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Root resorption of maxillary molar after intrusion by using TADs

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Root resorption of maxillary molar after intrusion by using TADs

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Content 1 | P a g e

Root Resorption
Of
Maxillary Molar
After Intrusion by using TADs
By
Jae Kim
May 2018

A Thesis Presented to the Faculty of the USC Graduate School
University of Southern California in Partial Fulfillment of the Requirements for the
Degrees Master of Science (Craniofacial Biology)

Copyright 2018 Jae Kim
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Acknowledgements
I would like to thank Dr. Glenn Sameshima for his mentorship through residency
and this master’s thesis. I would also like to thank Dr. Jong-ho Choi and Dr. Andre
Weissheimer for their guidance throughout this project. Patient data were generously
shared by Dr. Kook from GangNam St. Mary’s Hospital and Dr. Jong-ho Choi. I would
like to show my appreciation toward them for contributing their patient data. Lastly, I
would like to thank Allison Hwang, undergraduate student at USC, for her dedication in
assisting with data analysis.

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Table of Contents
I. Table of Contents 3
II. Abstract 5
III. Introduction 6
IV. Literature Review 8
▪ Cementum and External Apical Root Resorption (EARR) 8
▪ Pathogenesis 9
▪ Prevalence 11
▪ Grading of Root Resorption 12
▪ Effect of Orthodontic Forces 13
▪ Molar Intrusion/ TAD Assisted Molar Intrusion 14
▪ Other Factors Associated with EARR 15
▪ Predictability of EARR 16
▪ Quantitative Evaluation of Root Resorption 17
▪ 3-Dimensional Imaging and Software 19
V. Research Objective 22
VI. Hypothesis 22
VII. Materials and Method 23
▪ Subjects 23
▪ Data acquisition 23
▪ Procedure 24
▪ Superimposition of CBCT Scans before and after intrusion 26
VIII. Results & Discussion 29
▪ Pre-treatment Root Lengths and Post Intrusion Length 29
▪ Molar Intrusion and Root Resorption 29
▪ Extrusion of Data 30
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▪ Intrusion and Root Resorption 30
▪ Superimposition of CBCT Scans using Invivo 3D Analysis Software 33
▪ Inaccuracy/Sources of Error 40
▪ Possible Future Steps 42
IX. Conclusion 43
X. References 44
XI. Appendix 49
▪ Appendix A: OnDemand 3D Coordinates Raw Data 49
▪ Appendix B: OnDemand: Change in Root Length for each patient 61
▪ Appendix C: OnDemand Calculated Intrusion and Resorption amount on
each root 68

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II. Abstract
Introduction
Temporary anchorage devices (TADs) have transformed treatment planning in
orthodontics as they can provide alternative options to orthognathic surgeries; however,
there still are many aspects of TADs that need to be investigated to maximally utilize
them in safe and controlled manners. It has shown that when TADs are used to intrude
molars, root resorption can occur. The objective of our study was to determine the
amount of root resorption on maxillary molars after TAD intrusion and determine if the
amount of root resorption is correlated to the amount of intrusion.

Methods
TADs were used to intrude maxillary molars of 18 Korean patients between the
ages under 30 years old. Cone Beam Computed Tomography (CBCT) scans which had
been taken pre-treatment and post-intrusion were analyzed to assess root resorption.
The scans were superimposed (OnDemand Software and Invivo 3D Imaging software)
to assess the molars from which the following were measured in mm: (1) amount of
molar intrusion, (2) length of the mesial root of the molar before treatment, and (3)
length after treatment.

Results
Intrusion amount varied from 0 to 4mm and root resorption amount varied 0 to
3mm when measurements were made on the superimposition images. Teeth with
significant amount of intrusion did not undergo the most amount of root resorption and
teeth with the smallest amount of intrusion did not undergo the least amount of root
resorption. Furthermore, MB roots were not always the roots with the most significant
root resorption.

Conclusion
The amount of intrusion after TAD intrusion had no correlation to the amount of root
resorption on maxillary molars. Thus, this study suggests that when TADs are used to
intrude maxillary molars, root resorption may be unpredictable, but the amount may not
severe or significant.

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III. Introduction
Intrusion is a type of orthodontic tooth movement where a tooth is moved apically
parallel to the long axis of the tooth and into the supporting alveolar bone. This creates
pressure on the bone structure around the root of the tooth and cause bone resorption.
Intrusion may result in different outcomes depending on various factors including
magnitude and direction of the force, duration of the treatment, and intrusion methods.
There are two types of intrusions; true intrusion or absolute intrusion and relative
intrusion. True or absolute intrusion is pure apical movement of the tooth along the long
axis of the tooth without extrusion of other teeth. Relative intrusion is when teeth are
prevented from erupting or teeth are being labially tipped in the expense of extruding
other teeth in the arch.
In orthodontic treatment, molar intrusion is often crucial as it can change the
treatment plan. Molar intrusions have been attempted in numerous ways but are not
limited to bite plates, bite turbos, and biomechanical methods such as Begg,
Bioprogressive, Burstone intrusion arch, and Ricketts utility arch techniques. These
methods result in relative intrusion, which may not be desirable in achieving the optimal
treatment outcome in some cases. In the past, traditional methods of true intrusion
have been limited to bypass and segmental mechanics using fixed appliances or
wearing J-hook headgear. The success of traditional methods depends largely on
patients’ compliance, but compliance is often poor due to discomfort of the appliances.
Furthermore, it can still result in relative intrusion if the treating doctor is not careful with
the mechanics and compromise the treatment outcome.
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In recent years, temporary anchorage devices (TADs) have become an excellent
alternative for true intrusion. TADs are titanium alloy or stainless-steel screws with
diameter range from 1.2 to 2.5mm and length range from 6 to 11mm. They are typically
drilled into the attached alveolar mucosa located between roots of teeth only with local
anesthetics. Placement is considered non-invasive procedure with minimal
complications and pain. Furthermore, there is no osteointegration occurring with TADs,
which allows for ease of removal. TADs can eliminate the possibility of relative
intrusion and patient compliance factor of the methods discussed above. They can also
reduce patient discomfort level due to their small size. Not only they are convenient to
use, they have opened a new door to patients with complex conditions such as anterior
open bite and vertical excess problems; the only treatment option for these patients was
orthognathic surgery in the past. Now, these problems are being corrected non-
surgically using TADs.
TADs have transformed treatment planning in orthodontics as they are becoming
widely popular among orthodontists because of the reasons discussed above; however,
there still are many aspects of TADs that need to be investigated to maximally utilize
them in safe and controlled manners. It has shown that when TADs are used to intrude
molars, roots become resorbed. One of the potential side-effects that can occur with
any orthodontic intrusion is root resorption.

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IV. Literature Review
Cementum and External Apical Root Resorption (EARR)
There are two types of root resorption; external and internal root resorption.
Internal resorption is initiated by cells located in dental pulp causing resorption from the
inside of the pulp; whereas, external resorption is initiated in the periodontium causing
resorption on the external and lateral surfaces of the root. Both types of root resorption
are irreversible; thus, it may be detrimental to the long-term health of the tooth.
External root resorption is when the protective cementum layer, dentin, and/or
the surrounding bone are being lost due to physiological or pathological process. The
cementum has a protective layer called the formative cell layer that prevents osteoclasts
from resorbing the root. Once this layer is disrupted, resorption can be initiated. This
can physiologically occur when the permanent teeth resorb the root of deciduous teeth
as they erupt and exfoliate deciduous teeth. When teeth are endodontically or
periodontally infected, pathological resorption can occur. Pathological resorption can
also occur following any trauma and luxation to the tooth or after orthodontic tooth
movement. This may increase the risk of premature loss of the affected teeth if the
amount of resorption is severe.
The thickness of cementum layer varies along the root. Malek el at. extensively
studied the physical properties of root cementum on surfaces of premolar roots using a
Nano-indentation instrument. They suggested that its differential thickness dictates the
hardness of cementum (Figure 1). This can be used to predict the likely location for root
resorption.
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In orthodontic treatment, a type of external root resorption called external apical
root resorption (EARR) can occur. Apical root resorption occurs since cementum is the
softest at the apical part of the root (Figure 1).

Pathogenesis
The pathological process of EARR is thought to be initiated by compression from
orthodontic force which then causes ischemic necrosis of the periodontal ligament.
Normally, compression in the periodontal ligament causes hyalinization a few days after
the compression loading from the orthodontic force (Iino, 2007). During hyalinization,
macrophages are recruited to the compression site and remove hyaline. This allows for
tooth movements to occur. During this process, RANK (receptor activator of nuclear
factor kappa B) ligand (RANKL) and osteoprotegerin (OPG) are produced by bone
marrow stromal cells or found on the mature osteoblast. These two control factors are
responsible for the control of osteoclast differentiation (Figure 2). Excessive
compression can disrupt the natural balance of these factors initiating the process of
root resorption and damaging the protective cementum layer.
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Figure 2. (Fernandes el at. 2013)
This has been studied by many, yet it still needs much more research to fully
understand the exact process.
The etiology of The EARR associated with orthodontic treatment can vary
depending on multiple factors; these factors include individual biological variations such
as shape and length of the root, genetic predisposition and the effect of orthodontic
forces. The degree and severity of EARR depends on patient-related and treatment-
related factors.
Patient related factors include but not limited to genetics, systemic factors,
systemic diseases such as asthma, allergies, and chronic alcoholism, the severity of
malocclusion, tooth root morphology, a previous history of root resorption, alveolar bone
density, root proximity to cortical bone, endodontic treatment, and patient age and sex.
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Treatment related factors are the total treatment time, force related factors such as
magnitude, direction, continuity of force (continuous or intermittent), and duration of
applied force, type of orthodontic tooth movement (intrusion, extrusion, tipping, or bodily
movement), amount of displacement, and method of force application. Some believe
that age plays a role in possible root resorption. As patients age, their periodontal
ligament becomes largely quiescent (Lupi and Sadowsky, 1996). Adult patients also
have greater prevalence of periodontal disease than adolescents, increasing their risk of
root resorption (Segal el at., 2004). There have been reports that significant bone loss
in the teens and early twenties are infrequent (Reitan, 1954). These suggest that adult
patients are more susceptible to root resorption than adolescent patients when going
through orthodontic treatment.
As this multifactorial phenomenon can compromise the success of the
orthodontic treatment outcome, orthodontists must thoroughly understand the effect of
orthodontic treatment on root resorption. They should inform patients about every risk
factor and foresee any possible complication in advance.

Prevalence
As discussed above, the etiology of EARR can be complex and multifactorial.
The lack of current knowledge in this field cannot fully prepare orthodontists for all the
possible complications associated with EARR. It also causes the prevalence of EARR to
be higher than it should be. Various studies report large variations in the prevalence of
EARR associated with orthodontic treatment. For instance, CPR Maues et al. reported
that only 2.9% of 959 teeth from 129 patients presented severe root resorption [8];
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whereas, MS Marques et al. found that 14.5% of 1049 patients had severe root
resorption during orthodontic treatment. [9]

Grading of Root Resorption
There are various methods in determining the amount of root resorption.
Balducci et al. used a system where the 2mm or greater root resorption is described as
severe [10]; whereas, Mirabella et al. defined severe EARR as more than 4mm or one
third of the root length being resorbed [11]. Thus, variations in the prevalence found by
different groups are expected since different grading systems can change the result of a
study.
A grading classification developed by Levander and Malmgren has been used in
numerous studies to assess the severity of root resorption (Figure 3).
Figure 3 Levander and Malmgren’s classification for quantitative assessment of root
resorption. 1. Grade 1, 2. Grade 2, 3. Grade 3, 4. Grade4. (Levander and Malmgren
1988)
Table 1 describes each grade in Levander-Malmgren classification; grade 4 is
defined as root resorption exceeds 1/3 of original root length. This has been the
consensus for severe root resorption in the orthodontic literature.
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Table 1 (Levander and Malmgren, 1988)

Effect of Orthodontic Forces
One of the major risk factors for EARR is the magnitude, direction, type of
orthodontic force. It has been widely accepted that the heavy forces not only cause
slower tooth movement, but also can cause more root resorption than light forces (Chan
and Darendeliler 2005). Optimal force for orthodontic treatment without risk of root
resorption should be 7-26 g/cm
2
(Chan and Darendelier 2005).
Any directional force or type of force can cause some form of root resorption.
Most frequent root resorption has been associated with orthodontic intrusion (Brezniak
and Wasserstein 1993). Intrusion also tends to have four times root resorption risk than
extrusion (Han et al, 2005). Han el at. showed that premolars underwent more EARR
when intruded compared when extruded using 17x25ss utility arch (Han el at., 2005).
Intrusion is thought to cause most detrimental root resorption in orthodontic treatment
when coupled with lingual root torque (Costopoulos and Nanda 1996).
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The amount of EARR also depends on the type of orthodontic force. When teeth
are being intruded into the alveolar bone, continuous light forces tend to have less risk
of root resorption than intermittent heavy forces as shown below in Figure 4.

Figure 4 (Darendeliler 2009)

Molar Intrusion/ TAD Assisted Molar Intrusion
Molars have the second highest risk of root resorption after incisors (Sharpe el at.
1987). When molars are being intruded into the supporting alveolar bone, the pressure
concentrates at the root apex. This causes compression and necrosis of periodontal
ligament. TADs for molar intrusion are typically placed between roots of molars or
between roots of 1
st
molar and 2
nd
premolar as shown in Figure 5.
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Figure 5 (Li et al., 2013) A. Mini-screw between the upper first molar and the second
molar on the buccal side., B. Mini-screw placed on the lingual side.
There have been many studies on the effect of molar intrusion on roots when
TADs are used. Ohmae et al. has shown that an intrusive force (150g) via TADs and
NiTi-coil spring caused minimal root resorption when teeth were intruded 4.5mm.
Histology revealed that short period of continuous heavy force caused root resorption
and, subsequently, the formation of new cementum (Ohmae et al., 2001). Another
group has shown that super-erupted molars can be intruded up to 2.1mm without
significant root resorption (Heravi et al., 2011)

Other Factors Associated with EARR
As mentioned above, there are various other factors that increase the risk of
EARR. The duration of the overall treatment as well as duration of active force on teeth
can increase root resorption likelihood. (Segal et al. 2004) Furthermore, the amount of
apical displacement especially during intrusion is highly related to amount of total EARR.
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Patients with tongue thrusting can also increase the risk of EARR (Sameshima
and Sinclair, 2001). One of possible etiologies for malocclusions with open anterior bite
is tongue thrusting. A treatment option for these patients may involve molar intrusion to
close the bite. Thus, patients with open bites are highly susceptible to EARR not only
because of their initial condition, but also because of possible treatment method.

Predictability of EARR
There have been many studies focusing on the predictability of EARR associated
with orthodontic treatment. Sameshima and Sinclair concluded in their study that
patients with horizontal root displacement during the treatment, tongue thrusting habit,
and abnormal root shape may have higher estimated risk of EARR (Sameshima and
Sinclair 2004).
Orthodontists attempt to predict possible EARR in patients by assessing risk
factors associated with orthodontic treatment; however, there still are many unknown
risk factors that need to be discovered before accurate prediction of possible future
resorption can be made (Shah 2017).

Quantitative Evaluation of Root Resorption
It is evident that histological evaluation of root resorption is the most accurate
method (Harry and Sim, 1982) (Kokich, 2008). Unfortunately, this cannot be done on
healthy adults going through orthodontic treatment. Radiological evaluation has been
the most routine method of determining the probability of EARR.
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Panoramic and periapical radiographies have been the most common method to
diagnose and predict the susceptibility of EARR in orthodontic patients. The amount of
EARR can be calculated on periapical radiographs by measuring the tooth length
(incisal-apical distance) and the crown length (incisal-cementoenamel junction distance)
of the tooth (Figure 5). This method ensures for correct radiograph inclination since the
crown length needs to be the same before and after the treatment.
Figure 5. (Scheibel el at., 2014) A.
Incisal-apical distance., B. Incisal-Cementoenamel junction distance.
The method using panoramic radiograph uses similar way of measuring EARR
(Figure 6). However, this method does not consider the differences in angulation of the
teeth before and after the orthodontic treatment. Sameshima and Sinclair suggest that
periapical films should be ordered for obscured apices and/or other risk factors of EARR
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since panoramic radiography may overestimate the amount of root resorption by 20% or
more (Sameshima and Sinclair, 2001)

Figure 6. (Ioi el at. 2015)

The questionable accuracy of panoramic radiography method has been shown in the
past (Kokich 2008). Kokich found that radiological incidence of root resorption in
bicuspid intrusion was lower than histological incidence (Kokich 2008).
Recently, using cone beam computed tomography (CBCT) to assess EARR has
been becoming popular since studies have shown that CBCT is more accurate than
panoramic radiograph. Dudic et al. has shown that EARR is being underestimated with
panoramic radiography when compared to CBCT. More than 25% of the root resorption
was observed with CBCT than with panoramic radiography (Dudic et al. 2009).
Periapical radiography has been shown to be more accurate than CBCT when
evaluating apical root resorption on posterior teeth (Freitas el at., 2013). However,
periapical radiographic method is very technique sensitive since angulation between the
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teeth and the x-ray beam need to be identical to be accurate. Thus, there needs to be a
more accurate way of measuring root resorption using CBCT.

3-Dimensional Imaging and Software
Cone Beam Computed Tomography has been slowly replacing the conventional
radiographic methods in orthodontics. With the rapid development of technologies, new
CBCT scanners produce higher resolution images with low radiation being exposed to
patients (Hashimoto, 2003).
There is numerous 3-Dimensional Imaging software that are available in market
for medical and dental professionals. They are also becoming more accurate and user-
friendly. Thus, many orthodontists now turn to CBCT and 3D imaging to diagnose and
treatment plan cases. There have been reports that EARR can accurately be measured
using these new technologies.
Some examples of software that have been used include, but not limited to
Dolphin 3D Imaging, Invivo Imaging, ITK-SNAP, MIMICS, and OnDemand. Leite el at.
compared root resorption between self-ligating and conventional pre-adjusted brackets
using CBCT and Dolphin 3-D imaging (Leite el at., 2012). They reported that there was
no difference in the degree of EARR between self-ligating brackets and conventional
preadjusted brackets (Leite el at., 2012). Recently, volumetric measurement of molar
roots was done using CBCT and laser scanning after mini screw implant intrusion (Li et.,
2013). Using the Mimics software 10.0, CBCT DICOM files were imported and
segmented (Figure 7). The roots of the molar were then isolated and their volumes
before and after the intrusion were compared using the software (Figure 8). The
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volumetric measurements were verified to be accurate by physically measuring the
volume using the laser scanning. Although the authors suggest that this is an accurate
method, there remain uncertainties in the segmentation process.

Figure 7. Segmentation of the upper first molar. (Li et al., 2013)
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Figure 8. Isolation of roots (Li et al., 2013)

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V. Research Objective
The primary purpose of this retrospective study was to evaluate the following
questions:
1. Is there a more convenient three-dimensional imaging technique for
quantitatively measuring molar intrusion and molar root resorption?
2. Can this three-dimensional imaging technique be used to accurately measure?
a. The amount of intrusion on molars
b. The amount of resorption on roots of intruded molars?
3. Can there be correlation between amount of root resorption and amount of
intrusion?

VI. Hypothesis
In view of the literature, we hypothesized that the amount of intrusion by using
TADs has no significant correlation to the amount of root resorption on maxillary molars.

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VII. Materials and Methods
Subjects
Eighteen Korean patients who had undergone orthodontic treatment involving
molar intrusion by using TADs were selected from the Orthodontic Department,
GangNam St. Mary’s Hospital-The Catholic University of Korea and Dr. Jeong-ho Choi’s
private clinic in Seoul, Korea.
Patients were between the ages of 20 and 30 years. There was no restriction on
type of malocclusion, sex, crowding, or other common dental and orthodontic
measurements. Patients with previous orthodontic treatment, evidence of root
resorption on pre-treatment panoramic radiographs, and severely dilacerated roots are
excluded from the study.
Pre-treatment CBCT and post-intrusion CBCT were taken for each patient. It
should be noted that post-intrusion CBCT for patients were taken at different period in
the treatment.
Data acquisition
For patients from the Orthodontic Department, GangNam St. Mary’s Hospital-The
Catholic University of Korea, CBCT scans were taken using an iCAT scanner by the x-
ray technologist. The scanning parameters were 120 kV, 47.7 mAs, 20 seconds per
revolution, 170 x 130 mm field of view, and voxel size of 0.3 mm. Each seated subject's
head position was oriented so that the Frankfort plane was parallel to the floor, and the
images were taken at the intercuspal position.
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For patients from Dr. Jeong-ho Choi’s private clinic in Seoul, Korea, CBCT scans
were taken using KaVo 3D eXam scanner by his x-ray technologist. The scanning
parameters were 120 kV, 8 mAs, 26 seconds per revolution, 80 x 80mm field of view,
and voxel size of 0.2 mm. Each seated subject's head position was oriented so that the
Frankfort plane was parallel to the floor, and the images were taken at the intercuspal
position. The field of view for all CBCT scans included anterior cranial base, nasion,
facial bones, maxilla, and mandible.
Procedure
All the CBCT data were exported and saved as DICOM multi-files format. They
were then imported into OnDemand 3D
TM
Application software (CyberMed Tustin, Calif)
for analysis of molar intrusion and root resorption using its 3-dimensional coordinate
system.
The software allows CBCT pre-treatment and post-intrusion scans to be re-
oriented and calibrated to the same head position by using following landmarks; Nasion,
Sella, right Pogonion (R Po), left and right orbitale (R or and L or) (Figure 9).
The following landmarks were digitized for measuring the lengths of the roots and
displacements of teeth during the treatment; midpoint on the cementoenamel junction of
maxillary 1
st
molar on the mesial surface (CEJ), apex of the palatal root of maxillary 1
st

molar (Palatal Root), apex of the mesiobuccal root of maxillary 1
st
molar (MB root), and
apex of distobuccal root (DB root). All the point digitizations were done by 1 examiner
to limit operator generated variation.
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Figure 9. Reorientation of CBCT Scan Using OnDemand 3D
TM

Both right and left maxillary 1
st
molars were evaluated for each patient. Coordinates for
the above landmarks were transferred to Excel software for further analysis (Table 2).

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Table 2: Coordinates (x, y, z) of Landmarks for Pre-treatment (X1, Y1, Z1) and Post-
intrusion (X2, Y2, Z2) CBCT Scans of Patient NY

Superimposition of CBCT Scans before and after intrusion.
The same DICOM multi-files were imported into Invivo 3D cephalometric analysis
software (version 5.3; Anatomage, San Jose, Calif) for superimposition of pre-treatment
CBCT scan and post-intrusion CBCT scan. This was used to assess the maxillary 1
st

molar from which the followings were measured in mm: (1) amount of molar intrusion, (2)
length of the mesial root of the molar before treatment, and (3) length after treatment.
Pre- and post-treatment mesial root lengths were compared.
Patient NY
X1 (mm) Y1 (mm) Z1 (mm) X2 (mm) Y2 (mm) Z2 (mm)
Nasion 0 0 0 0 0 0
Sella 0.5 64.4 -16.96 0.5 64.33 -16.24
R Po -66.16 88.24 -29.97 -64.84 89.41 -29.18
R or -30.92 8.56 -29.97 -30.17 8.76 -29.18
L or 30.1 8.56 -29.97 31.25 8.76 -29.18
MB root R 26.01 17.39 -61.84 26.46 17.16 -61.38
DB root R 28.36 22.91 -62.44 28.47 23.02 -61.69
Palatal root R 17.47 24.62 -60.22 16.69 24.77 -58.75
CEJ R 23.54 16.08 -72.81 24.16 16.44 -71.95
MB root L -25.55 16.72 -64.28 -26.08 16.75 -63.68
DB root L -27.04 18.85 -63.42 -27.34 19.65 -62.54
Palatal root L -16.16 22.48 -61.92 -16.38 22.74 -60.99
CEJ L -24.46 14.59 -75.16 -23.74 15.22 -75.1
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To determine the amount of intrusion, two images were superimposed based on
anterior cranial base since it is the most stable landmark. Images were then sagittally
sliced on the 1
st
maxillary molars as shown below. The amount of intrusion was
calculated by measuring from the tip of molar before to after the intrusion.

Figure 10. Superimposition of Pre-treatment and Post-Intrusion CBCT Scans

These scans were superimposed based on the crown of 1
st
maxillary molar
before and after the intrusion to calculate the amount of EARR associated with the
treatment. Superimposed images were then sagittally sliced on the 1
st
maxillary molar
that was intruded. This allowed the observer to locate the apex of each root and directly
compared the height of the molar roots before and after the intrusion.
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Figure 11. Pre-treatment measurements of 1
st
maxillary molar roots after re-orientation
of CBCT scans based on 1
st
maxillary molar. Before Intrusion

Figure 12. Post-intrusion measurements of 1
st
maxillary molar roots after re-orientation
of CBCT scans based on 1
st
maxillary molar.
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VIII. Results and Discussion
Pre-treatment Root Lengths and Post-Intrusion Root Length
Right and left 1
st
maxillary molars from fourteen patients (total of twenty-eight
molars) were examined. The lengths (L) of each molar root before and after the
intrusion were determined by calculating the difference between CEJ point and the apex
of each root. This was repeated for both right and left molars. Table 3 shows a sample
calculation for patient SY.
Patient SY L1 (mm) L2(mm)
MB root R 1.38 0.43
DB root R 2.56 3.47
Palatal root R 2.95 3.61

MB root L 8.85 1.44
DB root L 11.8 1.59
Palatal root L 4.13 2.46
Table 3: Root Lengths before and after the intrusion for Patient SY. L1: Pre-treatment
Length. L2: Post-intrusion Length

Molar Intrusion and Root Resorption
The amount of root resorption was then calculated by subtracting the pre-
treatment length of each root from the post-intrusion root length (L1-L2). The amount of
intrusion for maxillary 1
st
molar was determined by calculating the difference between
CEJ point on pre-treatment scan (CEJ1) and CEJ point on post-intrusion scan (CEJ2).
Table 4 shows a sample calculated values of intrusion and resorption for patient NY.
Table 4: Intrusion and Root Resorption of all three roots for Patient NY

Intrusion (mm) Resorption MB (mm) Resorption DB (mm) Resorption P (mm)
NY R 0.29 0.59 0.25 0.21
NY L 0.83 0.6 -0.17 0.37
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Exclusion of Data
There may be sources of data in data acquisition process. Some teeth have
values that do not seem to be physiologically feasible. Table 5 is an example of
inaccurate data. This shows that right maxillary 1
st
molar for patient GS was extruded
9.49mm and its root lengths increased. Such data are excluded from the analysis. The
sources of inaccuracy and outliers are discussed later in this paper.
Intrusion (mm) Resorption MB (mm) Resorption DB (mm) Resorption P (mm)
GS R -9.49 -0.82 -1.05 -1.94
GS L 0.09 -0.11 0.2 -0.02
Table 5: Intrusion and Root Resorption of all three root for Patient GS.

Intrusion and Root Resorption
Twelve out of twenty-eight teeth were excluded. Table 6 is the summary of
sixteen teeth that were included in the analysis.
Intrusion (mm) Resorption MB (mm) Resorption DB (mm) Resorption P (mm)
SY R 4.29 0.95 -0.91 -0.66
SY L 5.54 7.41 10.21 1.67
NY R 0.29 0.59 0.25 0.21
NY L 0.83 0.6 -0.17 0.37
YS1 R 2.48 0.36 1.12 1.37
YS1 L 2.38 0.24 0.73 0.28
KD R 3.27 -1.29 1.92 1.99
KD L 3.03 1.65 1.72 0.63
YS2 R 4.14 0.57 1.57 1.44
YS2 L 3.66 -0.53 1.22 1.31
JS R 0.62 -0.23 0.9 1.91
JS L 1.7 -2.23 3.74 2.43
PM R 0.7 0.27 0.68 -0.33
PM L 0.17 -0.87 -0.79 -0.51
SE R 0.98 0.33 0.46 0.17
SE L 0.54 -0.26 -0.24 -0.78
Table 6: Intrusion and Root Resorption of all three roots for sixteen molars.
31 | P a g e

Negative numbers in table 6 suggest teeth had negative resorption, meaning
deposition or elongation. This is very unlikely to occur and may be due to measurement
error which will be discussed later.
Patient SY had the most amount of molar intrusion; left molar had 5.54mm.
Throughout the treatment, left molar roots suffered tremendous amount of resorption
according to the calculation; MB root resorption was 7.41mm and DB root resorption
was 10.21mm. It is uncertain that this was due to inaccuracy or an outlier since CBCT
scans were not taken immediately before and after the intrusion. There could have
been other factors throughout the treatment that caused this amount of root resorption.
Teeth other than left molar of Patient SY had intrusion that ranged from 0.29 to
4.29mm. Root resorption varied between right and left molars of the same patient. For
instance, right and left molars of patient YS1 had 2.48mm and 2.38mm of intrusion,
respectively; however, root resorption on these teeth varied. Given that same intrusive
forces are applied to the right and left molars, it is expected to see similar amount of
resorption on each root. Yet, right and left palatal roots had resorption of 1.37mm and
0.28mm, respectively.
Recent study by Li el at. claimed that mesiobuccal root of maxillary 1
st
molar is
most susceptible to EARR when it is intruded (Li el at., 2013). Only three teeth out of
sixteen teeth agreed with their conclusion. This may be due to inadequate sample size
or sources of error.
There were also large variations among the roots of the same tooth. The MB,
DB, P root of right molar for patient YS1 had 0.36mm, 1.12mm, 1.37mm of root
resorption, respectively.
32 | P a g e

It should be noted that this was a retrospective study and there were many
factors that could not be controlled. Nevertheless, variations were too large; variations
imply that there was no correlation between the amount of intrusion and EARR. Yet,
besides teeth of patient SY, none of the teeth had more root resorption than 4mm
(Graph1). As described in the literature review section, 4mm is the accepted amount of
severe resorption in the orthodontic community. Thus, this study suggests that when
TADs are used to intrude maxillary molars, root resorption may be unpredictable, but
the amount may not severe or significant.

Graph 1: EARR vs Intrusion by using TADs

-4
-2
0
2
4
6
8
10
12
0 1 2 3 4 5 6
Resorption (mm)
Intrusion (mm)
Intrusion vs. EARR
P
DB
MB
33 | P a g e

Superimposition of CBCT Scans using Invivo 3D Analysis Software
Only ten out of eighteen teeth showed intrusion and root resorption when pre-
treatment and post-intrusion images were superimposed. Table 7 displays all ten teeth
with their intrusion and root resorption values. For these, only MB roots were analyzed
since they were claimed to be most susceptible to EARR associated with orthodontic
treatment.
Patient
Intrusion
(mm)
Root resorption MB
(mm)
SY R 3.83 2.98
SY L 1 0.7
YS1 R 1.7 1.2
YS1 L 4 2.31
KD R 2.16 0.9
KD L 1.72 1.4
JS R 1.75 0.45
JS L 2.76 1.74
SE R 1.75 1.08
SE L 2.29 1.42

Table 7: Measured Intrusion and Root resorption values using Invivo 3D software.
Intrusion amount varied from 1 to 4mm when measurements were made on the
superimposition images. Left 1
st
maxillary molar of patient YS1 had the most root
resorption (4mm) (Figure 13). However, it did not have the most root resorption
(2.31mm). SY L had the least amount of intrusion (1mm) but did not have the least
amount of root resorption (0.7mm).
34 | P a g e

Figure 13. Superimposition of patient YS1 left 1
st
Maxillary Molar.

Figure 14a: Superimposition of patient JS right 1
st
Maxillary Molar.

35 | P a g e

Figure 14b: Pre-treatment lengths for MB and DB roots of JS right 1
st
Maxillary Molar.

Figure 14c: Post-intrusion lengths for MB and DB roots of JS right 1
st
Maxillary Molar.

36 | P a g e

Figure 14d: Pre-treatment length for Palatal root of JS right 1
st
Maxillary Molar.

Figure 14e: Post-Intrusion length for palatal root of JS right 1
st
Maxillary Molar.

37 | P a g e

The amount of EARR on MB, DB, palatal roots of patient JS’s right maxillary 1
st

molar were 0.46mm, 0.31mm, and 0.45mm, respectively (Figure 14). These were the
least amount of EARR in the sample; yet, the amount of intrusion was not the least.
The amount of intrusion was 1.75mm (Table 7).
Right maxillary 1
st
molar of patient SY had the most resorption when the tooth
was intruded 3.83mm (Figure 15). EARR amount observed on MB, DB, and palatal
roots were 2.98mm, 3.96mm, 3.79mm, respectively. This again contradicts the study by
Li el at. that stated MB roots of 1
st
molars had the most risk of EARR when intruded.
These results also suggest that the amount of intrusion is not correlated with the
amount of EARR. This supports that EARR is unpredictable when intruding molars with
the use of TADs.

Figure 15a: Superimposition of patient SY right 1
st
Maxillary Molar.

38 | P a g e

Figure 15b: MB and DB Root Lengths of patient SY right 1
st
Maxillary Molar

Figure 15c: MB and DB Root Lengths of patient SY right 1
st
Maxillary Molar

39 | P a g e

Figure 15d: Palatal Root Lengths of patient SY right 1
st
Maxillary Molar

Figure 15e: MB and DB Root Lengths of patient SY right 1
st
Maxillary Molar
40 | P a g e

Inaccuracy/Sources of Error
Sources of error are difficult to avoid in retrospective studies. The evaluation
method of this study includes possible sources of inaccuracy and error. As discussed
briefly above, the biggest possible inaccuracy may be the fact that scans were not taken
immediately before and after the intrusion. Any type of orthodontic movement could
have result in root resorption. Different types of movements could have occurred in
each patient, causing inaccuracy in the results. Furthermore, the biggest risk factor for
EARR is known to be duration of overall orthodontic treatment. Since the overall
treatment time or types of tooth movements were not controlled in subjects, it is
uncertain that the observed root resorption in this study was solely due to intrusion
forces.
Small sample size may have undermines the reliability of this study. We only
had a sample of eighteen patients and ten of which were excluded from the study since
they did not seem to have undergone true intrusion. A study with low statistical power
and small sample reduces chance of detecting a true effect. A study with a larger
sample size should be conducted to verify the outcome of this study.
All the measurements were done by only one observer. This could have caused
random measurement error and negative numbers in table 6. Negative numbers
suggest possible growth of teeth; deposition of cementum. Although some report that
there is an ongoing deposition of cementum throughout life (Zander and Hurzeler, 1958),
it is unlikely to see 2mm of root development as observed in patient GS. The
inadequate quality of CBCT scans added to sources of measurement errors. Figure 16
shows how it is difficult to pinpoint the exact position of the root apex due to blurriness
41 | P a g e

of the image. Since the measurement range for the root resorption is in mm, it is difficult
to accurately measure on scans with this resolution.

Figure 16. Inaccuracy in determining the apex of the root.

Figure 17. Close-up of cephalometric image developed from CBCT scan.
42 | P a g e

Some subjects had extensive dental restorations done on molars (Figure 21).
Restorations such as crowns and large amalgams cause distortions or artifacts on the
images, which may result in inaccurate measurements. Metallic artifacts can make it
difficult for observers to make reliable and accurate linear measurements.
CBCT has disadvantage of higher noise and lower contrast than conventional
medical CT. Due to the low contrast of CBCT, it is difficult to detect the exact boundary
between the root of the teeth and the alveolar bone. This may have added inaccuracy to
the measurement of root lengths before and after. CBCT with a better contrast value
and higher resolution should be considered in future studies.

Possible Future Steps
Results could have been more accurate if some factors are controlled. In future
studies, immediate before and after the intrusion scans are recommended.
Furthermore, it is advisable to only apply intrusive forces in between the scans to limit
potential effects from the other orthodontic movements.
Resolution of CBCT scans could improve using a smaller field of study with a
smaller voxel size. Kolsuz et al. compared the influence of field of view sizes and
different voxel resolutions in CBCT scans (Kolsuz et al., 2015). They showed that the
quality of CBCT could be improved using a smaller field of view size and voxel size.
This could decrease the intra-observer error and increase the accuracy of the
measurements, increasing the validity of the study.

43 | P a g e

IX. Conclusion
Molar intrusion using TADs can now provide an alternative treatment option for
orthodontic patients with conditions such as anterior open bite. When molars are
intruded by using TADs, roots are susceptible for resorption. This study showed that
the amount of external apical root resorption associated with orthodontic treatment
involving intrusion is insignificant as fifteen teeth out of sixteen teeth had less than 4mm
root resorption. This suggests that molars are likely to successfully undergo intrusion
without significant root resorption. However, further studies must be done to test the
validity of this study. Factors including types of forces applied to teeth, duration of force
application, and duration between before and after CBCT scans should be controlled.
Furthermore, the better quality CBCT scans should be used to minimize intra-observer
error and increase the validity of the study. This could be done by using a smaller voxel
size and smaller field of view that focuses around the molars of interest.

44 | P a g e

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XI. Appendix
Appendix A: OnDemand 3D coordinates Raw
SY Before

After
x y z x1 y1 z2
0 0 0 0 0 0
Sella 0.5 63.37 -8.38 0.5 62.62 -4.49
R Po -62.81 84.91 -25.49 -61.37 86.92 -21.13
R or -31.61 8.34 -25.49 -29.58 9.06 -24.72
L or 28.11 8.34 -25.49 27.74 9.06 -24.72

MB root R 24.1 20.44 -58.23 25.18 24.93 -55.21
DB root R 25.87 24.38 -58.03 26.63 28.83 -55.21
Palatal root R 17.61 24.77 -57.05 18.4 28.97 -52.8
CEJ R 19.77 21.82 -68.06 22.92 25.36 -65.78

MB root L -27.43 28.7 -53.9 -25.68 23.2 -55.05
DB root L -27.23 31.65 -53.31 -25.68 26.23 -53.89
Palatal root L -18.97 23.98 -57.05 -19.05 27.1 -51.67
CEJ L -26.84 19.85 -68.06 -24.68 24.64 -65.66

NY1 Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 64.4 -16.96 0.5 64.33 -16.24
R Po -66.16 88.24 -29.97 -64.84 89.41 -29.18
R or -30.92 8.56 -29.97 -30.17 8.76 -29.18
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L or 30.1 8.56 -29.97 31.25 8.76 -29.18
MB root R 26.01 17.39 -61.84 26.46 17.16 -61.38
DB root R 28.36 22.91 -62.44 28.47 23.02 -61.69
Palatal root R 17.47 24.62 -60.22 16.69 24.77 -58.75
CEJ R 23.54 16.08 -72.81 24.16 16.44 -71.95

MB root L -25.55 16.72 -64.28 -26.08 16.75 -63.68
DB root L -27.04 18.85 -63.42 -27.34 19.65 -62.54
Palatal root L -16.16 22.48 -61.92 -16.38 22.74 -60.99
CEJ L -24.46 14.59 -75.16 -23.74 15.22 -75.1

YS Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 61.31 -10.1 0.5 61.56 -9.53
R Po -60.59 87.85 -24.92 -59.22 88.83 -24.3
R or -32.22 8.24 -24.92 -34.19 9.47 -24.3
L or 33.61 8.24 -24.92 33.19 9.47 -24.3

MB root R 21.59 22.57 -52.9 22.69 24.44 -52.81
DB root R 21.59 24.79 -52.49 22.98 25.9 -52.23
Palatal root R 16.94 26.61 -52.2 19.65 27.47 -51.32
CEJ R 21.64 20.95 -62.5 21.59 23.18 -63.57

MB root L -25.74 23.81 -54 -24.59 25.5 -54.27
DB root L -26.75 25.15 -54.3 -25.75 26.55 -53.78
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Palatal root L -19.53 28.18 -53.1 -18.79 30.03 -51.59
CEJ L -21.86 23.47 -63.52 -20.48 25.6 -63.79

GS Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 67.68 -1.19 0.5 66.98 -0.98
R Po -57.55 85.02 -28.61 -57.58 87.74 -27.34
R or -33.61 11.86 -28.61 -33.44 12.07 -25.13
L or 34.61 11.86 -28.61 35.54 12.07 -25.13

MB root R 27.69 35.17 -60.77 28.95 27.2 -59.34
DB root R 29.15 37.22 -59.78 29.6 29.48 -58.74
Palatal root R 22.13 37.95 -61.86 21.63 31.1 -59.32
CEJ R 28.78 33.71 -68.45 27.86 24.92 -68.59

MB root L -26.25 26.89 -65.06 -25.31 26.88 -61
DB root L -27.39 30.45 -64.75 -26.78 30.13 -61.34
Palatal root L -20.26 32.02 -62.26 -19.3 31.92 -59.23
CEJ L -25.22 24.72 -75.65 -25.41 24.6 -72.4

JH Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 63.97 -2.96 0.5 63.29 -2.26
R Po -57.49 87.51 -28.74 -54.54 86.36 -25.83
52 | P a g e

R or -35.31 11.96 -28.74 -34.89 10.89 -25.83
L or 31.03 11.96 -28.74 31.16 10.89 -25.83

MB root R 25.47 27.06 -59.26 27.1 27.74 -55.71
DB root R 26.52 30.43 -56.52 27.87 30.44 -53.59
Palatal root R 19.58 31.69 -55.68 19.96 31.6 -52.43
CEJ R 23.27 27.07 -70.22 24.06 27.78 -66.13

MB root L -29.02 29.59 -59.01 -27.33 28.54 -55.52
DB root L -29.49 32.27 -58.1 -29.05 31.41 -53.99
Palatal root L -22.4 33.53 -57.63 -20.83 32.55 -53.99
CEJ L -28.33 28.18 -70.02 -26.64 27.4 -67.17

KD Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 60.95 -10.55 0.5 6.36 -10.61
R Po -53.31 84.19 -27.92 -51.58 83.53 -28.47
R or -28.96 6.61 -27.92 -29.66 7.21 -28.47
L or 29.72 6.61 -27.92 29.33 7.21 -28.47

MB root R 24.36 15.76 -60.88 25.87 18.33 -60.53
DB root R 26.11 21.17 -60.07 26.64 23.11 -58.83
Palatal root R 17.36 23.55 -58.96 18.16 25.42 -57.26
CEJ R 23.49 16.47 -69.94 23.43 20.33 -69.14

53 | P a g e

MB root L -22.09 20.17 -58.87 -23.3 20.95 -57.99
DB root L -22.36 24.56 -59.04 -25.3 25.27 -57.4
Palatal root L -14.81 23.47 -57.95 -16.05 25.27 -56.17
CEJ L -19.71 18.36 -69.02 -19.71 20.79 -68.97
GE Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 59.62 -2.53 0.5 58.91 -2.58
R Po -60.05 71.6 -22.07 -60.05 85.22 -22.21
R or -29.45 6.82 -22.07 -28.38 5.74 -22.21
L or 28.31 6.82 -22.07 30.66 5.74 -22.21

MB root R 23.27 17.26 -48.94 24.43 14.59 -48.47
DB root R 25.78 20.24 -48.31 26.61 17.8 -47.58
Palatal root R 16.7 21.96 -47.68 17.1 19.73 -46.92
CEJ R 24.79 16.14 -60.6 24.85 13.44 -60.54

MB root L -23.8 17.35 -52 -23.06 15.23 -52.31
DB root L -25.96 21.1 -52.06 -25.5 19.09 -52.41
Palatal root L -17.02 22.25 -50.33 -15.99 20.12 -50.48
CEJ L -24.42 15.58 -63.15 -24.88 14.59 -63.59

YS2 Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 66.61 -10.21 0.5 66.65 -8.19
54 | P a g e

R Po -66.54 87.84 -25.26 -67.43 87.9 -25.22
R or -33.51 7.88 -25.26 -33.78 9.31 -25.22
L or 28.83 7.88 -25.26 28.03 9.31 -25.22

MB root R 23.77 24.98 -57.78 24.49 27.51 -57.03
DB root R 25.78 27.38 -56.18 26.34 29.91 -55.4
Palatal root R 16.69 27.25 -55.38 16.51 29.91 -53.97
CEJ R 23.85 23.91 -67.8 23.23 28.01 -67.95

MB root L -26.59 23.2 -56.61 -26.12 25.35 -56.47
DB root L -28.83 26.27 -56.25 -28.78 28.67 -55.8
Palatal root L -19.99 26.86 -54.49 -19.47 29.17 -53.97
CEJ L -28.05 22.73 -68.16 -28.42 26.35 -67.43

GH Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 65.96 -4.9 0.5 65.39 -8.17
R Po -54.75 86.32 -23.99 -48.16 87.75 -24.77
R or -32.97 6.37 -23.99 -33.62 4.97 -24.77
L or 29.39 6.37 -23.99 30.83 4.97 -24.77

MB root R 22.67 14.16 -56.97 22.89 11.68 -60.29
DB root R 24.05 17.6 -56.42 25.34 15.47 -59.51
Palatal root R 15.12 18.56 -58.31 16.99 16.13 -60.27
CEJ R 22.88 13.75 -66.55 22.79 11.79 -69.28
55 | P a g e

MB root L -23.83 19.72 -57.99 -23.96 18.36 -58.65
DB root L -25.03 22.38 -57.79 -25.41 21.14 -58.31
Palatal root L -19.59 24.37 -56.53 -19.28 23.15 -57.77
CEJ L -25.52 16.67 -66.35 -25.54 15.55 -66.23

JS Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 66.89 -5.28 0.5 63.2 -5.06
R Po -76.01 96.09 -26.27 -79.62 91.16 -28.46
R or -33.39 6.97 -26.27 -34.9 6.65 -28.46
L or 36.94 6.97 -26.27 34.95 6.65 -28.46

MB root R 26.13 17.19 -62.94 26.87 21.27 -59.41
DB root R 25.57 23.5 -62.96 25.63 26.91 -59.26
Palatal root R 19.26 24.34 -60.26 18.39 26.74 -56.95
CEJ R 24.34 19.43 -74.98 25.81 23.74 -72.31

MB root L -27.39 17.05 -63.33 -28.19 20.21 -59.83
DB root L -26.69 22.79 -63.44 -27.13 24.44 -59.53
Palatal root L -19.69 23.78 -61.8 -20.25 26.74 -57.76
CEJ L -24.86 18.35 -75.09 -24.2 23.74 -72.76

KM Before

After
x y z x1 y1 z2
56 | P a g e

Nasion 0 0 0 0 0 0
Sella 0.5 63.4 -7.18 0.5 63.01 -7.41
R Po -65.89 84.66 -28.48 -69.4 83.53 -28.5
R or -32.32 6.71 -28.48 -32.05 6.62 -28.5
L or 29.62 6.71 -28.48 29.62 6.62 -28.5

MB root R 25.79 15.97 -57.23 25.89 16.06 -56.97
DB root R 26.83 18.84 -56.71 27.26 18.03 -56.18
Palatal root R 16.53 20.53 -54.23 17.04 20.19 -54.22
CEJ R 23.17 14.16 -67.39 23.59 14.09 -67.39

MB root L -23.49 16.91 -57.62 -22.62 17.24 -57.18
DB root L -25.02 18.62 -57.59 -23.41 18.22 -56.39
Palatal root L -14.27 19.53 -54.52 -13.97 19.21 -54.03
CEJ L -20.63 14.31 -68.77 -20.12 14.29 -68.58

PM Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 62.87 -15 0.5 62.14 -14.95
R Po -67.81 86.77 -26.05 -63.7 84.77 -25.72
R or -31.04 5.26 -26.05 -35.24 5.4 -25.72
L or 31.07 5.26 -26.05 30.37 5.4 -25.72

MB root R 25.66 22.43 -58.3 25.66 22.59 -59.06
DB root R 26.14 25.01 -58.63 26.16 24.76 -58.89
57 | P a g e

Palatal root R 20.01 25.33 -58.7 19.89 62.09 -58.36
CEJ R 25.07 20.33 -67.25 25.93 20.76 -67.19

MB root L -24.77 20.82 -60.54 -25.73 21.59 -60.29
DB root L -25.09 23.24 -59.74 -26.9 23.93 -59.29
Palatal root L -18.96 24.85 -58.28 -20.07 25.26 -57.46
CEJ L -23.83 19.69 -68.61 -23.9 19.59 -68.29

SE Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 61.81 -9.34 0.5 61.56 -8.43
R Po -56.92 85.32 -25.45 -56.79 89.03 -24.34
R or -32.43 7.18 -25.45 -32.06 7.65 -24.44
L or 29.7 7.18 -24.45 30.06 7.65 -24.44

MB root R 26.35 16.42 -61.4 26.69 17.32 -61.07
DB root R 27.73 20.35 -61.87 27.58 21.12 -61.39
Palatal root R 19.86 21.73 -60.1 19.65 22.79 -59.59
CEJ R 22.17 15.24 -69.93 22.71 16.47 -69.86

MB root L -26.41 15.04 -60.86 -26.04 16.09 -60.82
DB root L -27.78 18.19 -61.45 -27.71 19.22 -61.49
Palatal root L -19.92 20.55 -61.26 -19.22 22.12 -60.59
CEJ L -24.63 13.16 -71.32 -24.15 13.95 -71.13

58 | P a g e

BS Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 65.44 -4.68 0.5 65.95 -5.74
R Po -59.58 92.05 -23.73 -59.77 92.32 -23.86
R or -29.36 11.54 -23.73 -29.19 11.02 -23.86
L or 30.3 11.54 -23.73 28.97 11.02 -23.86

MB root R 26.53 28.72 -54.63 26.84 27.02 -55.56
DB root R 25.94 31.2 -53.36 26.23 29.86 -54.03
Palatal root R 20.4 31.55 -51.95 21.56 30.27 -53.22
CEJ R 22.8 29.55 -63.73 22.03 28.24 -63.59

MB root L -25.84 29.84 -52.38 -25.34 28.2 -52.77
DB root L -26.74 31.19 -51.93 -26.44 30.04 -52.9
Palatal root L -23.05 32.64 -51.15 -22.77 31.5 -52.04
CEJ L -23.77 30.73 -62.29 -23.79 29.06 -63.4

YJ Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 55.13 -19.03 0.5 57.15 -10.39
R Po -42.56 85.93 -29.29 -54.81 82.07 -29.45
R or -32.7 2.37 -29.29 -32.78 6.7 -29.45
L or 31.58 2.37 -29.29 32.47 6.7 -29.45

59 | P a g e

MB root R 25.31 7.61 -57.88 27.08 17.36 -57.67
DB root R 25.58 12.06 -29.07 26.94 21.43 -58.23
Palatal root R 17.93 13.45 -57.8 18.95 22.65 -56.51
CEJ R 25.48 6.91 -68.1 27.05 17.36 -68.02

MB root L -28.66 9.56 -58.88 -27.66 17.77 -57.59
DB root L -27.96 13.31 -59.5 -27.12 22.51 -58.66
Palatal root L -19.19 14.57 -57.14 -18.45 23.59 -56.22
CEJ L -27.32 8.3 -69.53 -27.35 18.31 -68.14

YM Before

After
x y z x1 y1 z2
Nasion 0 0 0 0 0 0
Sella 0.5 65.99 -9.59 0.5 65.69 -9.82
R Po -58.27 81.58 -26.56 -58.56 79.51 -27.53
R or -33.96 10.97 -26.56 -34.27 9.66 -27.53
L or 27.62 27.04 -68.05 31.09 9.66 -27.53

MB root R 27.62 27.04 -68.05 29.96 24.61 -69.32
DB root R 29.88 32.44 -69.33 29.32 30.31 -70.7
Palatal root R 20.47 34.53 -66.89 20.08 31.88 -68.73
CEJ R 28.74 26.73 -78.01 28.46 24.38 -78.57

MB root L -23.75 23.59 -71.47 -23.95 21.26 -72.69
DB root L -25.67 29.13 -71.35 -25.71 26.4 -73.55
Palatal root L -18.08 30.82 -71.55 -18.37 28.41 -72.98
CEJ L -25.36 23.23 -78.18 -25.76 20.34 -78.12

60 | P a g e

IJ
x y z
Nasion 0 0 0
Sella 0.5 58.77 -11.42
R Po -51.78 82.86 -28.25
R or -36.64 9.42 -28.25
L or 33.88 9.42 -28.25

MB root R 25.05 25.28 -53.08
DB root R 26.37 31.52 -52.05
Palatal root R 17.47 28.37 -51.31
CEJ R 23.59 26.15 -62.84

MB root L -26.96 25.7 -52.23
DB root L -27.5 31.62 -51.26
Palatal root L -19.42 30.44 -51.25
CEJ L -27.61 26.35 -61.26

PH
x y z
Nasion 0 0 0
Sella 0.5 -4.34 -2.17
R Po -58 14.68 -20.78
R or -38.13 -58.13 -20.78
L or 33 -58.13 -20.78

61 | P a g e

MB root R 23.51 -45.67 -55.85
DB root R 23.12 -43.67 -55.71
Palatal root R 17.12 -42.52 -56.87
CEJ R 24.65 -46.35 -66.95

MB root L -27.17 -45.58 -57.93
DB root L -27.81 -43.8 -57.03
Palatal root L -20.92 -42.77 -57.09
CEJ L -26.95 -46.73 -68.32

Appendix B: OnDemand: Change in Root Length for each patient

SY
ΔY ΔY'
MB root R 1.38 0.43
DB root R 2.56 3.47
Palatal root
R 2.95 3.61

MB root L 8.85 1.44
DB root L 11.8 1.59
Palatal root
L 4.13 2.46
NY
ΔY ΔY'
MB root R 1.31 0.72
62 | P a g e

DB root R 6.83 6.58
Palatal root
R 8.54 8.33

MB root L 2.13 1.53
DB root L 4.26 4.43
Palatal root
L 7.89 7.52
YS1
ΔY ΔY'
MB root R 1.62 1.26
DB root R 3.84 2.72
Palatal root
R 5.66 4.29

MB root L 0.34 0.1
DB root L 1.68 0.95
Palatal root
L 4.71 4.43
GS
ΔY ΔY'
MB root R 1.46 2.28
DB root R 3.51 4.56
Palatal root
R 4.24 6.18

MB root L 2.17 2.28
DB root L 5.73 5.53
63 | P a g e

Palatal root
L 7.3 7.32
JH
ΔY ΔY'
MB root R 0.01
-
0.04
DB root R 3.36 2.66
Palatal root
R 4.62 3.82

MB root L 1.41 1.14
DB root L 4.09 4.01
Palatal root
L 5.35 5.15
KD
ΔY ΔY'
MB root R 0.71 2
DB root R 4.7 2.78
Palatal root
R 7.08 5.09

MB root L 1.81 0.16
DB root L 6.2 4.48
Palatal root
L 5.11 4.48
GE
ΔY ΔY'
64 | P a g e

MB root R 1.12 1.15
DB root R 4.1 4.36
Palatal root
R 5.82 6.29

MB root L 1.77 0.64
DB root L 5.52 4.5
Palatal root
L 6.67 5.53

YS2
ΔY ΔY'
MB root R 1.07 0.5
DB root R 3.47 1.9
Palatal root
R 3.34 1.9

MB root L 0.47 1
DB root L 3.54 2.32
Palatal root
L 4.13 2.82
GH
ΔY ΔY'
MB root R 0.41 0.11
DB root R 3.85 3.68
Palatal root
R 4.81 4.34
65 | P a g e

MB root L 3.05 2.81
DB root L 5.71 5.59
Palatal root
L 7.7 7.6

JS
ΔY ΔY'
MB root R 2.24 2.47
DB root R 4.07 3.17
Palatal root
R 4.91 3

MB root L 1.3 3.53
DB root L 4.44 0.7
Palatal root
L 5.43 3
KM
ΔY ΔY'
MB root R 1.81 1.97
DB root R 4.68 3.94
Palatal root
R 6.37 6.1

MB root L 2.6 2.95
DB root L 4.31 3.93
Palatal root
L 5.22 4.92

66 | P a g e

PM
ΔY ΔY'
MB root R 2.1 1.83
DB root R 4.68 4
Palatal root
R 5 5.33

MB root L 1.13 2
DB root L 3.55 4.34
Palatal root
L 5.16 5.67
SE
ΔY ΔY'
MB root R 1.18 0.85
DB root R 5.11 4.65
Palatal root
R 6.49 6.32

MB root L 1.88 2.14
DB root L 5.03 5.27
Palatal root
L 7.39 8.17
BS
ΔY ΔY'
MB root R 0.83 1.22
DB root R 1.65 1.62
Palatal root
R 2 2.03
67 | P a g e

MB root L 0.89 0.86
DB root L 0.46 0.98
Palatal root
L 1.91 2.44

YS
ΔY ΔY'
MB root R 0.7 0
DB root R 5.15 4.07
Palatal root
R 6.54 5.29

MB root L 1.26 0.54
DB root L 5.01 4.2
Palatal root
L 6.27 5.28
YM
ΔY ΔY'
MB root R 0.31 0.23
DB root R 5.71 5.93
Palatal root
R 7.8 7.5

MB root L 0.36 0.92
DB root L 5.9 6.06
Palatal root
L 7.59 8.07
68 | P a g e

Appendix C: OnDemand Calculated Intrusion and Resorption amount on each
root.
Intrusion Resorption MB Resorption DB Resorption P
SY Right 4.29 0.95 -0.91 -0.66
SY Left 5.54 7.41 10.21 1.67
NY Right 0.29 0.59 0.25 0.21
NY Left 0.83 0.6 -0.17 0.37
YS1 Right 2.48 0.36 1.12 1.37
YS1 Left 2.38 0.24 0.73 0.28
GS Right -9.49 -0.82 -1.05 -1.94
GS Left 0.09 -0.11 0.2 -0.02
JH Right 0.03 0.05 0.7 0.8
JH Left -1.46 0.27 0.08 0.2
KD Right 3.27 -1.29 1.92 1.99
KD Left 3.03 1.65 1.72 0.63
GE Right -3.41 -0.03 -0.26 -0.47
GE Left -1.7 1.13 1.02 1.14
YS2 Right 4.14 0.57 1.57 1.44
YS2 Left 3.66 -0.53 1.22 1.31
GH Right -2.53 0.3 0.17 0.47
GH Left -1.69 0.24 0.12 0.1
JS Right 0.62 -0.23 0.9 1.91
JS Left 1.7 -2.23 3.74 2.43
KM Right -0.46 -0.16 0.74 0.27
KM Left -0.41 -0.35 0.38 0.3
PM Right 0.7 0.27 0.68 -0.33
PM Left 0.17 -0.87 -0.79 -0.51
SE Right 0.98 0.33 0.46 0.17
69 | P a g e

SE Left 0.54 -0.26 -0.24 -0.78
BS Right -0.8 -0.39 0.03 -0.03
BS Left -1.16 0.03 -0.52 -0.53

Abstract (if available)

Abstract Introduction: Temporary anchorage devices (TADs) have transformed treatment planning in orthodontics as they can provide alternative options to orthognathic surgeries

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Asset Metadata

Creator Kim, Jae (author)

Core Title Root resorption of maxillary molar after intrusion by using TADs

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 03/12/2018

Defense Date 02/23/2018

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

Tag intrusion,OAI-PMH Harvest,root resorption,temporary anchorage devices

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Sameshima, Glenn (committee chair), Grauer, Dan (committee member), Paine, Michael (committee member)

Creator Email Kimjae@usc.edu,kimjae6@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-483881

Unique identifier UC11267011

Identifier etd-KimJae-6100.pdf (filename),usctheses-c40-483881 (legacy record id)

Legacy Identifier etd-KimJae-6100.pdf

Dmrecord 483881

Document Type Thesis

Rights Kim, Jae

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

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