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Mandibular plane angle changes with or without premolar extraction treatment in adult orthodontics measured using 3-D cone beam technology
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Mandibular plane angle changes with or without premolar extraction treatment in adult orthodontics measured using 3-D cone beam technology
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Content
MANDIBULAR PLANE ANGLE CHANGES WITH OR WITHOUT PREMOLAR
EXTRACTION TREATMENT IN ADULT ORTHODONTICS
MEASURED USING 3-D CONE BEAM TECHNOLOGY
by
Jenny Yoo
A Thesis Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(CRANIOFACIAL BIOLOGY)
May 2010
Copyright 2010 Jenny Yoo
ii
DEDICATION
To my family, friends, and co-residents
who have kept me together in one piece
iii
ACKNOWLEDGEMENTS
Dr. Holly Moon
Dr. Jeong-Ho Choi
Dr. Sameshima
Dr. Michael Paine
Ellen Grady
Dede
Louisa
My Co-Residents (Class of 2010)
Class of 2011
Class of 2012
iv
TABLE OF CONTENTS
Dedication ii
Acknowledgements iii
List of Tables v
List of Figures vi
Abstract vii
Chapter 1: Introduction 1
Chapter 2: Review of Literature 5
Chapter 3: Hypothesis 22
Chapter 4: Materials and Methods 24
Chapter 5: Results 34
Chapter 6: Discussion 41
Chapter 7: Assumptions 45
Chapter 8: Limitations 46
Chapter 9: Conclusions 47
Bibliography 49
v
LIST OF TABLES
Table 5.1: Initial Comparison of Non-Extraction and Extraction Groups 34
Table 5.2: Comparison of Initial Measurements between Non-Extraction and Extraction Groups 36
Table 5.3: Comparison of Initial Mandibular Angle and Mandibular Changes in Both Groups 37
Table 5.4: Comparison of Incisor Movement and Mandibular Changes in Both Groups 38
Table 5.5: Comparison of Molar Movement and Mandibular Changes in Both Groups 39
Table 5.6: Comparison of Horizontal and Vertical Changes in the Mandible and Molars 40
Table 5.7: Comparison of Molar Horizontal and Vertical Movement 40
vi
LIST OF FIGURES
Figure 2.1. 3D Images formed by Cone Beam Computed Tomography 11
Figure 2.2. The Newtom QR-DVT 3G 13
Figure 2.3. Broadbent’s Superimposition Registered @ R 15
Figure 2.4. Bjork’s Mandibular Superimposition Structures 17
Figure 2.5. Rickett’s Mandibular Superimposition Method 17
Figure 2.6. Kawamata’s 3D Superimposition Method 19
Figure 2.7. Hajeer’s 7-point Soft Tissue Superimposition 19
Figure 2.8. Computerized Superimposition Using Corresponding Voxel Information 20
Figure 4.1. Viewing Two 3D Images Using OnDemand 3D 25
Figure 4.2. Superimposing Images on Cranial Base as Identified by the Blue Box 26
Figure 4.3. Viewing Superimposed Images Using a Sagittal Cut 26
Figure 4.4. Measuring Changes at the Incisal Tip 27
Figure 4.5. Making an Image Slice Through the Arch Form 28
Figure 4.6. Measuring Changes in Molar Movement 29
Figure 4.7. Superimposing Images on the Mandible 30
Figure 4.8. Measuring Changes at the Incisal Tip of the Lower Incisor 31
Figure 4.9. Making an Image Slice Through the Arch Form 32
vii
ABSTRACT
The purpose of this study was to determine whether extraction of four premolars
in orthodontic treatment results in closing of the mandibular plane angle, also called the
‘wedge effect’. Method: Using a new program, OnDemand3D™, pre-treatment and post-
treatment 3D cone beam CT scans of 54 patients at the University of Southern
California’s School of Dentistry were superimposed to compare changes during
orthodontic treatment. Using 3D scans to measure changes eliminates distortion effects
from traditional lateral cephalograms, landmark identification errors, and superimposition
errors. The two 3D scans were superimposed initially on the cranial base. Viewing the
image in the sagittal plane, horizontal and vertical changes at the most anterior and most
posterior point on the mandible, respectively, were measured in millimeters. Changes at
the incisal edge of the central incisor were also measured horizontally and vertically.
Then an image slice was made through the arch form to measure horizontal and vertical
changes of the maxillary left and right first molar. The two images were then
superimposed on the anterior mandibular body. Using similar views, horizontal and
vertical measurements were made for the lower central incisor and lower left and right
first molar. Results: There was no significant difference (p>0.05) in mandibular
movement with extraction of four first premolars and non-extraction orthodontic
treatment. In the extraction group, there was a significant (p<0.05) lingual movement of
the upper and lower incisors as well as significant (p<0.05) mesial movement of the
upper and lower molars compared to the non-extraction group. The mandible showed no
significant (p>0.05) difference between the extraction and the non-extraction group.
There was a correlation (p>0.05) in lingual movement of the incisors and horizontal
viii
movement of the mandible as well as vertical displacement of the incisors and vertical
movement of the mandible. Vertical movement of the molars was correlated (p<0.05)
with vertical movement of the mandible. Horizontal movement of the upper and lower
molars were correlated (p<0.05) as well as vertical movement of the upper and lower
molars. Conclusion: There is no ‘wedge effect’ when extracting four premolars in
orthodontic treatment. Vertical movement of the molars should be controlled as there is
an increase in vertical facial dimension with extrusion of the molars during mesialization
for extraction treatment.
1
CHAPTER 1: INTRODUCTION
Orthodontic treatment aims to not only straighten teeth but to create facial
balance. A patient’s facial balance is measured in all three planes of space, width, length
and height
[1]
. A treatment plan is created to address the patient’s chief complaint and to
align the patient’s teeth that will provide the best functional occlusion as well as an
improved facial balance. When treatment planning and diagnosing an orthodontic patient,
many factors must be considered to maintain or improve facial balance. In the case of a
patient with increased vertical dimension, closing the mandibular plane angle has
continued to be a challenge to orthodontists. Many treatment decisions, including
extractions, have been recommended for closing the vertical dimension.
Extractions are commonly recommended in orthodontics to create space in the
dental arch and alleviate any crowding of teeth. Extractions can also be used in cases of
facial imbalance, such as if the patient’s lips are too protrusive and retraction of the
anterior teeth will restore balance to the patient’s face. Some clinicians have argued that
extraction of premolars will decrease the vertical dimension and restore facial balance.
This ‘angle of facial divergence’ was first studied by Shudy
[2]
. Shudy studied the effect
that by changing the mandibular plane angle, mandibular prognathism and vertical facial
height could be changed. As the mandibular plane angle closes, the mandible swings
forward to close. This then increases mandibular prognathism and decreases facial height.
As the mandibular plane angle closes, the mandible swings forward to close. This
increases mandibular prognathism and decreases vertical facial height. The ‘wedge
effect’ then states that by extracting second premolars, the molars can be mesialized more
2
than with first premolar extraction and causes a decrease in vertical facial height
[2,3,4]
.
The ‘wedge effect’ assumes that by moving the posterior teeth more forward in the
mouth, the angle of the mandible is no longer propped open and can close down. This
rationale has been used in arguing for second premolar extractions to help close an open
bite or to decrease the vertical dimension.
However, many studies have been done to disprove this theory
[5-9]
. In 1999,
Kocadereli studied the effect on vertical dimension with non-extraction versus first
premolar extraction treatment
[10]
. He concluded that both groups showed an increase in
vertical dimension but there was no significant difference between the two groups.
However, both groups included patients who still had a potential for growth so he
attributed the increase in vertical dimension to remaining growth. In a more recent study
in 2010 by Kumari, changes in vertical dimension with extraction versus non-extraction
treatment were studied
[11]
. Kumari also found that there was an overall increase in
vertical dimension but no significant difference between the two groups. This study also
included patients who still had remaining growth potential.
Previous studies regarding the ‘wedge effect’ were done using conventional
lateral cephalograms. However, all conventional lateral cephalograms have an inherent
distortion due to the increasing magnification from the center of the film as well as
changes in patient positioning. In addition to the distortion found within the image,
superimpositions of traced lateral cephalograms include landmark identification errors.
Midtgard found landmark identification errors from 0.5mm to over 2mm of discrepancy
[12]
. Measurement errors can become quite significant with the additive effect of the errors
3
when superimposing tracings. The introduction of 3D cone beam imaging has eliminated
the distortion of each patient’s image and the patient can be reoriented within the imaging
software. A new program called OnDemand3D™ by CyberMed, superimposes two
dicomm images from the same patient based on a mathematical formula called the mutual
information theory. Using a computer model for superimpositions, human error in
landmark identification can be eliminated.
In this study, 54 adult patients from the University of Southern California School
of Dentistry (USCSD) Department of Orthodontics were identified. This study measured
the amount of facial height change before and after orthodontic treatment using archival
data acquired from 3D cone beam scans taken using the NewTom QR-DVT 3G. Using
the OnDemand3D™ program, initial and final dicom images were superimposed to
determine the precise amount of tooth movement as well as skeletal changes that occur in
a patient due to orthodontic treatment. This study will help clarify the claim that there are
no differences in vertical facial height with extraction versus non-extraction treatment by
eliminating distortion of the images, reducing landmark identification errors, and
eliminating growth of the patients.
Purpose of the Study
- Determine whether significant differences in vertical facial height exist in
extraction or non-extraction orthodontic treatment
4
- Determine if using 3D cone beam technology and computerized superimpositions
will lead to significant differences in measurements compared to using lateral
cephalograms
5
CHAPTER 2: REVIEW OF THE LITERATURE
Normal Facial Growth
Facial esthetics is one of the key diagnostic factors in determining a treatment
plan for each orthodontic patient. During orthodontic treatment, orthodontists plan to
either maintain or improve facial balance. Patients often seek an orthodontist to straighten
their teeth, but orthodontists must take into consideration a patient’s face and profile in
order to assess the best method to create a balanced face. At birth, the width of the
cranium has reached its full dimension and cannot be changed. However, as the face
grows through childhood, the depth of the face reaches its potential around 14-15 years of
age and the vertical height of the face completes its growth a few years later
[1]
.
Orthodontists can try and manipulate the growth potential during the adolescent years or
manipulate the vertical dimension in the adult years.
During the growth period, the vertical dimension of the face is established by
growth at the sutures connecting the cranial base to the maxilla, as well as growth of the
mandible itself. The maxilla is carried downward and forward by two mechanisms. There
is apposition of bone at the cranial base that pushes the maxilla down and forward and
there is growth of the maxilla itself. Increase of mandibular height is associated with
growth at the lower portion of the cranial base which carries the mandibular fossae
downward and causes an overall increase of the facial height
[13]
. The mandible itself
grows in a downward and forward direction by growth at the ramus, coronoid, and
condylar process
[1]
. Vertical dimension is also influenced by the direction of condylar
growth that causes mandibular rotation during growth
[13]
.
6
Classification of vertical facial dimension is often measured at the mandible.
Facial divergence is described as a tangent line along the lower border of the mandible
and the Sella-Nasion line (SN)
[3]
. The larger the angle between SN and the mandibular
plane becomes larger, the mandible is steeper and the vertical height increases. The
smaller the angle, the shorter the vertical facial height becomes. The mandible is then
classified as hypodivergent or hyperdivergent, associated with a short or long facial
height, respectively
[2]
. Hyperdivergent mandibles are associated with a steep mandibular
plane angle and therefore are associated with an increased vertical facial dimension.
Increased vertical height due to a rotational growth of the mandible steepens the
mandibular plane angle and results in a hyperdivergent mandible. Vertical molar
positioning will also influence the position of mandible. An increase in molar eruption
can cause an opening rotation of the mandible, increasing the vertical facial height
[3]
.
Vertical Facial Height Changes With Or Without Extraction Treatment in
Orthodontics
Extraction in orthodontics is used to create facial balance, address midline
discrepancies, alleviate crowding and influence the vertical dimension
[14-21]
. Using the
theory of the ‘wedge effect’, a patient with an elongated lower facial height may be
treatment planned for extraction of teeth in order to decrease the vertical facial height.
The ‘wedge effect’ was described by Shudy that as molars are mesialized, we are able to
close the vertical facial dimension by decreasing the mandibular plane angle
[2-4]
. The
posterior teeth in the mouth help maintain vertical dimension by maintaining alveolar
7
bone height and maintaining freeway space
[3]
. Sassouni also concurred that by reducing
tooth mass, either by intrusion or extraction of teeth, the mandibular plane angle can be
closed
[22]
. Studies have shown that as posterior teeth erupt, there is an increase in
vertical facial dimension
[23]
. Therefore, they have concluded that removal of posterior
teeth will allow closing of the bite. In high angle cases, enucleation of second premolars
has been shown to decrease the vertical dimension
[24]
.
While the theory remains prominent, many studies have been done to determine
whether there is an effect on the mandible during orthodontic treatment
[5-7,25-27]
. Chua, in
1993, studied the effects of extraction versus non-extraction on the lower anterior facial
height in growing patients
[28]
. After adjusting for growth, Chua concluded that there was
no change in facial height in patients who had extraction treatment. However, those who
were treated non-extraction showed an increase in their lower anterior facial height due to
the downward and backward rotation of the mandible. Treatment duration was also
significantly longer in the extraction cases.
Staggers studied the effects of extracting first premolars on the vertical height
[27]
.
The study showed no significant differences between extraction of first premolars
compared to non-extraction treatment. There was an average increase of vertical
dimension in both groups.
In 1999, Kocadereli did a similar study comparing changes in facial vertical
dimension in extraction and non-extraction treatment
[10]
. He found an increase of facial
vertical dimension in both group, but attributed some of the increase to remaining growth
potential. Treatment times were not addressed in this study. Kim studied the effects of
8
extracting first versus second premolars on vertical facial dimension
[29]
. There was found
to be an increase in facial dimension in both extraction groups with no significant
difference between the two groups. Kumari, in 2010, again studied the effects of
extraction and non-extraction treatment in orthodontics
[11]
. With a mean age of 15 in
both groups, an increase was reported in vertical dimension for extraction and non-
extraction treatment but there was no significant difference in the increase of vertical
dimension between the two groups.
Lateral Cephalogram Accuracy
In order to quantitatively study changes in the craniofacial complex, lateral
cephalograms have been used in orthodontics since first introduced by Broadbent in
1931
[30]
. Lateral cephalograms are obtained by positioning patients in a head holder that
positions their midsagittal plane 5 feet away from an x-ray machine on their right side.
The x-ray beam is directed at the center of the ears, which are held in place by ear rods,
and the image is captured on a film placed as close as possible to the left side of the
patient’s head
[31]
. Due to the point-to-area nature of the x-ray beam, there is an inherent
distortion effect of the lateral cephalogram. As the distance increases from the center of
the ear rods, there is an increased magnification error
[32]
.
Different points are identified on a lateral cephalogram from which linear and
angular measurements are made and then compared to numbers that have been accepted
to represent a normal and pleasing face
[33]
. Orthodontists use these cephalometric
numbers to quantitatively measure soft tissue and skeletal dimensions
[34-38]
.
9
Cephalometrics serve as a guideline in making treatment decisions, studying growth, and
comparing the treatment outcomes after orthodontic treatment has been completed
[35]
.
The identified landmarks on a cephalogram vary amongst the analysis, such as
Downs, Ricketts, or Steiner analysis. Baumrind, in 1971, studied 16 commonly used
landmarks and found that the accuracy in identifying these landmarks depended on ‘how
sharply the edge folds in the region of the point being estimated
[39]
. The probability that
a point would be identified successfully was found to be about 95%, leaving 5% for
errors
[40]
. There is a wide range of inter-operator differences in identifying each
landmark and each point has its own characteristic reliability
[41-47]
. Some landmarks are
easier to identify and therefore are more reliable than others. However, some landmarks
have errors of more than 1mm
[44]
. Mitgard studied 15 landmarks and measured the errors
in identification and distance measurements
[12]
. He found landmark errors as great as
2mm and distance measurement discrepancies up to 1.1mm.
Sources of errors found in identifying landmarks in lateral cephalograms include
the quality of the radiograph, the experience of each clinician, machine errors in
identifying the landmarks, superimpositions of the tracings and errors in major axis
locations
[44]
. Some landmarks are defined as ‘the most anterior point’ which becomes a
subjective landmark dependent on the orientation of the skull. Identification of landmarks
is also sometimes difficult due to the anatomy of the skull
[48]
.
Reproducibility of a patient’s cephalogram can also vary. Patient positioning for a
cephalogram is difficult due to the asymmetry inherent in each patient
[32]
. Also,
positioning of the patient in the head holder is very critical because once the image is
10
taken, patient positioning can no longer be manipulated. Any change in rotation of the
patient can make superimpositions difficult
[49]
. When landmarks are identified and then
superimposed, the degree of inconsistency compounds upon itself, decreasing the
reliability of measurements.
As technology continues to advance, digital radiography has become more
common than film radiography. The images are either scanned or captured on a digital
sensor and recorded as pixels. The accuracy of landmark identification is determined by
the pixel size as well as the screen resolution of the computer used to identify the
landmarks
[50]
. Studies have shown that the use of digital radiography have not
significantly affected the accuracy of landmark identification
[51,52]
. These digital images
are then traced using computer software programs, such as Dolphin®. These programs
have not affected reliability, but have decreased operator time in identifying landmarks
and tracing cephalograms
[53]
.
3D Cone Beam Technology
Recently, the use of 3-dimensional computed tomography has become
popularized in all aspects of dentistry. Computed tomography was first introduced in
1967 by Sir Godfrey Hounsfield
[54]
and first used clinically in 1972
[55]
. Now, use of
computed tomography has become standardized in the medical field. Originally, there
was one detector and source which rotated around the patient. As technology advanced,
more detectors were incorporated into the machines.
11
In 1989, cone beam computed tomography was introduced and has been
implemented with a wide variety of uses in dentistry
[55,56]
. Cone beam computed
tomography uses a conical x-ray beam and a two-dimensional detector that allows the
image to be captured in a single rotation around a patient who is either seated or
supine
[57]
(fig. 2.1).
Figure 2.1. 3D Images formed by Cone Beam Computed Tomography
A single rotation of the x-ray beam around the patient has decreased the time
needed to take the image, therefore decreasing patient movement during the scan as well
as radiation to the patient. All 3D images taken are then stored in a format known at
DICOM (Digital Imaging and Communications) allowing information to be easily
distributed among medical professionals, regardless of the scanner used to take the
image
[58]
.
Cone beam technology has now become implemented in all fields of dentistry.
Oral surgeons have used cone beam CT to localize pathology as well as assist in
treatment planning for orthognathic surgery. Location of anatomical structures and
pathology is more reliable because the 3D image can be manipulated and sliced to
12
determine the exact location of the object of interest
[48]
. Periodontists have implemented
cone beam CT for the treatment planning and simulation of implant placement
[59]
.
Orthodontists use cone beam CT to construct panoramic and cephalometric images as
well as identify any pathology that may be present.
Once the image has been taken, a computer software program uses different
algorithms to reconstruct the image for viewing by 3D elements called voxels
[59]
. Voxels
are gray colored cubes that measure the amount of radiation absorbed and form the
viewed image
[58]
. As voxel size decreases, image quality increases as well as radiation
dosage
[60]
. The clarity of the image is also affected by the computer software program
used to view the program as well as the resolution of the computer monitor. Resolution of
the 3D image is also affected by the quality of the sensor and the rotational spacing of the
image slices
[57]
. Resolution of a 3D cone beam image is higher than a conventional CT,
but there is more noise and soft tissue detail that is lost
[59]
.
Currently, patient radiation with a cone beam CT is recorded as low as 98%
reduction in radiation than conventional CTs and comparable to a dental full mouth
radiographic series
[61]
. A full mouth series is measured at ~33 µSv, a digital panoramic
xray is ~2.4-6.2 µSv and a digital cephalometric xray is ~1.6-1.7 µSv
[62]
. Cone beam
CTs are measured at ~40-50 µSv for maxillofacial imaging
[63]
.
Another advantage of using 3D cone beam images is that it is accurate in all
dimensions, eliminating the magnification and distortion found on conventional
radiographs
[56]
. A study by Periago showed that while linear measurements made from a
cone beam CT were slightly less than anatomic measurements, the accuracy was still
13
clinically reliable
[64]
. In 2009, Brown found that errors were below 1mm
[65]
. These
errors were probably due to landmark identification errors, which are also present in
conventional lateral cephalograms. 3D cone beam imaging eliminates errors due to
variation in patient positioning because software used to view the image allows
reorientation of the image in any direction.
The NewTom QR-DVT 3G was used for 3D cone beam imaging at the USCSD
Department of Orthodontics (fig. 2.2). A patient is placed in a supine position and then
positioned in the machine for scanning of the craniofacial complex. The NewTom 3G
takes 75 seconds of scan time with an effective scan time of 36 seconds
[48,59]
and has a
voxel size of about 0.3mm
3
[66]
. It also records voxels in 8 bits, which equals 256 shades
of gray. A NewTom with a large field of view is measured about 42-50 µSv
[62,67]
.
Figure 2.2. The Newtom QR-DVT 3G
The NewTom’s accuracy was found to be within an error of 0.5mm, which is
below the resolution power of the scans
[68]
. In a study by Lascala, the accuracy of
measurements using the NewTom was found to be slightly less than real
14
measurements
[69]
. However, linear measurements were still reliable and a significant
difference was only found for internal structures of the skull. Kragskov determined that
CBCT measurements were less reliable than lateral cephalogram measurements, but these
errors may be due to the introduction of an additional coordinate
[70]
. Similar with lateral
cephalograms, each landmark has a characteristic pattern of error
[63].
Superimposition Techniques
In order to quantitatively measure the changes in skeletal and dental structures
due to growth or orthodontic treatment, it is necessary to compare two radiographs of the
same patient taken at different time points. Two images are overlapped, or superimposed,
on a stable point and changes can then be measured
[13]
. Superimpositions have continued
to be extremely useful in studying treatment results in orthodontics.
Broadbent in 1937, determined that the best way to study overall growth was to
use a fixed point, R, which is the halfway point from Sella to a perpendicular point on the
Bolton-Nasion plane, to superimpose two cephalograms
[30,71]
(fig. 2.3).
15
Figure 2.3. Broadbent’s Superimposition Registered @ R
Ricketts developed a four-step method for superimpositions
[72]
. He used two
points to measure overall growth of the craniofacial complex. Point one superimposed
Basion-Nasion line on the Pterygoid point. Point two superimposed Basion-Nasion on
Nasion. Downs found that the reliability of using S-N, Broadbent’s triangle, or FH was
similar
[36]
; however, he advocated the use of FH plane to study changes in facial
dimension
[73]
. Pancherz studied the reliability of superimposing images on a line formed
by Sella and Nasion
[74]
. He found that there were significant errors in registration of the
two images within and between observers. While studies have shown that cranial base
growth is completed at age 6, changes have been found in the hypophyseal fossa (sella) at
least 10 years later
[75]
.
In a comparison of 4 different methods of superimposition (SN@Sella,
FH@Porion, Least Squared-5, manual geometric superimposition), significant
differences were found in the errors of the same examiner as well as between different
16
examiners
[76]
. The least squared-5 method, which averages the best fit of 5 identified
landmarks, was found to be the most reliable of the four methods.
To measure changes at the maxillary level, Broadbent used the ‘best fit’ method
of superimposition, using the palatal plane (ANS-PNS) registered at ANS to study
growth and change of the maxilla
[30]
. Ricketts, as well as Brodie and Downs, suggested
using the same method
[72]
. Moore also superimposed on palatal plane but registered the
two cephalograms at the pterygomaxillary fissure
[77]
. Bjork and Skieller, in 1977,
suggested the ‘structural method’ in which the cephalograms are superimposed on the
anterior surface of the zygomatic process while positioning the second cephalogram so
that the resorptive lowering of the nasal floor was equal to the amount of apposition at the
orbital floor
[78]
. In a study by Nielsen, it was reported that the ‘best fit’ method by
Broadbent underestimated the vertical growth of the maxilla and underestimated molar
growth 30% and incisor growth 50%, so he advocated the use of the ‘structural method’
instead
[79]
. A study using implants to measure the accuracy of superimposition methods
found that superimposing using the posterior and anterior zygomatic process of the
maxilla was the most reliable method
[80]
.
Mandibular superimpositions were studied by Bjork in 1963 where he
superimposed the mandible using the inferior border of the mandible, the mandibular
canal and the developing molar bud
[81]
(fig. 2.4). Bjork’s method of superimposition was
found to be fairly reliable; however, errors were attributed to tracing and registration
errors. Angular measurements errors were found to be less than 2 degrees
[82]
.
17
Figure 2.4. Bjork’s Mandibular Superimposition Structures
Ricketts superimposed on a reference plane constructed from protuberance menti
to his Xi point and registered at protuberance menti
[72]
(fig. 2.5). Reliability with
Rickett’s method was found to be significant, showing less than 0.3mm of error
[83]
.
However, in comparing Bjork’s and Ricketts’ method of superimposition using tantalum
implants, Bjork’s superimposition method was found to be more reliable
[84]
.
Figure 2.5. Rickett’s Mandibular Superimposition Method
Errors in superimposition measurements can be attributed to many of the same
limitations of tracing lateral cephalograms. Some errors can be due to a difference in
orientation of the patient in x-ray machine when taking the lateral cephalogram. Due to
18
the variability of landmark identification as discussed previously, superimposing two
landmarks may not be exact and will show changes that may only be attributed to
orientation of the overlapping image
[85]
. In addition, precise landmark identification on
each cephalogram after superimposing two radiographs is difficult because of the
inherent variability of each point
[39]
. Baumrind found that more errors were due to the
rotational errors of superimpositions two images rather than the translational errors
[85]
.
The further the measured point is from the superimposed point, the greater the error
becomes.
Superimpositions of 3D scans have overcome some of the limitations presented in
conventional lateral cephalograms. Orientation of the patient can be modified after the
image has been taken to be much more precise. Using 3D images also allow for less
magnification errors and clinician bias in landmark identification. However, previous
methods of superimposing 3D images required landmark identification of about 12-16
points that were then used to overlap the images
[85]
. Registration accuracy was found on
average within 1-2mm. This method of superimposition continues to incorporate
landmark identification errors and rotational effects, even when using computer
programs.
In 1998, Kawamata described a method of superimposing pre-surgical and post-
surgical 3D cone beam images
[86]
. They created a 3D image of the pre-surgical region of
interest followed by a semitransparent 3D image of the post-surgical region of interest
(fig. 2.6). Then using different identifying points on the image, they rotated and
19
overlapped the post-surgical image in the lateral, frontal and axial views until they
overlapped. Then measurements were made from this superimposition.
Figure 2.6. Kawamata’s 3D Superimposition Method
Hajeer in 2002 studied the reproducibility of soft tissue landmark identification on
3D models
[87]
. Using the results, he advocated the use of 7 identifiable and reliable
points on a 3D scan for alignment of two separate 3D images for superimpositions (fig.
2.7).
Figure 2.7. Hajeer’s 7-point Soft Tissue Superimposition
As software advances were made, Cevidanes used a fully automated computer
program to aid in the superimpositions of two 3D models
[88]
(fig. 2.8). A software
program that superimposed the two 3D images based on a mathematical model was used
20
to align corresponding voxels on a specified region
[89]
. Superimpositions were made on
the entire cranial base in adults and the anterior cranial fossae for growing children.
Measurements using this model were found to be no more than 0.26mm between
different observers
[90]
.
Figure. 2.8. Computerized Superimposition Using Corresponding Voxel Information
In order to adjust for normal changes between two images, a non-rigid
mathematical model
[91]
was used to superimpose data that included changes due to
growth and treatment
[92]
. Interexaminer measurements were found to be at least within
0.5mm discrepancy. Differences in measurements were attributed to low contrast that
diminished the boundaries of the images. Also, properties of the surface model could be
adjusted by each examiner. Changes in the surface model would then also affect the
measurements made between the two images.
21
Reliability of computer aided superimpositions increases when the image being
registered has a larger field of view
[74]
. Using corresponding voxels to superimpose the
images increases the reliability compared to other methods of superimposition because
there is less influence by image noise, artifacts and soft tissue deformations.
OnDemand3D™ by Cybermed is a new program that also uses the mutual
information theory in which the intensity values of corresponding voxels of a region of
interest are compared and then aligned
[89]
. Cybermed is the first Korean company to
develop a 3D imaging software. This software allows fully automated superimpositioning
of two 3D images. This eliminates any human error during the processing of 3D images
into 2D images or landmark identification error.
22
CHAPTER 3: HYPOTHESIS
1. How does vertical movement of the mandible compare in patients who have four
premolar extraction treatment versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in vertical mandibular movement between
four premolar extraction treatment versus non-extraction treatment in orthodontics
H
1
: There is a significant difference in vertical mandibular movement between
four premolar extraction treatment versus non-extraction treatment in orthodontics
2. How does horizontal movement of the mandible compare in patients who have four
premolar extraction treatment versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in horizontal mandibular movement
between four premolar extraction treatment versus non-extraction treatment in
orthodontics
H
1
: There is a significant difference in horizontal mandibular movement between
four premolar extraction treatment versus non-extraction treatment in orthodontics
3. How does vertical movement of incisors compare in four premolar extraction treatment
versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in vertical incisal movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
H
1
: There is a significant difference in vertical incisal movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
23
4. How does horizontal movement of incisors compare in four premolar extraction
treatment versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in horizontal incisal movement between
four premolar extraction treatment versus non-extraction treatment in orthodontics
H
1
: There is a significant difference in horizontal incisal movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
5. How does vertical movement of molars compare in four premolar extraction treatment
versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in vertical molar movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
H
1
: There is a significant difference in vertical molar movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
6. How does horizontal movement of molars compare in four premolar extraction
treatment versus non-extraction treatment in orthodontics?
H
0
: There is no significant difference in horizontal molar movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
H
1
: There is a significant difference in horizontal molar movement between four
premolar extraction treatment versus non-extraction treatment in orthodontics
24
CHAPTER 4: MATERIALS AND METHODS
Subjects
Pre-treatment and post-treatment CBCT data was identified on orthodontic
patients that were treated the University of Southern California’s School of Dentistry in
the Department of Orthodontics. All scans were taken on the NewTom QR-DVT 3G in
the Department of Orthodontics between 2005 and 2009. Over 1500 patients were found
and then screened with the following criteria:
Inclusion Criteria
1) Patients have existing initial and final CBCT data of diagnostic quality
2) Patients exhibit a Class 1 molar relationship
3) Female patients at least 15 years of age, Male patients at least 17 years of age
4) Full fixed orthodontic appliances were used
Exclusion Criteria
1) Use of extraoral anchorage
2) Use of temporary anchorage devices
3) Use of vertical control appliances, ie. TPA, Nance
4) Patients with missing molars
5) Shorter than 20 months of treatment time
6) Patients exhibiting cross bites
25
Of the patients screened, 54 patients were identified with these criteria: 24
patients treated with four premolar extractions and 30 patients treated without extractions.
Measurements
Using the OnDemand3D™ software by Cybermed, initial and final cone beam CT
images were viewed for diagnostic quality (fig. 4.1). Patients were re-oriented to
Frankfort-horizontal. Horizontal measurements were made parallel to Frankfort
horizontal and vertical measurements were made perpendicular to Frankfort horizontal.
All measurements were made to 1/100 of a millimeter.
Figure 4.1. Viewing Two 3D images Using OnDemand3D
Patient data was then superimposed on cranial base. (fig. 4.2).
26
Figure 4.2. Superimposing Images on Cranial Base as Identified by the Blue Box
A sagittal cut through the center of the patient was made and viewed (fig. 4.3).
Figure 4.3. Viewing Superimposed Images Using a Sagittal Cut
27
Lack of changes at ANS and palatal plane was checked to verify termination of
growth of each patient. Horizontal and vertical changes of the tip of the maxillary central
incisor were measured (fig. 4.4). Horizontal changes of the mandible were measured at
the most anterior point, pogonion, and vertical changes of the mandible were measured at
the most inferior point, menton.
Figure 4.4. Measuring Changes at the Incisal Tip
28
Measurements of molar movement were made by cutting the image slice through
the center of the posterior arch form (fig.4.5).
Figure 4.5. Making an Image Slice Through the Arch Form
29
Horizontal movement of the right and left molar was measured along the arch at
the height of contour and vertical movement was measured perpendicular to the arch at
the cusp tip (fig.4.6).
Figure 4.6. Measuring Changes in Molar Movement
30
After superimposing the two images at the anterior body of the mandible,
measurements of the lower central incisor and molar were made (fig.4.7).
Figure 4.7. Superimposing Images on the Mandible
31
Horizontal and vertical changes were measured at the incisal tip of the lower
central incisor (fig. 4.8).
Figure 4.8. Measuring Changes at the Incisal Tip of the Lower Incisor
32
Images slice were made down the arch form on both the left and right side to
measure changes in horizontal and vertical molar movement (fig. 4.9).
Figure 4.9. Making an Image Slice Through the Arch Form
Reliability of Measurements
All superimpositions and measurements were made by one examiner. Reliability
was measured using the intraclass correlation coefficient (ICC) on SPSS17. All
measurements showed very high ICC values (closer to a value of 1). The lowest value
was 0.944 for the upper left first molar measurement in the vertical dimension. These
values show a very strong reliability in measurements.
33
Statistical Analysis
Descriptive statistics was calculated for the sample using SPSS17. Mean
movements of the molars were calculated. Independent t-tests were used to determine
movement of teeth and changes in the mandible and significance was measured at
p<0.05. The Pearson correlation coefficient was used to compare and relate the changes
between the teeth and mandible.
34
CHAPTER 5: RESULTS
Initial Comparison of the two groups
The sample consisted of 52 adult patients treated with orthodontics at the
University of Southern California’s School of Dentistry. Initial age of the non-extraction
group was significantly( p<0.05) different than the initial age of the extraction group.
Treatment duration, initial SnGoGn and initial FMA were not significantly different for
both groups (table 1). Selection was normalized for the two groups.
Table 5.1: Initial Comparison of Non-Extraction and Extraction Groups
NE (n=29) EXT (n=23)
p value
mean S.D. mean S.D.
Initial age 25Y 1M 10Y 11M 19Y 7M 3Y 9M 0.016*
Tx duration
(months)
27.45 4.39 29.61 4.51 0.088
Initial SnGoGn 31.03 4.04 33.5 6.24 0.108
Initial FMA 23.95 4.96 26.3 6.01 0.123
( * P<0.05 )
The upper incisor moved significantly (p<0.05) more horizontally and vertically
in the extraction group compared to the non-extraction group (table 2). Both the left and
right upper first molar moved significantly (p<0.05) more horizontally, in a mesial
direction, than the non-extraction group. There was no significant difference (p>0.05) in
vertical movement of the left and right upper first molar between both groups. The lower
incisor moved significantly (p<0.05) more horizontally, or lingually, in the extraction
group than the non-extraction group. There was no significant difference (p>0.05) in the
vertical movement of the lower incisor between the two group. Both left and right lower
35
first molars showed a significant (p<0.05) horizontal movement in a mesial direction in
the extraction group than the non-extraction group. There was a significant (p<0.05)
vertical movement of the lower right first molar in the extraction group compared to the
non-extraction group. However, there was no significant difference (p>0.05) in the lower
left first molar movement between the two groups. The mandible showed no significant
difference (p>0.05) in the horizontal or the vertical dimension between the extraction and
non-extraction groups.
36
Table 5.2: Comparison of Initial Measurements between Non-Extraction and Extraction Groups
NE (n=29) EXT (n=23)
p value
mean S.D. mean S.D.
U1 hor 0.02 1.84 -3.31 3.17 0.000*
U1 ver -0.21 1.10 0.90 1.53 0.005*
U6R hor 0.14 0.92 2.20 1.23 0.000*
U6R ver -0.01 1.22 0.05 0.83 0.839
U6L hor 0.12 1.40 3.22 6.01 0.011*
U6L ver -0.33 0.99 -0.11 1.00 0.438
U6 hor 0.13 0.90 2.71 3.16 0.000*
U6 ver -0.17 0.88 -0.03 0.77 0.566
L1 hor 0.18 2.31 -1.48 2.39 0.015*
L1 ver 0.15 1.13 0.02 1.68 0.756
L6R hor -0.07 0.95 2.76 1.33 0.000*
L6R ver 0.39 0.87 1.20 0.93 0.002*
L6L hor 0.09 0.82 2.27 1.54 0.000*
L6L ver 0.64 0.75 0.94 1.02 0.220
L6 hor 0.01 0.76 2.50 1.06 0.000*
L6 ver 0.50 0.71 1.07 0.86 0.011*
Me hor 0.04 1.20 -0.59 1.28 0.073
Me ver 0.12 1.62 0.80 1.60 0.136
(*p<0.05)
37
Changes in Incisor and Molars Compared to Changes in the Mandible
There was no significant correlation (p>0.05) in mandibular movement in a
horizontal or vertical dimension compared to the initial mandibular angle, measured
either by SnGoGn or FMA (table 3).
Table 5.3: Comparison of Initial Mandibular Angle and Mandibular Changes in Both Groups
Pearson's
correlation
coefficient
p value
Initial SNGoGn Me hor -0.269 0.054
initial FMA Me hor -0.193 0.171
Initial SNGoGn Me ver -0.012 0.933
initial FMA Me ver -0.02 0.889
(*p<0.05)
After combining results from both extraction and non-extraction groups, incisor
changes were compared to changes in mandibular movements (table 4). Horizontal
movement of the upper incisor was correlated to horizontal mandibular movement.
Vertical movement of the upper incisor was also correlated to vertical mandibular
movement.
38
Table 5.4: Comparison of Incisor Movement and Mandibular Changes in Both Groups
Pearson's
correlation
coefficient
p value
U1 hor Me hor 0.326 0.019*
U1 ver Me hor -0.133 0.347
L1 hor Me hor 0.205 0.145
L1 ver Me hor -0.092 0.515
U1 hor Me ver -0.247 0.078
U1 ver Me ver 0.337 0.015*
L1 hor Me ver -0.018 0.901
L1 ver Me ver 0.171 0.225
(*p<0.05)
Molar movements in extraction and non-extraction groups were combined and compared
to mandibular movement (table 5). There was no significant correlation (p>0.05) found in
molar movement and mandibular horizontal movement. A significant correlation
(p<0.05) was found in vertical molar movement of the upper and lower first molars and
vertical movement of the mandible.
39
Table 5.5: Comparison of Molar Movement and Mandibular Changes in Both Groups
Pearson's
correlation
coefficient
p value
UR6 hor Me hor -0.186 0.187
UR6 ver Me hor -0.117 0.409
UL6 hor Me hor -0.130 0.365
UL6 ver Me hor -0.129 0.367
LR6 hor Me hor 0.000 0.997
LR6 ver Me hor -0.048 0.737
LL6 hor Me hor 0.002 0.990
LL6 ver Me hor 0.045 0.751
U6 hor Me hor -0.171 0.225
U6 ver Me hor -0.146 0.300
L6 hor Me hor -0.008 0.954
L6 ver Me hor -0.016 0.909
UR6 hor Me ver 0.130 0.360
UR6 ver Me ver 0.566 0.000*
UL6 hor Me ver -0.020 0.890
UL6 ver Me ver 0.277 0.049*
LR6 hor Me ver 0.044 0.758
LR6 ver Me ver 0.462 0.001*
LL6 hor Me ver -0.110 0.440
LL6 ver Me ver 0.286 0.042*
U6 hor Me ver 0.033 0.819
U6 ver Me ver 0.515 0.000*
L6 hor Me ver -0.016 0.908
L6 ver Me ver 0.439 0.001*
(*p<0.05)
40
There was a significant correlation (p<0.05) between the mandibular horizontal
and vertical movements (table 6). There was also a significant correlation (p<0.05)
between the upper and lower first molar horizontal as well as vertical movements.
Table 5.6: Comparison of Horizontal and Vertical Changes in the Mandible and Molars
Pearson's
correlation
coefficient
p value
Me hor Me ver -0.317 0.022*
U6 hor L6 hor 0.479 0.000*
U6 ver L6 ver 0.338 0.014*
(*p<0.05)
There was no significant correlation (p<0.05) between the horizontal and vertical
movement of the molars (Table 7).
Table 5.7: Comparison of Molar Horizontal and Vertical Movement
Pearson's
correlation
coefficient
p value
U6L hor U6L ver -0.099 0.484
U6R hor U6R ver 0.032 0.822
U6 hor U6 ver 0.050 0.725
L6L hor L6L ver 0.151 0.291
L6R hor L6R ver 0.233 0.097
L6 hor L6 ver 0.229 0.102
(p<0.05)
41
CHAPTER 6: DISCUSSION
Previous studies have been done to examine effect of extraction treatment on
facial balance and esthetics. While some practitioners consider extraction of teeth to
allow greater control in the vertical dimension, multiple studies have shown there is no
difference. However, most studies have been limited to measuring changes from
orthodontic treatment using lateral cephalogram measurements and superimpositions.
As technology has advanced to using 3-dimensional imaging in orthodontics, we
are able to verify previous studies that have been done. The 3D Cone Beam CT allows
the clinician to manipulate the images after the image has been taken and view a specific
area of the patient’s craniofacial complex from any direction. Using a new computer
program, OnDemand3D™, mathematical models were used to accurately superimpose
the 3D images. This allowed us to eliminate the majority of human error that is inherent
in current methods of superimpositions.
Many of the previous studies were limited to using a growing sample size which
may contribute to an overall increase in vertical dimension
[10]
. In this study, treatment
duration and initial mandibular plane angle were normalized. Although the initial
treatment ages were significantly different (p<0.05), an adult sample group was used to
eliminate any residual growth effects. Cessation of growth was also verified by
superimposing on cranial base and noting no change at ANS.
As expected, upper incisor movement was significantly different (p<0.05)
between the extraction and non-extraction groups. There was more horizontal, or lingual,
movement of the upper incisors found in the extraction group. This result is expected due
42
to space closure usually by both mesialization of the posterior segment and retraction of
the anterior segment. The lower incisor also showed more lingual movement in the
extraction group for the same reason stated above. Upper and lower molars showed a
greater horizontal, or mesial, movement in the extraction group compared to the non-
extraction group. This movement is also expected in order to close the extraction spaces
during treatment.
The upper molars did not show any significant different (p>0.05) movement in
the vertical dimension during treatment in the extraction group. The lower right first
molar showed more extrusion in the extraction group than the non-extraction group, but
the lower left first molar did not show any difference. However, on average, the lower
molars did demonstrate an increase in vertical movement during extraction treatment than
non-extraction treatment as shown in previous studies
[10,11,28.29].
Shudy found that the
downward movement of maxillary molars was most responsible for establishing facial
height during growth
[4]
. However, our results demonstrate that vertical movement of
maxillary molars is more easily controlled during orthodontic treatment than the vertical
movement of mandibular molars.
There was no significant difference in mandibular movement in the horizontal or
vertical dimension between the extraction and non-extraction groups. This result
corroborates the studies that stated there was no ‘wedge effect’ in orthodontic treatment
by extracting premolars. While there was a significant mesialization of the molars during
extraction treatment, we have determined that the simultaneous vertical movement of the
molars negates any closing effect on the mandible. While insignificant (p>0.05), there
43
appears to be a tendency towards an opening of the bite during orthodontic treatment. On
average, the extraction group tended to open the vertical dimension more than in the non-
extraction group. Since our sample size consisted of non-growing adult patients, there
were no residual growth effects that could be attributed to these tendencies.
Our study showed that there was no correlation between initial mandibular plane
angle and mandibular plane angle changes during treatment. However, these results do
not imply that initial mandibular plane angle does not have an effect on facial changes
during orthodontic treatment. Studies have shown that patients with hyperdivergent
profiles tend to have an increase in vertical facial dimension during orthodontic
treatment
[93]
. All the patients included in this study were non-growing adults with an
average mandibular plane angle. The majority of orthodontic treatment is initiated during
adolescence when growth can possibly be modified or is still changing.
There was a correlation between incisor movement and mandibular movement.
As the upper incisor extruded, there was a tendency towards opening of the mandible.
This effect may be attributed to changes originating at the molars. A consistent
correlation was found between the vertical control of the upper and lower first molars and
the vertical movement of the mandible. With an increase in vertical extrusion of the
molars, there was an increase in the vertical facial dimension. This may explain the
previous correlation between upper anterior extrusion and increase in vertical dimension.
As molars extrude and the mandible opens, overbite is decreased. In order to establish an
ideal incisor relationship and correct overbite, vertical positioning of the incisor will also
extrude to compensate for the increased vertical dimension of the face. Control of the
44
anterior segment during alignment or space closure is important in controlling the facial
vertical dimension.
The horizontal movement of the upper and lower first molars was correlated, as
expected in order to maintain the class I molar relationship. Also, the amount of vertical
extrusion of the upper and lower molars was found to be correlated. There was no
relationship found, however, between the amount of vertical extrusion and horizontal
movement of the molars. Maintaining vertical control of molars during space closure
continues to be a challenge to orthodontists. There is currently no predictable amount of
mandibular opening during orthodontic treatment but clinicians need to be continually
mindful of the vertical effects of their treatment mechanics.
45
CHAPTER 7: ASSUMPTIONS
1. The patient population treated at the University of Southern California is
representative of the Los Angeles population
2. The measurements were accurate and reproducible
3. The NewTom’s accuracy is reliable and any distortion is clinically insignificant
46
CHAPTER 8: LIMITATIONS
1) The NewTom was introduced into the USCSD’s Orthodontic Department in 2005 and
then replaced by a traditional x-ray machine in 2009. The number of patients who
were able to take initial and final 3D scans on the NewTom and fit the inclusion
criteria was greatly limited.
2) The majority of the patient population treated at the University of Southern
California’s School of Dentistry is teenagers. This study excluded patients who were
still growing and therefore, excluded a vast number of these patients. The number of
older orthodontic patients who are treated with four premolar extractions is also
limited due to the tendency towards non-extraction treatment in adults.
3) The NewTom’s resolution is 0.3mm, which limits the accuracy of the measurements.
4) There is no untreated control group in this study.
47
CHAPTER 9: CONCLUSIONS
1) There was a significantly greater horizontal movement of the incisors and molars
in the extraction group than the non-extraction group.
2) The lower molars showed a significantly greater extrusive component in the
extraction group than the non-extraction group.
3) There was no difference in movement of the mandible during extraction or non-
extraction treatment.
a. There is no wedge effect due to extraction of four premolars.
b. There may even be a tendency for opening of the bite due to orthodontic
treatment.
4) Regardless of the type of orthodontic treatment, extrusion of the upper anterior
teeth and both molar teeth was related to an increase in vertical facial dimension.
a. Vertical control is necessary in orthodontic treatment to maintain vertical
facial dimension.
48
5) Fully automated 3D cone beam CT superimpositions are reliable for measuring
changes due to growth and/or orthodontic treatment.
a. Errors due to patient positioning and landmark overlap can be eliminated.
b. Errors due to landmark identification can be reduced to the points
necessary for measuring changes, not for superimposing the images.
49
BIBLIOGRAPHY
45. Adenwalla ST, Kronman JH, Attarzadeh F. Porion and condyle as cephalometric
landmarks--an error study. Am J Orthod Dentofacial Orthop. 1988;94(5):411-5
39. Baumrind S, Frantz RC. The reliability of head film measurement. 1. Landmark
Identification. Am J Orthod. 1971;60:111–127.
85. Baumrind S, Miller DM, Molthen R. The reliability of head film measurements. 3.
Tracing superimposition. Am J Orthod 1976;70:618-644.
81. Bjork A. Variations on the growth pattern of the human mandible. A longitudinal
radiographic study by the implant method, J Dent Res 1963;42 (suppl.1):400-11.
13. Bjork A, Skieller V. Facial development and tooth eruption: An implant study at the
age of puberty. Am J Orthod Dentofacial Orthop 1972;62:339-383
78. Bjork A, Skieller V. Roentgencephalometric growth analysis of the maxilla. Trans
Eur Orthod Soc. 1977;7:209-33
30. Broadbent BH. Bolton standards and technique in orthodontic practice. Angle Othod.
1937;7:209-33.
71. Broadbent BH. The face of the normal child. Angle Orthod. 1937;7:183-208
62. Brooks S. Radiation doses of common dental radiographic examinations: A Review.
Acta Stomatol Croat. 2008;42(3):207-217
65. Brown AA, Scarfe WC, Scheetz JP, Silveira AM, Farman AG. Linear accuracy of
Cone Beam CT derived 3D images. Angle Orthod. 2009;79:150-157.
88. Cevidanes LH, Styner MA, Proffit WR. Image analysis and superimposition of 3-
dimensional cone-beam computed tomography models. Am J of Orthod & Dentofacial
Ortho 2006;129:611-618
92. Cevidanes LH, Heymann G, Cornelis MA, DeClerck HJ, Tulloch JF. Superimposition
of 3-dimensional cone-beam computed tomography models of growing patients. Am J of
Orthod Dentofac Orthop 2009;136:94-99
90. Cevidanes LH, Bailey LJ, Tucker GR Jr, Styner MA, Mol A, Phillips CL, et al.
Superimposition of 3D cone-beam CT models of orthognathic surgery patients.
Dentomaxillofac Radiol 2005; 34:369-75.
50
46. Chan CK, Tng TH, Hägg U, Cooke MS. Effects of cephalometric landmark validity
on incisor angulation. Am J Orthod Dentofac Orthop. 1994;106:487-95.
28. Chua AL, Lim JY, Lubit EC. The effects of extraction versus nonextraction
orthodontic treatment on the growth of the lower anterior face height. Am J Orthod
Dentofac Orthop. 1993;104:361–368.
83. Cook AH. The variability and reliability of two maxillary and mandibular
superimposition techniques. Part II. Am J Orthod Denofac Orthop 1994;106:463-71.
82. Cook PA, Gravely JF. Tracing error with Bjork’s mandibular structures. Angle
Orthod 1988;58:169-178.
9. Cusimano C, McLaughlin RP, Zernik JH. Effects of first bicuspid extractions on facial
height in high-angle cases. J Clin Orthod. 1993;27:594–598.
57. Dawood A, Patel S, Brown J. Cone beam CT in dental practice. British dental journal
2009;207:23-28.
18. de Castro N. Second-premolar extraction in clinical practice. Am J Orthod.
1974;65:115–137.
15. Dewel BF. Extraction in orthodontics: premises and prerequisites. Angle Orthod.
1973;43:65–87.
80. Doppel DM, Damon WM, Joondeph DR, Little RM. An investigation of maxillary
superimposition techniques using metallic implants. Am J of Orthod Dentofac Orthop
1994;105:161-168.
73. Downs, WB: The role of cephalometrics in orthodontic case analysis and diagnosis.
Am J of Orthod 1960;38:162-183.
36. Downs WB. Variations in facial relationships: their significance in treatment and
prognosis. Am J Orthod. 1948;38:812-40.
51. Duarte HEM, Vieck R, Siqueira DF, Angelieri F, Bommarito S, Dalben G and
Sannomiya EK. Effect of image compression of digital lateral cephalograms on the
reproducibility of cephalometric points. Dentomaxillofacial Radiology 2009;38:393–400.
24. Garlington M, Logan LR. Vertical changes in high mandibular plane cases following
enucleation of second premolars. Angle Orthod. 1990;60:263–267.
51
5. Gianelly AA, Cozzani M, Boffa J. Condylar position and maxillary first premolar
extraction. Am J Orthod Dentofacial Orthop. 1991;99:473–476.
76. Gliddon MJ, Xia JJ, Gateno J, Wong HT, Lasky RE, Teichgraeber JF, Jia X,
Liebschner MA, Lemoine JJ. The accuracy of cephalometric tracing superimposition.
J Oral Maxillofac Surg. 2006 Feb;64(2):194-202.
56. Govila S, Gundappa M. Cone beam computed tomography - an overview. J Conserv
Dent 2007;10:53-58.
58. Grauer D, Cevidanes L, Proffit WR. Working with DICOM craniofacial images. Am
J Orthod Dentofac Orthop 2009;136:460-70.
87. Hajeer MJ, Ayoub AF, Millett DT, Bock M, Siebert JP. Three-dimensional imaging
in orthognathic surgery: The clinical application of a new method. Int J Adult Orthod
Orthognath Surg 2002;17:318–330.
85. Hill DLG, Hawkes DJ, Gleeson MJ, et al. Accurate frameless registration of MR and
CY images of the head: Applications in planning surgery and radiation therapy.
Radiology 1994;191:447-454.
33. E.H. Hixon, The norm concept and cephalometrics. Am J Orthod 1956;42:898–906.
59. Kau CH, Bozic M,English J, Lee R, Bussa H, Ellis R. Cone-beam computed
tomography of the maxillofacial region – an update. Int J Med Robotics Comput Assist
Surg 2009;5:366-380.
86. Kawamata A, Fujishita M, Kuniteru N, Kanematu N, Niwa K, Langlais R. Three-
dimensional computed tomography evaluation of postsurgical condylar displacement
after mandibular osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;
85: 371–376.
19. Ketterhagen DH. First premolar or second premolar extractions: formula or clinical
judgment? Angle Orthod 1979;49:190–198.
29. Kim, TK et al. First or second premolar extraction effects on facial vertical
dimension. Angle Orthod 2005;75:177-182
10. Kocadereli I. The effect of first premolar extraction on vertical dimension. Am J
Orthod Dentofacial Orthop. 1999;116:41–45.
52
23. Kojima K, Endo T, Shimooka S. Effects of maxillary second molar extraction on
dentofacial morphology before and after anterior open-bite treatment: a cephalometric
study. Odontology 2009;97:43-50.
70. J. Kragskov, C. Bosch, C. Gyldensted and S. Sindet-Pedersen, Comparison of the
reliability of craniofacial anatomic landmarks based on cephalometric radiographs and
three-dimensional CT scans, Cleft Palate Craniofac J 1997;34:111–116.
49. Kumar V, Ludlow JB, Mol A, Cevidanes L. Comparison of conventional and cone
beam CT synthesized cephalograms. Dentomaxillofac Radiol. 2007;36:263-9.
11. Kumari M, Fida M. Vertical facial and dental arch dimensional changes in extraction
vs. non-extraction orthodontic treatment. J of the College of physicians and Surgeons
Pakistan 2010:20(1):17-21.
69. C.A. Lascala, J. Panella and M.M. Marques, Analysis of the accuracy of linear
measurements obtained by cone beam computed tomography (CBCT-NewTom),
Dentomaxillofac Radiol 2004;33:291–294.
26. Levy PH. Clinical implications of mandibular repositioning and the concept of an
alterable centric relation. Int J Orthod 1979;17:6–25.
60. Liedke GS, Dias da Silveira HE, Dias da Silveira HL, Dutra V, Poli de Figueiredo JA.
Influence of voxel size in the diagnostic ability of cone beam tomography to evaluate
simulated external root resorption. JOE 2009;35:233-235.
17. Logan LR. Second premolar extraction in Class I and Class II. Am J Orthod
1973;63:115–147.
63. Lou L, Lagravere MO, Compton S, Major PW and Flores-Mir C. Accuracy of
measurements and reliability of landmark identification with computed tomography (CT)
techniques in the maxillofacial area: a systematic review, Oral Surg Oral Med Oral Pathol
Oral Radiol Endod 2007;104:402–411.
48. Ludlow JB etal. Precision of cephalometric landmark identification: Cone-beam
computed tomography vs conventional cephalometric views. Am J Orthod Dentofac
Orthop 2009;136:312.e1-312.e10.
6. Luecke PE III, Johnston LE Jr. The effect of maxillary first premolar extraction and
incisor retraction on mandibular position: testing the central dogma of ‘‘functional
orthodontics.’’ Am J Orthod Dentofacial Orthop. 1992;101:4–12.
53
7. Luppanapornlarp S, Johnston LE Jr. The effects of premolar-extraction: a long-term
comparison of outcomes in ‘‘clear-cut’’ extraction and nonextraction Class II patients.
Angle Orthod 1993;63:257–272.
50. Macrì V, Wenzel A. Reliability of landmark recording on film and digital lateral
cephalograms. European Journal of Orthodontics 1993;15:137–148.
89. Maes F, Collignon A, Vandermeulen D, Marchal G, Suetens P. Multimodality image
registration by maximation of mutual information. IEEE Transactions on Medical
Imaging. 1997;16:187-198.
67. Mah JK, Danforth RA, Bumann A, Hatcher D. Radiation absorbed in maxillofacial
imaging with a new dental computed tomography device. Oral Surg Oral Med Oral
Pathol Oral Radiol Endod. 2003;96:508-13.
68. R. Marmulla, R. Wörtche, J. Mühling and S. Hassfeld. Geometric accuracy of the
NewTom 9000 Cone Beam CT, Dentomaxillofac Radiol 2005;34:28–31.
8. McLaughlin RP, Bennett JC. The extraction-nonextraction dilemma as it relates to
TMD. Angle Orthod 1995;65:175–186.
12. Midtgard J, Bjork G, Linder-Aronson S. Reproducibility of cephalometric landmarks
and errors of measurements of cephalometric cranial distances. Angle Orthod
1974;44:56-61.
77. Moore AW. Orthodontic treatment factors in Class II malocclusion. Am J Orthod.
1959;45:323-52.
43. C.F.A. Moorrees, Normal variation and its bearing on the use of cephalometric
radiographs in orthodontic diagnosis. Am J Orthod 1953;39:942–950.
14. Nance H. N. The removal of second premolars in orthodontic treatment. Am J
Orthod. 1949;35:685–695.
79. Nielsen IL. Maxillary superimposition: a comparison of three methods for
cephalometric evaluation of growth and treatment change. Am J Orthod Dentofac
Orthop.1989;95:422–431.
74. Pancherz H, Hansen K: The nasion-sella reference line in cephalometry: A
methodologic study. Am J Orthod 1984;86:427.
31. Parker JH. An analysis of cephalometry. Am J Orthod 1953;39:915-931.
54
64. Periago DR, Scarfe WC, Moshiri M, Scheetz J, Silveira AM, Farman AG. Linear
accuracy and reliability of cone beam ct derived 3-dimensional images constructed using
an orthodontic volumetric rendering program. Angle Orthod 2008;78;387-395.
47. Perillo M, Beideman R, Shofer F, Jacobsson-Hunt U, Higgins-Barber K, Laster L,
Ghafari J. Effect of landmark identification on cephalometric measurements: guidelines
for cephalometric analyses. Clin Orthod Res. 2000;3:29-36.
1. Proffit, W.R., H.W. Fields, and D.M. Sarver, Contemporary orthodontics. 4th ed.
2007, St. Louis, Mo.: Mosby Elsevier.
44. A. Richardson, An investigation into the reproducibility of some points, planes, and
lines used in cephalometric analysis. Am J Orthod 52 (1966), pp. 637–651
72. Ricketts RM. A four step method to distinguish orthodontic changes from natural
growth. J Clin Orthod. 1975;4:208–228.
52. Roden-Johnson D, English J, Gallerano R. Comparison of hand-traced and
computerized cephalograms: Landmark identification, measurement, and superimposition
accuracy. Am J of Orthod Dentofac Orthop. 2008;133:556-564.
91. Rueckert D, Sonoda LI, Hayes C, Hill DLG, Leach MO, Hawkes DJ. Nonrigid
registration using free-form deformations: application to breast MR images. IEEE Trans
Med Imaging 1999;18:712-21.
34. Salzmann JA. Limitations of roentgenographic cephalometrics. Am J Orthod
Dentofac Orthop 1964:50:169-188.
22. Sassouni V, Nanda S. Analysis of dentofacial vertical proportions. Am J Orthod
1964;50:801–823.
61. William C. Scarfe, Allan G. Farman, Predag Sukovic. Clinical applications of cone-
beam computed tomography in dental practice. J Can Dent Assoc 2006;72:75–80.
4. Schudy FF. The control of vertical overbite in clinical orthodontics. Angle Orthod
1968;38:19–39.
3. Schudy FF. The rotation of the mandible resulting from growth: its implication in
orthodontic treatment. Angle Orthod 1965;35:36–50.
2. Schudy FF. Vertical growth versus anteroposterior growth as related to function and
treatment. Angle Orthod 1964;34:75–93.
55
16. Schwab DT. The borderline patient and tooth removal. Am J Orthod 1971;59:126–
145.
T. Sekiguchi and B.S. Savara, Variability of cephalometric landmarks used for face
growth studies. Am J Orthod 1972;61: 603–618.
84. Springate SD, Jones AG. The validity of two methods of mandibular superimposition:
A comparison with tantalum implants. Am J Orthod Dentofac Orthop 1998;113:263-270.
27. Staggers JA. Vertical changes following first premolar extractions. Am J Orthod
Dentofacial Orthop. 1994;105:19–24.
32. Steiner CC. Cephalometrics for you and me. Am J Orthod 1953:39;729.
37. Steiner CC. Cephalometrics in clinical practice. Angle Orthod 1959:29;8.
35. Steiner CC. The use of cephalometrics as an aid to planning and assessing orthodontic
treatment. Am J Orthod 1960;46:721–735.
75. Steur I. The cranial base for superimposition of lateral cephalometric radiographs.
Am J Orthod 1972;61:493-500.
20. Steyn CL, du Preez RJ, Harris AM. Differential premolar extractions. Am J Orthod
Dentofac Orthop 1997;112:480–486.
66. Stratemann SA, Huang JC, Maki K, Miller AJ, Hatcher DC. Comparison of cone
beam computed tomography imaging with physical measures. Denomaxillofacial
Radiolog. 2008;37:80-93.
54. Sukovic P. Cone beam computed tomography in craniofacial imaging. Orthod
Craniofacial Res 2003;6:31–36.
93. Taner-Sarisoy L, Darendeliler N. The influence of extraction orthodontic treatment on
craniofacial structures: evaluation according to two different factors. Am J Orthod
Dentofac Orthop 1999;115:508–514.
40. Trpkova B, Major P, Prasad N. et al. Cephalometric landmarks identification and
reproducibility: A meta analysis, Am J Orthod Dentofac Orthop 1997;112:165-170.
25. Tulley WJ. The role of extractions in orthodontic treatment. Br Dent J.
1959;107:199–205.
38. Tweed CH. The frank-mandibular-incisal angle (FMIA) in orthodontic diagnosis,
treatment planning and prognosis. Angle Ortho 1954;24:121.
56
53. Uysal T, Baysal A and Yagci A. Evaluation of speed, repeatability, and
reproducibility of digital radiography with manual versus computer-assisted
cephalometric analyses. European Journal of Orthodontics 2009;31:523–528.
42. F.P.G.M. van der Linden, A study of roentgenocephalometric bony landmarks. Am J
Orthod 1971;59:111–125.
21. Yagi M, Ohno H, Takada K. Computational formulation of orthodontic tooth-
extraction decisions. Angle Orthod. 2009:29:892-898.
55. Zoller JE, Neugebauer J. Cone-beam volumetric imaging in dental, oral and
maxillofacial medicine: fundamentals, diagnostics and treatment planning. London :
Quintessence, 2008
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Asset Metadata
Creator
Yoo, Jenny
(author)
Core Title
Mandibular plane angle changes with or without premolar extraction treatment in adult orthodontics measured using 3-D cone beam technology
School
School of Dentistry
Degree
Master of Science
Degree Program
Craniofacial Biology
Degree Conferral Date
2010-05
Publication Date
05/07/2010
Defense Date
03/25/2010
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(original),
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Tag
3-D cone beam technology,mandibular plane angle,OAI-PMH Harvest,premolar extraction,wedge effect
Language
English
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Moon, Holly (
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), Payne, Michael (
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), Sameshima, Glenn T. (
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)
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jmyoo52@gmail.com,jmyoo52@hotmail.com
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Yoo, Jenny
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University of Southern California Dissertations and Theses
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Tags
3-D cone beam technology
mandibular plane angle
premolar extraction
wedge effect