University of Southern California Dissertations and Theses

Monitering of typodont root movement via crown superimposition of single CBCT and consecutive iTero scans

(USC Thesis Other)

Monitering of typodont root movement via crown superimposition of single CBCT and consecutive iTero scans

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content 1

Monitoring of Typodont Root Movement via Crown Superimposition of Single CBCT and
Consecutive iTero Scans

By: Philong Pham
A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Science in Craniofacial Biology
at
The University of Southern California
May 2014

2

Table of Contents

Abstract ......................................................................................................................................................... 3
Introduction .................................................................................................................................................. 4
Materials and Methods ................................................................................................................................. 6
Results ........................................................................................................................................................... 9
Discussion.................................................................................................................................................... 10
Conclusion ................................................................................................................................................... 13
Figures ......................................................................................................................................................... 14
Tables .......................................................................................................................................................... 22
References .................................................................................................................................................. 24

3

Abstract
Introduction: The purpose of this study was to develop a new methodology to visualize in 3
dimensions the whole teeth, including the roots, at any moment during orthodontic treatment
without the need for multiple cone-beam computed tomography (CBCT) scans. Methods: An
extra-oral typodont model was created using extracted human teeth placed in a wax base. These
teeth were arranged to represent a typical malocclusion. Initial records of the malocclusion,
including CBCT and intra-oral surface scan were taken. Threshold segmentation of the CBCT
was performed to generate a 3-dimensional virtual model. This model and the intra-oral surface
scan model were superimposed to generate a complete set of digital composite teeth composed of
high resolution surface scan crowns sutured to CBCT roots. These composite teeth were
individually isolated from their respective arches for single tooth manipulation. Orthodontic
treatment for the malocclusion typodont model was performed, and post-treatment intra-oral
surface scans before and after bracket removal were taken. A CBCT scan after bracket removal
was also obtained. The isolated composite teeth were individually superimposed onto the post-
treatment surface scan creating the expected root position setup. In order to validate this setup, it
was compared with the post-treatment CBCT scan which contains the true position of the roots.
Color displacement maps were generated to confirm accurate crown superimposition and to
measure the discrepancy between the expected and true root positions. Results: Color
displacement maps through crown superimposition showed differences between the expected
root positions and true root positions to be 0.1678mm ± 0.3178mm for the maxillary and
0.1140mm ± 0.1587mm for the mandibular in the presence of brackets. Once the brackets were
removed, differences of 0.1634mm ± 0.3204mm for the maxillary and 0.0902mm ± 0.2505mm
for the mandibular were found. Conclusions: A new reliable approach was demonstrated in an
ex-vivo typdont model to have the potential of tracking the 3-dimensional positions of the entire
teeth including the roots, with only the initial CBCT scan and consecutive iTero scans. Since the
presence of brackets in the intra-oral scan had minimal influence in the analysis, this method can
be applied to any stage of orthodontic treatment.

4

Introduction
In orthodontic treatment, various orthodontic appliances are utilized to move teeth from
malocclusion to a functional and stable occlusion which is composed of teeth in their proper
relationships to one another as well as in harmony with the maxillofacial hard and soft tissues.
The six characteristics or “keys” that describe tooth locations in 3-dimensional space and are
necessary to result in successful orthodontic treatment outcome were defined by Andrews in his
study of the crowns of 120 sets of stone models of nonorthodontic patients with ideal
occlusion.(Andrews, 1972, 1989) Andrews later developed the treatment goal concept in addition
to the initial preadjusted orthodontic appliances which contained built-in dimensional and
angular information for every tooth. These advancements resulted in a decreased amount of wire
bending necessary for successful orthodontic treatment.(Andrews, 1972, 1976, 1979, 1989)
Current preadjusted appliances are mostly derived from Andrews’ original straight-wire
appliances designed based on the crown norms he had measured. These preadjusted appliances
allows the orthodontist to treat patients with more efficiency and improves the quality of
orthodontic finishing.(Magness, 1978) However, due to inaccuracies in bracket positioning
during the initial bonding process and variations in tooth anatomy and bracket designs, Andrews’
6 keys are difficult to achieve for even experienced orthodontists.(Balut et al., 1992; Bryant et
al., 1984; Carlsson and Rönnerman, 1973; Germane et al., 1989; Kattner and Schneider, 1993;
Miethke, 1997; Miethke and Melsen, 1999; Taylor and Cook, 1992) Furthermore, because
Andrews focused solely on the crowns and not the entire tooth, root positions at the end of the
treatment may be compromised.(Balut et al., 1992; Miethke, 1997; Miethke and Melsen, 1999)
Thus, it is common to have improper root placement throughout orthodontic treatment resulting
in the need to visualize the roots frequently using radiographs in order to perform the necessary
corrections.
Traditionally, monitoring and finalizing the root position has been performed by using
panoramic X-rays at the initial, progress, and finishing stages of orthodontic treatment.(Mayoral,
1982; Ursi et al., 1990) A 2008 survey shows that 67.4% and 80.1% of American orthodontists
take progress and post-treatment panoramic radiographs respectively.(Keim et al., 2008)
However, multiple studies have indicated that panoramic X-rays do not accurately reflect the true
root position, especially in the canine and first premolars, due to distortions that occur mainly as
a result of the X-ray beam not being orthogonal to the target teeth.(Garcia-Figueroa et al., 2008;
5

Lagravère et al., 2008; Mckee et al., 2001; Owens and Johal, 2008) Therefore, a new method to
accurately visualize the root position at different stages in orthodontic treatment is needed.
In recent years, the development and use of cone-beam computed tomography (CBCT)
has allowed for accurate visualization of the roots of teeth in 3 dimensions.(Hutchinson, 2005;
Lagravère et al., 2008; Lascala et al., 2004) However, CBCT scans use significantly more
radiation than a panoramic radiograph, so multiple CBCT scans would not be suggested
clinically.(Brooks, 2009; Ludlow et al., 2006) An imaging technique that can be performed
multiple times throughout orthodontic treatment without any use of radiation is a digital intra-
oral surface scan. This technique can accurately display crowns with high resolution, but it
cannot display roots.(Ender and Mehl, 2011, 2013; van der Meer et al., 2012) While individually,
both CBCT and digital intra-oral surface scans do not have the capability to safely and accurately
visualize root positions at different stages of orthodontic treatment, root tracking may be possible
through a combination of these two imaging techniques. Therefore, the aim of this study was to
devise a new methodology that combines the pre-treatment CBCT scan with digital intra-oral
surface scans resulting in safe and accurate root position assessment in 3 dimensions throughout
orthodontic treatment.

6

Materials and Methods
An extra-oral “typodont” model composed of extracted human teeth with intact roots
arranged in ideal occlusion and placed in pink dental wax was created, and then these teeth were
rearranged in a typical malocclusion (Fig. 1A). Initial records including CBCT and direct intra-
oral surface scan were taken. The typodont was scanned with a Sirona Galileos Comfort 3D
scanner (Sirona, Charlotte, NC), set at 85kVp, 7mA, 14s scan time, 15cm spherical field of view
size, and 0.15mm voxel dimension. The typodont’s digital imaging and communications in
medicine (DICOM) data obtained from the CBCT scan was imported into Mimics (version 15.0;
Materialise, Leuven, Belgium). A threshold segmentation of 2224-4095 gray levels was applied
to the DICOM data resulting in the generation of 3-dimensional virtual surface models of the
maxillary and mandibular dental arches which contain the entire teeth including the roots (Fig.
2A). These two arches are imported into 3-matic (version 7.0; Materialise, Leuven, Belgium) in
which each tooth is individually isolated from its respective arch into its own whole tooth part
for single tooth manipulation (Fig. 2B).
An iTero intra-oral scanner (Align Technology, San Jose, CA) was used to digitally scan
the crowns of the typodont teeth resulting in stereolithography (.stl) files of the maxillary and
mandibular arches in high resolution (Fig. 2C). The .stl files of these arches were imported into
3-matic in which the crowns of the iTero arches were also individually isolated into their own
respective crown part for single crown manipulation (Fig. 2D). The CBCT isolated tooth parts
are then superimposed onto their respective iTero isolated crown parts (Fig. 2E). Since iTero
scans do not capture the roots, CBCT roots were removed before generating color displacement
maps using 3-matic to confirm accurate superimposition between the CBCT and iTero crowns.
Color maps showed the displacement between the closest points between two compared parts, in
this case the CBCT and iTero crowns. The CBCT and iTero crowns are composed of roughly
60,000 and 300,000 points respectively, and the color map generated showed the minimum
displacement between all of these points. In addition, 3-matic outputs the mean and maximum
displacements as well as the standard deviation measured in the color map analysis. 3-matic also
outputs a histogram that recorded all the displacements between the points. After validation of
accurate superimposition using a color map, the crowns of the low resolution CBCT isolated
7

teeth are removed, and the high resolution iTero crowns are sutured onto the CBCT roots
creating individual digital “composite teeth” (Fig. 2F).
Orthodontic treatment was simulated on this extra-oral typodont model by an experienced
orthodontist. A complete set of brackets was bonded and a .014” NiTi archwire was tied to these
brackets. The typodont was submerged into a hot water bath at 125F
0
temperature for 30
minutes. In hot water, the dental pink wax softens, allowing for accelerated tooth movement.
After expression of the archwire, the typodont was quenched in cold water for cessation of tooth
movement. This procedure was repeated using consecutive arch wires (.016” NiTi, .016” x .022”
NiTi and .016” x .022” SS) until treatment was complete (Fig. 1B). This simulated orthodontic
treatment was completed within hours in contrast to live orthodontic treatment which requires
many months to several years to finish.
Following orthodontic treatment, an intra-oral scan was taken before and after bracket
removal of the post-treatment typodont model, hence the bracketed and non-bracketed crowns. A
post-treatment CBCT was also taken after bracket removal for the purpose of validation. The
following methodology was separately performed on the bracketed and non-bracketed post-
treatment intra-oral scans in order to examine whether the presence of brackets affect the
accuracy of the analysis. Threshold segmentation of the post-treatment CBCT scan at 2224-4095
gray levels and .stl file from the intra-oral scans were obtained and imported into 3-matic. The
crowns of the isolated individual composite teeth created previously, were superimposed
independently onto the iTero digital scans of the post-treatment bracketed and non-bracketed
crowns. Since these composite teeth also contain the root information, this crown
superimposition results in the roots of the composite teeth placed in the “expected root position”
(ERP) setup (Fig. 3A). The post-treatment ERP setup was compared to the true root position
which was recorded through the post-treatment CBCT virtual model. This post-treatment CBCT
virtual model was also superimposed, but as one single unit, onto the post-treatment iTero
bracketed or non-bracketed crowns that the ERP model was currently superimposed with (Fig.
3B). After removal of the iTero scan, the ERP setup and post-treatment CBCT virtual model
have now been indirectly superimposed with each other, allowing the comparison between each
other (Fig. 3C).
Next, the composite teeth of the ERP setup and the CBCT virtual model teeth were cut at
the cementoenamel junction (CEJ) isolating the crowns and roots from each other. A color map
8

was created which measured the displacements between the isolated crowns of the ERP setup
and post-treatment CBCT virtual model in order to verify accurate superimposition between
them. A color map was also generated for the roots of the ERP and post-treatment CBCT virtual
model to measure the differences between the expected and true root positions.

9

Results
Color maps for the superimposition between the CBCT virtual model and iTero crowns
displayed three colors: green, blue, and red (Fig. 4). Changes within a 0.5mm range are shown as
green. Inward movement greater than 0.5 mm of the iTero crowns compared to the CBCT
crowns is represented as blue and outward movement greater than 0.5mm as red. The maxillary
and mandibular CBCT and iTero crowns were found to have a difference of 0.034mm ±
0.148mm and 0.004mm ± 0.147mm respectively. The maximal displacement between the CBCT
and iTero crowns for the maxillary and mandibular teeth was 0.824mm and 0.913mm
respectively (Table IA).
Color mapping from indirect superimposition of the ERP setup crowns with the post-
treatment CBCT crowns through iTero scanned bracketed crowns showed maxillary
displacement of 0.062mm ± 0.202mm with a maximum of 1.421mm and mandibular
displacement of 0.007mm ± 0.144mm with maximum of 1.185mm (Fig. 5, Table IB). Color
mapping of the roots showed maxillary displacement of 0.168mm ± 0.319mm with a maximum
of 1.859mm and mandibular displacement of 0.114mm ± 0.159mm with a maximum of
0.827mm (Fig. 6, Table IIA).
Color mapping from indirect superimposition of the ERP setup crowns with the post-
treatment CBCT crowns through iTero scanned non-bracketed crowns showed maxillary crown
displacement of 0.065mm ± 0.197mm with a maximum of 1.471mm, and mandibular crown
displacement of 0.006mm ± 0.135mm with a maximum of 0.874mm (Fig. 7, Table IC). Color
mapping of the roots showed maxillary displacement of 0.163mm ± 0.320mm with a maximum
of 1.976mm and mandibular displacement of 0.090mm ± 0.251mm with a maximum of
1.197mm (Fig. 8, Table IIB).

10

Discussion
Successful orthodontic treatment requires positioning of teeth in a stable and functional
occlusion as well as in an esthetic manner. The majority of the focus when performing
orthodontics is on the positions of the crowns of teeth rather than the roots due to the roots
usually not being involved with the esthetics and occlusal contacts.(Bryant et al., 1984; Carlsson
and Rönnerman, 1973; Dewel, 1949; Germane et al., 1989) Current research has shown that even
with proper placement of the roots following orthodontic treatment, some relapse is still to be
expected. Additionally, naturally occurring normal occlusion may not stay for life.(Driscoll-
Gilliland et al., 2001; Huggins, 1994; Little, 1990; Nett and Huang, 2005; Ormiston et al., 2005)
However, it is reasonable to speculate that the ideal positioning of the roots in the basal bone
could decrease the amount of relapse that occurs after orthodontic treatment. In addition, many
orthodontists notice flaws in the crown alignment only after observing improper root angulations
detected by X-rays although most X-rays are flawed. Furthermore, the American Board of
Orthodontics (ABO) recommends the use of panoramic X-rays when assessing the root
angulations, requires general root parallelism, and deducts points if the roots of adjacent teeth
come in contact with one another or are not parallel with each other.(Casko et al., 1998) Thus,
many orthodontists still attempt to obtain proper root placement when treating patients resulting
in pre-treatment, progress, and post-treatment panoramic radiographs taken. Multiple studies
have indicated that panoramic radiographs are not accurate representations of the root positions
and angulations, especially in canine and first premolars areas, so a new method for assessing the
roots is needed.(Garcia-Figueroa et al., 2008; Mckee et al., 2001; Owens and Johal, 2008)
For optimal assessment of the roots, a 3-dimensional representation of the teeth is
necessary. This has been made possible in recent years through CBCT technology which has
been shown to display dentofacial structures in a 1:1 ratio. In addition, any distortions in the
CBCT images have been found to be clinically insignificant.(Lagravère et al., 2008; Lascala et
al., 2004) Thus, CBCT scans accurately display the true positions of the roots. However, CBCT
scans transmit significantly more radiation compared to panoramic radiographs, so repeated
clinical use of CBCT scans is currently not suggested, especially for the children.(Brooks, 2009;
Ludlow et al., 2006; Silva et al., 2008) Thus, we developed a methodology to generate a 3-
dimensional representation of the whole teeth with minimal radiation through the combination of
the initial CBCT scan, for the root data, and intra-oral scans, for the crown data, to form digital
11

composite teeth that can be individually manipulated to create a model that can depict the root
positions at any stage of the orthodontic treatment.
Accurate individual tooth superimposition is paramount in the formation of a reliable
ERP setup, therefore we decided to use the intra-oral scan as the crowns of our composite teeth
for its high resolution. In addition, similar parts (intra-oral scan to intra-oral scan) superimpose
with each other more accurately than dissimilar parts (intra-oral scan to CBCT scan).
The composite teeth were created by superimposing CBCT crowns with iTero crowns,
and the accuracy of this CBCT and iTero crown superimposition was verified through a color
map analysis which found minimal differences between the two parts. While there were a few
blue and red spots on the color map indicating areas of displacement greater than 0.5mm, we
found that these spots was mainly localized on the occlusal surfaces which have much more
complex anatomy compared to the other tooth surfaces. Due to this complexity, the low
resolution of the CBCT scan could not accurately capture the occlusal surface anatomy. This
resulted in either missing or added tooth structure leading to some of the discrepancy between
the CBCT and iTero crowns. The tooth anatomy is also greatly dictated by the quality of the
threshold segmentation which could further add or subtract tooth structure causing these
discrepancies. In addition, during CBCT image acquisition there were artifacts that may have
further affected the contrast of the images. This could affect the discrimination between densities
during the threshold segmentation process, and, consequently, the construction of 3-dimensional
virtual models of teeth, especially, in the complex occlusal surfaces. All of these factors help
explain the small superimposition error shown in the color maps.
To validate the ERP root position against the true root position, only the ERP crowns,
and not the roots, were superimposed onto the CBCT virtual model roots. While crown
superimposition was manipulated to get the best fit, once achieved, the root displacement was
accepted and measured to check the validity of this methodology. Thus, we cut out the crowns
from the ERP and CBCT models and perform a color displacement map comparing solely the
roots to more accurately reflect the differences at the roots.
We tested our ERP setup against the CBCT virtual models of our ex-vivo typodont model
at post-treatment before and after bracket removal. Color maps from indirect superimposition of
ERP setup with the post-treatment CBCT virtual model showed there were little difference in the
amount of displacement in the crowns and in the roots whether bracketed or non-bracketed iTero
12

crowns were used in the construction of the ERP. Thus, the presence of brackets does not seem
to affect the accuracy of the ERP setup. Qualitatively, we did notice that in both cases there were
multiple red and blue locations within the roots indicating that there were locations with a
displacement of greater than 0.5, but upon closer analysis of the histograms, most of these points
were still within 1mm. Furthermore, all of the points are still within 2mm which is significantly
more accurate than panoramic radiographs. It is worth noting that our comparison showed true
three-dimensional discrepancies, unlike panoramic or any other two-dimensional X-rays which
will give false impressions of reduced discrepancies when a three-dimensional relationship is
projected onto a two-dimensional image.
Since the presence of brackets did not lower the accuracy of the ERP setup, we postulate
that this methodology may be performed at any phase of the orthodontic treatment to visualize
the root positions as long as the intra-oral surface scan is obtained at that stage. When performing
best-fit superimposition, 3-matic software was able to ignore the obvious addition of brackets.
Our methodology works similarly to how cranial base are often used as reference when
performing superimpositions because it remains unchanged when compared to what is being
analyzed.(Cevidanes et al., 2009, 2010, 2005, 2007) In this case the crown position in respect to
its own root, remains unchanged throughout orthodontic treatment. Thus, based on our results,
superimposition of the 3-dimensional crowns is an accurate way to capture the 3-dimensional
root information.
Additionally, we have reported the USC root vector analysis program which we have
been developing to measure the mesiodistal angulation and faciolingual inclination of each
whole tooth in three dimensions.(Tong et al., 2012a, 2012b) This root position assessment
methodology along with a modified USC root vector analysis program may provide a powerful
research tool to quantitatively measure the mesiodistal angulation and faciolingual inclination of
each whole teeth in three dimensions at any stage of orthodontic treatment.
A limitation of this study that should be considered is that it is yet to be tested on clinical
patients. We expect the threshold segmentation of teeth out of complex craniofacial bony
structures in real patients to be significantly more challenging. Threshold segmentation using
current software is tedious and very time-consuming. With newer generation 3D scanners and
further improvement in 3D rendering and image processing software, we hope to make the
process much easier and faster for clinical use in the future.
13

Conclusion

1. This methodology has been demonstrated in an ex-vivo typodont model to be a potential
option to track the 3-dimensional root position at any stage of orthodontic treatment, by
using a single pre-treatment CBCT scan and consecutive digital intra-oral scans. No
additional CBCT scans or panoramic radiographs are required.
2. This methodology is considered accurate and reliable through color displacement maps
which showed minimal differences between the expected and true root positions.

14

Figures

Fig 1. Malocclusion typodont models created using extracted human teeth and pink dental wax. A,
Before and B, after simulated orthodontic treatment.
15

Fig 2. Generation of digital composite teeth. A, Threshold segmentation of pre-treatment CBCT scan generates
a 3-dimensional virtual surface model. B, CBCT model is separated into individual teeth. C, Intra-oral digital scan
of pre-treatment. D, Digital intra-oral scan is separated into individual crowns. E, Crowns of the CBCT teeth are
superimposed onto the digital intra-oral scans crowns. F, CBCT roots and digital intra-oral scan crowns are
combined to generate individual digital composite teeth.
16

Fig 3. Indirect superimposition process with bracketed (top) and non-bracketed (bottom) post-treatment
intra-oral scans for the comparison of the expected and true root positions. A, Composite teeth were
superimposed onto the post-treatment intra-oral digital scan forming the expected root position setup. B,
Post treatment CBCT virtual model was also superimposed onto the same intra-oral digital scan. C,
Removal of the intra-oral digital scan allowed for comparison of the expected and true root positions.
17

Fig 4. Verification of accurate superimposition between pre-treatment CBCT virtual model and intra-oral digital
scan crowns A, Color map comparing superimposed pre-treatment CBCT virtual model and intra-oral scan
crowns. Green areas indicate that the two parts are within 0.5mm of each other while blue and red areas
indicate differences greater than 0.5mm. B, Histogram showing the distribution of displacements between the
CBCT and iTero crowns in the maxillary arch and C, in the mandibular arch. The blue and red lines indicate
0.5mm limits.
18

Fig 5. Verification of accurate crown superimposition after performing indirect superimposition with
post-treatment intra-oral scan with bracketed crowns A, Color displacement map comparing the
crown positions of the ERP and CBCT setups. Green areas indicate that the two parts are within
0.5mm of each other while blue and red areas indicate differences greater than 0.5mm. B, Histogram
showing the distribution of displacements between the crowns of the ERP and CBCT setups in the
maxillary arch and C, in the mandibular arch. The blue and red lines indicate 0.5mm limits.

19

Fig 6. Measurement of displacement between roots of the ERP setup and post-treatment CBCT
model after performing indirect superimposition with post-treatment intra-oral scan with bracketed
crowns A, Color displacement map comparing the root positions of the ERP and CBCT setups. Green
areas indicate that the two parts are within 0.5mm of each other while blue and red areas indicate
differences greater than 0.5mm. B, Histogram showing the distribution of displacements between
the roots of the ERP and CBCT setups in the maxillary arch and C, in the mandibular arch. The blue
and red lines indicate 0.5mm limits.

20

Fig 7. Verification of accurate crown superimposition after performing indirect superimposition with post-
treatment intra-oral scan with non-bracketed crowns A, Color displacement map comparing the crown positions of
the ERP and CBCT setups. Green areas indicate that the two parts are within 0.5mm of each other while blue and
red areas indicate differences greater than 0.5mm. B, Histogram showing the distribution of displacements
between the crowns of the ERP and CBCT setups in the maxillary arch and C, in the mandibular arch. The blue and
red lines indicate 0.5mm limits.

21

Fig 8. Measurement of displacement between roots of the ERP setup and post-treatment CBCT
model after performing indirect superimposition with post-treatment intra-oral scan with non-
bracketed crowns A, Color displacement map comparing the root positions of the ERP and CBCT
setups. Green areas indicate that the two parts are within 0.5mm of each other while blue and red
areas indicate differences greater than 0.5mm. B, Histogram showing the distribution of
displacements between the roots of the ERP and CBCT setups in the maxillary arch and C, in the
mandibular arch. The blue and red lines indicate 0.5mm limits.

22

Tables

Table I: Crown Analysis Verifying Accurate Superimposition
Crown Analysis Type Mean Displacement (mm) Standard Deviation (mm) Minimum Displacement (mm) Maximum Displacement (mm)

A. iTero vs. CBCT (Pre-Tx)

Mx Crowns 0.034 0.148 0.000 0.824
Mn Crowns 0.004 0.147 0.000 0.913

B. ERP setup vs. CBCT (Post-Tx w/Brackets)

Mx Crowns (with Brackets) 0.062 0.202 0.000 1.421
Mn Crowns (with Brackets) 0.007 0.144 0.000 1.185

C. ERP Setup vs. CBCT (Post-Tx w/o Brackets)

Mx Crowns (without Brackets) 0.065 0.197 0.000 1.471
Mn Crowns (without Brackets) 0.006 0.135 0.000 0.874
23

Table II: Root Analysis Comparing True Outcome versus Expected Root Position with and without Brackets

Root Analysis Type Mean Displacement (mm) Standard Deviation (mm) Minimum Displacement (mm) Maximum Displacement (mm)

A. ERP setup vs. CBCT (w/brackets)

Mx Roots 0.168 0.319 0.000 1.859
Mn Roots 0.114 0.159 0.000 0.827

B. ERP setup vs. CBCT (w/o brackets)

Mx Roots 0.163 0.320 0.000 1.976
Mn Roots 0.090 0.251 0.000 1.197
24

References
Andrews, L.F. (1972). The six keys to normal occlusion. Am. J. Orthod. 62, 296–309.
Andrews, L.F. (1976). The diagnostic system: occlusal analysis. Dent. Clin. North Am. 20, 671–
690.
Andrews, L.F. (1979). The straight-wire appliance. Br. J. Orthod. 6, 125–143.
Andrews, L.F. (1989). Straight wire: the concept and appliance (San Diego, California: K-W
Publications).
Balut, N., Klapper, L., Sandrik, J., and Bowman, D. (1992). Variations in bracket placement in
the preadjusted orthodontic appliance. Am. J. Orthod. Dentofacial Orthop. 102, 62–67.
Brooks, S.L. (2009). CBCT Dosimetry: Orthodontic Considerations. Semin. Orthod. 15, 14–18.
Bryant, R.M., Sadowsky, P.L., and Hazelrig, J.B. (1984). Variability in three morphologic
features of the permanent maxillary central incisor. Am. J. Orthod. 86, 25–32.
Carlsson, R., and Rönnerman, A. (1973). Crown-root angles of upper central incisors. Am. J.
Orthod. 64, 147–154.
Casko, J.S., Vaden, J.L., Kokich, V.G., Damone, J., James, R.D., Cangialosi, T.J., Riolo, M.L.,
Owens, S.E., and Bills, E.D. (1998). Objective grading system for dental casts and panoramic
radiographs. American Board of Orthodontics. Am. J. Orthod. Dentofacial Orthop. 114, 589–
599.
Cevidanes, L.H.C., Heymann, G., Cornelis, M. a, DeClerck, H.J., and Tulloch, J.F.C. (2009).
Superimposition of 3-dimensional cone-beam computed tomography models of growing patients.
Am. J. Orthod. Dentofacial Orthop. 136, 94–99.
Cevidanes, L.H.C., Motta, A., Proffit, W.R., Ackerman, J.L., and Styner, M. (2010). Cranial base
superimposition for 3-dimensional evaluation of soft-tissue changes. Am. J. Orthod. Dentofacial
Orthop. 137, S120–9.
Cevidanes, L.H.S., Bailey, L.J., Tucker, G.R., Styner, M.A., Mol, A., Phillips, C.L., Proffit,
W.R., and Turvey, T. (2005). Superimposition of 3D cone-beam CT models of orthognathic
surgery patients. Dentomaxillofac. Radiol. 34, 369–375.
Cevidanes, L.H.S., Bailey, L.J., Tucker, S.F., Styner, M. a, Mol, A., Phillips, C.L., Proffit, W.R.,
and Turvey, T. (2007). Three-dimensional cone-beam computed tomography for assessment of
mandibular changes after orthognathic surgery. Am. J. Orthod. Dentofacial Orthop. 131, 44–50.
25

Dewel, B.F. (1949). Clinical observations on the axial inclination of teeth. Am. J. Orthod. 35,
98–115.
Driscoll-Gilliland, J., Buschang, P.H., and Behrents, R.G. (2001). An evaluation of growth and
stability in untreated and treated subjects. Am. J. Orthod. Dentofacial Orthop. 120, 588–597.
Ender, A., and Mehl, A. (2011). Full arch scans: conventional versus digital impressions--an in-
vitro study. Int. J. Comput. Dent. 14, 11–21.
Ender, A., and Mehl, A. (2013). Influence of scanning strategies on the accuracy of digital
intraoral scanning systems. Int. J. Comput. Dent. 16, 11–21.
Garcia-Figueroa, M. a, Raboud, D.W., Lam, E.W., Heo, G., and Major, P.W. (2008). Effect of
buccolingual root angulation on the mesiodistal angulation shown on panoramic radiographs.
Am. J. Orthod. Dentofacial Orthop. 134, 93–99.
Germane, N., Bentley, B.E., and Isaacson, R.J. (1989). Three biologic variables modifying
faciolingual tooth angulation by straight-wire appliances. Am. J. Orthod. Dentofacial Orthop. 96,
312–319.
Huggins, D. (1994). The retention phase of treatment; the importance of root positioning as an
aid to stability of the occlusion. Aust. Orthod. J. 13, 100–105.
Hutchinson, S.Y. (2005). Cone beam computed tomography panoramic images vs. traditional
panoramic radiographs. Am. J. Orthod. Dentofac. Orthop. 128, 550.
Kattner, P.F., and Schneider, B.J. (1993). Comparison of Roth appliance and standard edgewise
appliance treatment results. Am. J. Orthod. Dentofacial Orthop. 103, 24–32.
Keim, R.G., Gottlieb, E.L., Nelson, A.H., and Vogels, D.S. (2008). 2008 JCO study of
orthodontic diagnosis and treatment procedures, part 1: results and trends. J. Clin. Orthod. 42,
625–640.
Lagravère, M.O., Carey, J., Toogood, R.W., and Major, P.W. (2008). Three-dimensional
accuracy of measurements made with software on cone-beam computed tomography images.
Am. J. Orthod. Dentofacial Orthop. 134, 112–116.
Lascala, C.A., Panella, J., and Marques, M.M. (2004). Analysis of the accuracy of linear
measurements obtained by cone beam computed tomography (CBCT-NewTom).
Dentomaxillofac. Radiol. 33, 291–294.
Little, R.M. (1990). Stability and relapse of dental arch alignment. Br. J. Orthod. 17, 235–241.
Ludlow, J.B., Davies-Ludlow, L.E., Brooks, S.L., and Howerton, W.B. (2006). Dosimetry of 3
CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT.
Dentomaxillofac. Radiol. 35, 219–226.
26

Magness, W.B. (1978). The straight-wire concept. Am. J. Orthod. 73, 541–550.
Mayoral, G. (1982). Treatment results with light wires studied by panoramic radiography. Am. J.
Orthod. 81, 489–497.
Mckee, I.W., Glover, K.E., Williamson, P.C., Lam, E.W., Heo, G., and Major, P.W. (2001). The
effect of vertical and horizontal head positioning in panoramic radiography on mesiodistal tooth
angulations. Angle Orthod. 71, 442–451.
Van der Meer, W.J., Andriessen, F.S., Wismeijer, D., and Ren, Y. (2012). Application of intra-
oral dental scanners in the digital workflow of implantology. PLoS One 7, e43312.
Miethke, R.R. (1997). Third order tooth movements with straight wire appliances. Influence of
vestibular tooth crown morphology in the vertical plane. J. Orofac. Orthop. 58, 186–197.
Miethke, R.R., and Melsen, B. (1999). Effect of variation in tooth morphology and bracket
position on first and third order correction with preadjusted appliances. Am. J. Orthod.
Dentofacial Orthop. 116, 329–335.
Nett, B.C., and Huang, G.J. (2005). Long-term posttreatment changes measured by the American
Board of Orthodontics objective grading system. Am. J. Orthod. Dentofacial Orthop. 127, 444–
50; quiz 516.
Ormiston, J.P., Huang, G.J., Little, R.M., Decker, J.D., and Seuk, G.D. (2005). Retrospective
analysis of long-term stable and unstable orthodontic treatment outcomes. Am. J. Orthod.
Dentofacial Orthop. 128, 568–74; quiz 669.
Owens, A.M., and Johal, A. (2008). Near-end of treatment panoramic radiograph in the
assessment of mesiodistal root angulation. Angle Orthod. 78, 475–481.
Silva, M.A.G., Wolf, U., Heinicke, F., Bumann, A., Visser, H., and Hirsch, E. (2008). Cone-
beam computed tomography for routine orthodontic treatment planning: a radiation dose
evaluation. Am. J. Orthod. Dentofacial Orthop. 133, 640.e1–5.
Taylor, N.G., and Cook, P.A. (1992). The reliability of positioning pre-adjusted brackets: an in
vitro study. Br. J. Orthod. 19, 25–34.
Tong, H., Kwon, D., Shi, J., Sakai, N., Enciso, R., and Sameshima, G.T. (2012a). Mesiodistal
angulation and faciolingual inclination of each whole tooth in 3-dimensional space in patients
with near-normal occlusion. Am. J. Orthod. Dentofacial Orthop. 141, 604–617.
Tong, H., Enciso, R., Van Elslande, D., Major, P.W., and Sameshima, G.T. (2012b). A new
method to measure mesiodistal angulation and faciolingual inclination of each whole tooth with
volumetric cone-beam computed tomography images. Am. J. Orthod. Dentofacial Orthop. 142,
133–143.
27

Ursi, W.J., Almeida, R.R., Tavano, O., and Henriques, J.F. (1990). Assessment of mesiodistal
axial inclination through panoramic radiography. J. Clin. Orthod. 24, 166–173.

Abstract (if available)

Abstract Introduction: The purpose of this study was to develop a new methodology to visualize in 3 dimensions the whole teeth, including the roots, at any moment during orthodontic treatment without the need for multiple cone‐beam computed tomography (CBCT) scans. Methods: An extra‐oral typodont model was created using extracted human teeth placed in a wax base. These teeth were arranged to represent a typical malocclusion. Initial records of the malocclusion, including CBCT and intra‐oral surface scan were taken. Threshold segmentation of the CBCT was performed to generate a 3‐dimensional virtual model. This model and the intra‐oral surface scan model were superimposed to generate a complete set of digital composite teeth composed of high resolution surface scan crowns sutured to CBCT roots. These composite teeth were individually isolated from their respective arches for single tooth manipulation. Orthodontic treatment for the malocclusion typodont model was performed, and post‐treatment intra‐oral surface scans before and after bracket removal were taken. A CBCT scan after bracket removal was also obtained. The isolated composite teeth were individually superimposed onto the post‐treatment surface scan creating the expected root position setup. In order to validate this setup, it was compared with the post‐treatment CBCT scan which contains the true position of the roots. Color displacement maps were generated to confirm accurate crown superimposition and to measure the discrepancy between the expected and true root positions. Results: Color displacement maps through crown superimposition showed differences between the expected root positions and true root positions to be 0.1678mm ± 0.3178mm for the maxillary and 0.1140mm ± 0.1587mm for the mandibular in the presence of brackets. Once the brackets were removed, differences of 0.1634mm ± 0.3204mm for the maxillary and 0.0902mm ± 0.2505mm for the mandibular were found. Conclusions: A new reliable approach was demonstrated in an ex‐vivo typodont model to have the potential of tracking the 3‐dimensional positions of the entire teeth including the roots, with only the initial CBCT scan and consecutive iTero scans. Since the presence of brackets in the intra‐oral scan had minimal influence in the analysis, this method can be applied to any stage of orthodontic treatment.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Three-dimensional assessment of tooth root shape and root movement after orthodontic treatment: a retrospective cone-beam computed tomography study

PDF

Utilizing voxel based superimposition to asses orthognathic surgical treatment

PDF

The mesiodistal angulation and faciolingual inclination of each whole tooth in three dimensional space post non-extraction orthodontic treatment

PDF

Alveolar process inclination as related to tooth inclination on near normal patients -- in three dimensional space

PDF

Root shape frequency and direction of dilaceration: a CBCT study

PDF

Orthodontic rotational relapse: prevalence and prevention

PDF

Shear bond strength comparison of mesh, sandblasted and laser-etched orthodontic brackets

PDF

Comparison of self-ligating brackets to conventionally-ligated twin edgewise brackets for root resorption

PDF

Comparison of HLD CAL-MOD scores obtained from digital versus plaster models

PDF

Relationship between dental and alveolar bony arch form and whole tooth mesiodistal angulation and faciolingual inclination in three-dimensional space

PDF

A comparative study of caucasian and African American mandibular clinical arch forms

PDF

Use of digital models to assess orthodontic treatment progress

PDF

Classification of 3D maxillary incisor root shape

PDF

3D assessment of virtual bracket removal for modern orthodontic retainers: a prospective clinical study

PDF

The accuracy of intraoral scans of interproximal spaces with and without saliva: a prospective clinical study

PDF

A comparison of root resorption between Invisalign treatment and contemporary orthodontic treatment

PDF

Cirtual 3D placement of temporary orthodontic anchorage implants

PDF

Relationship between key cephalometric parameters and tooth tip and torque

PDF

An assessment of orthognathic surgery outcomes utilizing virtual surgical planning and a patented full-coverage 3D-printed orthognathic splint

PDF

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

Asset Metadata

Creator Pham. Philong (author)

Core Title Monitering of typodont root movement via crown superimposition of single CBCT and consecutive iTero scans

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 03/05/2014

Defense Date 01/28/2014

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

Tag OAI-PMH Harvest,orthodontics,root,superimposition

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Paine, Michael L. (committee chair), Chen, Yong (committee member), Sameshima, Glenn T. (committee member)

Creator Email philonghpham@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-367556

Unique identifier UC11296310

Identifier etd-PhamPhilon-2281.pdf (filename),usctheses-c3-367556 (legacy record id)

Legacy Identifier etd-PhamPhilon-2281.pdf

Dmrecord 367556

Document Type Thesis

Format application/pdf (imt)

Rights Pham. Philong

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