Download evaluation of immediate soft tissue effects of rapid maxillary

EVALUATION OF IMMEDIATE SOFT TISSUE EFFECTS
OF RAPID MAXILLARY EXPANSION USING
THREE-DIMENSIONAL IMAGING.
Daniel Robert Adams D.M.D.
An Abstract Presented to the Faculty of the Graduate School
of Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2009
Abstract
Introduction:
The development and increased use of cone
beam computed tomography (CBCT) in orthodontic treatment
provides a means to measure changes on the soft tissue that
are not on the facial midline.
Purpose:
The purpose of
this study is to demonstrate a reliable method of measuring
soft tissue changes associated with rapid maxillary
expansion (RME) treatment to quantify immediate soft tissue
changes in the transverse and anterior-posterior planes
following RME in growing patients, using CBCT images.
Materials and Methods:
A sample of twenty-three
consecutively treated patients, who had been treated by RME
was utilized for this study.
Patients were scanned using
CBCT prior to placement of the rapid maxillary expander
(T0), then immediately following full activation of the
appliance (T1).
Defined landmarks were then located on the
pre- and post-treatment orientated images.
Change in
landmark position from pre- to post-treatment was then
measured.
Results:
This sample had a mean expansion of
5.2mm of the appliance. Significant transverse expansion
was measured on most soft tissue landmark locations.
All
the measures made showed significant change in the lip
position with a lengthening of the vertical dimension of
1
the upper lip, and a generalized decrease in thickness of
both the upper and lower lips.
Conclusions:
Significant
changes in the soft tissue do occur with RME treatment.
There is a transverse widening of the midface, and a
thinning of the lips.
2
EVALUATION OF IMMEDIATE SOFT TISSUE EFFECTS
OF RAPID MAXILLARY EXPANSION USING
THREE-DIMENSIONAL IMAGING.
Daniel Robert Adams D.M.D.
A Thesis Presented to the Faculty of the Graduate School
of Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2009
COMMITTEE IN CHARGE OF CANDIDACY:
Assistant Professor Ki Beom Kim,
Chairperson and Advisor
Professor Eustaquio A. Araujo
Professor Rolf G. Behrents
i
DEDICATION
I dedicate this project to my loving and supportive
family.
I am thankful for the support and encouragement
from my wonderful wife Chelsey.
Also, for my three
children Koston, Jak, and Penny who keep me from getting
lazy.
I also dedicate this to my parents who have never
ceased to encourage and support me.
ii
ACKNOWLEDGEMENTS
I would like to acknowledge the following individuals for
their contributions to this thesis:
Dr. Kim for his advice and guidance during this
endeavor,
Dr. Behrents for helping me with organization and
sharing his knowledge and insight
Dr. Araujo for making time for me in his already busy
schedule,
Dr. Joe Mayes for providing access to my sample and
information on treatment details
Heidi Israel for assistance in statistical analysis
iii
TABLE OF CONTENTS
List of Tables............................................vi
List of Figures..........................................vii
CHAPTER 1:
INTRODUCTION...................................1
CHAPTER 2: REVIEW OF THE LITERATURE
Growth and Development of the Maxillary Complex.......5
Etiology of Maxillary Deficiency.................6
Rapid Maxillary Expansion.............................8
The Haas Appliance...............................9
The Hyrax Appliance.............................10
Timing of Treatment.............................10
Effects of Rapid Maxillary Expansion.................12
Skeletal Effects................................12
Dental Effects..................................14
Soft Tissue Effects.............................16
Two-Dimensional Soft Tissue Analysis.................18
Photographic Images.............................19
Lateral Cephalograms............................20
Posteroanterior Cephalograms....................21
Three-Dimensional Soft Tissue Analysis...............22
Physical Measurement............................23
Laser Facial Scanning...........................24
Digital Photogrammetry..........................25
Computed Tomography.............................26
Cone-Beam Computed Tomography...................28
Summary and Statement of Thesis......................29
References...........................................31
CHAPTER 3: JOURNAL ARTICLE
Abstract.............................................38
Introduction.........................................40
Materials and Methods................................42
Landmark Assessment.............................46
Statistics......................................54
Results..............................................55
Discussion...........................................60
Transverse Change...............................62
Anterior-Posterior Change.......................65
Change in Lips..................................66
iv
Conclusions..........................................68
References...........................................69
Vita Auctoris.............................................72
v
LIST OF TABLES
Table 3.1:
Definitions of anatomic landmarks located.....50
Table 3.2:
Cronbach’s alpha for intraclass correlation
coefficient of landmark identification........57
Table 3.3:
Transverse change, descriptive statistics.....58
Table 3.4:
Anteroposterior change, descriptive
statistics....................................58
Table 3.5:
Direct measures, descriptive statistics.......59
Table 3.6:
Transverse change, paired t-test results......59
Table 3.7:
Anteroposterior change, paired
t-test results................................60
Table 3.8:
Direct measures, paired t-test results........60
vi
LIST OF FIGURES
Figure 3.1:
Model of Palatal Expander...................43
Figure 3.2:
The standard orientation....................45
Figure 3.3:
Frontal view with soft tissue landmarks.....47
Figure 3.4:
Soft tissue nasion..........................48
Figure 3.5:
Bridge of nose (BN).........................49
Figure 3.6:
Measurement of upper lip thickness..........52
Figure 3.7:
Measurements of the lower lip thickness.....53
Figure 3.8:
Measure for length of upper lip.............54
Figure 3.9:
Transverse change...........................64
Figure 3.10:
Anteroposterior change......................66
vii
CHAPTER 1:
INTRODUCTION
Facial esthetic considerations are vital in
orthodontic treatment planning.
One of the goals of
orthodontics is to maintain or improve facial balance and
esthetics.1
Thus, it is important for orthodontists to
understand the full impact that treatment will have on the
facial esthetics of their patients.
Rapid maxillary expansion is a treatment that has been
described in the orthodontic literature since 1860.2
It is
often used during the mixed dentition as a treatment for
posterior crossbites and crowding of the dentition.3
It has
been reported that 21% of children have maxillary
transverse deficiency resulting in some form of crossbite.4
The hard tissue changes that take place as the result of
RME have been well documented in the orthodontic
literature.3,5-12
Most studies show that transverse
expansion seen with rapid maxillary expansion (RME) is 50%
skeletal and 50% dental.1
Effects include buccal tipping of
the molars and premolars5 and a downward and forward
displacement of the maxilla.12,13
Rapid maxillary expansion
has been shown to produce an increase in arch width and
perimeter to allow for correction of posterior crossbite
and provide space to alleviate crowding of the dentition.5,14
1
Compared with the large amount of information
available regarding the hard tissue changes associated with
RME, there is a relatively small amount of information
available regarding soft tissue changes.
Studies that are
available largely neglect structures lateral to the
midline.
Factors such as soft tissue thickness and the
elastic nature of soft tissues create changes that are not
necessarily at a one to one ratio with changes taking place
in the underlying hard tissue.15
Studies of soft tissue change involving facial regions
lateral to the midline are limited partly because these
structures are not identifiable on traditional twodimensional cephalograms.16
Also it is difficult to
repeatedly identify soft tissue landmarks due to the nature
of these tissues.17,18
Karaman et al. evaluated soft tissue
changes induced by RME.
They used lateral cephalograms
taken on 20 patients pre- and post-RME treatment.
They
found that the nose tip and soft tissue A point followed
the anterior movements of the maxilla and maxillary
incisors.19
One attempt to measure regions lateral to the midline
was made by Berger et al.
They measured facial changes
based on measurements made from two dimensional digital
photos and found changes in several areas.20
2
Using this
method they documented some changes that take place in the
soft tissue when viewed from a frontal view.
With more information becoming available through the
more widespread use of cone beam computed tomography (CBCT)
in orthodontics, there is greater potential to study the
effects orthodontic treatment has on the soft tissue.
Progress in software development has allowed for more
manipulation and better viewing of the CBCT images, which
allows for more accurate and repeatable collection of
information.21
Cone beam computed tomography provides high
resolution three-dimensional imaging that contains
information of both hard and soft tissue, with the added
benefit of being less expensive and delivering less
radiation to the patient than traditional tomography.22,23
The purpose of this study is to to quantify the
immediate soft tissue changes in the transverse and
anterior-posterior planes following RME in growing
patients, using CBCT images.
3
CHAPTER 2: REVIEW OF THE LITERATURE
This review of the literature is divided into five
parts. The first section will outline the growth and
development of the maxillary complex.
It will also include
some known etiologies of maxillary constriction that may
lead to a need for rapid maxillary expansion.
Knowledge of
growth and development of the maxilla helps in describing
the need, and mechanism of action for rapid maxillary
expansion. The second section of this review will describe
the process of rapid maxillary expansion.
This will
include a description of the biomechanics of the procedure
as well as the appliance used on the subjects in this
study.
The third section will look at previous findings
regarding the changes associated with rapid maxillary
expansion.
Skeletal, dental, and soft tissue changes have
all been studied to some extent and this section will look
at some of the findings describing changes in these areas.
The forth section is intended to give a historical
perspective on how soft tissue have been measured twodimensionally, most notably utilizing lateral and
posteroanterior cephalograms, and photographs. More
recently, technological advances have provided
orthodontists with the opportunity to analyze these changes
4
with three-dimensional imaging techniques. The advantages
and disadvantages of these techniques will be discussed in
the final section, with emphasis placed on the most
historically popular methods of measurement.
Growth and Development of the Maxillary Complex
The two maxillary bones form by intramembraneous bone
formation, meaning bones form by apposition of bone at the
sutures.
The bones also develop through surface
remodeling.
Implant studies carried out by Björk helped to
show the direction in which the maxillary bones develop.24
These implant studies showed that growth of the maxilla and
midface occurs by apposition of bone on the posterior of
the maxillae towards the palatine bone and at the maxillary
tuberosities.24,25
During development of the midface, the
prenatal cartilage of the nasal septum is ossified to
become the vomer and portions of the ethmoid bones leaving
some cartilage remaining in the adult nasal septum.25
Björk also showed that vertical growth of the maxilla
occurs by apposition of bone in the floor of the orbit and
at the oral surface of the hard palate.24,25
Vertical growth
during the ages of 6-18 years has been shown to increase
9 mm (19-26%) in females and by 15 mm (32-40%) in males.26
5
Information on growth in the transverse plane is
limited. Research as recent as 1971 believed that growth in
the transverse dimension was completed by the age of 3
years.27
However many have shown that growth of the maxilla
continues at the midpalatal suture beyond puberty.10,25,28
Korn and Baumrind showed through implant studies that
during and after peak velocity growth, transverse
development does still occur.29
Sutural growth at the
midpalatal suture is thought to occur until the age of 1315 years, and slows and discontinues as the maxillary bones
begin to fuse.30
Etiology of Transverse Maxillary Deficiency
Maxillary deficiency is often clinically recognized by
the presence of either a unilateral or bilateral crossbite.
Maxillary deficiency in the transverse plane can occur in
patients with otherwise normal jaw proportions.
However,
when it occurs in a skeletal Class II patient it is often
accompanied by excessive vertical development, and in a
skeletal Class III patient it is often part of a
generalized deficiency of the entire maxilla.1
A study
conducted by the U.S. Public Health department showed a
prevalence maxillary constriction in 9.4% of the general
6
population in subjects from the age of 8-50 years.31
Maxillary constriction may be due to genetic or
environmental factors, or a combination of both.
Many
genetic syndromes are associated with maxillary
constriction including Marfan's, Crouzon, and
velocardiofacial syndrome.
Environmental factors can play a role in maxillary
constriction.
Harvold, Chierici, and Vargervik showed that
respiration may affect the dentition.
They conducted
research using rhesus monkeys that involved altering tongue
positions to simulate the positions of a mouth breather, as
well as completely blocking the nasal airway causing the
monkeys to only breathe through their mouths.
This caused
the animals to have an altered tongue posture, a lowered
mandible, constricted dental arches, and less transverse
development of the Maxilla.32-34
Maxillary constriction is often manifested in mouth by
the presence of a posterior crossbite.
This crossbite can
be unilateral or bilateral depending on severity of the
maxillary deficiency and the other proportions of the bones
of the facial complex.
7
Rapid Maxillary Expansion
The first appearance it the literature of rapid
maxillary expansion (RME) was in 1860.2
Angell designed an
appliance to separate the maxillary bones at the midpalatal
suture before the suture fused.
He described this
treatment as useful in patients that did not have room to
accommodate the maxillary canines.
This treatment is commonly used today in patients with
a constricted maxilla, resulting in crossbite or crowding
of the dentition.3
There are currently many methods of
maxillary expansion.
In order to achieve skeletal
expansion, force needs to be placed across the midpalatal
suture.
This can be accomplished by appliances that
utilize a screw, springs, or wires.
Appliances may be
fixed or removable, connected to TADs or the dentition, as
well banded or bonded to the dentition.
expansion is variable.
The speed of
Rapid expansion in often defined as
0.5 mm or more per day; semi-rapid is approximately 0.25 mm
per day, while slow expansion is usually about 1 mm per
week.1
Rapid maxillary expansion is most often done using a
jackscrew that is activated 0.5 mm-1 mm/day.
can range from 10-20 lbs.35
Force levels
Radiographs can confirm the
8
opening of the midpalatal suture.
In addition, opening of
the suture can often be observed clinically by a diastema
opening between the maxillary incisors.
Active expansion
can continue for 2-3 weeks depending on the desired amount
of expansion.
The appliance then is left in place for a
period of 3-6 months as new bone fills the suture.1
Orthopedic movement in RME occurs when the forces
applied to the dentition and alveolar processes exceed the
limit of orthodontic movement.36
As the appliance is
activated the force causes a bending of the alveolar
process which then results in a distraction force across
the midpalatal suture.9
During the first stages of
expansion it has been shown that the force from the
appliance accumulates, and this leads to a decrease in the
mineral content of the suture.36
Then, once opening of the
suture is obtained, the force needed becomes less.
It was
measured that a single activation of a Haas or hyrax
appliance can produce 3-10 lbs of force across the suture.37
The Haas Appliance
Although the use of maxillary expansion has been
documented from as early as 1860,2 its use was not
popularized until Haas introduced an appliance in the
9
1950s.8
The Haas appliance was fixed and banded to the
first permanent molars and first pre-molars, connected to a
jackscrew in the center near the mid-palatal suture, with
acrylic coverage of the palate.
It has been suggested that
acrylic coverage allowing the appliance to be tissue borne
as well as dental, allows for more parallel expansion force
to the alveolar ridges. On the other hand, this appliance
also has the potential for tissue damage and irritation to
the patient.9
The Hyrax Appliance
In 1968 William Biederman introduced his Hygienic
rapid expander (Hyrax).38
This appliance was designed
similar to the Haas expander but connected the jackscrew to
the dentition with a wire frame thus removing the acrylic
coverage of the palate.
The idea was that this would be
less irritating to the patient, easier for the clinician to
fabricate, and easier for the patient to keep clean.38
Timing of Treatment
The goal of RME is to obtain expansion of the
maxillary complex through separation of the maxillary bones
10
and minimize the effects on the dentition.
In order to
obtain this separation, expansion should be completed
before the fusion of the suture is complete.
Most studies
show that the suture fuses slowly over time, but that
growth is usually complete at an average age of 16 years in
females, and 18 years in males, with a great amount of
individual variation.10,25,26,29,30
Persson and Thilander in a
study using 24 necropsy specimens found that the earliest
complete fusion of the midpalatal suture occurred in a 15
year old female, while a sample taken from 27 year old
female showed no signs of fusion.39
According to Baccetti
et al. rapid maxillary expansion should be performed before
peak growth velocity in order to obtain a better transverse
skeletal change.40
It has been shown that the average peak
growth velocity occurs at 7-11 in males and 6-11 in
females.26
Because RME can be more effective at these
younger ages, in patients where transverse deficiency is
severe, it is often ideal to perform the treatment during
this time.
RME can sometimes be achieved on older
patients, but orthopedic changes can be relatively small,
and there will usually be a greater amount of relapse.12
11
Effects of RME
The primary purpose of RME is to expand the maxillary
complex, ideally through a skeletal correction.
However,
since everything is connected, changes occur not just
skeletally, but also in the dentition and soft tissue as
well.
This may result in side effects that may be
desirable or undesirable depending on the case being
treated.1
Skeletal Effect of RME
Studies have shown that RME affects more than just the
midpalatal suture.
Chaconas and Caputo showed that sutural
resistance to RME not only comes from the midpalatal
suture, but also at other articulations in the maxillary
complex, such as the zygomatic and sphenoidal sutures.37
Their research suggests that resistance and opening at
these sutures may be a more significant influence on
obtaining orthopedic movement than the resistance at the
midpalatal suture.
It has also been verified that there is
some degree of separation at several sutural articulations
of the maxillae.
This has recently been well documented by
three dimensional CT imaging.41
12
Haas reported changes in the width of the nasal cavity
in both pig and human samples.9,13
In humans Haas found an
increase in intranasal width to be 4.1 mm.13
This study was
repeated both by Haas and other investigators who
demonstrated that the range of the increase was from 2.14.5 mm.11,40,42,43
Wertz published a study in 1970 which looked at the
direction and magnitude of maxillary displacement with RME.
He examined 60 cases that he had treated for correction of
bilateral “maxillary narrowness,” as well as 2 dried skulls
which he subjected to the same therapy.
He found that
there was a consistent downward displacement of the
maxilla.
Also from a superior view, separation of the
midpalatal suture did not occur in a parallel fashion,
Wertz found that greatest expansion was seen in the
anterior at the anterior nasal spine, then diminished
posteriorly.12
It was also shown that the maxillae separate
in the vertical plane in a triangular pattern, with the
apex near the maxillofrontal suture with progressively more
skeletal separation inferiorly.11,12
During RME it has also been shown that there is a
displacement of the maxillae in a downward and forward
direction.9,11
This results in a downward and forward
movement of A point.9,12
Haas reported that the maxilla
13
moves 2.5 mm downward and 3.5 mm forward.43
Haas stated
that this movement is due to the orientation of the suture
of the maxilla.
He suggests that as sutures other than the
midpalatal open during RME it produces a similar effect as
growth would at these sutures thus producing a resulting
downward and forward displacement.43
Effects in the position of the mandible have also been
reported.
The mandible shows a downward and backward
rotation due to its articulation with the maxilla.
This
result leads to an increase in the mandibular plane angle.44
Dental Effects of RME
The dental changes of RME can be substantial.
Dental
effects are greater than skeletal effects because the
appliance is anchored to the teeth, and any skeletal
changes that occur reflect as dental change as well, since
the teeth are located in the bone.
Diastema opening between the central incisors is noted
as a clinical sign that suture separation has been
achieved.
Haas stated that the width of the diastema is
approximately half the amount of the screw activation.9
Other studies by Lagravere et al. showed that the average
diastema opening in patients undergoing RME was 2.98 mm.45
14
The diastema formed, however, is only temporary as the
incisors begin to tip mesially back into proximal contact
and, unaided, the root will then upright over a period of
about four months.11,12
Dental effects are also seen with regard to the first
maxillary molars.
Tipping of the molars generally occurs
with great variability.
Studies have shown that the change
of angulation of the first molars can be anywhere from 124º.9,46
Lagravere et al. in thier metanalysis of the
literature stated an average of 3º of tipping occurs across
the posterior teeth but concluded that this was not
clinically significant.45
They also showed that the
intermolar width increases 6.00-6.75 mm, and that the
intercanine width increases 5.00-5.30 mm.
Also the first
maxillary molars extrude an average of 0.5 mm, and overjet
increases an average of 1.3 mm.45
These effects, combined
with the downward and forward displacement of the maxilla,
have shown to result in an increase in vertical dimension
and opening of the bite.13,42,47
Another significant change seen in the dentition is in
total arch perimeter.
An increase of 1 mm in interpremolar
width adds approximately 0.7 mm of arch perimeter.5 Patients
undergoing RME were shown to have an average increase in
arch perimeter of about 4 mm.14
15
Soft Tissue Effects of RME
Although RME has a long history of use and remains a
common treatment, little research has been done on changes
it produces with regard to the facial soft tissues and
appearance of the face.
Karaman et al. evaluated soft tissue changes induced
by RME.
They used lateral cephalograms taken on 20
patients pre- and post-RME treatment.
They found that nose
tip and soft tissue A point followed the anterior movements
of the maxilla and maxillary incisors.
Also, following
expansion, the dimensions of the mid- and lower face
increased vertically.19
A study by Kilic et al. measuring soft tissue angles
based on the Holdaway soft tissue analysis showed other
changes take place.
In this study researchers evaluated
the short-term soft tissue changes associated with RME.
They used 18 subjects who started with a diagnosis of
bilateral crossbite.
This study was based on measurements
taken from lateral cephalograms taken at three different
times including: before RME, after expansion, and at
retention about 6 months afterwards.
Then they evaluated
measurements through a soft tissue analysis.
The soft
tissue facial angle was found to decrease, while the H
16
angle and profile convexity increases after RME.
The soft
tissue facial angle and H angle showed insignificant
changes during the retention period. Although some recovery
took place during retention, the increases in skeletal
profile convexity and H angle were statistically
significant for the total period.48
Berger et al. measured facial changes based on
measurements made from digital photos and found changes in
several areas.
They found that nose length had a
significant decrease of 0.7 mm during the expansion
process.
The upper lip length had significant change
during the expansion process showing an increase of 1 mm
during expansion.
They found that overall facial height,
represented by the sum of the nose length (excanthion to
subnasale), upper lip length (subnasale to stomion), and
the lower lip-chin length (stomion to menton), showed a
total decrease of 0.6 mm.
Eye width showed a decrease of
0.4 mm, while the intercanthal distance increased by 0.3 mm
following active expansion.
increase by 1.0 mm.
Lower face width was shown to
Nose width was shown to increase
significantly by 1.9 mm.
Lower lip vermilion distance
increased by 0.2 mm, while the upper lip vermillion height
distance showed no change.20
This study shows that many
dimensions of the face are affected by RME treatment.
17
Compared with the large amount of information
available about the hard tissue changes associated with
RME, there is a relatively small amount of information
regarding soft tissue changes.
Studies that are available
largely neglect non-midline structures.
Factors such as
soft tissue thickness and the elastic nature the of soft
tissues create changes that are not necessarily at a one to
one ratio with changes taking place in the underlying hard
tissue.
Park and Hwang in a study looking at the ratio of
change seen in soft tissue versus hard tissue following
orthognathic surgery, have shown that there are significant
differences in this ratio depending on the site. Overall
there was a significantly lower ratio seen in the soft
tissue over the maxilla than that noted in the mandible.15
Two-Dimensional Soft Tissue Analysis
Finding a reliable method of measuring soft tissue
change is difficult.
Landmark identification in the soft
tissue is complicated by the rounded, flowing nature of
tissue.17
It is thus difficult to ensure the exact point
that is being measured is the same landmark when comparing
the pre- and post-treatment soft tissue measures.18
There
have not been a large number of studies measuring soft
18
tissue changes produced by palatal expansion.
Most of the
studies involving soft tissue change deal with surgical
treatments where tissue changes and differences in facial
appearance are much more obvious.
The more reliable points
are those that lie on the midline, or those that lie on the
most anterior portion of a sagittal view.
As a result,
many studies looking at soft tissue changes have focused on
midline changes, or those that affect the profile of the
patient.
This section discusses two dimensional methods of
comparing soft tissue changes that have been utilized.
Photographic Images
One way to determine soft tissue changes in the face
is with two dimensional photographs.
An example of this is
the study performed by Berger et al. to measure changes in
patients who had undergone palatal expansion by either
surgical or non-surgical means.20
Measurements were made
from frontal photos of patients pre- and post-treatment, as
well as during treatment.
Photographs were taken with the
patients head in a natural position, at a standardized
focal length.
Each photograph was calibrated by including
a photo of a 12 inch ruler in the image that was then
matched to the ruler’s actual size when the image was
19
projected.
Ten different measurements were then made
according to the researchers’ protocol, which were then
compared on pre- and post-treatment photos.
It is also possible to make two dimensional
comparative measurements of the soft tissue on sagittal
photos.
Various angles of photos may be used to attempt to
recreate a three dimensional rendering of the patient.
However due to the difficulty of reliably locating
landmarks the process becomes highly susceptible to error.
Lateral Cephalograms
Lateral cephalograms are another option for measuring
change that takes place during RME treatment. With lateral
cephalograms it is possible to study the soft tissue of the
patient’s profile.
Comparing midline structures by this
method has been one of the most common ways to report soft
tissue changes associated with orthodontic treatment.19,49,50
Karaman et al. used lateral cephalograms to study the
changes of the soft tissue profile.
They performed their
study on 20 growing children (10 male and 10 female) who
were diagnosed with bilateral crossbite and “maxillary
collapse.”
The age range of the patients was from 10.1
years to 14.8 years with an average of 12.8 years.
20
Patients were treated with a bonded RME appliance with
expansion activated at a rate of 0.5 mm/day.
Lateral
cephalograms were taken with the patient in centric
relation before and after RME treatment.
They used a
reference plane that was created by drawing a vertical line
perpendicular to the SN plane that intersected SN at the
anterior wall of sella tursica.
Measurements were made on
pre- and post-treatment radiographs and the observed
changes were reported.19
After RME, it was seen
that the nose tip and soft tissue of A point followed hard
tissue of A point in a forward and downward displacement.
Posteroanterior Cephalograms
Many studies have used lateral cephalograms to study
changes associated with RME, but there have been relatively
few that have employed posteroanterior (PA)
cephalograms.9,10,12
This may be because many researchers are
reluctant to use PA cephalograms for many reasons
including: difficulties in reproducing head posture and
landmarks due to poor radiographic technique, or variable
reliability in locating various skeletal and dental
landmarks.51
Cross and McDonald used PA cephalograms to
determine effects of RME on skeletal, dental, and nasal
21
structures.6
Since soft tissue landmarks are often even
less reliable than hard tissue landmarks there have not
been any studies that relied on PA cephalograms to measure
soft tissue changes associated with RME treatment.
Three-Dimensional Soft Tissue Analysis
In the attempt to produce detailed information about
patients and treatment outcomes, orthodontists and other
healthcare professionals have begun to explore threedimensional imaging.
In a review on craniofacial imaging,
Quintrero et al. suggest that the best option of patient
imaging is the one that provides the most information, with
the least expense and risk to the patient.52
Three-
dimensional imaging is able to provide a much greater
amount of information than two dimensional imaging.
In an early attempt to create three dimensional
images, researchers used a process called 3D cephalometry.
The idea behind this was to use lateral and posteroanterior
cephalograms together by matching up landmarks on each to
recreate the three-dimensional structure.
This method
proved to be unreliable and was unable to provide much
information about soft tissue change.16,53
22
Physical Measurement: Direct and Indirect
Direct physical measurement taken directly on the
patient’s face, (e.g., with calipers) is the most basic
form of 3D measurement.
Such measures may also be made in
an indirect manor, utilizing impressions and plaster casts
of the patient’s face.54
Such techniques have been used
recently to measure nasal change using nasal casts.17
Indirect measurement has further advanced as
demonstrated by the “3 draw” system developed by Polhemus
Inc. (Colchecster, VT).
This was used in a study by Sforza
et al. and uses a temporary marking device (Sforza used a
liquid eye-liner) to manually mark facial soft tissue
points.55
These points are then digitized with reference to
a 3D coordinate grid by a computerized electromagnetic
digitizer; this then allows distances and angles between
the points to be calculated.
This method does require
patients to hold their heads still for approximately one
minute as digitization takes place; any movement may
introduce error into the process.
The primary advantage of
making physical measurements is that they are non-invasive.
23
Laser Facial Scanning
Laser scanning utilizes laser technology to obtain
three-dimensional information regarding the surface of
objects being scanned.
This technology has been applied to
some extent in the healthcare industry.
This method works
by using a camera which records distortions of a vertically
fanned laser on a patient’s face as the patient is rotated
on a turntable.
Day and Robert used a handheld optical
laser scanner to scan the patient while the patient remains
stationary.
They used this form of laser scanning to study
soft tissue changes following orthognathic surgery.56
This
process leads to the display of the image as a construction
of small triangular surfaces which reflect a theoretical
light source.
Different scans can then be compared by
superimposing them along stable soft tissue points.57,58
One difficulty associated with laser facial scanning
is the time required to obtain the scan.
The longer the
scanning time, the more potential there is for patient
movement which will then create error and a less useful
image.59
Also, most laser scanning devices are reported to
have accuracy in the range of 0.5 mm to 2 mm.57,60,61
In a
study comparing dimensions taken by laser scanning compared
to those taken by direct measurement, Kovacs et al. found
24
that approximately half of their measures differed by more
than 2 mm.62
Digital Photogrammetry
Three-dimensional photographic imaging uses a series
of cameras and lights placed at various positions around
the patient.
The obtained images are joined by a computer
program which takes into account the different camera
positions and focal lengths so as to create a 3D
image.53,59,63,64
This is an evolved form of
stereophotogrammetry, which uses photos from different
positions and attempts to create a 3D image manually,
rather than being done by a computer.65
A study by Weinberg et al. investigated the precision
of 3D imaging by comparing measurements taken by two
different digital photogrammetry systems (Genex and 3dMD)
to measurements taken by direct physical measurement.66
In
this study the sample included 18 different mannequin
heads, and took 12 linear measurements (each made twice by
each method), and evaluated intraobserver precision across
the three methods.
They found that the overall mean
differences were small enough to be considered
25
insignificant, and that data obtained by either system
could be combined or compared statistically.
Like laser facial scanning this method only allows for
study of the surface changes.
Any subsurface measures,
including those of the hard tissue, cannot be obtained with
this method.
Computed Tomography
Computed tomography (CT) is a method involving
traditional tomograms that uses digital geometry processing
to create a 3D image.52
This method was first developed and
introduced commercially in the early 1970s by Godfrey
Hounsfield.64
This method of imaging has several advantages
over 3D imaging techniques discussed thus far. Computed
tomography images contain information for both hard and
soft tissue structures and the technology can also provide
information about surface and subsurface structures.
This
allows for registration of the images on the more reliable
hard tissue structures, while still being able to locate
soft tissue landmarks.
Also the need for standardization
of the head position of the patient during the acquisition
of the image is not as important because head position can
later be manipulated by the computer software to orientate
26
the head according to a reference plane.22,67
The ability to
manipulate the images with computer software also allows
the operator to change sharpness, opacity, contrast and
other properties that may help to identify and label
landmarks and registration points.
The scans may also be
viewed in cross section or individual parts for better
landmark identification.22,52,64
Although there are many advantages to using computed
tomography, Quintero et al. suggests several reasons why it
may not be appropriate for orthodontic diagnosis.52
They
state that the CT scans are too expensive and expose the
patient to too much radiation to be used routinely in
orthodontics, although in some situations the benefit may
outweigh the risks.
They also suggest that CT imaging in
inefficient at producing suitable soft tissue contrast.
Some researchers have suggested methods to combine CT
images with three-dimensional photographic images.67,68
Recent research however has shown that this method produced
errors that were relatively large especially around the
eyebrows, eyelids and cheeks.69
27
Cone-Beam Computed Tomography
Cone-beam computed tomography (CBCT) was developed to
counter some of the problems associated with conventional
CT scanning.70
In CBCT the image is captured as radiation
hits a two-dimensional detector.
This allows the image of
the entire region to be captured in a single pass rather
than multiple slices which are later stacked as in
conventional CT.22
The radiation source consists of a
conventional, low-radiation x-ray tube, and the resultant
beam is projected onto a panel detector, producing a more
focused beam and considerably less scatter radiation
compared to the conventional CT devices.23,71
It has been
suggested that radiation exposure with CBCT is about 20%
the amount of a traditional CT, and is comparable to a
full-mouth periapical radiograph panel.23
The software currently available is also able to
generate all radiographs traditionally used in orthodontic
diagnosis.
This allows diagnostic panoramic, periapical,
occlusal, and cephalograms radiographs to be produced from
the image acquired during CBCT.72
Advances in CBCT have caused it to become a more
commonly used method of 3D imaging in the field of
orthodontics.
The CBCT images give a much greater amount
28
of information than the traditional radiographic methods
that have been used.
As information from these images
becomes more readily available to researchers in
orthodontics, it provides greater ability to more fully
understand the impact and changes that occur as the result
of orthodontic treatment.
Summary and Statement of Thesis
Rapid maxillary expansion is a very common and well
established treatment in orthodontics.
Orthopedic changes
can be achieved through its use in patients with transverse
deficiency.
This treatment creates changes in the
patient’s hard and soft tissue.
The soft tissue changes that take place with RME are
not well documented in the literature.
This is partly due
to the available methods that have been used in the past to
capture and evaluate the soft tissue images.
Also the
problem of locating reliable landmarks and reference points
on soft tissue has made it difficult for researchers to
measure changes in soft tissue that do not lie along the
midline region.
Two-dimensional imaging has been unable to provide a
reliable method for measuring changes in shape and depth of
29
the soft tissue.
as well.
Three-dimensional imaging has weaknesses
Many techniques have been either too expensive or
expose the patient to too much radiation to be used
routinely.
Others have been unable to show both hard and
soft tissue structures, some only being able to record
surface information.
With CBCT being developed as a method to acquire
needed information with less radiation to the patient, it
is becoming a routine method of imaging.
With more of this
information becoming available it allows investigators an
opportunity to measure hard and soft tissue changes
associated with orthodontic treatment.
The purpose of this study is to quantify the immediate
soft tissue changes in the transverse and anteroposterior
planes following RME in growing patients, using CBCT
images.
30
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37
CHAPTER 3:
JOURNAL ARTICLE
Abstract
Introduction:
The development and increased use of cone
beam computed tomography (CBCT) in orthodontic treatment
provides a means to measure changes on the soft tissue that
are not on the facial midline.
Purpose:
The purpose of
this study is to demonstrate a reliable method of measuring
soft tissue changes associated with rapid maxillaey
expansion (RME) treatment to quantify immediate soft tissue
changes in the transverse and anterior-posterior planes
following RME in growing patients, using CBCT images.
Materials and Methods:
A sample of twenty-three
consecutively treated patients, who had been treated by RME
was utilized for this study.
Patients were scanned using
CBCT prior to placement of the rapid maxillary expander
(T0), then immediately following full activation of the
appliance (T1).
Defined landmarks were then located on the
pre- and post-treatment orientated images.
Change in
landmark position from pre- to post-treatment was then
measured.
Results:
This sample had a mean appliance
expansion of 5.2mm. Significant transverse expansion was
measured on most soft tissue landmark locations.
38
All the
measures made showed significant change in the lip position
with a lengthening of the vertical dimension of the upper
lip, and a generalized decrease in thickness of both the
upper and lower lips.
Conclusions:
Significant changes in
the soft tissue do occur with RME treatment.
There is a
transverse widening of the midface, and a thinning of the
lips.
39
Introduction
Rapid maxillary expansion (RME) is a treatment that
has been described in the orthodontic literature since
1860.1,2
It is often used during the mixed dentition as a
treatment for posterior crossbites and crowding of the
dentition.3
The hard tissue changes that take place as the
result of RME have been well documented in the orthodontic
literature.3-12
Most studies show that transverse expansion
seen with RME is 50% skeletal and 50% dental.1
Effects
include buccal tipping of the molars and premolars5 and a
downward and forward displacement of the maxilla.12-14
Compared with the large amount of information
available regarding the hard tissue changes associated with
RME, there is a relatively small amount of information
available regarding soft tissue changes.
Studies that are
available largely neglect structures lateral to the
midline.
Studies of soft tissue change involving facial regions
lateral to the mid-line are limited partly because these
structures are not identifiable on traditional twodimensional cephalograms.
15,16
Also it is difficult to
repeatedly identify soft tissue landmarks due to the nature
of these tissues.17,18
Karaman et al. evaluated soft tissue
40
changes induced by RME.
They used lateral cephalograms
taken on 20 patients pre- and post-RME treatment.
They
found that the nose tip and soft tissue A point followed
the anterior movements of the maxilla and maxillary
incisors.19
One attempt to measure regions lateral to the midline
was made by Berger et al.
They measured facial changes
based on measurements made from two dimensional digital
photos and found changes in several areas.20
Using this
method they documented some changes that take place in the
soft tissue when viewed from a frontal view.
With more information becoming available through the
more widespread use of cone beam computed tomography (CBCT)
in orthodontics, there is greater potential to study the
effects orthodontic treatment has on the soft tissue.
Progress in software development has allowed for more
manipulation and better viewing of the CBCT images, which
allows for more accurate and repeatable collection of
information.21
Cone beam computed tomography provides high
resolution three-dimensional imaging that contains
information of both hard and soft tissue, with the added
benefit of being less expensive and delivering less
radiation to the patient than traditional tomography.22,23
41
The purpose of this study is to quantify the immediate
soft tissue changes in the transverse and anteriorposterior planes following RME in growing patients, using
CBCT images.
Materials and Methods
Twnety-three consecutive RME patints were used for
this study collected from an orthodontic private practice.
Patients had all been diagnosed with a skeletal transverse
discrepancy, and undergone RME treatment performed by the
same orthodontist using the same protocol.
After applying the exclusion criteria, 23 patients
were included in the study.
The mean age of the patients
at the time the first CBCT image was taken was 12.3 ± 2.6
years, with a range of 8.3 to 17.8 years.
The second CBCT
image was taken a mean of 22.8 days later with a range of
14 to 37 days.
Each patient had been treated with a fixed rapid
maxillary expander.
The expander used in all cases was
manufactured by Dentaurum (DENTAURUM Group, Ispringgen,
Germany) and contained a 7 mm expansion jackscrew.
The
stainless steel appliance was soldered to orthodontic bands
on the maxillary first molars, with supporting arms
42
extending anteriorly to the premolar and canine regions
(Figure 3.1).
Figure 3.1- Model of Palatal Expander used on patients
in this study
The rapid palatal expander was activated two onequarter turns (0.2 mm each quarter turn) of the jackscrew
at the delivery of the appliance, then by one one-quarter
turn twice a day by the patient or parent.
Active
expansion of the appliance continued until overcorrection
of the transverse discrepancy was achieved.
Overcorrection
was achieved when the palatal cusps of the maxillary molars
were in an edge-to-edge relation with the buccal cusps of
the opposing mandibular teeth.
43
Each patient received two CBCT scans, one prior to the
delivery of the appliance (T0), and one immediately
following the active expansion phase of treatment (T1).
All scans were taken by the same technician.
The patients
were stabilized with their teeth in occlusion in centric
relation, and with the Frankfort Horizontal plane parallel
to the floor.
The Classic i-CAT CBCT scanner (Imaging
Sciences International, Hatfield, PA) was used for all
scans, and required 20 seconds for each scan, with voxel
size set at 0.4 mm.
Each dataset was assigned a number to eliminate the
possibility of patient identification and imported to
Dolphin Imaging 10.5 software (Dolphin Imaging and
Management Solution, Chatsworth, CA).
The image was
orientated along the mid-sagittal plane (z plane),
Frankfort horizontal plane (x plane), and a coronal plane
(y plane) extending through the anterior wall of the right
and left external meatus.
The image was orientated first
to the mid-sagittal plane (determined by nasion, sella, and
point between nasal bones), then the horizontal plane was
created perpendicular to the sagittal plane on the
Frankfort Horizontal plane.
Finally the coronal plane was
created perpendicular to the two already determined planes,
44
and set against the anterior wall of the right external
meatus.
(Figure 3.2)
Figure 3.2: The standard orientation using threedimensional planes.
45
Landmark Assessment
Placement of landmarks was accomplished on the Dolphin
Imaging software.
This allows for points to be defined
three-dimensionally using an x,y,z Cartesian coordinate
system, based on the 3 planes of orientation.
A series of
20 landmarks were located on each pre- and post-treatment
scan and located three-dimensionally by their x,y,z
coordinates (Figure 3.3, 3.4, 3.5).
The landmark at the
tip of the nose was only made on 8 of the sample because it
was not captured on all images.
For most of the landmarks, change was measured in the
transverse plane.
To detect changes in the transverse
plane the x coordinate was used.
For other measures,
change was measured in the anteroposterior position.
To
measure anteroposterior change the z coordinate was used.
A list and definition of all the landmarks placed can be
found in Table 3.1; this table also shows the direction of
change for each landmark.
46
Figure 3.3:
Frontal view with soft tissue landmarks.
47
Figure 3.4: Soft tissue nasion in line
with sella-nasion on the midsagittal plane
48
Figure 3.5: Bridge of nose (BN) made along plane parallel
to FH plane crossing the tip of the nasal bones, on the
midsagittal plane
49
Table 3.1: Definitions of anatomic landmarks located
Landmark
Definition
Plane
Exocanthion
(Ex)
Endocantion
(En)
Lateral commissure of the eye
recorded bilaterally
Medial commissure of the eye,
recorded bilaterally
Soft tissue over the junction of
the nasomaxillary suture and
nasofrontal suture, recorded
bilaterally
point of intersection between
the sellanasion line and the
soft tissue profile
Soft tissue over most lateral
point of the zygomatic arch,
recorded bilaterally
Soft tissue on midsagittal plane
over the tip of the nasal bone,
extended parallel to FH plane
On frontal view located the
superior anterior extent of the
infraorbital foramen, landmark
placed on soft tissue over that
point, extended parallel to FH
plane, recorded bilaterally
Viewed frontal and inferiorly
where nasal alar meets face on
the inferior border of nose,
recorded bilaterally
Most anterior point of the nose
recorded on the midsagittal
plane
point at which the nasal septum
merges, in the midsagittal
plane, with the upper lip
Soft tissue over the center of
the upper first molar crown,
extending perpendicular from the
mesial-distal plane of the
crown, recorded bilaterally
Point of union of the upper and
lower lip, recorded bilaterally
median point of the mouth when
the mouth is closed
x
Apex of nose
(AN)
Soft tissue
nasion(Na)
Soft tissue
zygion (Zy)
Bridge of Nose
(BN)
Soft tissue
over
infraorbital
foramen (INF)
Alar base (AB)
Nasal tip (NT)
Subnasale (Sn)
Lower midface
(LMF)
Lip commissure
(LC)
Stomion (St)
50
x
x
z
x
z
x,z
x
z
z
x
x
Z
In addition to the landmarks, 10 direct measurements
were made between two defined points (Figures 3.6, 3.7,
3.8).
One direct measure was also made on the post-
treatment image of the mesial and distal aspects of the
rapid palatal expander to assure expansion had taken place.
These measurements were taken at the level of the center of
the crown of the central incisors, one for the upper and
one for the lower.
These were used to measure changes in
the thickness of the upper and lower lips.
Five measures
were made on the upper lip. The first one along the midsagittal, and one over each of the maxillary incisors.
The
point over the incisors was made from the center of the
crown to a point in the soft tissue extending along a line
that ran perpendicular to the mesial-distal plane of the
tooth.
There were four measures on the lower lip one over
each mandibular incisor made using the same method as that
described for the upper lip.
The tenth measure made was
done on the frontal view of the three-dimensional image
with the soft tissue and ran from the landmarks made at
subnasale and stomion.
This was used to measure change in
the vertical length of the upper lip.
made were recorded in millimeters.
All of the measures
The change was then
averaged for five measures on the upper lip and the four
51
measures on the lower lip to describe the average change in
the thickness of each lip.
Figure 3.6: Measurements of the upper lip thickness.
1. Midsagittal plane. 2. Left cenral incisor. 3. Left
lateral incisor. 4. Right central incisor. 5. Right
Lateral incisor
52
Figure 3.7: Measurements of the lower lip thickness.
6. Right central incisor. 7. Right lateral incisor.
8. Left central incisor. 9. Left lateral incisor
53
Figure 3.8:
Measure made for length of upper lip made from
subnasale to stomion.
Statistics
Descriptive statistics including the mean, standard
deviation, and minimum and maximum values were calculated.
For the landmarks, statistics describe the amount of change
in the specific plane being investigated.
For the measures
that were made the statistics describe the absolute amount
of change between the two points independent of the
direction of change.
All statistics were calculated using
SPSS 14.0 Statistical Software (SPSS, Inc., Chicago, IL).
54
In order to determine the significance of described
changes, the paired t-test was used.24
The level of
significance was defined as p<0.05.
To asses the accuracy of landmark placement and
repeated measures reliability testing was performed.
Three
of the twenty-three patients were randomly selected and all
landmarks and measurements were duplicated.
A Cronbach’s
alpha test was executed on repeated measures.
A perfect
score equals 1.00, while a Cronbach’s alpha greater than or
equal to 0.80 is considered an indicator for a reliable
technique.
Reliability testing was also used to determine
the accuracy of the method of orientation.
This was
calculated by placing landmarks in non-changing areas of
the skull, in this case on the anterior-superior border of
the right and left foramen ovale.
Results
All landmarks had a Cronbach’s alpha above 0.80.
The
intraclass correlation coefficient showed all the landmarks
to be reliable.
The lowest of the Cronbach’s Alpha
measurements reported was 0.842 for subnasale.(Table 3.2)
55
Reliability using the Cronbach’s alpha for orientation
showed x at 0.966, z at 0.993, and y 0.615.
No measures
were taken using the y-axis in this study.
The mean amount of expansion in this sample was 5.2 mm
with a range from 3.1 mm to 6.4 mm, shown by opening of the
RME.
Opening of the midpalatal suture was in the anterior
region was reported to be 1.5 mm as reported in study using
the same sample.16
The descriptive statistics for all measures are listed
in Tables 3.3, 3.4, and 3.5.
The statistics for the paired
t-test are shown in Tables 3.6, 3.7, and 3.8.
The
measurements for all but four of the landmarks show
significance.
The four landmarks that did not show
significance were soft tissue nasion, the left lip
commissure, the right nasal apex landmark, and the right
soft tissue over the upper first molar.
All of the
measured values for the lips showed a significant change.
The average change of the upper lip was then
calculated by taking the mean of the change seen in the
five measures on the upper lip.
The average change in
thickness of the upper lip was -0.922 mm.
The same measure
was made in the lower lip and change in thickness was
calculated to be -1.035 mm.
These demonstrated a mean
decease in upper and lower lips thickness.
56
Table 3.2: Cronbach’s alpha for intraclass correlation
coefficient of landmark identification.
Landmark
Cronbach’s alpha
Right excantion
1.000
Left excantion
.990
Right endocantion
.971
Left endocantion
.989
Right lip commissure
.996
Left lip commissure
.992
Right alar base
.977
Left alar base
.999
Soft tissue nasion
.999
Bridge of nose
.997
Subnasale
.842
Right apex of nose
.908
Left apex of nose
.898
Right inf
.984
Left inf
.977
Nasal tip
.965
Right lower face
.997
Left lower face
.996
Right zygion
.996
Left zygion
.943
57
Table 3.3: Transverse change descriptive statistics
*significant values
MINIMUM
MAXIMUM
MEAN
STANDARD
Measure (MM)
N
CHANGE
CHANGE
CHANGE
DEV
Right Ex
23
-1.3
3.3
0.90*
1.18
Right En
23
-0.3
4.0
1.30*
1.17
Left En
23
-1.4
5.6
1.22*
1.76
Left Ex
23
-1.9
4.3
1.08*
1.24
R LC
23
-1.0
4.0
1.20*
1.45
L LC
23
-4.6
3.4
0.65
1.52
R AB
23
0.86*
-0.3
2.7
0.73
L AB
23
-0.9
3.0
0.93*
0.87
R AN
23
-2.5
2.6
0.43
1.25
L AN
23
-0.6
4.4
0.89*
1.06
R Inf
23
-2.0
2.5
0.85*
1.00
L Inf
23
-0.1
3.3
1.12*
0.97
R LMF
23
-2.9
4.6
0.78
1.89
L LMF
23
-1.6
4.0
1.49*
1.28
R Zy
23
-0.2
2.2
0.88*
0.65
L Zy
23
1.10*
-0.3
4.4
1.28
Table 3.4:
Anteroposterior change descriptive statistics
*significant values
MINIMUM
MAXIMUM
MEAN
STANDARD
Measure (MM)
N
CHANGE
CHANGE
CHANGE
DEV
Na
23
0.43
-2.0
2.3
1.24
BN
23
0.79*
-1.7
3.4
1.36
NT
8
1.58*
0.4
2.3
0.68
Sn
23
2.21*
0.7
4.4
1.23
R Inf
23
1.21*
-2.5
4.3
1.56
L Inf
23
0.96*
-1.2
3.5
1.27
58
Table 3.5:
Measure (MM)
Upper Lip
Vertical
Upper Lip MS
Upper Lip L1
Upper Lip L2
Upper Lip R1
Upper Lip R2
Lower Lip R1
Lower Lip R2
Lower Lip L1
Lower Lip L2
Direct measures descriptive statistics
*significant values
MINIMUM
MAXIMUM
MEAN
STANDARD
N
CHANGE
CHANGE
CHANGE
DEV
23
-0.5
3.3
0.92*
1.04
23
23
23
23
23
23
23
23
23
-2.8
-2.6
-2.5
-2.5
-4.2
-3.4
-4.2
-3.8
-3.6
0.3
0.3
0.8
1.0
1.0
0.7
0.8
0.2
0.5
-1.07*
-0.68*
-0.77*
-0.93*
-1.16*
-0.99*
-1.07*
-1.19*
-0.89*
0.93
0.70
0.84
0.98
1.22
1.06
1.06
1.01
1.05
Table 3.6: Transverse change paired t-test results
(significance p<0.05)
*values that are significant
Measure
t
Sig. (2-tailed)
Right Ex
3.661
.001*
Right En
5.344
.000*
Left En
3.322
.003*
Left Ex
4.157
.000*
R LC
3.956
.001*
L LC
2.056
.052
R AB
5.629
.000*
L AB
5.186
.000*
R AN
1.678
.107
L AN
4.018
.001*
R Inf
4.080
.000*
L Inf
5.525
.000*
R LMF
1.986
.060
L LMF
5.588
.000*
R Zy
6.561
.000*
L Zy
4.124
.000*
59
Table 3.7:
Anterioposterior change paired t-test results
(significance p<0.05)
*values that are significant
Measure
t
Sig. (2-tailed)
Na
1.661
.111
BN
2.694
.014*
NT
6.611
.000*
Sn
8.626
.000*
R Inf
3.734
.001*
L Inf
3.623
.002*
Table 3.8:
Direct measures paired t-test results
(significance p<0.05)
*values that are significant
Measure
t
Sig. (2-tailed)
Upper Lip Vertical
4.250
.000*
Upper Lip MS
-5.478
.000*
Upper Lip L1
-4.651
.000*
Upper Lip L2
-4.373
.000*
Upper Lip R1
-4.589
.000*
Upper Lip R2
-4.555
.000*
Lower Lip R1
-4.456
.000*
Lower Lip R2
-4.860
.000*
Lower Lip L1
-5.647
.000*
Lower Lip L2
-3.942
.001*
Discussion
The use of CBCT images and imaging software in this
study allowed for repeatable placement of landmarks.
The
ability to orientate the T0 and T1 images to the same
orientation allowed changes to be measured in any plane.
The sample size of 23 was significantly larger than
many other three-dimensional studies that have been done to
60
study soft tissue change.25,26
This gives more power to
statistical analyses used to investigate the data for
significant changes.
This sample was also unique in that
the data provide information directly prior to placement of
the appliance, and directly following the active expansion
phase of treatment, allowing the assessment of immediate
changes, directly attributed to RME.
The mean time between
the scans was 22.8 days with a range of 14 to 37 days.
Even though the sample represents growing children, the
effects of growth are negligible because of the short time
between the T0 and T1 scans.
Results from the measures on the appliance show that
expansion did take place.
The expanders increased a mean
of 5.2 mm with a range from 3.1 mm to 6.4 mm.
Past studies have shown that the greatest amount of
change is seen in the transverse dimension.3,5-12
Many of
the landmarks used in this study were chosen to measure
transverse change in the soft tissue corresponding to areas
of underlying hard tissues that are known to experience
significant transverse changes.
61
Transverse Change
In the upper midface, transverse expansion did occur
in the soft tissue.
Points associated with the right eye
and left eye moved away from the midsagittal plane
representing an increase in the distance between the eyes.
The width of the apex of the nose also showed an increase
although the landmark on the right was not shown to be
significant.
landmark.
This may be due to the nature of the
The landmark used for the apex of the nose is in
and area where there is a large amount of curvature of the
orbit.
Any error in vertical placement of this landmark
would greatly effect the transverse position.
A transverse
increase was also seen in the final position of both the
right and left zygions.
The width of the alar base of the nose also showed an
increase.
Both the right and left landmarks moved away
from the midsagittal plane.
The right side moved by an
average of 0.86 mm and the left by 0.94 mm. Similar
findings of transverse expansion were reported in the hard
tissue nasal base using metallic implants by Krebs10 and
Skeiller27 on posteroanterior cephalograms.
The soft tissue
over the infraorbital foramen showed transverse increases.
The lips and lower midface also showed a transverse
62
increase, although the right lower midface landmark and
left lip commissure were not significant (p=.06 and p=.052
respectively).
Reasons for changes not being significant
could be related to nature of soft tissue.
Any change in
the patients’ muscular tension or occlusion during pre- and
post-CBCT scans could result in a different soft tissue
position not related to expansion.
Also it is possible
that asymmetric expansion took place in some instances
could cause this outcome.
Significant transverse expansion
has also been noted in each of these areas in the hard
tissue in previous studies (Figure 3.10).10-13,16
63
Figure 3.9:
Transverse change of landmarks
*significant
64
Anterioposterior Change
Some points along the midsagittal plane also showed
significant change.
Soft tissue nasion came forward an
average of 0.43 mm however this value was not significant.
The bridge of the nose came forward by 0.80 mm.
The
tip of the nose moved anteriorly by a mean of 1.59 mm
however, this value was only able to be measured in 8
patients.
Subnasale moved anteriorly by a mean of 2.21 mm.
These findings are in agreement with previous findings in
that there is an anterior displacement of the maxilla
during RME.11-13,26,27
Anterior movement was also reported in the soft tissue
over the right and left infraorbital foramina.
This also
would agree with reported anterior displacement of the
maxillary complex that has been described with RME
treatment.11-13,26,27-29
65
Figure 3.10:
Anterioposterior change
*significant
Change in the Lips
The vertical length of the upper lip also was shown to
have a significant mean increase of 0.92 mm.
This finding
agrees with Berger et al.’s study using two-dimensional
66
digital photos which reported a mean increase of 1.0 mm
immediately following the activation phase of expansion.20
The thickness of both the upper and lower lips showed
a significant decrease.
The upper lip changed by a mean of
-0.922 mm, while the lower lip changed by a mean of
-1.035 mm.
This change most likely reflects the effect of
transverse expansion and stretching of the soft tissue of
the mouth.
Although the measure of the left lip commissure
for transverse expansion was not significant (p=.052) the
mean was 0.65mm while one outlier showed a change of -4.6
mm which is likely affecting the significance.
The right
lip commissure showed a significant change of 1.20 mm,
showing that there is some transverse change of the lips
which could account for a thinning of the lips.
This study only looked at the immediate effects of RME
treatment.
Many studies suggest that the effects commonly
seen with RME treatment have a high level of relapse.1012,14,20,27-29
Future studies on this topic may look at relapse
after a period of time to determine the long term stability
of the observed changes.
67
Conclusions
1. Rapid maxillary expansion produces a significant
transverse and anterior displacement of the soft
tissue of the midface of growing.
2. Rapid maxillary expansion produces a significant
increase of the length of the upper lip of growing
children .
3. Rapid maxillary expansion produces a significant
decrease of the thickness of the upper and lower lips.
68
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71
VITA AUCTORIS
Daniel Adams was born on the 1st of July 1975 in San
Pablo, California.
Dr. Adams is the oldest of three
children.
He graduated from Acalanes High School in
Lafayette, California in 1993.
After that he moved to
Rexburg, Idaho to attend BYU-Idaho.
After two years there
he served a two-year mission for The Church of Jesus Christ
of Latter-day Saints in East Africa, serving in the
countries of Kenya, Uganda, and Ethiopia.
Upon his return
from missionary service he attended BYU-Provo where he
graduated with a Bachelor’s degree in Microbiology in 2002.
Dr. Adams began his dental education at Nova
Southeastern University in Fort Lauderdale, Florida and
received his D.M.D. degree in 2006.
In that same year he
began his residency program in orthodontics and Saint Louis
University.
Dr. Adams his happily married to his wife, Chelsey.
They have three children, Koston, 4, Jak, 2, and Penny, 4
months.
Dr. Adams and his family are planning to relocate to
San Diego, California to pursue a career.
72