University of Southern California Dissertations and Theses

Adhesive performance of hybrid CAD/CAM materials. Chapter I, Influence of surface treatment on the shear bond strength of hybrid CAD/CAM materials. Chapter II, Luting protocol for novel CAD/CAM m...

(USC Thesis Other)

Adhesive performance of hybrid CAD/CAM materials. Chapter I, Influence of surface treatment on the shear bond strength of hybrid CAD/CAM materials. Chapter II, Luting protocol for novel CAD/CAM m...

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content

ADHESIVE PERFORMANCE OF HYBRID CAD/CAM MATERIALS
CHAPTER I: INFLUENCE OF SURFACE TREATMENT ON THE SHEAR BOND STRENGTH OF
HYBRID CAD/CAM MATERIALS
CHAPTER II: LUTING PROTOCOL FOR NOVEL CAD/CAM MATERIALS

by

Dr. Reham Mohammed Alsamman

A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
CRANIOFACIAL BIOLOGY

May 2021

Copyright 2021 Dr. Reham M. Alsamman
ii
Dedication
I would like to dedicate this work to my family and loved ones, who have supported me throughout my
journey. I wouldn’t have made it this far without you.
To my mother, Sahar A. Brollos, you are always on my mind. I hope I made you proud. RIP
To my father, Mohammed N. Alsamman, for his unconditional love and countless sacrifices.
To my husband, Ali H. Nusair, for his unfailing support and words of encouragement. I could never have
accomplished this without you.
To my children, Jude A. Nusair and Hassan A. Nusair, for bringing joy into my life.
To my sibling, Roaa, Rawabi and Nasser, for supporting me and being there for me whenever I needed.
To my aunt, Mariam A. Brollos, and my mother-in-law, Najat S Sulimani, for helping me when I needed
you the most.
To my family members and best friends, for lifting me up whenever I am down.

iii
Acknowledgments
I would like to express my gratitude to my advisor Dr. Jin-Ho Phark for his guidance and support through
my learning process. He provided me with useful comments and guided me to the right the direction
whenever he thought I needed it. Without his valuable assistance this work would not been completed.

I would like to extend my gratitude to my mentor Dr. Sillas Duarte Jr. for his for his support through my
journey. He consistently challenged me to get out of my comfort zone and push the boundaries to learn
something new. Without his guidance my journey would not be fulfilled.

Beside my advisors, I would like to express my appreciation to my committee members: Dr. Michael Paine
and Dr. Alena Knezevic for their insightful comments, encouragement, and questions that incented me to
widen my research from various perspectives.

Finally, I acknowledge the support of Southern California Clinical and Translational Science Institute (SC
CTSI) and Anita Yau for conducting the statistical analysis. I also gratefully acknowledge the staff, faculty
and colleagues in the Craniofacial Biology Program of the Herman Ostrow School of Dentistry of the
University of Southern California for providing assistance and support.

iv
Table of Contents
Dedication ............................................................................................................................................................... ii
Acknowledgments ................................................................................................................................................. iii
List of Tables .......................................................................................................................................................... v
List of Figures ........................................................................................................................................................ vi
Abbreviations ........................................................................................................................................................ vii
Abstract ................................................................................................................................................................ viii
Chapter I: Influence of Surface Treatment on the Shear Bond Strength of Hybrid CAD/CAM Materials ............ 1
Introduction ....................................................................................................................................................... 1
Objectives of the Study ..................................................................................................................................... 9
Material and Methods ..................................................................................................................................... 10
Sample Preparation .................................................................................................................................... 10
Bonding Procedure ..................................................................................................................................... 10
Artificial Aging .......................................................................................................................................... 12
Shear Bond Strength Testing ...................................................................................................................... 13
Mode of Failure .......................................................................................................................................... 14
Microstructural Characterization ................................................................................................................ 14
Statistical Analysis .......................................................................................................................................... 16
Results ............................................................................................................................................................. 17
Discussion ....................................................................................................................................................... 28
Conclusion ...................................................................................................................................................... 35
Chapter II: Luting Protocol for Novel Hybrid CAD/CAM Materials .................................................................. 36
Introduction ..................................................................................................................................................... 36
Objective of the Study ..................................................................................................................................... 45
Material and Methods ..................................................................................................................................... 46
Sample Preparation .................................................................................................................................... 46
Bonding Procedure ..................................................................................................................................... 47
Artificial Aging .......................................................................................................................................... 48
Shear Bond Strength Testing ...................................................................................................................... 48
Mode of Failure .......................................................................................................................................... 49
Material Characterization ........................................................................................................................... 49
Statistical Analysis .......................................................................................................................................... 52
Results ............................................................................................................................................................. 53
Discussion ....................................................................................................................................................... 65
Conclusion ...................................................................................................................................................... 74
References ............................................................................................................................................................ 75
v

List of Tables
Table 1: Overview and examples of all-ceramic and ceramic-like materials categorized according to their
composition. ............................................................................................................................................ 4
Table 2: Overview of different types of surface treatments, their mechanism and indications. ............. 7
Table 3: Surface treatments protocols ................................................................................................... 11
Table 4: Characteristic and composition of used materials ................................................................... 12
Table 5: List of tested groups classified by aging ................................................................................. 15
Table 6: Mean Shear Bond Strength (MPa) and Standard Deviation (SD). ......................................... 19
Table 7: Summary of 3-way and 2-way ANOVA for SBS conducted at each level of interacting factor20
Table 8: Frequency and percentage of failure mode by group .............................................................. 25
Table 9: Material properties of various cements (6, 40). ...................................................................... 38
Table 10: Bonding protocols for hybrid CAD/CAM materials according to the manufacturer. .......... 42
Table 11: Chemical composition of cements used in the study ............................................................ 47
Table 12: List of tested groups classified by aging ............................................................................... 51
Table 13: Mean shear bond strength (MPa) and standard deviation (SD) ............................................ 55
Table 14: Summary of 3-way and 2-way ANOVA for SBS conducted at each level of interacting factor
............................................................................................................................................................... 56
Table 15: Frequency and percentage of failure mode by group ............................................................ 61
Table 16: Raman shift of functional groups identified as possible chemical interaction. .................... 62

vi
List of Figures

Figure 1: Representation of the surface treatment assigned to each group ........................................... 11
Figure 2: Schematic representation of the study set .............................................................................. 13
Figure 3: Notch-edge configuration for shear bond strength ................................................................ 13
Figure 4: Box plots of shear bond strength in MPa. .............................................................................. 18
Figure 5: Mean (early & late) SBS (in MPa) presented by surface treatment ...................................... 22
Figure 6: Mean (early & late) SBS (in MPa) presented by restorative material. .................................. 24
Figure 7: Mode of failure. ..................................................................................................................... 24
Figure 8: Scanning electron microscopy of hybrid CAD/CAM materials (magnification x10,000) .... 27
Figure 9: Schematic illustration for dental adhesive systems ............................................................... 36
Figure 10: Classification of resin cement .............................................................................................. 39
Figure 11: Schematic representation of the study set ............................................................................ 49
Figure 12: Schematic representation of Raman Spectroscopy components and mechanism of action 50
Figure 13: Box plots of shear bond strength in MPa ............................................................................. 54
Figure 14: Mean (early & late) SBS (in MPa) presented by restorative material ................................. 58
Figure 15: Mean (early & late) SBS (in MPa) presented by luting cement .......................................... 59
Figure 16: Mode of failure .................................................................................................................... 60
Figure 17: Raman spectra of hybrid CAD/CAM materials (Lava Ultimate, LuxaCam Composite and
Cerasmart) ............................................................................................................................................. 64

vii
Abbreviations
ANOVA: Analysis of variance
CAD/CAM: Computer aided designing/computer aided manufacturing technology
CJ: CoJet
CS: CoJet and silane
CS: Cerasmart
LC: LuxaCam Composite
LED: Light emitting diode
LU: Lava Ultimate
MP: Monobond Plus only
NS: No surface treatment
PTFs: Pre-test failures
RNC: Resin nano ceramic
SB: Sandblasting only
SBS: Shear bond strength
SD: Standard deviation
SEM: Scanning electron microscopy
SL: Silane only
SM: Sandblasting and Monobond Plus
SS: Sandblasting and silane

viii
Abstract
Chapter I: Influence of Surface Treatment on the Shear Bond Strength of Hybrid CAD/CAM
Materials

Objective: To establish a strong and durable bond, an appropriate treatment of the respective surfaces is
crucial. Therefore, the aims of this study were: 1) To evaluate the influence of different surface treatments
on the bonding strength between hybrid CAD/CAM materials and universal resin cement system using
notched-edge shear bond strength (SBS) test. 2) To examine the microstructures of different hybrid
materials and the surface changes after applying different surface treatments that contribute to the bonding
performance of the restoration using scanning electron microscopy (SEM).

Materials and Methods: CAD CAM blocks of three hybrid materials (LuxaCam Composite; LC, Lava
Ultimate; LU, and Cerasmart; CS) were sectioned into 2 mm thick slices (N=630), polished with silicon
carbide paper (1200 grit) and cleaned ultrasonically in ethanol for 5 min. Each material was sub-divided
into seven groups (n=30) based on the applied surface treatment (NS: no surface treatment, SB: sandblasting
only, SL: silane only, MP: Monobond Plus only, SS: sandblasting and silane, SM: sandblasting and
Monobond Plus, CS: CoJet and silane). Composite cylinders (Filtek Z250 composite) were fabricated using
a bonding mold inserts and cemented to the CAD CAM slices under standardized load of 1 kg. Universal
bonding agent and universal resin cement (Universalbond and Universalzement) were used for bonding
according to the manufacturer’s instructions and light cured for 20 sec/surface.
Half of each group was tested for early SBS after 24h storage in distilled water at 37 °C, other half was
tested for late SBS after artificial aging by thermo-cycling for 20K cycles at 5 °C-55 °C (dwell time: 30
sec, transfer time: 10 sec) and 6 months of water storage at 37 °C. Notched-edge SBS was measured using
a universal testing machine (Instron 6596) by loading specimens until failure. Failure modes were assessed
with a stereo microscope and reported. Statistical analysis was performed with 3-way-ANOVA model using
Bonferroni post-hoc multiple comparisons with α = 0.05.
ix
Results: Shear bond strength (SBS) of hybrid CAD/CAM materials increased with micromechanical
surface treatments (SB) compared to chemical treatments (SL and MP). Depending on the restorative
material, chemical treatment increased early SBS but it deteriorated after artificial aging. Generally,
combination surface treatments (SS, SM, and CS) performed similarly to SB alone.
Conclusions: Adhesive performance of hybrid CAD/CAM materials is influenced by surface treatment and
deteriorates over time.
Chapter II: Luting Protocol for Novel Hybrid CAD/CAM Materials
Objective: Choosing a proper cement/adhesive system which is chemically compatible with the restorative
material is a critical step for efficient bonding procedure. Therefore, the aims of this study were: 1) To
assess the bonding performance of different luting systems with hybrid CAD/CAM materials using a
notched-edge shear bond strength (SBS) test. 2) To examine the different microstructures of hybrid
CAD/CAM materials and the different chemical components that contribute to their bonding performance
using scanning electron microscopy (SEM) and micro-Raman spectroscopy.
Materials and Methods: CAD CAM blocks of three materials (LuxaCam Composite; LC, Lava Ultimate;
LU, and Cerasmart; CS) were sectioned into 2 mm thick slices (N=540), polished with silicon carbide paper
(1200 grit) and cleaned ultrasonically in ethanol for 5 min. Composite cylinders (Filtek Z250 composite)
were fabricated using a bonding mold inserts, polymerized for 20 sec using LED unit, and cemented to the
CAD CAM slices under standardized load of 1 kg. Each material was sub-divided into six group (n=30)
based on the luting cements (Universalzement, RelyX Ultimate, DuoCem, Multilink Automix, RelyX
Unicem 2, Ketac Cem Plus) which were used according to the manufacturers’ instructions and light cured
for 20 sec/surface.
Half of each group was tested for early SBS after 24h storage in distilled water at 37 °C, other half was
tested for late SBS after artificial aging by thermo-cycling for 20K cycles at 5 °C-55 °C (dwell time: 30
sec, transfer time: 10 sec) and 6 months of water storage at 37 °C. Notched-edge SBS was measured using
x
a universal testing machine (Instron 6596) by loading specimens until failure. Failure modes were assessed
with a stereo microscope and reported. Statistical analysis was performed with 3-way ANOVA model using
Bonferroni post-hoc multiple comparisons with α = 0.05.
Results: SBS of hybrid materials differs depending on the used luting cement. LuxaCam Composite (LC)
performed best combined with Universalzement after artificial aging. Lava Ultimate (LU) had similar late
SBS when bonded with Relyx Ultimate, Duocem and Universalzement. Late SBS of Cerasmart (CS)
reported no significant difference using Multilink Automix, Duocem and Universalzement. Early SBS
presented similar performance for LU and LC with all tested cements except RelyX Unicem 2. CS has
lower early SBS than other two materials. After artificial aging, LU had more stable bonding strength
followed by CS and LC in order.
Conclusions: Depending on the restorative material, the choice of luting cement has a significant effect on
long-term shear bond strength.
Chapter I: Influence of Surface Treatment on the Shear Bond Strength of Hybrid CAD/CAM
Materials
Introduction
Computer-aided designing (CAD)/computer-aided manufacturing technology (1) has become a popular
approach in restorative dentistry in the past years. CAD/CAM offers a standardized manufacturing process
results in a reliable, predictable, and economic workflow for individual and complex restorations in a timely
manner (2). This rapid progression in technology enables the production of CAD/CAM chairside 1-visit
restorations which are particularly attractive for patients and clinicians. Excellent machinability, short
processing times, and good reproduction of details are important for features for a chairside material. The
first functioning chairside CAD/CAM prototype was introduced in the 1980s when Mörmann and
Brandestini introduced the Cerec system (3). Up to date, an increasing number of chairside systems and
restorative materials have been evolving to meet the increased demands for highly aesthetic, biocompatible,
and long-lasting restorations (4).
Generally, all-ceramic and ceramic-like restorative materials can be categorized based on their chemical
composition into 1) glass-matrix ceramics, which consist of nonmetallic inorganic ceramics with a glass
phase; 2) polycrystalline ceramics, which consist of nonmetallic inorganic ceramics without any glass
phase; and 3) resin-matrix ceramics also referred to as “hybrid”, which consist of organic matrix that is
highly filled (> 50% by weight) with inorganic ceramic particles (5). Table 1 provides an overview of all-
ceramic and ceramic-like materials categorized according to the proposed classification and of their
composition and clinical indications according to manufacturer information. A variety of CAD/CAM
restorative materials provide a range of mechanical and optical properties (6, 7). In recent years, dental
manufacturers have been focusing on developing materials with different microstructures which mimic the
physical and mechanical characteristics of natural teeth. Ceramic materials have some physical properties
2
similar to those of human enamel, whereas composite resin materials have characteristics very similar to
those of dentin (6, 7).
In this sense, hybrid ceramics were developed combining the advantageous properties of ceramics such as
durability, biocompatibility and esthetics with the properties of composite resins such as high flexural
strength and low abrasiveness (6, 7). They combine the intermingling of polymers and different ceramics
to achieve the aforementioned goal. The use of industrial polymerization by high pressure and high heat
improves monomer conversion and cross-linked matrix, yielding superior mechanical behavior (6, 7). As
CAD/CAM materials are constantly evolving, clinicians face a complex decision process choosing a proper
restorative material and a correct bonding protocol. The ultimate goal is to optimize the bonding protocol
for hybrid restorative materials based on their microstructure and the chemical compositions rather than
just the overall category as these categories and commercial names do not reflect the correct material-
specific chemical composition.

3
Ceramic Category
Product Name
(Manufacturer)
Composition
Clinical Indications
(according to
manufacturers)
Glass-matrix ceramics
Feldspathic
ceramics
VITA Mark II
VITA TriLuxue forte
VITA RealLife
(VITA Zahnfabrik)
feldspar and quartz with
limited amount of kaolin.
veneers, inlays, onlays,
anterior crowns, and
veneering for
substructures made of
oxide ceramic.
Leucite-reinforced
ceramic
IPS Empress CAD
(Ivoclar Vivadent)
Leucite (35–45 vol%)
distributed into a glassy
matrix.
veneers, inlays, onlays,
anterior and posterior
crowns.
Lithium disilicate
ceramic
IPS e.max CAD
(Ivoclar Vivadent)
Lithium disilicate (70
vol%) incorporated in a
glassy matrix.
veneers, inlays, onlays,
anterior and posterior
crowns, 3-unit bridges
(up to 2
nd
premolar),
veneering for
substructure made of
oxide ceramic.
Zirconia-reinforced
lithium silicate
Celtra Duo
(Dentsply) Glass-ceramic material
enriched with highly
dispersed zirconia (10
wt%)
veneers, inlays, onlays,
anterior and posterior
crowns
VITA Suprinity
(VITA Zahnfabrik)
veneers, inlays, onlays,
anterior and posterior
crowns, implant-
supported crowns
Glass-infiltrated
ceramic

VITA In-Ceram
ALUMINA
VITA In-Ceram
ZIRCONIA
(VITA Zahnfabrik)
Porous oxide ceramic
skeleton (alumina/
zirconia) infiltrated with
lanthanum glass in two
steps firing.
substructures for
crowns and 3-unit
bridges in anterior and
posterior regions.
Polycrystalline ceramics
Alumina
In- Ceram AL
(VITA Zahnfabrik)
Fine-grain crystalline
structure (aluminum
oxide) densely arranged
without glass phase.
primary telescope
crowns, anterior and
posterior crowns, 3-unit
anterior bridges
Zirconia
Katana Zirconia ML
(Kuraray)
Fine-grain crystalline
structure (zirconium
oxide), stabilized by
Yttrium oxide, densely
arranged without glass
phase.
veneers, inlays, onlays,
anterior and posterior
crowns, multi-unit
bridges up to 2 pontics
(used as full-contour or
substructure)
IPS e.max ZirCAD
(Ivoclar Vivadent)
crowns, multi-unit
bridges up to 2 pontics
(used as full-contour or
substructure)

4
Continuation of table from previous page
Ceramic Category
Product Name
(Manufacturer)
Composition
Clinical Indications
(according to
manufacturers)
Resin-matrix ceramics (Hybrid)
Resin Nano
Ceramic
Lava Ultimate
(3M ESPE)
Nano ceramic particles in
form of nanoclusters
bound in highly cross-
linked polymeric matrix.

veneers, inlays, and
onlays
Cerasmart
(GC)
Uniformly distributed
nanoparticles of alumina-
barium-silicate embedded
in polymer matrix
veneers, inlays, onlays,
anterior and posterior
crowns, implant-
supported crowns.
Polymer Infiltrated
Ceramic Network
VITA Enamic
(VITA Zahnfabrik)

Dual network of
feldspathic ceramic (86
wt%) and polymer (14
wt%) consisting of
UDMA and TEGDMA
veneers, inlays, onlays,
anterior and posterior
crowns, implant-
supported crowns.
Composite
Paradigm MZ100
(3M ESPE)
Zirconia-silica ceramic
particles embedded in a
resin matrix; the
inorganic content
comprises more than 60
wt%.
veneers, inlays, onlays,
crowns
Shofu Block HC
(Shofu)
veneers, inlays, onlays,
anterior and posterior
crowns, and implant-
supported crowns.
Table 1: Overview and examples of all-ceramic and ceramic-like materials categorized according to their
composition (5).

A bonded restoration has up to three interfaces: tooth-adhesive interface, adhesive-resin cement interface,
and cement-restoration interface. In some cases, additional layer of adhesive is applied to the restoration
which adds up to the number of interfaces (adhesive-restoration interface). On the other hand, some cements
(self-adhesive cements) do not require the application of an adhesive and therefore have only two interfaces:
tooth-cement interface and cement-restoration interface (8). It is well established that the main adhesive
mechanism to dental substrate is based on micromechanical retention resulting from the formation of a
hybrid layer and resin tags into the etched enamel or dentin (9, 10). There are basically three options for
bonding to dental substrate; removal of the smear layer using an etch-and-rinse approach, modification of
the smear layer using a self-etch approach, or selective etching approach (11, 12). In addition, the benefit
of additional chemical interactions between the dental substrate and chemical component such as functional
5
monomers (e.g 4-META, phenyl-P, and 10-MDP) in the adhesive system have been a focus of many studies
in the past few years (13, 14).
The available information in regard to adhesive mechanism at the restoration-cement interface is based on
micromechanical and/or chemical retention (1, 6, 15). Depending on the class of the material, various
surface treatments have been suggested to improve the bond strength of CAD/CAM restorative materials
to resin cements (8, 16). Micromechanical retention can be achieved by altering the surface texture using
either mechanical or chemical means, resulting in an enlarged surface area and microscopically small
undercuts within the altered surface where the adhesives/cements can flow into and interlock (8, 16).
Hydrofluoric acid (HF) etching, laser etching, sandblasting (airborne particle abrasion), and bur grinding
are examples of surface treatments that provide micromechanical retention. Furthermore, chemical
treatment is suggested to enhance bonding by applying coupling agents, which contain bifunctional
molecules that allow a chemical reaction between the inorganic ceramic and the organic resin cement (17).
The most commonly used agents are silane, which bonds to silica (17)

and MDP containing agents, which
bond to hydroxyapatite and ceramic oxides (13, 18). Table 2 provides an overview about different types of
surface treatments, their mechanism and indications.
Sandblasting (SB) is an airborne particle abrasion method that use aluminum oxide (Al
2
O
3
) to treat the
receptive surface in indeed to improve bond strength by exposing fresh surface, free of contaminants, and
exposing the fillers so become reachable for silanization. It also provides micromechanical retention to the
luting cement by roughen the surface of the restoration (19, 20). Many factors have been reported to affect
the outcome of the airborne particle abrasion procedure such as nature of receptive surface, the type and
size of the particles, the applied pressure and duration (19, 20). Tribochemical coating is another airborne
particle abrasion method that uses Al
2
O
3
particles that are coated with silicon dioxide to embed silica
particles at the surface of metals, polycrystalline materials to be used for the silanization thereby improve
6
bonding (21). This technique is provided by two available systems known as Rocatec and CoJet (3M ESPE,
St. Paul, MN, USA) for laboratory and chairside application.
Silane is known for helping in the compounding of dissimilar materials. One end has a silanol (Si–OH)
functional group where silicon and oxygen atoms react with their correspondents on the surface of the to
be bonded material (17). These bi-functional molecules are capable of forming siloxane ionic bonds (Si–
O–Si) to the silicon–oxygen groups in the silica-based surface by a condensation reaction (17). The other
end has methylacrylate group (–OCH 3), which contains double-carbon bonds, enable it to co-polymerize
with the organic resin matrix by an addition reaction (17). The silane also increases the hydrophobicity and
wettability of the treated surface,

thus enhancing its interaction with the hydrophobic resin cements (22). It
is usually present in the form of a dilute of methacryloxypropyl trimethoxysilane (MPTMS) with 2-5 wt%
alcoholic solutions (17). It is present either as two bottles for hydrolytic activation prior to application, or
as a single bottle in pre-hydrolyzed form, ready for use. It can also be found as a component in primers,
universal adhesives, and resin cements.

7
Surface Treatment Type of Retention Mechanism Indication
Mechanical Surface Treatment
Airborne particle
abrasion
(Sandblasting)
Micromechanical
Application of Al
2
O
3
particles at
certain pressure to create surface
roughness.
Resin composite,
hybrid ceramics,
oxide ceramics,
metals
Airborne particle
abrasion
(Tribochemical
coating)
Micromechanical
Application of Al 2SiO 5

particles
at certain pressure to embed
silica particles at the surface
along with roughening the
surface.
Metals, oxide
ceramics
Laser etching
Micromechanical
Surface modification with the
use of different types of lasers
(CO
2
laser, Nd:YAG, Er:YAG,
Er,Cr:YSGG and Femtosecond
lasers) with power outputs rang
from 400mW- 10W.
Glass-based
ceramics, hybrid
ceramics, oxide
ceramics
Surface grinding Micromechanical
Surface grinding by a diamond
bur to create surface roughness.
Intra-oral repair
of fractured
restoration
Chemical Surface Treatment
Acid etching
(HF aicd)
Micromechanical
Application 5–10% HF,
selectively dissolute the silica
phase causing surface roughness.
Glass-based
ceramics, hybrid
ceramics
Application of silane
product.
Chemical
Formation of siloxane ionic
bonds between a silanol group
with the silica-containing surface
at one end. And co-
polymerization of the
methylacrylate groups with the
resin matrix at the other end.
Glass-based
ceramics, resin
composites,
hybrid ceramics,
metals and metal
oxides.
Application of MDP
containing product.
Chemical
Chemical bond between
phosphoric-acid group and
hydroxyapatite or metal oxides
at one end. And co-
polymerization of vinyl group
with the resin matrix at the other
end.
Glass-based
ceramics, metals
and metal oxides.
Combination Surface Treatment
HF + silane
SB + MDP
SB + silane
Silica coating + silane
Micromechanical
and chemical
Combine two methods; one to
create surface roughness for
mechanical interlocking, other to
form chemical bond with
receptive surface.
Different
combination is
recommendation
based on same
indications
above.
Table 2: Overview of different types of surface treatments, their mechanism and indications.

8
Another chemical component that forms chemical retention is acidic functional monomers which have been
added to self-etch and universal adhesive systems as well as ceramic primers and self-adhesive resin cement
(13, 14). Examples of such molecules are 4-META, phenyl-P, MDP, and di-HEMA–phosphate; each has a
different self-etching capacity and affinity to form a chemical bond with different substance (14).
Furthermore, 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) has been identified as being
capable of establishing a very intensive and stable chemical interaction with hydroxyapatite (at optimal
concentration of 5-10%) forming MDP-Ca water-insoluble salts contribute to the bond strength (14, 18).
The MDP molecule retains a phosphoric-acid group at one end of the molecule, which serves as an adhesion
promoting agent for hydroxyapatite or metal oxides such as alumina and zirconia. The other end retains a
vinyl group which facilitates polymerization with double- carbon bonds in the organic resin matrix (13, 14).
According to the literature, different surface treatments may be recommended for different ceramic
materials (21, 23-25). In the case of glass ceramics, hydrofluoric acid etching followed by the application
of silane coupling agent has been identified as the gold standard bonding protocol. Up to date, the bonding
of hybrid CAD/ CAM material is still a subject of conflict (23). The importance of micromechanical
retention in bond durability of hybrid CAD/CAM materials is well established (16). However, there is still
a question on whether the combination of micromechanical and chemical surface treatments of the
restoration is more effective than micromechanical treatment alone. Different recommendations have been
suggested by literature regarding the application of coupling agents after micromechanically treating the
hybrid restoration (16, 26). As adhesive bonding of the restoration is an important step determining its
longevity (19, 27), establishing an evidence-based bonding protocol is essential. A comprehensive
understanding of the effect of the restorative material selection, surface treatment and luting cement on the
bonding performance of hybrid CAD/CAM restorations is necessary as it will help the clinician in making
decisions toward successful, long-lasting restorations.

9
Objectives of the Study
To establish a strong and durable bond at the restorative interface, an appropriate treatment of the respective
surfaces is crucial. Therefore, the aims of this study were:
1) To evaluate the influence of different surface treatments on the bonding strength between hybrid
CAD/CAM materials and universal resin cement system using notched-edge shear bond strength
(SBS) test.
2) To examine the surface changes after applying different surface treatments that contribute to the
bonding performance of the restoration using scanning electron microscopy (SEM).
The null hypotheses of this investigation were:
1) Surface treatment has no significant effect on SBS.
2) Restorative material has no significant effect on SBS.
3) Aging has no significant effect on SBS.

10
Material and Methods
Sample Preparation
Six hundred and thirty square specimens were fabricated using three hybrid CAD/CAM materials (Lava
Ultimate; LU, LuxaCam Composite; LC and Cerasmart; CS). The blocks were sectioned into 2 mm
thickness slices using a precision low-speed diamond saw (Isomet 1000; Buehler, Lake Buff, IL, USA)
under distilled water. The bonding surfaces of all the specimens were metallurgically polished with silicon
carbide paper (1200 grit: Carbimet 2, Buehler). The specimens were ultrasonically (PC3; L&R Ultrasonic,
Kearny, NJ, USA) cleaned in ethanol for 5 min, then rinsed with distilled water for 30 sec and air-dried.
Composite cylinders (Filtek Z250 composite, 3M ESPE, St. Paul, MN, USA) were fabricated using bonding
mold inserts (Ultradent Products, South Jordan, UT, USA) with an internal diameter of 2.37 mm and a
height of 3 mm. The composite was inserted in two increments into the mold and light polymerized for 20
sec using LED curing light (Elipar S10 Curing Light; 3M ESPE, St. Paul, MN, USA). A radiometer
(Bluephase Meter II, Ivoclar Vivadent, Schaan, Liechtenstein) was used at constant intervals to ensure
sufficient light output (>1000 mW/cm
2
).
Bonding Procedure
Each hybrid CAD/CAM material was divided into seven groups (n=30 per group) based on the applied
surface treatments (NS: no surface treatment, SB: sandblasting only, SL: silane only, MP: Monobond Plus
only, SS: sandblasting and silane, SM: sandblasting and Monobond Plus, CS: CoJet and silane). Table 3
illustrates the protocols followed for applying each surface treatment. The composite cylinders were bonded
to the hybrid CAD/CAM slices using a universal bonding agent in combination with a universal resin
cement (Universalbond and Universalzement, DMG, Hamburg, Germany) according to manufacturer
instructions. Table 4 summarizes the characteristics and compositions of the materials used in the study.
The bonded specimens were seated in a custom-made alignment device and loaded with 1 kg. Excess
11
cement was removed, and each specimen was light cured for 20 sec on each side using a LED curing light
(Elipar S10 Curing Light; 3M ESPE, St. Paul, MN, USA).
Surface Treatment Applied Protocol
Sandblasting
(50 μm Al 2O 3)
The surface was treated with 50 μm aluminum oxide (Al 2O 3) particles
(Cobra 50 μm white; Renfert, Hilzingen, Germany) at an air pressure
of 2.8 bar using a fine blasting unit (Basic Quattro IS; Renfert,
Hilzingen, Germany) at a distance of 10 mm for 13 sec. Specimens
were cleaned ultrasonically in ethanol for 5 min, then rinsed with
distilled water for 30 sec and air-dried.
Silane Application
Silane (Vitique Silane, DMG, Hamurg, Germany) components were
mixed in 1:1 ratio for 15 sec and applied to the surface. After 10 sec,
the solvent was evaporated with a gentle stream of oil-free air.
Combination Coupling Agent
(contains MDP and silane)
The combination agent (Monobond Plus, Ivoclar Vivadent, Schaan
Liechtenstein) was applied to the surface and allowed to react for 60
sec. The excess material was dispersed, and the solvent was evaporated
with a stream of oil-free air.
Tribochemical Coating
(CoJet; 27 μm Al 2SiO 5)
The surface was treated using 27 μm silica coated aluminum oxide
(Al 2SiO 5) particles (CoJet, 3M ESPE, St. Paul, MN, USA) at an air
pressure of 2.8 bar using a fine blasting unit (Basic Quattro IS; Renfert,
Hilzingen, Germany) at a distance of 10 mm for 15 sec.
Table 3: Surface treatments protocols
Figure 1: Representation of the surface treatment assigned to each group
12
Material Manufacturer Composition (wt%)
Lava Ultimate
(Lot N895356)
3M ESPE, St. Paul, MN,
USA
Bis-GMA, UDMA, Bis-EMA, TEGDMA
with 80% fillers; silica (20 nm), zirconia (4-11
nm) & silica/zirconia clusters
LuxaCam Composite (Lot
776764)
DMG, Hamburg, Germany Polymer blend with 70% silicate glass fillers
Cerasmart
(Lot 1811291)
GC Dental Products,
Tokyo, Japan
Bis-MEPP, UDMA, DMA with 71% filler;
silica (20 nm), barium glass (300 nm) and
alumina nanoparticles
Filtek Z250 Composite
(Lot N889534)
3M ESPE, St. Paul, MN,
USA
TEGDMA, Bis-GMA, Bis-EMA, UDMA
with 84% silica & zirconia fillers (0.01−3.5
μm), photo-initiator
Vitique Silane
(Lot 774792)
DMG, Hamburg, Germany
Silane bottle: MPTMS
Activator bottle: water, ethanol, phosphoric
acid & catalyst
Monobond Plus
(Lot W90333)
Ivoclar Vivadent, Schaan,
Liechtenstein
Silane methacrylate, 10-MDP, ethanol,
disulphide methacrylate
Universalbond DMG, Hamburg, Germany
Bottle A: HEMA, Bis-GMA, acidic resin,
dibenzoyl peroxide
Bottle B: ethanol, water & activator
Universalzement DMG, Hamburg, Germany
UDMA, TEDMA, Bis-GMA, barium glass,
pigments, catalyst
Bis-MEPP: 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, TEGDMA: triethylene glycol
dimethacrylate, DMA: Dimethacrylate, UDMA: urethane dimethacrylate, Bis-GMA: Bisphenol A
glycidyl methacrylate, 10-MDP:10-methacryloyloxydecyl dihydrogenphosphate, HEMA: hydroxyethyl
methacrylate, Bis-EMA: Bisphenol A polyethethylene glycol diether dimethacrylate, MPTMS:
methacryloxypropyl trimethoxysilane
Table 4: Characteristic and composition of used materials
Artificial Aging
For each group, fifteen specimens were tested for early shear bond strength (SBS) after 24h storage in
distilled water at 37 °C. The other fifteen specimens per group were tested for late shear bond strength after
artificial aging by thermal cycling (THE-1100, SD Mechatronik, Feldkirchen-Westerham, Germany) for
20,000 cycles at 5°C - 55°C with 30 sec dwell time and 10 sec transfer time. Additionally, the specimens
were stored for 6 months in distilled water at 37°C.
13

Figure 2: Schematic representation of the study set
Shear Bond Strength Testing
The bond strength was measured with notched-edge shear bond strength test (ISO 29022/2013) using a
notched crosshead (Crosshead Assembly, Ultradent, South Jordan, UT, USA) mounted in a universal testing
machine (model 6596; Instron Corp, Norwood, Mass., USA) at a crosshead speed of 1 mm/min (22).
Cylinders were loaded in shear configuration until failure Figure 3. SBS values were recorded in N and
converted in MPa by dividing the failure load (N) by the bonding area (mm
2
). Specimens, which de-bonded
before testing, were recorded as pre-test failures (PTFs).
Figure 3: Notch-edge configuration for shear bond strength
14
Mode of Failure
Mode of failure (cohesive in CAD/CAM material, cohesive in composite, cohesive in cement, adhesive in
CAD/CAM material, adhesive in composite, mixed) were assessed with a stereo microscope (Wild M7;
Wild Heerbrugg AG, Heerbrugg, Switzerland) at x60 to x200 magnification and reported.

Microstructural Characterization
Scanning electron microscopy (SEM) was performed to evaluate the microstructure of the tested hybrid
CAD/CAM materials and the surface changes after applying each surface treatment. The specimens were
prepared following the same methodology above. The specimens were mounted on universal stubs with
double tape, sputter coated with gold-palladium (sputter coater 108, Cressington Scientific Instruments Ltd,
Watford, UK) and observed under a field emission scanning electron microscope (JEOL JSM-7001, JEOL
Inc., Peabody, MA, USA) at an accelerating voltage of 5.0 kV to 10.0 kV.

15
Early SBS Late SBS
LUNSE, Lava Ultimate-no surface treatment-early
LUSBE, Lava Ultimate- sandblasting-early
LUSLE, Lava Ultimate-silane-early
LUMPE, Lava Ultimate-Monobond Plus-early
LUSSE, Lava Ultimate- sandblasting + silane-early
LUSME, Lava Ultimate- sandblasting+ Monobond Plus-
early
LUCSE, Lava Ultimate-CoJet + silane-early
LUNSL, Lava Ultimate-no surface treatment-late
LUSBL, Lava Ultimate- sandblasting-late
LUSLL, Lava Ultimate-silane-late
LUMPL, Lava Ultimate- Monobond Plus -late
LUSSL, Lava Ultimate- sandblasting + silane-late
LUSML, Lava Ultimate- sandblasting+ Monobond Plus-
late
LUCSL, Lava Ultimate-CoJet + silane-late
LCNSE, LuxaCam-no surface treatment-early
LCSBE, LuxaCam-sandblasting-early
LCSLE, LuxaCam- silane-early
LCMPE, LuxaCam-Monobond Plus-early
LCSSE, LuxaCam- sandblasting + silane-early
LCSME, LuxaCam- sandblasting + Monobond Plus-early
LCCSE, LuxaCam-CoJet + silane-early
LCNSL, LuxaCam-no surface treatment-late
LCSBL, LuxaCam- sandblasting-late
LCSLL, LuxaCam-silane-late
LCMPL, LuxaCam- Monobond Plus-late
LCSSL, LuxaCam- sandblasting + silane-late
LCSML, LuxaCam- sandblasting + Monobond Plus-late
LCCSL, LuxaCam- CoJet + silane-late
CSNSE, Cerasmart-no surface treatment-early
CSSBE, Cerasmart- sandblasting-early
CSSLE, Cerasmart-silane-early
CSMPE, Cerasmart- Monobond Plus-early
CSSSE, Cerasmart- sandblasting + silane-early
CSSME, Cerasmart- sandblasting + Monobond Plus-early
CSCSE, Cerasmart-CoJet + silane-early
CSNSL, Cerasmart-no surface treatment-late
CSSBL, Cerasmart- sandblasting-late
CSSLL, Cerasmart-silane-late
CSMPL, Cerasmart- Monobond Plus-late
CSSSL, Cerasmart- sandblasting + silane-late
CSSML, Cerasmart- sandblasting + Monobond Plus-late
CSCSL, Cerasmart-CoJet + silane-late
Table 5: List of tested groups classified by aging

16
Statistical Analysis
Statistical analysis of the data was performed with a 3-way analysis of variance (ANOVA) model using
Bonferroni post-hoc multiple comparisons, with an overall significance level of α = 0.05. The dependent
variable was shear bond strength (in MPa), and the three factors used for analysis were: 1) aging, 2)
material, and 3) surface treatment. Furthermore, data was stratified by aging (early SBS and late SBS), and
2-way ANOVA models using Bonferroni post-hoc multiple comparisons were performed.

Pre-test failures (PTFs) were excluded from the analysis to allow the use of powerful parametric test. All
data were transformed using a square root transformation to meet the normality assumption. Although the
homogeneity of variance assumption was violated (Levene’s test, P= 0.0104), ANOVA is generally
considered robust to any homogeneity of variance issues in balanced datasets. Statistical software (STATA
15.1; College Station, TX: StataCorp LLC) was used for calculations.
17
Results
The mean values of shear bond strength (SBS) and standard deviation (SD) are listed in Table 6 and
illustrated in Figure 4. There were 8 out of 630 (1.27%) specimens recorded as pre-test failures (PTFs)
which were excluded from the analysis. Frequency of PTFs for groups were recorded as 12.5% LCNSL,
12.5% LCSML, 12.5% LUSLL, 12.5% LUSML, 12.5% CSNSE, 25% CSNSL and 12.5% CSCSL.
Mean shear bond strength was compared across the two levels of aging, three materials, and seven surface
treatments and the data were analyzed with a 3-way ANOVA model. All main factors of aging, material,
and surface treatment were statistically significant (P<0.001). Two-way interactions were significant
(P<0.001), aging x surface treatment (P<0.001) and material x surface treatment except aging x material
(P=0.2793). Three-way interaction aging x material x surface treatment was statistically significant
(P<0.001).
Due to the complexity of interpretation of the main effects and interactions, the data was stratified by aging,
and a 2-way ANOVA model was used to test materials and surface treatments differences of the early and
late SBS data separately. Table 7 summarizes the overall 3-way ANOVA and the 2-way ANOVA. The 2-
way ANOVA showed significant F-test values for the main effects of material and surface treatment
(P<0.001). Two-way interaction between material x surface treatment was also statistically significant
(P<0.001).

18

(Material: LuxaCam Composite – LC; Lava Ultimate – LU; CS – Cerasmart, Surface treatment: No surface
treatment – NS; Sandblasting – SB; Silane – SL; Monobond Plus – MP; Sandblasting and silane – SS;
Sandblasting and Monobond Plus – SM; CoJet and silane – CS, Aging: Early – E; Late – L)
Figure 4: Box plots of shear bond strength in MPa.

19
Group
LuxaCam (LC) Lava Ultimate (LU) Cerasmart (CS)
Mean ± SD Mean ± SD Mean ± SD
Early Shear Bond Strength (E)
No Surface Tx (NS) 16.35 ± 9.16
A
10.69 ± 3.86
A
4.31 ± 2.92
a
Sandblasting Only (SB) 37.05 ± 9.08

40.00 ± 12.31
B
24.44 ± 7.68
Aa

Silane Only (SL) 31.89 ± 7.20
a
22.28 ± 7.83
Cb
30.60 ± 10.71
ABab

Monobond Plus Only (MP) 22.02 ± 8.99
Aa
14.66 ± 5.82
ACab
12.28 ± 5.76
Cb

Sandblasting + Silane (SS) 38.74 ± 7.69
ab
33.57± 13.33
BCa
44.69 ± 9.50
Db

Sandblasting + Monobond Plus (SM) 37.97 ± 5.39 32.44 ± 9.57
BC
17.91± 3.23
ACa

CoJet + Silane (CS) 35.44 ± 9.96 37.93 ± 11.08
B
39.38 ± 11.96
BD

Late Shear Bond Strength (L)
No Surface Tx (NS) 2.93 ± 1.99

3.69 ± 2.06
A
2.81 ± 1.24
A
Sandblasting Only (SB) 29.41 ± 5.57
A
28.62 ± 7.50 20.07 ± 9.32
a

Silane Only (SL) 13.90 ± 3.39
Ba
5.96 ± 3.12
Ab
9.79 ± 4.41
ab

Monobond Plus Only (MP) 13.20 ± 5.07
Ba
4.41 ± 2.43
A
5.44 ± 2.00
A

Sandblasting + Silane (SS) 16.07 ± 2.45
Ba
24.53 ± 6.25 22.93 ± 7.04
Sandblasting + Monobond Plus (SM) 41.63 ± 6.12
Ca
24.40 ± 6.73 25.49 ± 7.58

CoJet + Silane (CS) 35.14 ± 11.99
ACa
25.85 ± 5.50 22.46 ± 8.14
Different lower-case letters in the same row indicate significant differences
Different UPPER-case letters in the same column indicate significant differences among same aging groups
Table 6: Mean Shear Bond Strength (MPa) and Standard Deviation (SD).

20
Source Sum of
Squares
df Mean Square F p-value
3-way
Aging 195.74 1 195.74 313.79 <0.001
Material 61.26 2 30.63 49.1 <0.001
Surface Treatment 850.43 6 141.74 227.22 <0.001
Aging x Material 1.59 2 0.80 1.28 0.2793
Aging x Surface Treatment 71.158 6 11.86 19.01 <0.001
Material x Surface Treatment 79.03 12 6.59 10.56 <0.001
Aging x Material x Surface Treatment 40.96 12 3.41 5.47 <0.001
Residual 361.17 579 0.62
Total 1649.34 620 2.66
2-way for early shear bond strength
Material 34.024 2 17.01 21.72 <0.001
Surface Treatment 363.88 6 60.65 77.43 <0.001
Material x Surface Treatment 66.60 12 5.55 7.09 <0.001
Residual 228.71 292 0.78
Total 688.04 312 2.21
2-way for late shear bond strength
Material 28.90 2 14.45 31.31 <0.001
Surface Treatment 554.61 6 92.43 200.27 <0.001
Material x Surface Treatment 53.58 12 4.47 9.67 <0.001
Residual 132.46 287 0.46
Total 768.09 307 2.50
Table 7: Summary of 3-way and 2-way ANOVA for SBS conducted at each level of interacting factor
21
Effect of Surface Treatments
I. Early Shear Bond Strength
Mean early SBS of LuxaCam Composite ranged from 16.35 to 38.74 MPa. Sandblasting and silane
application reported the highest SBS, but was not significantly different than SBS of LCSBE, LCSME,
LCCSE and LCSLE (P=1.00). All these groups were statistically higher than LCMPE (P<0.05) that
performed similarly to LCNSE (P>0.05).
Mean early SBS of Lava Ultimate groups ranged from 10.69 to 40.00 MPa. Sandblasting only had the
highest SBS which was not statistically different from LUSSE, LUSME, and LUCSE (P=1.00).
Sandblasting combined with silane or Monobond Plus reported no significant difference than groups treated
with silane or Monobond Plus only (P>0.05). LUMPE performed similar to LUNSE (P=1.00).
Mean early SBS of Cerasmart groups ranged from 4.31 to 44.69 MPa. Sandblasting and silane application
reported the highest SBS which was statistically similar to CSCSE (P>0.05). Both groups were significantly
different from all other groups (P<0.05) except when comparing CSCSE with CSSLE (P=1.00). Silane
application showed similar SBS to CSSBE and CSSME (P=1.00).
II. Late Shear Bond Strength
LuxaCam Composite had late SBS ranging from 2.93 to 41.63 MPa. LCSML group presented the highest
SBS which was significantly different from all groups (P<0.05) except LCCSL (P>0.05). Sandblasting only
produced statistically similar SBS to those of LCCSL (P=1.00). LCSSL presented no significant difference
in SBS compared to LCSLL and LCMPL (P>0.05).
Mean late SBS of Lava Ultimate ranged from 3.69 to 28.62 MPa. Sandblasting only had the highest SBS
which was not statistically different than LUSSL, LUSML, and LUCSL (P=1.00). The application of silane
or Monobond Plus only showed no significant difference than no surface treatment (P>0.05).
22
Mean late SBS of Cerasmart ranged from 2.81 to 25.49 MPa. The sandblasting and Monobond Plus group
reported the highest SBS which was not significantly different from those of CSSBL, CSSSL, CSCSL
(P=1.00). The group treated with silane only was statistically lower than these four groups (P<0.05).

(Material: LuxaCam Composite – LC; Lava Ultimate – LU; CS – Cerasmart)
Different lower-case letters indicate significant differences between groups
Figure 5: Mean (early & late) SBS (in MPa) presented by surface treatment
Late SBS Late SBS Late SBS
Late SBS Late SBS Late SBS
23
Effect of Restorative Material
I. Early Shear Bond Strength
Comparing the early SBS between the three CAD/CAM materials, Lava Ultimate and LuxaCam Composite
performed similarly for all surface treatments (P>0.05) except when treated with silane only as LCSLE was
significantly higher than LUSLE (P<0.05). Cerasmart reported significantly lower SBS than those of
LuxaCam Composite and Lava Ultimate in all surface treatments except groups that included silane
application; CSSLE and CSCSE were statistically similar to the corresponding group in other two materials
(P>0.05) and CSSSE group to LCSSE (P=1.00).
II. Late Shear Bond Strength
LuxaCam Composite presented significantly higher late SBS than Lava Ultimate with all surface treatments
(P<0.05) except LCNSL and LCSBL compared with LUNSL and LUSBL respectively (P=1.00). Also,
LuxaCam Composite reported statistically higher SBS than Cerasmart with all surface treatments (P<0.05)
except LCNSL and LCSLL (P>0.05). Sandblasting and silane application significantly lowered SBS of
LuxaCam Composite compared to the other two materials (P<0.05). Cerasmart performed similarly to Lava
Ultimate in all surface treatments (P>0.05) except sandblasting only group (P<0.05).

Effect of Aging
The effect of artificial aging on SBS was significant among all the groups (P<0.05) except LCSB, LCSM,
LCCS, LUSS, LUSM, CSNS, CSSB and CSSM groups which presented no significant difference between
early and late SBS (P>0.05). Generally, the early SBS was higher than the late SBS except when
sandblasting and Monobond Plus surface treatment was applied to LuxaCam Composite and Cerasmart.
These two groups reported higher late SBS than early SBS, but it was not significantly different (P>0.05).
24

(Surface treatment: No surface treatment – NS; Sandblasting – SB; Silane – SL; Monobond Plus – MP; Sandblasting and
silane – SS; Sandblasting and Monobond Plus – SM; CoJet and silane – CS)
Different UPPER-case letters indicate significant differences between groups
Figure 6: Mean (early & late) SBS (in MPa) presented by restorative material.
Mode of Failure
Analysis of the total sample showed mainly adhesive failures at the CAD/CAM interface (55%), followed
by cohesive failures within the CAD/CAM material (33%), and mixed failures (8%). The detailed mode of
failure for each group is presented in Figure 7 and Table 8.

Figure 7: Mode of failure.

25
Failure Mode, N (row %)
Group
Cohesive
in
CAD/CAM
Cohesive
in
composite
Cohesive
in
cement
Adhesive
at
CAD/CAM
Adhesive
at
Composite
Mixed Total
LUNSE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUSBE 11 (78.57) 0 (0.00) 1 (7.14) 2 (14.29) 0 (0.00) 0 (0.00) 14 (100.00)
LUSLE 0 (0.00) 0 (0.00) 0 (0.00) 13 (86.67) 0 (0.00) 2 (13.33) 15 (100.00)
LUMPE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUSSE 9 (60.00) 0 (0.00) 0 (0.00) 4 (26.67) 0 (0.00) 2 (13.33) 15 (100.00)
LUSME 12 (80.00) 0 (0.00) 0 (0.00) 1 (6.67) 0 (0.00) 2 (13.33) 15 (100.00)
LUCSE 7 (46.67) 0 (0.00) 0 (0.00) 5 (33.33) 1 (6.67) 2 (13.33) 15 (100.00)
LCNSE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCSBE 13 (86.67) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 2 (13.33) 15 (100.00)
LCSLE 5 (33.33) 0 (0.00) 0 (0.00) 8 (53.33) 0 (0.00) 2 (13.33) 15 (100.00)
LCMPE 0 (0.00) 0 (0.00) 0 (0.00) 14 (93.33) 0 (0.00) 1 (6.67) 15 (100.00)
LCSSE 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCSME 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCCSE 14 (93.33) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 1 (6.67) 15 (100.00)
CSNSE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSSBE 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSSLE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSMPE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSSSE 6 (40.00) 0 (0.00) 0 (0.00) 5 (33.33) 0 (0.00) 4 (26.67) 15 (100.00)
CSSME 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSCSE 4 (26.67) 1 (6.67) 0 (0.00) 8 (53.33) 0 (0.00) 2 (13.33) 15 (100.00)
LUNSL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUSBL 9 (60.00) 0 (0.00) 0 (0.00) 4 (26.67) 0 (0.00) 2 (13.33) 15 (100.00)
LUSLL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUMPL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUSSL 5 (33.33) 1 (6.67) 0 (0.00) 8 (53.33) 0 (0.00) 1 (6.67) 15 (100.00)
LUSML 8 (53.33) 0 (0.00) 0 (0.00) 6 (40.00) 0 (0.00) 1 (6.67) 15 (100.00)
LUCSL 7 (46.67) 0 (0.00) 0 (0.00) 5 (33.33) 0 (0.00) 3 (20.00) 15 (100.00)
LCNSL 0 (0.00) 0 (0.00) 1 (6.67) 14 (93.33) 0 (0.00) 0 (0.00) 15 (100.00)
LCSBL 0 (0.00) 0 (0.00) 2 (13.33) 7 (46.67) 0 (0.00) 6 (40.00) 15 (100.00)
LCSLL 1 (6.67) 0 (0.00) 0 (0.00) 14 (93.33) 0 (0.00) 0 (0.00) 15 (100.00)
LCMPL 0 (0.00) 0 (0.00) 1 (6.67) 13 (86.67) 0 (0.00) 1 (6.67) 15 (100.00)
LCSSL 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCSML 1 (6.67) 1 (6.67) 0 (0.00) 5 (33.33) 0 (0.00) 8 (53.33) 15 (100.00)
LCCSL 1 (6.67) 4 (26.67) 0 (0.00) 5 (33.33) 2 (13.33) 3 (20.00) 15 (100.00)
CSNSL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSSBL 6 (40.00) 0 (0.00) 1 (6.67) 7 (46.67) 0 (0.00) 1 (6.67) 15 (100.00)
CSSLL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSMPL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSSSL 4 (26.67) 3 (20.00) 0 (0.00) 6 (40.00) 0 (0.00) 2 (13.33) 15 (100.00)
CSSML 10 (66.66) 1 (6.67) 0 (0.00) 2 (13.33) 0 (0.00) 2 (13.33) 15 (100.00)
CSCSL 2 (13.33) 1 (6.67) 0 (0.00) 11 (73.33) 0 (0.00) 1 (6.67) 15 (100.00)
Total 210 (33.39) 12 (1.91) 6 (0.95) 347 (55.17) 3 (0.48) 51 (8.11) 629 (100.00)
Table 8: Frequency and percentage of failure mode by group
26
Microstructural Characterization
Scanning electron microscopy (SEM) was used to examine the surface topography of each hybrid
CAD/CAM material after applying different surface treatments. Representative SEM images are illustrated
in Figure 8. According to SEM examination, polished surfaces presented a smooth topography for all tested
hybrid CAD/CAM materials. LC and CS were relatively similar exhibiting uniformly distributed particles
embedded in the resin matrix, LU showed a characteristic microstructure in the form of agglomerated and
non-agglomerated filler particles embedded in the resin matrix.
The surface topography of all tested materials was significantly altered after applying micromechanical
surface treatments (SB and CJ). SEM images of treated surfaces presented increased surface micro-
irregularities and randomly distributed micropores in all hybrid CAD/CAM materials investigated in this
study. More specifically, surface roughness was more prominent after SB compared to CJ surface treatment.
Evident undercuts, ridges and grooves on the surface of each material could be easily identified after
sandblasting. SEM images of surfaces treated with CJ showed less surface irregularity and visible silica
particles randomly embedded into the hybrid CAD/CAM materials.

27

Figure 8: Scanning electron microscopy of hybrid CAD/CAM materials (magnification x10,000)

(1a) Microstructure of Lava Ultimate polished surface
(2a) Microstructure of LuxaCam Composite polished surface
(3a) Microstructure of Cerasmart polished surface
(1b) Microstructure of Lava Ultimate after application of 50 μm Al2O3 at pressure of 2.8 bar for 13 sec.
(2b) Microstructure of LuxaCam Composite after application of 50 μm Al2O3 at pressure of 2.8 bar for 13 sec.
(3b) Microstructure of Cerasmart after application of 50 μm Al2O3 at pressure of 2.8 bar for 13 sec.
(1c) Microstructure of Lava Ultimate after application of with 27 μm Al2SiO5 at pressure of 2.8 bar for 13 sec.
(2c) Microstructure of LuxaCam Composite after application of 27 μm Al2SiO5 at pressure of 2.8 bar for 13 sec.
(3c) Microstructure of Cerasmart after application of 27 μm Al2SiO5 at pressure of 2.8 bar for 13 sec.
1a 1b 1c
2a 2b 2c
3a 3b 3c
28
Discussion
The present results showed that the tested surface treatments had a positive effect on the shear bond strength
(SBS) of the tested hybrid materials. Therefore, the first null hypothesis that, surface treatment has no
significant effect on SBS of hybrid CAD/CAM materials, was rejected. These results are in agreement with
the findings of previous studies (16, 26), and suggest that the effectiveness of bonding relies more on
micromechanical retention, rather than on the assumed chemical bond by silane and/or MDP containing
agents. Several studies (29, 30) related the improved bonding properties of the abraded specimens to the
increased surface roughness reporting that surfaces with more roughness achieved higher SBS values than
surfaces with less roughness. As seen in Figure 8, the SEM images clearly revealed alteration in the surface
topography of the micromechanically treated specimens compared to the untreated specimens in all the
tested materials. Whereas untreated surfaces presented smooth appearance, sandblasting and tribochemical
coating roughened the surface in all tested materials.
In the present study, micromechanical retention has been applied using two airborne particle abrasion
methods: first, sandblasting (SB) the restoration with alumina oxide (Al 2O 3) particles which has been
suggested by previous studies (31-33) to increase the surface area and improve the mechanical interlocking
between luting cement and many restorative materials. Second, tribochemical coating (CoJet- CJ) that has
been recommended for metals and polycrystalline materials as silica coated aluminum (Al 2SiO 5) particles
abrade the receptive surface and embed silica particles to be used for the silanization thereby improve
bonding (21). Studies (19, 20, 26) have shown that particles size, applied air pressure, duration and distance
affected the roughness of the receptive surface. A previous study (19) supported this claim reporting that
bond strength of hybrid materials improved when using 50 μm Al 2O 3 particles compared to 27 μm Al 2O 3
and 30 μm Al 2SiO 5 particles. Although our study implemented different airborne particle abrasion
parameters (SB; 50 μm Al 2O 3 at 12.8 pressure, 10 mm distance for 13 sec vs CJ; 27 μm Al 2SiO 5 at 12.8
pressure, 10 mm distance for 15 sec), there was no significant different at SBS of tested materials between
two treatments (comparing SS and CS groups for less variable comparison). This could be explained by the
29
fact that the tested hybrid materials already have silica fillers in their composition; thus, there is no
additional benefits for the silica coating when silane application is intended (33).
The application of silane coupling agents was suggested by several studies (1, 31) to improve the bond
strength of resin cement to CAD/CAM restorative materials. Higashi et al. (31) suggested that the
improvement of bond strength after silanization may be due to the chemical bond between resin cement
and the restorative material created by covalently coating the silica-containing surface with methacrylate
double- carbon bonds that can co-polymerize with the resin matrix. Another theory (22) suggested that the
bond enhancement is due to improving the wettability of the bonding surface and reducing the contact angle
of resin cements with restorative material. This could allow the resin cement to penetrate into the micro-
roughness created on the surface, resulting in increased micromechanical retention. Our results showed that
chemical treatment by silane alone improved the early SBS of all tested materials compared to untreated
specimens (NS). However, there was significant reduction in SBS after aging. Additionally, despite the
statistical significance comparing SL and NS groups of LuxaCam Composite (LC) and Cerasmart (CS), the
SBS values were below the acceptable bond strength range suggested by literature (15 - 25 MPa) making
it clinically irrelevant (34).
Moreover, the application of silane to roughened specimens by SB or CJ did not significantly influence the
SBS of all tested materials compared to SB alone. Except the increase in the early SBS of CSSSE and
CSCSE groups which significantly decreased after aging questioning its durability. While some studies (26,
29, 30) reported an improvement in the bond strength of Cerasmart (CS) and Lava Ultimate (LU) after
silane application, other studies (16, 34) supported our finding by recommending sandblasting only The
discrepancy between the results may be explained by different methodology like the form of silane agents
(two-bottles vs single bottle), artificial aging protocol and the bond testing method (35). Additionally,
different rate of silane hydrolysis which depends among others on the silane molecular structure, its
concentration, pH, temperature, humidity, and solvent system (17).
30
The combination coupling agent used in this study (Monobond Plus-MP) is designed to bond to silica, oxide
ceramics, base metals and precious metals as it contains three active agents (silane, MDP and disulfide
methacrylate) in one bottle. Several studies (13, 36, 37) reported that combination coupling agent is
effective in improving the bond strength of glass-ceramic and zirconium oxide restorations. Although the
manufacturer claims it is a universal primer for all types of restorative materials, our findings suggested
that the influence of MP application on the bond strength is material dependent. There was an improvement
in the early SBS to all tested materials, but this effect did not provide stable long-term bonding performance
for LU and CS. The late SBS of LCMPL was significantly higher compared to LCNSL, but this increase is
not clinically relevant as the bond strength value is still below the acceptable range (34).
According to the present study, the addition of combination coupling agent to sandblasted specimens (SM)
did not have a significant effect on early SBS of all tested materials compared to micromechanical retention
alone (SB). After artificial aging, only LC presented statistically higher SBS in LCSML group compared
to LCSBL group. A possible explanation to these finding is that the use of MDP containing universal
adhesive could have obscured the effectiveness of the MDP content in the coupling agent which is expected
to bond to zirconia fillers in Lava Ultimate adding to its bond strength (30). Additionally, researchers have
argued the stability of silane in acidic mixtures were prone to hydrolysis (17, 38). However, the
manufacturer reported that Monobond Plus is not an aqueous solution with a low pH and both the silane
and the phosphoric acid derivative will not change noticeably at room temperature. However, additional
studies may be required to confirm this explanation.
LC presented different bonding behavior with the addition of chemical treatment (SL or MP) to sandblasted
specimen which was not the case with other two hybrid materials. Whereas the addition of silane (LCSSL)
significantly dropped the SBS, the addition of combination coupling agent (LCSML) significantly
increased the SBS in comparison with LCSBL group. This phenomenon could be explained by two related
aspects. First, sandblasting the surface with alumina powder may leave a thin layer of alumina coating onto
the substrate surfaces (38, 39). After silanization, Al–O–Si bonds are formed which are somewhat weaker
31
than Si–O–Si and more susceptible to hydrolysis (38). Second, the magnitude of effect is determined to the
amount of alumina deposited which is directly related to the sandblasting pressure and surface hardness
(39). The same mechanism applies for bonding 10-MDP to the deposited alumina which is on the other
hand more resistance to degradation explaining the contradicting bonding behavior (13).
The surface hardness of LC hybrid materials is another aspect as low hardness allows more alumina
deposition magnifying the effect of the chemical bond (38). Hardness is a material property defined as the
resistance of a material to plastic deformation produced by an indentation force (40) There are several types
of surface hardness tests which are based on the ability of the surface of a material to resist penetration by
a diamond point or steel ball under a specified load (41). Examples of these tests are Brinell, Rockwell,
Shore, Vickers, and Knoop hardness tests (41). Supporting our finding in regard to LC, a previous study
(42) presented differences in Vickers hardness (HV) between LU compared with LC reporting that hardness
parameters increase progressively with increasing the amount of inorganic fillers. LU with 80 wt% fillers
had significantly higher HV than LC with 70 wt% fillers (42).
The bond strength of hybrid CAD/CAM material was affected by the restorative material selection.
Therefore, the second null hypothesis that restorative material has no significant effect on SBS was rejected.
In the long-term, LC generally presented higher bonding performance than LU and CS regardless surface
treatments. On the other hand, CS performed similarly to LU in all surface treatments except SB group.
These findings can be explained by the differences in microstructure and chemical composition of the tested
materials (42, 43). In agreement with this result previous studies reported that the efficiency of surface
treatment is highly dependent on the chemical composition of the restorative material rather than the surface
treatment itself as different organic matrices and filler compositions may react differently during surface
treatments (23, 30). More details about the effect of chemical composition and microstructure will be
discussed in Chapter II.
32
In order to induce clinically relevant parameters to identify superior surface treatment and restorative
materials, artificial aging of the bonded specimens has been used. Several in-vitro studies (26, 43, 44) used
artificial aging to simulate changes in the oral environment and create clinically relevant testing parameters.
Although there is no gold standard for aging CAD/CAM materials, there are many acceptable methods
applied in most of the studies which are based on chemical, thermal or mechanical aging (44, 45). The
current study used long-term water storage (6 months of storage in distilled water at 37°C) and thermal
cycling (20K cycles at 5°C - 55°C) where all assigned specimens were treated equally regarding the aging
protocol to provide comparability. The results presented significant effect of aging on lowering SBS among
most of the groups. Therefore, the second null hypothesis was rejected. Each of these aging methods has a
different mechanism; storage in a media solution is based on the concept of chemical degradation of the
compound by a solvent (44, 46). In our case, the presence of water caused degradation of the unprotected
ester linkages in methacrylate-based resin monomers, polymers and coupling agents in a process called
hydrolysis (46, 47). Different storage media have different impact on the bond strength; however, using
distilled water reported to have similar effect compared to using artificial saliva (47). Literature presented
variable storage duration which also affect the outcome of the in-vitro study (44, 46). It was reported that
24 h is the minimum requirement to allow complete polymerization of the tested materials, and at least a
duration of 6 months to reflect the durability of bond strength (44, 46).
The second method used in our study was thermocycling which combines accelerated hydrolysis and
repeated volumetric changes (expansion/contraction) causing mechanical stress and form microcracks in
the bonding interface lowering the bond strength (44). ISO 11405 recommendation for thermal cycling is
500 cycles in water bath at temperature of 5–55 °C with dwell time of 20 sec (48). However, many studies
reported these number of cycles to be insufficient for in-vivo simulation (49, 50). Gale and Darvell (50)
suggested the use of 10K cycles reporting it is equivalent to one year in the oral cavity, others reported 50K
would be the equivalent of a year (49). The lack of standardized aging protocols caused the outcomes of
laboratory testing to be variable and incomparable (44). A previous study (51) compared the effect of
33
different aging methods on the bond strength and reported that 6 months of water storage equal the effect
of 10K (5- 55°C) thermocycles as both decreased the bonding strength to nearly 50% of initial values at 24
h.
Based on our findings, micromechanical retention produced more durable bond compared to chemical
treatment which is sensitive to hydrolysis. For example, silane is reported to be instable in the presence of
−OH containing compounds, polar groups and water (38). Moreover, the siloxane ionic bonds (Si–O–Si)
between the silane molecule and the inorganic surface are hydrolyzed to silanol (–Si–OH) which condensate
and deactivate the silane (38). While the addition of chemical treatment to micromechanically treated
surfaces did not present an influence on the durability of the bond in most of tested groups, it had a
deteriorating effect on others such as LCSS implying that bonding protocols should be material specific
rather than generalized.
Diverse methodologies have been suggested to evaluate the bonding performance of adhesive agents and
cements to restorative materials such as macro- or micro-shear bond strength, macro- or micro-tensile bond
strength, pull-off, push-out, fatigue and fracture toughness (35). These testing methods differ in the
specimens’ geometries, the loading configuration, the direction of applied force and the stress distribution
thus comparison results of different tests should be carefully made. In the present study, shear bond strength
(SBS) test, where a compressive force is applied parallel to the bonding interface, was selected as it is a
commonly used, and reliable method (25, 30, 35, 52). Compared to other testing methods, SBS test has the
advantages of simple specimen preparation and elimination of pre-stressing factors such as sectioning
specimens (35). However, the validity of SBS test has been questioned in terms of non-uniform interfacial
stresses which might cause cohesive failures in the bonded substrate leading to misinterpretation of the
results (28, 35, 53, 54). Additionally, stress concentrations near the loading site reduces the calculated SBS
below the true failure stress levels (28, 35, 53, 54). In the present study, SBS of hybrid CAD/CAM materials
was measured using notched-edge configuration which is designed to provide better stress distribution
across the bonding interface allowing a more standardized testing method (22).
34
The tested specimens presented mainly adhesive failures in all groups which indicate the validity of the
applied testing method (35). Cohesive failures were also observed in the CAD/CAM material which may
indicate that the bond between the restorative materials and cement seemed to exceed the strength of the
CAD/CAM material (35). Therefore, cohesive failure refers to mean strength of the tested material rather
than the true bond strength value of the bonding interface. In the present study, the number of pre-test
failures (PTFs) was not high enough (1.27% of total sample) to misrepresent the performance of the tested
materials; therefore, all PTFs were excluded from the analysis to preserve the normal distribution of the
data allowing the use of powerful parametric test (55).

35
Conclusion
Within the limitations of the present study, all the tested factors (surface treatment, restorative material, and
aging) influenced the shear bond strength (SBS) of hybrid CAD/CAM materials. It could be concluded that
surface treatments resulted in higher SBS values compared to untreated surface in all tested materials. The
effectiveness of bonding relied more on micromechanical retention, rather than on the chemical retention.
Depending on the restorative material, silane and/or MDP containing agents had little to no effect on the
SBS of tested materials. Mostly, there were negligible differences, that may not have clinical significance.
Further research is needed to provide insights into the chemical and microstructural characterizations of
hybrid CAD/CAM materials that may cause differences in their bonding performance.

36
Chapter II: Luting Protocol for Novel Hybrid CAD/CAM Materials
Introduction
Adhesion mechanisms to dental substrates are based primarily on the demineralization of the enamel and/or
dentin by acid etching followed by the infiltration of resin monomers into the created microporosities to
become micromechanically interlocked (9, 10). Bonding to the dental substrate follows one of the following
approaches: 1) etch and rinse approach which removes the smear layer, 2) self-etch approach which
modifies the smear layer, and 3) selective etching approach which includes applying phosphoric acid on
the enamel margins prior to the application of self-etch adhesives (11, 12). Based on these concepts, dental
adhesive systems can be classified into etch and rinse system, self-etch system and recently developed
multi-mode universal adhesive system. The clinical application of these adhesive systems may involve
three, two, or a single step based on the number of the components in that system (Figure 9).

Figure 9: Schematic illustration for dental adhesive systems

bonding agent
Three-steps Two-steps
Dental Adhesive Systems
Multi-mode Universal
Adhesive
Etch & rinse Adhesive
Etch & rinse
mode
Self-etch
mode
Acid
Primer
Adhesive
Acid
Primer
+
Adhesive
Two-steps
Self-etch Adhesive
Adhesive
Acid
+
Primer
One-step
Two-bottles One-bottle
+
Acid
+
Primer
+
Adhesive
Acid
+
Primer
+
Adhesive
37
Luting cements can be classified based on their interaction with the tooth substrate into non-adhesive
cements (e.g zinc phosphate cement), chemically bonded cements (e.g glass ionomer-based, and phosphate-
modified resin cements), and micromechanically bonded cements (e.g resin-based cements) (8).
Manufacturers constantly working on improving the material’s properties which dictate the clinical
indication and performance of luting cements. For example, luting cement should have high compressive
and tensile strength to waistband different stresses, elastic modulus close to dentin (13.7 GPa), low film
thickness (≤ 25 μm), dimensional stability and low solubility in oral environment to provide favorable
outcome (40). Luting cements vary in their mechanical and physical properties which are determined by
their chemical composition (Table 9) (6).

38
Type of Cement
Type of
Reaction
Strength (MPa)
Modulus
of
Elasticity
(GPa)
Flexural
Strength
(MPa)
Solubility in
Water
(wt% or
μg/mm
3
)
Tensile Compressive
ISO 9917 N/A N/A 50 N/A N/A
0.2% or
40 μg/mm
3

(max)
Non-adhesive
Zinc phosphate Acid-base 3.1-4.5 96-133 13 15-98 0.2%
Chemical Bonding
Polycarboxylate Acid-base 3.6-12 57-99 5-6 14.7-16.5 0.06%
Glass-ionomer Acid-base 42.53 93-226 7-8 7.8-24.8 1.25%
Resin-modified
glass- ionomer
Acid-base +
polymerization
13-25 85-160 2.5-7.8 27-100 1%
Phosphate-
modified resin
(self-adhesive)
Polymerization 34 212-291 4.5-6.6 42-99
3-33 μg/mm
3

Micromechanical Bonding
Self-cured
composite resin
Polymerization
(chemical
activation)
62 292 6.5 100 0.89%
Light-cured
composite resin
Polymerization
(light
activation)
77.4 345-400 4.5 107-123
0-12 μg/mm
3

Dual-cured
resin cements
Polymerization
(light and
chemical
activation)
40-56 279-352 6-9.6 110-131
0-128 μg/mm
3

Table 9: Material properties of various cements (6, 40).
39
Focusing on resin cements, many factors influence these properties such as the filler type, size, and load,
the nature of the resin matrix, and its proportions, initiators/stabilizers and degree of conversion (56). Resin
cements can be sub-classified according to the adhesive system used in combination with the cement into
etch and rinse, self-etch and self-adhesive resin cements (Figure 10) (8). The recently introduced self-
adhesive resin cements bond to the receptive substrate without the application of acid or adhesive system
as functional monomers are incorporated into the cement with potential for chemical interaction with the
bonding substrates (tooth, ceramics, and alloys) (13, 18, 37).

Figure 10: Classification of resin cement
The bonding mechanism of self-adhesive cements to tooth structure rely more on chemical interaction
rather than the micromechanical retention as the incorporated functional acidic monomers react with the
calcium ions of the hydroxyapatite partially dissolving the smear layer without removing the smear plug
within the dentinal tubules (18, 31). A thick smear layer may negatively influence the bond strength,
however, acid etching the dentin with phosphoric acid is detrimental and must be avoided since the
hydroxyapatite is needed for the chemical bond (18, 31). Studies reported (6, 57) that surface conditioning
bonding agent
Resin Cement
Self-adhesive Resin Cement Conventional Resin Cement
Etch & rinse
resin cement
Self-etch
resin cement
Self-etch
adhesive
Etch & rinse
adhesive
No adhesive needed as
functional monomers
incorporated into the
cement
Based on polymerization:
Self-cure
Light-cure
Dual-cure
40
the dentin using mild acidic agents, such as 25% polyacrylic acid might remove the superficial loosely
bound fraction of the smear layer, thus improving adhesion. On the other hand, pretreatment of enamel with
strong acid, such as 35% phosphoric acids is recommended to yield a higher bond strength (58).
In the past two decades, dental adhesives and cements have been revolutionized moving towards simplicity
and efficiency. Many chemical components such as acidic functional monomers (e.g 4-META, phenyl-P,
and 10-MDP) and/or silane coupling agents have been incorporated into the adhesive systems and resin
cements in attempt to eliminate additional bonding steps (14, 37). Such chemical molecules are known for
promoting adhesion of resins to hydroxyapatite, oxide ceramics, and base metals in case of 10-MDP, or
silica glass in case of silane (14, 31, 37). The mechanism of action of these molecules (silane and 10-MDP)
are mentioned in Chapter I above.
Materials with such chemical composition have been advertised by the manufacturers as “universal
adhesive agents” and “universal resin cements”. This terminology refers to the ability of the product to
promote adhesion to dental substrate as well as various restorative substrates including ceramics,
polycrystalline and resin-based composite without the use of accessory priming agents (15, 27, 30). The
use of the term “universal” is unfortunately misleading to many clinicians and does not reflect the clinical
reality. Yet, there is no true “universal cement” as the bonding property of the resin cement is dictated by
the adhesive system used rather than the cement itself. For example, the manufacturer of commercially
available universal resin cement (Universalzement, DMG, Hamburg, Germany) recommends combining it
with universal bonding agent (Universalbond, DMG, Hamburg, Germany) although it is advertised as
“universal”.
Regarding universal adhesives, heterogenous bonding behavior towards the bonding substrates was
observed due to differences in their functional components (13, 14, 37). For example, universal adhesives
vary in their bonding potential to dental substrate due to differences in the concentration and purity of 10-
MDP which affects their etching capacities of enamel and dentin (13). Moreover, some universal adhesives
41
will not bond to silica due to the absence of a silane component in the adhesive. As the term “universal”
does not necessarily mean the presence of both silane and 10-MDP molecules, the selection of adhesives
should be material-specific.
Over the years, manufacturers have been working on improving the indirect restorations in relation to their
mechanical, optical and bonding properties by altering their composition. With the advances in computer-
aided design (CAD)/ computer-aided manufacturing technology, indirect restorations have become a
popular option. Different formulations have been introduced recently with different CAD/CAM material
classifications (Table 1) which exhibit different composition, material properties, processing methods and
clinical indications (5). Additionally, materials within the same classification exhibit various mechanical
and bonding properties due to different composition in terms of type of resin monomer, type of fillers, load
of fillers, size and shape (5, 42, 43, 59, 60). However, manufacturers are recommending the same bonding
protocols based on the overall class of material rather than being material specific.
Focusing on hybrid CAD/CAM materials, e.g., Lava Ultimate (LU; 3M ESPE, St. Paul, MN, USA) is
classified as a resin nano- ceramic which has approximately 80 wt% of zirconia-silica nanofillers in the
form of agglomerated and non-agglomerated particles bound in a 20 wt% of UDMA-based resin matrix.
Th material is totally heated rather than photopolymerized and has a flexural strength of 170-180 MPa (16).
Cerasmart (CS; GC Dental Products, Tokyo, Japan) is also a resin nano-ceramic with 71wt% of alumina-
barium-silicate fillers homogeneously and evenly distributed in a UDMA-based matrix. The block is heated
and polymerized upon manufacturing, resulting in a flexural strength of 220-240 MPa (16). A new material
of the same category (LuxaCam Composite, LC; DMG, Hamburg, Germany) was recently introduced with
flexural strength of 130 MPa (43). The composition of the material given by the manufacturer are not exact;
the organic matrix is generically specified as methacrylate based filled with 70% silicate-glass particles.
Despite the previously discussed differences between these hybrid materials which influence their bonding
behavior, manufacturers still suggest similar bonding protocols in term of surface treatment and the
42
application of an additional layer of universal adhesive or a primer to the restorative substrate. Table 10 list
the bonding protocol suggested for different hybrid CAD/CAM materials according to the manufacturers.
The present study aims to offer guidance towards developing material specific bonding protocol. After
testing different surface treatments in relation to the bond strength of hybrid CAD/CAM materials in
Chapter I, the current part will test the bonding performance of hybrid CAD/CAM materials cemented with
different luting cements (conventional resin cement, self-adhesive resin cement and resin-modified glass-
ionomer cement) using different bonding protocols (applying universal adhesive, applying combination
coupling agent or using the cement alone).
CAD/CAM Material Bonding Protocol (according to manufacturer)
Lava Ultimate
(3M ESPE, St. Paul, MN,
USA)
1) Sandblast the surface with 50 μm aluminum oxide particles
at an air pressure of 2 bar
2) Clean the surface with alcohol and air-dry
3) Apply a universal adhesive agent according to its instructions
of use
Cerasmart
(GC Dental Products, Tokyo,
Japan)
1) Sandblast the surface with 25-50 μm aluminum oxide particles
at an air pressure of 1.5 bar or treat with 5% hydrofluoric acid
for 60 sec.
2) Clean the surface with water or alcohol and air-dry
3) Apply a silane coupling agent or a primer according to
instructions of use
LuxaCam Composite
(DMG, Hamburg, Germany)
1) Sandblast the surface with 50 μm aluminum oxide particles
at an air pressure of 2 bar
2) Clean the surface with water or alcohol, and air-dry
3) Apply a suitable primer or universal adhesive according to
its instructions of use
Table 10: Bonding protocols for hybrid CAD/CAM materials according to the manufacturer.
The chemical compositions of the restorative materials, adhesive systems, and luting cements play an
important role in the bonding properties of the restoration-cement interface (13, 61, 62). Unfortunately, this
information when provided by the manufacturers is often incomplete or labeled with misleading
terminologies. To our knowledge the majority of in-vitro bond strength studies have relied on bond strength
tests in combination with electron microscopy examination such as scanning electron microscopy (SEM)
which uses very narrow electron beam which presents a large depth of field yielding a characteristic 3D
appearance with a wide range of magnifications (58, 63). A limitation of these studies is that they provided
43
only indirect evidence of the dynamic reactions occurring at the bonding interface. Moreover, the
microstructural analysis provides only very limited information on the chemistry of used material and the
bonding interfaces (58, 63).
Chemical analysis can be performed via spectroscopy which is defined as the study of the interaction
between matter and electromagnetic radiation (64). It uses the principle of light scattering or absorbance of
different wavelengths, such as X-rays, laser light, UV light and visible light to determine the particles’ size,
shape, material compositions and concentration (64). Different types of spectroscopy are distinguished by
the type of radiative energy involved in the interaction. These types include Fourier-transform infrared
spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Energy-
dispersive X-ray spectroscopy (EDS or EDX) (64, 65).
FTIR and Raman spectroscopy have been applied in dental research to evaluate the degree of conversion
of polymers, study the setting reaction of dental material such as glass ionomer or study dental tissue
demineralization/remineralization (36, 64, 65). While FTIR require extensive sample preparation, Raman
spectroscopy requires little to none and provides data in matter of seconds (66). Raman spectroscopy also
has the advantage of allowing observation through glass, observation in aqueous solutions, and analysis of
minute regions of less than 1 μm in high resolution (36, 65, 67). This in-vitro study will combine
microstructural and chemical characterization techniques with the bonding strength test to provide an
insight on the adhesion of hybrid CAD/CAM restorative materials to resin cements emphasizing on the
effect of the materials’ composition and microstructure.
The continuous development of new CAD/CAM materials has led to a need to study their bonding behavior
in attempt to predict their clinical performance. Modern restorative treatments have been shifting towards
minimally invasive preparations where the clinical success heavily relies on the bonding of the restorations
rather than the preparation’s retentive features (68). The final bond strength is defined by the weakest link
in the chain. Therefore, the adhesive bond between the different material interfaces has to be constantly
44
improved

and adapted to the requirements of newly developed materials (16). Many factors affect the
bonding performance of the restoration which include bonding substrate, restorative material, adhesive
system, luting cement, bonding protocol, and the clinician’s knowledge and skills (5, 16, 29, 56). The
ultimate goal is to optimize all these factors to ensure long-term success of the restoration.
45
Objective of the Study
Choosing a proper luting cement which is chemically compatible with the restorative material is a critical
step for efficient bonding procedure. Therefore, the aims of this study were:
1) To assess the bonding performance of different cement systems with hybrid CAD/CAM materials
using a notched-edge shear bond strength test.
2) To examine the different microstructures of hybrid CAD/CAM materials and the different chemical
components that contribute to their bonding performance using scanning electron microscopy (SEM)
and micro-Raman spectroscopy.
The null hypotheses of this investigation were:
1) Restorative material has no significant effect on SBS.
2) Luting cement has no significant effect on SBS.
3) Artificial aging has no significant effect on SBS.

46
Material and Methods
Sample Preparation
Five hundred and forty square specimens were fabricated using three hybrid CAD/CAM materials (Lava
Ultimate; LU, LuxaCam Composite; LC and Cerasmart; CS). The specimens were sectioned, polished and
cleaned following the same protocol in Chapter I above. Furthermore, composite cylinders (Filtek Z250
composite, 3M ESPE, St. Paul, MN, USA) were fabricated using bonding molds inserts (Ultradent Products
Inc., South Jordan, UT, USA) with an internal diameter of 2.37 mm and a height of 3 mm. Table 11 listed
these materials characteristic and chemical composition.

Material Manufacturer Composition
Universalbond
DMG, Hamburg,
Germany
Bottle A: HEMA, Bis-GMA, acidic resin,
dibenzoyl peroxide.
Bottle B: ethanol, water & activator.
Universalzement
DMG, Hamburg,
Germany
UDMA, TEGDMA, Bis-GMA, barium glass,
pigments, catalyst.
RelyX Ultimate
(Lot 3410062)
3M ESPE, St. Paul,
MN, USA
Base: methacrylate monomers, silanated silica
fillers, TEGDMA, initiators, stabilizers &
rheological additives.
Catalyst: methacrylate monomers, radiopaque
alkaline fillers (calcium hydroxide), silanated
silica, initiator, stabilizers, pigments, rheological
additives & fluorescence dye.
Scotchbond Universal
(Lot 7102413)
3M ESPE, St. Paul,
MN, USA
Ethanol, water, photo-initiator, silane, Bis-GMA,
HEMA, silica, 10-MDP, dimethacrylate resins,
Vitrebond™ Copolymer.
One Coat 7 Universal
(Lot H91194)
Coltène/Whaledent,
Altstätten,
Switzerland
Ethanol, water, photo-initiator, MDP, MMA-
modified polyacrylyic acid, UDMA, HEMA.
DuoCem
(Lot H94322)
Coltène/Whaledent,
Altstätten,
Switzerland
Bis-EMA, Bis-GMA, TEGDMA, zinc oxide,
silanated silica, dibenzoyl peroxide, sodium
fluoride.
Monobond Plus
(Lot W90333)
Ivoclar Vivadent,
Schaan,
Liechtenstein
Silane methacrylate, 10-MDP, ethanol sulphide
methacrylate

47
Continuation of table from previous page
Material Manufacturer Composition
Multilink Automix
(Lot W38653)
Ivoclar Vivadent,
Schaan,
Liechtenstein
Dimethacrylates, HEMA, benzoyl peroxide,
inorganic fillers, ytterbium trifluoride, initiator,
stabilizers, pigments.
RelyX Unicem 2
(Lot 3410073)
3M ESPE, St. Paul,
MN, USA
Base: Methacrylate monomers containing
phosphoric acid groups, methacrylate monomers,
silanated fillers, initiator, stabilizer, rheological
additives
Catalyst: Methacrylate monomers, silanated
fillers, alkaline fillers (calcium hydroxide),
initiator stabilizer, pigments rheological additives.
Ketac Cem Plus Automix
(Lot N914485)
3M ESPE, St. Paul,
MN, USA
Paste A: radiopaque fluoro-alumino-silicate glass,
opacifying agent, HEMA, water, a proprietary
reducing agent.
Paste B: zirconia silica filler, HEMA,
methacrylated polycarboxylic acid, Bis-GMA,
water & potassium persulfate.
TEGDMA: triethylene glycol dimethacrylate, UDMA: urethane dimethacrylate, Bis-GMA: Bisphenol
A glycidyl methacrylate, 10-MDP:10-methacryloyloxydecyl dihydrogenphosphate, HEMA:
hydroxyethyl methacrylate, Bis-EMA: Bisphenol A polyethethylene glycol diether dimethacrylate.
Table 11: Chemical composition of cements used in the study.

Bonding Procedure
The bonding surfaces of all specimens were treated with 50 μm aluminum oxide (Al 2O 3) particles (Cobra
50 μm white; Renfert, Hilzingen, Germany) at an air pressure of 2.8 bar using a fine blasting unit (Basic
Quattro IS; Renfert, Hilzingen, Germany) at a distance of 10 mm for 13 sec. The specimens were cleaned
ultrasonically in ethanol for 5 min, then rinsed with distilled water for 30 sec and air-dried.

48
Each hybrid material was divided into six groups (n=30 per group) based on the applied cement system:
1- Universal resin cement, dual-cure & universal bonding agent (Universalzement & Universalbond)
2- Resin cement, dual-cure & universal bonding agent (RelyX Ultimate & Scotchbond Universal)
3- Resin cement, dual-cure & light cure universal bonding agent (DuoCem & One Coat 7 Universal)
4- Resin cement, dual-cure & combination coupling agent (Multilink Automix & Monobond Plus)
5- Self-adhesive resin cement, dual-cure (RelyX Unicem 2)
6- Resin-modified glass-ionomer cement, self-cure (Ketac Cem Plus Automix)
The composite cylinders were bonded to the slices using the assigned cement according to its manufacturer
instructions. Table 11 summarizes the chemical compositions of the cements used in the study. The bonded
specimens were seated in a custom-made alignment device and loaded with 1 kg. Excess cement was
removed, and each specimen was light cured for 20 sec on each side using LED curing light (Elipar S10
Curing Light; 3M ESPE, St. Paul, MN, USA).
Artificial Aging
Following the same aging protocol in Chapter I, fifteen specimens from each group were tested for early
shear bond strength (SBS) after 24h storage in distilled water at 37 °C. The other fifteen specimens per
group were tested for late SBS after artificial aging by thermal cycling (THE-1100, SD Mechatronik,
Feldkirchen-Westerham, Germany) for 20,000 cycles at 5°C - 55°C with 30 sec dwell time and 10 sec
transfer time) and 6 months of storage in distilled water at 37°C.
Shear Bond Strength Testing
The bond strength was measured with notched-edge shear bond strength test (ISO 29022/2013) using a
notched crosshead (Crosshead assembly, Ultradent, South Jordan, UT, USA) mounted in a universal testing
machine (model 6596; Instron Corp, Norwood, Mass., USA) at a crosshead speed of 1 mm/min (
Figure 3) (22). SBS values were recorded in N and converted in MPa. Specimens, which de-bonded before
testing, were recorded as pre-test failures (PTFs).

49

Figure 11: Schematic representation of the study set.
Mode of Failure
Mode of failure (cohesive in CAD/CAM material, cohesive in composite, cohesive in cement, adhesive in
CAD/CAM material, adhesive in composite, mixed) were assessed with a stereo microscope (Wild M7;
Wild Herrbrugg AG, Heerbrugg, Switzerland) at x60 to x200 magnification and reported.

Material Characterization
Microstructural characterization of tested hybrid CAD/ CAM materials was performed with scanning
electron microscopy (SEM) for untreated (polished specimens) and sandblasted specimens as described in
Chapter I above.
The chemical characterization of the tested hybrid CAD/CAM materials was performed using micro-Raman
spectroscopy which is based on inelastic scattering of monochromatic light (laser source) resulting from
change in the frequency of light photons upon interaction with the sample. Photons are absorbed by the
sample and then reemitted with different frequency which is shifted up or down in comparison with original
frequency (called the Raman effect). This shift provides information about vibrational, rotational and other
low frequency transitions in molecules, and typically reported as wavenumbers (cm
-1
). Figure 12 illustrates
the components of Raman spectroscopy system and its mechanism of action.
50
Specimen of tested hybrid CAD/CAM materials were prepared following the same methodology above.
The analysis was conducted with a micro-Raman spectrometer (Renishaw Inc, Gloucestershire, UK)
equipped with a confocal microscope, whose operation is based on infrared light scattering excites the
studied matter. A HeNe laser beam with a wavelength of 532 nm and excitation power of 4 mW was focused
through a X100 Olympus objective to ~1 μm beam diameter. The device is equipped with an air-cooled
CCD detector. Raman spectra was acquired from surface of three hybrid CAD/CAM materials with
accumulation time of 60 sec each. Measurements were collected at a resolution of 0.5 cm
-1
in a spectral
region between 100 and 3200 cm
-1
. Spectra were Raman shift frequency-calibrated using known lines of
silicon. All spectra were placed on the same baseline and normalized with the aid of Wire 3.4 software
(Renishaw Inc, Gloucestershire, UK).

Figure 12: Schematic representation of Raman Spectroscopy components and mechanism of action

51
Early SBS Late SBS
LUUE, Lava Ultimate-Universalzement-early
LURE, Lava Ultimate-RelyX Ultimate-early
LUDE, Lava Ultimate-DuoCem-early
LUME, Lava Ultimate-Multilink-early
LUXE, Lava Ultimate-RelyX Unicem-early
LUKE, Lava Ultimate- Ketac Cem Plus-early
LUUL, Lava Ultimate-Universalzement-late
LURL, Lava Ultimate-RelyX Ultimate-late
LUDL, Lava Ultimate-DuoCem-late
LUML, Lava Ultimate- Multilink-late
LUXL, Lava Ultimate-RelyX Unicem-late
LUKL, Lava Ultimate- Ketac Cem Plus-late
LCUE, LuxaCam-Universalzement-early
LCRE, LuxaCam-RelyX Ultimate-early
LCDE, LuxaCam-DuoCem-early
LCME, LuxaCam-Multilink-early
LCXE, LuxaCam-RelyX Unicem-early
LCKE, LuxaCam-Ketac Cem Plus-early
LCUL, LuxaCam-Universalzement-late
LCRL, LuxaCam-RelyX Ultimate-late
LCDL, LuxaCam-DuoCem-late
LCML, LuxaCam- Multilink-late
LCXL, LuxaCam-RelyX Unicem-late
LCKL, LuxaCam- Ketac Cem Plus-late
CSUE, Cerasmart-Universalzement-early
CSRE, Cerasmart-RelyX Ultimate-early
CSDE, Cerasmart-DuoCem-early
CSME, Cerasmart- Multilink-early
CSXE, Cerasmart-RelyX Unicem-early
CSKE, Cerasmart- Ketac Cem Plus-early
CSUL, Cerasmart-Universalzement-late
CSRL, Cerasmart-RelyX Ultimate-late
CSDL, Cerasmart-DuoCem-late
CSML, Cerasmart- Multilink-late
CSXL, Cerasmart-RelyX Unicem-late
CSKL, Cerasmart- Ketac Cem Plus-late
Table 12: List of tested groups classified by aging
52
Statistical Analysis
Statistical analysis of the data was performed with a 3-way analysis of variance (ANOVA) model using
Bonferroni post-hoc multiple comparisons, with an overall significance level of α = 0.05. The dependent
variable was shear bond strength (in MPa), and the three factors used for analysis were: 1) aging, 2)
material, and 3) cement. Furthermore, data was stratified by aging (early SBS and late SBS), and 2-way
ANOVA models using Bonferroni post-hoc multiple comparisons were performed.
Pre-test failures (PTFs) were excluded from the analysis to allow the use of more powerful parametric tests.
All data were transformed using a square root transformation to meet the normality assumption. Although
the homogeneity of variance assumption was violated (Levene’s test, P=0.00174), ANOVA is generally
considered robust to any homogeneity of variance issues in balanced datasets. Statistical software (STATA
15.1; College Station, TX: StataCorp LLC) was used for calculations.
53
Results
The mean values of shear bond strength (SBS) and standard deviation (SD) are listed in Table 13 and
illustrated in Figure 13. There were 90 out of 540 (16.73%) specimens recorded as pre-test failures (PTFs)
which were excluded from the analysis. All PTFs were specimens bonded with RMGI (Ketac Cem Plus).
Mean SBS was compared across the two levels of aging, three materials, and five cements (Ketac Cem Plus
was excluded as all specimens were PTFs) and the data were analyzed with a 3-way ANOVA model. All
main factors of aging, material, and cement were statistically significant (P<0.001). All two-way
interactions were significant; aging x cement, material x cement, and aging x material (P<0.001). Three-
way interaction aging x material x cement was statistically significant as well (P<0.001).
In order to simplify the interpretation of the main effects and interactions, data was stratified by aging, and
2-way ANOVA model was used to test materials and cements differences of the early and late SBS data
separately. The overall 3-way ANOVA and the 2-way ANOVAs are summarized in Table 14. The 2-way
ANOVA for both early SBS and late SBS showed significant F-test values for the main effects of material
and cement (P<0.05). Two-way interaction between material x cement was also statistically significant
(P<0.001).
54

(Material: LuxaCam Composite – LC; Lava Ultimate – LU; CS – Cerasmart, Cements:
Universalzement– U; Relyx Ultimate– R; DuoCem – D; Multilink Automix – M; Relyx Unicem 2
– X, Aging: Early – E; Late – L)
Figure 13: Box plots of shear bond strength in MPa
55

Group
LuxaCam (LC) Lava Ultimate (LU) Cerasmart (CS)
Mean ± SD Mean ± SD Mean ± SD
Early Shear Bond Strength (E)
Universalzement (U) 37.05 ± 9.08
A
40.00 ± 12.31

24.44 ± 7.68
Aa
Relyx Ultimate (R) 34.34 ± 9.77
AC
46.09 ± 12.86 21.13 ± 11.07
ABa
DuoCem (D) 50.83 ± 7.39
B
50.47 ± 7.90 17.21 ± 6.49
ABa
Multilink Automix (M) 40.31 ± 6.06
AB
46.37 ± 11.06 15.28 ± 6.77
Ba
Relyx Unicem 2 (X) 24.82 ± 13.39
C
44.21 ± 8.25
a
27.06 ± 10.62
A
Ketac Cem Plus (K) 00.00 ± 00.00* 00.00 ± 00.00* 00.00 ± 00.00*
Late Shear Bond Strength (L)
Universalzement (U) 29.41 ± 5.57
A
28.62 ± 7.50
A
20.07 ± 9.32
Aa

Relyx Ultimate (R) 10.86 ± 3.90

29.88 ± 8.80
Aa
12.47 ± 2.88
B

DuoCem (D) 7.54 ± 1.97
a
27.43 ± 11.56
A
19.21 ± 4.96
AC

Multilink Automix (M) 6.68 ± 1.92

7.42 ± 7.85 22.83 ± 7.69
Aa

Relyx Unicem 2 (X) 8.41 ± 2.20
a
9.90 ± 2.70
ab
13.98 ± 4.12
BCb

Ketac Cem Plus (K) 00.00 ± 00.00* 00.00 ± 00.00* 00.00 ± 00.00*
Different lower-case letters in the same row indicate significant differences
Different UPPER-case letters in the same column indicate significant differences among same aging groups
* Excluded from statistical analysis
Table 13: Mean shear bond strength (MPa) and standard deviation (SD)

56
Source Sum of Squares df Mean Square F p-value
3-way
Aging 359.367 1 359.367 512.15 <0.001
Material 110.406 2 55.203 78.67 <0.001
Resin Cement 122.361 2 61.181 87.19 <0.001
Aging x Material 62.555 4 15.639 22.29 <0.001
Aging x Resin Cement 41.952 4 10.488 14.95 <0.001
Material x Resin Cement 57.804 8 7.226 10.3 <0.001
Aging x Material x Resin Cement 109.581 8 13.698 19.52 <0.001
Residual 293.304 418 0.702
Total 1156.440 447 2.587
2-way for early shear bond strength
Material 196.111 2 98.056 112.55 <0.001
Resin Cement 8.686 4 2.171 2.49 0.044
Material x Resin Cement 55.609 8 6.951 798 <0.001
Residual 182.078 209 0.871
Total 443.422 223 1.988
2-way for late shear bond strength
Material 36.655 2 18.328 34.44 <0.001
Resin Cement 96.226 4 24.056 45.20 <0.001
Material x Resin Cement 111.569 8 13.946 26.21 <0.001
Residual 111.226 209
Total 355.902 223
Table 14: Summary of 3-way and 2-way ANOVA for SBS conducted at each level of interacting factor
57
Effect of the Cement
I. Early Shear Bond Strength
Mean SBS of LuxaCam Composite ranged from 24.82 to 50.83 MPa. DuoCem group presented the highest
SBS which was statistically similar to Multilink Automix (P>0.05). LCUE ranked third which was not
significantly different than LCME and LCRE (P>0.05). RelyX Unicem 2 group was statistically lower than
all groups (P<0.05) except LCRE (P>0.05).
Lava Ultimate had mean SBS ranged from 40.00 to 50.47 MPa. The highest mean SBS was reported for
DuoCem group which performed similarly compared to all cement systems (P=1.00). Mean SBS of
Cerasmart ranged from 15.28 to 27.06 MPa. RelyX Unicem 2 had the highest SBS but it was not
significantly different from other cements groups (P>0.05) except CSME (P<0.05). Additionally, there was
no statistical difference between CSME, CSDE, and CSRE (P>0.05).
II. Late Shear Bond Strength
Mean SBS of LuxaCam Composite ranged from 6.68 to 29.41 MPa. Universalzement group was
significantly higher than all other cement systems (P<0.001). There was no significant difference across
the other cements (P>0.05).
Mean SBS of Lava Ultimate ranged from 7.42 to 29.88 MPa. RelyX Ultimate had highest SBS which was
statistically similar to LUUL and LUDL (P=1.00). Multilink Automix group reported the lowest bonding
performance which was not significantly different than LUXL (P>0.05).
Cerasmart had mean SBS ranged from 12.47 to 22.83 MPa. Multilink Automix had the highest SBS but
there was no significant difference when compared to CSUL and CSDL (P=1.00). RelyX Unicem 2 group
was significantly lower than other cement systems (P<0.05) except CSRL and CSDL (P>0.05).

58

Figure 14: Mean (early & late) SBS (in MPa) presented by restorative material.

Effect of Restorative Material
I. Early Shear Bond Strength
LuxaCam Composite and Lava Ultimate presented no significant difference in mean SBS with all cements
(P<0.05) except Relyx Unicem 2 (P<0.001). Cerasmart reported significantly lower mean SBS than other
materials (P<0.05) except when comparing CSXE and LCXE (P=1.00)
II. Late Shear Bond Strength
There was no significant difference in mean SBS of Lava Ultimate and LuxaCam Composite when bonded
with Universalzement, Relyx Unicem 2, and Multilink Automix cements (P=1.00). However, Lava
Ultimate performed better when bonded with DuoCem and Relyx Ultimate (P<0.001).
Lava Ultimate reported statistically higher mean SBS compared to Cerasmart when bonded with
Universalzement and RelyX Ultimate (P<0.05). However, it was statistically lower when Multilink
Automix cement was used (P<0.001). Both materials performed similarly with DuoCem and Relyx Unicem
2 (P>0.05).
Early SBS Early SBS Early SBS
Late SBS Late SBS Late SBS
59
Cerasmart showed significantly higher SBS compared to LuxaCam Composite when bonded with DuoCem,
Multilink Automix and Relyx Unicem 2 (P<0.05). This difference in SBS was not significant when Relyx
Ultimate was used (P=1.00). LuxaCam Composite reported statistically higher SBS compared using
Universalzement (P<0.05).
Figure 15: Mean (early & late) SBS (in MPa) presented by luting cement

Late SBS Late SBS Late SBS
Late SBS Late SBS Late SBS
Early SBS Early SBS Early SBS
Early SBS Early SBS Early SBS
60
Effect of Aging
The effect of aging on SBS was significant among all groups (P<0.05) except LCU, CSU, CSR, CSD, CSM
groups (P>0.05). Generally, early SBS presented higher values than late SBS except when Cerasmart was
bonded with DuoCem and Multilink Automix cements. These two groups showed higher late SBS, but it
was not statistically significant (P>0.05).

Mode of Failure
Analysis of total sample showed mainly cohesive failure at CAD/CAM material (47.03%), followed by
adhesive failure at CAD/CAM interface (32.27%), mixed failures (12.45%) and adhesive failure at the
composite interface (2.23%). Detailed mode of failure for each group is presented in Figure 16 and Table
15.
Table 15: Frequency and percentage of failure mode by group

Figure 16: Mode of failure

61
Failure Mode, N (row %)
Group
Cohesive in
CAD/CAM
Cohesive
in
composite
Cohesive
in
cement
Adhesive
at
CAD/CAM
Adhesive
at
Composite
Mixed Total
LUUE 11 (78.57) 0 (0.00) 1 (7.14) 2 (14.29) 0 (0.00) 0 (0.00) 14 (100.00)
LURE 5 (3.33) 2 (13.33) 0 (0.00) 0 (0.00) 0 (0.00) 8 (53.33) 15 (100.00)
LUDE 6 (40.00) 0 (0.00) 0 (0.00) 3 (20.00) 0 (0.00) 6 (40.00) 15 (100.00)
LUME 4 (26.67) 0 (0.00) 0 (0.00) 4 (26.67) 1 (6.67) 6 (40.00) 15 (100.00)
LUXE 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUKE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCUE 13 (86.67) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 2 (13.33) 15 (100.00)
LCRE 11 (73.33) 0 (0.00) 0 (0.00) 0 (0.00) 2 (13.33) 2 (13.33) 15 (100.00)
LCDE 9 (60.00) 0 (0.00) 2 (13.33) 0 (0.00) 2 (13.33) 2 (13.33) 15 (100.00)
LCME 13 (86.67) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 2 (13.33) 15 (100.00)
LCXE 12 (80.00) 0 (0.00) 1 (6.67) 0 (0.00) 1 (6.67) 1 (6.67) 15 (100.00)
LCKE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSUE 15 (100.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSRE 11 (73.33) 1 (6.67) 1 (6.67) 1 (6.67) 1 (6.67) 0 (0.00) 15 (100.00)
CSDE 12 (80.00) 0 (0.00) 1 (6.67) 1 (6.67) 0 (0.00) 1 (6.67) 15 (100.00)
CSME 11 (73.33) 0 (0.00) 2 (13.33) 0 (0.00) 1 (6.67) 1 (6.67) 15 (100.00)
CSXE 9 (60.00) 0 (0.00) 0 (0.00) 5 (33.33) 0 (0.00) 1 (6.67) 15 (100.00)
CSKE 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LUUL 9 (60.00) 0 (0.00) 0 (0.00) 4 (26.67) 0 (0.00) 2 (13.33) 15 (100.00)
LURL 0 (0.00) 0 (0.00) 3 (20.00) 7 (46.67) 2 (13.33) 3 (20.00) 15 (100.00)
LUDL 7 (46.67) 1 (6.67) 1 (6.67) 3 (20.00) 0 (0.00) 3 (20.00) 15 (100.00)
LUML 1 (6.67) 0 (0.00) 0 (0.00) 12 (80.00) 0 (0.00) 2 (13.33) 15 (100.00)
LUXL 5 (35.71) 0 (0.00) 0 (0.00) 5 (35.71) 0 (0.00) 4 (28.57) 14 (100.00)
LUKL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
LCUL 0 (0.00) 0 (0.00) 2 (13.33) 7 (46.67) 0 (0.00) 6 (40.00) 15 (100.00)
LCRL 10 (66.67) 0 (0.00) 3 (20.00) 1 (6.67) 1 (6.67) 0 (0.00) 15 (100.00)
LCDL 4 (26.67) 0 (0.00) 4 (26.67) 3 (20.00) 0 (0.00) 4 (26.67) 15 (100.00)
LCML 8 (53.33) 0 (0.00) 0 (0.00) 7 (46.67) 0 (0.00) 0 (0.00) 15 (100.00)
LCXL 11 (73.33) 0 (0.00) 0 (0.00) 1 (6.67) 0 (0.00) 3 (20.00) 15 (100.00)
LCKL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
CSUL 6 (40.00) 0 (0.00) 1 (6.67) 7 (46.67) 0 (0.00) 1 (6.67) 15 (100.00)
CSRL 11 (73.33) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 4 (26.67) 15 (100.00)
CSDL 9 (60.00) 0 (0.00) 0 (0.00) 5 (33.33) 1 (6.67) 0 (0.00) 15 (100.00)
CSML 2 (13.33) 0 (0.00) 0 (0.00) 11 (73.33) 0 (0.00) 2 (13.33) 15 (100.00)
CSXL 13 (86.67) 0 (0.00) 1 (6.67) 0 (0.00) 0 (0.00) 1 (6.67) 15 (100.00)
CSKL 0 (0.00) 0 (0.00) 0 (0.00) 15 (100.00) 0 (0.00) 0 (0.00) 15 (100.00)
Total 253 (47.03) 4 (0.74) 23 (4.28) 179 (32.27) 12 (2.23) 67 (12.45) 538 (100.00)
Table 15: Frequency and percentage of failure mode by group

62
Material Characterization
Microstructural characterization of tested hybrid CAD/ CAM materials was performed with scanning
electron microscopy (SEM). The results of the examination are discussed in Chapter I above.
Chemical characterization of tested materials was performed using micro-Raman microscopy. The acquired
Raman spectra were placed on the same baseline and normalized with the aid of Wire 3.4 software
(Renishaw Inc, Gloucestershire, UK). The Raman spectra for three hybrid CAD/CAM materials revealed
vibrations of both the organic and inorganic components which are presented in Figure 17.
The position of the peaks indicated the molecular structure of the hybrid materials. Functional group of
inorganic matrices occurred at the 3100-1200 cm
-1
region. In all three Raman spectra, small and broad peaks
were identified at the 400–1000 cm
-1
region, indicating the presence of inorganic components (fillers).
Table 16 shows the bands and functional groups identified as possible chemical interaction.

Raman Shift (cm
-1
) Assignment
1638, 1450 C=C (carbon double bond)
1608 C-C (carbon single bond)
1721 C=O (carbonyl group)
1114 C-O-C (ether group)
2900-3000 C-H (carbon-hydrogen bond)
3100 O-H (hydroxyl group)
1300 CH 3 (methacrylate group)
1187 [CH 3] 2 –C (Gem- dimethyl -Bis-GMA)
1247 Si-O-Si (asymmetrical siloxane)
797 Si-O-Si (symmetrical siloxane)
640, 463 t-ZrO 2 (tetragonal zirconia)
750 AL 2O 3 (alumina)
Table 16: Raman shift of functional groups identified as possible chemical interaction.

63
The height of the peak revealed the intensity of the substance showing the most intense band associated
with the organic component of the resin matrix. Comparison between the three tested materials presented
different concentration of resin matrix with LC contained the most organic component followed by CS and
lastly LU as expected. The inorganic component (fillers) presented decreased intensity of the Raman bands
which are rather scanty and incomplete. Furthermore, the width of the peaks is an indication of the
crystalline quality and homogeneity of the material. The tested material presented mostly broad peaks
specially in LC and LU compared to CS, referring to the inhomogeneous distribution of the fillers into the
materials.
64
Figure 17: Raman spectra of hybrid CAD/CAM materials (Lava Ultimate, LuxaCam Composite and Cerasmart)
65
Discussion
The first null hypothesis, that the factor restorative material has no significant effect on SBS, was rejected.
The bonding behavior of the tested hybrid CAD/CAM materials varied regardless of the used luting cement
due to differences in the microstructure and chemical composition (16, 29, 62). The present study reported
that the long-term performance of Lava Ultimate (LU) was better than Cerasmart (CS), followed by
LuxaCam Composite (LC) which ranked last. This finding may be related to the composition of the tested
materials (Table 4) as different organic matrices and filler compositions are reported to react differently
during surface treatment (30). The high percentage of organic matrix in LC and CS, compared to the highly
filled LU, make these materials more sensitive to sandblasting (42). Moreover, LU contains smaller fillers
and larger cluster particles which cannot easily be detached from the material surface during sandblasting
(42, 43).
Based on the Results of Chapter I, all specimens were treated with 50 μm aluminum oxide (Al 2O 3) particles
following the same protocol for standardization as the roughness of the sandblasted surface can be affected
by the type of the powder, its particles size, applied air pressure, duration and distance as previously
discussed in Chapter I above. A previous study (20) reported that excessive sandblasting in terms of particle
size, duration, and applied pressure can be deleterious for resin-matrix ceramic materials causing cracks of
1-10 μm length. To avoid this, mild sandblasting was applied in our study following the parameters
recommended for resin-matrix CAD/CAM materials (20). Although sandblasting parameters were
standardized for all tested materials, its effect may vary on the surface roughness, depending on the hardness
of the sandblasted material.
Another explanation of the bond strength differences between the tested materials could be the mechanical
properties of these materials which is also related to their chemical composition (42). For example, surface
hardness was reported to be influenced by the load and type of inorganic fillers (42). Supporting our
findings, a previous study (42) reported higher Vickers hardness (HV) for hybrid CAD/CAM materials with
66
higher fillers load. Another study (43) noted that the type of fillers had an effect on surface hardness
explaining that barium-glass particles have lower hardness opposed to the zirconia particles, consequently
making the surface of zirconia-containing materials more resistant to mechanical roughening. This is
consistent with the results that stated that LU performed better than CS and LC.
These findings are supported by SEM images (Figure 8) showing the polished specimens of the tested
materials with different microstructure. LU presented a characteristic microstructure in the form of
agglomerated and non-agglomerated filler particles embedded in the resin matrix, while LC and CS were
relatively similar exhibiting uniformly distributed particles embedded in the resin matrix. The effect of
sandblasting on the surface roughness was prominent. LC presented deeper grooves and evident undercuts
compared to LU and CS Figure 8.
Despite the similar microstructural characterizations of LC and CS, their bonding performance differed.
This may be attributed to the discrepancies in the chemical composition of the two materials which is often
incomplete or mislabeled by the manufacturers (42). All tested materials contain SiO 2 particles which react
with silane contributing to the bond strength (38). CS also contains Ba glass particles which have similar
reaction with silane. LU contains ZrO 2 which chemically react with 10-MDP providing a higher bond
strength value (30). Similar reaction is assumed to occur between 10-MDP and Al₂O₃ fillers in CS.
However, the magnitude of effect on the bond strength is related to the filler’s concentration in the material
(39). In the present study, micro-Raman spectroscopy was used to characterize the chemical components
of tested hybrid CAD/CAM materials. Siloxane bond (Si-O-Si) was detected in all tested materials with is
attributed to the bond between the silane (identified by the presence of C=C and C=O) with silica Figure
17. Other inorganic fillers were more difficult to detect due to decreased intensity of the Raman bands
which was insufficient for a valid comparison between the hybrid CAD/CAM materials. This can be
explained by the fact that the intensity of bands depends on the position on the surface that each spectrum
is collected which is related to the inhomogeneity of the sample's surface (36, 64). Another factor is the
fluorescence effect which causes interference with the Raman spectrum of zirconia and alumina (64, 69).
67
The use of an exciting laser with shorter wavelength or higher wavelength (infrared) would be preferable
in such case (64).
The second null hypothesis, that luting cement had no significant effect on SBS, was rejected. Based on the
luting cement, the tested materials had significantly different performance in the long-term. LC reported
high SBS when combined with Universalzement, all other resin cements reported values below the
acceptable range (15-25 MPa) (34). LU performed best when bonded with Universalzement, DuoCem and
Relyx Ultimate which were not statistically significant from each other. Finally, CS performed better than
other materials only when combined with Multilink Automix cement which was not statistically significant
than Universalzement. In the long-term, all tested materials SBS below acceptable bond range (15-25 MPa)
when bonded with self-adhesive resin cement (RelyX Unicem 2) Table 13 (34).
Consistent with the results of the present study, previous studies (6, 16, 29) stated that the chosen cements
had a significant effect on bond strength of the restoration. Resin cements vary widely in their physical
properties because of the variety and proportions of resins and fillers in their formulas. Other studies (6,
56) also reported that the properties of resin cements are influenced by the filler type and size, filler load,
silane coupling agent, nature of the resin matrix, degree of porosity, and degree of conversion. Moreover,
the addition of different chemical components such as functional monomers to the cement and/or the
combined adhesive system affect the chemical characteristics of the product (13, 14, 18, 37). The tested
resin cements had different chemical compositions in term of type of resin monomers, initiator components,
stabilizers, inorganic fillers, pigments and other additives as listed in Table 11.
The fact that the tested luting cements were used in different bonding protocols as we followed the
manufacturers’ instructions of the commercially available products could be of an influence. This factor
could be addressed as a limitation of the methodology; however, it reflects the clinical situation. While
some cements (Universalzement, RelyX Ultimate, and DuoCem) were combined with universal adhesive
agents, others (Multilink Automix) were used with a combination coupling agent or no agent at all (RelyX
68
Unicem 2, and Ketac Cem Plus Automix). These agents differ in their chemistry (Table 11) such as type of
resin, solvent, presence or absence of functional molecules (e.g MDP, silane, and MMA-modified
polyacrylic acid) which determine their bonding potentials. Furthermore, it is well known that the properties
of the resin cements are dominated by the used adhesive system rather than the cement itself (6). Further
information could be collected from chemical analysis of the bonding interface to reveal the chemical
interaction at the molecular level. However, the aim of this study was to evaluate the effect of the restorative
material’s chemical composition on its bonding performance rather than the chemical reaction at bonding
interface.
Luting cements have distinguished mechanism interacting with the bonding substrate; 1) some bond
chemically to the tooth only such as glass ionomer (GI) and resin modified glass ionomer (RMGI) cements,
2) some are micromechanically retained to the pre-treated bonding substrate (tooth and restoration) such as
conventional resin cements, 3) others combine chemical and micromechanical retention to the tooth and
some restorative substate such as self-adhesive resin cements (6). The chemistry of the luting cements plays
an important role in determining their physical, mechanical and bonding properties (Table 9) (6). These
discrepancies between the nature of the cement influence their clinical indication and long-term
performance (26, 31, 70). RMGI is a hybrid cement that combines a glass powder, such as used in GI, and
a polymerizable liquid attached to the polyacrylic acid. The addition of resin to the mixture improved the
mechanical and handling properties of RMGI compared to conventional GI, but it is still weaker and more
soluble compared to resin cements (40). Furthermore, self-adhesive resin cements are mechanically
stronger than non-resin cements, but weaker than conventional resin cements.
Recently introduced self-adhesive resin cements presented a promising result in bonding zirconium oxide
restorations due to the presence of functional acidic monomers (13, 31). A study also presented significantly
higher bond strengths of Lava Ultimate bonded with a self-adhesive resin cement compared to a
conventional resin cement (71). However, other in vitro studies (16, 29) showed that it is still inferior to
total-etch and self-etch bonding systems when bonding to indirect composites which is in agreement with
69
the current finding. A self-adhesive resin cement is a self-etching material during the initial stages of its
chemical reaction. Its low pH and high hydrophilicity at early stages after mixing yields good wetting of
tooth structure and promotes surface demineralization (72).

As the reaction progresses, the acidity of the
cement is gradually neutralized because of the reaction with the apatite from dental substrates

and with the
metal oxides present in the basic, acid-soluble inorganic fillers. As the hydrophilic and acidic monomers
are consumed, the cement becomes more hydrophobic, which minimizes water sorption, hygroscopic
expansion, and hydrolytic degradation (72).

If the bonding substrate is mostly comprised of resin material,
a metal casting, or any material other than dental substrate, the necessary neutralization of the acidic
monomers can be significantly affected resulting in residual amounts of acidity (72). Consequently, the
polymerization reaction of the cement is compromised which results in increased water sorption impacting
the durability of the indirect restoration (16, 72). This explains the bonding behavior of the tested self-
adhesive resin cements (RelyX Unicem 2) bonded to the hybrid materials as it presented high early SBS,
but it dramatically deteriorated after artificial aging due to incomplete pH neutralization that affected the
polymerization.
Artificial aging has been used by several in-vitro studies (26, 43, 44) to simulate changes in the oral
environment and create clinically relevant testing parameters. The presence of water and repeated thermal
changes in the mouth subject the bonding interface to continuous chemical and mechanical degradation as
discussed in Chapter I (44, 45). The current study used long-term water storage (6 months of storage in
distilled water at 37°C) and thermal cycling (20K cycles at 5°C - 55°C) where all assigned specimens
followed the same aging protocol for standardization (35, 44). Our results indicated that the bond strength
decreased after subjecting the bonded specimen to artificial aging which is consistent with data from other
studies (1, 19). Therefore, the third null hypothesis, that aging has no effect on SBS, was rejected.
The tested materials presented mostly similar early SBS but their bonding performance differed
significantly after aging regardless of the luting cement (Table 13). This finding can be explained by the
fact that CAD/CAM materials age differently due to differences in chemical composition (73). Sonmez et
70
al. (74) reported that simulated aging strongly affected resin-matrix materials more than glass-based
ceramic materials which was explained by differences in microstructure as the resin-matrix material has
inorganic filler particles embedded in a polymer matrix without interconnections allowing water penetration
into the resin matrix and therefore degrading the restorative material. The tested CAD/CAM materials are
similar in form of resin-matrix ceramics, however, discrepancies in the filler load could explain the results.
LU, which had better overall bonding performance than the other two materials, had a higher filler load (80
wt%) compared to CS (71 wt%) and LC (70 wt%) (74).
Another aspect to explaining these results is the different effect of aging on the luting cements which is
related to their different physical and mechanical properties (75). Considering the various strength values,
modulus of elasticity, wear resistance, solubility and water sorption, the durability of various classes of
cements can be ranked (6, 71). The chemical components of the luting cements highly impact these
characterizations. The tested cements are subjected to tensile stresses at shear bond strength testing, higher
SBS values would be expected for cements with higher tensile strength. This is consistent with our findings
as conventional resin cements with tensile strength of 62-77 MPa reported higher SBS compared to self-
adhesive resin cement with tensile strength of 34 MPa (31). Another factor is that self-adhesive resin
cements are more prone to water sorption compared to conventional resin cements (46).
The sorption phenomenon in resin-based materials is a diffusion-controlled process that causes chemical
degradation by releasing residual monomer and debonding of fillers (46). It can be explained based on two
theories: the free volume theory which involves solvent absorption through voids in the polymer, and the
interaction theory where the water binds to specific ionic groups of the polymer chain depending on the
water affinity of these groups (47). The absorbed water may result in swelling and widening of spaces
between polymer chains depending on the degree of cross-link density of its structure. This allows free
unreacted monomers trapped in the polymer network to diffuse out into the storage solvent depending on
their molecular size and their affinity to the aqueous solvent (47).
71
Different levels of sorption and solubility are observed in luting cements because of the differences in their
chemical composition, mainly the organic matrices (75).

The number of hydrophilic components,

cross-
linking density and porosity,

and the polarity of the components in the formulation have been shown to play
an important role in these properties. For example,

Bis-EMA and UDMA based resins appear to be more
hydrophobic and resistant to sorption and solubility than Bis-GMA based systems. TEGDMA and HEMA,
on the other hand, appear to be highly hydrophilic and more susceptible to moisture uptake and solubility
(75). Beside Bis-GMA monomer, which was a component in most of tested cements, some cements
contained HEMA, such as Multilink Automix and Ketac Cem Plus Automix cements, explaining their poor
performance at the testing conditions (presence of water). On the other hand, the inclusion of Bis-EMA in
the chemical formula of DuoCem could explain its good performance despite aging (75). The degree of
conversion (DC) and the number of unreacted monomers in the cement are additional factors to consider
as self-cure cements are reported to have lower DC compared to dual-cure cement (6, 7). The tested RMGI
is a self-cure cement and more soluble than the other two classes of cements (conventional and self-adhesive
resin cements) leading to more water uptake which causes expansion of up to 8 vol% in the cement (6, 7).
This could explain why tested RMGI had a high number of pre-test failure (PTFs).
The bonding performance of CAD/CAM restorative materials have been an interest of many studies
which used different testing methodologies to evaluate the bond strength (1, 26, 43, 44, 49). Shear bond
strength (SBS) test is a reliable method and widely used but the non-uniform interfacial stresses have
been a concern as it might lead to misinterpretation of the results (28, 53, 54). In the present study, notch-
edge configuration was used to measure SBS of hybrid CAD/CAM materials to different cements as it
provides better stress distribution across the bonding interface (22). Regarding the failure modes of tested
materials, cohesive failures in CAD/CAM material was observed specially in specimen tested for early
SBS (Figure 16), which may indicate that the bond between the restorative materials and cement seemed
to exceed the strength of the CAD/CAM material (35). Adhesive failures at CAD/CAM material were
72
also observed which indicate the validity of the applied testing method (35).

The total sample presented 16.73% as pre-test failures (PTFs) which were excluded from the analysis. PTFs
have been handled in dental research by two ways (55). First, include them in the statistical analysis by
assigning the lowest measured value or zero which is very likely to cause losing the normal distribution of
data, especially with a high number of PTFs, with the further consequence that parametric tests cannot be
used. Second, exclude them and simply compute the values of the specimens that were able to be tested. If
there are too many PTFs, it is obvious that the values reported are higher for groups that exclude PTFs
compared to relatively lower bond strength measured for groups that include PTFs (55). Many scientific
journals require the authors to report the number of PTFs and to describe how they were handled, because
much information could be derived from the incidence of PTFs. In our study, all PTFs were recorded among
the same tested cement; all specimens bonded with RMGI cement debonded before testing. The exclusion
of PTFs from the analysis preserved the normal distribution and allowed the use a more powerful parametric
test (ANOVA) compared to nonparametric tests without causing misrepresentation of the tested materials.
The present study combined bond strength test with different analytical techniques (SEM and micro-Raman
spectroscopy) aiming to provide complementary information in regard to the microstructure of hybrid
CAD/CAM materials and their chemical composition that may contributed to their bonding behavior. SEM
technique have been widely used in combination with in-vitro bond strength tests (57) revealing valuable
information in regard to the adhesion mechanism, the quality of the bonding interface and the mode of
failure of the bonded specimens. It is also of great relevance in analyzing the performance of dental
materials in relation to their microstructure (58, 63). However, it provides limited information about the
chemical compositions and chemical interactions (58, 63). For this purpose, a chemical analytical technique
is needed to provide information about the chemical characters of a specific material and the dynamic of
chemical reaction. Raman spectroscopy has been used in dental research studying different aspects such as
the degree of conversion (DC), tooth demineralization and remineralization, and material’s setting reaction
73
by following the changes in a peak of interest (36, 76, 77). For example, a previous study (36) used micro-
Raman spectroscopy to quantify DC of the adhesives across the bonding interface as it is able to extract
information in a minute area of ~ 1 μm in high resolution. The DC of the adhesives was quantified by
tracking changes in the band intensities of C=C at 1638 cm
-1
in relation to the reference band C—C at 1608
cm
-1
before and after polymerization (36).
The finding of our study revealed that the bonding performance of the luting cement was material
dependent. In another words, the same cement presented different bonding behavior with different hybrid
CAD/CAM materials referring to that certain restorative material/luting cements combination are more
chemically compatible than others. To confirm this, chemical analysis of the bonding interface is needed to
evaluate the dynamic interaction at the molecular level. Due to the methodology of our study testing
different cements, it would be challenging to define a peak of interest to track along the bonding interface
as chemistry of the tested cements are different. Another challenging point would be locating the
restoration-cement interface as the tested restoration and cements both are resin-based materials sharing
similar peaks. Previous studies (36, 77) have assessed the adhesive-dentin interface which is easier to locate
by identifying the phosphate of the dentin at 960 cm
-1
. Despite these limitations, the implementation of
micro-Raman spectroscopy in our study added value to our data as it chemically characterized the tested
hybrid CAD/CAM materials, and we were able to correlate their chemical components to their bonding
behavior achieving our set aim.

74
Conclusion
It can be concluded that luting performance of hybrid CAD/CAM materials can be affected by the selected
restorative material, luting cement and bonding protocol. The long-term luting behavior of hybrid
CAD/CAM restorative material depend on the material’s composition and microstructure in term of type
of fillers, size, shape, and load, as well as the organic matrix. Additionally, the durability of bond strength
of luting cement depends on the physical and mechanical properties which are dictated by its chemistry.
Certain combination of restorative material and luting cement presented more favorable outcome indicating
different level of chemical compatibility. Chemical analysis of the bonding interface is needed to evaluate
the dynamic at molecular level. The current study aimed to offer consistent guidance regarding the clinical
protocol for luting; considering the findings, it is clear that optimal bonding protocol and consequently
clinical retention is material dependent and closely following the respective manufacturer’s instructions is
warranted at this time.

75
References
1. Campos F, Almeida CS, Rippe MP, de Melo RM, Valandro LF, Bottino MA. Resin Bonding to a
Hybrid Ceramic: Effects of Surface Treatments and Aging. Oper Dent. 2016;41(2):171-8.

2. Zhang Y, Kelly JR. Dental Ceramics for Restoration and Metal Veneering. Dent Clin North Am.
2017;61(4):797-819.

3. Mormann WH, Brandestini M, Lutz F, Barbakow F. Chairside computer-aided direct ceramic
inlays. Quintessence Int. 1989;20(5):329-39.

4. Zaruba M, Mehl A. Chairside systems: a current review. Int J Comput Dent. 2017;20(2):123-49.

5. Gracis S, Thompson VP, Ferencz JL, Silva NR, Bonfante EA. A new classification system for all-
ceramic and ceramic-like restorative materials. Int J Prosthodont. 2015;28(3):227-35.

6. Duarte S, Sartori N, A S, JH P. Adhesive resin Cements for Bonding Esthetic Restorations : a
review. Quintessence Dent Technolo. 2011;34:40-66.

7. Awada A, Nathanson D. Mechanical properties of resin-ceramic CAD/CAM restorative
materials. J Prosthet Dent. 2015;114(4):587-93.

8. Blatz MB, Sadan A, Kern M. Resin-ceramic bonding: a review of the literature. J Prosthet Dent.
2003;89(3):268-74.

9. Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel
surfaces. J Dent Res. 1955;34(6):849-53.

10. Nakabayashi N, Kojima K, Masuhara E. The promotion of adhesion by the infiltration of
monomers into tooth substrates. J Biomed Mater Res. 1982;16(3):265-73.

11. Pashley DH, Tay FR, Breschi L, Tjaderhane L, Carvalho RM, Carrilho M, et al. State of the art
etch-and-rinse adhesives. Dent Mater. 2011;27(1):1-16.

12. Van Meerbeek B, Yoshihara K, Yoshida Y, Mine A, De Munck J, Van Landuyt KL. State of the
art of self-etch adhesives. Dent Mater. 2011;27(1):17-28.

13. Carrilho E, Cardoso M, Marques Ferreira M, Marto CM, Paula A, Coelho AS. 10-MDP Based
Dental Adhesives: Adhesive Interface Characterization and Adhesive Stability-A Systematic Review.
Materials (Basel). 2019;12(5).

14. Yoshihara K, Hayakawa S, Nagaoka N, Okihara T, Yoshida Y, Van Meerbeek B. Etching
Efficacy of Self-Etching Functional Monomers. J Dent Res. 2018;97(9):1010-6.

15. Awad MM, Albedaiwi L, Almahdy A, Khan R, Silikas N, Hatamleh MM, et al. Effect of
universal adhesives on microtensile bond strength to hybrid ceramic. BMC Oral Health. 2019;19(1):178.

16. Spitznagel FA, Vuck A, Gierthmuhlen PC, Blatz MB, Horvath SD. Adhesive Bonding to Hybrid
Materials: An Overview of Materials and Recommendations. Compend Contin Educ Dent.
2016;37(9):630-7.

76
17. Lung CY, Matinlinna JP. Aspects of silane coupling agents and surface conditioning in dentistry:
an overview. Dent Mater. 2012;28(5):467-77.
18. Fukegawa D, Hayakawa S, Yoshida Y, Suzuki K, Osaka A, Van Meerbeek B. Chemical
interaction of phosphoric acid ester with hydroxyapatite. J Dent Res. 2006;85(10):941-4.

19. Tekce N, Tuncer S, Demirci M. The effect of sandblasting duration on the bond durability of
dual-cure adhesive cement to CAD/CAM resin restoratives. J Adv Prosthodont. 2018;10(3):211-7.

20. Yoshihara K, Nagaoka N, Maruo Y, Nishigawa G, Irie M, Yoshida Y, et al. Sandblasting may
damage the surface of composite CAD-CAM blocks. Dent Mater. 2017;33(3):e124-e35.

21. Kassotakis EM, Stavridakis M, Bortolotto T, Ardu S, Krejci I. Evaluation of the Effect of
Different Surface Treatments on Luting CAD/CAM Composite Resin Overlay Workpieces. J Adhes
Dent. 2015;17(6):521-8.

22. ISO, 29022:2013. Dentistry-adhesion-notched-edge shear bond strength. Geneva: International
Organization for Standardization. 2013.

23. Borges GA, Sophr AM, de Goes MF, Sobrinho LC, Chan DC. Effect of etching and airborne
particle abrasion on the microstructure of different dental ceramics. J Prosthet Dent. 2003;89(5):479-88.

24. El-Damanhoury HM, N AE, Sheela S, Gaintantzopoulou MD. Adhesive luting to hybrid ceramic
and resin composite CAD/CAM Blocks:Er:YAG Laser versus chemical etching and micro-abrasion
pretreatment. J Prosthodont Res. 2020.

25. Gungor MB, Nemli SK, Bal BT, Unver S, Dogan A. Effect of surface treatments on shear bond
strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials. J Adv Prosthodont.
2016;8(4):259-66.

26. Lise DP, Van Ende A, De Munck J, Vieira L, Baratieri LN, Van Meerbeek B. Microtensile Bond
Strength of Composite Cement to Novel CAD/CAM Materials as a Function of Surface Treatment and
Aging. Oper Dent. 2017;42(1):73-81.

27. Kern M, Wegner SM. Bonding to zirconia ceramic: adhesion methods and their durability. Dent
Mater. 1998;14(1):64-71.

28. Versluis A, Tantbirojn D, Douglas WH. Why do shear bond tests pull out dentin? J Dent Res.
1997;76(6):1298-307.

29. Spitznagel FA, Horvath SD, Guess PC, Blatz MB. Resin bond to indirect composite and new
ceramic/polymer materials: a review of the literature. J Esthet Restor Dent. 2014;26(6):382-93.

30. Sismanoglu S, Gurcan AT, Yildirim-Bilmez Z, Turunc-Oguzman R, Gumustas B. Effect of
surface treatments and universal adhesive application on the microshear bond strength of CAD/CAM
materials. J Adv Prosthodont. 2020;12(1):22-32.

31. Higashi M, Matsumoto M, Kawaguchi A, Miura J, Minamino T, Kabetani T, et al. Bonding
effectiveness of self-adhesive and conventional-type adhesive resin cements to CAD/CAM resin blocks.
Part 1: Effects of sandblasting and silanization. Dent Mater J. 2016;35(1):21-8.

77
32. Loomans BA, Mesko ME, Moraes RR, Ruben J, Bronkhorst EM, Pereira-Cenci T, et al. Effect of
different surface treatment techniques on the repair strength of indirect composites. J Dent. 2017;59:18-
25.

33. Park JH, Choi YS. Microtensile bond strength and micromorphologic analysis of surface-treated
resin nanoceramics. J Adv Prosthodont. 2016;8(4):275-84.
34. Elsaka SE. Repair bond strength of resin composite to a novel CAD/CAM hybrid ceramic using
different repair systems. Dent Mater J. 2015;34(2):161-7.

35. Van Meerbeek B, Peumans M, Poitevin A, Mine A, Van Ende A, Neves A, et al. Relationship
between bond-strength tests and clinical outcomes. Dent Mater. 2010;26(2):e100-21.

36. Zhou J, Wurihan, Shibata Y, Tanaka R, Zhang Z, Zheng K, et al. Quantitative/qualitative analysis
of adhesive-dentin interface in the presence of 10-methacryloyloxydecyl dihydrogen phosphate. J Mech
Behav Biomed Mater. 2019;92:71-8.

37. Yoshida Y, Nagakane K, Fukuda R, Nakayama Y, Okazaki M, Shintani H, et al. Comparative
study on adhesive performance of functional monomers. J Dent Res. 2004;83(6):454-8.

38. Matinlinna JP, Lung CYK, Tsoi JKH. Silane adhesion mechanism in dental applications and
surface treatments: A review. Dent Mater. 2018;34(1):13-28.

39. Al Jabbari YS, Zinelis S, Eliades G. Effect of sandblasting conditions on alumina retention in
representative dental alloys. Dent Mater J. 2012;31(2):249-55.

40. Rawls HR. Dental Cement. In: Anusavice KJ, Phillips RW, Shen C, Rawls HR, editors. Phillips'
science of dental materials. 12th ed. St. Louis, Mo.: Elsevier/Saunders,; 2013. p. 307-39.

41. Rawls HR. Mechanical properties of dental materials. In: Anusavice KJ, Phillips RW, Shen C,
Rawls HR, editors. Phillips' science of dental materials. 12th ed. St. Louis, Mo.: Elsevier/Saunders,; 2013.
p. 48-68.

42. Ilie N. Spatial Distribution of the Micro-Mechanical Properties in High-Translucent CAD/CAM
Resin-Composite Blocks. Materials (Basel). 2020;13(15).

43. Ilie N. Altering of optical and mechanical properties in high-translucent CAD-CAM resin
composites during aging. J Dent. 2019;85:64-72.

44. Blumer L, Schmidli F, Weiger R, Fischer J. A systematic approach to standardize artificial aging
of resin composite cements. Dent Mater. 2015;31(7):855-63.

45. Swain MV. Impact of oral fluids on dental ceramics: what is the clinical relevance? Dent Mater.
2014;30(1):33-42.

46. Liebermann A, Ilie N, Roos M, Stawarczyk B. Effect of storage medium and aging duration on
mechanical properties of self-adhesive resin-based cements. J Appl Biomater Funct Mater.
2017;15(3):e206-e14.

47. Kitasako Y, Burrow MF, Nikaido T, Tagami J. The influence of storage solution on dentin bond
durability of resin cement. Dent Mater. 2000;16(1):1-6.

78
48. ISO, 11405:1994. Guidance on Testing of Adhesion to Tooth Structure. Geneva: International
Organization for Standardization. 1994.

49. Morresi AL, D'Amario M, Capogreco M, Gatto R, Marzo G, D'Arcangelo C, et al. Thermal
cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature
review. J Mech Behav Biomed Mater. 2014;29:295-308.

50. Gale MS, Darvell BW. Thermal cycling procedures for laboratory testing of dental restorations. J
Dent. 1999;27(2):89-99.
51. Deng D, Yang H, Guo J, Chen X, Zhang W, Huang C. Effects of different artificial ageing
methods on the degradation of adhesive-dentine interfaces. J Dent. 2014;42(12):1577-85.

52. Phark JH, Duarte S, Jr., Hernandez A, Blatz MB, Sadan A. In vitro shear bond strength of dual-
curing resin cements to two different high-strength ceramic materials with different surface texture. Acta
Odontol Scand. 2009;67(6):346-54.

53. DeHoff PH, Anusavice KJ, Wang Z. Three-dimensional finite element analysis of the shear bond
test. Dent Mater. 1995;11(2):126-31.

54. Van Noort R, Noroozi S, Howard IC, Cardew G. A critique of bond strength measurements. J
Dent. 1989;17(2):61-7.

55. Eckert GJ, Platt JA. A statistical evaluation of microtensile bond strength methodology for dental
adhesives. Dent Mater. 2007;23(3):385-91.

56. Stamatacos C, Simon JF. Cementation of indirect restorations: an overview of resin cements.
Compend Contin Educ Dent. 2013;34(1):42-4, 6.

57. De Munck J, Vargas M, Van Landuyt K, Hikita K, Lambrechts P, Van Meerbeek B. Bonding of
an auto-adhesive luting material to enamel and dentin. Dent Mater. 2004;20(10):963-71.

58. Duarte S, Jr., Botta AC, Meire M, Sadan A. Microtensile bond strengths and scanning electron
microscopic evaluation of self-adhesive and self-etch resin cements to intact and etched enamel. J
Prosthet Dent. 2008;100(3):203-10.

59. Papadopoulos K, Pahinis K, Saltidou K, Dionysopoulos D, Tsitrou E. Evaluation of the Surface
Characteristics of Dental CAD/CAM Materials after Different Surface Treatments. Materials (Basel).
2020;13(4).

60. Silva LHD, Lima E, Miranda RBP, Favero SS, Lohbauer U, Cesar PF. Dental ceramics: a review
of new materials and processing methods. Braz Oral Res. 2017;31(suppl 1):e58.

61. Eldafrawy M, Greimers L, Bekaert S, Gailly P, Lenaerts C, Nguyen JF, et al. Silane influence on
bonding to CAD-CAM composites: An interfacial fracture toughness study. Dent Mater.
2019;35(9):1279-90.

62. Eldafrawy M, Ebroin MG, Gailly PA, Nguyen JF, Sadoun MJ, Mainjot AK. Bonding to CAD-
CAM Composites: An Interfacial Fracture Toughness Approach. J Dent Res. 2018;97(1):60-7.

63. Duarte S, Phark JH, Blaltz MB, A S. Ceramic systems: An ultra- structural study. 2010;33:42-60.

79
64. Belli R, Wendler M, de Ligny D, Cicconi MR, Petschelt A, Peterlik H, et al. Chairside
CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization. Dent
Mater. 2017;33(1):84-98.

65. Van Meerbeek B, Mohrbacher H, Celis JP, Roos JR, Braem M, Lambrechts P, et al. Chemical
characterization of the resin-dentin interface by micro-Raman spectroscopy. J Dent Res.
1993;72(10):1423-8.

66. Chen Y, Lu Z, Qian M, Zhang H, Chen C, Xie H, et al. Chemical affinity of 10-
methacryloyloxydecyl dihydrogen phosphate to dental zirconia: Effects of molecular structure and
solvents. Dent Mater. 2017;33(12):e415-e27.
67. Wang Y, Spencer P. Quantifying adhesive penetration in adhesive/dentin interface using confocal
Raman microspectroscopy. J Biomed Mater Res. 2002;59(1):46-55.

68. van Dijken JW, Hasselrot L. A prospective 15-year evaluation of extensive dentin-enamel-
bonded pressed ceramic coverages. Dent Mater. 2010;26(9):929-39.

69. Siarampi E, Kontonasaki E, Andrikopoulos KS, Kantiranis N, Voyiatzis GA, Zorba T, et al.
Effect of in vitro aging on the flexural strength and probability to fracture of Y-TZP zirconia ceramics for
all-ceramic restorations. Dent Mater. 2014;30(12):e306-16.

70. Zhang Y, Wang Y. Effect of application mode on interfacial morphology and chemistry between
dentine and self-etch adhesives. J Dent. 2013;41(3):231-40.

71. Peumans M, Valjakova EB, De Munck J, Mishevska CB, Van Meerbeek B. Bonding
Effectiveness of Luting Composites to Different CAD/CAM Materials. J Adhes Dent. 2016;18(4):289-
302.

72. Manso AP, Carvalho RM. Dental Cements for Luting and Bonding Restorations: Self-Adhesive
Resin Cements. Dent Clin North Am. 2017;61(4):821-34.

73. Winter A, Schurig A, Rasche E, Rosner F, Kanus L, Schmitter M. The flexural strength of
CAD/CAM polymer crowns and the effect of artificial ageing on the fracture resistance of CAD/CAM
polymer and ceramic single crowns. J Mater Sci Mater Med. 2019;31(1):9.

74. Sonmez N, Gultekin P, Turp V, Akgungor G, Sen D, Mijiritsky E. Evaluation of five CAD/CAM
materials by microstructural characterization and mechanical tests: a comparative in vitro study. BMC
Oral Health. 2018;18(1):5.

75. Bourbia M, Finer Y. Biochemical Stability and Interactions of Dental Resin Composites and
Adhesives with Host and Bacteria in the Oral Cavity: A Review. J Can Dent Assoc. 2018;84:i1.

76. Wang Y, Spencer P. Physiochemical interactions at the interfaces between self-etch adhesive
systems and dentine. J Dent. 2004;32(7):567-79.

77. Oliveira B, Ubaldini A, Baesso ML, Andrade L, Lima SM, Giannini M, et al. Chemical
Interaction and Interface Analysis of Self-Etch Adhesives Containing 10-MDP and Methacrylamide With
the Dentin in Noncarious Cervical Lesions. Oper Dent. 2018;43(5):E253-E65.

Abstract (if available)

Abstract Chapter I: Influence of Surface Treatment on the Shear Bond Strength of Hybrid CAD/CAM Materials ❧ Objective: To establish a strong and durable bond, an appropriate treatment of the respective surfaces is crucial. Therefore, the aims of this study were: 1) To evaluate the influence of different surface treatments on the bonding strength between hybrid CAD/CAM materials and universal resin cement system using notched-edge shear bond strength (SBS) test. 2) To examine the microstructures of different hybrid materials and the surface changes after applying different surface treatments that contribute to the bonding performance of the restoration using scanning electron microscopy (SEM). ❧ Materials and Methods: CAD CAM blocks of three hybrid materials (LuxaCam Composite

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

The effect of surface treatment and translucency on the shear bond strength between resin cement and zirconia

PDF

Influence of enamel biomineralization on bonding to minimally invasive CAD/CAM restorations

PDF

Bond strength to different types of lithium disilicate reinforced ceramic materials

PDF

Influence of an aerosolized alumino-silica-based surface coating on shear bond strengths of two different types of zirconia

PDF

Micro tensile bonding strength to milled and printed permanent CAD/CAM materials

PDF

Influence of a novel self-etching primer on bond-strength to glass-ceramics and wettability of glass-ceramics

PDF

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.

PDF

The performance of light emitting diode (LED) light curing units and dental radiometers

PDF

Efficacy of a 10-MDP containing cleaner on the bond strength to contaminated dentin

PDF

Effect of staining solutions on the color and translucency change of various resin based definitive CAD/CAM materials

PDF

The influence of thickness and different resin cements on the flexural strength of high strength CAD/CAM glass ceramics

PDF

Effect of repeated firing on color and translucency of different CAD/CAM lithium disilicate reinforced glass-ceramic materials

PDF

Bonding accuracy of a novel lingual customized orthodontic appliance (INBRACE™): an in-vivo study

PDF

Trueness evaluation of three-dimensionally (3D) printed provisional crowns by two digital light processing (DLP) printers

PDF

Influence of particle-abrasion and aging on biaxial flexural-strength of three Zirconia materials

PDF

An evaluation of bond strength using sham lingual brackets with differences in base morphology and preparation

PDF

Evaluation of the printing trueness of CAD-CAM maxillary complete denture bases fabricated by using two different DLP 3D printers

PDF

3D ssessment of bracket position accuracy for lingual appliances using CAD/CAM technology: a pilot study

PDF

Effect of repeated firings on biaxial flexural strength of different CAD/CAM lithium disilicate reinforced materials in two different thicknesses

PDF

Comparison of premolar extraction rates between one-phase and two-phase class II malocclusion

Asset Metadata

Creator Alsamman, Reham Mohammed (author)

Core Title Adhesive performance of hybrid CAD/CAM materials. Chapter I, Influence of surface treatment on the shear bond strength of hybrid CAD/CAM materials. Chapter II, Luting protocol for novel CAD/CAM m...

School School of Dentistry

Degree Doctor of Philosophy

Degree Program Craniofacial Biology

Publication Date 04/29/2021

Defense Date 03/01/2021

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

Tag adhesion,bonding,CAD/CAM,hybrid ceramics,indirect restoration,OAI-PMH Harvest,resin cement,surface treatment

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Phark, Jin-Ho (committee chair), Duarte, Sillas Jr. (committee member), Knezevic, Alena (committee member), Paine, Michael (committee member)

Creator Email alsamman@usc.edu,Dr.reham.alsamman@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-455813

Unique identifier UC11668640

Identifier etd-AlsammanRe-9570.pdf (filename),usctheses-c89-455813 (legacy record id)

Legacy Identifier etd-AlsammanRe-9570.pdf

Dmrecord 455813

Document Type Dissertation

Rights Alsamman, Reham Mohammed

Type texts

Source 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 a...

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