University of Southern California Dissertations and Theses

A three-dimensional computed tomography comparison of the maxillary palatal vault between patients with rapid palatal expansion and orthodontically treated controls

(USC Thesis Other)

A three-dimensional computed tomography comparison of the maxillary palatal vault between patients with rapid palatal expansion and orthodontically treated controls

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content A THREE-DIMENSIONAL COMPUTED TOMOGRAPHY COMPARISON OF
THE MAXILLARY PALATAL VAULT BETWEEN PATIENTS WITH RAPID
PALATAL EXPANSION AND ORTHODONTICALLY TREATED CONTROLS
by
Elizabeth Gohl, D.D.S.
____________________________________________________________________
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(CRANIOFACIAL BIOLOGY)
August 2007
Copyright 2007 Elizabeth Gohl, D.D.S.
ii
Table of Contents
List of Tables iii
List of Figures iv
Abstract v
Introduction 1
Review of the Literature 2
Significance 26
Hypothesis 27
Subjects and Methods 27
Statistical Analysis 34
Results 35
Discussion 38
Assumptions 41
Limitations 42
Conclusions 42
Bibliography 43
iii
List of Tables
Table 1. Comparison between RPE and controls on baseline and 36
end of treatment characteristics
Table 2. Comparison between RPE and controls absolute and 38
percent change in characteristics over treatment
iv
List of Figures
Figure 1. Midsagittal section: Midsagittal plane 29
Figure 2. Midsagittal section; Crude volume 30
Figure 3. Axial section: Crude volume 30
Figure 4. Coronal section: Crude volume 31
Figure 5. Midsagittal section: Anatomical volume 31
Figure 6. Axial section: Anatomical volume 32
Figure 7. Coronal section: Anatomical volume 32
Figure 8. Coronal section at the level of the first molars: Width measurement 33
Figure 9. Midsagittal section: Height measurements; Tallest and height 34
v
Abstract
Introduction: The purpose of this study was to compare the cone-beam scan
volume measurements between patients with rapid palatal expansion and controls on
archived records. Methods: The study included 16 patients who required RPE and
15 controls; all patients had orthodontic treatment and a beginning and progress
cone-beam CT scan. The volume area of the palatal region was measured and
compared to palatal vault height and width measurements and independent T-tests
were used to analyze the continuous variables. Results: The percent of change in
crude palatal volume was 11.2% in controls and 24.6% in the RPE group. The mean
width increase for the orthodontic only cases was 0.86mm, whereas the mean width
increase for the RPE cases was 2.86mm. There was no significant difference in the
change of palatal vault height. Conclusion: There is a significant difference in
palatal area volume between the RPE and control patients.
1
Introduction
Recent studies have attempted to evaluate three dimensional effects of rapid
palatal expansion (RPE), but these evaluation methods have used two dimensional
cephalometric films. Lateral cephalograms have been used to assess sagittal and
vertical changes and postero-anterior cephalograms have been used to assess
transverse changes due to RPE treatment (Cross et al, 2000; Chung et al, 2004).
However, this data cannot accurately depict the detailed three-dimensional changes
that occur in the maxilla with rapid palatal expansion.
The objective of this study is to compare the three dimensional changes of
skeletal and dental structures in a group of growing patients treated for maxillary
constriction before and after RPE, with a matched control group, using cone-beam
Computerized Tomography (CT) 3-D imaging.
This study will also determine:
• If the volume of the palatal region increases, decreases, or stays the same
with RPE treatment.
o This may answer the question: does the maxillary vault flatten with
transverse expansion or does the roof of the vault remain at the
original height?
• What are the three dimensional changes that occur in the maxilla of a
matched control population with orthodontic treatment only (no RPE)?
• The three dimensional data will be compared with traditional two-
dimensional data of palatal height and width for comparison.
2
Review of the Literature
Normal transverse increases in maxillary basal and alveolar cross-arch width
are believed to result from growth at the median palatal suture and appositional
remodeling along the lateral aspects of the maxilla (Krebs, 1964; Melsen, 1975).
The anatomy of the mid palatal suture becomes more interdigitated with age
Melsen (1975) examined histologic sections of palatal bone recovered at
autopsy of 27 girls and 33 boys varying in age from 0 to 21 years and noticed that
the morphology of the suture tends to have three distinct stages of transverse
patterning. The first stage, in the infantile period, is characterized with the suture
being broad, flat, and “Y” shaped.
3
During the juvenile period (about age 10 years) the suture becomes more wavy.
And finally, the suture becomes more tortuous with increasing digitations
during the adolescent period. This third interdigitation becomes so heavy that
separation of the two halves of the maxilla is not possible without fracturing the
interdigitated segments. In the oldest persons with inactive sutures, Sharpey’s fibers
were seen running across the suture uninterruptedly.
4
The nasal surface of the hard palate showed evidence of resorption until 14-
15y and then consisted of resting lamellar bone. Conversely, the oral surface of the
palatal bone was characterized by apposition up to 13-14y. Remodeling at the
posterior border of the palate was seen up to age 16-18y. This would indicate that
growth in length of the hard palate, which occurs up to puberty, occurs partly in the
transverse suture and partly by apposition on the posterior margin.
Normal transverse width increases
Hesby et al (2006) used a sample of 36 normal, untreated class I subjects and
measured the maxillary cross-arch width at the palatal midalveolar and palatal crest
levels on their dental casts from ages 7-26 years old. The mean maxillary cross-arch
width change at the alveolar crest level (at the first molars) was slightly under 3mm.
But, between the ages of approximately 13 and 16.5 years (years where most RPE
treatment occurs), the transpalatal width increase was only 0.67mm. The mean
maxillary cross-arch width change at the midalveolar level was slightly under 5mm.
The authors correlate these age-related changes with the maxillary molar uprighting
(buccal root torque) that occurs normally with molar eruption. They suggest that
these results follow the idea that the “lateral drift of the palatal surface away from the
midsagittal plane is greater at the level of the first molar roots than at the level of the
first molar crest.” Thus, erupting maxillary molars move laterally as the suture
widens, with the mean transverse growth of the mid-palatal suture between the ages
of four and adulthood being 6.9mm (Bjork et al, 1974), then the molars encounter
5
cheek pressure that force the crowns lingually. Crossbites may prevent this normal
maxillary molar uprighting process and lock them into a position of increased lingual
root torque.
Cessation of normal growth
The timing of the pubertal growth spurt is variable, but, on the average, is
two years earlier in girls than in boys. The age of average peak height velocity
(PHV) is 13.5 years old in boys and 11.5 years old in girls (fiftieth percentile). For
girls, menarche is a good indicator that she has passed her PHV and that her growth
is slowing down. In contrast, boys experience their PHV much later in puberty and
have more variation in the termination of growth. Cessation of growth is variable,
but is usually complete by 17 years old (Enlow, 1990).
Maxillary transverse deficiency; What is it?
Maxillary transverse constriction is a discrepancy secondary to
environmental, genetic, and functional factors. A maxillary transverse deficiency
most commonly manifests itself as skeletal and dental upper arch narrowness and
presents as a unilateral or bilateral buccal crossbite. Implant studies by Bjork (1974)
have shown that the growth of the mid-palatal suture is the most important factor in
determining the width of the maxilla. Typically, a maxillary arch with a transpalatal
width of 36-39mm, as measured from the closest points of the maxillary first molars,
can accommodate a dentition of average size without much crowding or spacing
6
(McNamara, 2000). Thus, maxillary arches which are less than 36mm wide are
frequently going to be too narrow to accommodate the lower arch and will present
clinically as a cross bite.
How common/prevalence
The prevalence of posterior crossbite has been reported to be 7% in white
American children, 1-2% in African American children (Kutin, 1969). In European
children, the crossbite rates are as high as 23% (Kurol et al, 1992). A large study of
Turkish children reported posterior crossbite incidence of 9.5% (Sari et al, 2003).
Reason for treatment
Transverse maxillary deficiencies can give rise to clinical problems such as:
altered dentofacial esthetics, maxillary hypoplasia, asymmetrical facial growth,
positional and functional deviations of the mandible, adverse periodontal responses,
unstable tipping, and other functional problems (Will, 1996). For these reasons and
others, maxillary constriction is well suited to orthopedic expansion.
History of Rapid Palatal Expansion used to treat crossbites
Rapid maxillary expansion was first described in the 1860s by Emerson
Angell using a jackscrew with contrarotating heads (Timms, 1999).
7
Since then, the RPE has gone through various stages of popularity and decline. RPE
treatment was later re-popularized by Haas (1965) as the preferred method for the
correction of maxillary arch constriction by applying expansion pressure across the
mid-palatal suture. By using a rigid appliance, tipping of the molars was limited and
produced orthopedic, and more stable, expansion of the palate. The Haas appliance
has acrylic pads which contact the palatal soft tissue and transmit expansion forces
directly to the skeletal structures. This appliance design is still used today.
However, the large acrylic framework makes cleaning difficult and gingival irritation
can be a factor.
8
The Hyrax design, originally conceived by Biederman in 1968, is a premolar
and molar banded appliance with minimal gingival coverage to facilitate oral
hygiene. It also seems to cause the least amount of gingival irritation, since it does
not contact any soft tissue.
(Reed et al, 1999)
A recent study which compared the Haas and Hyrax devices demonstrated
that tooth-borne and tooth tissue-borne devices tended to produce similar orthopedic
effects, but that the Haas appliance produced a greater change in the axial inclination
of supporting teeth, especially the first premolars, compared to the Hyrax appliance
(Garib et al, 2005).
Historically, there are several other ways to correct a crossbite, including
auxiliary arches or overlay wires that fit into the headgear tubes, cross elastics, a
quadhelix appliance, bonded appliance, or greater than 10mm of expansion in a large
9
(0.021”x0.025”) stainless steel archwire, but these techniques will not be discussed
since they are not relevant to this research project.
Arch perimeter increase
More recently, RPE expansion has been used for reasons other than to correct
maxillary transverse deficiency. Howe et al (1983) showed that crowding in
Caucasians appears to be more often related to a deficiency in arch perimeter than to
teeth that are too large. Maxillary constriction can contribute to arch length
deficiency and therefore, dental crowding.
RPE treatment can widen the maxillary arch and provide additional space of
approximately 3-4mm to relieve crowding (Brust et al, 1995). A study by Adkins et
al (1990) found the arch perimeter increase was approximately 0.7 times the change
in first premolar width. Thus the average gain in arch perimeter in the sample was
4.3mm, which is consistent with the 3-4mm seen by Brust et al.
There are other indications for RPE treatment, including spontaneous class II
correction (McNamara 2000, Gianelly 2003), palatal expansion to reduce the dark
spaces in buccal corridors (Roden-Johnson, 2005), and improving airway function
(Haas 1961, Grey 1987), but they will not be discussed, as they are not within the
scope of this thesis.
10
Rapid palatal expansion forces
“If the applied transverse forces are of sufficient magnitude to overcome the
bioelastic strength of the sutural elements, orthopedic separation of the maxillary
segments can occur” (Bell, 1982). According to Isaacson et al (1964) and Isaacson
and Ingram (1964), forces of 100N or more can be reached with multiple turns of the
activation screw. Force levels tend to accumulate with multiple turns and can reach
as high as 34lbs (Zimring et al., 1965).
Anatomy of sutural opening
The increase in transpalatal width with RPE treatment is due to both
orthodontic and orthopedic effects. Transpalatal width is gained through a
combination of effects. Orthopedic/skeletal expansion involves separating the right
and left halves of the maxilla at the mid-palatal suture; orthodontic/dental expansion
results from buccal tipping of the maxillary posterior teeth.
The idea behind the RPE design of rigid fixation is to hold the alveolar
segments firm and reduce or eliminate the buccal crown tipping aspect of RPE
treatment. By using a rigid appliance, tipping of the molars is minimal and produces
an orthopedic, and more stable, expansion of the palate. However, currently there is
no device that can completely eliminate this tipping component.
Anatomically during RPE treatment, the expansion force is applied to the
maxillary bones, which separate and apply force to the palatine bones, which
11
separate and further apply lateral forces to the pterygoid processes of the sphenoid
bone.
(from Timms, 1980)
Since the pterygoid processes are actually part of one bone, the sphenoid cranial
bone, and are not paired bones like the maxillary and palatine, the lateral forces of
maxillary expansion cause the lower portions to splay outward, not separate (Timms,
1980). Physiologically this may rotate the two inferior halves of the maxillary
processes slightly upward and outward (in a ‘splaying motion’) and thus
conceptually rotate the medial superior portions downward while separating. This
may account for the flattening or ‘dropping’ of the palatal vault that has been
described by McCurdy, (1909) Black, (1909), and Haas (1961).
12
During rapid palatal expansion, the two maxillary halves are moved apart (transverse
arrows) so that a lateral bending of the pterygoid process occurs (rotational arrows).
(Holberg et al, 2006)
Lateral bending of the pterygoid process. (Holberg et al, 2006)
13
During RPE treatment the alveolar ridges tip and bend buccally and the teeth both
move bodily and tip. (Bishara and Staley, 1987)
Hicks (1978) used implants to evaluate the tip of the maxillae relative to one
another and found that the tipping is in the range of -1 and 8 degrees. This rotational
tipping may account for the triangular pattern of expansion, i.e., the difference
between expansion at the dental arch and expansion at the nasal base. In the frontal
plane, the RPE separates the two halves of the maxilla superioinferiorly unequally
with the fulcrum of rotation being close to the frontomaxillary suture (Haas, 1961;
Wertz, 1970).
14
Force systems related to midpalatal sutural expansion in the frontal view.
(Braun, 2000)
Krebs (1964) used metal implants in the infrazygomatic ridge and in the alveolar
process lingual to the maxillary canines to evaluate the effects of the RPE. He found
the gain in the width of the dental arch across the molars (7.5mm) to be around twice
that of the basal maxillary segments (3.7mm) and gains at the base of the nasal
cavity was 2.0mm. Filho et al (1995) with 32 young children confirms this
triangular opening pattern in the frontal plane. They evaluated the orthopedic effect
by measuring interprostion, interanterior nasal spine, and internasal widths and found
increases of 4.765mm, 2.656mm, and 2.078mm respectively on a PA ceph. Chung
and Font (2004) also looked at the PA ceph and found maxillary width mean
15
increased 2.28mm, which was 30.1% of the Haas appliance expansion (7.58mm).
These results confirm the triangular opening pattern of the maxilla in the frontal
plane and that the center of rotation is near the frontomaxillary suture (Wertz, 1970)
in young patients. The orthopedic behavior of the maxilla with RPE treatment is a
large width gain at the dentoalveolar region and a diminishing taper at the maxillary
base and nasal cavity as the stress is attenuated.
(Wertz, 1970)
16
Individual variation may be a reflection of the geometric morphology and the
degree of buttressing within circummaxillary structures (Timms, 1980). Also,
individuals have different variations in bone thickness, quality, and elasticity that
cannot be accounted for presently in research.
Is RPE treatment affected by growth?
As mentioned in the previous paragraphs, the bioelastic strength of the
midpalatal suture of a younger individual with little interdigitation is assumed to be
less than that of an older individual whose suture is more interdigitated. Results
from RPE studies have been variable, with some studies showing little to no
expansion in non-growing individuals and other studies showing similar transverse
gains between growing and non-growing individuals. Although the rapid palatal
expander can produce a consistant amount of expansion at the dentoalveolar level at
any developmental stage, some studies argue that if the treatment with RPE occurs
before the peak in pubertal growth, then more skeletal changes are observed over the
long term.
Baccetti et al (2001) looked at treatment timing and RPE therapy and found
that in all groups whose Haas RPE was activated 10.5mm, the maxillary intermolar
width increase was about 9mm. Although all patients treated gained dento-alveolar
arch width, those patients treated with the RPE early (before or during their pubertal
growth spurt, cervical vertebral stage 3 to stage 4) tended to exhibit more significant
and more effective long-term changes at the skeletal level, demonstrated by width
17
gains at the maxillary, latero-nasal, and latero-orbital sutures. Widening of the
maxilla 3.0mm beyond normal at the skeletal level was evident in the early-treated
group, whereas the widening of the late-treated group was only 0.9mm more than
normals.
Baccetti’s results agree with the histological data found by Melsen (1975)
which show increasing interdigitation of the midpalatal suture with increasing age.
Thus it appears as though maxillary separation early with RPE reaches areas that are
superior to the midpalatal suture and that the fulcrum of separation may be as high as
the frontomaxillary suture. When RPE treatment is after the growth spurt, and the
midpalatal suture has presumably increased skeletal calcification, the fulcrum of
maxillary separation seems to be more inferior and nearer to the RPE, as described
by Wertz (1970). Also, the median palatine suture closes from the posterior to the
anterior, meaning that the posterior region ossifies first. This may also restrict the
amount of expansion in some patients who are beginning to mature Cross et al
(2000). With more interdigitation, it can be assumed that more force would be
needed to separate the two halves.
Stability may also be related to age as Wertz and Dreskin (1977) noted
greater and more stable orthopedic changes in patients under the age of 12 years.
Patients who were older tended to lose much of the width increases that were gained
with RPE. However, there is an increasing body of literature which reveals that the
RPE can be used successfully in patients that are slightly older, say those with
permanent dentition and may be up to age 18 years old.
18
Sari et al (2003) found that treating children with RPE in the mixed dentition
lead to more relapse than treatment in the permanent dentition indicating that early
treatment is not necessarily more stable than later treatment. Also, they found there
was a larger angular increase between the two halves of the maxilla suggesting that
early expansion did not lead to more parallel opening, but instead lead to more
bending of the alveolar structures.
A study conducted by Baydas et al (2006) looked at metabolic activity (via
bone scintigraphy) of the craniofacial regions during RPE treatment in a sample of
female young adult patients aged 16-18 years old who had completed growth based
on their hand-wrist films. The authors found that with RPE treatment, metabolic
activity was the highest around the midpalatal suture and also found statistically
significant increases in metabolic activity around the zygomatic, sphenoid, nasal, and
maxillary bones. These results indicate that the metabolic activity that occurs in the
midpalatal suture area is indicative of new bone formation in the region. These
results must, however, be viewed with caution because even though there is
metabolic activity and/or new bone formation surrounding the midpalatal region, that
is not a direct indication of expansion in the area.
Again, individual variation plays a role in the flexibility of the suture and
some older individuals may gain significant intermolar width with late RPE
treatment. Despite some studies which support the use of RPE in older, non-growing
individuals, it is generally thought that after growth has ceased and the suture has
fused, it is best to use surgically assisted rapid palatal expansion to avoid adverse
19
consequences such as severe dental tipping, which is unstable, and gingival recession
on posterior teeth (Vanarsdall, 1994). The optimal age for expansion is before 13 to
15 years of age (Bishara et al 1987).
Orthodontic expansion measurements.
Before computed tomography, the maxillary intermolar width was measured
primarily in two ways, (1) internally on dental casts, using soft tissue landmarks, or
(2) laterally on PA cephalometric radiographs, using the lateral/buccal surface of the
maxillary first molars. Measuring width increases using the crowns of the molars
combines true orthopedic movement along with buccal tipping, thus any numbers
recorded cannot eliminate buccal tipping as a component.
(1) Intermolar width measured of dental casts
a) Timms (1980) looked at 32 children (20 girls, 12 boys) with an age range of
8.2-24 years (ave age 11-14) and found with RPE treatment, there was an
intermolar arch width gain of 6.5-9.5mm as measured from the lingual
cervical margin of the first permanent molars.
b) Adkins et al (1990) used plaster casts for measurements using the most lingual
points at the gingival margin of the molars. They found that with RPE
treatment on 21 patients (14 female, 7 male, age range 11.6-17 years old) the
maxillary intermolar increase was 6.5mm at the first molars.
20
c) Chung and Font (2004) found that in 20 children (14 female, 6 male) with a
mean age of 11.7 years, with RPE treatment the mean maxillary intermolar
width (as measured from the “dotted cusp tips of the first molars”) increased
7.92mm as measured on the dental casts. Since the mean expansion of the
Haas appliance was 7.58mm, they attribute 0.34mm (4.3%) of the expansion
to buccal crown tipping. However, since they are using the crown itself as
part of the measurement, they cannot eliminate buccal tipping. When
measuring at the lingual crest level they may have had more accurate
measurements.
Intermolar width in the bucco-lingual dimension is measured at various locations on
the casts and may account for some of the variation seen in the measurements.
(2) Intermolar width measured on PA cephs
a) Baccetti et al (2001) looked at treatment timing and RPE therapy and found
that in all groups whose Haas RPE was activated 10.5mm, the maxillary
intermolar width was about 9mm. Both early and late maturing groups
demonstrated expansion at the alveolar level as measured on the PA ceph with
a gain of approximately 3.2-3.5mm over controls.
b) Cross et al (2000) found that mean upper molar width (as measured from the
lateral aspect of the mx first molar on the PA ceph) significantly increased by
21
a mean of 5.5mm with RPE treatment in a population of 20 females and 5
males with the average age of 13.4 years.
c) Da Silva Filho et al 1995 evaulated 32 children (gender not identified, mean
age 8 years old) with a Haas expander and found that the distance between the
buccal surfaces of the molars of anchorage was statistically significant with a
mean expanded difference of 5.5mm (with a range of 1-9mm).
Garib et al (2005) used computed tomography to measure the internal
maxillary widths and measured the maxillary width between the lingual alveolar
crests at the middle of the maxillary molar. They found that the dental arch at the
lingual alveolar crest level displayed increases in width of approximately 4.3mm.
And that the transverse dimensions of the entire maxilla expanded in a triangular
shape, similar to results described earlier. The significant disadvantage to their study
was that their Hyrax appliance sample size was only four female patients (average
age 12.6 years).
Orthodontic expansion and buccal tipping
This study is not focused on the details of buccal tipping, however a follow-
on study measuring the amount or degree of buccal tipping in these patients would
be interesting. This data could be correlated to Garib et al. (2005) data on buccal
tipping. A brief review of measurements of buccal tipping is included for
educational purposes.
22
Wertz and Dreskin (1977) state that “as buccal teeth are moved laterally, they
become inclined to the buccal as a result of the arcing of the bones themselves, some
alveolar bending, and tipping of teeth.” They believe uprighting molars after
expansion may account for the measured loss of arch width seen post-treatment.
Adkins et al. (1990), using the Hyrax appliance, measured crown tipping on
plaster casts with a tangent line to the cusp tips of the molars and showed that buccal
crown tipping with expansion was highly variable, some with little to no tipping and
some with tipping of more than 15 degrees. This variation ranged from 6+/-6
degrees. They found no statistically significant relationship between tipping of the
anchor teeth and age, initial palatal width, and amount of expansion.
Studies using the Haas expander report maxillary molar buccal tipping
amounts varying from none Lima et al. (2005) to 6 degrees (McNamara et al 2003)
to 24 degrees Filho et al. (1995). Chung and Font (2004) subtracted the mean
increase in intermolar width (7.92mm) from the mean expansion of the Haas
appliance (7.58mm) and the difference (0.34mm) is the amount of expansion they
attribute to buccal crown tipping (4.3%).
Garib et al. (2005), in a three dimensional media most similar to this study,
used computed tomography to evaluate buccal tipping in 4 female patients with
banded RPEs (Group II only), with a mean age of 12.6 years, and found that in the
Hyrax patients first premolars and molars (anchorage teeth) did not exhibit any
significant change in inclination, i.e. buccal tipping, with inclination increases of 2.3
degrees and 2.5 degrees respectively. However, both tipping and bodily translation
23
occurred in maxillary second premolar teeth with inclination increases of 6.7
degrees. They theorized that the first premolars and first molars might not tip due to
their being banded, and thus there was more bodily movement of these teeth. The
differences in inclination found in the second premolars might be due to forces
placed on the crown generating a buccal moment and therefore buccal tipping.
Does the palatal vault height change with rapid palatal expansion?
From the early to mid 1900’s, it was believed that the palatine processes were
lowered as a result of the expanding alveolar processes; rapid palatal expansion
caused the lowering of the roof of the palatal vault (McCurdy, 1909; Black, 1909).
Haas (1961) concurred with this belief. Pfaff (1905) studied air flow through the
nasal passage with expansion and believed that expansion lowered the palatal vault,
induced straightening of the nasal septum, and increased air volume.
Davis and Kronman (1969) revealed changes in the palatal vault structure
with tracings of pre and post expansion models of twenty-six Caucasian children
who had RPE therapy. The tracings were made by sectioning the casts through the
mesiobuccal cusps of the first molars and also through the tips of the cuspids and
then tracing the palatal configurations. They concluded that the roof of the vault does
not lower as a result of expansion. Instead, palatal height appears to remain
relatively constant, although flattening slightly.
Linder-Aronson and Lindgren (1979) after examining plaster casts and lateral
cephalometric x-rays of 16 girls and 23 boys concluded that the height of the palatal
24
vault was 1.6mm larger at the end of the observation period, but they attributed that
result to growth rather than the treatment effect (even though their subject age range
was 10.6-21.5 and presumably some patients were no longer growing). Additionally,
this study states that there was no relationship found between inter-molar width and
the height of the palatal vault, and this result was in agreement with Linder-Aronson
and Aschan (1963) stating that the height of the palatal vault was not influenced by
RPE treatment.
Volume of the palatal area is relevant because an increase in volume could
result in more room for the tongue. Brodie (1950, 1954) stated that patients with
constricted maxillary arches tended to carry the tongue in a low position. When the
tongue has more room, the tongue more likely to stay in the palatal region, and this
may possibly reduce low and/or forward tongue position.
Relapse
Stabilizing the suture after expansion allows the tissues to reorganize and all
the expansion force to dissipate. Any residual force that remains after retention is
removed may cause the tissues to rebound, thus losing intermolar width gained by
the RPE. Hicks (1978) reported that relapse is related to the retention protocol. If
the device was removed immediately after expansion and the expanded area not
retained, relapse could be as much as 45% of the initial expansion. Recommended
retention periods after RPE treatment are three to six months to allow for bony
infilling of the separated suture (Gill et al, 2004; Bishara et al, 1987).
25
Device
Cone-beam CT’s are becoming more common in the clinical dental practice
due to their cost, access, ability to visualize pathology in three dimensions (Nakajima
et al, 2005), and decreased overall effective absorbed dose of radiation (E) for the
same diagnostic yield of information. Imaging of a maxillomandibular volume with
the NewTom 3G results in an E of 57uSv (Ludlow et al, 2005). Medical CT’s have a
much higher E, with the maxilla at 1400uSv and a maxillo-mandibular CT of
2100uSv (Ngan, et al., 2003).
Traditional film panoramic radiographs result in an E of 6uSv and a full
mouth series has a range of E from 33-84 uSv (Danforth and Clark, 2000) to 14-100
uSv (Gibbs, 2000) depending on variables such as film speed, technique, kVp, and
collimation. Lateral cephalometric films are approximately 5-7uSv, PA cephs are 5-
7uSv, occlusal films are 5uSv, and a TMJ series is 20-30uSv (Mah, 2006).
Therefore, when comparing the radiation dose from the NewTom 3G (at 57uSv) to
the equivalent films that would be necessary to include the same information
(average = pano 6+FMX 59+lat ceph 6+PA ceph 6+one occlusal 5+TMJ series 25=
107uSv) the radiation dose for traditional radiographs is almost double that of the
cone-beam CT.
Scanning times with cone beam CT’s are slightly longer than traditional
radiographs with maxillomandibular volume imaging times of between 10-90
seconds. Traditional radiographs give us a 2-dimensional image of the area of
interest, in particular the lateral ceph or the PA ceph will only provide a
26
superimposed view of the palatal area. Cone-beam CT provides 3-dimensional data
(a stack of images) which allows us to measure not only distances but areas and
volumes.
Recent studies have attempted to evaluate three-dimensional effects of rapid
palatal expansion, but these evaluation methods have used two-dimensional
cephalometric films. Lateral cephalograms have been used to assess sagittal and
vertical changes and postero-anterior cephalograms have been used to assess
transverse changes due to RPE treatment (Cross et al, 2000; Chung et al, 2004).
However, this data cannot accurately depict the detailed three-dimensional changes
that occur in the maxilla with rapid palatal expansion.
Significance
With the age range of the patient population used in this study, we can
assume the patients are still growing and/or the palatal suture has not fully calcified
(Bishara et al., 1987). Rapid palatal expansion increases maxillary arch width with a
combination of both orthodontic (tipping and bodily translation) and orthopedic
(bony separation and remodeling at the suture) effects. The effects of arch wire
treatment alone is orthodontic only. Therefore, we can evaluate the RPE effects of
orthopedic change in the experimental patients and evaluate whether these changes
increase the volume within the palatal vault region over that which would be
normally seen with regular orthodontic treatment.
27
Hypothesis
The null hypothesis is that there is no volumetric change in the maxillary
region between patients with rapid palatal expansion and controls. The alternative
hypothesis is that the CT morphologic measurements of volume within the maxillary
region will be significantly different in RPE treated patients than non-RPE treated
patients.
Subjects and Methods
All clinical treatment was performed at the Graduate Orthodontic Clinic at
the University of Southern California. Sixteen healthy patients (mean age 12.6
years, range 8.9-15.10 years; 5 male, 11 female) who required RPE due to a
unilateral or bilateral crossbite and orthodontic treatment and had cone-beam CT
imaging were selected for the study. Fifteen controls were selected for similar age
and gender (mean age 13.2, range 10.6-15.7 years; 4 male, 11 female), had
orthodontic treatment only (no RPE), and also had a cone-beam CT scan. All
patients were thought to be growing prior to fusion of the midpalatal suture, based on
age and clinical judgment. All the patients were in the late transitional or early
permanent dentition stage. Patients did not have any craniofacial abnormalities,
surgical treatment or extraction treatment.
Patients treated with the RPE had a Hyrax palatal expander banded on the
maxillary first premolars and first molars. Patients were monitored weekly for
appropriate activation of the appliance. Expanders were turned 1-2 times per day
28
until the required expansion, i.e., slight overcorrection of the cross-bite was achieved
(average time 4-6 weeks) and then were stabilized. The RPE (or a TPA) was used
for retention for at least 3 months post-expansion. Most patients with RPE did not
have any orthodontic treatment until after the fixed retention period, but several did
have some appliances placed (like a 2x4) during the fixed retention period. Control
patients started orthodontic treatment at approximately the same time as the
experimental group started expansion therapy. Newtom scans on all patients were
taken as part of progress records at the midpoint in treatment, which ranged from 8
months to 2 years (average 15 months). The patient was asked to put their head in
Frankfort horizontal for the Newtom scan, however there was a variation in their
head position between scans (difference in angulation).
Images were imported in vWorks 5.0 (Cybermed, Seoul, Korea) and the
following measurements were performed on each scan: volumetric, width and height
of the palatal region. The angulation was defined as the angle between ANS-PNS
and the vertical in the vWorks image. We performed two kinds of volumetric
measurements: a crude squared-shape prism (Vol_crude) and an anatomically well-
defined hand-traced volume (Vol_anatomic).
The crude prism was defined as follows: First we found the mid-sagittal
plane going through the anterior mid-point of the two upper incisors and the
posterior mid-point of the spine (Fig. 1). We defined the borders of the crude prism
as (a) superior border was defined on the mid-sagittal image as the most superior
point of the palatal vault (Fig. 2); (b) inferior border was defined as the inferior CEJ
29
of the central incisors (Fig. 2); (c) the anterior border was defined as the inferior CEJ
of the central incisors (Fig. 2); (d) the posterior border was PNS/most posterior
boarder of the bony hard palate (Fig. 2); (e) the lateral borders were defined on the
axial section by the most mesial portion of the second molars at the CEJ (Fig. 3).
Figure 1. Midsagittal section: Midsagittal plane
30
Figure 2. Midsagittal section; Crude volume
Figure 3. Axial section: Crude volume
31
Figure 4. Coronal section: Crude volume
The anatomically well-defined volume started with the crude box and one
operator removed the bony and teeth voxels (Figs 5-7).
Figure 5. Midsagittal section: Anatomical volume
32
Figure 6. Axial section: Anatomical volume
Figure 7. Coronal section: Anatomical volume
33
To define the width of the palate we used the hard tissue internal palatal
landmarks. We measured the mean transpalatal width between the lingual alveolar
crests at the level of the first molars for all patients (experimental and controls),
similar to the protocol described in Garib et al (2005) (Fig. 8). By using hard tissue
landmarks, the possibility of gingival thinning or recession affecting the data is also
eliminated.
Figure 8. Coronal section at the level of the first molars: Width measurement
To measure height of the palatal vault, we measured both the absolute highest
point in the palatal vault area (regardless of the anterior-posterior point between the
34
incisors and PNS) (named tallest) (Fig. 9) and the palatal height at a fixed plane (the
line defined in the mid-sagittal image as the projection of the coronal plane going
through the palatal root of the first molars (named height) (Fig. 9).
Figure 9. Midsagittal section: Height measurements; Tallest and height
Height and width were measured twice and the mean was used in this study.
Statistical Analysis
Because the variables under study were normally distributed, we compared
the baseline characteristics using the Pearson chi-square test for sex and independent
t-tests for the continuous variables. Absolute volume change for crude and anatomic
35
palatal volumes was defined as the difference between the measurements in the
beginning and progress scans. Percent change in palatal volumes (crude and
anatomic) was computed by subtracting the beginning scan palatal volume from the
progress scan palatal volume and dividing by the beginning scan volume and
multiplying by 100. This was done because the two groups differed significantly on
palatal volume at baseline. We conducted multiple linear regression to test whether
the absolute and percent change in palatal volumes differed between the
experimental and the control groups. We also conducted linear regression adjusting
for the baseline palatal volume.
Results
Baseline: The experimental and the control group were similar in age and sex
distribution (Table 1). However, they differed significantly on palatal crude and
anatomic volumes before treatment. The controls had statistically significantly larger
palatal volumes before treatment (p=0.005). The two groups did not show
statistically significant differences in mean palatal width, height or tallest height
(p>0.05). There was no significant difference in angulation between the beginning
and progress scan for each patient (paired t-test p=0.0653). The mean difference in
angulation between scans was 0.19 degrees for the controls and 0.83 for the RPE
patients. There were no significant differences in angulation between the two groups
(p=0.25).
36
Table 1. Comparison between RPE and controls on baseline and end of treatment
characteristics
*
Parameter Experimental
group (RPE)
Control group P-value
§
Age (yrs) 12.6 (1.63) 13.2 (1.43) 0.32
Sex
Female 11 (68.7%) 11 (73.3%)
Male 5 (31.3%) 4 (26.7%) 0.78
Before treatment parameters
Palatal crude volume
(mm
3
)
20177 (5792.5) 26230 (5398.7) 0.005
Anatomic vol. (mm
3
) 13797 (4453.0) 17750 (2735.5) 0.006
Width (mm) 34.3 (3.65) 35.8 (3.17) 0.23
Height (mm) 11.9 (3.18) 12.9 (2.72) 0.37
Tallest height (mm) 12.5 (3.03) 13.3 (2.45) 0.41
After treatment parameters
Palatal crude volume
(mm
3
)
24722 (6296.4) 29035 (5679.2) 0.055
Anatomic vol. (mm
3
) 16504 (4188.6) 19585 (3432.5) 0.03
Width (mm) 37.2 (4.05) 36.7 (2.99) 0.70
Height (mm) 13.4 (3.05) 14.1 (2.90) 0.50
Tallest height (mm) 13.6 (2.92) 14.5 (2.67) 0.35
*
Data presented as N (%) for sex and mean (standard deviation) for the continuous
variables.
§
P-values obtained from Pearson chi-square test for sex and independent t-tests for
the continuous variables.
37
After treatment: Controls had a palatal crude volume 4,313 mm
3
larger than
RPE patients after treatment but this difference was marginally non-significant
(p=0.055), however the two groups showed a statistically significant difference in
anatomic palatal volume after manual removal of the bone and tooth structures in the
images (p=0.03).
There was no significant difference in palatal vault width or height, as
measured either from the tallest palatal vault location or at a fixed plane defined by
the first molars.
Changes during treatment: There was a significant difference in palatal crude
(p=0.011) and anatomic (p=0.036) volume percent change between the control and
RPE groups. The percent of change in crude palatal volume was 11.2% in controls
and 24.6% in the RPE group. Thus the difference in volume change before and after
treatment between the two groups was 13.4%. The results were similar for the
anatomic palatal volume (Table 2).
There was a significant difference in width percent change, as measured
between the maxillary first molars, between the control and experimental groups
(p=0.027). The mean width increase for the orthodontic only cases was 0.86mm,
whereas the mean width increase for the RPE cases was 2.86mm, a difference of
2mm.
There was no significant difference in palatal vault height change (measured
as absolute or percent change), as measured either from the tallest palatal vault
location or at the plane of the first molars, between the two groups.
38
Table 2. Comparison between RPE and controls absolute and percent change in
characteristics over treatment
Parameter Experimental
group (RPE)
Control group P-value
(t-test)
Percent change
Palatal Crude volume (%) 24.61 (16.40) 11.23 (9.83) 0.011
Anatomic vol. (%) 23.35 (21.97) 10.22 (7.39) 0.036
Width (%) 8.65 (9.53) 2.53 (3.56) 0.027
Height (%) 14.62 (19.83) 10.2 (12.52) 0.47
Tallest height (%) 10.10 (17.13) 9.53 (12.87) 0.92
Absolute change
Palatal Crude volume
(mm
3
)
4545 (2829.1) 2804 (2370.8) 0.075
Anatomic vol. (mm
3
) 2707 (2251.9) 1835 (1396.7) 0.209
Width (mm) 2.86 (2.98) 0.86 (1.2) 0.022
Height (mm) 1.47 (1.99) 1.22 (1.45) 0.70
Tallest height (mm) 1.07 (1.70) 1.19 (1.50) 0.83
Discussion
Cone-beam CT’s are becoming more common in clinical dental practice due
to their cost, access, ability to visualize pathology in three dimensions,
1
and
decreased overall effective absorbed dose of radiation (E) for the same diagnostic
yield of information. In this study, cone-beam CT enabled an entirely new set of
data to be visualized and calculated: the palatal volume.

1
Nakajima A, Sameshima GT, Arai Y, Homme Y, Shimizu N, Dougherty H Sr. Two-and Three-
dimensional Orthodontic Imaging Using Limited Cone Beam-Computed Tomography. Angle Orthod
2005;75:895-903.
39
At the beginning of treatment, the control group had significant larger palatal
volume, as expected, even though statistically, this was not due to a larger molar-to-
molar width or larger height. During the experimental period, both groups went
through normal growth (age range from 8.9 years to 15.7 years).
At the end of the experimental period, the palatal volume of the RPE group
increased by 23.35% compared to 10.22% in controls, but the RPE group was still
statistically significantly smaller in volume as compared to the controls. All the
individual parameters such as AP length, height, and width across

the

first molars
were not statistically significantly different after treatment. Summarized, this means
the palatal volume of the RPE group is still smaller than the control group even
though the component parts measured were not smaller than controls. This result
may be due to several factors. Even though the widths, heights, and AP lengths of
both groups are similar after treatment, the mean values of the controls are larger in
every area (except molar-to-molar width) and all together this may make the control
group’s palatal volume larger. Also, since the volume is a three-dimensional
characteristic, the actual palatal shape may be different between the RPE treatment
group and the controls and account for the volumetric difference noted at the end of
treatment. The increased AP length in the RPE group resulting in no statistical
significant difference after treatment does not mean that the actual length of the
maxilla in the anterior-posterior dimension grew more with the RPE therapy. It is
more likely due to the tipping effect of the 2x4 appliances on the maxillary anteriors
in the RPE group.
40
To explain why there was a statistically significant difference in percent
change in palatal volume but not an absolute change (the progress volume – the
beginning volume), it must be remembered that the percent change was calculated
as: (the absolute change) x 100 divided by (the beginning value). Therefore, group
A might have the same absolute change of volume as group B, but group A might
still have bigger percent change if its initial volume was smaller than the one of
group B.
Though there were no statistical significant differences in molar-to-molar
width before or after treatment, its percent change and absolute change were
statistically significantly different. The increase in molar-to-molar width is most
likely due to the RPE effect itself and/or the buccal tipping effect on the molars,
which could range from 0 degrees to 24 degrees (Da Silva Filho et al., 1995;
McNamara, 2003).
Hesby et al. (2006) reported molar-to-molar width increases of 0.67mm in
normal, untreated patients between the ages of 12.9-16.5 years. This study found
that orthodontic treatment alone increased the mean molar-to-molar width
approximately 0.86mm. Subtracting normal, untreated patient values from
orthodontically treated patient values (0.86mm-0.67mm) reveals there may be minor
orthodontic expansion from arch wires during orthodontic treatment (0.19mm), but
this is unlikely to be due to any sort of skeletal expansion. RPE treatment, in this
study using CT scans, increased the molar-to-molar width 2.86mm while studies
using PA cephalometric molar-to-molar measurements report width increases of 3.2
41
to 5mm over controls (Chung, 2004). Garib et al. (2005) using a CT scan and having
the most similar protocol to our own, reports a 4.3mm increase at level of lingual
alveolar crest with RPE treatment. This difference may be explained by the fact that
we have a much larger sample size than Garib (n=4).
This study found no significant differences in palatal vault height from
beginning to progress records. If the maxillary bones splay with RPE treatment, they
do not rotate enough to lower the palatal vault and decrease the volume found in the
palatal vault region. Furthermore, these results could not confirm the findings of
Linder-Aronson and Lindgren

(1979) which states that the palatal vault height
increases. Since Linder-Aronson used casts for their palatal vault height
measurements, they may have seen increases in height due to thinning of the palatal
soft tissues due to growth or stretching of these tissues during RPE treatment.
Assumptions
1. All patients were growing based on age and clinical judgment.
2. The determination the lowest part of the box used the CEJ of the central
incisors.
3. All angulations could correct for head position differences.
4. Required expansion was achieved by ‘slight overcorrection of the cross-bite,’
which is based on clinical judgment and is a variable and subjective amount.
5. Measurements were accurate and reproducible.
42
Limitations
1. There were a limited number of records that satisfied the strict criteria set for
the study.
2. The study only used orthodontic patients as opposed to the general
population.
3. Measurements were subject to human error.
Conclusions
1. RPE treatment was effective in increasing the palatal volume of patients with
constricted maxillary arches, but those volumes, even after RPE treatment,
remained smaller than those of orthodontically treated patients.
2. The increase in palatal volume of RPE patients is mostly due to an increase in
molar-to-molar width and canine-to-canine width. There is no significant
change in palatal vault height or AP length due to RPE treatment.
43
Bibliography
Adkins, MD, Nanda, RS, Currier, GF. Arch Perimeter Changes on Rapid Palatal
Expansion. AJODO 1990;97:194-199.
Baccetti, T., Franchi, L., Cameron, CG, and McNamara, JA. Treatment Timing for
Rapid Maxillary Expansion. Angle Orthod 2001;71:343-350.
Baydas, B, Yavuz, I, Uslu, H, Dagsuyu, IM, Ceylan I. Nonsurgical Rapid Maxillary
Expansion Effects on Craniofacial Structures in Young Adult Females. Angle
Orthod 2006;76:759-767.
Bell, RA. A Review of Maxillary Expansion in Relation to Rate of Expansion and
Patient’s Age. AJO 1982;81:32-36.
Biederman, W. A Hygienic Appliance for Rapid Expansion. JCO 1968;2:67-70.
Bishara, SE and Staley, RN. Maxillary Expansion: Clinical Implications. AJODO
1987;91:3-14.
Bjork A, Skieller V. Growth in the Width of the Maxilla Studied by the Implant
Method. Scand J Plast Reconstr Surg 1974;8(1-2):26-33.
Black, NM. The Relation Between Deviation of the Nasal Septum and Irregularities
of the Teeth and Jaw. JA-MA 1909;52:943-945.
Brodie, AG. Anatomy and Physiology of Head and Neck Musculature. AJO
1950;36:831-844.
Brodie, AG. The Fourth Dimension in Orthodontia. Angle Orthod 1954;24:15-30.
Braun, S, Bottrel, JA, Lee, KG, Lunazzi, JJ, Legan, HL. The Biomechanics of Rapid
Maxillary Sutural Expansion. AJODO 2000;118:257-261.
Brust, EW, McNamara, JA Jr. Arch Dimensional Changes Concurrent with
Expansion in Mixed Dentition Patients. Michigan Growth Series. Ann Arbor:
Center for Human Growth and Development; University of Michigan; 1995.
Cross, DL and McDonald JP. Effect of Rapid Maxillary Expansion on Skeletal,
Dental, and Nasal Structures: a Postero-Anterior Cephalometric Study. Euro J
Orthod 2000;22:519-528.
44
Chung, CH and Font, B. Skeletal and Dental Changes in the Sagittal, Vertical, and
Transverse Dimensions After Palatal Expansion. AJODO 2004;126:569-575.
Danforth, RA, Clark, DE. Effective Dose from Radiation Absorbed During a
Panoramic Examination With a New Generation Machine. Oral Surg Oral Med
Oral Pathol Oral Radiol Endod 2000;89(2):236-243.
Davis, WM and Kronman, JH. Anatomical Changes Induced by Splitting of the
Midpalatal Suture. Angle Orthod 1969;39:126-132.
Enlow, DH. Facial Growth, 3
rd
Ed., W.B. Saunders Company, Philadelphia, 1990.
Filho, RMAL, Lima, AC, Ruellas, ACO. Spontaneous Correction of Class II
Malocclusion After Rapid Palatal Expansion. Angle Orthod 2003;73:745-752.
Garib, DG, Henriques, JFC, Janson, G, Freitas, MR, Coelho, RA. Rapid Maxillary
Expansion – Tooth Tissue-borne vs. Tooth Borne Expanders: A Computed
Tomography Evaluation of Dentoskeletal Effects. Angle Ortho 2005;75:548-
557.
Gianelly, AA. Rapid Palatal Expansion in the Absence of Crossbites: Added Value?
AJODO 2003;124:4:362-65.
Gibbs, SJ. Effective Dose Equivalent and Effective Dose: Comparison for Common
Projections in Oral and Maxillofacial Radiology. Oral Surg Oral Med Oral
Pathol Oral Radiol Endod 2000;90:538-545.
Gill, D., Naini, F., McNally, M., Jones, A. The Management of Transverse
Maxillary Deficiency. Dent Update 2004;31:516-523.
Gray, LP. Rapid Maxillary Expansion and Impaired Nasal Respiration. Ear Nose
Throat J 1987;66:248-251.
Haas, AJ. Rapid Expansion of the Maxillary Dental and Nasal Cavity by Opening the
Midpalatal Suture. Angle Orthod 1961;31:73-90.
Haas, AJ. The Treatment of Maxillary Deficiency by Opening the Midplatal Suture.
Angle Orthod 1965;35:200-217.
Haas, AJ. Palatal Expansion: Just the Beginning of Dentofacial Orthopedics. AJO
1970;57:219-255.
45
Hicks, EP. Slow Maxillary Expansion: A Clinical Study of the Skeletal Versus
Dental Response to Low-Magnitude Force. Am J Orthod 1978;73:121-141.
Hesby, RM, Marshall, SD, Dawson, DV, Southard, KA, Casko, JS, Franciscus, RG,
Southard, TE. Transverse Skeletal and Dentoalveolar Changes During Growth.
AJODO 2006;130(6):721-731.
Holberg, C., Rudzki-Janson, I. Stresses at the Cranial Base Induced by Rapid
Maxillary Expansion. Angle Orthod 2006;76:543-550.
Howe, RP, McNamara, JA Jr, O’Connor, KA. An examination of Dental Crowding
and its Relationship to Tooth Size and Arch Dimension. Am J Ortho
1983;83:363-73.
Isaacson, RJ, Wood, JL, Ingram AH. Forces Produced by Rapid Maxillary
Expansion. Part 1. Design of the Force Measuring System. Angle Orthod
1964;34:256-260.
Isaacson, RJ, Ingram, AH. Forces Produced by Rapid Maxillary Expansion. Part II.
Forces Present During Treatment. Angle Orthod 1964;34:261-270
Krebs, A. Midpalatal Suture Expansion Studied by the Metallic Implant Method
over a Seven Year Period. Eur Orthos Soc 1964;40:131-142.
Kurol, J, Berglund, L. Longitudinal Study and Cost Benefit Analysis of the Effect of
Early Treatment of Posterior Crossbites in the Primary Dentition. Eur J Orthod
1992;14:173-179.
Kutin, G, Hawes, RR. Posterior Crossbites in the Deciduous and Mixed Dentitions.
Am J Orthod 1969;56:491-504.
Lagravere, MO, Major, PW, Flores-Mir, C. Long-term Dental Changes After Rapid
Maxillary Expansion Treatment: A Systematic Review. Angle Orthod
2005;75:151-157.
Lima, AL, Filho, RMAL, and Bolognese, AM. Long Term Clinical Outcome of
Rapid Maxillary Expansion as the Only Treatment Performed in Class I
Malocclusion. Angle Orthod 2005;75:372-376.
Linder-Aronson, S, Aschan, G. Nasal Resistance to Breathing and Palatal Height
Before and After Expansion of the Median Palatine Suture. Odont Revy
1963;14:254-270.
46
Linder-Aronson, S, Lindgren J. The Skeletal and Dental Effects of Rapid Maxillary
Expansion. Brit J Orthod 1979;6:25-29.
Ludlow, JB, Brooks, SL, Davies-Ludlow, LE, Howerton, B. Dosimetry of 3 CBCT
Units for Oral and Maxillofacial Radiology. International Association of
Dentomaxillofacial Radiology. 15
th
Congress: Cape Town, South Africa, 2005.
Mah, J. X-Ray Imaging and Oral healthcare, 2006.
McCurdy, SL. Discussion: Separation of Upper Maxillae. J Am Med Assoc
1909;52:1030-1031.
McNamara, JA. Maxillary Transverse Deficiency. AJODO 2000;117:567-570.
McNamara, JA Jr. The Role of the Transverse Dimension in Orthodontic Diagnosis
and Treatment. In: McNamara, JA Jr, ed. Growth Modification: What Works,
What Doesn’t and Why? Monograph 36, Craniofacial Growth Series, Center for
Human Growth and Development. Ann Arbor: The University of Michigan;
1999.
McNamara, JA Jr., Baccetti, T, Franchi, L, Herberger, TA. Rapid Maxillary
Expansion Followed by Fixed Appliances: A Long-Term Evaluation of Changes
in Arch Dimensions. Angle Orthod 2003;73:344-353.
Melsen, B. Palatal Growth Study on Human Autopsy Material: A Histologic
Microradiographic Study. AJO 1975;68:42-54.
Nakajima, A, Sameshima, GT, Arai, Y, Homme, Y, Shimizu, N, Dougherty, H Sr.
Two- and Three-dimensional Orthodontic Imaging Using Limited Cone Beam-
Computed Tomography. Angle Orthod 2005;75:895-903
Ngan, DC, Kharbanda, OP, Geenty, JP, Darendeiller, MA. Comparison of Radiation
Levels from Computed Tomography and Conventional Dental Radiographs.
Aust Orthod J 2003;19:67-75.
Pfaff, W. Stenosis of the Nasal Cavity Caused by Contraction of the Palatal Arch and
Abnormal Position of the Teeth: Treatment by Expansion of the Maxilla. Dental
Cosmos 1905;47:570-573.
Roden-Johnson, D. The Effects of Buccal Corridor Spaces and Arch Form on Smile
Esthetics. AJODO 2005;127:343-350.
47
Sari, Z, Tancan, U, Usumez, S, and Basciftci, FA. Rapid Maxillary Expansion. Is it
Better in the Mixed or in the Permanent Dentition? Angle Orthod 2003; 73(6):
654-661.
Timms, DJ. The Dawn of Rapid Maxillary Expansion. Angle Ortho 1999;69(3):247-
250.
Timms, DJ. A Study of Basal Movement with Rapid Maxillary Expansion. AJO
1980;77:500-507.
Wertz, RA. Skeletal and Dental Changes Accompanying Rapid Midpalatal Suture
Opening. AJO 1970;58:41-66.
Wertz, R and Dreskin, M. Midpalatal Suture Opening: A Normative Study. AJO
1977;71:367-381.
Will, L. Transverse Maxillary Deformities: Diagnosis and Treatment. SROMS
1996;5:1-28.
Vanarsdall, RL. Periodontal/Orthodontic Interrelationships. In: Graber, TM,
Vanarsdall, RL, editors. Orthodontics: Current Principles and Techniques, 2
nd
ed. St. Louis: CV Mosby; 1994. p.712-749.
Zimring, JF, Isaacson, RJ. Forces Produced by Rapid Maxillary Expansion. III.
Forces Present During Retention. Angle Ortho 1965;35:178-186

Abstract (if available)

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

A cone beam CT evaluation of the maxillary dento skeletal complex after rapid palatal expansion

PDF

Reprogramming the NiTi expander: an alternative to conventional rapid and slow maxillary expansion modalities for the treatment of patients with cleft lip and palate

PDF

The effect of cone beam computed tomography (CBCT) imaging on orthodontic diagnosis and treatment planning

PDF

Three dimensional analysis of maxillary retromolar alveolar bone before and after en‐masse distalization

PDF

Detrimental effects of dental encroachment on secondary alveolar bone graft outcomes in the treatment of patients with cleft lip and palate: a cone-beam computed tomography study

PDF

Operator-determined and reoriented natural head position in three-dimensional imaging

PDF

Comparative facial attractiveness in two and three dimensions

PDF

The relationship of the forehead to the maxillary central incisor in adult white females: an evaluation of Andrews Element II analysis

PDF

Genetic review of mouse and human cleft lip and palate

PDF

Comparison between tooth mesiodistal angulation measurements from constructed panoramic images and three-dimensional volumetric images

PDF

A cone beam-CT evaluation of the proximity of the maxillary sinus to commonly used TAD sites

PDF

Proper mesio-distal angulation and bucco-lingual inclination of the whole tooth in three-dimensional space -- a standard for orthodontic patients

PDF

Slow maxillary expansion for the treatment of unilateral crossbite in pre-adolescents: a long-term retrospective study of the changes in arch dimension

PDF

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

PDF

Cone-beam computed tomography images: applications in endodontics

PDF

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

PDF

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

PDF

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

PDF

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

PDF

Prevalence and distribution of facial alveolar bone fenestrations in the anterior dentition: a cone beam computed tomography analysis

Asset Metadata

Creator Gohl, Elizabeth (author)

Core Title A three-dimensional computed tomography comparison of the maxillary palatal vault between patients with rapid palatal expansion and orthodontically treated controls

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 07/05/2007

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

Tag 3D imaging,maxillary expansion,maxillary volume,molar width,OAI-PMH Harvest,palatal height,RPE

Language English

Advisor Enciso, Reyes (committee member), Mah, James (committee member), Sameshima, Glenn T. (committee member)

Creator Email gohleliz@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m583

Unique identifier UC1336565

Identifier etd-Gohl-20070705 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-514537 (legacy record id),usctheses-m583 (legacy record id)

Legacy Identifier etd-Gohl-20070705.pdf

Dmrecord 514537

Document Type Thesis

Rights Gohl, Elizabeth

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu