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Influence of material type, thickness, and wavelength on transmittance of visible light through additively and subtractively manufactured permanent CAD-CAM resin materials for definitive restorations.

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Influence of material type, thickness, and wavelength on transmittance of visible light through additively and subtractively manufactured permanent CAD-CAM resin materials for definitive restorations.

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Content Influence of material type, thickness, and wavelength on transmittance of visible light
through additively and subtractively manufactured permanent CAD-CAM resin materials for
definitive restorations.
By
Alberto Lázaro Pascual, DDS
A Thesis Presented to the
FACULTY OF THE USC HERMAN OSTROW SCHOOL OF DENTISTRY
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(BIOMATERIALS AND DIGITAL DENTISTRY)
May 2024
Copyright 2024 Alberto Lázaro Pascual

ii
Dedication
To my parents, Dr. Ricardo Lázaro Valero and Ms. Cristina Pascual, for their unconditional
support, love, and their gift of life. To my brother, Dr. Ricardo Lázaro Pascual, source of
inspiration, bravery and passion in my personal and professional career. To have you as my
brother is indeed a blessing. To everyone who has inspired me to excel in my life. I have an
everlasting debt of gratitude to all of you.

iii
Acknowledgements
First and foremost, I owe my deepest appreciation to my parents, for always believing in me,
supporting me to fulfil my dreams and encouraging me to become better in whatever I aim to
be. I am where I am today because of them. I could not have done any of this without their love
and support.
I would like to thank my brother for all the love, support, encouragement, and inspiration
through good and hard times.
I would like to express my appreciation to my supervisor Dr. Jin-Ho Phark, for all the help and
support provided during the Master degree and for the time you invested in me. Your extensive
knowledge and direction were vital in helping me complete my thesis.
To my co-advisor, Dr. Sillas Duarte, my deep gratitude for the opportunity to pursue this
Master of Science and contributing to advancing my education, in digital and restorative
dentistry and for your guidance throughout the course of the Master.
I would also like to thank Dr. Alena Knezevic, for your guidance and support during the
master’s program, and for your advice and constant updates with the current literature.
I would like to express my full and special gratitude to my faculty members in Advanced
Prosthodontics throughout these past two years and a half. My sincerest gratitude to Dr.
Winston Chee and Dr. George Cho, for the opportunity to become part of the Advanced
Prosthodontics family and combine the program with the Master of Science in Biomaterials
and Digital Dentistry. To my program director, Dr. Cheryl Park, for her inspiration, guidance,
encouragement, and support to complete both programs simultaneously in an excellent manner.
Also, I would like to thank Dr. Tae J Ahn and Dr. Sangho Byun, I sincerely appreciate your
helpful instruction, the engaging intellectual discussions and lessons learnt from you during
the extensive hours in clinic. I am grateful for all your efforts and insights to make my learning
experience meaningful. Thank you all for advancing my education in Prosthodontics, clinically
and theoretically, and for your guidance, not only in the professional aspect, but on the personal
side too.

iv
I would also want to express my gratitude to my research colleagues, Dr. Jordi Llena, Dr.
Andrew Lim and Dr. Waad Mzain, for your continuous supportive words as we work through
this journey together.
Finally, I would like to express my gratefulness and appreciation to the Advanced
Prosthodontics residents, Class of 2022, 2023, 2025 and 2026, we have shared part of our
training to become Prosthodontists, you’ll always be part of me and you will have a place in
my heart.
Last, but not least, my deep appreciation and love to my co-residents Dr. Webster Felix, Dr.
Michael Ho, Dr. Hyojun Kim, Dr. Andrew Lim and Dr. Ankur Tyagi, with whom I have shared
the best, but also most intense and demanding, years of my life. I am grateful to life for having
crossed our path. Your support, drive and friendship has been unsurpassed. Thank you for being
my family in Los Angeles, this friendship will last forever.

v
Table of Contents
Dedication..................................................................................................................................................................................ii
Acknowledgements...................................................................................................................................................................iii
List of Tables..........................................................................................................................................................................viii
List of Figures...........................................................................................................................................................................ix
Abstract....................................................................................................................................................................................xii
Chapter One: Introduction ......................................................................................................................................................... 1
1. Computer-Aided Design and Manufacturing (CAD-CAM).......................................................................................1
1.1 Subtractive Manufacturing .............................................................................................................................. 2
1.2 Additive Manufacturing .................................................................................................................................. 5
2. Milled & Printed Materials...................................................................................................................................... 10
3. Polymerization ......................................................................................................................................................... 15
3.1 Free radical methacrylate polymerization...................................................................................................... 16
3.2 Creation of radicals........................................................................................................................................ 17
3.3 Initiation of the polymerization process ........................................................................................................ 18
3.4 Chain propagation ......................................................................................................................................... 18
3.5 Termination ................................................................................................................................................... 19
3.6 Degree of conversion..................................................................................................................................... 20
4. Photoinitiators.......................................................................................................................................................... 23
4.1 Camphoroquinone (CQ)................................................................................................................................ 24
4.2 9,10-Phenanthrenequinone (PQ).................................................................................................................... 25
4.3 1-Phenyl-1,2Propanedione (PPD).................................................................................................................. 27
4.4 Ivocerin ......................................................................................................................................................... 28
4.5 Lucirin TPO................................................................................................................................................... 29
5. Light Curing Units (LCUs)...................................................................................................................................... 31
5.1 Halogen light curing units (QTH LCUs)....................................................................................................... 32
5.2 LED Light curing units (LED LCUs)............................................................................................................ 33
5.3 Plasma Arc LCU’s (PALs)............................................................................................................................ 34
5.4 Laser lights (LLs).......................................................................................................................................... 34
5.5 Polymerization of composite resins and adhesives........................................................................................ 35
6. Spectrophotometers and transmittance of light ........................................................................................................ 37
6.1 Basics of light behavior and interaction ........................................................................................................ 37
6.2 Transmittance Spectrophotometers................................................................................................................ 39
6.3 Reflectance Spectrophotometers ................................................................................................................... 42
7. Importance of light transmittance in dentistry.......................................................................................................... 44
Chapter Two: Hypothesis & Objectives .................................................................................................................................. 47
1. Question/s: ............................................................................................................................................................... 47
2. Null hypothesis: ....................................................................................................................................................... 47
3. Objective/s:.............................................................................................................................................................. 47
Chapter Three: Materials and Methods.................................................................................................................................... 48
1. Milled material (control) – Lava Ultimate (3M, St. Paul, MN, USA) - (Group A).................................................51
2. Printed material 1 - VarseoSmile Crown Plus (BEGO, Bremen, Germany) - (Group B)........................................53
3. Printed material 2 - Ceramic Crown (Sprintray, Los Angeles, CA, USA) – (Group C)...........................................54
4. Design, printing and slicing for groups B and C:..................................................................................................... 55
5. Post-processing for groups B and C:........................................................................................................................ 65
6. Support removal (groups B and C): ......................................................................................................................... 68
7. Polishing & Sample Identification (for all groups):................................................................................................. 68
8. Testing (Transmittance Analysis): ........................................................................................................................... 76
9. Data Management and Statistical Analysis:............................................................................................................. 82

vi
Chapter Four: Results.............................................................................................................................................................. 83
1. Descriptive Analysis of Transmittance %:............................................................................................................... 83
2. Data Normality Analysis and Equality of Variances: .............................................................................................. 86
3. Statistical analysis and comparisons between materials:.......................................................................................... 88
3.1 Material comparisons (by wavelength) – thickness = 1 mm..........................................................................90
3.1.1 Camphorquinone (CQ) [468nm] .............................................................................................................. 90
3.1.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................... 91
3.1.3 Ivocerin [418nm]...................................................................................................................................... 92
3.1.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]............................................................................................ 93
3.1.5 Lucirin TPO [400nm]............................................................................................................................... 94
3.1.6 Summary .................................................................................................................................................. 95
3.2 Material comparisons (by wavelength) – thickness = 2 mm..........................................................................96
3.2.1 Camphorquinone (CQ) [468 nm] ............................................................................................................. 96
3.2.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................... 97
3.2.3 Ivocerin [418nm]...................................................................................................................................... 98
3.2.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]............................................................................................ 99
3.2.5 Lucirin TPO [400nm]............................................................................................................................. 100
3.2.6 Summary ................................................................................................................................................ 101
3.3 Material comparisons (by wavelength) – thickness = 3mm.........................................................................102
3.3.1 Camphorquinone (CQ) [468 nm] ........................................................................................................... 102
3.3.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................. 103
3.3.3 Ivocerin [418nm].................................................................................................................................... 104
3.3.4 1-Phenyl-1,2 propanedione (PPD) [410 nm].......................................................................................... 105
3.3.5 Lucirin TPO [400 nm]............................................................................................................................ 106
3.3.6 Summary ................................................................................................................................................ 107
3.4 Material comparisons (by wavelength) – thickness = 4mm.........................................................................108
3.4.1 Camphorquinone (CQ) [468 nm] ........................................................................................................... 108
3.4.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................. 109
3.4.3 Ivocerin [418nm].................................................................................................................................... 110
3.4.4 1-Phenyl-1,2 propanedione (PPD) [410 nm].......................................................................................... 111
3.4.5 Lucirin TPO [400nm]............................................................................................................................. 112
3.4.6 Summary ................................................................................................................................................ 113
4. Statistical analysis and comparisons between thicknesses:....................................................................................114
4.1 Thickness comparisons (by wavelength) – Lava Ultimate: .........................................................................116
4.1.1 Camphorquinone (CQ) [468 nm] ........................................................................................................... 116
4.1.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................. 117
4.1.3 Ivocerin [418 nm]................................................................................................................................... 118
4.1.4 1-Phenyl-1,2 propanedione (PPD) [410 nm].......................................................................................... 119
4.1.5 Lucirin TPO [400 nm]............................................................................................................................ 120
4.1.6 Summary ................................................................................................................................................ 121
4.2 Thickness comparisons (by wavelength) – Varseo Smile: ..........................................................................122
4.2.1 Camphorquinone (CQ) [468 nm] ........................................................................................................... 122
4.2.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................. 123
4.2.3 Ivocerin [418 nm]................................................................................................................................... 124
4.2.4 1-Phenyl-1,2 propanedione (PPD) [410 nm].......................................................................................... 125
4.2.5 Lucirin TPO [400 nm]............................................................................................................................ 126
4.2.6 Summary ................................................................................................................................................ 127
4.3 Thickness comparisons (by wavelength) – Ceramic Crown:.......................................................................128
4.3.1 Camphorquinone (CQ) [468 nm] ........................................................................................................... 128
4.3.2 9,10-Phenanthrenequinone (PQ) [420 nm]............................................................................................. 129
4.3.3 Ivocerin [418 nm]................................................................................................................................... 130
4.3.4 1-Phenyl-1,2 propanedione (PPD) [410 nm].......................................................................................... 131
4.3.5 Lucirin TPO [400 nm]............................................................................................................................ 132
4.3.6 Summary ................................................................................................................................................ 133
5. Statistical analysis and comparisons between photoinitiators:...............................................................................134
5.1 Photoinitiator (wavelength) comparison (by material) – thickness = 1 mm ................................................136
5.1.1 Lava Ultimate......................................................................................................................................... 136
5.1.2 Varseo Smile .......................................................................................................................................... 137
5.1.3 Ceramic Crown ...................................................................................................................................... 138
5.1.4 Summary ................................................................................................................................................ 139
5.2 Photoinitiator (wavelength) comparison (by material) – thickness = 2 mm ................................................140
5.2.1 Lava Ultimate......................................................................................................................................... 140
5.2.2 Varseo Smile .......................................................................................................................................... 141
5.2.3 Ceramic Crown ...................................................................................................................................... 142

vii
5.2.4 Summary ................................................................................................................................................ 143
5.3 Photoinitiator (wavelength) comparison (by material) – thickness = 3 mm ................................................144
5.3.1 Lava Ultimate......................................................................................................................................... 144
5.3.2 Varseo Smile .......................................................................................................................................... 145
5.3.3 Ceramic Crown ...................................................................................................................................... 146
5.3.4 Summary ................................................................................................................................................ 147
5.4 Photoinitiator (wavelength) comparison (by material ) – thickness = 4 mm ...............................................148
5.4.1 Lava Ultimate......................................................................................................................................... 148
5.4.2 Varseo Smile .......................................................................................................................................... 149
5.4.3 Ceramic Crown ...................................................................................................................................... 150
5.4.4 Summary ................................................................................................................................................ 151
Chapter Five: Discussion ....................................................................................................................................................... 152
1. Transmittance of light related to material .............................................................................................................. 154
2. Transmittance of light in function of material thickness........................................................................................ 156
3. Translucency related to wavelength....................................................................................................................... 158
4. Light transmittance, translucency and esthetics..................................................................................................... 160
5. Degree of conversion ............................................................................................................................................. 163
5.1 Material microstructure: .............................................................................................................................. 163
5.2 Thickness:.................................................................................................................................................... 164
5.3 Type of cement:........................................................................................................................................... 165
5.4 Light curing units parameters and wavelengths:.......................................................................................... 166
6. Future Perspectives................................................................................................................................................ 166
7. Limitations............................................................................................................................................................. 167
Chapter Six: Conclusions....................................................................................................................................................... 171
Bibliography .......................................................................................................................................................................... 172

viii
List of Tables
Table 1: Comparison of digital manufacturing techniques ........................................................................................................9
Table 2. Materials used in the study (2, 10, 58, 65)......................................................................................................................... 48
Table 3. Identification and measurements for each sample...................................................................................................... 75
Table 4. Descriptive statistical analysis of results.................................................................................................................... 84
Table 5. Kolmogorov-Smirnov test for non-transformed data ................................................................................................. 86
Table 6. Kolmogorov-Smirnov test for transformed data ........................................................................................................ 86
Table 7. Levene's test (equality of variances) .......................................................................................................................... 87
Table 8. Group-wise comparisons of materials tested at 1 mm for CQ (468nm ......................................................................90
Table 9. Group-wise comparisons of materials tested at 1mm for PQ (420 nm) .....................................................................91
Table 10. Group-wise comparisons of materials tested at 1mm for Ivocerin (418 nm) ...........................................................92
Table 11. Group-wise comparisons of materials tested at 1mm for PPD (410 nm) .................................................................93
Table 12. Group-wise comparisons of materials tested at 1mm for Lucirin TPO (400nm) .....................................................94
Table 13. Group-wise comparisons of materials tested at 2 mm for CQ (468nm)...................................................................96
Table 14. Group-wise comparisons of materials tested at 2 mm for PQ (420 nm) ..................................................................97
Table 15. Group-wise comparisons of materials tested at 2 mm for Ivocerin (418 nm) ..........................................................98
Table 16. Group-wise comparisons of materials tested at 2 mm for PPD (410 nm) ................................................................99
Table 17. Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm) ..................................................100
Table 18. Group-wise comparisons of materials tested at 3 mm for CQ (468nm).................................................................102
Table 19. Group-wise comparisons of materials tested at 3 mm for PQ (420 nm) ................................................................103
Table 20. Group-wise comparisons of materials tested at 3 mm for Ivocerin (418 nm) ........................................................104
Table 21. Group-wise comparisons of materials tested at 3 mm for PPD (410 nm) ..............................................................105
Table 22. Group-wise comparisons of materials tested at 3 mm for Lucirin TPO (400 nm) .................................................106
Table 23. Group-wise comparisons of materials tested at 4 mm for CQ (468nm).................................................................108
Table 24. Group-wise comparisons of materials tested at 4 mm for PQ (420 nm) ................................................................109
Table 25. Group-wise comparisons of materials tested at 4 mm for Ivocerin (418 nm) ........................................................110
Table 26. Group-wise comparisons of materials tested at 4 mm for PPD (410 nm) ..............................................................111
Table 27. Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm) ..................................................112
Table 28. Group-wise comparisons of thicknesses at Lava Ultimate group for CQ (468nm)................................................116
Table 29. Group-wise comparisons of thicknesses at Lava Ultimate group for PQ (420nm) ................................................117
Table 30. Group-wise comparisons of thicknesses at Lava Ultimate group for Ivocerin (418 nm) .......................................118
Table 31. Group-wise comparisons of thicknesses at Lava Ultimate group for PPD (410 nm).............................................119
Table 32. Group-wise comparisons of thicknesses at Lava Ultimate group for Lucirin TPO (400 nm) ................................120
Table 33. Group-wise comparisons of thicknesses at Varseo Smile group for CQ (468nm).................................................122
Table 34. Group-wise comparisons of thicknesses at Varseo Smile group for PQ (420nm)..................................................123
Table 35. Group-wise comparisons of thicknesses at Varseo Smile group for Ivocerin (418 nm).........................................124
Table 36. Group-wise comparisons of thicknesses at Varseo Smile group for PPD (410 nm) ..............................................125
Table 37. Group-wise comparisons of thicknesses at Varseo Smile group for Lucirin TPO (400 nm)..................................126
Table 38. Group-wise comparisons of thicknesses at Ceramic Crown group for CQ (468nm) .............................................128
Table 39. Group-wise comparisons of thicknesses at Ceramic Crown group for PQ (420nm)..............................................129
Table 40. Group-wise comparisons of thicknesses at Ceramic Crown group for Ivocerin (418 nm).....................................130
Table 41. Group-wise comparisons of thicknesses at Ceramic Crown group for PPD (410 nm)...........................................131
Table 42. Group-wise comparisons of thicknesses at Ceramic Crown group for Lucirin TPO (400 nm)..............................132
Table 43. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 1 mm ..............................................136
Table 44. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 1 mm ...............................................137
Table 45. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 1 mm............................................138
Table 46. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 2 mm ..............................................140
Table 47. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 2 mm. ..............................................141
Table 48. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 2 mm............................................142
Table 49. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 3 mm. .............................................144
Table 50. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 3 mm ...............................................145
Table 51. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 3 mm............................................146
Table 52. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 4 mm ..............................................148
Table 53. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 4 mm ...............................................149
Table 54. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 4 mm............................................150

ix
List of Figures
Figure 1. Chemical structure of a methacrylate-based monomer.....................................................................................................................16
Figure 2. Schematic illustration of external energy factors acting on a radical-generating species to result in formation of “free radicals”. ..17
Figure 3. Diagram of the polymerization initiation step. .................................................................................................................................18
Figure 4. Polymer chain propagation by addition of successive monomer units..............................................................................................18
Figure 5. Diagram of chain termination via monomer-radical collision. .........................................................................................................19
Figure 6. Visible light absorption spectrum of CQ, ranging from about 425 to 495 nm..................................................................................24
Figure 7. Visible light absorption of the photoinitiator, 9,10-Phenanthrnequinone, spanning from about 390 to 460 nm. ..............................25
Figure 8. Visible light absorption of PPD, ranging between 390 to 460 nm....................................................................................................27
Figure 9. Visible light absorption of Ivocerin® is seen to span from about 390 to 445 nm.............................................................................28
Figure 10. Visible light absorption of the photoinitiator, Lucirin® TPO, spanning from about 390 to 410 nm...............................................29
Figure 11. Reflection (left) and transmission (right)........................................................................................................................................37
Figure 12. Top: direct, mixed and diffuse reflection. Bottom: direct, mixed and diffused transmission..........................................................37
Figure 13. Spectrophotometer mechanism (diagram)......................................................................................................................................40
Figure 14. Summariez diagram regarding materials, groups and subgroups....................................................................................................49
Figure 15. Summarized workflow and steps taken ..........................................................................................................................................50
Figure 16. Machine used for cutting the specimens.........................................................................................................................................51
Figure 17. Lava Ultimate block used...............................................................................................................................................................51
Figure 18. 1 mm to 4 mm Lava Ultimate polished samples.............................................................................................................................52
Figure 19. Varseo Smile Crown Plus bottle used ............................................................................................................................................53
Figure 20. 1 mm to 4 mm Varseo Smile Crown Plus polished samples...........................................................................................................53
Figure 21. Ceramic Crown bottle used ............................................................................................................................................................54
Figure 22. 1 mm to 4 mm polished Ceramic Crown samples..........................................................................................................................54
Figure 23. Specimens design (1 mm to 4 mm)................................................................................................................................................55
Figure 24. Sprintray Pro S printer and Sprintray Pro Wash/Dry equipment ....................................................................................................56
Figure 25. Sprintray Pro S printer ready to use................................................................................................................................................56
Figure 26. Varseo Smile Crown Plus 1 mm specimen distribution on printer tray (front view) ......................................................................57
Figure 27. Varseo Smile Crown Plus 1 mm specimen distribution on printer tray (side view)........................................................................57
Figure 28. Varseo Smile Crown Plus 2 mm specimen distribution on printer tray (front view) ......................................................................58
Figure 29. Varseo Smile Crown Plus 2 mm specimen distribution on printer tray (side view)........................................................................58
Figure 30. Varseo Smile Crown Plus 3 mm specimen distribution on printer tray (front view) ......................................................................59
Figure 31. Varseo Smile Crown Plus 3 mm specimen distribution on printer tray (side view)........................................................................59
Figure 32. Varseo Smile Crown Plus 4 mm specimen distribution on printer tray (front view) ......................................................................60
Figure 33. Varseo Smile Crown Plus 4 mm specimen distribution on printer tray (side view)........................................................................60
Figure 34. Ceramic Crown 1 mm specimen distribution on printer tray (front view)......................................................................................61
Figure 35. Ceramic Crown 1 mm specimen distribution on printer tray (side view) .......................................................................................61
Figure 36. Ceramic Crown 2 mm specimen distribution on printer tray (front view)......................................................................................62
Figure 37. Ceramic Crown 2 mm specimen distribution on printer tray (side view) .......................................................................................62
Figure 38. Ceramic Crown 3 mm specimen distribution on printer tray (front view)......................................................................................63
Figure 39. Ceramic Crown 3 mm specimen distribution on printer tray (side view) .......................................................................................63
Figure 40. Ceramic Crown 4 mm specimen distribution on printer tray (front view)......................................................................................64
Figure 41. Ceramic Crown 4 mm specimen distribution on printer tray (side view) .......................................................................................64
Figure 42. Sprintray Pro Wash/Dry equipment ...............................................................................................................................................65
Figure 43. Sprintray Print Removal Tool ........................................................................................................................................................65
Figure 44. Printed Varseo Smile Crown Plus 1 mm - 4 mm samples before post-processing (front view).....................................................66
Figure 45. Printed Varseo Smile Crown Plus 1 mm - 4 mm samples before post-processing (side view)......................................................67
Figure 46. Printed Ceramic Crown 1 mm - 4 mm samples before post-processing (front view) .....................................................................67
Figure 47. Printed Ceramic Crown 1 mm - 4 mm samples before post-processing (side view)......................................................................67
Figure 48. Sprintray Support Snipper..............................................................................................................................................................68
Figure 49. Buehler 600-grit, 1000-grit and 1200-grit polishing sandpaper......................................................................................................68
Figure 50. 1 mm to 4 mm samples being measured during calibration process...............................................................................................70
Figure 51. Labelled containers with samples (sample number, material, thickness and size)..........................................................................71
Figure 52. Set up used: computer to register data and PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer.........................................76
Figure 53. PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer used....................................................................................................76
Figure 54. PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer used (open) ........................................................................................77
Figure 55. Diagram indicating. most important parts of spectrophotometer PerkinElmer Lambda 950 UV-Vis-Nir.......................................77
Figure 56. Integrating sphere for spectrophotometer Lambda 950 UV-Vis-Nir (top view)- left image ...........................................................78
Figure 57. Integrating sphere for spectrophotometer Lambda 950 UV-Vis-Nir (side view)- right image........................................................78
Figure 58. Solid sample holder & sample positioning for spectrophotometer Lambda 950 UV-Vis-Nir (top view)- left image .....................78
Figure 59. Solid sample holder & sample positioning for spectrophotometer Lambda 950 UV-Vis-Nir (side view)- right image..................78
Figure 60. Solid sample holder with no sample (front and side views)............................................................................................................79
Figure 61. Solid sample holder holding sample (front and side views) ...........................................................................................................79
Figure 62. Screenshot of parameters introduced at UV Winlab software ........................................................................................................81
Figure 63. Transmittance of light for all materials, thickness and photoinitiators (wavelengths......................................................................85
Figure 64. Transmittance of light by materials, at all thicknesses and wavelengths........................................................................................88
Figure 65. Transmittance of light by materials and thicknesses (all wavelengths) ..........................................................................................89
Figure 66. Transmittance of light by materials and wavelengths (all thicknesses) ..........................................................................................89
Figure 67. (left) Kruskal-Wallis test boxplot of materials tested at 1 mm for CQ (468 nm)...........................................................................90
Figure 68. (right) Group-wise comparisons of materials tested at 1 mm for CQ (468 nm)..............................................................................90
Figure 69. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for PQ (420 nm) .............................................................................91
Figure 70. (right) Group-wise comparisons of materials tested at 1mm for PQ (420 nm)...............................................................................91
Figure 71. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for Ivocerin (418 nm) .....................................................................92
Figure 72. (right) Group-wise comparisons of materials tested at 1mm for Ivocerin (418 nm).......................................................................92

x
Figure 73. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for PPD (410 nm)...........................................................................93
Figure 74. (right) Group-wise comparisons of materials tested at 1mm for PPD (410 nm).............................................................................93
Figure 75. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for Lucirin TPO (400nm) ...............................................................94
Figure 76. (right) Group-wise comparisons of materials tested at 1mm for Lucirin TPO (400nm) .................................................................94
Figure 77. (left) Kruskal-Wallis test boxplot of materials tested at 2mm for Lucirin TPO (400nm) ...............................................................96
Figure 78. (right) Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm) ................................................................96
Figure 79. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for PQ (420 nm) ............................................................................97
Figure 80. (right) Group-wise comparisons of materials tested at 2 mm for PQ (420 nm)..............................................................................97
Figure 81. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for Ivocerin (418 nm) ....................................................................98
Figure 82. (right) Group-wise comparisons of materials tested at 2 mm for Ivocerin (418 nm)......................................................................98
Figure 83. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for PPD (410 nm)..........................................................................99
Figure 84. (right) Group-wise comparisons of materials tested at 2 mm for PPD (410 nm)............................................................................99
Figure 85. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for Lucirin TPO (400nm) ............................................................100
Figure 86. (right) Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm) ..............................................................100
Figure 87. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for CQ (468nm)...........................................................................102
Figure 88. (right) Group-wise comparisons of materials tested at 3 mm for CQ (468 nm)............................................................................102
Figure 89. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for PQ (420 nm) ..........................................................................103
Figure 90. (right) Group-wise comparisons of materials tested at 3 mm for PQ (420 nm)............................................................................103
Figure 91. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for Ivocerin (418 nm) ..................................................................104
Figure 92. (right) Group-wise comparisons of materials tested at 3 mm for Ivocerin (418 nm)....................................................................104
Figure 93. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for PPD (410 nm)........................................................................105
Figure 94. (right) Group-wise comparisons of materials tested at 3 mm for PPD (410 nm)..........................................................................105
Figure 95. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for Lucirin TPO (400nm) ............................................................106
Figure 96. (right) Group-wise comparisons of materials tested at 3 mm for Lucirin TPO (400nm) ..............................................................106
Figure 97.(left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Lucirin TPO (400nm) ............................................................108
Figure 98. (right) Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm) ..............................................................108
Figure 99. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for PQ (420 nm) ..........................................................................109
Figure 100. (right) Group-wise comparisons of materials tested at 4 mm for PQ (420 nm) ..........................................................................109
Figure 101. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Ivocerin (418 nm) ................................................................110
Figure 102. (right) Group-wise comparisons of materials tested at 4 mm for Ivocerin (418 nm)..................................................................110
Figure 103. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for PPD (410 nm)......................................................................111
Figure 104. (right) Group-wise comparisons of materials tested at 4 mm for PPD (410 nm)........................................................................111
Figure 105. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Lucirin TPO (400nm) ..........................................................112
Figure 106. (right) Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm) ............................................................112
Figure 107. Transmittance of light by thicknesses, at all materials and wavelengths....................................................................................114
Figure 108. Transmittance of light by thicknesses and materials (all wavelengths) ......................................................................................115
Figure 109. Transmittance of light by thickness and wavelength (all materials) ...........................................................................................115
Figure 110. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for CQ (468nm)........................................................116
Figure 111. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for CQ (468nm)..........................................................116
Figure 112. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for PQ (420nm) ........................................................117
Figure 113. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for PQ (420nm) ..........................................................117
Figure 114. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for Ivocerin (418 nm) ...............................................118
Figure 115. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for Ivocerin (418 nm).................................................118
Figure 116. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for PPD (410 nm) .....................................................119
Figure 117. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for PPD (410 nm).......................................................119
Figure 118.(left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for Lucirin TPO (400 nm).........................................120
Figure 119. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for CQ (468nm)..........................................................120
Figure 120. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for CQ (468nm) .........................................................122
Figure 121. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for CQ (468nm)...........................................................122
Figure 122. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for PQ (420nm)..........................................................123
Figure 123. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for PQ (420nm)............................................................123
Figure 124.(left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for Ivocerin (418 nm)..................................................124
Figure 125. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for Ivocerin (418 nm)...................................................124
Figure 126. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for PPD (410 nm).......................................................125
Figure 127. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for PPD (410 nm) ........................................................125
Figure 128.(left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for Lucirin TPO (400 nm)...........................................126
Figure 129.(right) Group-wise comparisons of thicknesses tested at Varseo Smile for CQ (468nm)............................................................126
Figure 130. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for CQ (468nm)......................................................128
Figure 131. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for CQ (468nm) .......................................................128
Figure 132. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for PQ (420nm)......................................................129
Figure 133. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for PQ (420nm)........................................................129
Figure 134. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for Ivocerin (418 nm).............................................130
Figure 135. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for Ivocerin (418 nm)...............................................130
Figure 136. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for PPD (410 nm)...................................................131
Figure 137. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for PPD (410 nm).....................................................131
Figure 138. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for Lucirin TPO (400 nm)......................................132
Figure 139. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for CQ (468nm) .......................................................132
Figure 140. Transmittance of light by wavelength, at all materials and thicknesses......................................................................................134
Figure 141. Transmittance of light by photoinitiator (wavelength) and materials (all thicknesses)...............................................................135
Figure 142. Transmittance of light by photoinitiator (wavelength) and thickness (all materials) ..................................................................135
Figure 143. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 1 mm ......................................................136
Figure 144. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 1 mm........................................................136
Figure 145. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 1 mm........................................................137
Figure 146. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 1 mm .........................................................137
Figure 147. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 1 mm....................................................138

xi
Figure 148. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 1 mm......................................................138
Figure 149. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 2 mm ......................................................140
Figure 150. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 2 mm........................................................140
Figure 151. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 2 mm........................................................141
Figure 152. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 2 mm .........................................................141
Figure 153. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 2 mm....................................................142
Figure 154. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 2 mm......................................................142
Figure 155. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 3 mm ......................................................144
Figure 156. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 3 mm........................................................144
Figure 157. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 3 mm........................................................145
Figure 158. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 3 mm .........................................................145
Figure 159. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 3 mm....................................................146
Figure 160. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 3 mm......................................................146
Figure 161. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 4 mm ......................................................148
Figure 162. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 4 mm........................................................148
Figure 163. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 4 mm........................................................149
Figure 164. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 4 mm .........................................................149
Figure 165. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 4 mm....................................................150
Figure 166. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 4 mm......................................................150

xii
Abstract
Purpose: To evaluate the transmittance of light through CAD CAM resin materials for
definitive restorations that were manufactured additively (printed) or subtractively (milled) as
a function of material, thickness, and wavelength.
Material and methods: A total of 120 flat, squared samples were fabricated from three
different CAD CAM resin materials for definitive restorations (milled: Lava Ultimate (3M,
St. Paul, MN, USA); printed: Varseo Smile Crown Plus (BEGO, Bremen, Germany) and
(Ceramic Crown Sprintray, Los Angeles, CA, USA)). For each material, specimens of
different thicknesses (1 mm , 2 mm, 3 mm and 4 mm with n=10 per thickness) were
fabricated and polished. Transmittance of light at different wavelengths (400 nm, 410 nm,
418 nm, 420 nm, 468 nm) was measured using a spectrophotometer equipped with a 150 mm
integrating sphere (Perkin Elmer, Waltham, MA, USA). Data was analyzed using KruskalWallis and Mann-Whitney tests with Bonferroni correction (α=.05).
Results: The transmittance of light was higher for Lava Ultimate, followed by Varseo Smile
Crown Plus and Ceramic Crown. Significant differences were observed between the
thicknesses tested: 1 mm thickness transmitted the highest amount of light while 4 mm
thickness transmitted the lowest. The higher transmittance values were achieved when longer
wavelengths were used: irradiant light at 468 nm transmitted the most, while irradiant light at
400 nm transmitted the least.
Conclusions: Light transmittance can be affected by the material used, the thickness of the
object, and the wavelength of the light. Light transmittance through permanent CAD/CAM
resin materials was reduced for printed materials, increasing thickness, and lower
wavelengths.

Chapter One: Introduction
1. Computer-Aided Design and Manufacturing (CAD-CAM)
The development of CAD/CAM is based around three elements, namely: (1) data acquisition,
(2) data processing and (3) manufacturing. The exponential increase in power of computers
has resulted in major advances in all of these areas.(1-3)
During the last years, there has been a huge increase in the use of computer-aided design
(CAD) and computer-aided manufacturing (CAM) in dentistry, basically due to advances in
intraoral and extraoral scanning and manufacturing technologies. The fact that CAD/CAM
technologies provide the possibility of manufacturing a wide range of biomaterials, such as
zirconia, ceramic-infiltrated polymers, ceramics, PMMA or even metals, has made
CAD/CAM technology an indispensable part of any dental laboratory or office.
(1-3)
The increased demand for esthetics in dentistry has led to an increase in the use of ceramic
and tooth-colored composite resin restorations.(4) Especially, the CAD/CAM ceramics have
enjoyed growing popularity.(5, 6) Because more dentists work independently of a technician,
they need to get a better understanding of the optical characteristics of dental materials in
order to closely match them with those of the natural tooth.(7-9)
When talking about CAD/CAM technologies, there are two main manufacturing
technologies: subtractive manufacturing and additive manufacturing. Subtractive
manufacturing (mostly known as milling) was first introduced in dentistry and has been able
to produce high-precision level restorations and products with high precision and details on
the occlusal surface as well as high accuracy of the marginal and internal fit.(10)
Recently, additive manufacturing technologies, more commonly known as 3D printing, have
been receiving increasing attention among practitioners and dental technicians. There has
been a vast development of printable biomaterials, particularly for the fabrication of resin and
ceramic restorations. (11)

2
1.1 Subtractive Manufacturing
If we look at where we are today, CAD/CAM in dentistry has been primarily based around
the process of subtractive manufacturing. Milling begins with a block of material and a
milling machine controlled by a computer. The milling machine then executes commands for
removing material that is not wanted in the final product. This method is also known as
“subtractive manufacturing.”(12) It has been shown that subtractive manufacturing reduces
overall production time and yields complex products that would have otherwise been difficult
to create through conventional dental processes. (12)
Over the years, CAM processes have achieved a significantly high degree of sophistication
and complexity in terms of the products that can be manufactured,(12) and today a vast variety
of tool path schematics and materials can be used. It has been demonstrated that by using this
method the overall production time will reduce considerably and complex models, which are
otherwise difficult and/or impossible to make by the conventional dental processes, could be
made easily. Nowadays all these processing routes come under the umbrella of subtractive
machining.(6, 7) However, this method of manufacturing is very wasteful as more material is
removed compared to what is used in the final product.(8)
In subtractive manufacturing, objects are created by progressively removing material from a
solid block or sheet. The material is removed from the starting material by cutting, drilling,
boring, or grinding. While these processes may be carried out manually, they are more
commonly achieved using computer numeric control (CNC); consequently, being today, the
most popular subtractive manufacturing. (8)
CNC machining involves the use of CAD to design a model to be machined, as well as the
use of CAM to instruct the CNC machine on how exactly to do the material removal. There
are three major machining processes that concern removing material according to 3D models:
turning, drilling and milling. Other subtractive manufacturing processes are laser cutting,
waterjet cutting, electrical discharge machining, and plasma cutting. These methods are
mainly used for 2D machining. (8)

3
The main advantages of subtractive manufacturing are: (8)
- Application to a wide variety of materials including metals, plastics, plastic
composites and even wood.
- Possibility of use to obtain almost any geometry such as flat surface, holes, cylinders,
screw threads, slots etc.
- High accuracy and precision with low tolerance values.
- Ability to obtain smooth surface finishing.
However, subtractive manufacturing techniques also have limitations, such as the amount of
material wastage, in form of chips of material that are no table to be used. Even if the chips
can be recycled, they are still wasted material. Moreover, subtractive manufacturing
techniques are more time consuming than additive manufacturing methods. (8)
Additionally, not all milling machines are alike: there are multiple milling options available
for different applications within the dental profession. The simplest of all CNC milling
apparatuses is the 3-axis milling machine, in which the machine’s tool schematic
simultaneously controls bur movement along the X, Y, and Z planes.(13)This type of milling
machine is appropriate for most non-complex dental restorations or applications that do not
pose an occult surface. If milled components have a tool schematic that requires dramatic
curvatures, the 3-axis CNC apparatus could possibly mill with gouging and/or interference. It
may be necessary to sacrifice inert detail to prevent this from occurring, which would then
limit the precision of the milled product.(14)
A second option is a 4-axis CNC milling machine. This type of milling unit provides an
additional element of precision. The block table moves along a fourth plane, allowing the tool
path to reach more curvature and achieving enhanced detail in the final mill product. In order
to produce more complex restorations that require explicate inert details it is necessary to use
enhanced axes CNCs that are more sophisticated in their tool schematics.(14)
Also available are 5-axis milling machines, which are even more versatile because they
control their tool paths in five motions continuously and simultaneously. Two concurrent
motions within the milling machine occur—X-, Y-, and Z-axis movement and A-, B-axis

4
movement in either the cutter spindle or the block table.(13) The unique advantage to such a
tool path schematic is that continuous adjustment of the bur’s orientation while cutting
facilitates a significantly heightened precision in the milled product necessary for complex
cases such as implants. It is recommended that dental laboratories use discrete 5-axis CNC
milling machines, which are able to operate within both 3-axis and 5-axis schema depending
on the needs of the case.(15)

5
1.2 Additive Manufacturing
Additive manufacturing is defined by the American Society for Testing and Materials
(ASTM) as: “the process of joining materials to make objects from 3D model data, usually
layer upon layer, as opposed to subtractive manufacturing methodologies”.(16)
Three dimensional (3D) printing refers to the process that materials are mixed or solidified
together (such as liquid molecules or powder grains being fused together) to create a 3D
object under computerized control.(17) As one of the advanced fabrication techniques, 3D
printing is also referred to as additive manufacturing (AM) and rapid prototyping technology,
which requires automated processes and standardized materials as building blocks to enable
the creation of 3D objects from personalized and specific computer-aided designs.(18)
The first 3D printing process, called as “stereolithography”, was invented by Charles Hull in
1983. In 1986, Mr. Hull introduced the first three-dimensional (3D) printing technology, and
the industry developed many different manufacturing technologies, which have been applied
to numerous fields.(18-21) That year, Hull patented stereolithography (SLA) and built and
developed a 3D printing system. In 1990, Scott Crump received a patent for fused deposition
modeling (FDM).(22) Since then, 3D printing has been increasingly progressing.
Since then, many companies have developed 3D printers for commercial applications. With
the rapid development of 3D printing technologies, 3D printing gained much attention in
public due to its excellence in precision, extraordinary material savings, freedom in design,
and personalized customization.(23)
In the field of medicine, such as traumatology, cardiology, neurosurgery, plastic surgery, and
craniomaxillofacial surgery, 3D printing is often used for digital imaging in surgical
planning, custom surgical devices, and patient-physician communication.(24) In the field of
dentistry, its applications range from prosthodontics, oral and maxillofacial surgery, and oral
implantology to orthodontics, endodontics, and periodontology.(25, 26)
In principle the process works by taking a 3D computer file and creating a series of crosssectional slices. Each slice is then printed one on top of the other to create the 3D object. One
attractive feature of this process is that there is no waste. Traditionally, additive
manufacturing processes started to be used in the 1980s to manufacture prototypes, models,

6
and casting patterns. Thus, it has its origins in rapid prototyping (RP), which is the name
given to the rapid production of models using additive layer manufacturing. Today, “Additive
Manufacturing” describes technologies that can be used anywhere throughout the product life
cycle from pre-production (i.e. rapid prototyping) to full scale production (also known as
rapid manufacturing) and even for tooling applications or post-production customization.(10)
Additive manufacturing is widely known as 3D printing. It is carried out using machines
known as 3D printers. The term 3D printing covers a range of processes that differ by
material and energy source. However, there are common steps in all operations: (25, 26)
1. A CAD model of the part to be printed is designed.
2. Specialized slicing software then slices this model into several cross-sectional layers.
3. Depending on the technology used, the 3D printer proceeds to melt, fuse, or cure the
material and deposit it layer by layer until the desired geometry forms. The material
may be powder, wire, sheet, or liquid.
The main advantages of additive manufacturing are the following: (25, 26)
- It is highly efficient due to the elimination of waste.
- It is comparatively faster to go from the design stage to production.
- Produces intricate and complex designs with ease.
The main disadvantages of additive manufacturing follow: (25, 26)
- Less precision and accuracy than subtractive manufacturing.
- Reduced variety of materials available (mainly acrylics and resins).
- Limited mechanical properties and finishing processes always needed.
Additive manufacturing is transitioning from rapid prototyping models to manufacturing real
parts for use as final products. The equipment is becoming competitive with traditional
manufacturing techniques in terms of price, speed, reliability, and cost of use. This, in turn,
has led to the expansion of its use in industry and there has been explosive growth in the sales
and distribution of the equipment.(27)
Alongside these developments the number of materials that the industry uses have increased
greatly and modern machines can utilize a broad array of polymers, metals and ceramics. As

7
the industry makes the transition from prototypes to functional devices, the materials
available will begin to play a much bigger role. When producing a prototype it is enough for
it to look good, but as we move to functional objects such as customized implants and oral
prostheses the materials and their properties become much more important.(28)
3D printing was first applied in dentistry in the early 2000s, when the technology was first
used to make dental implants and custom prosthetics. The up- to-date medical applications of
3D printing can be briefly divided into the following categories: tissue and organ fabrication,
creating prosthetics, implants, and anatomical models, as well as pharmaceutical research
concerning drug discovery, delivery, and dosage forms. The greatest advantage that 3D
printing provides for medical applications is the freedom to produce custom-made medical
products and equipment. Therefore, the applications of 3D printing to customize prosthetics
and implants can create inestimable value.(23, 29, 30)
Additive manufacturing in dentistry has many benefits, mainly the fulfillment of the
customized requirements of dental industry in lesser time and cost. However, it also provides
faster and accurate service, it is cost-effective, fabrication is easy and quicker (reduced
fabrication time), production is rapid, design is customized and reduces physical storage (due
to digital storage).(27, 31-33)
The most frequently used method for this purpose is polymerization-based printing, a
technique where light of a specific wavelength is directed to a VAT containing a liquid
photosensitive resin, which is locally cured and solidified layer by layer to form the desired
object.(34)
The process of additive manufacturing is ideally suited to dentistry, which has a tradition of
producing customized parts made to fit the patient and not the other way around. This creates
a great opportunity for dentistry and there is already a huge array of additive manufacturing
technologies that we can use, and these include:
• Fused deposition modelling (FDM): product is manufactured as like the extrusion
process, where a heated thermoplastic material is added layer by layer to fabricate a
model. In this process, the print head consists of multi-nozzle and extrudes different
types of material at the same time.(35, 36)

8
• Selective laser sintering (SLS): this additive manufacturing technology accomplishes
sintering with the application of a laser beam. The material used is in the form of
powder, and laser sinters the powder.(37, 38)
• Direct metal laser sintering (DMLS): this technology is used to produce metal parts
with high accuracy and better mechanical strength. In this technology, the metal
material is added layer by layer and a laser beam is used to fuse powder at a definite
point.(39, 40)
• Electron Beam Melting (EBM): Powerful electron beam is used to build product layer
by layer using a metal powder by command of the CAD model with exact geometry.
Under a vacuum, the raw material is stored and fused by an electron beam.(41, 42)
• Stereolithography (SLA): products are built with the application of ultraviolet laser
inside a vat of resin. Limited availability of materials useable with this technology as
it uses light-sensitive polymers. It gives better surface finish and has lesser wastage of
raw material.(43, 44) Makes use of a scanning laser as light source for curing the liquid
polymer. A wide variety of SLA printers have now become commercially available
and their use in dental laboratories is constantly increasing.(45)
• Digital Light Processing (DLP): is similar to SLA, but uses a shallower VAT and
cures an entire layer by means of a digital light projector located beneath the resin
bath.(27) DLP therefore leads to faster print times and requires less material than SLA.
However, post-processing steps, such as washing off excess resin and further light
curing, are still necessary for ensuring good mechanical properties. (46)
• Polyjet 3D printing (PJP): manufacturing of parts through UV-curable acrylic plastic.
It uses various types of printing materials. In medical and dentistry field, model
printed by this technology provides a better understanding of patient anatomy.(47, 48)
• Inkjet 3D printing (IJP): This technology use different fluids such as polymer solution
provided in the form of liquid and deposited layer by layer to built a product. It prints
varieties of materials with less time and cost.(49, 50)
• Laminated Object Manufacturing (LOM): 3D models are fabricated by adding layers
of the defined sheet of materials. A laser is used to cut sheet material as per the
required cross-section. Adhesives are used to combine the layers and generated by
repeating the steps.(51, 52)
• Color-Jet-Printing (CJP): this technology uses powder as a core material, and binder
as a resin and the part is built through spreading of core material in the layer, over the
build platform, using a roller. Printing head jets/spray binder (adhesive) on the

9
powder layer at specified points as decided by the CAD software, thus a colorful
product is built (printed) which has extensive usage in the medical field.(53, 54)
• Multi-Jet-Printing (MJP): nozzles are used to spray binding of liquid onto metallic or
ceramic powder to create a thin solid layer. After production of the model, it must be
sintered in the furnace to increase the strength.(55, 56)
A comparison between additive and subtractive manufacturing is shown in Table 1: (55, 56)
Additive Manufacturing Subtractive Manufacturing
Achievable complexity Can produce parts with highly complex geometries,
even better than 5-axis CNC machining. Better suited to produce relatively simple geometry.
Producible features Cannot produce features such as holes and threaded
features effectively Effectively creates holes and threaded sections.
Properties of parts produced
Parts produced may have insufficient mechanical
properties. Because the parts are created layer by
layer, structural weaknesses arise between these
layers, thereby compromising mechanical
properties and strength.
Parts produced may have excellent mechanical and
thermal properties.
Accuracy
Can achieve less dimensional accuracy. The most
accurate AM process, SLM/DMLS, can produce
tolerances as tight as 0.100 mm.
Can achieve greater dimensional accuracy. Tolerances
as tight as 0.025 mm are possible.
Production materials Works predominantly with plastics and to a small
extent, metals.
Works with a wide range of materials, including
plastics, metals, wood, foam, glass, and stone.
Finishing Parts produced always require finishing processes. Parts produced may or may not require finishing.
Setup
Requires minimal setup which results in shorter
time per part, from design to production.
After designing a CAD model of the part and
converting it, all needed is to setup the feedstock
material, allowing the 3D printer to do the rest.
Requires more effort and time in setting up. In CNC
machining, after designing a CAD model several
aspects and parameters of the CNC machine need to be
set, such as placing the workpiece on the work table,
selecting and preparing the appropriate luting fluid,
selecting and affixing the cutting tool, and setting the
right speed, feed, and depth of cut.
Scalability
Cost of production is directly proportional to
production quantity. As production quantity
increases, however, production costs rise
significantly.
Cost of production is inversely proportional to
production quantity. As production quantity increases,
production costs reduce.
Speed and cost Faster and less expensive for geometrically small
parts, plastics, and small production runs.
Faster and less expensive for relative large parts,
metals, and large production runs.
Table 1: Comparison of digital manufacturing techniques

10
2. Milled & Printed Materials
State-of-the-art restorations can be fabricated using subtractive or additive methods in the
dental laboratory or even in the dental office. In the past, ceramic materials have been used
for esthetic restorations manufactured in a manual or CAD/CAM workflow.(57). More
recently, resin composites, nano-ceramic materials and hybrid materials have been
established as an alternative. (58) Lately, mechanical and esthetic properties of computer-aided
design/computer-aided manufacturing-generated restorations(59) and the diversity of
restorative materials available for CAD/CAM systems has increased.(60)
Currently, a wide range of materials with different compositions and physical properties has
become available. Mainly, these materials have been fabricated by CAD/CAM subtractive
technologies: block materials have been used to mill restorations out of them, mainly
ceramics and resins. Dense ceramics are characterized by high hardness and wear resistance
values; yet, they cannot withstand elastic deformation because their Young moduli are much
higher than that of dental tissues.(61) Recently, new materials, such as polymer-infiltrated
ceramic network (PICN; Vita Enamic; Vita Zahnfabrik) materials and composite resin nanoceramics blocks (Cerasmart; GC Europe; Lava Ultimate; 3M ESPE) have been introduced as
alternatives to dense ceramics.(61)Vita Enamic is composed of a porous ceramic network
(86%), which is then infiltrated with a polymer by capillary action.(62) Composite resin nanoceramic blocks consist of a polymeric matrix reinforced by ceramic fillers, either nanofillers
(Lava Ultimate; 3M ESPE or Shofu Inc.; Shofu Block & Disk HC) or nanohybrid fillers
(Cerasmart; GC Europe). Industrial fabrication of these blocks under high temperature and
high pressure has led to a higher volume fraction filler and higher conversion rates (85%)
than with indirect composite resin fabricated in dental laboratories, thus significantly
improving their mechanical properties.(61, 63-65)
These industrially prefabricated polymers or acrylates offer mechanical qualities superior to
direct temporary restorations.(66, 67) The polymerization process under industrial conditions
with standardized high pressure and temperature parameters, leads to a highly homogeneous
internal structure of the blanks, offering numerous advantages: initial studies showed an
increased long-term stability, better biocompatibility and a more favorable wear behavior
compared to manually processed polymers.(68) Further studies have additionally investigated
the color stability of PMMA-based temporary high pressure CADCAM polymers and
conventional polymers compared to glass-ceramics: in these cases, high pressure CADCAM

11
polymers show comparable color stability to glass-ceramics and a significantly better color
stability than conventional resins.(69)
The application of high-performance permanent CAD/CAM polymers as long-term
temporaries offers new innovative treatment strategies and restorative approaches.
Furthermore, they offer more favorable CAD/CAM processing characteristics and can be
used in lower thickness than ceramic materials.(70-72)
However, some manufacturers have already accredited the use of their high-performance
polymer materials for permanent single-tooth restorations. While long term clinical
evaluations are not yet widely available, in vitro comparisons to already well-known and
clinically proven materials may provide some information on their suitability for long term
clinical use. Therefore, the mechanical and optical properties of high performance CADCAM
polymers must be compared to already well-known and scientifically proven concepts using
ceramic materials, which currently remains as the accepted standard for tooth-colored single
tooth restorations. Mechanical and optical properties of the high performance CADCAM
polymers are influenced by monomer composition, chemical composition as well as filler
size or arrangement of the materials itself.(65, 67, 73)
It is widely known that in dentistry, the performance of provisional restorations is paramount
since they will dictate parameters to be followed and modified according to the patient's
needs.(74) Materials commonly used to fabricate these restorations are conventional or milled
composite based resins. However, recently, 3D-printed resin-based materials have been
developed and introduced and started to be used for the manufacturing of temporary and
permanent fixed and removable dental prosthesis, and many new materials have been
developed in the past few years. These additively manufactured materials present some
disadvantages associated with their low mechanical properties, such as low-fracture
toughness which can lead to critical failure and decreased longevity.(75, 76) Other properties,
such as wear, color stability or light transmittance have not been studied nor established yet.
3D printing technologies have gathered increased popularity among technicians and
clinicians due to the wide variety of materials and respective applications, along with ease of
use. However, there currently is a lack of evidence with respect to clinical performance, as
basically in terms of mechanical and biological properties of these 3D printed materials,
intended for provisional and/or permanent restorations.(77)

12
The main reason why 3D printed resins have gained popularity among clinicians is due to
some advantages such as reduced designing times, expedite fabrication, and claimed
improved performance. Some authors demonstrated that 3D-printed resin fixed dental
prosthesis show good mechanical properties and high fracture resistance,(78, 79) making them
attractive in restorative and prosthetic dentistry for either long-term temporization or even as
a viable permanent solution. Similar to what happens to resin composites, there are a variety
of factors that can influence the final materials properties such as particle size, shape,
monomer type, flowability and/or viscosity, as well as inherent characteristics of these types
of materials and the equipment used for its polymerization, such as the polymerization time,
light source used, and its post processing steps.(77)
It is critical to evaluate the mechanical characteristics of dental materials, such as its flexural
strength, elastic modulus, and microhardness, in order to predict its clinical effectiveness and
performance.(80) More research are needed in vivo and in vitro as the literature on the
mechanical characteristics of 3D-printed permanent composite resins for dentistry is limited.
(79, 81, 82)
Flexural strength is one of the important properties in determining the mechanical
characteristics of composite resin materials,(83) and it is defined as the ability to endure under
load deformation when compressive stress and tensile stress are combined.(83, 84) It has been
determined that the flexural strength values of both CAD/CAM milling and 3D printing
composite materials might be suitable for inlay, onlay and single unit anterior and most
posterior fixed restorations.(85)
In 3D printing, layers of composite resin are gradually cured until the desired shape is
achieved to create the specimens or prosthesis. The final product’s surface and mechanical
qualities can be considerably impacted by the layers’ thickness and orientation.(86) Moreover,
additive manufacturing fabrication of specimens and prosthesis can create voids within or
between successive layers, resulting in a weaker mechanical structure. Some authors reported
that the bonds between the layers are the weakest bonds, which can be easily separated by
shear forces, reporting lower flexural strength for additively manufactured prosthesis
materials than those fabricated by subtractive manufacturing technologies.
(87)
A monomer and a photoinitiator are the components of the liquid resin used in printing.
When UV light activates the photo-initiator, it transforms the monomer into a polymer,

13
creating bonded chains at the macromolecular level. However, due to the rapid mechanism of
layer-by-layer formation, this process results in an insufficient cure density throughout each
layer added. This ultimately minimizes the effectiveness of long chain crosslinking, lower
double bond formation affects its mechanical properties.(75) On the other hand, in CAD/ CAM
milling blocks produced under high temperature and pressure, longer double bonds are
formed, the distance between the molecules is reduced and a denser structure is obtained.(86)
Thus, the amount of residual monomer is less with high monomer conversion.(84) In line with
the results obtained from the study, the relatively lower mechanical properties of 3D printed
resins compared to milling resins may be due to the presence of residual monomer.(85)
Other authors investigated the fracture load of composite resins produced by SM and AM
technique using different material thicknesses.(79) They found that 3D printed crowns
withstand similar loads as other composites, regardless of occlusal thickness. But it would be
incorrect to directly compare the current study to studies looking at the fracture load of fixed
restorations made in the form of crowns or bridges.(79, 82)
A mechanical characteristic of a material connected to stiffness is the modulus of elasticity,
which is the inclination of the stress-strain curve inside the proportional limit. The amount of
deformation within the material is directly affected by an external load. A material used in the
posterior area where masticatory loads are high must have sufficient modulus of elasticity.(88)
Most of the limited available studies demonstrate that the modulus of elasticity of the
composite resins produced with 3D printer is significantly lower than those produced with
CAD/CAM milling. The modulus of elasticity value of the milled materials is approximately
similar or close to the modulus of elasticity (16-20 GPa) reported for natural dentine.(83)
The mechanical performance of additively manufactured polymers has not yet been studied
thoroughly. Microhardness, defined as the relative resistance of a material to an external
indentation force is known as surface hardness,(63, 83) does not only dictate the esthetic
appearance but also influence plaque accumulation, carious lesion formation, and the
abrasion behavior of restorative materials. Ideal hardness is also necessary to maintain
anatomic form and stability to withstand flexural stresses caused by mastication forces in the
oral environment.(77) It has been tested and studied that composites and resins produced with
3D printing may be wear more than milling.(85)

14
A few 3D-printed materials have been recently developed and launched to the market as
definitive materials for fixed dental prosthesis, such as VarseoSmile Crown by BEGO
(BEGO, Bremen, Germany), Crowntec by Nextdent (NextDent, Soesterberg, Netherlands),
Ceramic Crown by Sprintray (Sprintray, Los Angeles, CA, USA) or Permanent Crown Resin
(Formlabs, Somerville, MA, USA). Manufacturers advocate that these materials are a viable
option for additive manufacturing of tooth-colored definitive dental restorations.(89) These
materials have been approved for single-tooth restorations such as crowns, inlays, onlays, or
veneers, and are the first available 3D-printable materials approved for definitive dental
restorations(17). These materials are basically ceramic-reinforced resins consisting of a
methacrylic ester matrix (esterification products of 4,4‘-isopropylidiphenol, ethoxylated and
2-methyl- prop-2enoic acid) with inorganic ceramic fillers (particle size 0.7 μm) and can be
classified as “resin matrix ceramics” (RMCs).(90)
Since RMCs have a relatively low flexural strength,(91) a fully adhesive luting procedure is
recommended for RMC restorations to enable an optimum connection between tooth and
restoration.(92) This results in a stable tooth-restoration complex which cannot be achieved by
conventional cementation. In various studies, the restorations were cemented using different
resin cements, such as ResiCem (Shofu Dental GmbH, Ratingen, Germany), Clearfil SA
(Kuraray Europe GmbH, Hattersheim, Germany), Panavia F2.0 (Kuraray Europe GmbH,
Hattersheim, Germany), or Panavia V5 (Kuraray Europe GmbH, Hattersheim, Germany).(93, 94)
Some RMCs should be airborne particle abraded before placement to generate an optimum
bond strength while others should be etched with hydrofluoric acid. In this way, materials
such as Lava Ultimate (3M Deutschland GmbH, Neuss, Germany), need to be airborne
particle abraded before luting, according to their manufacturer’s recommendations.(95) On the
other hand, the resin infiltrated ceramic VITA Enamic (Vita Zahnfabrik, Bad Säckingen,
Germany, Germany), has to be etched with hydrofluoric acid before luting.(95-97) For 3Dprinted ceramic materials, neither airborne-particle abrasion nor etching of the restoration is
recommended before bonding.(17) Contrary to glass ceramics, etching with hydrofluoric acid
cannot dissolve out the amorphous glass matrix in 3D printed ceramics, and is hence
pointless. However, airborne-particle abrasion of 3D printed ceramic restorations may
perhaps lead to increased bond strength values and might therefore minimize the risk of
clinical retention loss.(89)

15
3. Polymerization
When the materials to be bonded have been accordingly prepared, it’s time to apply the
bonding agent and cement, most commonly resin cement. The most common method of
polymerization of dental resin-based materials (RBMs) such as resin-based cements,
adhesives and fissure sealants is by light curing, and to date, CQ is the most commonly used
photoinitiator. (98) Polymerization is induced very slowly by CQ and tertiary amines are added
to increase the rate of curing and/or polymerization.
In dentistry, almost all of resin-based restorative products use the same basic monomer
family and polymerization mechanism: methacrylates and vinyl-free radical addition
polymerization.(98)
Use of resin-based products as restorative materials is not new. The first products used for
these purposes were based on plant or animal components and were molded to shape using
heat (thermoplastic materials). However, there was no true production-step polymerization
process in their final chemical structure. (99)
Polymethyl methacrylate (PMMA) was the first organic polymer used for construction of
heat-processed denture base materials. Before this material, dentures base materials were
made using heat-processed rubber (Vulcanite), ceramics, or swage-formed metals. The ability
for clinicians to use PMMA was based upon licenses, and the products were heavily under
control of major manufacturers.(99) After World War II, the ability to polymerize methyl
methacrylate at room temperature (the co-called, cold-cured, or chemical-cured materials)
became available.(100) With this ability, the processing of dentures became much less
expensive, and less cumbersome. Early forms of a direct, esthetic restorative material
(Sevitron, LD Caulk Company, Milford, DE, USA) used a powder/liquid system.(101) Initial
results were good, however, the restoration discolored, wore at a very high rate, and
displayed unacceptable leakage at the margins. It was not until advancements in monomer
chemistry (Bis-GMA or “Bowen’s monomer”) and the incorporation of finely ground
inorganic filler became available, that serious consideration for use of resin-based, direct,
esthetic restorative materials became a reality.(102)
To reduce resin viscosity, and thus allow higher filler loading, a functional methacrylate comonomer (triethylene glycol dimethacrylate [TEGDMA]) was incorporated.(103) This

16
formulation was first introduced to dentistry as a double-paste, self-curing system in 1969.(104)
The success of these early formulations were greatly improved, with the incorporation of
enamel acid etching and use of an unfilled boding resin to micromechanically bond the
restoration to peripheral tooth structure.(105) However, the steps needed to physically
proportion components, mix them, load the mixture into a transfer device, inject, and hold the
material under compression in a matrix material, while the chemical reaction underwent
sufficient setting to allow finishing and polishing, took up to 8 minutes, depending on the
product.(106) This gave clinicians what they wanted, namely a direct, esthetic restorative
material that literally quickly set, when the clinician decided the moment for polymerization
was needed.(104)
3.1 Free radical methacrylate polymerization
The term “vinyl” refers to the presence of an electron-rich, carbon-to-carbon double bond
appearing at the terminal end of a monomer molecule. Specifically, methacrylates are
distinguished by the presence of a methyl group covalently bond to the “α” carbon atom. The
basic structure of a methacrylate-based monomer is presented in the Figure 1, where the “R”
symbol indicates a wide variety of substitution groups that can be added to provide
monomers with unique properties. (107)
Figure 1. Chemical structure of a methacrylate-based monomer.
Substitution of the “R” with a methyl group provides the monomer methyl methacrylate, use
of an ethyl group yields “ethyl methacrylate”, a component in some temporary restorative
resins, and placement of a “hydroxyethyl” generates hydroxyethyl methacrylate (HEMA).
Substitution with other species that also contain an additional methacrylate group on the other

17
monomer end, provides what are known as “dimethacrylate” monomers: Bis-GMA,
TEGDMA, UDMA, etc. (103)
3.2 Creation of radicals
The methacrylate vinyl group can be conceived of as a “compressed spring” awaiting release
of its constrained, internal energy, which will subsequently be used to link together
(polymerize) other such methacrylate groups present in the restorative material. The key to
starting the unlocking of this internal energy is creation of a very reactive chemical species
that aggressively seeks a high-density electron location (the carbon double bond). The free
radical generator is such a species. Different types of chemicals are used for this role, but the
end result is similar: the compound is acted upon by some external form of energy (heat,
chemicals, or radiant energy), and becomes “activated.” This process is shown
diagrammatically in the Figure 2. (107)
Figure 2. Schematic illustration of external energy factors acting on a radical-generating species to result in formation of
“free radicals”.
Once in this form, the species becomes a “free radical,” having an outer shell electron
actively seeking another electron to share its orbital, thus forming a stable, covalent bond.
The clinician should note that it is this step that he/she uses to control when and how fast, and
to what extent the polymerization reaction will proceed. It is the number of free radicals
formed, the rate at which they are formed, and the rate at which they are annihilated that
controls the subsequent polymerization reaction. Thus, factors such as component
proportioning, temperature, and amount of radiant energy exposure are under the control of
the clinician, and will all significantly influence the rate at which the polymerization process
will proceed. (104)

18
3.3 Initiation of the polymerization process
Once created, the freshly formed free radical diffuses through the resin medium in search of a
highly electron-rich area, which happens to be the carbon-to-carbon double bond of a
methacrylate- based monomer. When these two species collide, the resulting effect is the
initiation of polymerization, and is displayed in the following diagram (Figure 3). (107)
Figure 3. Diagram of the polymerization initiation step.
In this process, the free radical takes one electron from the four contributing to the carbon
double bond, and forms a covalent bond between itself, and one carbon atom. In addition, the
now extra electron between the carbons atoms moves to a different shell, leaving behind a
single covalent bond between the two carbon atoms, where a double bond occupied this space
before. Now, the extra electron in the outermost carbon atom becomes the free radical
species, and actively diffuses through the low viscosity resin medium in search of another
electron-rich, carbon double bond with which to react, in a similar manner. (104)
3.4 Chain propagation
The first monomer turned free radical then seeks other electron-rich monomeric species, with
which it reacts to form covalent bonds (building the developing polymer network), and
subsequently creates a new radical end for every monomer unit that is joined. This process is
presented diagrammatically in Figure 4. (107)
Figure 4. Polymer chain propagation by addition of successive monomer units.

19
In this manner, the polymer chain grows in length, by covalently adding monomer units one
at a time. As the process continues, the rate of monomer consumption drastically increases,
resulting in a very sharp spike in the rate of the overall polymerization process (called “autoacceleration”). With increasing incorporation of monomer into the growing polymer network,
the viscosity of the resin system increases, and the rate of diffusion of growing radical ends is
greatly decreased, causing an overall lowering in the rate of polymerization, as well as
depletion of available, unreacted monomer.(104)
3.5 Termination
The polymerization reaction can stop for several different reasons. The concentration of
available monomer decreases as the reaction progresses, and the growing radical chains have
an ever-increasing difficulty in diffusing through the initially gel like and then glass-like resin
matrix. However, the most easily understood mechanism is the scenario when two growing
radical ends collide. This results in formation of a covalent bond between them, thus
quenching each radical element, bringing further growth of either polymer chain to a halt.
This process is presented in Figure 5, where two radical chains meet to form a covalent bond
between them, stopping any further chain growth. (107)
Figure 5. Diagram of chain termination via monomer-radical collision.

20
3.6 Degree of conversion
The most commonly used materials for cementation are resin cements because of their
optimal physico-chemical properties, such as their variability in tones, adequate flexural and
compressive strength, superior retention, and high fracture resistance.(108-110) These materials are
composed of a polymeric matrix based on dimethacrylate monomers, filler particles, and
pigments.(110) Resin cements are classified according to the type of filling, mode of activation
(light, chemical, and dual curing), and the bonding mechanism (self-etching and total etch).(108,
111)
Different from the traditional self-curable composite cements (which involve a pure chemical
initiation of the polymerization reaction), most of the currently available composite cements
are dual-curable (chemically and photo-activated, available in a two-component syringe) or
solely light-curable (one-component syringe). The lack of chemical initiators in the
exclusively light-curable composite cements makes their polymerization totally dependent on
the amount of energy of light transmitted through the restorative material.(112) This category of
composite cements is indicated when luting relatively thin and translucent restorations that
allow enough light irradiance (LI) to activate the photoinitiators and initiate the
polymerization reaction.(111-113) Some advantages of this mechanism are color stability, adequate
working time, and easier removal of excess cement prior to photoactivation.(110, 114)The
polymerization reaction can be affected by the composition of each product (type of
monomer, content of inorganic particles, and possible interactions between the bonding
system and cement)(108) and by extrinsic factors such as translucency and thickness of the
indirect restoration, in addition to the temperature, type, and amount of light energy
received.(108, 114-118)
To overcome the limitations of light-cured cements, dual-cured cements were designed to
ensure polymerization in regions where light curing is complex.(110, 119-122) These systems are
composed of a catalyst paste of benzoyl peroxide (initiator) and the base paste containing a
light-curing resin cement.(110, 123) The free radicals formed by the chemical reaction (tertiary
amines, benzoyl peroxide) compensate for the lack of free radicals resulting from the lightactivated initiation system (aliphatic amines, photoinitiator). Dual-cured resin cements may
have a reduction in color stability because of the possibility of oxidation that occurs in the
components involved in chemical curing (tertiary amines).(110, 111)

21
Considering that retaining good marginal integrity of an indirect restoration largely
determines the restoration’s longevity, reduced marginal leakage is the major advantage of an
adhesive luting protocol using composite cements over conventional cementation.(124) A proper
cure of the cement is essential in order to obtain good mechanical properties and avoid
cement ditching. Marginal defects are associated with a higher risk on secondary caries and
endodontic/periodontal complications.(125) The degree of conversion (DC) of composite
cements directly contributes to its mechanical properties and has even been used as a
parameter for predicting the clinical performance of restorations.(117, 126, 127)
The degree of conversion (DC) of resinous materials refers to the number of monomer units
that react to form polymers, which determines the physical and mechanical properties of each
material,(108, 114, 128) its biocompatibility, strength, elastic modulus, hardness, and solubility.(108, 110, 117,
129, 130) The literature reports that a clinically accepted DC should be between 60% and 75%. It
is commonly believed that hardness is strongly correlated with the DC. Many studies have
used Knoop or Vickers hardness tests to determine the DC, but given that most mechanical
properties of resin cements are influenced by several characteristics (type and composition of
resin, type of filler, filler loading, polymerization mode, chemical structure of the monomers,
and the type and density of the cross-links), the absolute microhardness should not be
compared with the DC values.(109, 128, 131, 132) The most precise techniques to determine
qualitatively and quantitatively the number of carbon–carbon (C = C) double bonds present in
the resin matrix are nuclear magnetic resonance (NMR), high performance liquid
chromatography (HPLC), gel permeation chromatography (GPC), multiple internal reflection
(MIR), infrared Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR).(129)
FTIR is one of the most commonly used tests owing to its fast scanning capacity, high wavelength, better resolution, stability, and accuracy.(108, 111)
The DC can be affected by the same factors involved in the polymerization reactions.
Nevertheless, there is a lack of consensus regarding the relationship between the DC and the
transmittance of light and the thickness of ceramic restorations and the polymerization mode
of the resin cement used. Runnacles et al.(118) demonstrated that the DC of light-cured resin
cement is affected by the thickness and type of ceramic used when cementing restorations
larger than 1.5 mm. Faria E et al.(133) indicated that the increased thickness of ceramic
restorations (0.5, 1, and 2 mm) resulted in radiation decrease using two LED units; however,

22
no direct relationship between the radiation loss and DC was observed in ceramic thicknesses
of less than 1.5 mm.(111)
When light transmittance is compromised due to attenuation in the overlying restoration, DC
of the composite cement may be suboptimal, having also a negative effect on the mechanical
properties of the cement and its bond strength to both the restoration and tooth substrate.(117, 134)
Moreover, unreacted monomers (not bonded to the polymeric chain) may be released, thereby
potentially irritate the pulp by generating local inflammatory responses.(112) In areas hardly
reachable by light, dual-curable composite cements are commonly indicated in order to
achieve proper polymerization thanks to the additional chemical polymerization-initiation
system. However, it has been shown that light-curing is essential even for dual-curable RBCs
in order to reach sufficient material properties.(135) Light attenuation is dependent on the fillervolume fraction, the particle size and shape, and the refractive indices of the composing
materials.(136) Moreover, translucency differs depending on the light wavelength and the
transmitted spectrum that changes continuously with depth.(136, 137) As a result, different
combinations of the light-curing unit (LCU) employed and the photo-initiator(s) present in
the light-curable material might result in variations in DC. Due to the complexity of all these
parameters involved and because of the wide variety that exists in LCUs, CAD–CAM
materials and composite cements, it would be rather complex, if not impossible, to measure
the independent effect of all these factors. Instead, direct measurement of their overall effect
is far more practical and clinically relevant than evaluating all these influencing variables
separately. This also means that attenuation is specific for each restorative material and that
the maximum thickness through which a material can be light-cured has to be determined for
the actual material and LCU.(127)
The amount of light transmitted through ceramic restorations depends on the light irradiance
of the light curing unit and the thickness, type, and translucency of the ceramic materials.(138, 139)
Although a number of studies have shown that increased thickness and darker shades of
ceramic materials act as optical barriers to light reaching the cement,(119, 131, 138) the level of light
transmittance through dental ceramics with different compositions (feldspathic, leucitereinforced, and lithium disilicate-reinforced) and translucency (high and low), and the
consequent effects on the polymerization of resin cement have not yet been fully
investigated.(118)

23
4. Photoinitiators
Once the materials intended for bonding have been appropriately prepared, the next step
involves the application of the bonding agent and the resin cement. Incoming photons are
absorbed by a photoinitiator which, when activated, enables the formation of free radicals and
thus trigger the polymerization reaction. Knowledge of the absorption spectrum of a
material’s photoinitiator chemistry is critical for effective polymerization. (107)
The guiding principle that dictates the efficiency of a photo-polymerization reaction is how
much light energy is absorbed by the photoinitiator in the system, which is dependent on the
efficiency of the light curing unit (LCU) and the total energy. (107) This means that, while light
irradiance is important, the more important factor is how much of the emitted light effectively
matches the absorption spectrum of the photo-initiator. Only when the wavelength of the light
curing unit (LCU) matches the maximum absorption of a material’s photoinitiator, efficient
light polymerization does occur. (107)
There are two types of photoinitiators: type 1 and type 2. This division is caused by different
ways of production of free radicals by these photoinitiators: in type-1 photoinitiators the
polymerization process is initiated by α-cleavage while in type-2 photoinitiators it is initiated
by H-abstraction.
Norrish type-1 photoinitiators improve material properties in dental resin composites. They
have low energy bonds which after cleavage yields more active radicals and they allow
photopolymerization by shorter wavelength, higher energy photon of violet light. Also, these
initiators improve tissue color matching as a result of low pigmentation due to shorter
wavelength range absorption and reduce the elution of residual monomers as they increase
crosslink density of resin. These photoinitiators do not require co-initiators and their color is
not as yellow as photoinitiators type 2, but after polymerization they turn yellow due to high
concentration of residual monomers. These photoinitiators undergo alpha-cleavage type of
photoinitation mechanism, where the compound breaks down into two radicals.
Type-2 photoinitiators have an absorption band that lies between 400–490 nm. The initiation
is generally slower than photoinitiation caused by type-1 photoinitiators, because is based on
a bimolecular reaction and the polymerization initiates by photons of visible blue light. The

24
co-initiators of CQ are mostly aromatic tertiary amines, and the concentration of CQ and coinitiators is obtained to gain a high degree of conversion. The polymerization is initiated by
irradiation of blue light by the carbonyl group of CQ and transition into a triplet state via
excitation into a single state. The radical formation is highly dependent upon the co-initiator
type, the concentration, and its structure. This type of photoinitiators is more useful than
type-1 photoinitiators because of better optical absorption properties in the near visible
wavelength region.
4.1 Camphoroquinone (CQ)
Camphoroquinone (CQ) is an alpha-diketone and it is type-2 photoinitiator invented by Dart
and Nemcek in 1971.(140) Its wavelength peak absorption is 468 nm, with 425 – 495 nm
absorption wavelength spectra (Figure 6). CQ is an intense-yellow-colored powder and it
adds yellow tint to the uncured composite.(107) The color bleaches after irradiation(141), but
Alvim et al. state that it has poor photobleaching and the yellow color remains the same after
exposure to blue light.(142) This poor bleaching properties are caused by chromophore groups,
which are components of CQ.
(142, 143) The yellowish staining may be a problem in color
matching,(144, 145) so it has led to less addition of photoinitiator, in order not to change the final
properties of the material. When staining occurs, it is caused by its co-initiator which
undergoes oxidation with time promoting color change of the dental resin. (146)
Figure 6. Visible light absorption spectrum of CQ, ranging from about 425 to 495 nm

25
A high degree of conversion of resin cements from monomer to polymer is required to
achieve good mechanical properties such as hardness,(147-149) flexural strength,(150) and
resistance to wear,(151) and insufficient conversion is associated with elution of substances(152-
154) and concomitant potentially toxic effects.(155) Although manufacturers usually talk about the
high tip irradiance values of their light-curing units (LCUs), they seldom discuss another
important factor for high polymerization efficiency, that is, that the emission spectrum of the
light curing unit (LCU) should match the absorption spectrum of the resin based material
(RBM) initiator. Most current light curing units (LCUs) have an emission spectrum which
peaks at around 470 nm to match the absorption spectrum of CQ.
(156) Because of the CQ is the
most common photoinitiator in resin-based composites, every property is compared to CQ’s
feature in most analysis.(157)
4.2 9,10-Phenanthrenequinone (PQ)
9,10-Phenanthrenequinone (PQ) is an alternative photoinitiator to CQ created in 1999. It is
also a 2-type photoinitiator and it requires co-initiators like CQ. It is supposed to reduce
yellow staining and to cooperate with CQ. This photoinitiator is an orange solid and it is
aromatic diketone. The absorbance maximum of PQ is at 420 nm and it could be less yellow
than CQ (Figure 7).(158)
Figure 7. Visible light absorption of the photoinitiator, 9,10-Phenanthrnequinone, spanning from about 390 to 460 nm.

26
Albuquerque et al.(158) in their analysis compared influence of CQ and PQ on properties of
resin-based composites and showed that: PQ has a higher relative photon absorption than CQ,
that the degree of conversion is the same for PQ and CQ regardless of the addition of a coinitiator and that the materials containing CQ have a higher depth of cure than those with PQ
(this is because of the absorption maximum of PQ, which is near the UV region and presents
a curve extended to visible region of the spectrum and this decreases the light irradiance and
reduces the penetration of light through restoration). The last feature which was compared
was color, finding that resin-based composites including PQ have lower color stability than
with CQ.
(158)
Recent interest in alternative initiators, involving a-diketone and acylphosphine oxide
derivatives,(159-164) has shown that these initiators result in more acceptable aesthetic properties
of RBCs compared with CQ, which is well known for its yellowing effect. The light
absorbance of these photoinitiators lies in the region below 420 nm which mismatches with
the emission range of most single-peak light-emitting diode (LED) LCUs(145, 159, 162) and
therefore may result in insufficient polymerization and lower degree of conversion (DC) and
adversely affect the mechanical properties and biocompatibility of resin-based materials.
To counteract this, dual-peak LED LCUs have been developed which have an emission peak
at about 470 nm to initiate CQ and another peak at about 400 nm for alternative initiators.
This type of light curing unit (LCU) has been shown to be efficient in photoactivation of
dental adhesives and cements containing 2,4,6-trimethylbenzoyldiphenylphosphine oxide
(Lucirin TPO), Ivocerin or 1-Phenyl-1,2-Propanedione (PPD) instead of a CQ-amine
system.(165)

27
4.3 1-Phenyl-1,2Propanedione (PPD)
1-phenyl-1,2 propanedione (PPD) is a photoinitiator which forms free radicals by cleavage
and by proton transfer from amine co-initiator.(166) It is also a 2-type photoinitiator (alphadiketone) and it has an aromatic group on one side of the carbonyl and a methyl group on the
other.(107, 167) However, there are some recent studies that suggest to classify PPD in both type I
and II, as PPD is activated in the short wavelength spectrum (blue spectrum). This
photosensitizer is a pale yellow viscous fluid and it ensures good compatibility with resins.(166)
The range of absorbance is 390–460 nm and the absorbance maximum is 410 nm (Figure 8)
(107, 167) while other sources say it is 393 nm(168) or 398 nm(144, 169) and 400 nm.(166) CQ and PPD
have almost the same light absorbance(159), and PPD can be used either synergistically with
CQ to increase the photopolymerization process(166, 170) ,or alone or with a co-initiators such as
tertiary amines or DPI salts(171) . PPD alone induces a high degree of conversion, mostly the
same as CQ.
(172) For clinicians, the main advantage of PPD is that it’s less yellow than CQ,
which is a desired feature in color matching, especially nowadays with the trend and burst of
esthetic dentistry and patient’s desiring white teeth and restorations.
Figure 8. Visible light absorption of PPD, ranging between 390 to 460 nm.

28
4.4 Ivocerin
Ivocerin is a dibenzoyl germanium photoinitiator which is patented and is available only in
select products from one manufacturer: Ivoclar Vivadent (IvoclarVivadent, Schaan,
Lichtenstein). The absorption range of Ivocerin is 390–445 nm(142) and absorbance maximum
is 418 nm (Figure 9).(170) Recently, the photoinitiator based on dibenzoyl germanium has been
added also to dental luting cements.
Figure 9. Visible light absorption of Ivocerin® is seen to span from about 390 to 445 nm.
Luting cements containing dibenzoyl germanium (Variolink E, Ivocerin) are characterized by
higher degree of conversion and color stability comparing to luting cements containing CQ.
The degree of conversion of cement containing Ivocerin is about 87%, but cement containing
CQ and tertiary amine has about a 44% degree of conversion. Other authors proved that
Ivocerin-based cement has the highest Vickers micro-hardness (47 VHN), while CQ-based
cements have about 33 VHN.(173) Moreover, Delgado et al. proved in their studies that flexural
strength of cements containing Ivocerin is very similar to flexural strength of CQ-cements:
the value of flexural strength of Ivocerin is 119.93 MPa while it is 120.41 Mpa for CQ.
(174)
Due to shorter wavelength absorption range than CQ, these newly introduced photoinitiators
(Lucirin TPO, PPD and Ivocerin) require polywave LED LCU dental light curing units. The
common light-curing units have spectrum limited to 420–490 nm and it is not sufficient for
resin-based composites with photoinitiators such as Lucirin TPO, PPD or Ivocerin.(175) The

29
best properties of these photoinitiators was gained when polywave light-curing units were
used.(165, 176, 177) Single-peak light-curing unit have narrow range of light: 450–470 nm and the
absorption of Lucirin TPO, PPD and/or Ivocerin is out of this range. However, polywave
light-curing units are provided with extra light range: 400 to 415 nm and the exposure of
resin containing Lucirin TPO, PPD or Ivocerin to the light is sufficient.(178)
In a previous study, a dual-peak LED LCU resulted in a higher DC than a single-peak control
in experimental unfilled resins containing only Lucirin TPO, only CQ-amine, or their
combination. (91)
4.5 Lucirin TPO
2,4,6-trimethylbenzoyl-diphenylphosphine oxide (Lucirin TPO)(175) is type-1 photoinitiator
based on acylphosphine oxide. It can be a stand-alone photoinitiator system or it can be used
synergistically with CQ and it does not require co-initiators to accelerate
photopolymerization process.(179, 180) The use of Lucirin TPO eliminated the amine group and
that increase stability of color upon aging(181) and the color stability is the highest.(159, 181) TPO
has narrow wavelength absorption range 380–425 nm(182) and the maximum is 400 nm(182) or
other source said it is 381 nm.(145)
Figure 10. Visible light absorption of the photoinitiator, Lucirin® TPO, spanning from about 390 to 410 nm.

30
The composites including TPO have many advantages respect to CQ, such as:
- Higher degree of conversion than the composites containing CQ,
(177, 179, 183, 184) as TPOcomposites display an average 10% conversion increase.
- Esthetics: TPO-based materials show great color stability(176, 181, 185, 186) and also can
mimic the optical characteristics of teeth such as color, opalescence and
translucency.(146)
- Faster polymerization than CQ-composites. The irradiation times are equal or greater
than 3 seconds.(187) Lucirin TPO is more reactive than CQ even it does not require coinitiators.
- The temperature increase of TPO resin-based composites is lower than CQ controls.
- The polymerization efficiency in dental resin is higher when TPO is used in dental
resin, compared to CQ and PPD’s efficiency, when the halogen light curing unit
initiates the polymerization.(178) Lucirin TPO is more effective than CQ, because it
produces two free radicals by α-cleavage, when CQ delivers only one. The first TPO’s
radical is more competent as an initiator of polymerization, but it also can abstract
protons from the medium and create a second radical.(159, 188)
- The surface hardness is higher when TPO is used, as compared to CQ.
(189) The flexural
modulus and hardness were significantly higher in TPO-materials than CQcomposites, but flexural strength of TPO-composites and CQ-controls is similar.
The main disadvantage of TPO-based composites is generation of higher polymerization
stresses than CQ-controls,(184) while the second main disadvantage is lower depth of cure
compared to CQ-containing mixture. (176-178, 186)

31
5. Light Curing Units (LCUs)
Resin-based composites (RBCs) were first introduced in the 1960s(190) and, with the
development of effective and reliable dentine bonding systems in the late 1980s,(191) have been
used routinely as a filling material for both anterior and posterior teeth. The early RBCs were
chemically cured, two-component materials and visible light-curing RBCs, using CQ as an
initiator, were first reported in 1978.(192) Light-curing materials contributed a significant
clinical advance over the auto-cured materials(193) and, in addition to direct RBC restoration
materials, they include luting agents for ceramic restorations, pit and fissure sealants and
resin-modified glass ionomers.
The mode of curing has changed with time. The first report of a light curing material was of
an ultraviolet (UV) cured fissure sealant.(194) However, owing to the limited penetration depth
of the UV light and the potential health hazards, this system was quickly abandoned. Today,
four types of light curing unit (LCU) are available for clinical use: (195)
- Quartz tungsten halogen LCU‘s (QTHs)
- Light-emitting diode units (LEDs)
- Plasma-arc LCU’S
- Argon-ion lasers
The main factors that play a role and affect the polymerization process are the following:
- Filler type, size and loading.
- The thickness and shade of the restorative material.
- The effectiveness of light transmission (for example, the condition of the light guide
tips, in terms of being free from debris and scratches).
- Exposure time
- Light irradiance
- Distance of the light source from the restorative material.
Commercially available curing units have different light intensities and light sources, with
energy levels in QTH, LED and other LCUs ranging from 300 to more than 2000 mW/cm2
.

32
5.1 Halogen light curing units (QTH LCUs)
Until recently, halogen LCU’s were the most frequently used dental LCUs and many remain
in use in dental practices. Only a small part of their wide spectral emission occurs in the
useful range. Much of the light emitted from these LCU’s is therefore ineffective and may
cause unwanted increases in tooth temperature.(196) QTH LCUs, still generate 93% of the total
energy production in the form of heat.(197)
The physical basis for light production in QTH LCUs is that heated objects emit
electromagnetic radiation. (198)
Light is produced when an electric current flows through a thin tungsten filament surrounded
by halogen gas. Because the filament acts as a resistor, the passage of current generates heat.
To provide blue light for photo polymerization, QTH LCU filaments require to be heated to
high temperatures emitting wavelengths covering a large part of the spectrum. Their
collective emission results in the production of white light. To produce light of a specific
waveband or color, unwanted portions of the spectrum must be filtered out. As a result, the
largest part of the radiative power of this light source is wasted and the principal
disadvantage of QTH LCUs is the need to overcome unwanted heat.(198)
Main benefits of QTH LCUs are the fact that it’s a low-cost technology and that it has been
used for many years in dentistry. However, it has many drawbacks, such as its low efficiency,
the high temperatures it reaches (LCU cooled by ventilating fan) or its short service light.(198)
Moreover, since a fan cooling air current must enter and exit through slots in the frame
casing, disinfection of the LCU is problematic. Another drawback of QTH LCUs is that the
bulb, reflector, and filter can degrade over time, interfering with light unit power output and
contributing to bulb fading. The LCU reflector may lose its reflective properties because of
loss of reflective material, or deposition of surface impurities. Filter coatings may become
pitted, chipped, or flaky, and the filters themselves may crack or break. Loss of any or all of
these properties reduces light output and compromises photo polymerization. (198)

33
5.2 LED Light curing units (LED LCUs)
LEDs use a semiconductor material system (gallium nitride) to generate blue light of selected
wavelengths and narrow spectral distribution of between 400 and 500 nm without the
requirement of filters. The chemical composition of the semiconductor combination can be
altered to obtain a specific wavelength range. This is a much more efficient way of
converting an electric current into light compared to QTH LCU technology.(199)
The main advantages of LED LCUs are that they have a consistent output (with no bulbs to
change), there’s no need for filter systems, are quiet, have long service lives, low power
consumption and high efficiency, leading to low temperature development and no ventilation
fan required in most models. (199)
However, the main drawback, is that older generation LEDs can only polymerize materials
with an absorption maximum between 430 and 480 nm (CQ as a photoinitiator), mainly
owing to the narrow emission spectrum. However, this is not applicable to newer models. (199)
The primary absorption curve of CQ ranges from 425 to 495 nm, with its maximum at 468
nm. Within this range, optimal emission of the light source lies between 450 and 490 nm.
Ninety five percent of photons emitted by older blue LEDs occur between 440 and 500 nm,
while that of some newer types, such as bluephase® (IvoclarVivadent, Schaan, Lichtenstein),
have a spectral wavelength of 380 to 500 nm. The emission maximum of the blue LEDs is
approximately 465 nm, almost identical to the absorption peak of CQ. (200)
The performance of first-generation LED LCUs were only comparable with that of standard
QTH LCUs. Advances in LED technology have made it possible to develop high power
LED-based systems which now are equivalent to high irradiance QTH or plasma arc LCUs.
The earlier versions of blue LEDs had low light irradiance and required the use of many
LEDs to provide adequate performance. Marked improvements in LED technology have
resulted in the development of several types of commercial LED LCUs with improved
irradiance output, resulting in a depth of cure (DoC), equivalent to that of conventional QTH
units at equivalent light exposure times.(200)
Newer high power LED LCUs have light intensities approaching 2000 mW/cm2 and, if used
at maximum power, may present as much of a heat problem as high power QTH LCUs,

34
especially when there is a reduced remaining dentine thickness, and with darker shades of
RBCs.(201)
Lightweight, portable and highly efficient LED units are now available. The first generation
of LED’s were launched without the need for filter systems or cooling fans. However, as the
greatest determinant to diode life is overheating and some of the newest LED LCU’s are very
powerful, newer models do use filter systems and/or internal fans to draw heat away from the
diodes. (201)
5.3 Plasma Arc LCU’s (PALs)
Plasma-arc lights (PALs) work by the application of a high voltage current across two
electrodes within a gas-filled fluorescent bulb. The term “plasma” refers to the gas which, in
the case of dental LCUs, is xenon, and most of its atoms or molecules are ionized. The
current heats the plasma to several thousand degrees Celsius producing ultraviolet radiation
which, when it collides with the bulb wall, is converted to light and heat. PALs have low
efficiency, with most of the energy given off as heat, and less than 1% given off as light.
Their power consumption is higher than that of QTH LCUs and they have a high operating
temperature which makes the use of ventilating fans necessary. In addition, PALs spectral
output is continuous and must be filtered to provide the useful blue light. (201)
PALs were introduced with the claim that they could decrease curing times significantly
without a concomitant reduction in mechanical properties and performance of the cured
materials,(201) though this is not unequivocally supported.(202) Typically, adequate curing results
can be obtained only if the cure, or exposure times are extended beyond those recommended
by the devices’ manufacturers and, additionally, high-irradiance PAC lights may increase
heat generation in the cured dental materials, leading to pulpal damage.(203)
5.4 Laser lights (LLs)
Laser lights are based on the laser principle (light amplification by stimulated emission of
radiation). They emit light at specific wavelengths as a result of the excitation of atoms of
suitable gases which, in the case of dental LLs is argon, at specific energy levels. They have
the advantage of having narrow spectral emission characteristics producing blue light, which

35
may be readily adapted to dental photoinitiators, without the need for filters. Because of their
low energy conversion, they require a larger base for power supply and cooling, making the
units large and expensive and, for these reasons, they have generally fallen out of favor. (203)
5.5 Polymerization of composite resins and adhesives
To ensure adequate polymerization of RBCs, it is essential that the LCU produces sufficient
light power. Insufficient polymerization of RBCs may lead to failures in the placement of
direct or indirect restorations and may cause postoperative sensitivity, more rapid
discoloration, increased wear, premature fracture and the necessity of endodontic treatment.
(204)
The efficiency of LCUs is usually discussed in terms of light irradiance (mW/cm2) or, less
commonly, as radiation flux density. The effective range of the light emission spectrum that
can initiate polymerization is relatively narrow. (204) Low levels of polymerization leads to
deterioration in mechanical and physical material properties, and increases water absorption,
leaching out of components and susceptibility to discoloration. (204)
Bis-GMA (2,2-bis [4-(2-hydroxy- 3-methacrylyloxy-propoxy)phenyl]propane) remains the
most common molecule in modern RBCs. It has a high cross-linking ability and a lower
shrinkage than pure methacrylate’s, though polymerization shrinkage remains the single most
significant problem related to RBC restorations. Other methacrylate’s, such as UDMA
(urethane dimethacrylate), are frequently added to improve color stability, hydrophobicity,
high viscosity and tensile strength.(204)
Although sufficient light irradiance of the LCU is a fundamental prerequisite for proper
polymerization, the degree of conversion (DC) is dependent on several additional factors,
such as filler size and shape, optical translucency and the refractive index of the material.(205,
206)
The DC is never 100%, and low conversion affects many properties and compromises wear
resistance, fracture toughness, flexural modulus, hardness, flexural fatigue, dimensional
stability, and color change. Additionally, low conversion leads to higher permeability, more

36
water sorption and leaching out of residual uncured monomers in the clinical situation. Eluted
dimethacrylates have been shown to exert cytotoxic and endocrine disruptive effects.
It has been stated that the success and dependability of RBC restorations depends on the
degree of conversion or polymerization (DC) of the material.(207) The DC will be impacted by
many factors, which mainly depend on the material (composition, shade), the photoinitiator
present, properties of the LCU (spectral output, power irradiance, wavelength, lens diameter),
and the curing conditions (distance to the material).(207)
Regarding this last point, many units now offer a variety of light guide tips to facilitate
occlusal surface curing. In a study comparing curing tips of diameters 4 mm, 7.5 mm, 10.5
mm and 12 mm, irradiance values for the same LCU ranged from 547 mW/cm2, for a 12 mm
tip to 2574 mW/cm2 for a 4 mm tip. Variability in light irradiance across the curing-tip face
and the spectral output of dental light-curing units significantly influence curing efficiency
across RBC restoration surfaces.(208)
Since LCU energy output is the product of irradiance and time,(209, 210) the same amount of
energy can be absorbed by a material by adjusting the exposure time to maximize energy
efficiency. Factors, such as RBC composition and shade, may affect the DC so making it
difficult to define what is an adequate energy level. Many LCUs produce lower output
intensities than stated by the manufacturer,(211) and of greater concern are the results of studies
which show that the light intensities of LCUs are often inadequate for optimum curing,
though there has been overall improvement in the last decade.(211)
Light irradiance output changes as the LCU ages with use and an obvious reduction in
irradiance has been recorded with older units,(212) and it has been recorded that there is a lack
of awareness among dentists of the need for maintenance and regular checking of the light
irradiance of these units.

37
6. Spectrophotometers and transmittance of light
6.1 Basics of light behavior and interaction
Reflection is the process by which electromagnetic radiation is returned either at the
boundary between two media (surface reflection) or at the interior of a medium (volume
reflection), whereas transmission is the passage of electromagnetic radiation through a
medium. Both processes can be accompanied by diffusion (also called scattering), which is
the process of deflecting a unidirectional beam into many directions. This is called diffuse
reflection and diffuse transmission (Figure 11). When no diffusion occurs, reflection or
transmission of a unidirectional beam results in a unidirectional beam according to the laws
of geometrical optics (Figure 12). In this case, it is called regular reflection (or specular
reflection) and regular transmission (or direct transmission).(213)
Figure 11. Reflection (left) and transmission (right)
Figure 12. Top: direct, mixed and diffuse reflection. Bottom: direct, mixed and diffused transmission

38
There are three traditional methods of studying the translucency of dental ceramics: direct
transmission, total transmission (including scattering), and spectral reflectance. However, the
translucency values vary depending on the measurement methods, such as transmittance or
reflectance. Additional studies to determine which translucency measurement methodology
best reflects the clinical situation, and its clinical relevance, are needed. (214)
The optical transmittance of solids and liquids as well as the absorptivity of various chemical
species are parameters of fundamental significance in characterizing materials. Meaningful
transmittance data can be obtained only when the measurements are performed with wellknown accuracy and precision. To perform such measurements, a high accuracy
spectrophotometer is normally used, being a single-beam instrument composed of a constant
radiation source, a monochromator, a sample carriage, an integrating sphere-photomultiplier
assembly followed by appropriate electronics, and a read out system consisting of a digital
voltmeter and a computer data acquisition and handling provision. (215)
In general, reflection, transmission and absorption depend on the wavelength of the affected
radiation. Thus, these three processes can either be quantified for monochromatic radiation or
for a certain kind of polychromatic radiation. For the latter, the spectral distribution of the
incident radiation must be specified. In addition, reflectance, transmittance and absorptance
might also depend on polarization and geometric distribution of the incident radiation, which
therefore also have to be specified.(213)
Reflectance and transmittance are characteristics used to describe the optical properties of
materials. These can apply to complex/polychromatic radiation or to monochromatic radiation.
The optical properties of materials are not a constant since they are dependent on many
parameters such as: thickness of the sample, surface conditions, angle of incidence,
temperature, the spectral composition of the radiation and/or polarization effects.(213)
Optical transmittance is due to an intrinsic property of a material and characterizes a
particular translucent material. Since this parameter is not known a priori, it must be
determined by experimental procedures. True transmittance values can be obtained only by
using accurate measuring techniques and by taking into consideration all factors which can
affect and distort the data.(215)
Every chemical compound absorbs, transmits, or reflects light or electromagnetic radiation
over a certain range of wavelength. Spectrophotometry is a measurement of how much a

39
chemical substance absorbs or transmits and it is widely used for quantitative analysis in
various areas (e.g., chemistry, physics, biology, biochemistry, material, and chemical
engineering, etc). Any application that deals with chemical substances or materials can use
this technique.(216)
6.2 Transmittance Spectrophotometers
A spectrophotometer is an instrument that measures the number of photons (the irradiance of
light) absorbed after it passes through sample tested. It is apparent that less light is allowed to
pass through a highly turbid or colored solution or sample than through a clear one. The
spectrophotometer is the device that can quantify the amount of light transmitted through
samples and solutions. By using a spectrophotometer, the amount of a known chemical
substance (concentration) can also be determined by measuring the irradiance of light
detected. Depending on the range of wavelength of light source, it can be classified into two
different types:(217)
- UV-visible spectrophotometer: uses light over the ultraviolet range (185 – 400 nm)
and visible range (400 – 700 nm) of electromagnetic radiation spectrum.(217)
- IR spectrophotometer: uses light over the infrared range (700 – 15000 nm) of
electromagnetic radiation spectrum.(217)
In visible spectrophotometry, the absorption or the transmission of a certain substance can be
determined by the observed color. When light is transmitted through a sample, some of it
may be absorbed. If the absorption occurs in the ultraviolet or infrared regions of the
electromagnetic spectrum, the solution will appear colorless. But if the absorption occurs in
the visible region of the spectrum, the solution will appear colored. For instance, a sample
that absorbs light over all visible ranges (i.e., transmits none of visible wavelengths) appears
black in theory. On the other hand, if all visible wavelengths are transmitted (i.e., absorbs
nothing), the solution sample appears white. In practice, visible spectrophotometers, use a
prism to narrow down a certain range of wavelength (to filter out other wavelengths) so that
the particular beam of light is passed through a sample.(218)

40
A spectrophotometer consists of a light source (visible, UV, or both), a collimator, a
monochromator (to obtain a single fixed wavelength), a wavelength selector, a sample
compartment (which holds a sample tube or cuvette of fixed path length), a photoelectric
detector or phototube (to measure this light and display a reading on the meter panel) and a
digital display or a meter. Detailed mechanism is described below (Figure 13).(217)
Figure 13. Spectrophotometer mechanism (diagram)
Inside a spectrophotometer, light is focused through a lens system to an entrance slit. The
light rays are refocused by a second lens onto an exit slit. Between the second lens and the
exit slit is a monochromatic grating which separates the white light into its component
wavelengths in much the same fashion as a prism. By proper rotation of the monochromatic
grating, specific light wavelengths may be passed on through the exit slit to a photocell. This
cell is connected directly to a galvanometer which translates the electrical output of the
activated photocell into a specific transmittance value. (218)
In between the exit slit and the photocell is a chamber where samples may be placed. A clear
specimen will yield 100% transmittance, while a turbid sample will deflect a considerable
portion of the light rays and will have a lower percent transmittance. The greater the density,
the lower the percent transmittance. (218)
A spectrophotometer, in general, consists of two devices; a spectrometer and a photometer. A
spectrometer is a device that produces, typically disperses and measures light. A photometer
indicates the photoelectric detector that measures the irradiance of light.(217)

41
- Spectrometer: It produces a desired range of wavelength of light. First a collimator
(lens) transmits a straight beam of light (photons) that passes through a
monochromator (prism) to split it into several component wavelengths. Then a
wavelength selector (slit) transmits only the desired wavelengths. (217)
- Photometer: After the desired range of wavelength of light passes through the
sample, the photometer detects the amount of photons that is absorbed and then sends
a signal to a galvanometer or a digital display. (217)
Transmittance of light is simply the percentage of light impinging on a solution or object that
passes through and emerges to be detected by an instrument. It is zero for a completely
opaque solutions or objects and 100% when all the light is transmitted. Transmittance and
absorbance measure the same, but the scales are reversed, and they are divided differently.
Absorbance is the flip side of transmittance and states how much of the light the sample kept
and didn’t allow to emerge though it.
As transmittance is the ratio of two radiation flux intensities, it is therefore necessary that the
photometric scale of the spectrophotometer used to perform the measurements is accurate.
The transmittance of a particular material is also a function of wavelength, so the wavelength
scale of the monochromator should also be accurate. The measurements should be made
using collimated radiations (a beam of light that has parallel rays, and therefore will spread
minimally as it propagates). Such radiations define the actual path length through the
transmitting medium, the reflection losses, and eliminates the effects of polarized radiations
that are produced at the surface of the sample.
Other important factors which must be considered are: homogeneity and stability of the
sample, radiation scatter inside the sample, interference phenomena, stray radiation (leakage
and scattered radiation), polarization, fluorescence, temperature, and surface conditions.
Since transmittance measurements depend on a diversity of factors, meaningful values can be
obtained only by defining the experimental conditions for obtaining transmittance data.

42
6.3 Reflectance Spectrophotometers
The final color of an all-ceramic restoration is a merging of the underlying tooth structure or
core and the ceramic material. The color of the final restoration cannot match the shade
selected from a shade guide unless this modification is considered. Therefore, a stump or base
tooth preparation shade needs to be obtained and transmitted to the technician.(219)
Dental shade-matching instruments have been brought to market to reduce or overcome
imperfections and inconsistencies of traditional shade matching. Historically, assessing shade
visually has been characterized by several innate difficulties: metamerism, suboptimal color
matching conditions, tools and method as well as the receiver’s age fatigue, mood and
drugs/medications.(220) Despite these difficulties, the human eye can discern very small
differences in color. However, the ability to communicate the degree and nature of these
differences is lacking.
During the past half decade, the dental profession has experienced the growth of a new
generation of technologies devoted to the analysis, communication, and verification of shade.
Shade determination for direct and indirect restorations has always been a challenge for the
esthetic dentist. As opposed to subjective visual shade selection with not always quite
controlled conditions and methods, and shade guides that exhibited significant shortcomings,
several authors tried to objectively quantify tooth color in the past. This was done through
identifying color problems in dentistry(221); the importance of the quantity and quality of light
required to properly analyze shade(222) through studying correlation between extracted teeth
and shade guides(223) or the development of the early shade measuring instruments and shade
guides.(224)
The late 1990s marked the birth of a new industry in dentistry, with commercially available
instrument-based color measurement systems. These are also called spectrophotometers.
However, these are not transmittance spectrophotometers, but reflectance spectrophotometers,
which are the most used and known spectrophotometers in dentistry. They are amongst the
most accurate, useful and flexible instruments for overall color matching and color matching
in dentistry.(225) They measure the amount of light energy reflected from an object at 1–25 nm
intervals along the visible spectrum.(226, 227) These kind of spectrophotometers contain a source
of optical radiation, a means of dispersing light, an optical system for measuring, a detector
and a means of converting light obtained to a signal that can be analyzed. The data obtained

43
from reflectance spectrophotometers must be manipulated and translated into a form useful
for dental professionals. The measurements obtained by the instruments are frequently keyed
to dental shade guides and converted to shade tab equivalent.
(228) Compared with observations
by the human eye, or conventional techniques, it was found that spectrophotometers offered a
33% increase in accuracy and a more objective match in 93.3% of cases.(229)
The invention and use of reflectance spectrophotometers was the first effort toward a shade
analysis system for complete tooth surface measurement. Today’s shade-matching
technologies have been developed in an effort to increase the success of color matching,
communication, reproduction and verification in clinical dentistry, and, ultimately, to
increase the efficiency of esthetic restorative work within any practice. (230)

44
7. Importance of light transmittance in dentistry
The interaction of light with dental materials is of main importance from two standpoints:
first, from the esthetic point of view, and secondly, from the curing and depth of cure point of
view.
From the esthetics point of view, it is widely known that the final appearance of a restoration
depends on many factors, mainly color, translucency, opalescence, fluorescence and
metamerism. To produce a highly esthetic and mimetic restoration, color is very important,
but translucency is considered as a key factor. Human teeth are characterized by varying
degrees of translucency, which can be defined as the gradient between transparent and
opaque. Translucency is defined as the physical and optical property allowing light to pass
through the material by scattering of photons, creating a change in index of refraction, while
transparency is defined as the physical property allowing light to pass through the material
without appreciable scattering of light. In other words, a translucent material is made up of
components with different indices of refraction, while a transparent material is made up of
components with a uniform index of refraction.
For this reason, dental materials should be somehow translucent, to generate this translucent
effect like teeth and achieve highly esthetic results. Ceramic materials have been advocated
rather than traditional metal ceramic restorations because of their excellent esthetics and
acceptable mechanical properties. Since dentin and enamel have inherent translucency(231, 232)
esthetically matching ceramic restorations with adjacent natural teeth should involve not only
shape and texture but also the reproduction of the optical characteristics of natural teeth. The
translucency of ceramics has been emphasized as one of the primary factors in controlling the
esthetic outcome of ceramic restorations.(233) In addition, the translucency of ceramics is also
closely related to light transmission and the polymerization efficiency of underlying resinbased cements. (234-236)
From the curing point of view, the interaction of light with dental materials is very important
too. Nowadays, most of the materials we are using are luted to teeth by bonding agents,
mainly adhesives and cements. In most of cases, these luting agents are activated using a
curing light which initiates the polymerization and curing process. It is important to make
sure that the light from the curing light will be able to reach the adhesive and/or cement

45
placed beneath the restoration, between the tooth structure and the material itself. Many
factors influence the amount of light that will transmit through the material, such as:
- LCU related factors (irradiance, spectral output, wavelength, and light guide
diameter).
- Distance from LCU to material.
- Material-related factors (thickness, filler particles, filler structure, filler grain size,
resin matrix composition, pigments, polymerization, aging, number, size, and
distribution of defects, porosity, and refractive index of filler and organic matrix).
Light transmittance is a crucial factor when choosing the specific luting procedure, as it
determines whether the light will pass through the restoration and reach the cement with
sufficient effectiveness to perform the cure. Transmittance is generally defined as the relative
amount of light passing through the material, with the remaining light being reflected or
absorbed within the visible spectrum (400 to 700 nm). When light is passing through a
ceramic material, light is intensely scattered and diffusely reflected, leading to a more opaque
appearance and low transmittance values. When only some of the light is scattered and most
is transmitted the material will have higher transmittance values. Transmittance (T) is the
fraction of incident light, which is transmitted, in other words, it’s the amount of light that
“successfully” passes through the substance and comes out the other side. It is defined as T =
I/Io, where I = transmitted light (“output”) and Io = incident light (“input”). %T is merely
(I/Io) x 100.
Light transmittance is a crucial factor when choosing the specific luting procedure (lightcure, or dual-cure), as it determines whether the light will pass through the restoration and
reach the cement with sufficient effectiveness to perform the cure. The light used during
curing polymerization is blue and violet light, and therefore it is the amount of light within
the violet [380-450 nm] and blue [450-500] spectrums passing through the restoration that is
decisive and not the amount of light within the visible spectrum (400 to 700 nm).
Finally, another parameter that has an influence on the amount of curing light that is
transmitted through a material is the thickness of the material itself. It is widely demonstrated
that changing (by increasing) the thickness of a material, normally results in a large decrease
in translucency. However, it is also material-dependent: the change in translucency when
changing thickness varies in respect to the material used or studied.

46
In dentistry, the materials most widely used are ceramics and resins. For ceramics, the
transmission coefficient at different thicknesses has been evaluated but there is not a clear
conclusion about it, as it is material and light dependent.(235, 237) One first study by Antonson et
al. found that the transmission coefficient of dental ceramics was linearly related to the
thickness.(237) Another study by Peixoto et al. found an exponential increase of the
transmission coefficient of a porcelain with a decrease in thickness.(235) For composites, there
are studies evaluating the influence of thickness of a material in its translucency, such as the
study by Kamashima et al. or Kim et al., that report that the translucency of composite resins
increased exponentially as the thickness decreased.(238, 239) However, although the thickness of
a restoration it is a very important factor to consider when thinking about the amount of
curing light passing through a material, there is still misunderstanding regarding the
correlation between the transmittance and thickness of glass ceramics has been achieved.
Nowadays, most of the materials used are CAD/CAM materials produced either by additive
or subtractive manufacturing technologies. The most common used materials are ceramics for
definitive restorations and resins for provisional restorations. Despite their widespread use,
little information is available concerning the transmittance of light in resin materials
advocated to be used for definitive restorations. Thus, this study was conducted to evaluate
the transmittance of curing light through different CAD/CAM-generated resin materials
advocated to be used for definitive restorations and to evaluate if different materials,
thicknesses and light wavelengths play a role in light transmittance. Therefore, the aim of this
investigation was to evaluate the transmittance of visible light (mainly violet [380-450 nm]
and blue [450-500] light) through two additively manufactured permanent CAD-CAM resin
materials (printed) for definitive restorations in comparison with one subtractively
manufactured CAD-CAM resin materials (milled) as a function of material, a function of
thickness and a function of wavelength.

47
Chapter Two: Hypothesis & Objectives
1. Question/s:
1. How much light transmits through additively manufactured permanent CADCAM resin materials (printed) for definitive restorations in comparison with
subtractively manufactured CAD-CAM resin materials (milled)?
2. Does the thickness of these materials influence the transmission of curing
light?
3. Does the wavelength of the irradiant light influence the transmission of curing
light?
2. Null hypothesis:
1. There is no difference in the irradiance of transmitted curing light between the
additively manufactured permanent CAD-CAM resin materials (printed) for
definitive restorations in comparison with the subtractively manufactured
CAD-CAM resin materials (milled).
2. There is no difference in the irradiance of transmitted curing light between the
different thicknesses of the materials tested.
3. There is no difference in the irradiance of transmitted curing light between the
different wavelengths of the irradiant light.
3. Objective/s:
1. To evaluate the transmittance of visible light (mainly violet [380-450 nm] and
blue [450-500] light) through two additively manufactured permanent CADCAM resin materials (printed) for definitive restorations in comparison with
one subtractively manufactured CAD-CAM resin materials (milled) as a
function of material, a function of thickness and a function of wavelength.

48
Chapter Three: Materials and Methods
A total of 120 flat, squared samples were made from three different CAD CAM resin
materials for definitive restorations. For each material, the samples were fabricated and
sectioned in different thicknesses to evaluate the influence of material composition and
thickness on light transmission at different wavelengths. The thicknesses studied were 1 mm,
2 mm, 3 mm and 4 mm.
MATERIALS
MILLED PRINTED
Name Lava Ultimate VarseoSmile Crown Plus Ceramic Crown
Brand 3M BEGO Sprintray
Content Matrix Highly cross-linked
polymeric matrix
20
wt%
Esterification products of
4,4‘-isopropylidiphenol,
ethoxylated and 2-methylprop-2enoic acid.
50-75
wt%
Methacrylate oligomers 20-60 wt%
Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide.
< 2.5
wt%
Methacrylate and acrylic
monomers
20-50 wt%
Filler Nano-ceramic
components
(zirconium dioxide
and silicone oxide
nano-particles)
80
wt%
inorganic fillers (silanized
dental glass, particle size
0.7 μm)
30 - 50
wt%
Additives (inorganic
fillers)
>50 wt%
Properties Appearance/State Solid Liquid Liquid
Viscosity Not applicable 2,500 – 6,000 mPa 2,500 – 6,000 mPa
Density 2.1 g/cm3 1.4-1.5 g/cm3 1.6-1.7 g/cm3
Flash Point Not applicable 110ºC 110º
Flexural Strength 204 MPa 116 – 150 MPa 150 ±25 mPa
Flexural
Modulus
12.80 MPa 4,090 MPa 7,800 ± 500 MPa
Water Solubility Negligible < 1 µg/mm3 2.16 ± 1.30 μg/mm3
Water Sorption Not applicable < 12 µg/mm3 17.35 ± 2.56 μg/mm3
Color Used A1 A1 A1
Batch Number NA21524 600577 S23C14CA11
Table 2. Materials used in the study (2, 10, 58, 65)

49
Each material was considered as a group, and each group was divided into four subgroups,
based on their thickness (1 mm , 2 mm, 3 mm and 4 mm). Ten samples from each thickness
were fabricated for each material, polished until a smooth, scratch-less, glossy surface was
achieved and tested my means of a Spectrophotometer equipped with a 150mm integrating
sphere (Perkin Elmer, Waltham, MA, USA) to evaluate the transmittance of light through
these CAD CAM resin milled and printed materials for definitive restorations.
Figure 14. Summariez diagram regarding materials, groups and subgroups
Total specimens per each material (n=40)
Milled materials Printed materials
Lava Ultimate
VarseoSmile
Crown Plus Ceramic Crown
1 mm 2 mm 3 mm 4 mm
Transmittance testing (%T) using UV-Vis-Nir Spectrophotometer

50
Figure 15. Summarized workflow and steps taken
Study Design
Specimen
preparation
Testing
Statistical
Analysis
Select materials to test
Sectioning of milled
materials
Slicing and printing of
3D printed materials
Specimen design
Polishing of all materials
Transmittance Analysis
Transmittance Analysis

51
1. Milled material (control) – Lava Ultimate (3M, St. Paul, MN, USA) - (Group
A)
Specimens from Lava Ultimate (3M, St. Paul, MN, USA) material were used in this group.
These specimens were fabricated from a 14L Lava Ultimate block (3M, St. Paul, MN, USA),
which is 14.5 mm x 14.5 mm x 18.00 mm in size.
The Lava Ultimate blocks (3M, St. Paul, MN, USA) were precisely cut and sectioned with a
diamond blade -Isomet diamond blade, 15LC, 3in (Buehler Ltd., Lake Bluff, IL, USA)- at
900 rpm to get 40 specimens (10 per subgroup).
Figure 16. Machine used for cutting the specimens
Figure 17. Lava Ultimate block used

52
Each subgroup had varying thicknesses:
- Subgroup A1 consisted of ten 1 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 1.00±0.1 mm
- Subgroup A2 consisted of ten 2 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 2.00±0.1 mm
- Subgroup A3 consisted of ten 3 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 3.00±0.1 mm
- Subgroup A4 consisted of ten 4 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 4.00±0.1 mm
Figure 18. 1 mm to 4 mm Lava Ultimate polished samples

53
2. Printed material 1 - VarseoSmile Crown Plus (BEGO, Bremen, Germany) -
(Group B)
Specimens from VarseoSmile Crown Plus (BEGO, Bremen, Germany) material were used in
this group. These specimens were fabricated by 3D-printing from a liquid resin. Forty
specimens were printed, varying in thicknesses from 1 mm to 4 mm. According to their
thickness, the subgroups were defined as:
- Subgroup B1, consisting of ten 1 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 1.00±0.1 mm
- Subgroup B2, consisting of ten 2 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 2.00±0.1 mm
- Subgroup B3, consisting of ten 3 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 3.00±0.1 mm
- Subgroup B4, consisting of ten 4 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 4.00±0.1 mm
Figure 19. Varseo Smile Crown Plus bottle used
Figure 20. 1 mm to 4 mm Varseo Smile Crown Plus polished samples

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3. Printed material 2 - Ceramic Crown (Sprintray, Los Angeles, CA, USA) –
(Group C)
Specimens from Ceramic Crown (Sprintray, Los Angeles, CA, USA) material were used in
this group. These specimens were fabricated by 3D-printing from a liquid resin too. Forty
specimens were printed, varying in thicknesses from 1 mm to 4 mm. According to their
thickness, the subgroups were defined as:
- Subgroup C1, consisting of ten 1 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 1.00±0.1 mm
- Subgroup C2, consisting of ten 2 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 2.00±0.1 mm
- Subgroup C3, consisting of ten 3 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 3.00±0.1 mm
- Subgroup C4, consisting of ten 4 mm specimens with the following dimensions:
14.5±0.1 mm x 14.5±0.1 mm x 4.00±0.1 mm
Figure 21. Ceramic Crown bottle used
Figure 22. 1 mm to 4 mm polished Ceramic Crown samples

55
4. Design, printing and slicing for groups B and C:
The specimens were designed using Meshmixer software (Autodesk Inc, San Francisco,
California, USA) according to the desired thickness (1 mm, 2 mm, 3 mm, 4.0 mm) and were
printed with a 3D-printer operated by the corresponding software. For each group, the printer
was be set to print 40 specimens (10 per subgroup), with the following dimensions: 14.5±0.1
mm x 14.5±0.1 mm x 1.00±0.1 mm for subgroups B1 and C1, 14.5±0.1 mm x 14.5±0.1 mm x
2.00±0.1 mm for subgroups B2 and C2, 14.5±0.1 mm x 14.5±0.1 mm x 3.00±0.1 mm for
subgroups B3 and C3 and 14.5±0.1 mm x 14.5±0.1 mm x 4.00±0.1 mm for subgroups B4 and
C4.
Figure 23. Specimens design (1 mm to 4 mm)
Each material was sliced with its corresponding software RayWare (Sprintray, Los Angeles,
CA, USA) and printed with its corresponding printer Sprintray Pro S (Sprintray, Los Angeles,
CA, USA) that works at 405 nm wavelength. The ideal working temperature was in the
temperature range between 18 °C and 28 °C. Before use, the resin had to be homogeneous, so
before the first use, the material was actively shaken for 2 minutes, making sure that when
decanting the resin into the tray, it should be exposed to daylight for as short time as possible.
The resin in the resin tank was mixed beforehand to avoid the separation of its components in
the tank due to its different density and molecular weight. This was even more important
when a transparent layer was visible on the surface of the resin in the tank, meaning that the
material needed mixing prior to use.
STL files of the designed specimens were imported into the RayWare software (Sprintray,
Los Angeles, CA, USA), which carried out all the necessary steps before sending the samples
to print. All the specimens included supports with the following characteristics: the narrowest
supports available evenly distributed through the sample to avoid unsupported areas when
printing.

56
Each thickness group consisted of 10 specimens (n=10). Due to the characteristics and size of
the printing tray for each material, for VarseoSmile Crown (BEGO, Bremen, Germany) all
the specimens for each thickness (n=10) were printed at the same time, while for Ceramic
Crown (Sprintray, Los Angeles, CA, USA) the specimens for each thickness were printed in
two prints (only 5 specimens fitted on each tray).
The specimens to be printed were added to the RayWare (Sprintray, Los Angeles, CA, USA)
virtual tray and manually positioned on the printing tray, with a 10 mm separation between
them, 50 microns layer thickness, 45º orientation, generation of supports and no mesh edit,
label or resize options. At this point, specimens were now sent to the printer.
Figure 24. Sprintray Pro S printer and Sprintray Pro Wash/Dry equipment
Figure 25. Sprintray Pro S printer ready to use

57
The specimen distribution along the printing tray, with its corresponding supports, are
illustrated on the following diagrams:
VarseoSmile Crown Plus (BEGO, Bremen, Germany) - 1 mm:
Figure 26. Varseo Smile Crown Plus 1 mm specimen distribution on printer tray (front view)
Figure 27. Varseo Smile Crown Plus 1 mm specimen distribution on printer tray (side view)

58
VarseoSmile Crown Plus (BEGO, Bremen, Germany) – 2 mm:
Figure 28. Varseo Smile Crown Plus 2 mm specimen distribution on printer tray (front view)
Figure 29. Varseo Smile Crown Plus 2 mm specimen distribution on printer tray (side view)

59
VarseoSmile Crown Plus (BEGO, Bremen, Germany) – 3 mm:
Figure 30. Varseo Smile Crown Plus 3 mm specimen distribution on printer tray (front view)
Figure 31. Varseo Smile Crown Plus 3 mm specimen distribution on printer tray (side view)

60
VarseoSmile Crown Plus (BEGO, Bremen, Germany) – 4 mm:
Figure 32. Varseo Smile Crown Plus 4 mm specimen distribution on printer tray (front view)
Figure 33. Varseo Smile Crown Plus 4 mm specimen distribution on printer tray (side view)

61
Ceramic Crown (Sprintray, Los Angeles, CA, USA) – 1 mm:
Figure 34. Ceramic Crown 1 mm specimen distribution on printer tray (front view)
Figure 35. Ceramic Crown 1 mm specimen distribution on printer tray (side view)

62
Ceramic Crown (Sprintray, Los Angeles, CA, USA) – 2 mm:
Figure 36. Ceramic Crown 2 mm specimen distribution on printer tray (front view)
Figure 37. Ceramic Crown 2 mm specimen distribution on printer tray (side view)

63
Ceramic Crown (Sprintray, Los Angeles, CA, USA) – 3 mm:
Figure 38. Ceramic Crown 3 mm specimen distribution on printer tray (front view)
Figure 39. Ceramic Crown 3 mm specimen distribution on printer tray (side view)

64
Ceramic Crown (Sprintray, Los Angeles, CA, USA) – 4 mm:
Figure 40. Ceramic Crown 4 mm specimen distribution on printer tray (front view)
Figure 41. Ceramic Crown 4 mm specimen distribution on printer tray (side view)

65
5. Post-processing for groups B and C:
Once printing was completed, the samples were post processed, which basically consisted of
2 main steps: washing and curing. Firstly, the building platform was removed from the
printer. During removing the restoration and the following cleaning steps, wearing gloves
(nitrile gloves) and protective goggles was mandatory.
On completion of printing, the printed objects were released from the build platform by
wedging the removal tool –Print Removal Tool (Sprintray, Los Angeles, CA, USA)- under
the specimen’s base and rotating the tool. The printed objects were immersed and cleaned for
20 (Ceramic Crown (Sprintray, Los Angeles, CA, USA)) or 25 minutes (VarseoSmile Crown
(BEGO, Bremen, Germany)) in Isopropyl Alcohol (91 %) using 3D printing material washer
unit Sprintray Pro Wash/Dry (Sprintray, Los Angeles, CA, USA), which uses a patented
Mechanical Jetting Technology with an Automatic 2-stage wash and dry cycle by means of a
precise 10,000 RPM propeller.
Figure 42. Sprintray Pro Wash/Dry equipment
Figure 43. Sprintray Print Removal Tool

66
The printed objects were then removed from the Isopropyl Alcohol (91 %) bath and sprayed
with additional Isopropyl Alcohol (91 %) to fully rinse off any remaining resin residue. If
resin residues still apparent, these were removed using a brush soaked in Isopropyl Alcohol
(91 %). After cleaning, the printed object was finally dried using compressed air. If there still
was liquid resin adhering to the surface of the object, this was completely removed by
spraying again with Isopropyl Alcohol (91 %) and re-drying.
The second step of the post-processing process was curing of the printed samples: to achieve
the desired material properties and biocompatibility, post-curing of the completely dried and
cleaned printed objects was necessary, as the final properties of the printed object depend on
the post-curing process. The printed specimens were placed in a UV-light box - SprintRay
Pro Cure 2 (Sprintray, Los Angeles, CA, USA)- which uses a Patented Light Motion Drive
UV LED system in a scanning chamber for 360° curing with 385 nm light wavelength and 42
individual LEDs. This curing unit needs no pre-heating, as heating is instant: heat is
generated through recovery & recirculation of exhaust heat from UV lights, with a maximum
chamber temperature of 80°C. For VarseoSmile Crown Plus (BEGO, Bremen, Germany) the
curing time was 6:30 min. For Ceramic Crown (Sprintray, Los Angeles, CA, USA) the curing
time was 1:50 min. Finally, the printed and post-processed specimens were allowed to cool
for 3–5 minutes or until the object felt cool.
Figure 44. Printed Varseo Smile Crown Plus 1 mm - 4 mm samples before post-processing (front view)

67
Figure 45. Printed Varseo Smile Crown Plus 1 mm - 4 mm samples before post-processing (side view)
Figure 46. Printed Ceramic Crown 1 mm - 4 mm samples before post-processing (front view)
Figure 47. Printed Ceramic Crown 1 mm - 4 mm samples before post-processing (side view)

68
6. Support removal (groups B and C):
Before polishing, the supports were removed, in 2 steps: firstly, using the Support Snipper
(Sprintray, Los Angeles, CA, USA) to carefully cut the supports. The second part of support
removal process consisted on using a cutting wheel disc - 918B.11.200 HP Medium Flexible
Coated Double Sided Diamond Disc –
(Brasseler USA, Savannah, GA, USA) to
remove the supports on fragile or unreachable
areas for the Support Snipper (Sprintray, Los
Angeles, CA, USA).
Figure 48. Sprintray Support Snipper
7. Polishing & Sample Identification (for all groups):
All specimens were hand-polished with sandpaper, following the full sequence, from the
coarsest to the finest: starting with 600- grit sandpaper up to 1200-grit sandpaper, being each
paper 8 inches. The whole sequence follows:
1. Starting by means of the 600-grit sandpaper CarbiMet® Plain 600 [P1200]
(Buehler Ltd., Lake Bluff, IL, USA).
2. Followed by the 1000-grit sandpaper CarbiMet® Plain 1000 [P2500] (Buehler
Ltd., Lake Bluff, IL, USA).
3. Finally the 1200-grit sandpaper MicroCut® Plain 1200 [P2500] (Buehler Ltd.,
Lake Bluff, IL, USA).
Figure 49. Buehler 600-grit, 1000-grit and 1200-grit polishing sandpaper

69
Polishing time was 60-180 seconds per sample, under running distilled water. Polishing time
was variable because the polishing procedure had to be continued until the desired dimension
and surface characteristics of the specimen was achieved, with a smooth, scratch-less, glossy
final surface.
Following polishing, the dimensions of the specimens were measured with a digital caliper
(Mitutoyo digital caliper; Mitutoyo Corp, Kawasaki, Japan) on 8 different areas (2 areas per
side of the squared specimen). The dimensions should be confirmed to be (width x length x
height) 14.5±0.1 mm x 14.5±0.1 mm x 1.00±0.1 mm for subgroup 1 specimens (A1, B1, C1),
14.5±0.1 mm x 14.5±0.1 mm x 2.00±0.1 mm for subgroup 2 specimens (A2, B2, C2),
14.5±0.1 mm x 14.5±0.1 mm x 3.00±0.1 mm for subgroup 3 specimens (A3, B3, C3) and
14.5±0.1 mm x 14.5±0.1 mm x 4.00±0.1 mm for subgroup 4 specimens (A4, B4, C4).

70
Figure 50. 1 mm to 4 mm samples being measured during calibration process

71
Samples were stored in labelled containers, identified by marking them with a number on one
of the corners with a small carbide bur -1/4 HP round carbide H1.11.005 bur- (Brasseler
USA, Savannah, GA, USA) at 20000 rpm and measured on 8 different spots.
Figure 51. Labelled containers with samples (sample number, material, thickness and size)

72
Sample number Material Thickness group Measured thickness
1 Lava Ultimate 1 mm 1.07 - 1.09 mm
2 Lava Ultimate 1 mm 0.99 - 1.07 mm
3 Lava Ultimate 1 mm 0.99 - 1.06 mm
4 Lava Ultimate 1 mm 0.93 - 1.07 mm
5 Lava Ultimate 1 mm 1.05 - 1.07 mm
6 Lava Ultimate 1 mm 0.99 - 1.10 mm
7 Lava Ultimate 1 mm 1.04 - 1.07 mm
8 Lava Ultimate 1 mm 1.03 - 1.05 mm
9 Lava Ultimate 1 mm 0.95 - 1.08 mm
10 Lava Ultimate 1 mm 1.01 - 1.07 mm
11 Lava Ultimate 2 mm 2.00 - 2.09 mm
12 Lava Ultimate 2 mm 2.04 - 2.08 mm
13 Lava Ultimate 2 mm 1.90 - 2.04 mm
14 Lava Ultimate 2 mm 1.92 - 2.03 mm
15 Lava Ultimate 2 mm 1.97 - 2.04 mm
16 Lava Ultimate 2 mm 1.91 - 2.06 mm
17 Lava Ultimate 2 mm 1.97 - 2.01 mm
18 Lava Ultimate 2 mm 1.93 - 2.10 mm
19 Lava Ultimate 2 mm 1.91 - 2.05 mm
20 Lava Ultimate 2 mm 1.90 - 2.06 mm
21 Lava Ultimate 3 mm 2.90 - 3.10 mm
22 Lava Ultimate 3 mm 2.92 - 3.10 mm
23 Lava Ultimate 3 mm 2.96 - 3.06 mm
24 Lava Ultimate 3 mm 2.93 - 3.10 mm
25 Lava Ultimate 3 mm 2.99 - 3.09 mm
26 Lava Ultimate 3 mm 2.96 - 3.04 mm
27 Lava Ultimate 3 mm 2.90 - 2.95 mm
28 Lava Ultimate 3 mm 3.02 - 3.07 mm
29 Lava Ultimate 3 mm 2.99 - 3.07 mm

73
30 Lava Ultimate 3 mm 2.98 - 3.10 mm
31 Lava Ultimate 4 mm 3.90 - 3.96 mm
32 Lava Ultimate 4 mm 3.97 - 4.10 mm
33 Lava Ultimate 4 mm 3.97 - 4.02 mm
34 Lava Ultimate 4 mm 3.92 - 3.95 mm
35 Lava Ultimate 4 mm 3.96 - 4.01 mm
36 Lava Ultimate 4 mm 3.92 - 4.05 mm
37 Lava Ultimate 4 mm 4.05 - 4.10 mm
38 Lava Ultimate 4 mm 3.96 - 4.08 mm
39 Lava Ultimate 4 mm 4.02 - 4.10 mm
40 Lava Ultimate 4 mm 3.90 - 4.04 mm
41 VarseoSmile Crown Plus 1 mm 1.01 - 1.10 mm
42 VarseoSmile Crown Plus 1 mm 0.97 - 1.06 mm
43 VarseoSmile Crown Plus 1 mm 0.96 - 1.07 mm
44 VarseoSmile Crown Plus 1 mm 0.96 - 1.10 mm
45 VarseoSmile Crown Plus 1 mm 0.95 - 1.10 mm
46 VarseoSmile Crown Plus 1 mm 0.96 - 1.10 mm
47 VarseoSmile Crown Plus 1 mm 1.00 - 1.09 mm
48 VarseoSmile Crown Plus 1 mm 0.99 - 1.05 mm
49 VarseoSmile Crown Plus 1 mm 0.98 - 1.04 mm
50 VarseoSmile Crown Plus 1 mm 0.96 - 1.09 mm
51 VarseoSmile Crown Plus 2 mm 1.90 - 2.01 mm
52 VarseoSmile Crown Plus 2 mm 1.94 - 1.98 mm
53 VarseoSmile Crown Plus 2 mm 2.04 - 2.10 mm
54 VarseoSmile Crown Plus 2 mm 1.98 - 2.08 mm
55 VarseoSmile Crown Plus 2 mm 1.91 - 1.96 mm
56 VarseoSmile Crown Plus 2 mm 1.91 - 2 mm
57 VarseoSmile Crown Plus 2 mm 2.00 - 2.08 mm
58 VarseoSmile Crown Plus 2 mm 2.07 - 2.10 mm
59 VarseoSmile Crown Plus 2 mm 1.97 - 2.05 mm
60 VarseoSmile Crown Plus 2 mm 1.96 - 2.02 mm
61 VarseoSmile Crown Plus 3 mm 2.91 - 3.09 mm

74
62 VarseoSmile Crown Plus 3 mm 2.91 - 3.10 mm
63 VarseoSmile Crown Plus 3 mm 2.91 - 3.02 mm
64 VarseoSmile Crown Plus 3 mm 2.96 - 3.06 mm
65 VarseoSmile Crown Plus 3 mm 2.96 - 3.10 mm
66 VarseoSmile Crown Plus 3 mm 3.00 - 3.08 mm
67 VarseoSmile Crown Plus 3 mm 2.97 - 3.08 mm
68 VarseoSmile Crown Plus 3 mm 2.91 - 3.10 mm
69 VarseoSmile Crown Plus 3 mm 2.99 - 3.08 mm
70 VarseoSmile Crown Plus 3 mm 3.04 - 3.10 mm
71 VarseoSmile Crown Plus 4 mm 3.98 - 4.04 mm
72 VarseoSmile Crown Plus 4 mm 3.96 - 4.05 mm
73 VarseoSmile Crown Plus 4 mm 3.97 - 4.05 mm
74 VarseoSmile Crown Plus 4 mm 3.91 - 4.07 mm
75 VarseoSmile Crown Plus 4 mm 3.91 - 4.06 mm
76 VarseoSmile Crown Plus 4 mm 3.95 - 4.05 mm
77 VarseoSmile Crown Plus 4 mm 3.99 - 4.06 mm
78 VarseoSmile Crown Plus 4 mm 4.02 - 4.09 mm
79 VarseoSmile Crown Plus 4 mm 3.97 - 4.10 mm
80 VarseoSmile Crown Plus 4 mm 3.98 - 4.08 mm
81 Ceramic Crown 1 mm 0.92 - 1.03 mm
82 Ceramic Crown 1 mm 1.01 - 1.10 mm
83 Ceramic Crown 1 mm 1.04 - 1.10 mm
84 Ceramic Crown 1 mm 0.94 - 1.08 mm
85 Ceramic Crown 1 mm 0.91 - 0.98 mm
86 Ceramic Crown 1 mm 0.95 - 1.10 mm
87 Ceramic Crown 1 mm 0.93 - 1.09 mm
88 Ceramic Crown 1 mm 0.97 - 1.02 mm
89 Ceramic Crown 1 mm 1.00 - 1.09 mm
90 Ceramic Crown 1 mm 0.99 - 1.05 mm
91 Ceramic Crown 2 mm 1.95 - 2.02 mm
92 Ceramic Crown 2 mm 2.03 - 2.09 mm
93 Ceramic Crown 2 mm 1.99 - 2.04 mm

75
94 Ceramic Crown 2 mm 1.93 - 1.98 mm
95 Ceramic Crown 2 mm 2.02 - 2.10 mm
96 Ceramic Crown 2 mm 2.02 - 2.10 mm
97 Ceramic Crown 2 mm 2.02 - 2.07 mm
98 Ceramic Crown 2 mm 1.91 - 2.03 mm
99 Ceramic Crown 2 mm 1.94 - 2.08 mm
100 Ceramic Crown 2 mm 2.01 - 2.05 mm
101 Ceramic Crown 3 mm 2.90 - 2.97 mm
102 Ceramic Crown 3 mm 2.98 - 3.08 mm
103 Ceramic Crown 3 mm 2.90 - 2.99 mm
104 Ceramic Crown 3 mm 2.95 - 3.08 mm
105 Ceramic Crown 3 mm 3.07 - 3.09 mm
106 Ceramic Crown 3 mm 2.92 - 3.09 mm
107 Ceramic Crown 3 mm 3.02 - 3.10 mm
108 Ceramic Crown 3 mm 2.98 - 3.06 mm
109 Ceramic Crown 3 mm 2.98 - 3.08 mm
110 Ceramic Crown 3 mm 3.03 - 3.09 mm
111 Ceramic Crown 4 mm 3.99 - 4.08 mm
112 Ceramic Crown 4 mm 3.96 - 4.07 mm
113 Ceramic Crown 4 mm 3.96 - 4.09 mm
114 Ceramic Crown 4 mm 3.98 - 4.10 mm
115 Ceramic Crown 4 mm 3.91 - 4.08 mm
116 Ceramic Crown 4 mm 3.95 - 4.09 mm
117 Ceramic Crown 4 mm 4.03 - 4.10 mm
118 Ceramic Crown 4 mm 3.94 - 4.09 mm
119 Ceramic Crown 4 mm 3.98 - 4.10 mm
120 Ceramic Crown 4 mm 4.02 - 4.08 mm
Table 3. Identification and measurements for each sample

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8. Testing (Transmittance Analysis):
To measure the light transmittance of the prepared samples, these were placed at the entrance
port of a PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer -equipped with a 150mm
integrating sphere- (Perkin Elmer, Waltham, MA, USA).
Figure 52. Set up used: computer to register data and PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer
Figure 53. PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer used

77
Figure 54. PerkinElmer Lambda 950 UV-Vis-Nir Spectrophotometer used (open)
Figure 55. Diagram indicating. most important parts of spectrophotometer PerkinElmer Lambda 950 UV-Vis-Nir

78
Figure 56. Integrating sphere for spectrophotometer Lambda 950 UV-Vis-Nir (top view)- left image
Figure 57. Integrating sphere for spectrophotometer Lambda 950 UV-Vis-Nir (side view)- right image
Figure 58. Solid sample holder & sample positioning for spectrophotometer Lambda 950 UV-Vis-Nir (top view)- left image
Figure 59. Solid sample holder & sample positioning for spectrophotometer Lambda 950 UV-Vis-Nir (side view)- right
image

79
A solid sample holder (Perkin Elmer, Waltham, MA, USA) was used in order to position the
sample in the same, repeatable position.
Figure 60. Solid sample holder with no sample (front and side views)
Figure 61. Solid sample holder holding sample (front and side views)
The total transmittance was measured for each material in transmittance % values (%T) and
the results were automatically reported by the software: transmittance was reported as
percentage values between 0% (totally opaque) and 100% (totally transparent) for violet
(400-430 nm) and blue light (430-480 nm). The software used for data acquisition and export
was UV WinLab (Perkin Elmer, Waltham, MA, USA) and the software used for data export
was UV WinLab Data Processer and Viewer (DPV) (Perkin Elmer, Waltham, MA, USA).

80
The analysis of light transmittance was performed on the wavelengths corresponding to the
VALO Cordless Curing Light (Ultradent, South Jordan, UT, USA), which has a utilizable
wavelength range of 385 – 515 nm. and 395 – 415nm, with the peak wavelengths at 440 –
480nm. The measurements were be conducted taking into account the wavelength spectral
absorption of the photoinitiators used in dentistry, mainly: Camphoroquinone (CQ), 9,10-
Phenanthrenequinone (PQ), 1-Phenyl-1,2-Propanedione (PPD), Lucirin TPO (2,4,6-
trimethylbenzoyl-diphenylphosphine oxide) and Ivocerin (Ivocerin-dibenzoyl germanium). It
is important to consider the wavelength peak absorption for each photoinitiator, being 468 nm
(425 – 495 nm absorption wavelength spectra) for Camphoroquinone (CQ), 420 nm (360 –
510 nm absorption wavelength spectra) for 9,10-Phenanthrenequinone (PQ), 410 nm (390 –
460 nm absorption wavelength spectra) for 1-Phenyl-1,2-Propanedione (PPD), 400 nm (380 -
425 nm absorption wavelength spectra) for Lucirin TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and 418 nm (390 - 445 nm absorption wavelength spectra) for
Ivocerin (Ivocerin-dibenzoyl germanium). For this reason, transmittance analysis was
conducted in two different wavelengths in the visible light spectra: violet light spectra (λ
from 400–430), representing the spectrum of violet light and blue light spectra (λ from 430–
480), representing the blue light emission spectra. Transmittance was measured for each
sample 3 times. The mean of the 3 measurements was considered.
The first step was introducing and labelling correctly all the data into the UV WinLab (Perkin
Elmer, Waltham, MA, USA) software. A total of 120 samples were tested, three
measurements sample, resulting in 360 measurements. See appendix for reference tables on
data naming and labelling. On the “samples” section by the “samples ID” tab, each sample
was labelled and identified on the “sample ID” column according to sample number, material
name, thickness, sample number and measurement number. On the “description” column,
detailed information about each sample was introduced (material name and thickness, sample
number, measurement number).

81
Figure 62. Screenshot of parameters introduced at UV Winlab software
When all the data was introduced, labelled, and described, the first sample was introduced on
the sample holder, researcher pressed “start” button and the spectrophotometer started
measuring the transmittance (%T) of the first sample introduced. When finished measuring
%T of the first sample, the software asked the researcher to introduce the following sample
(according to samples introduced on the “sample ID” table) until all samples were tested.
When the spectrophotometer finished testing all the samples, it was time to check the results
of the tested samples on the “graphs” column, and finally export the data by means of the UV
WinLab Data Processer and Viewer software (Perkin Elmer, Waltham, MA, USA).

82
9. Data Management and Statistical Analysis:
All the data was entered into a digital sheet (Excel; Microsoft Corp, Redmond, WA, USA)
and transmittance of each specimen was determined as percentage values between 0% (totally
opaque) and 100% (totally transparent), to measure the light transmittance according to the
specimen thickness (1 mm to 4 mm) of the different materials (printed and milled). The
independent variables were “material used” and “material thickness” and the dependent
variable was “light transmittance (%)”.
Several assumptions need to be fulfilled to apply a statistical test, which are normality,
interval data of the dependent variable, homoscedasticity, no multicollinearity, and equal
sample size.
Kolmogorov Smirnov test was applied to test the normality of our data. As the data didn’t
follow a normal distribution, a non-parametric test was applied to determine the clinical
significance and the acceptance or rejection of the null hypothesis (Kruskal-Wallis test).
Kruskal-Wallis test was applied and assessed at the 95% confidence level (α=.05) to
determine statistically significant differences among different materials and different
thicknesses.
Levene’s test was used to evaluate the homogeneity of the data.
A post-hoc multiple comparisons was performed to determine the statistical different between
different materials and different thicknesses using the Mann-Whitney test at (α=.05).
Significance values have been adjusted for Bonferroni correction (adj.Sig).

83
Chapter Four: Results
1. Descriptive Analysis of Transmittance %:
A summary of the descriptive statistical analysis of the results showing the transmittance of
materials tested (Lava Ultimate, Varseo Smile Crown Plus and Ceramic Crown) at the
wavelengths corresponding to the photoinitiators interested in is shown as follows.
Total of n=120 samples were tested, n=40 from Lava Ultimate, n=40 from Varseo Smile and
n=40 from Ceramic Crown. Each sample was tested for transmittance at the following
wavelengths: 468nm (peak absorbance value for CQ), 420nm (peak absorbance value for PQ),
418nm (peak absorbance value for Ivocerin), 410nm (peak absorbance value for PPD) and
400nm (peak absorbance value for Lucirin TPO). A summary of the sample frequency used in
the study can be observed on Table 4.
Table 5 and Figure 63 show a summary of all the descriptive statistical analysis of the results
showing the transmittance of materials tested (Lava Ultimate, Varseo Smile and Ceramic
Crown) at the thicknesses (1 mm, 2 mm, 3 mm and 4 mm) studied and at the wavelengths
corresponding to the photoinitiators (468 nm, 420 nm, 418 nm, 410 nm, 400 nm) interested in
(mean, 95% confidence interval, mean, variance, standard deviation, maximum, minimum).
Overall, the highest mean transmittance value was seen in Lava Ultimate 1 mm when testing
at 468nm (peak absorption value for CQ) transmittance % = 0.42.
The lowest mean transmittance value was transmittance % = 0.00 and was observed in:
- Varseo Smile 3 mm at 418 nm (peak absorption value for Ivocerin), 410 nm (peak
absorption value for PPD), and 400 nm (peak absorption value for Lucirin TPO)
- Varseo Smile 4 mm at 420 nm (peak absorption value for PQ), 418 nm peak
absorption value for Ivocerin), 410 nm (peak absorption value for PPD), and 400 nm
(peak absorption value for Lucirin TPO)
- Ceramic Crown 1 mm at 400 nm (peak absorption value for Lucirin TPO)
- Ceramic Crown 2 mm (at 410 nm (peak absorption value for PPD), and 400 nm (peak
absorption value for Lucirin TPO).
- Ceramic Crown 3mm at 410 nm (peak absorption value for PPD) and 400 nm (peak
absorption value for Lucirin TPO).

84
Table 4. Descriptive statistical analysis of results
Photoinitiator Material
Mean (T% as decimal)
Mean
(T% as
decimal)
Standard Deviation
Thickness
(mm)
Mean
value Mean value
95% confidence interval
Lower Upper Std Dev Min Max
CQ
(468 nm)
Lava Ultimate
1 0.41
0.2034 0.160 0.246 0.170 0.135 0.056 0.440 2 0.22
3 0.12
4 0.06
Varseo Smile
1 0.32
0.151 0.117 0.185 0.120 0.107 0.040 0.340 2 0.16
3 0.08
4 0.08
Ceramic
Crown
1 0.29
0.126 0.938 0.158 0.090 0.100 0.020 0.30 2 0.13
3 0.06
4 0.03
PQ
(420 nm)
Lava Ultimate
1 0.029
0.135 0.098 0.173 0.100 0.117 0.020 0.350 2 0.14
3 0.06
4 0.02
Varseo Smile
1 0.12
0.039 0.248 0.054 0.020 0.047 0.000 0.130 2 0.03
3 0.01
4 0.00
Ceramic
Crown
1 0.20
0.069 0.442 0.942 0.040 0.782 0.000 0.213 2 0.05
3 0.02
4 0.01
Ivocerin
(418 nm)
Lava Ultimate
1 0.32
0.132 0.095 0.169 0.090 0.116 0.020 0.350 2 0.13
3 0.06
4 0.02
Varseo Smile
1 0.09
0.031 0.019 0.042 0.016 0.037 0.000 0.106 2 0.02
3 0.01
4 0.00
Ceramic
Crown
1 0.18
0.060 0.036 0.083 0.033 0.072 0.000 0.210 2 0.04
3 0.01
4 0.01
PPD
(410 nm)
Lava Ultimate
1 0.29
0.118 0.084 0.152 0.080 0.107 0.010 0.320 2 0.12
3 0.05
4 0.02
Varseo Smile
1 0.03
0.011 0.007 0.014 0.010 0.010 0.000 0.036 2 0.01
3 0.01
4 0.00
Ceramic
Crown
1 0.08
0.022 0.010 0.034 0.003 0.038 0.000 0.136 2 0.01
3 0.00
4 0.00
Lucirin TPO
(410 nm)
Lava Ultimate
1 0.24
0.091 0.095 0.169 0.090 0.116 0.020 0.350 2 0.08
3 0.03
4 0.01
Varseo Smile
1 0.02
0.008 0.019 0.042 0.016 0.037 0.000 0.106 2 0.01
3 0.00
4 0.00
Ceramic
Crown
1 0.02
0.006 0.062 0.120 0.058 0.090 0.010 0.266 2 0.00
3 0.00
4 0.00

85
Figure 63. Transmittance of light for all materials, thickness and photoinitiators (wavelengths

86
2. Data Normality Analysis and Equality of Variances:
The Kolmogorov-Smirnov test was used to test the normality of the transmittance values.
The test revealed that the data were not normally distributed, as the transmittance values for
all of the groups deviated from the normality assumption (p<0.05)
The significance level is .050
* Not normally distributed groups. (p=<0.05)
Table 5. Kolmogorov-Smirnov test for non-transformed data
Data was transformed via logarithm (log10), exponential (Exp), logarithm (ln) and square
root (SqRt) to check the normality the transmittance values. However, Kolmogorov-Smirnov
test revealed that, for all the transformations, the data was not normally distributed, as the
transmittance values for all of the transformed data deviated from the normality assumption
(p<0.05)
Table 6. Kolmogorov-Smirnov test for transformed data
Tests of Normality
Material
Kolmogorov-Smirnova Shapiro-Wilk
Statistic df Sig. Statistic df Sig.
CQ (468nm) Lava Ultimate .206 40 <.001 .830 40 <.001
Varseo Smile .217 40 <.001 .827 40 <.001
Ceramic Crown .244 40 <.001 .798 40 <.001
PQ (420nm) Lava Ultimate .225 40 <.001 .799 40 <.001
Varseo Smile .333 40 <.001 .726 40 <.001
Ceramic Crown .297 40 <.001 .740 40 <.001
Ivocerin (418nm) Lava Ultimate .235 40 <.001 .794 40 <.001
Varseo Smile .367 40 <.001 .720 40 <.001
Ceramic Crown .306 40 <.001 .729 40 <.001
PPD (410nm) Lava Ultimate .239 40 <.001 .788 40 <.001
Varseo Smile .214 40 <.001 .879 40 <.001
Ceramic Crown .351 40 <.001 .643 40 <.001
Lucirin TPO
(400nm)
Lava Ultimate .271 40 <.001 .762 40 <.001
Varseo Smile .174 40 .004 .872 40 <.001
Ceramic Crown .349 40 <.001 .628 40 <.001

87
Levene’s test was used to evaluate the homogeneity of the data and it showed that the
variances are homogeneous for CQ (468nm) groups but not homogeneous (p<0.001) for the
rest of the groups (Table 7).
Table 7. Levene's test (equality of variances)
Parametric tests such as analysis of variance (ANOVA) have four requirements including
equal sample size, independent variable, normal distribution, and homogeneity of variance.
The first two (equal sample size and independent variable) were met. However, normal
distribution and homogeneity of variance were not met. For these reasons, the statistical
analysis applied a non-parametric test, in this case Kruskal Wallis H-test, for all of the groups
and comparisons.
Pairwise comparison (Mann-Whitney U-test). Type I errors. Therefore, Bonferroni
correction. Significance values have been adjusted for Bonferroni correction (adj.Sig).
Test of Homogeneity of Variance
Levene
Statistic df1 df2 Sig.
CQ (468nm) Based on Mean 2.517 2 117 .085
Based on Mean 2.035 2 117 .135
Based on Mean and with adjusted
df
2.035 2 113.356 .135
Based on trimmed mean 2.574 2 117 .081
PQ (420nm) Based on Mean 13.379 2 117 <.001
Based on Mean 10.122 2 117 <.001
Based on Mean and with adjusted
df
10.122 2 93.538 <.001
Based on trimmed mean 12.694 2 117 <.001
Ivocerin (418nm) Based on Mean 18.613 2 117 <.001
Based on Mean 12.711 2 117 <.001
Based on Mean and with adjusted
df
12.711 2 83.219 <.001
Based on trimmed mean 17.183 2 117 <.001
PPD (410nm) Based on Mean 45.590 2 117 <.001
Based on Mean 28.585 2 117 <.001
Based on Mean and with adjusted
df
28.585 2 56.804 <.001
Based on trimmed mean 40.941 2 117 <.001
Lucirin TPO
(400nm)
Based on Mean 66.428 2 117 <.001
Based on Mean 34.626 2 117 <.001
Based on Mean and with adjusted
df
34.626 2 41.915 <.001
Based on trimmed mean 55.153 2 117 <.001

88
3. Statistical analysis and comparisons between materials:
When analyzing the transmittance of light by materials, at all thicknesses and
wavelengths, (Figure 64) it can be observed that light transmittance is highest for Lava
Ultimate, followed by Ceramic Crown and finally Varseo Smile.
Figure 64. Transmittance of light by materials, at all thicknesses and wavelengths
The differences between the materials are statistically significant for Lava Ultimate-Varseo
Smile and Lava Ultimate-Ceramic Crown but not for Varseo Smile-Ceramic Crown.
If looking in a more detailed way, at the transmittance of light by materials and
thicknesses (all wavelengths), (Figure 65) it can be observed that light transmittance is
highest for Lava Ultimate for all thicknesses, followed by Ceramic Crown and finally Varseo
Smile (for 1 mm and 2 mm) but inverted for 3 mm and 4 mm: light transmittance is higher
for Varseo Smile rather than Ceramic Crown.
The differences between the materials are statistically significant for Lava Ultimate-Varseo
Smile and Lava Ultimate-Ceramic Crown at all thicknesses, but not significant for Varseo
Smile-Ceramic Crown at any thickness.

89
Figure 65. Transmittance of light by materials and thicknesses (all wavelengths)
If looking in a more detailed way, at the transmittance of light by materials and
wavelengths (all thicknesses), (Figure 66) it can be observed that light transmittance is
highest for Lava Ultimate for all wavelengths, followed by Varseo Smile and finally Ceramic
crown (for CQ(468 nm) and TPO (400nm)) but inverted for PQ (420nm), Ivocerin (418nm)
and PPD (410nm): light transmittance is higher for Ceramic Crown rather than Varseo Smile.
Figure 66. Transmittance of light by materials and wavelengths (all thicknesses)
The differences between the wavelengths are statistically significant for some of the groups
not for others. Mainly, those comparisons that involve Lava Ultimate.
A more detailed comparison of the transmittance of light by materials and wavelengths,
per thickness is described in the following pages:

90
3.1 Material comparisons (by wavelength) – thickness = 1 mm.
3.1.1 Camphorquinone (CQ) [468nm]
For the materials tested, considering thickness = 1 mm, transmittance at 468 nm (CQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 8, Figure 67, Figure 68, Lava Ultimate had the highest transmittance
(mean = 0.41), followed by Varseo Smile (mean = 0.32) and Ceramic Crown (mean = 0.29).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.033). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.033). (Table 8 and Figure 68)
Figure 67. (left) Kruskal-Wallis test boxplot of materials tested at 1 mm for CQ (468 nm)
Figure 68. (right) Group-wise comparisons of materials tested at 1 mm for CQ (468 nm)
Table 8. Group-wise comparisons of materials tested at 1 mm for CQ (468nm
Pairwise Comparisons of Materials for CQ (468nm) at 1 mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 10.000 3.926 2.547 .011 .033*
Ceramic Crown-Lava Ultimate 20.000 3.926 5.094 <.001 .000*
Varseo Smile-Lava Ultimate 10.000 3.926 2.547 .011 .033*
0.32
0.29
0.41

91
3.1.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For the materials tested, considering thickness = 1 mm, transmittance at 420 nm (PQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001)
As shown in Table 9, Figure 69, Figure 70, Lava Ultimate had the highest transmittance
(mean = 0.32), Ceramic Crown (mean = 0.20) and Varseo Smile (mean = 0.12).
Pairwise comparison was significantly different from Ceramic crown (p=0.033) and from
Varseo Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown also differed
significantly from each other (p=0.033). (Table 9 and Figure 70)
Figure 69. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for PQ (420 nm)
Figure 70. (right) Group-wise comparisons of materials tested at 1mm for PQ (420 nm)
Pairwise Comparisons of Materials for PQ (420nm) at 1 mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -10.000 3.928 -2.546 .011 .033*
Varseo Smile-Lava Ultimate 20.000 3.928 5.092 <.001 .000*
Ceramic Crown-Lava Ultimate 10.000 3.928 2.546 .011 .033*
Table 9. Group-wise comparisons of materials tested at 1mm for PQ (420 nm)
0.12
0.20
0.32

92
3.1.3 Ivocerin [418nm]
For the materials tested, considering thickness = 1 mm, transmittance at 418 nm (Ivocerin)
was significantly different between some of the materials, according to the Kruskal-Wallis
test (p<0.001).
As shown in Table 10, Figure 71, Figure 72, Lava Ultimate had the highest transmittance
(mean = 0.32), followed by Ceramic Crown (mean = 0.18) and Varseo Smile (mean = 0.09).
Pairwise comparison was significantly different from Ceramic Crown (p=0.033) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.033). (Table 8 and Figure 68)
Figure 71. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for Ivocerin (418 nm)
Figure 72. (right) Group-wise comparisons of materials tested at 1mm for Ivocerin (418 nm)
Pairwise Comparisons of Materials for Ivocerin (418 nm) at 1 mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -10.000 3.926 -2.547 .011 .033*
Varseo Smile-Lava Ultimate 20.000 3.926 5.094 <.001 .000*
Ceramic Crown-Lava Ultimate 10.000 3.926 2.547 .011 .033*
Table 10. Group-wise comparisons of materials tested at 1mm for Ivocerin (418 nm)
0.09
0.18
0.32

93
3.1.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For the materials tested, considering thickness = 1 mm, transmittance at 410 nm (PPD) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 11, Figure 73, Figure 74, Lava Ultimate had the highest transmittance
(mean = 0.29), followed by Ceramic Crown (mean = 0.08) and Varseo Smile (mean = 0.03).
Pairwise comparison was significantly different from Ceramic Crown (p=0.030) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.037). (Table 11 and Figure 74)
Figure 73. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for PPD (410 nm)
Figure 74. (right) Group-wise comparisons of materials tested at 1mm for PPD (410 nm)
Pairwise Comparisons of Materials for PPD (410nm) at 1mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -9.800 3.917 -2.502 .012 .037*
Varseo Smile-Lava Ultimate 19.900 3.917 5.080 <.001 .000*
Ceramic Crown-Lava Ultimate 10.100 3.917 2.578 .010 .030*
Table 11. Group-wise comparisons of materials tested at 1mm for PPD (410 nm)
0.03
0.08
0.29

94
3.1.5 Lucirin TPO [400nm]
For the materials tested, considering thickness = 1 mm, transmittance at 400 nm (Lucirin
TPO) was significantly different between some of the materials, according to the KruskalWallis test (p<0.001).
As shown in Table 12, Figure 75, Figure 76, Lava Ultimate had the highest transmittance
(mean = 0.24), followed by Varseo Smile (mean = 0.02) and Ceramic Crown (0.02).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.001). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=1.000). (Table 12 and Figure 76)
Figure 75. (left) Kruskal-Wallis test boxplot of materials tested at 1mm for Lucirin TPO (400nm)
Figure 76. (right) Group-wise comparisons of materials tested at 1mm for Lucirin TPO (400nm)
Table 12. Group-wise comparisons of materials tested at 1mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for Lucirin TPO (400nm) at 1mm
Sample 1-Sample 2 Test Statistic Std. Error
Std. Test
Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile .500 3.919 .128 .898 1.000
Ceramic Crown-Lava Ultimate 15.250 3.919 3.891 <.001 .000*
Varseo Smile-Lava Ultimate 14.750 3.919 3.764 <.001 .001*
0.02 0.02
0.24

95
3.1.6 Summary
When comaping the transmittance between the different materials (Lava Ultimate, Varseo
Smile and Ceramic Crown) at 1 mm thicknesses, the following trends were found:
- For CQ (468 nm), transmittance % values for Lava Ultimate > Varseo Smile >
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000), Lava Ultimate-Varseo Smile (p = 0.033) and
Varseo Smile – Ceramic Crown (p = 0.033).
- For PQ (420 nm), transmittance % values for Lava Ultimate > Ceramic Crown >
Varseo Smile. Statistically significant differences were found between Lava Ultimate
- Ceramic Crown (p = 0.033), Lava Ultimate-Varseo Smile (p = 0.000) and Varseo
Smile – Ceramic Crown (p = 0.033).
- For Ivocerin (418 nm), transmittance % values for Lava Ultimate > Ceramic Crown
> Varseo Smile. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.033), Lava Ultimate-Varseo Smile (p = 0.000) and
Varseo Smile – Ceramic Crown (p = 0.033).
- For PPD (410 nm), transmittance % values for Lava Ultimate > Ceramic Crown >
Varseo Smile. Statistically significant differences were found between Lava Ultimate
- Ceramic Crown (p = 0.030), Lava Ultimate-Varseo Smile (p = 0.000) and Varseo
Smile – Ceramic Crown (p = 0.037).
- For Lucirin TPO (400 nm), transmittance % values for Lava Ultimate > Ceramic
Crown ≥ Varseo Smile. Statistically significant differences were found between Lava
Ultimate-Ceramic Crown (p = 0.000) and between Lava Ultimate-Varseo Smile (p =
0.001).

96
3.2 Material comparisons (by wavelength) – thickness = 2 mm.
3.2.1 Camphorquinone (CQ) [468 nm]
For the materials tested, considering thickness = 2 mm, transmittance at 468 nm (CQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 13, Figure 77, Figure 78, Lava Ultimate had the highest transmittance
(mean = 0.22), followed by Varseo Smile (mean = 0.16) and Ceramic Crown (0.13).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.032). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.032). (Table 13 and Figure 78)
Figure 77. (left) Kruskal-Wallis test boxplot of materials tested at 2mm for Lucirin TPO (400nm)
Figure 78. (right) Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for CQ (468nm) at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 10.000 3.912 2.557 .011 .032*
Ceramic Crown-Lava Ultimate 20.000 3.912 5.113 <.001 .000*
Varseo Smile-Lava Ultimate 10.000 3.912 2.557 .011 .032*
Table 13. Group-wise comparisons of materials tested at 2 mm for CQ (468nm)
0.16
0.13
0.22

97
3.2.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For the materials tested, considering thickness = 2 mm, transmittance at 420 nm (PQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 14, Figure 79, Figure 80, Lava Ultimate had the highest transmittance
(mean = 0.14), followed by Ceramic Crown (0.05) and Varseo Smile (mean = 0.03).
Pairwise comparison was significantly different from Ceramic crown (p=0.030) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.030). (Table 14 and Figure 80)
Figure 79. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for PQ (420 nm)
Figure 80. (right) Group-wise comparisons of materials tested at 2 mm for PQ (420 nm)
Pairwise Comparisons of Materials for PQ (420nm) at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -10.000 3.890 -2.571 .010 .030*
Varseo Smile-Lava Ultimate 20.000 3.890 5.142 <.001 .000*
Ceramic Crown-Lava Ultimate 10.000 3.890 2.571 .010 .030*
Table 14. Group-wise comparisons of materials tested at 2 mm for PQ (420 nm)
0.03
0.05
0.14

98
3.2.3 Ivocerin [418nm]
For the materials tested, considering thickness = 2 mm, transmittance at 418 nm (Ivocerin)
was significantly different between some of the materials, according to the Kruskal-Wallis
test (p<0.001).
As shown in Table 15, Figure 81, Figure 82, Lava Ultimate had the highest transmittance
(mean = 0.13), followed by Ceramic Crown (0.04) and Varseo Smile (mean = 0.02).
Pairwise comparison was significantly different from Ceramic crown (p=0.029) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.029). (Table 15 and Figure 82)
Figure 81. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for Ivocerin (418 nm)
Figure 82. (right) Group-wise comparisons of materials tested at 2 mm for Ivocerin (418 nm)
Pairwise Comparisons of Materials for Ivocerin (418nm) at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -10.000 3.864 -2.588 .010 .029*
Varseo Smile-Lava Ultimate 20.000 3.864 5.176 <.001 .000*
Ceramic Crown-Lava Ultimate 10.000 3.864 2.588 .010 .029*
Table 15. Group-wise comparisons of materials tested at 2 mm for Ivocerin (418 nm)
0.02 0.04
0.13

99
3.2.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For the materials tested, considering thickness = 2 mm, transmittance at 410 nm (PPD) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 16, Figure 83, Figure 84, Lava Ultimate had the highest transmittance
(mean = 0.12), followed by Varseo Smile (mean = 0.01) and Ceramic Crown (0.01).
Pairwise comparison was significantly different from Ceramic Crown (p=0.000) and Varseo
Smile (p=0.001). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.029). (Table 16 and Figure 84)
Figure 83. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for PPD (410 nm)
Figure 84. (right) Group-wise comparisons of materials tested at 2 mm for PPD (410 nm)
Pairwise Comparisons of Materials for PPD (410nm) at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 2.200 3.852 .571 .568 1.000
Ceramic Crown-Lava Ultimate 16.100 3.852 4.180 <.001 .000*
Varseo Smile-Lava Ultimate 13.900 3.852 3.609 <.001 .001*
Table 16. Group-wise comparisons of materials tested at 2 mm for PPD (410 nm)
0.01 0.01
0.12

100
3.2.5 Lucirin TPO [400nm]
For the materials tested, considering thickness = 2 mm, transmittance at 400 nm (Lucirin
TPO) was significantly different between some of the materials, according to the KruskalWallis test (p<0.001).
As shown in Table 17, Figure 85, Figure 86, Lava Ultimate had the highest transmittance
(mean = 0.08), followed by Varseo Smile (mean = 0.01) and Ceramic Crown (0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.007). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.258). (Table 17 and Figure 86)
Figure 85. (left) Kruskal-Wallis test boxplot of materials tested at 2 mm for Lucirin TPO (400nm)
Figure 86. (right) Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for Lucirin TPO (400nm) at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 6.600 3.842 1.718 .086 .258
Ceramic Crown-Lava Ultimate 18.300 3.842 4.763 <.001 .000*
Varseo Smile-Lava Ultimate 11.700 3.842 3.045 .002 .007*
Table 17. Group-wise comparisons of materials tested at 2 mm for Lucirin TPO (400nm)
0.01 0.00
0.08

101
3.2.6 Summary
When comparing the transmittance between the different materials (Lava Ultimate, Varseo
Smile and Ceramic Crown) at 2 mm thicknesses, the following trends were found:
- For CQ (468 nm), transmittance % values for Lava Ultimate > Varseo Smile >
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000), Lava Ultimate-Varseo Smile (p = 0.032) and
Varseo Smile – Ceramic Crown (p = 0.032).
- For PQ (420 nm), transmittance % values for Lava Ultimate > Ceramic Crown >
Varseo Smile. Statistically significant differences were found between Lava Ultimate
- Ceramic Crown (p = 0.030), Lava Ultimate-Varseo Smile (p = 0.000) and Varseo
Smile – Ceramic Crown (p = 0.030).
- For Ivocerin (418 nm), transmittance % values for Lava Ultimate > Ceramic Crown
> Varseo Smile. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.029), Lava Ultimate-Varseo Smile (p = 0.000) and
Varseo Smile – Ceramic Crown (p = 0.029).
- For PPD (410 nm), transmittance % values for Lava Ultimate > Varseo Smile ≥
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000) and Lava Ultimate-Varseo Smile (p = 0.001).
- For Lucirin TPO (400 nm), transmittance % values for Lava Ultimate > Varseo
Smile > Ceramic Crown. Statistically significant differences were found between
Lava Ultimate-Ceramic Crown (p = 0.000) and between Lava Ultimate-Varseo Smile
(p = 0.007).

102
3.3 Material comparisons (by wavelength) – thickness = 3mm.
3.3.1 Camphorquinone (CQ) [468 nm]
For the materials tested, considering thickness = 3 mm, transmittance at 468 nm (CQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 18, Figure 87, Figure 88, Lava Ultimate had the highest transmittance
(mean = 0.12), followed by Varseo Smile (mean = 0.08) and Ceramic Crown (0.06).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.026). Moreover, Varseo Smile and Ceramic Crown also differed significantly
from each other (p=0.026). (Table 18 and Figure 88).
Figure 87. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for CQ (468nm)
Figure 88. (right) Group-wise comparisons of materials tested at 3 mm for CQ (468 nm)
Pairwise Comparisons of Materials for CQ (468nm) at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 10.000 3.814 2.622 .009 .026*
Ceramic Crown-Lava Ultimate 20.000 3.814 5.244 <.001 .000*
Varseo Smile-Lava Ultimate 10.000 3.814 2.622 .009 .026*
Table 18. Group-wise comparisons of materials tested at 3 mm for CQ (468nm)
0.08
0.06
0.12

103
3.3.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For the materials tested, considering thickness = 3 mm, transmittance at 420 nm (PQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 19, Figure 89, Figure 90, Lava Ultimate had the highest transmittance
(mean = 0.06), followed by Ceramic Crown (mean = 0.02) and Varseo Smile (mean = 0.01).
Pairwise comparison was significantly different from Ceramic crown (p=0.017) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.053). (Table 19 and Figure 90)
Figure 89. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for PQ (420 nm)
Figure 90. (right) Group-wise comparisons of materials tested at 3 mm for PQ (420 nm)
Pairwise Comparisons of Materials for PQ (420nm) at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -9.000 3.792 -2.374 .018 .053
Varseo Smile-Lava Ultimate 19.500 3.792 5.143 <.001 .000*
Ceramic Crown-Lava Ultimate 10.500 3.792 2.769 .006 .017*
Table 19. Group-wise comparisons of materials tested at 3 mm for PQ (420 nm)
0.01 0.02
0.06

104
3.3.3 Ivocerin [418nm]
For the materials tested, considering thickness = 3 mm, transmittance at 418 nm (Ivocerin)
was significantly different between some of the materials, according to the Kruskal-Wallis
test (p<0.001).
As shown in Table 20, Figure 91, Figure 92, Lava Ultimate had the highest transmittance
(mean = 0.06), followed by Varseo Smile (mean = 0.01) and Ceramic Crown (mean = 0.01).
Pairwise comparison was significantly different from Ceramic Crown (p=0.003) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.484). (Table 20 and Figure 92)
Figure 91. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for Ivocerin (418 nm)
Figure 92. (right) Group-wise comparisons of materials tested at 3 mm for Ivocerin (418 nm)
Pairwise Comparisons of Materials for Ivocerin (418nm) at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -5.200 3.714 -1.400 .161 .484
Varseo Smile-Lava Ultimate 17.600 3.714 4.739 <.001 .000*
Ceramic Crown-Lava Ultimate 12.400 3.714 3.339 <.001 .003*
Table 20. Group-wise comparisons of materials tested at 3 mm for Ivocerin (418 nm)
0.01
0.01
0.06

105
3.3.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For the materials tested, considering thickness = 3 mm, transmittance at 410 nm (PPD) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 21, Figure 93, Figure 94, Lava Ultimate had the highest transmittance
(mean = 0.05), followed by Varseo Smile (mean = 0.01) and Ceramic Crown (mean = 0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.003). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.473). (Table 21 and Figure 94).
Figure 93. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for PPD (410 nm)
Figure 94. (right) Group-wise comparisons of materials tested at 3 mm for PPD (410 nm)
Pairwise Comparisons of Materials for PPD (410nm) at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 5.300 3.751 1.413 .158 .473
Ceramic Crown-Lava Ultimate 17.650 3.751 4.706 <.001 .000*
Varseo Smile-Lava Ultimate 12.350 3.751 3.293 <.001 .003*
Table 21. Group-wise comparisons of materials tested at 3 mm for PPD (410 nm)
0.01 0.00
0.05

106
3.3.5 Lucirin TPO [400 nm]
For the materials tested, considering thickness = 3 mm, transmittance at 400 nm (Lucirin
TPO) was significantly different between some of the materials, according to the KruskalWallis test (p<0.001).
As shown in Table 22, Figure 95, Figure 96, Lava Ultimate had the highest transmittance
(mean = 0.03), followed by Varseo Smile (mean = 0.00) and Ceramic Crown (mean = 0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.002). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.676). (Table 22 and Figure 96)
Figure 95. (left) Kruskal-Wallis test boxplot of materials tested at 3 mm for Lucirin TPO (400nm)
Figure 96. (right) Group-wise comparisons of materials tested at 3 mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for Lucirin TPO (400nm) at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 4.500 3.712 1.212 .225 .676
Ceramic Crown-Lava Ultimate 17.250 3.712 4.647 <.001 .000*
Varseo Smile-Lava Ultimate 12.750 3.712 3.435 <.001 .002*
Table 22. Group-wise comparisons of materials tested at 3 mm for Lucirin TPO (400 nm)
0.00
0.00
0.03

107
3.3.6 Summary
When comparing the transmittance between the different materials (Lava Ultimate, Varseo
Smile and Ceramic Crown) at 2 mm thicknesses, the following trends were found:
- For CQ (468 nm), transmittance % values for Lava Ultimate > Varseo Smile >
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000), Lava Ultimate-Varseo Smile (p = 0.026) and
Varseo Smile – Ceramic Crown (p = 0.026).
- For PQ (420 nm), transmittance % values for Lava Ultimate > Ceramic Crown >
Varseo Smile. Statistically significant differences were found between Lava Ultimate
- Ceramic Crown (p = 0.017) and Lava Ultimate-Varseo Smile (p = 0.000).
- For Ivocerin (418 nm), transmittance % values for Lava Ultimate > Varseo Smile ≈
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.003) and Lava Ultimate-Varseo Smile (p = 0.000).
- For PPD (410 nm), transmittance % values for Lava Ultimate > Varseo Smile >
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000) and Lava Ultimate-Varseo Smile (p = 0.003).
- For Lucirin TPO (400 nm), transmittance % values for Lava Ultimate > Varseo
Smile ≥ Ceramic Crown. Statistically significant differences were found between
Lava Ultimate-Ceramic Crown (p = 0.000) and between Lava Ultimate-Varseo Smile
(p = 0.007).

108
3.4 Material comparisons (by wavelength) – thickness = 4mm.
3.4.1 Camphorquinone (CQ) [468 nm]
For the materials tested, considering thickness = 4 mm, transmittance at 468 nm (CQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 23, Figure 97 and Figure 98, Lava Ultimate had the highest transmittance
(mean = 0.06), followed by Varseo Smile (mean = 0.04) and Ceramic Crown (mean = 0.03).
Pairwise comparison was significantly different from Ceramic crown (p=0.000) and Varseo
Smile (p=0.028). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.067). (Table 23 and Figure 98)
Figure 97.(left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Lucirin TPO (400nm)
Figure 98. (right) Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for CQ (468nm) at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 8.800 3.850 2.286 .022 .067
Ceramic Crown-Lava Ultimate 18.800 3.850 4.883 <.001 .000*
Varseo Smile-Lava Ultimate 10.000 3.850 2.597 .009 .028*
Table 23. Group-wise comparisons of materials tested at 4 mm for CQ (468nm)
0.04
0.03
0.06

109
3.4.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For the materials tested, considering thickness = 4 mm, transmittance at 420 nm (PQ) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 24, Figure 99 and Figure 100, Lava Ultimate had the highest
transmittance (mean = 0.02), followed by Ceramic Crown (mean = 0.01) and Varseo Smile
(mean = 0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.011) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=0.830). (Table 24 and Figure 100)
Figure 99. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for PQ (420 nm)
Figure 100. (right) Group-wise comparisons of materials tested at 4 mm for PQ (420 nm)
Pairwise Comparisons of Materials for PQ (420nm) at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -4.150 3.815 -1.088 .277 .830
Varseo Smile-Lava Ultimate 15.200 3.815 3.984 <.001 .000*
Ceramic Crown-Lava Ultimate 11.050 3.815 2.896 .004 .011*
Table 24. Group-wise comparisons of materials tested at 4 mm for PQ (420 nm)
0.00
0.01
0.02

110
3.4.3 Ivocerin [418nm]
For the materials tested, considering thickness = 4 mm, transmittance at 418 nm (Ivocerin)
was significantly different between some of the materials, according to the Kruskal-Wallis
test (p<0.001)
As shown in Table 25, Figure 101 and Figure 102, Lava Ultimate had the highest
transmittance (mean = 0.02), followed by Ceramic Crown (mean = 0.01) and Varseo Smile
(mean = 0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.004) and Varseo
Smile (p=0.000). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=1.000). (Table 25 and Figure 102)
Figure 101. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Ivocerin (418 nm)
Figure 102. (right) Group-wise comparisons of materials tested at 4 mm for Ivocerin (418 nm)
Pairwise Comparisons of Materials for Ivocerin (418nm) at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Varseo Smile-Ceramic Crown -2.600 3.781 -.688 .492 1.000
Varseo Smile-Lava Ultimate 14.650 3.781 3.875 <.001 .000*
Ceramic Crown-Lava Ultimate 12.050 3.781 3.187 .001 .004*
Table 25. Group-wise comparisons of materials tested at 4 mm for Ivocerin (418 nm)
0.00
0.01
0.02

111
3.4.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For the materials tested, considering thickness = 4 mm, transmittance at 410 nm (PPD) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 26, Figure 103 and Figure 104, Lava Ultimate had the highest
transmittance (mean = 0.02), followed by Varseo Smile (mean = 0.00) and Ceramic Crown
(mean = 0.00).
Table 26 and Figure 104 present the group-wise comparisons, with only the comparisons
Lava Ultimate-Ceramic Crown (p=0.001) and Lava Ultimate-Varseo Smile (p=0.004) being
significant.
Figure 103. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for PPD (410 nm)
Figure 104. (right) Group-wise comparisons of materials tested at 4 mm for PPD (410 nm)
Pairwise Comparisons of Materials for PPD (410nm) at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 1.650 3.714 .444 .657 1.000
Ceramic Crown-Lava Ultimate 13.650 3.714 3.675 <.001 .001*
Varseo Smile-Lava Ultimate 12.000 3.714 3.231 .001 .004*
Table 26. Group-wise comparisons of materials tested at 4 mm for PPD (410 nm)
0.00
0.02
0.00

112
3.4.5 Lucirin TPO [400nm]
For the materials tested, considering thickness = 4 mm, transmittance at 400 nm (Lucirin
TPO) was significantly different between some of the materials, according to the KruskalWallis test (p<0.001).
As shown in Table 27, Figure 105 and Figure 106, Lava Ultimate had the highest
transmittance (mean = 0.01), followed by Varseo Smile (mean = 0.00) and Ceramic Crown
(mean = 0.00).
Pairwise comparison was significantly different from Ceramic crown (p=0.001) and Varseo
Smile (p=0.017). Moreover, Varseo Smile and Ceramic Crown did not differ significantly
from each other (p=1.000). (Table 27 and Figure 106)
Figure 105. (left) Kruskal-Wallis test boxplot of materials tested at 4 mm for Lucirin TPO (400nm)
Figure 106. (right) Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm)
Pairwise Comparisons of Materials for Lucirin TPO (400nm) at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
Ceramic Crown-Varseo Smile 2.850 3.729 .764 .445 1.000
Ceramic Crown-Lava Ultimate 13.200 3.729 3.540 <.001 .001*
Varseo Smile-Lava Ultimate 10.350 3.729 2.775 .006 .017*
Table 27. Group-wise comparisons of materials tested at 4 mm for Lucirin TPO (400nm)
0.00
0.01
0.00

113
3.4.6 Summary
When comparing the transmittance between the different materials (Lava Ultimate, Varseo
Smile and Ceramic Crown) at 2 mm thicknesses, the following trends were found:
- For CQ (468 nm), transmittance % values for Lava Ultimate > Varseo Smile >
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.000) and Lava Ultimate-Varseo Smile (p = 0.028).
- For PQ (420 nm), transmittance % values for Lava Ultimate > Ceramic Crown >
Varseo Smile. Statistically significant differences were found between Lava Ultimate
- Ceramic Crown (p = 0.011) and Lava Ultimate-Varseo Smile (p = 0.000).
- For Ivocerin (418 nm), transmittance % values for Lava Ultimate > Ceramic Crown
> Varseo Smile. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.004) and Lava Ultimate-Varseo Smile (p = 0.000).
- For PPD (410 nm), transmittance % values for Lava Ultimate > Varseo Smile ≥
Ceramic Crown. Statistically significant differences were found between Lava
Ultimate - Ceramic Crown (p = 0.001) and Lava Ultimate-Varseo Smile (p = 0.004).
- For Lucirin TPO (400 nm), transmittance % values for Lava Ultimate > Varseo
Smile ≥ Ceramic Crown. Statistically significant differences were found between
Lava Ultimate-Ceramic Crown (p = 0.001) and between Lava Ultimate-Varseo Smile
(p = 0.017).

114
4. Statistical analysis and comparisons between thicknesses:
When analyzing the transmittance of light by thickness, for all materials and
wavelengths, (Figure 107) it can be observed that light transmittance is highest for 1 mm,
followed by 2 mm, 3 mm and finally 4 mm.
Figure 107. Transmittance of light by thicknesses, at all materials and wavelengths
The differences between the materials are statistically significant for all the comparisons.
If analyzing the transmittance of light by thickness and materials (all wavelengths),
(Figure 108) it can be observed that light transmittance is highest for 1 mm for all materials,
followed by 2 mm, 3 mm and finally 4 mm.
The differences between the thicknesses are statistically significant for the comparisons 1 mm
- 2 mm, 1 mm - 3 mm, 1 mm - 4 mm and 2 mm - 4 mm for all materials, comparisons 2 mm -
3 mm for Lava Ultimate and Varseo Smile and 3 mm - 4 mm for Lava Ultimate.

115
Figure 108. Transmittance of light by thicknesses and materials (all wavelengths)
If looking in a more detailed way, at the transmittance of light by thickness and
wavelengths (all materials), (Figure 109) it can be observed that light transmittance is
highest for 1 mm for all wavelengths, followed by 2 mm, 3 mm and finally 4 mm.
Figure 109. Transmittance of light by thickness and wavelength (all materials)
The differences between the wavelengths are statistically significant for some of the groups
not for others. Mainly, between 1 mm - 2 mm (except for Lucirin TPO), 1 mm - 3 mm, 1 mm
- 4 mm and 2 mm - 4 mm (except for PPD (410 nm) and Lucirin TPO (400 nm)).
A more detailed comparison of the transmittance of light by thicknesses and wavelengths,
per material is described in the following pages:

116
4.1 Thickness comparisons (by wavelength) – Lava Ultimate:
4.1.1 Camphorquinone (CQ) [468 nm]
For all thicknesses, at Lava Ultimate, transmittance at 468 nm (CQ) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 28, Figure 110, and Figure 111, 1 mm thickness samples had the highest
transmittance (mean = 0.41), followed by 2 mm thickness samples (mean = 0.22), 3 mm
thickness samples (mean = 0.12) and 4 mm thickness samples (mean = 0.06).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.326), 2 mm – 3 mm (p=0.326), nor 3 mm – 4 mm (p=0.326). (Table 28 and Figure 111)
Figure 110. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for CQ (468nm)
Figure 111. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for CQ (468nm)
Pairwise Comparisons of Thicknesses for CQ (468nm) & Lava Ultimate
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.197 1.924 .054 .326
4 mm-2 mm 20.000 5.197 3.848 <.001 .001*
4 mm-1 mm 30.000 5.197 5.772 <.001 .000*
3 mm-2 mm 10.000 5.197 1.924 .054 .326
3 mm-1 mm 20.000 5.197 3.848 <.001 .001*
2 mm-1 mm 10.000 5.197 1.924 .054 .326
Table 28. Group-wise comparisons of thicknesses at Lava Ultimate group for CQ (468nm).
0.22
0.41
0.06
0.12

117
4.1.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For all thicknesses, at Lava Ultimate, transmittance at 420 nm (PQ) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 29, Figure 112, and Figure 113, 1 mm thickness samples had the highest
transmittance (mean = 0.32), followed by 2 mm thickness samples (mean = 0.14), 3 mm
thickness samples (mean = 0.06) and 4 mm thickness samples (mean = 0.02).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.323), 2 mm – 3 mm (p=0.323), nor 3 mm – 4 mm (p=0.323). (Table 29 and Figure 113)
Figure 112. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for PQ (420nm)
Figure 113. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for PQ (420nm)
Pairwise Comparisons of Thicknesses for PQ (420nm) & Lava Ultimate
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.188 1.928 .054 .323
4 mm-2 mm 20.000 5.188 3.855 <.001 .001*
4 mm-1 mm 30.000 5.188 5.783 <.001 .000*
3 mm-2 mm 10.000 5.188 1.928 .054 .323
3 mm-1 mm 20.000 5.188 3.855 <.001 .001*
2 mm-1 mm 10.000 5.188 1.928 .054 .323
Table 29. Group-wise comparisons of thicknesses at Lava Ultimate group for PQ (420nm)
0.22
0.41
0.06
0.12

118
4.1.3 Ivocerin [418 nm]
For all thicknesses, at Lava Ultimate, transmittance at 418 nm (Ivocerin) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 30, Figure 114, and Figure 115, 1 mm thickness samples had the highest
transmittance (mean = 0.32), followed by 2 mm thickness samples (mean = 0.13), 3 mm
thickness samples (mean = 0.06) and 4 mm thickness samples (mean = 0.02).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.327), 2 mm – 3 mm (p=0.327), nor 3 mm – 4 mm (p=0.327). (Table 30 and Figure 115)
Figure 114. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for Ivocerin (418 nm)
Figure 115. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for Ivocerin (418 nm)
Pairwise Comparisons of Thicknesses for Ivocerin (418nm) & Lava Ultimate
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.202 1.922 .055 .327
4 mm-2 mm 20.000 5.202 3.845 <.001 .001*
4 mm-1 mm 30.000 5.202 5.767 <.001 .000*
3 mm-2 mm 10.000 5.202 1.922 .055 .327
3 mm-1 mm 20.000 5.202 3.845 <.001 .001*
2 mm-1 mm 10.000 5.202 1.922 .055 .327
Table 30. Group-wise comparisons of thicknesses at Lava Ultimate group for Ivocerin (418 nm)
0.13
0.32
0.02
0.06

119
4.1.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For all thicknesses, at Lava Ultimate, transmittance at 410 nm (PPD) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 31, Figure 116, and Figure 117, 1 mm thickness samples had the highest
transmittance (mean = 0.29), followed by 2 mm thickness samples (mean = 0.12), 3 mm
thickness samples (mean = 0.05) and 4 mm thickness samples (mean = 0.02).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.329), 2 mm - 3 mm (p=0.329), nor 3 mm – 4 mm (p=0.329). (Table 31 and Figure 117)
Figure 116. (left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for PPD (410 nm)
Figure 117. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for PPD (410 nm)
Pairwise Comparisons of Thicknesses for PPD (410nm) & Lava Ultimate
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.207 1.920 .055 .329
4 mm-2 mm 20.000 5.207 3.841 <.001 .001*
4 mm-1 mm 30.000 5.207 5.761 <.001 .000*
3 mm-2 mm 10.000 5.207 1.920 .055 .329
3 mm-1 mm 20.000 5.207 3.841 <.001 .001*
2 mm-1 mm 10.000 5.207 1.920 .055 .329
Table 31. Group-wise comparisons of thicknesses at Lava Ultimate group for PPD (410 nm)
0.12
0.29
0.02
0.05

120
4.1.5 Lucirin TPO [400 nm]
For all thicknesses, at Lava Ultimate, transmittance at 400 nm (Lucirin TPO) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 32, Figure 118, and Figure 119, 1 mm thickness samples had the highest
transmittance (mean = 0.24), followed by 2 mm thickness samples (mean = 0.08), 3 mm
thickness samples (mean = 0.03) and 4 mm thickness samples (mean = 0.01).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.325), 2 mm - 3 mm (p=0.325), nor 3 mm – 4 mm (p=0.325). (Table 32 and Figure 119)
Figure 118.(left) Kruskal-Wallis test boxplot of thicknesses tested at Lava Ultimate for Lucirin TPO (400 nm)
Figure 119. (right) Group-wise comparisons of thicknesses tested at Lava Ultimate for CQ (468nm)
Pairwise Comparisons of Thicknesses for Lucirin TPO (400nm) & Lava Ultimate
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.192 1.926 .054 .325
4 mm-2 mm 20.000 5.192 3.852 <.001 .001*
4 mm-1 mm 30.000 5.192 5.778 <.001 .000*
3 mm-2 mm 10.000 5.192 1.926 .054 .325
3 mm-1 mm 20.000 5.192 3.852 <.001 .001*
2 mm-1 mm 10.000 5.192 1.926 .054 .325
Table 32. Group-wise comparisons of thicknesses at Lava Ultimate group for Lucirin TPO (400 nm)
0.08
0.24
0.01 0.03

121
4.1.6 Summary
When comparing the transmittance between the different thicknesses (1 mm, 2 mm, 3 mm
and 4mm) for Lava Ultimate material, the following trends were found:
- For CQ (468 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For PQ (420 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For Ivocerin (418 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For PPD (410 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For Lucirin TPO (400 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4
mm. Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).

122
4.2 Thickness comparisons (by wavelength) – Varseo Smile:
4.2.1 Camphorquinone (CQ) [468 nm]
For all thicknesses, at Varseo Smile, transmittance at 468 nm (CQ) was significantly different
between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 33, Figure 120, and Figure 121, 1 mm thickness samples had the highest
transmittance (mean = 0.32), followed by 2 mm thickness samples (mean = 0.16), 3 mm
thickness samples (mean = 0.08) and 4 mm thickness samples (mean = 0.04).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm - 2 mm
(p=0.324), 2 mm - 3 mm (p=0.324), nor 3 mm
– 4 mm (p=0.324). (Table 33 and Figure 121)
Figure 120. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for CQ (468nm)
Figure 121. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for CQ (468nm)
Pairwise Comparisons of Thicknesses for CQ (468nm) & Varseo Smile
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.189 1.927 .054 .324
4 mm-2 mm 20.000 5.189 3.854 <.001 .001*
4 mm-1 mm 30.000 5.189 5.781 <.001 .000*
3 mm-2 mm 10.000 5.189 1.927 .054 .324
3 mm-1 mm 20.000 5.189 3.854 <.001 .001*
2 mm-1 mm 10.000 5.189 1.927 .054 .324
Table 33. Group-wise comparisons of thicknesses at Varseo Smile group for CQ (468nm)
0.16
0.32
0.04
0.08

123
4.2.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For all thicknesses, at Varseo Smile, transmittance at 420 nm (PQ) was significantly different
between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 34, Figure 122, and Figure 123, 1 mm thickness samples had the highest
transmittance (mean = 0.12), followed by 2 mm thickness samples (mean = 0.03), 3 mm
thickness samples (mean = 0.01) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm – 2 mm
(p=0.323), 2 mm – 3 mm (p=0.323), nor 3 mm – 4 mm (p=0.323). (Table 34 and Figure 123)
Figure 122. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for PQ (420nm)
Figure 123. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for PQ (420nm)
Pairwise Comparisons of Thicknesses for PQ (420nm) & Varseo Smile
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.188 1.928 .054 .323
4 mm-2 mm 20.000 5.188 3.855 <.001 .001*
4 mm-1 mm 30.000 5.188 5.783 <.001 .000*
3 mm-2 mm 10.000 5.188 1.928 .054 .323
3 mm-1 mm 20.000 5.188 3.855 <.001 .001*
2 mm-1 mm 10.000 5.188 1.928 .054 .323
Table 34. Group-wise comparisons of thicknesses at Varseo Smile group for PQ (420nm)
0.03
0.12
0.01 0.00

124
4.2.3 Ivocerin [418 nm]
For all thicknesses, at Varseo Smile, transmittance at 418 nm (Ivocerin) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 35, Figure 124, and Figure 125, 1 mm thickness samples had the highest
transmittance (mean = 0.09), followed by 2 mm thickness samples (mean = 0.02), 3 mm
thickness samples (mean = 0.01) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.000), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.006), but did not differ between 1 mm – 2 mm
(p=0.241), 2 mm – 3 mm (p=0.185), nor 3 mm – 4 mm (p=1.000). (Table 35 and Figure 125)
Figure 124.(left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for Ivocerin (418 nm)
Figure 125. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for Ivocerin (418 nm)
Pairwise Comparisons of Thicknesses for Ivocerin (418nm) & Varseo Smile
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 5.900 5.166 1.142 .253 1.000
4 mm-2 mm 17.050 5.166 3.300 <.001 .006*
4 mm-1 mm 27.650 5.166 5.352 <.001 .000*
3 mm-2 mm 11.150 5.166 2.158 .031 .185
3 mm-1 mm 21.750 5.166 4.210 <.001 .000*
2 mm-1 mm 10.600 5.166 2.052 .040 .241
Table 35. Group-wise comparisons of thicknesses at Varseo Smile group for Ivocerin (418 nm)
0.0
0.09
0.01 0.00

125
4.2.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For all thicknesses, at Varseo Smile, transmittance at 410 nm (PPD) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 36, Figure 126, and Figure 127, 1 mm thickness samples had the highest
transmittance (mean = 0.03), followed by 2 mm thickness samples (mean = 0.01), 3 mm
thickness samples (mean = 0.01) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 2 mm (p=0.034), 1 mm – 3
mm (p=0.000) and 1 mm – 4 mm (p=0.000), but did not differ between 2 mm – 3 mm
(p=1.000), 2 mm – 4 mm (p=0.405) nor 3 mm – 4 mm (p=1.000). (Table 36 and Figure 127)
Figure 126. (left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for PPD (410 nm)
Figure 127. (right) Group-wise comparisons of thicknesses tested at Varseo Smile for PPD (410 nm)
Pairwise Comparisons of Thicknesses for PPD (410nm) & Varseo Smile
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 2.400 5.141 .467 .641 1.000
4 mm-2 mm 9.400 5.141 1.828 .068 .405
4 mm-1 mm 23.600 5.141 4.590 <.001 .000*
3 mm-2 mm 7.000 5.141 1.362 .173 1.000
3 mm-1 mm 21.200 5.141 4.123 <.001 .000*
2 mm-1 mm 14.200 5.141 2.762 .006 .034*
Table 36. Group-wise comparisons of thicknesses at Varseo Smile group for PPD (410 nm)
0.0
0.03
0.01 0.00

126
4.2.5 Lucirin TPO [400 nm]
For all thicknesses, at Varseo Smile, transmittance at 400 nm (Lucirin TPO) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 37, Figure 128, and Figure 129, 1 mm thickness samples had the highest
transmittance (mean = 0.02), followed by 2 mm thickness samples (mean = 0.01), 3 mm
thickness samples (mean = 0.00) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.006) and 1 mm
– 4 mm (p=0.002), but did not differ between 1 mm – 2 mm (p=0.433), 2 mm – 3 mm
(p=0.844), 2 mm – 4 mm (p=0.452) nor 3 mm – 4 mm (p=1.000). (Table 37 and Figure 129)
Figure 128.(left) Kruskal-Wallis test boxplot of thicknesses tested at Varseo Smile for Lucirin TPO (400 nm)
Figure 129.(right) Group-wise comparisons of thicknesses tested at Varseo Smile for CQ (468nm)
Pairwise Comparisons of Thicknesses for Lucirin TPO (400nm) & Varseo Smile
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 1.550 5.090 .305 .761 1.000
4 mm-2 mm 9.050 5.090 1.778 .075 .452
4 mm-1 mm 18.200 5.090 3.576 <.001 .002*
3 mm-2 mm 7.500 5.090 1.474 .141 .844
3 mm-1 mm 16.650 5.090 3.271 .001 .006*
2 mm-1 mm 9.150 5.090 1.798 .072 .433
Table 37. Group-wise comparisons of thicknesses at Varseo Smile group for Lucirin TPO (400 nm)
0.0
0.02
0.00 0.00

127
4.2.6 Summary
When comparing the transmittance between the different thicknesses (1 mm, 2 mm, 3 mm
and 4mm) for Varseo Smile material, the following trends were found:
- For CQ (468 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For PQ (420 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For Ivocerin (418 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.000), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.006).
- For PPD (410 nm), transmittance % values for 1 mm > 2 mm ≥ 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 2 mm
(significance 0.034), 1 mm – 3 mm (significance 0.000) and 1 mm – 4 mm
(significance 0.000).
- For Lucirin TPO (400 nm), transmittance % values for 1 mm > 2 mm > 3 mm ≥ 4
mm. Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.006), 1 mm – 4 mm (significance 0.002).

128
4.3 Thickness comparisons (by wavelength) – Ceramic Crown:
4.3.1 Camphorquinone (CQ) [468 nm]
For all thicknesses, at Ceramic Crown, transmittance at 468 nm (CQ) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 38, Figure 130, and Figure 131, 1 mm thickness samples had the highest
transmittance (mean = 0.29), followed by 2 mm thickness samples (mean = 0.13), 3 mm
thickness samples (mean = 0.06) and 4 mm thickness samples (mean = 0.03).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.001), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.001), but did not differ between 1 mm – 2 mm
(p=0.317), 2 mm – 3 mm (p=0.317), nor 3 mm – 4 mm (p=0.317). (Table 38 and Figure 131)
Figure 130. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for CQ (468nm)
Figure 131. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for CQ (468nm)
Pairwise Comparisons of Thickness for CQ (468nm) & Ceramic Crown
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 10.000 5.166 1.936 .053 .317
4 mm-2 mm 20.000 5.166 3.871 <.001 .001*
4 mm-1 mm 30.000 5.166 5.807 <.001 .000*
3 mm-2 mm 10.000 5.166 1.936 .053 .317
3 mm-1 mm 20.000 5.166 3.871 <.001 .001*
2 mm-1 mm 10.000 5.166 1.936 .053 .317
Table 38. Group-wise comparisons of thicknesses at Ceramic Crown group for CQ (468nm)
0.1
0.29
0.03 0.06

129
4.3.2 9,10-Phenanthrenequinone (PQ) [420 nm]
For all thicknesses, at Ceramic Crown, transmittance at 420 nm (PQ) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 39, Figure 132, and Figure 133, 1 mm thickness samples had the highest
transmittance (mean = 0.20), followed by 2 mm thickness samples (mean = 0.05), 3 mm
thickness samples (mean = 0.02) and 4 mm thickness samples (mean = 0.01).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.000), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.002), but did not differ between 1 mm – 2 mm
(p=0.331), 2 mm – 3 mm (p=0.209), nor 3 mm – 4 mm (p=0.750). (Table 39 and Figure 133)
Figure 132. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for PQ (420nm)
Figure 133. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for PQ (420nm)
Pairwise Comparisons of Thickness for PQ (420nm) & Ceramic Crown
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 8.000 5.214 1.534 .125 .750
4 mm-2 mm 19.000 5.214 3.644 <.001 .002*
4 mm-1 mm 29.000 5.214 5.562 <.001 .000*
3 mm-2 mm 11.000 5.214 2.110 .035 .209
3 mm-1 mm 21.000 5.214 4.028 <.001 .000*
2 mm-1 mm 10.000 5.214 1.918 .055 .331
Table 39. Group-wise comparisons of thicknesses at Ceramic Crown group for PQ (420nm)
0.05
0.20
0.02 0.01

130
4.3.3 Ivocerin [418 nm]
For all thicknesses, at Ceramic Crown, transmittance at 418 nm (Ivocerin) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 40, Figure 134, and Figure 135, 1 mm thickness samples had the highest
transmittance (mean = 0.18), followed by 2 mm thickness samples (mean = 0.04), 3 mm
thickness samples (mean = 0.02) and 4 mm thickness samples (mean = 0.01).
Pairwise comparison was significantly different between 1 mm – 3 mm (p=0.000), 1 mm – 4
mm (p=0.000) and 2 mm – 4 mm (p=0.003), but did not differ between 1 mm – 2 mm
(p=0.318), 2 mm – 3 mm (p=0.134), nor 3 mm – 4 mm (p=1.000). (Table 40 and Figure 135)
Figure 134. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for Ivocerin (418 nm)
Figure 135. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for Ivocerin (418 nm)
Pairwise Comparisons of Thickness for Ivocerin (418nm) & Ceramic Crown
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm 6.400 5.168 1.238 .216 1.000
4 mm-2 mm 18.200 5.168 3.522 <.001 .003*
4 mm-1 mm 28.200 5.168 5.457 <.001 .000*
3 mm-2 mm 11.800 5.168 2.283 .022 .134
3 mm-1 mm 21.800 5.168 4.218 <.001 .000*
2 mm-1 mm 10.000 5.168 1.935 .053 .318
Table 40. Group-wise comparisons of thicknesses at Ceramic Crown group for Ivocerin (418 nm)
0.04
0.18
0.01 0.02

131
4.3.4 1-Phenyl-1,2 propanedione (PPD) [410 nm]
For all thicknesses, at Ceramic Crown, transmittance at 410 nm (PPD) was significantly
different between some of the materials, according to the Kruskal-Wallis test (p<0.001).
As shown in Table 41, Figure 136, and Figure 137, 1 mm thickness samples had the highest
transmittance (mean = 0.08), followed by 2 mm thickness samples (mean = 0.01), 3 mm
thickness samples (mean = 0.00) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 2 mm (p=0.042), 1 mm – 3
mm (p=0.000) and 1 mm – 4 mm (p=0.000), but did not differ between 2 mm – 3 mm
(p=0.381), 2 mm – 4 mm (p=0.158) nor 3 mm – 4 mm (p=1.000). (Table 41 and Figure 137)
Figure 136. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for PPD (410 nm)
Figure 137. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for PPD (410 nm)
Pairwise Comparisons of Thickness for PPD (410nm) & Ceramic Crown
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm -1.800 4.930 -.365 .715 1.000
4 mm-2 mm 10.950 4.930 2.221 .026 .158
4 mm-1 mm 24.250 4.930 4.919 <.001 .000*
3 mm-2 mm 9.150 4.930 1.856 .063 .381
3 mm-1 mm 22.450 4.930 4.554 <.001 .000*
2 mm-1 mm 13.300 4.930 2.698 .007 .042*
Table 41. Group-wise comparisons of thicknesses at Ceramic Crown group for PPD (410 nm)
0.01
0.08
0.00 0.00

132
4.3.5 Lucirin TPO [400 nm]
For all thicknesses, at Ceramic Crown, transmittance at 400 nm (Lucirin TPO) was
significantly different between some of the materials, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 42, Figure 138 and Figure 139, 1 mm thickness samples had the highest
transmittance (mean = 0.02), followed by 2 mm thickness samples (mean = 0.00), 3 mm
thickness samples (mean = 0.00) and 4 mm thickness samples (mean = 0.00).
Pairwise comparison was significantly different between 1 mm – 2 mm (p=0.007), 1 mm – 3
mm (p=0.002) and 1 mm – 4 mm (p=0.001), but did not differ between 2 mm – 3 mm
(p=1.000), 2 mm – 4 mm (p=1.000) nor 3 mm – 4 mm (p=1.000). (Table 42 and Figure 139)
Figure 138. (left) Kruskal-Wallis test boxplot of thicknesses tested at Ceramic Crown for Lucirin TPO (400 nm)
Figure 139. (right) Group-wise comparisons of thicknesses tested at Ceramic Crown for CQ (468nm)
Pairwise Comparisons of Thicknesses for Lucirin TPO (400nm) & Ceramic Crown
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
4 mm-3 mm -.850 4.538 -.187 .851 1.000
4 mm-2 mm 2.200 4.538 .485 .628 1.000
4 mm-1 mm 16.950 4.538 3.735 <.001 .001*
3 mm-2 mm 1.350 4.538 .298 .766 1.000
3 mm-1 mm 16.100 4.538 3.548 <.001 .002*
2 mm-1 mm 14.750 4.538 3.251 .001 .007*
Table 42. Group-wise comparisons of thicknesses at Ceramic Crown group for Lucirin TPO (400 nm)
0.02
0.00 0.00 0.00

133
4.3.6 Summary
When comparing the transmittance between the different thicknesses (1 mm, 2 mm, 3 mm
and 4mm) for Ceramic Crown material, the following trends were found:
- For CQ (468 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.001), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.001).
- For PQ (420 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.000), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.002).
- For Ivocerin (418 nm), transmittance % values for 1 mm > 2 mm > 3 mm > 4 mm.
Statistically significant differences were found between the groups 1 mm – 3 mm
(significance 0.000), 1 mm – 4 mm (significance 0.000) and 2 mm – 4 mm
(significance 0.003).
- For PPD (410 nm), transmittance % values for 1 mm > 2 mm > 3 mm ≈ 4 mm.
Statistically significant differences were found between the groups 1 mm – 2 mm
(significance 0.042), 1 mm – 3 mm (significance 0.000) and 1 mm – 4 mm
(significance 0.000).
- For Lucirin TPO (400 nm), transmittance % values for 1 mm > 2 mm ≈ 3 mm ≈ 4
mm. Statistically significant differences were found between the groups 1 mm – 2 mm
(significance 0.007), 1 mm – 3 mm (significance 0.002), 1 mm – 4 mm (significance
0.001).

134
5. Statistical analysis and comparisons between photoinitiators:
When analyzing the transmittance of light by photoinitiators (wavelengths), for all
materials and thicknesses, (Figure 140) it can be observed that light transmittance is highest
for CQ (468 nm), followed by PQ (420 nm), Ivocerin (418 nm), PPD (410 nm) and finally
Lucirin TPO (400 nm).
Figure 140. Transmittance of light by wavelength, at all materials and thicknesses
The differences between the materials are statistically significant for all groups, except for
PQ-Ivocerin and PPD-Lucirin TPO.
If looking in a more detailed way, at the transmittance of light by photoinitiators
(wavelengths) and materials (all thicknesses), (Figure 141) it can be observed that light
transmittance is still highest for CQ (468 nm), followed by PQ (420 nm), Ivocerin (418 nm),
PPD (410 nm) and finally Lucirin TPO.
The differences between the wavelengths for the different materials are statistically
significant for some of the groups, but not statistically significant for many others.

135
Figure 141. Transmittance of light by photoinitiator (wavelength) and materials (all thicknesses)
If looking in a more detailed way, at the transmittance of light by photoinitiators
(wavelengths) and thickness (all materials), (Figure 142) it can be observed that light
transmittance is still highest for CQ (468 nm), followed by PQ (420 nm), Ivocerin (418 nm),
PPD (410 nm) and finally Lucirin TPO.
Figure 142. Transmittance of light by photoinitiator (wavelength) and thickness (all materials)
The differences between the wavelengths are statistically significant for some of the groups,
but not for others.
A more detailed comparison of the transmittance of light by photoinitiator (wavelength),
thickness and materials is described in the following pages:

136
5.1 Photoinitiator (wavelength) comparison (by material) – thickness = 1 mm
5.1.1 Lava Ultimate
For photoinitiator (wavelength) comparison, for Lava Ultimate at 1mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 43, Figure 143, and Figure 144, CQ [468 nm] had the highest
transmittance (mean = 0.41), followed by PQ [420 nm] (mean = 0.32), Ivocerin [418 nm]
(mean = 0.32), PPD [410 nm] (mean = 0.29) and Lucirin TPO [400 nm] (mean = 0.24).
Table 43 and Figure 144 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PPD [410 nm] (p=0.000), CQ [468 nm] – Lucirin TPO [400 nm] (p=0.000), PQ
[420 nm] – Lucirin TPO [400 nm] (p=0.000) and Ivocerin [418 nm] – Lucirin TPO [400 nm]
(p=0.006) being significant.
Figure 143. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 1 mm
Figure 144. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 1 mm
Pairwise Comparisons of Photoinitiators for Lava Ultimate at 1mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 11.150 6.498 1.716 .086 .862
TPO (400nm)-Ivocerin (418nm) 22.400 6.498 3.447 <.001 .006*
TPO (400nm)-PQ (420nm) 26.450 6.498 4.070 <.001 .000*
TPO (400nm)-CQ (468nm) 40.000 6.498 6.156 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 11.250 6.498 1.731 .083 .834
PPD (410nm)-PQ (420nm) 15.300 6.498 2.355 .019 .185
PPD (410nm)-CQ (468nm) 28.850 6.498 4.440 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 4.050 6.498 .623 .533 1.000
Ivocerin (418nm)-CQ (468nm) 17.600 6.498 2.709 .007 .068
PQ (420nm)-CQ (468nm) 13.550 6.498 2.085 .037 .370
Table 43. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 1 mm
0.41
0.24
0.32
0.29
0.32

137
5.1.2 Varseo Smile
For photoinitiator (wavelength) comparison, for Varseo Smile at 1mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 44, Figure 145, and Figure 146, CQ [468 nm] had the highest
transmittance (mean = 0.32), followed by PQ [420 nm] (mean = 0.12), Ivocerin [418 nm]
(mean = 0.09), PPD [410 nm] (mean = 0.03) and Lucirin TPO [400 nm] (mean = 0.02).
Table 44 and Figure 146 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – Ivocerin [418 nm] (p=0.021), CQ [468 nm] – PPD [410 nm] (p=0.000), CQ [468
nm] – Lucirin TPO [400 nm] (p=0.000), PQ [420 nm] – PPD [410 nm] (p=0.006) and PQ
[420 nm] – Lucirin TPO [400 nm] (p=0.000) being significant.
Figure 145. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 1 mm
Figure 146. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 1 mm
Pairwise Comparisons of Photoinitiators for Varseo Smile at 1mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 5.600 6.502 .861 .389 1.000
TPO (400nm)-Ivocerin (418nm) 17.800 6.502 2.737 .006 .062
TPO (400nm)-PQ (420nm) 27.800 6.502 4.275 <.001 .000*
TPO (400nm)-CQ (468nm) 37.800 6.502 5.813 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 12.200 6.502 1.876 .061 .606
PPD (410nm)-PQ (420nm) 22.200 6.502 3.414 <.001 .006*
PPD (410nm)-CQ (468nm) 32.200 6.502 4.952 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 10.000 6.502 1.538 .124 1.000
Ivocerin (418nm)-CQ (468nm) 20.000 6.502 3.076 .002 .021*
PQ (420nm)-CQ (468nm) 10.000 6.502 1.538 .124 1.000
Table 44. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 1 mm
0.32
0.12
0.03 0.02
0.09

138
5.1.3 Ceramic Crown
For photoinitiator (wavelength) comparison, for Ceramic Crown at 1mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 45, Figure 147, and Figure 148, CQ [468 nm] had the highest
transmittance (mean = 0.29), followed by PQ [420 nm] (mean = 0.20), Ivocerin [418 nm]
(mean = 0.18), PPD [410 nm] (mean = 0.08) and Lucirin TPO [400 nm] (mean = 0.02).
Table 45 and Figure 148 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PPD [410 nm] (p=0.000), CQ [468 nm] – Lucirin TPO [400 nm] (p=0.000), PQ
[420 nm] – PPD [410 nm] (p=0.043), PQ [420 nm] – Lucirin TPO [400 nm] (p=0.000) and
Ivocerin [418 nm] – Lucirin TPO [400 nm] (p=0.010) being significant.
Figure 147. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 1 mm
Figure 148. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 1 mm
Pairwise Comparisons of Photoinitiators for Ceramic Crown at 1mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 8.700 6.514 1.336 .182 1.000
TPO (400nm)-Ivocerin (418nm) 21.400 6.514 3.285 .001 .010*
TPO (400nm)-PQ (420nm) 27.300 6.514 4.191 <.001 .000*
TPO (400nm)-CQ (468nm) 39.350 6.514 6.041 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 12.700 6.514 1.950 .051 .512
PPD (410nm)-PQ (420nm) 18.600 6.514 2.855 .004 .043*
PPD (410nm)-CQ (468nm) 30.650 6.514 4.705 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 5.900 6.514 .906 .365 1.000
Ivocerin (418nm)-CQ (468nm) 17.950 6.514 2.756 .006 .059
PQ (420nm)-CQ (468nm) 12.050 6.514 1.850 .064 .643
Table 45. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 1 mm
0.29
0.02
0.20
0.08
0.18

139
5.1.4 Summary
When comparing the transmittance between the different photoinitiators (CQ, PQ, Ivocerin,
PPD, Lucirin TPO) at 1 mm thickness, the following trends were found:
- In general (no difference in material), transmittance % values for CQ [468 nm] >
PQ [420 nm] > Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm].
Statistically significant differences were found between six groups: CQ [468 nm] –
PQ [420 nm] (significance 0.008), CQ [468 nm] – Ivocerin [418 nm] (significance
0.001), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468 nm] – Lucirin
TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm] (significance
0.063), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.000), Ivocerin [418 nm]
– Lucirin TPO [400 nm] (significance 0.000) and PPD [410 nm] – Lucirin TPO [400
nm] (significance 0.004).
- For Lava Ultimate, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between four groups: CQ [468 nm] – PPD [410 nm]
(significance 0.000), CQ [468 nm] – Lucirin TPO [400 nm] (significance 0.000), PQ
[420 nm] – Lucirin TPO [400 nm] (significance 0.000) and Ivocerin [418 nm] –
Lucirin TPO [400 nm] (significance 0.006).
- For Varseo Smile, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between five groups: CQ [468 nm] – Ivocerin [418 nm]
(significance 0.021), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468
nm] – Lucirin TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm]
(significance 0.006) and PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.000).
- For Ceramic Crown, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between CQ [468 nm] – PPD [410 nm] (significance 0.000),
CQ [468 nm] – Lucirin TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410
nm] (significance 0.043), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.000)
and Ivocerin [418 nm] – Lucirin TPO [400 nm] (significance 0.010).

140
5.2 Photoinitiator (wavelength) comparison (by material) – thickness = 2 mm
5.2.1 Lava Ultimate
For photoinitiator (wavelength) comparison, for Lava Ultimate at 2 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 46, Figure 149, and Figure 150, CQ [468 nm] had the highest
transmittance (mean = 0.22), followed by PQ [420 nm] (mean = 0.14), Ivocerin [418 nm]
(mean = 0.13), PPD [410 nm] (mean = 0.12) and Lucirin TPO [400 nm] (mean = 0.08).
Table 46 and Figure 150 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PPD [410 nm] (significance 0.000), CQ [468 nm] – Lucirin TPO [400 nm]
(p=0.000), PQ [420 nm] – Lucirin TPO [400 nm] (p=0.000) and Ivocerin [418 nm] – Lucirin
TPO [400 nm] (p=0.005) being significant.
Figure 149. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 2 mm
Figure 150. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 2 mm
Pairwise Comparisons of Photoinitiators for Lava Ultimate at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 10.250 6.486 1.580 .114 1.000
TPO (400nm)-Ivocerin (418nm) 22.600 6.486 3.484 <.001 .005*
TPO (400nm)-PQ (420nm) 27.150 6.486 4.186 <.001 .000*
TPO (400nm)-CQ (468nm) 40.000 6.486 6.167 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 12.350 6.486 1.904 .057 .569
PPD (410nm)-PQ (420nm) 16.900 6.486 2.605 .009 .092
PPD (410nm)-CQ (468nm) 29.750 6.486 4.587 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 4.550 6.486 .701 .483 1.000
Ivocerin (418nm)-CQ (468nm) 17.400 6.486 2.683 .007 .073
PQ (420nm)-CQ (468nm) 12.850 6.486 1.981 .048 .476
Table 46. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 2 mm
0.22
0.08
0.14
0.12 0.13

141
5.2.2 Varseo Smile
For photoinitiator (wavelength) comparison, for Varseo Smile at 2 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 47, Figure 151, and Figure 152, CQ [468 nm] had the highest
transmittance (mean = 0.16), followed by PQ [420 nm] (mean = 0.03), Ivocerin [418 nm]
(mean = 0.02), PPD [410 nm] (mean = 0.01) and Lucirin TPO [400 nm] (mean = 0.01).
Table 47 and Figure 152 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – Ivocerin [418 nm] (p=0.021), CQ [468 nm] – PPD [410 nm] (p=0.000), CQ [468
nm] – Lucirin TPO [400 nm] (p=0.000), PQ [420 nm] – PPD [410 nm] (p=0.002) and PQ
[420 nm] – Lucirin TPO [400 nm] (p=0.003) being significant.
Figure 151. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 2 mm
Figure 152. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 2 mm
Pairwise Comparisons of Photoinitiators for Varseo Smile at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
PPD (410nm)-TPO (400nm) -.200 6.458 -.031 .975 1.000
PPD (410nm)-Ivocerin (418nm) 14.800 6.458 2.292 .022 .219
PPD (410nm)-PQ (420nm) 23.800 6.458 3.686 <.001 .002*
PPD (410nm)-CQ (468nm) 34.700 6.458 5.374 <.001 .000*
TPO (400nm)-Ivocerin (418nm) 14.600 6.458 2.261 .024 .238
TPO (400nm)-PQ (420nm) 23.600 6.458 3.655 <.001 .003*
TPO (400nm)-CQ (468nm) 34.500 6.458 5.343 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 9.000 6.458 1.394 .163 1.000
Ivocerin (418nm)-CQ (468nm) 19.900 6.458 3.082 .002 .021*
PQ (420nm)-CQ (468nm) 10.900 6.458 1.688 .091 .914
Table 47. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 2 mm.
0.16
0.01
0.03
0.01 0.02

142
5.2.3 Ceramic Crown
For photoinitiator (wavelength) comparison, for Ceramic Crown at 2 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 48, Figure 153, and Figure 154, CQ [468 nm] had the highest
transmittance (mean = 0.13), followed by PQ [420 nm] (mean = 0.05), Ivocerin [418 nm]
(mean = 0.04), PPD [410 nm] (mean = 0.01) and Lucirin TPO [400 nm] (mean = 0.00).
Table 48 and Figure 154 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – Ivocerin [418 nm] (p=0.023), CQ [468 nm] – PPD [410 nm] (p=0.000), CQ [468
nm] – Lucirin TPO [400 nm] (p=0.000), PQ [420 nm] – PPD [410 nm] (p=0.009), PQ [420
nm] – Lucirin TPO [400 nm] (p=0.000) and Ivocerin [418 nm] – Lucirin TPO [400 nm]
(p=0.043) being significant.
Figure 153. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 2 mm
Figure 154. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 2 mm
Pairwise Comparisons of Photoinitiators for Ceramic Crown at 2mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 6.300 6.468 .974 .330 1.000
TPO (400nm)-Ivocerin (418nm) 18.450 6.468 2.853 .004 .043*
TPO (400nm)-PQ (420nm) 27.850 6.468 4.306 <.001 .000*
TPO (400nm)-CQ (468nm) 38.150 6.468 5.899 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 12.150 6.468 1.879 .060 .603
PPD (410nm)-PQ (420nm) 21.550 6.468 3.332 <.001 .009*
PPD (410nm)-CQ (468nm) 31.850 6.468 4.925 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 9.400 6.468 1.453 .146 1.000
Ivocerin (418nm)-CQ (468nm) 19.700 6.468 3.046 .002 .023*
PQ (420nm)-CQ (468nm) 10.300 6.468 1.593 .111 1.000
Table 48. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 2 mm
0.13
0.00
0.05
0.01
0.04

143
5.2.4 Summary
When comparing the transmittance between the different photoinitiators (CQ, PQ, Ivocerin,
PPD, Lucirin TPO) at 2 mm thickness, the following trends were found:
- In general (no difference in material), transmittance % values for CQ [468 nm] >
PQ [420 nm] > Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm].
Statistically significant differences were found between seven groups: CQ [468 nm] –
PQ [420 nm] (significance 0.000), CQ [468 nm] – Ivocerin [418 nm] (significance
0.000), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468 nm] – Lucirin
TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm] (significance
0.014), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.001) and Ivocerin [418
nm] – Lucirin TPO [400 nm] (significance 0.016).
- For Lava Ultimate, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between four groups: CQ [468 nm] – PPD [410 nm]
(significance 0.000), CQ [468 nm] – Lucirin TPO [400 nm] (significance 0.000), PQ
[420 nm] – Lucirin TPO [400 nm] (significance 0.000) and Ivocerin [418 nm] –
Lucirin TPO [400 nm] (significance 0.005).
- For Varseo Smile, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] ≈ Lucirin TPO [400 nm]. Statistically significant
differences were found between five groups: CQ [468 nm] – Ivocerin [418 nm]
(significance 0.021), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468
nm] – Lucirin TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm]
(significance 0.002) and PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.003).
- For Ceramic Crown, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between six groups: CQ [468 nm] – Ivocerin [418 nm]
(significance 0.023), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468
nm] – Lucirin TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm]
(significance 0.009), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.000) and
Ivocerin [418 nm] – Lucirin TPO [400 nm] (significance 0.043).

144
5.3 Photoinitiator (wavelength) comparison (by material) – thickness = 3 mm
5.3.1 Lava Ultimate
For photoinitiator (wavelength) comparison, for Lava Ultimate at 3 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 49, Figure 155, and Figure 156, CQ [468 nm] had the highest
transmittance (mean = 0.12), followed by PQ [420 nm] (mean = 0.06), Ivocerin [418 nm]
(mean = 0.06), PPD [410 nm] (mean = 0.05) and Lucirin TPO [400 nm] (mean = 0.03).
Table 49 and Figure 156 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PPD [410 nm] (p=0.000), CQ [468 nm] – Lucirin TPO [400 nm] (p=0.000), PQ
[420 nm] – Lucirin TPO [400 nm] (p=0.000) and Ivocerin [418 nm] – Lucirin TPO [400 nm]
(p=0.004) being significant.
Figure 155. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 3 mm
Figure 156. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 3 mm
Pairwise Comparisons of Photoinitiators for Lava Ultimate at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 10.300 6.423 1.604 .109 1.000
TPO (400nm)-Ivocerin (418nm) 22.800 6.423 3.550 <.001 .004*
TPO (400nm)-PQ (420nm) 26.900 6.423 4.188 <.001 .000*
TPO (400nm)-CQ (468nm) 40.000 6.423 6.228 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 12.500 6.423 1.946 .052 .516
PPD (410nm)-PQ (420nm) 16.600 6.423 2.585 .010 .097
PPD (410nm)-CQ (468nm) 29.700 6.423 4.624 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 4.100 6.423 .638 .523 1.000
Ivocerin (418nm)-CQ (468nm) 17.200 6.423 2.678 .007 .074
PQ (420nm)-CQ (468nm) 13.100 6.423 2.040 .041 .414
Table 49. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 3 mm.
0.12
0.03 0.05
0.06 0.06

145
5.3.2 Varseo Smile
For photoinitiator (wavelength) comparison, for Varseo Smile at 3 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 50, Figure 157, and Figure 158, CQ [468 nm] had the highest
transmittance (mean = 0.08), followed by PQ [420 nm] (mean = 0.01), Ivocerin [418 nm]
(mean = 0.01), PPD [410 nm] (mean = 0.01) and Lucirin TPO [400 nm] (mean = 0.01).
Table 50 and Figure 158 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – Ivocerin [418 nm] (p=0.003), CQ [468 nm] – PPD [410 nm] (p=0.000), CQ [468
nm] – Lucirin TPO [400 nm] (p=0.000) being significant.
Figure 157. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 3 mm
Figure 158. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 3 mm
Pairwise Comparisons of Photoinitiators for Varseo Smile at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) .950 6.193 .153 .878 1.000
TPO (400nm)-Ivocerin (418nm) 8.800 6.193 1.421 .155 1.000
TPO (400nm)-PQ (420nm) 15.250 6.193 2.462 .014 .138
TPO (400nm)-CQ (468nm) 31.250 6.193 5.046 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 7.850 6.193 1.268 .205 1.000
PPD (410nm)-PQ (420nm) 14.300 6.193 2.309 .021 .209
PPD (410nm)-CQ (468nm) 30.300 6.193 4.893 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 6.450 6.193 1.041 .298 1.000
Ivocerin (418nm)-CQ (468nm) 22.450 6.193 3.625 <.001 .003*
PQ (420nm)-CQ (468nm) 16.000 6.193 2.583 .010 .098
Table 50. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 3 mm
0.08
0.01 0.01 0.01 0.01

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5.3.3 Ceramic Crown
For photoinitiator (wavelength) comparison, for Ceramic Crown at 3 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 51, Figure 159, and Figure 160, CQ [468 nm] had the highest
transmittance (mean = 0.06), followed by PQ [420 nm] (mean = 0.02), Ivocerin [418 nm]
(mean = 0.01), PPD [410 nm] (mean = 0.00) and Lucirin TPO [400 nm] (mean = 0.00).
Table 51 and Figure 160 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – Ivocerin [418 nm] (p=0.031), CQ [468 nm] – PPD [410 nm] (p=0.000), CQ [468
nm] – Lucirin TPO [400 nm] (p=0.000), PQ [420 nm] – PPD [410 nm] (p=0.002), PQ [420
nm] – Lucirin TPO [400 nm] (p=0.002) being significant.
Figure 159. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 3 mm
Figure 160. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 3 mm
Pairwise Comparisons of Photoinitiators for Ceramic Crown at 3mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) .100 6.313 .016 .987 1.000
TPO (400nm)-Ivocerin (418nm) 16.400 6.313 2.598 .009 .094
TPO (400nm)-PQ (420nm) 23.700 6.313 3.754 <.001 .002*
TPO (400nm)-CQ (468nm) 35.050 6.313 5.552 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 16.300 6.313 2.582 .010 .098
PPD (410nm)-PQ (420nm) 23.600 6.313 3.738 <.001 .002*
PPD (410nm)-CQ (468nm) 34.950 6.313 5.536 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 7.300 6.313 1.156 .248 1.000
Ivocerin (418nm)-CQ (468nm) 18.650 6.313 2.954 .003 .031*
PQ (420nm)-CQ (468nm) 11.350 6.313 1.798 .072 .722
Table 51. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 3 mm
0.00 0.00
0.02 0.01
0.06

147
5.3.4 Summary
When comparing the transmittance between the different photoinitiators (CQ, PQ, Ivocerin,
PPD, Lucirin TPO) at 3 mm, the following trends were found:
- In general (no difference in material), transmittance % values for CQ [468 nm] >
PQ [420 nm] ≈ Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm].
Statistically significant differences were found between six groups: CQ [468 nm] –
PQ [420 nm] (significance 0.000), CQ [468 nm] – Ivocerin [418 nm] (significance
0.000), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468 nm] – Lucirin
TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm] (significance
0.025) and PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.007).
- For Lava Ultimate, transmittance % values for CQ [468 nm] > PQ [420 nm] ≈
Ivocerin [418 nm] > PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between four groups: CQ [468 nm] – PPD [410 nm]
(significance 0.000), CQ [468 nm] – Lucirin TPO [400 nm] (significance 0.000), PQ
[420 nm] – Lucirin TPO [400 nm] (significance 0.000) and Ivocerin [418 nm] –
Lucirin TPO [400 nm] (significance 0.004).
- For Varseo Smile, transmittance % values for CQ [468 nm] > PQ [420 nm] ≈
Ivocerin [418 nm] ≈ PPD [410 nm] ≈ Lucirin TPO [400 nm]. Statistically significant
differences were found between three groups: CQ [468 nm] – Ivocerin [418 nm]
(significance 0.003), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468
nm] – Lucirin TPO [400 nm] (significance 0.000).
- For Ceramic Crown, transmittance % values for CQ [468 nm] > PQ [420 nm] >
Ivocerin [418 nm] > PPD [410 nm] ≈ Lucirin TPO [400 nm]. Statistically significant
differences were found between five groups: CQ [468 nm] – Ivocerin [418 nm]
(significance 0.031), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468
nm] – Lucirin TPO [400 nm] (significance 0.000), PQ [420 nm] – PPD [410 nm]
(significance 0.002), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.002).

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5.4 Photoinitiator (wavelength) comparison (by material ) – thickness = 4 mm
5.4.1 Lava Ultimate
For photoinitiator (wavelength) comparison, for Lava Ultimate at 4 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 52, Figure 161, and Figure 162, CQ [468 nm] had the highest
transmittance (mean = 0.06), followed by PQ [420 nm] (mean = 0.02), Ivocerin [418 nm]
(mean = 0.02), PPD [410 nm] (mean = 0.02) and Lucirin TPO [400 nm] (mean = 0.01).
Table 52 and Figure 162present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PQ [420 nm] (p=0.021), CQ [468 nm] – Ivocerin [418 nm] (p=0.034), CQ [468
nm] – PPD [410 nm] (p=0.001), CQ [468 nm] – Lucirin TPO [400 nm] (p=0.000), PQ [420
nm] – Lucirin TPO [400 nm] (p=0.046) and Ivocerin [418 nm] – Lucirin TPO [400 nm]
(p=0.028) being significant.
Figure 161. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Lava Ultimate at 4 mm
Figure 162. (right) Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 4 mm
Pairwise Comparisons of Photoinitiators for Lava Ultimate at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 12.050 6.284 1.917 .055 .552
TPO (400nm)-PQ (420nm) 17.800 6.284 2.832 .005 .046*
TPO (400nm)-Ivocerin (418nm) 18.750 6.284 2.984 .003 .028*
TPO (400nm)-CQ (468nm) 37.150 6.284 5.912 <.001 .000*
PPD (410nm)-PQ (420nm) 5.750 6.284 .915 .360 1.000
PPD (410nm)-Ivocerin (418nm) 6.700 6.284 1.066 .286 1.000
PPD (410nm)-CQ (468nm) 25.100 6.284 3.994 <.001 .001*
PQ (420nm)-Ivocerin (418nm) -.950 6.284 -.151 .880 1.000
PQ (420nm)-CQ (468nm) 19.350 6.284 3.079 .002 .021*
Ivocerin (418nm)-CQ (468nm) 18.400 6.284 2.928 .003 .034*
Table 52. Group-wise comparisons of photoinitiator comparison for Lava Ultimate at 4 mm
0.02 0.01
0.06
0.02 0.02

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5.4.2 Varseo Smile
For photoinitiator (wavelength) comparison, for Varseo Smile at 4 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 53, Figure 163, and Figure 164, CQ [468 nm] had the highest
transmittance (mean = 0.04), followed by PQ [420 nm] (mean = 0.00), Ivocerin [418 nm]
(mean = 0.00), PPD [410 nm] (mean = 0.00) and Lucirin TPO [400 nm] (mean = 0.00).
Table 53 and Figure 164 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PQ [420 nm] (p=0.000), CQ [468 nm] – Ivocerin [418 nm] (p=0.000), CQ [468
nm] – PPD [410 nm] (p=0.001) and CQ [468 nm] – Lucirin TPO [400 nm] (p=0.001)being
significant.
Figure 163. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Varseo Smile at 4 mm
Figure 164. (right) Group-wise comparisons of photoinitiator comparison for Varseo Smile at 4 mm
Pairwise Comparisons of Photoinitiators for Varseo Smile at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
PQ (420nm)-CQ (468nm) 25.850 6.023 4.292 <.001 .000*
Ivocerin (418nm)-TPO (400nm) -1.550 6.023 -.257 .797 1.000
Ivocerin (418nm)-PPD (410nm) -1.850 6.023 -.307 .759 1.000
Ivocerin (418nm)-CQ (468nm) 25.850 6.023 4.292 <.001 .000*
PQ (420nm)-Ivocerin (418nm) .000 6.023 .000 1.000 1.000
PQ (420nm)-TPO (400nm) -1.550 6.023 -.257 .797 1.000
PQ (420nm)-PPD (410nm) -1.850 6.023 -.307 .759 1.000
TPO (400nm)-PPD (410nm) .300 6.023 .050 .960 1.000
TPO (400nm)-CQ (468nm) 24.300 6.023 4.034 <.001 .001*
PPD (410nm)-CQ (468nm) 24.000 6.023 3.985 <.001 .001*
Table 53. Group-wise comparisons of photoinitiator comparison for Varseo Smile at 4 mm
0.00 0.00
0.04
0.00 0.00

150
5.4.3 Ceramic Crown
For photoinitiator (wavelength) comparison, for Lava Ultimate at 4 mm, transmittance was
significantly different between some of the wavelengths, according to the Kruskal-Wallis test
(p<0.001).
As shown in Table 54, Figure 165, and Figure 166, CQ [468 nm] had the highest
transmittance (mean = 0.03), followed by PQ [420 nm] (mean = 0.01), Ivocerin [418 nm]
(mean = 0.01), PPD [410 nm] (mean = 0.00) and Lucirin TPO [400 nm] (mean = 0.00).
Table 54 and Figure 166 present the group-wise comparisons, with only the comparisons CQ
[468 nm] – PQ [420 nm] (p=0.034), CQ [468 nm] – Ivocerin [418 nm] (p=0.007), CQ [468
nm] – PPD [410 nm] (p=0.000) and CQ [468 nm] – Lucirin TPO [400 nm] (p=0.000) being
significant.
Figure 165. (left) Kruskal-Wallis test boxplot of photoinitiator comparison for Ceramic Crown at 4 mm
Figure 166. (right) Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 4 mm
Pairwise Comparisons of Photoinitiators for Ceramic Crown at 4mm
Sample 1-Sample 2 Test Statistic Std. Error Std. Test Statistic Sig. Adj. Sig.a
TPO (400nm)-PPD (410nm) 1.350 6.170 .219 .827 1.000
TPO (400nm)-Ivocerin (418nm) 8.300 6.170 1.345 .179 1.000
TPO (400nm)-PQ (420nm) 11.000 6.170 1.783 .075 .746
TPO (400nm)-CQ (468nm) 29.100 6.170 4.716 <.001 .000*
PPD (410nm)-Ivocerin (418nm) 6.950 6.170 1.126 .260 1.000
PPD (410nm)-PQ (420nm) 9.650 6.170 1.564 .118 1.000
PPD (410nm)-CQ (468nm) 27.750 6.170 4.498 <.001 .000*
Ivocerin (418nm)-PQ (420nm) 2.700 6.170 .438 .662 1.000
Ivocerin (418nm)-CQ (468nm) 20.800 6.170 3.371 <.001 .007*
PQ (420nm)-CQ (468nm) 18.100 6.170 2.934 .003 .034*
Table 54. Group-wise comparisons of photoinitiator comparison for Ceramic Crown at 4 mm
0.00
0.03
0.01 0.00 0.01

151
5.4.4 Summary
When comparing the transmittance between the different photoinitiators (CQ, PQ, Ivocerin,
PPD, Lucirin TPO) at 4 mm, the following trends were found:
- In general (no difference in material), transmittance % values for CQ [468 nm] >
PQ [420 nm] ≈ Ivocerin [418 nm] ≈ PPD [410 nm] ≈ Lucirin TPO [400 nm].
Statistically significant differences were found between four groups: CQ [468 nm] –
PQ [420 nm] (significance 0.000), CQ [468 nm] – Ivocerin [418 nm] (significance
0.000), CQ [468 nm] – PPD [410 nm] (significance 0.000), CQ [468 nm] – Lucirin
TPO [400 nm] (significance 0.000).
- For Lava Ultimate, transmittance % values for CQ [468 nm] > PQ [420 nm] ≈
Ivocerin [418 nm] ≈ PPD [410 nm] > Lucirin TPO [400 nm]. Statistically significant
differences were found between six groups: CQ [468 nm] – PQ [420 nm]
(significance 0.021), CQ [468 nm] – Ivocerin [418 nm] (significance 0.034), CQ [468
nm] – PPD [410 nm] (significance 0.001), CQ [468 nm] – Lucirin TPO [400 nm]
(significance 0.000), PQ [420 nm] – Lucirin TPO [400 nm] (significance 0.046) and
Ivocerin [418 nm] – Lucirin TPO [400 nm] (significance 0.028).
- For Varseo Smile, transmittance % values for CQ [468 nm] > PQ [420 nm] ≈
Ivocerin [418 nm] ≈ PPD [410 nm] ≈ Lucirin TPO [400 nm]. Statistically significant
differences were found between four groups: CQ [468 nm] – PQ [420 nm]
(significance 0.000), CQ [468 nm] – Ivocerin [418 nm] (significance 0.000), CQ [468
nm] – PPD [410 nm] (significance 0.001) and CQ [468 nm] – Lucirin TPO [400 nm]
(significance 0.001).
- For Ceramic Crown, transmittance % values for CQ [468 nm] > PQ [420 nm] ≈
Ivocerin [418 nm] > PPD [410 nm] ≈ Lucirin TPO [400 nm]. Statistically significant
differences were found between four groups: CQ [468 nm] – PQ [420 nm]
(significance 0.034), CQ [468 nm] – Ivocerin [418 nm] (significance 0.007), CQ [468
nm] – PPD [410 nm] (significance 0.000) and CQ [468 nm] – Lucirin TPO [400 nm]
(significance 0.000).

152
Chapter Five: Discussion
The present study evaluated the transmittance of visible light (mainly violet [380-450 nm]
and blue [450-500] light) through two additively manufactured permanent CAD-CAM resin
materials (printed) for definitive restorations in comparison with one subtractively
manufactured CAD-CAM resin materials (milled) as a function of material and a function of
thickness.
The null hypothesis that “there is no difference in the irradiance of transmitted curing light
between the additively manufactured permanent CAD-CAM resin materials (printed) for
definitive restorations in comparison with the substractively manufactured CAD-CAM resin
materials (milled)” and that “there is no difference in the irradiance of transmitted curing
light between the different thicknesses of the materials tested” were rejected.
In previous studies the overall transmittance of glass ceramics, resins and zirconia materials
was evaluated. In some studies,(240, 241) transmittance of light glass ceramics was higher than that
of zirconia materials.(240-242) Other studies,(243) evaluated transmittance of light through resins and
ceramic materials, but not through zirconia. As clearly demonstrated on their research, for
polished specimens, affiliation to a certain material category did not allow conclusions to be
drawn regarding the translucency qualities of a material. Within the different material classes,
every tested material obtained statistically different values, so no conclusions could be driven
about the idea if resins or ceramics transmitted more light. What they found out was,
however, that in general, the translucency of dental ceramics is influenced by factors such as
crystalline structure, grain size, pigments, as well as number, size, and distribution of defects,
and porosity.(137, 243, 244)
In our study, we did not compare resins to ceramics or zirconia, but we compared different
types of CAD CAM resin materials advocated for definitive restorations with each other and
at different thicknesses. The results of the present study confirm the idea that there are
differences in transmittance of light between different materials and at different material
thicknesses.

153
In dentistry, the esthetic component of restorations plays an important role. The most important
factors to consider for esthetics in restorative dentistry is color and translucency. The esthetic
outcome of a restoration depends on the interaction of light with the restorative material, to
generate the color, translucency and opalescence desired. (245)
Spectrophotometry is a commonly used method to quantitatively measure color and
translucency in dentistry.(246-248) Different parameters are used to describe translucency, such as
the contrast ratio or the translucency parameter, making it difficult for clinicians to compare
studies.(249-251) Moreover, these parameters are not applicable to the direct measurement of
translucency and cannot be used below 50% transmission.(6, 252, 253) That is why in this study the
absolute translucency was determined to obtain meaningful and comparable values. For the
same reason, each specimen was first measured with both sides polished to obtain translucency
values that depend only on the material composition. This standardization prevented
misinterpretations of low T% values due to the roughness derived from the printing or milling
unit, even though the restoration is always rough on one side in vivo.(243)
The tested materials were chosen because of their recent launch into the market and curiosity
among clinicians; however, little information can be found about their optical properties. The
transmission of light in these materials regarding their composition, thickness and wavelength,
as well as the relationship between the transmission of light and material’s translucency and
esthetics is discussed in the following paragraphs.

154
1. Transmittance of light related to material
In general, light transmittance of dental materials, especially dental ceramics, is influenced by
factors such as crystalline structure, grain size, pigments, as well as number, size, and
distribution of defects, and porosity.(10,11) If the crystals are smaller than the wavelength of visible
light (400 to 700 nm) the glass will appear transparent; however, if the crystals are bigger than
the wavelength of visible light (400 to 700 nm), light scattering and a diffuse reflection will
take place, and the material will appear opaque.(243, 246)
Lieberman et al(254) stated that the amount of light passing through ceramics and zirconia is
generally determined by a complex combination of parameters, including residual porosity,
grain size, primary particle size, additives such as alumina and sintering.(241, 242, 255, 256) For
example, in zirconia and alumina ceramics, the high concentration of alumina determines
high transmittance values.(254)
Regarding light transmittance in resins, as with the ceramics, numerous parameters play a role,
for example, thickness, filler particles, resin matrix composition, polymerization, and aging.(6, 7)
Moreover, the translucency seems to be material specific, because no clear correlation among
the mentioned parameters can be found in the latest studies. Especially, the filler size is well
discussed, as almost all authors state that smaller filler size results in higher light transmittance.
(243, 244, 257-259)
In our study, it could be observed that, as a general trend, Lava Ultimate was the material that
presented higher values of transmittance at all thicknesses, followed by Ceramic Crown and
lastly, Varseo Smile. However, it depended on the wavelength studied. The previous findings
apply to all studied wavelengths except for wavelength 468nm (peak absorption value for
Camphoroquinone), where light transmittance values were higher in Varseo Smile group than
in Ceramic Crown group.
One possible reason for this finding is the fact that these materials are very different in
composition: Lava ultimate is a material whose filler is made up of nano-ceramic fillers (silica
nanomers of 20 nm diameter, and zirconia nanomers of 4 to 11 nm diameter) while Varseo
Smile and Ceramic Crown fillers, although not widely disclosed by the manufacturers, are
basically inorganic filers much bigger in size, around 0.7 – 0.9 micrometers. It is known that
large particles scatter more light than small ones. This might be a plausible reason why light

155
transmission values are higher in Lava Ultimate (less scattering, more transmission) and lower
in Varseo Smile and Ceramic Crown (more scattering, less transmission).
Some authors(260) studied the transmittance of light through resin-based composites, finding out
that light transmittance is ultimately determined by the difference between the refractive
indices (RI) of the filler and the organic matrix.(252) When the refractive indices of both phases
(inorganic and organic) are very close, there is a high light transmission and the material
appears highly translucent.(252, 261) Also, the type of filler particle, its size and its relationship to
the matrix composition may play a very important role in the transmission of light.(243) As
mentioned above, in our study, it could be observed that, as a general trend, Lava Ultimate was
the material that presented higher values of transmittance at all thicknesses, followed by
Ceramic Crown and lastly, Varseo Smile.
Another plausible reason for the difference in transmittance of light between Lava Ultimate,
Varseo Smile and Ceramic Crown might be the difference and/or similarity between the
refractive indices (RI) of the fillers and the organic matrix of each material. Probably, the
refractive index (RI) of the filler in Lava Ultimate might be very similar to the RI of the matrix
(high light transmission), while in Varseo Smile and Ceramic Crown the refractive index (RI)
of the filler might be very different from the RI from the matrix (high scattering and low light
transmission).

156
2. Transmittance of light in function of material thickness
Regarding the influence of the parameter “thickness,” it is widely demonstrated that changing
(by increasing) the thickness of a material, normally results in a large decrease in translucency.
However, it is also material-dependent: the change in translucency when changing thickness
varies in respect to the material used or studied.(254)
The literature shows that the transmittance of ceramics, resins and zirconia materials is also
significantly influenced by their thickness. Transmittance is inversely related to the thickness
of the ceramic layer to be traversed by a light beam: the thicker the material is, the lower the
transmittance,(242, 254) the thinner the material is, the higher the transmittance. Thicker materials
appear more opaque while thinner materials appear more translucent. In previous studies,(240, 242,
254) the transmittance of blue light through glass ceramics was higher than for zirconia
materials. However, they found out that at thicknesses of 2.5 mm or more, there was almost
no difference between glass ceramics and monolithic zirconia.(240-242, 254, 256)
Awad et al(243) studied the influence of sample thickness in resin and ceramic materials, finding
out that doubling the thickness of the material sample resulted in a large decrease in
translucency (on average 14.59 %). However, this trend was found for resins and ceramics,
with no difference between them: no substance class seemed to be more strongly affected
than others.(243, 248, 251, 262)
The results of the present study confirm the idea that there are differences in transmittance of
light between different thicknesses. As a general trend, our study pointed out that light
transmittance in CAD CAM resin materials used for definitive restorations was influenced by
the thickness of the material. The results demonstrated that 1 mm thickness samples were the
ones with higher transmittance values (for all materials tested), followed by 2 mm, 3 mm and
finally 4 mm samples.
If looking at the transmittance of light between the different thicknesses (1 mm, 2 mm, 3 mm
and 4mm) for the different materials separately (Lava Ultimate, Varseo Smile and Ceramic
Crown), it could be observed the same trend as stated previously: 1 mm was the thickness
that presented higher values of transmittance for all materials, followed the 2 mm thickness
group, 3 mm thickness group and lastly 4 mm thickness group (for all wavelengths studied).

157
Our findings are also in agreement with those found by Lucena et al(260), who stated in their
study that, there is a significant effect from sample thickness on the optical behavior of the
resin-based composites that they evaluated: as thickness increased, the transmittance
decreased, and absorbance and scattering increased. At the same time, as thickness decreased,
the transmittance increased, and absorbance and scattering decreased.(260)
Other authors(242), who studied the amount of light (360–540 nm) passing through shaded
zirconia with respect to material thickness, exposure distance, and different curing modes,
came up with results that were on the same page as the ones in our study: they found out that
that material thickness had a significant impact on the transmitted irradiance. They were also
in accordance with previous studies that investigated the translucency of ceramic materials,(254)
and confirmed that material thickness significantly influences the results.
Different investigations have reported different correlations between the translucency and the
thickness of glass-based ceramics.(242) While one study found that the translucency of ceramic
was linearly related to the thickness,(260) others reported an exponential increase in the
transmission of light with a decrease in thickness.(241, 242, 254-256, 260) Therefore, when using LCU
light for bonding and cementing restorations, accurate knowledge of the relationship between
irradiance and thickness is main importance in order to improve the long-term stability of
ceramic restorations.

158
3. Translucency related to wavelength
Light (visible light) is a type of electromagnetic radiation within the section of the
electromagnetic spectrum observed by the human eye. When a light beam goes through a
medium, it hits the particles existing in them. Due to this phenomenon, some light rays get
absorbed while a few get scattered in various directions. The irradiance of the scattered light
rays depends on the particles’ size and wavelength.(263)
When light passes from one medium to another, e.g., from air into a glass of water, then a
part of the light is absorbed by particles of the medium, preceded by its subsequent radiation
in a particular direction. This phenomenon is termed as scattering of light. The irradiance of
scattered light depends on the size of the particles and the wavelength of the light.(263)
Shorter wavelengths scatter more due to the waviness of the line and its intersection with a
particle. The wavier the line, the more the chance it intersects with a particle. On the other
hand, longer wavelengths are straighter, and the chances of colliding with the particle are
less, so the chances of scattering are less.(263)
In simpler terms, the light of a shorter wavelength is scattered much more than the light of a
longer wavelength. If “p” is considered as the probability of scattering and “λ” is the
wavelength of radiation, then it is given as:(263)
The probability for scattering will give a high rise for a shorter wavelength, and it is inversely
proportional to the fourth power of the radiation wavelength.(263)
It is similar to the idea of the light in its interaction with the sky and the environment: the sky
appears blue because of this scattering behavior. Light at shorter wavelengths—blue and
violet—is scattered by nitrogen and oxygen as it passes through the atmosphere. Longer
wavelengths of light—red and yellow—transmit through the atmosphere. This scattering of
light at shorter wavelengths illuminates the skies with light from the blue and violet end of
the visible spectrum.(263)

159
In our study, the different materials and thicknesses were evaluated at 5 different
wavelengths: 468nm (peak absorption value for CQ), 420nm (peak absorption value for PQ),
418 nm (peak absorption value for Ivocerin) and 410 nm (peak absorption value for PPD) and
400 nm (peak absorption value for Lucirin TPO). Considering these ideas of the interaction
of light and its wavelengths with the environment, some conclusions can be drawn in
reference to the results of our study. In our research we found out that for all materials and all
thicknesses studied, the higher transmittance values were achieved when longer wavelengths
were used: the transmittance of light was highest for all materials and all thicknesses at
longer wavelengths (468 nm – CQ) and lowest at shorter wavelengths. Our results were in
accordance with other studies,(260) in which they evaluated optical properties, translucency and
opalescence parameters of one-shaded resin-based composites: they found out that the
spectral behavior related to transmittance (T%) increased with wavelength, showing higher
values for long wavelengths and lower values for shorter wavelengths. The evaluated
materials mainly scattered and absorbed blue light (shorter wavelength of visible light), while
the maximum transmittance (T%) was for the longer wavelengths. The spectral distribution
pattern related to scattering (S) and absorption (K) showed a maximum value at shorter
wavelengths, showing higher values for shorter wavelengths and smaller values for longer
wavelengths.(260)

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4. Light transmittance, translucency and esthetics
In dentistry, the esthetic component of restorations plays an important role. The esthetic
outcome of a restoration depends on the interaction of light with the restorative material, in
order to generate the color, translucency and opalescence desired.(243)
It is important to bear in mind that the final appearance of a restoration depends on many
factors, not only color, but translucency, opalescence and metamerism too. It is believed that
the clinical esthetic success of a restoration basically depends on the final color, but that’s only
one of the factors to consider. The most important factors to consider for esthetics in restorative
dentistry is color and translucency. Color is usually described according to the Munsell color
space in terms of hue, value, and chroma. Hue is the attribute of a color that enables the
clinician to distinguish between different families of color, value indicates the lightness of a
color and chroma is the degree of color saturation. When color is determined using the Munsell
system, value is determined first followed by chroma, and hue is determined last by matching
with shade tabs of the value and chroma already determined.(245)
However, to produce a highly esthetic and mimetic restoration, translucency is a key factor too.
Human teeth are characterized by varying degrees of translucency, which can be defined as the
gradient between transparent and opaque. Transparency is defined as the physical property
allowing light to pass through the material without appreciable scattering of light. Translucency
allows light to pass through, by scattering the photons. In other words, a translucent material
is made up of components with different indices of refraction. A transparent material is made
up of components with a uniform index of refraction. Transparent materials appear clear, with
the overall appearance of one color, or any combination leading up to a brilliant spectrum of
every color.(245) In order to measure the translucency of a material, many parameters, such as
the Translucency Parameter (TP) or the Transmission Coefficient (TC) can be used. There is
no consensus in the literature regarding which parameter should be used, and is difficult to
standardize them and compare studies that used different parameters. (245)
To optimize esthetics, it is important that the translucency of restorative materials is predictable
for a given dental restoration. In some reports,(238, 264) the translucency of composite resins
increased exponentially as the thickness decreased. In the present study, a correlation between
translucency and thickness was also established with a high correlation for both milled and
printed materials, which agrees with the results of studies on dental composite resins,(265, 266) in

161
which they concluded that the range of translucency in ceramics at clinically relevant
thicknesses resulted from different crystalline compositions. The results of the present study
also confirmed the variations in the translucency derived from the type and composition of
resin materials. Moreover, a significant increase in translucency was also found because of the
decrease in thickness.
The opposite property of translucency is opacity. Materials which do not transmit light are
called opaque. Many such substances have a chemical composition which includes what are
referred to as absorption centers. They absorb certain portions of the visible spectrum while
reflecting others. The frequencies of the spectrum which are not absorbed are either reflected
or transmitted for our physical observation. This is what gives rise to color.(267)
Generally, increasing the translucency of a restoration lowers its value because more light goes
through the material, and less light returns to the eye. With increased translucency, light can
pass the surface and is scattered within the restoration. The translucency of enamel varies with
the angle of incidence, surface texture and luster, wavelength and level of dehydration.(268)
Moreover, two colors that appear to match under a given lighting condition but have different
spectral reflectance are called metamers, and the phenomenon is known as metamerism. The
problem of metamerism can be avoided by selecting a shade and confirming it under different
lighting conditions, such as natural daylight and fluorescent light.(245)
On the other hand, opalescence is the phenomenon in which a material appears to be of one
color when light is reflected from it and of another color when light is transmitted through it.
A natural opal is an aqueous disilicate that breaks transilluminated light into its component
spectrum by refraction. Opals act like prisms and refract different wavelengths to varying
degrees.(268) The shorter wavelengths refract more and require a higher critical angle to escape
an optically dense material than longer wavelengths. The hydroxyapatite crystals of enamel
also act as prisms. Wavelengths of light have different degrees of translucency through teeth
and dental materials. When illuminated, opals and enamel will transilluminate the reds and
scatter the blues within their body; thus, enamel appears bluish even though it is colorless. The
opalescent effects of enamel brighten the tooth and give it optical depth and vitality.(269)
Even our study didn’t study the esthetic effect of the tested materials, by studying the
transmission of light we can get so some thoughts regarding which material would be more

162
esthetic. As mentioned above, Lava Ultimate is a milled material with smaller filler particles
than Varseo Smile and Ceramic Crown. Moreover, transmittance of light is higher in Lava
Ultimate than in the other two materials, so, it is a more translucent material. For these reasons,
Lava Ultimate might be more adequate when trying to match more translucent teeth while
Varseo Smile and Ceramic Crown might be used to match more opaque type of teeth.
Moreover, due to the filler size, probably, Lava Ultimate will also be an easier to polish material
than the additively manufactured ones, resulting in esthetic differences at the surface texture of
the materials.

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5. Degree of conversion
The degree of conversion of resin cements and adhesives depend on many factors, mainly: the
microstructure of the material, the thickness of the restoration, the type of cement used, the
LCU parameters and the wavelength used.
5.1 Material microstructure:
Light transmittance of dental materials, especially dental ceramics, is influenced by factors
such as crystalline structure, grain size, pigments, as well as number, size, and distribution of
defects, and porosity.(270, 271) Regarding light transmittance in resins, as with the ceramics,
numerous parameters play a role, for example, thickness, filler particles, resin matrix
composition, polymerization, and aging. Many authors have found that the material
microstructure affects the amount of light reaching the cement, thus reducing its DC. For
example, it has been found out(272-276) that a higher DC is achieved when using high-glasscontent ceramics compared with polycrystalline ceramics (high matrix content and low filler
content), and when using ceramics with smaller particles in the filler in lieu of big particles.
Moreover, other author(277) showed that using a high-chroma ceramic can negatively influence
polymerization(277) because the pigments can absorb light, affecting its reach to the cement.(278)
The materials used in our study are very different in composition: Lava ultimate is a material
whose filler is made up of nano-ceramic fillers (silica nanomers of 20 nm diameter, and
zirconia nanomers of 4 to 11 nm diameter) while Varseo Smile and Ceramic Crown fillers,
although not widely disclosed by the manufacturers, are basically inorganic filers much
bigger in size, around 0.7 – 0.9 micrometers. This influences the amount of light
transmittance, as Lava Ultimate was the material that presented higher values of
transmittance at all thicknesses, followed by Ceramic Crown and lastly, Varseo Smile. This
might, consequently, affect the DC of the cement beneath the material used. Probably, due to
the differences in light transmittance due to differences in material microstructure, for the
same color and thickness, cements and adhesives used beneath Lava Ultimate might achieve
higher DC than cements and adhesives used in conjunction with Ceramic Crown or Varseo
Smile.

164
5.2 Thickness:
Many studies have found out that the DC can be heavily affected by the thickness of the
restorative material:(110, 279, 280) Some authors(109) found a statistically significant decrease in DC
related to the increase in ceramic thickness but only in the case of dual-cured cements. Other
authors(281-283) found a decrease in DC in both light- and dual-cured cements with an increase in
ceramic thickness. Some researchers found out a higher DC in light-cured cement than in
dual-cured cement.(281-283)
In our study, when comparing the transmittance of light between the different thicknesses
without taking into consideration the material, it could be observed that, as a general trend, 1
mm was the thickness that presented higher values of transmittance for all materials, followed
by the 2 mm thickness group, 3 mm thickness group and lastly 4 mm thickness group (for all
wavelengths studied).
It can be assumed, regarding past literature, that the thicker the restorative material used, the
least light transmittance through the sample and the DC of the underlying cement will be less.
From a clinical standpoint, would be reasonable trying to keep the thickness of the
restorations thin enough the keep high transmittance values, but always assuring to fulfil the
minimum thickness recommended by the manufacturer for optimal flexural strength.

165
5.3 Type of cement:
Another factor considered and evaluated in some studies in relation with the DC was the type
of cement used. The type of cement significantly influenced the DC values, as demonstrated
in many studies. Many authors(108, 109, 128, 131) observed higher DC values when light-cured cements
were used compared to dual cements.(129, 131) supporting the use of light-cured cement in
ceramic and resin restorations. Although studies comparing light-cured and dual-cured
cements are limited, there are publications supporting light-cured cements for ceramic
restorations of different thicknesses.
Regarding the use of dual- or light- cured cements, some authors indicated that the dualcuring cement should be used carefully when CAD/CAM restorations thicker than 1.5 mm
are employed, because 2-mm-thick materials exhibit lower DC%.(241) The light reaching the
underlying cement may be less than required depending on the composition and thickness of
the CAD/CAM composite material.(241) Previous studies have already reported an inverse
relationship between the thickness of ceramic-based restorations and DC%.(109, 117, 118, 284-287)
Other authors(288) concluded that ceramics with thicknesses of 0.5, 1.0, and 1.5 mm did not
have a significant effect on the light-cured resin cement DC compared with the control group,
recommending light-cured cement when the restorative material was <1.5 mm thick and
dual-cured cements when >1.5 mm. (288) Other authors(289) did not observe statistically
significant differences in the DC of light- vs dual-cured cements under ceramics with
thicknesses of 0.5, 0.7, and 1 mm, indicating that polymerization of the resins was adequate
when the ceramic material was interposed, but started observing differences in DC starting at
1.5 mm thickness. (289)
Although in our study we did not take into consideration the cement used, in terms of type or
cement or activation mode, it could be stated as a general recommendation that it would be
better trying to use light-cured cements rather than dual-cure cements to achieve higher
values of DC. However, to use light-cured cements, the thickness of the restoration should be
considered, to assure enough light irradiance reaching the cement. If the thickness of the
restoration is above 1.5 – 2 mm, it is recommendable to use a dual-cured cement to provide
an adequate degree of conversion of the cement. Above these thicknesses, the amount of
curing light transmitting through the restoration is low enough not to provide enough DC to
the cement for light-cured cements.

166
5.4 Light curing units parameters and wavelengths:
A reduction in DC may also occur because of the photoactivation specific process.(290) The
factors to be considered are the light irradiance,(103, 109) the LCU wavelength (must be coincident
with photoinitiators), and the activation protocols.(291) Some authors(109) reported DC values
below 35%, which are clinically unacceptable, by the use of a short irradiation time and low
power. It is very important to use LCU’s working properly, with high irradiance values, for
the recommended time and in the correct wavelength.
The type of LCU plays an important role in the polymerization of resinous cements. Several
studies have reported an increase in DC when they are light-cured with an LED LCU in
comparison with other light sources.(277, 278) Polywave LCU’s emit light with two or more
wavelength ranges, providing advantages, especially in cases where there is more than one
photoinitiator. These LCU’s are generally recommended for their ability to activate a wide
range of photoinitiators.(292, 293)
In our study, many different wavelengths were tested for each material. It is important to bear
in mind, as stated by other authors, the LCU should ideally be a polywave LCU, to make sure
it covers the wavelength of any photoinitiator available in dentistry. If the adhesive or cement
being used is activated by a photoinitiator that is out of the wavelength range of the LCU we
are using, the polymerization reaction will not take place.
Also, the irradiance of light of the LCU should be high and ideally, cements and adhesives
containing long wavelengths photoinitiators (such as CQ) should be used in order to achieve
high DC values, because more light transmittance takes place through the restorative
material. However, this may pose an esthetic concern because photoinitiators activated at
long wavelengths (ie CQ) are yellowish in color and less esthetic.
6. Future Perspectives
The amount of light that transmits through a material is of outmost importance in order to know
if the material itself is doable to be used in an adhesive way, how thick the restorative material
can be, which cements should be used (light or dual cured) for each situation and which LCU
should be best used. With the outburst of additively manufactured materials for temporary and
definitive restorations, studies that consider the transmittance of light through these will be
more commonly available.

167
7. Limitations
As any other study, the conducted research also presents some limitations:
1. It is an in vitro study on light transmittance on resin materials: the performance of
these materials in vivo, inside the oral cavity, might be slightly different due to the
presence of other factors, such as saliva. Moreover, the esthetic appearance of a
ceramic or resin restoration is a multifactorial phenomenon: in ceramics, the effect of
the ceramic translucency is dependent also on the color, surface texture of the
veneering ceramic,(266, 294) framework coloring technique,(295-297) and opacity and color of
the luting cement.(298) In the same way, in resins, the effect of the translucency of the
resin material is also dependent on the color, and surface texture,(266, 294) as well as
staining and glazing products used (monolithic restorations),(295-297) and opacity and
color of the luting cement.(240, 298)
2. Another limitation of this study was the fact that shade and chroma was not taken into
consideration and was not studied. All the specimens in this study were same shade
color. However, some authors,(242) found out that, the darker the shade, the lower the
irradiance passing through. Unshaded ceramics were observed to have the higher
irradiance results, regardless of the material thickness and curing conditions (mode,
distance).(299) The authors observed that there are differences in light irradiance and
translucency at differently shaded ceramic materials.(299) The authors declared that this
difference may have been due to either more pigmentation in the intense-shaded
ceramic versus the light- and the medium- shaded ceramic or the darker pigmentation
itself. Therefore, the light reflection differed and resulted in significant differences in
the translucency of different shades of ceramic. In our study, all materials were tested
at same color (A1), so the influence of different color and shade could not be
evaluated. The results obtained in this study must be addressed cautiously considering
potential differences in light transmittance between the materials tested if different
shades are evaluated.(242, 299)

168
3. Another limitation of this study is the fact that the distance between the tip of the
curing light and the material sample was not studied nor intervened: the amount of
light transmitting through a material was studied in vitro, with a spectrophotometer,
and the distance between the light source and the sample was kept constant. However,
in clinical practice, the distance between the tip of the LCU and the restorative
material is not always the same, as it is not standardized. Moreover, the amount of
light transmitted through a material may or may not change in relationship to the
distance between the curing light and the material. The effect of distance is not the
same for all LCUs. This reduction in the irradiance received does not follow the
“inverse-square law” because the light from most LCUs is a somewhat focused beam
of light. Some LCUs emit a well collimated beam of light and, for others, the beam
spreads out rapidly. Thus, manufacturers should report the radiant exitance not only at
the light tip, (tip irradiance), but also the irradiance delivered at clinically relevant
distances up to 10 mm away. (300, 301) Ideally, the light-curing tip unit should be in direct
contact with the restoration's surface. (111) However, sometimes preparation design does
not allow the polymerization within this distance. (111)Distances of more than 8 mm
between light source and the bottom of the proximal cavity have been demonstrated,
(111) and clinical factors such as the accessibility of the light source, the direction of the
light, cavity depth and intervening tooth tissue may limit depth of cure. (111) As the
distance from the light tip increases, the irradiance received declines. (107, 218, 300, 302-304)
4. A limitation of this study was also the presence of the base and its supports beneath
the printed specimens when cured with the Sprintray Pro Cure 2, as well as the
position of the sample when cured and the condition of the curing unit.
a. The presence of the base and its supports may have interfered on the
irradiance of the curing light that reached the samples, decreasing it. At the
same time, this might have had an influence on the DC of the samples and
affect the amount of light transmitting through the samples (when tested in the
spectrophotometer). Moreover, the thickness of the base and the number of
supports might also have had influence on the DC of the material itself. A

169
decreases DC might have influenced the material microstructure and,
consequently, the transmittance of light through it.
b. The position of the sample on the curing unit might also have had an
influence. Although the curing unit emits light from different areas, most of
the light is emitted from the bottom part of the unit, beneath the tray where the
sample is sitting on. On our study, the base of the samples was sitting on the
tray at the bottom of the curing unit, followed by the supports and finally the
sample. The position of the sample and a change of its orientation might have
had an influence on the amount of light reaching the sample, and
consequently, on its DC and on its light transmittance.
c. The condition of the curing unit also plays a role on the DC and final
microstructure of the printed materials. The hours of use of the LEDs and the
condition (cleanliness and use deterioration) of the transparent tray where the
objects are positioned to cure may influence the irradiance of light reaching
the objects and consequently its DC and possibly the transmittance of light
through them.
5. In this study we did not consider other factors related to LCU’s, such as “light beam
irradiance uniformity” and “light beam spectral uniformity”. Regarding “light beam
irradiance uniformity”, according to ISO 10650 standard, (305) the irradiance of the
light beam should be uniform through the whole irradiance tip. However, this does
not always happen. Normally, there is a huge difference between the single averaged
irradiance value provided by the ISO 10650 standard(305) and the information provided
by a beam profile from the same LCU. Ideally, the radiant power should be divided
by the optical tip area to produce an averaged radiant exitance. However, this
information can be misleading, because due to the disposition of the LEDs on the
lamp, the average radiant exitance might not be the true irradiance of the LCU. It is
very common to find “hot spots” of high radiant exitance above the average radiant
exitance where the LEDs are, while the other regions where the LEDs are not present,
the light output is lower.(300, 301)

170
6. Regarding “light beam spectral uniformity”, Price et al (218, 300, 303) also demonstrated that
the design of LCUs may pose a difference on the light irradiance values generated by
the LCU, especially in polywave LED LCUs. Polywave LCUs are able to emit light in
many different wavelength spectra. This is true, however, not all the types of light
(violet and blue for instance) are emitted uniformly. Depending on the design of the
LEDs on the tip of the LCU, the irradiance and distribution of light for a specific type
of light differs. The beam profile of a polywave length peak LED curing light is not
uniform, having a different number of violet light and blue light LED emitters in the
LCU. When this occurs, the light beam spectral light output is not uniform, and “hot
spots” of high irradiance are evident. In consequence, the resulting emitting light is
not well mixed, which means that, the irradiance of light and the areas of irradiance
on the tip are not the same. In our study, the light was uniform because it was emitted
by a transmittance spectrophotometer, however, it is important to know that, even if
using a polywave lamp, the amount of light emitted for different wavelengths, as well
as its disposition, is not uniform, and this might vary the values of transmitted light
through a material.(107, 218, 300, 302-304)

171
Chapter Six: Conclusions
- Light transmittance is affected by three main parameters: the material, the thickness of
the material, and the wavelength of the light.
- The subtractively manufactured material tested (Lava Ultimate) transmitted more
light, at all thicknesses tested, than the additively manufactured materials tested
(Varseo Smile Crown Plus and Ceramic Crown).
- For all materials tested, transmittance is thickness dependent. The thinner the
material, the more light transmittance.
- Transmittance is wavelength dependent. For all materials and all thicknesses studied,
the longer the wavelength, the higher transmittance. Irradiant light at 468 nm was
transmitted the most, while irradiant light at 400 nm was transmitted the least.

172
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Abstract (if available)

Abstract Purpose: To evaluate the transmittance of light through CAD CAM resin materials for definitive restorations that were manufactured additively (printed) or subtractively (milled) as a function of material, thickness, and wavelength.

Material and methods: A total of 120 flat, squared samples were fabricated from three different CAD CAM resin materials for definitive restorations (milled: Lava Ultimate (3M, St. Paul, MN, USA); printed: Varseo Smile Crown Plus (BEGO, Bremen, Germany) and (Ceramic Crown Sprintray, Los Angeles, CA, USA)). For each material, specimens of different thicknesses (1 mm , 2 mm, 3 mm and 4 mm with n=10 per thickness) were fabricated and polished. Transmittance of light at different wavelengths (400 nm, 410 nm, 418 nm, 420 nm, 468 nm) was measured using a spectrophotometer equipped with a 150 mm integrating sphere (Perkin Elmer, Waltham, MA, USA). Data was analyzed using Kruskal- Wallis and Mann-Whitney tests with Bonferroni correction (α=.05).

Results: The transmittance of light was higher for Lava Ultimate, followed by Varseo Smile Crown Plus and Ceramic Crown. Significant differences were observed between the thicknesses tested: 1 mm thickness transmitted the highest amount of light while 4 mm thickness transmitted the lowest. The higher transmittance values were achieved when longer wavelengths were used: irradiant light at 468 nm transmitted the most, while irradiant light at 400 nm transmitted the least.

Conclusions: Light transmittance can be affected by the material used, the thickness of the object, and the wavelength of the light. Light transmittance through permanent CAD/CAM resin materials was reduced for printed materials, increasing thickness, and lower wavelengths.

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Creator Lázaro Pascual, Alberto (author)

Core Title Influence of material type, thickness, and wavelength on transmittance of visible light through additively and subtractively manufactured permanent CAD-CAM resin materials for definitive restorations.

School School of Dentistry

Degree Master of Science

Degree Program Biomaterials and Digital Dentistry

Degree Conferral Date 2024-05

Publication Date 02/22/2024

Defense Date 01/18/2024

Publisher Los Angeles, California (original), University of Southern California (original), University of Southern California. Libraries (digital)

Tag 3D printing,additive manufacturing,CAD/CAM,CAD/CAM Resin,composite resin,digital dentistry,Light Transmittance,Material Thickness,OAI-PMH Harvest,permanent crown,subtractive manufacturing

Format theses (aat)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Phark, Jin-Ho (committee chair), Duarte, Sillas (committee member), Knezevic, Alena (committee member)

Creator Email albertlazaropascual@gmail.com,lazaropa@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-oUC113839152

Unique identifier UC113839152

Identifier etd-LzaroPascu-12668.pdf (filename)

Legacy Identifier etd-LzaroPascu-12668

Document Type Thesis

Format theses (aat)

Rights Lázaro Pascual, Alberto

Internet Media Type application/pdf

Type texts

Source 20240226-usctheses-batch-1126 (batch), University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright.

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA

Repository Email cisadmin@lib.usc.edu