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Comparative study of Caucasian and Hispanic mandibular clinical arch forms

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Comparative study of Caucasian and Hispanic mandibular clinical arch forms

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COMPARATIVE STUDY OF CAUCASIAN AND HISPANIC
MANDIBULAR CLINICAL ARCH FORMS

by

Amy Aland Gimlen

____________________________________________________________________

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

May 2007

Copyright 2007 Amy Aland Gimlen
ii
DEDICATION
To my Husband
Scott Burrin

iii
ACKNOWLEDGEMENTS
A special thank you to:
Dr. Sameshima
Dr. McLaughlin
Dr. Nojima
My Co-Residents
Ana Gimlen
April Gimlen
Guy Gimlen

iv
TABLE OF CONTENTS
Dedication ii
Acknowledgements iii
List of Tables v
List of Figures vi
Abstract vii
Chapter 1: Introduction 1
Chapter 2: Review of Literature 3
Chapter 3: Hypothesis 22
Chapter 4: Materials and Methods 24
Chapter 5: Results 28
Chapter 6: Discussion 43
Chapter 7: Assumptions 47
Chapter 8: Limitations 48
Chapter 9: Summary 49
Chapter 10: Conclusions 50
Bibliography 51

v
LIST OF TABLES
TABLE 1: Sample Characteristics 29
TABLE 2: Comparison of Variables between Caucasian and 31
Hispanic Class I, II, and III Samples

TABLE 3: Comparison of Frequency Distribution of 34
Square, Ovoid, Tapered Arch Forms between
Caucasian and Hispanics

TABLE 4: Comparison of Variables between Caucasians and 40
Hispanics for Square, Ovoid and
Tapered Arch Form Groups

vi
LIST OF FIGURES
FIGURE 1: Twelve clinical bracket points and 4 linear and 26
2 proportional measurements of arch dimension

FIGURE 2: Class I Caucasian Arch Form Frequency 35

FIGURE 3: Class I Hispanic Arch Form Frequency 35

FIGURE 4: Class II Caucasian Arch Form Frequency 36

FIGURE 5: Class II Hispanic Arch Form Frequency 36

FIGURE 6: Class III Caucasian Arch Form Frequency 37

FIGURE 7: Class III Hispanic Arch Form Frequency 37

FIGURE 8: Caucasian Arch Form Frequency 38

FIGURE 9: Hispanic Arch Form Frequency 38

vii
ABSTRACT
Introduction: The purpose of this study was to clarify morphologic
differences between Caucasian and Hispanic mandibular clinical arch forms in Class
I, II, and III malocclusions. Methods: The study included 60 Class I, 50 Class II, and
50 Class III patients from each ethnic group. Orthodontic study models were
photocopied, scanned, digitized, and measured (4 linear and 2 proportional). The
dental arches were classified into square, ovoid, and tapered forms to compare the
frequency distributions between the 2 ethnic groups. Results: The Caucasians had a
significantly smaller arch dimensions than the Hispanics, except for canine depth.
Caucasians had a higher frequency of tapered arch form whereas Hispanics had a
high frequency of square arch form. Conclusion: There is a significant difference
between frequency of arch forms and arch dimensions of Hispanic and Caucasian
patients. Specifically, there is no arch form unique to any of Angle classification or
ethnic group.
1
Chapter 1: INTRODUCTION
With the advent of superelastic wires and the esthetic preference of
orthodontist for broad smiles (Roden-Johnson D, 2005) it is common practice to alter
arch form without regard for the stability of the long term result. Current theory
states that treatment arch forms should be based on the pre-treatment shape of the
mandibular arch (Little, 1990), and the maxillary arch should be coordinated to this
in order to increase the chance of a stable result. It is more reasonable to have
several preformed arch wires in which to choose from that best fits the patient’s pre-
treatment arch form and taking into consideration both the patient’s ethnicity and
malocclusion (Nojima, 2001).
Two studies have addressed ethnicity and the frequency of the common arch
forms in different ethnic populations (Nojima, 2001, Kook, 2004). They found
significant differences in the frequency of arch forms between two different Asian
populations and Caucasian patients as well as differences in arch form between
malocclusion types and yet still it is rare for orthodontists to consider ethnicity when
choosing a treatment arch form.
Many orthodontic practices in the US are treating an increasing Hispanic
population and little is known of the arch forms of Hispanic patients. The objective
of this study was to determine the characteristics of clinical mandibular arch shapes
in Hispanic and Caucasian patients with Class I, Class II and Class III malocclusions,
testing the hypothesis that there is a difference in arch form and dimension between
the two ethnicities.
2
1. Determine if there is a difference in the arch form between Caucasian and
Hispanics.
2. Determine if there is a difference in the arch dimensions between Caucasian
and Hispanics.
3. Determine if there is a difference in the arch form between malocclusion
types: Class I, Class II and Class III.
4. Determine if there is a difference in the arch dimensions between
malocclusion types: Class I, Class II and Class III.

3
Chapter 2: REVIEW OF THE LITERATURE
NORMAL DEVELOPMENT OF DENTAL ARCHES
Development of the maxillary and mandibular arches begins early in
development, 17 day post-conception, with a down-growth of neural crest cells into
the surface ectoderm. The face begins to develop during the 5-7
th
week from four
primordial processes that surround a central depression called the oral pit. There is a
single process above the pit called the frontonasal process, two maxillary processes
lateral to the pit and the mandibular prominence below the pit. Throughout the first
trimester these processes fuse to form the face. The maxilla and mandible both
develop intramembranously and continue to grow by primary and secondary
displacement (Proffit, 2000).
Dental development begins between the 27
th
and the 37
th
day post-conception
when two epithelial bands are formed, one in the maxillary and one in the
mandibular arch. From these epithelial bands there is a down growth of epithelium
into the underlying mesenchyme which forms the dental lamina. The dental lamina
is the origin of both the deciduous and permanent dentition. As the teeth grow and
develop the adjacent tissues also are developing from the dental follicle. The
alveolar bone develops intramembranously and during development attaches to the
developing maxilla and mandible. Alveolar bone is the support structure for the
dentition and is defined only after the tooth erupts and disappears when the tooth is
lost, and is the key to arch form due to the fact it follows the position of the teeth
(Bernard, 1997).
4
As arches grow and as teeth erupt into the mouth arch dimensions change.
Moorrees in 1969 stated that there is a large amount of variation between
individuals, regarding arch form, but there is a central tendency for an increase in
intermolar width in the transition from primary to permanent dentition and even
increasing up to 18 years old, particularly in males. Intercanine width increases from
primary to permanent dentition, but after eruption of the permanent canines the width
no longer increases. Into the 30s and 40s patients arch depth tends to decrease
(DeKoch, 1972). After the age of 12, there is little to no increase in arch length or in
arch perimeter (Sinclair, 1983). Stanton in 1922 studied the natural variability in the
population and found that most humans with a normal occlusion vary 5mm in width,
from one side to the midpalatal suture, and 13mm in length, from buccal groove to
upper incisal edge, (Stanton, 1922). Arch length tends to decrease during the
transition from primary to permanent dentition and continues to decrease with age
(Shapiro, 1974).
Hellman studied the role of tooth size and its relationship to arch form in
humans and apes and found no relationship between the size of teeth and the arch
form (Hellman, 1919).
The impact of the role of soft tissue in the development of arch form has been
controversial. Scott stated that a case can be made for the importance of the pressures
exerted by the adjacent muscular tissues of the tongue, lips and cheeks in
determining arch form, but the fact that arch form is determined before tooth
eruption and that it depends for its final development on the direction and extent that
5
of alveolar process growth, would indicate that under normal conditions the soft
tissue plays a minor role in its determination” (Scott, 1957). Alternatively, Brader in
1972 stated that “the primary determinants of arch form morphology are the (muscle)
tissue forces of the resting state in contradistinction to the intermittent forces of
muscles in functioning states” (Brader, 1972). Currier postulated that due to the
shape of the arches the buccinator had a greater effect on the maxillary dentition in
the second and third molar region creating a more elliptical shape to the arch.
Mandibular arch shape was more dictated by occlusion rather than the effect of the
tongue or other circumoral musculature (Currier, 1969). “It is generally accepted that
the dental arch form is initially shaped by the form of underlying bone, and then after
eruption of the teeth, the shape becomes influenced by the oral musculature”
(McLaughlin, 2001)
Symmetry between contralateral sides of the arch is generally not found.
White found that only 6.25% of natural arch forms can be defined as symmetric
(White, 1978).
When comparing the size of the individual arches the maxillary tends to be
wider than the mandibular arch in normal occlusions allowing for proper
intercuspation of teeth, overbite and overjet. Fujita found in 2002 that “ the
association between the upper and lower dental arches did not vary by more than
0.3mm, but showed consistent lateral gaps of about 4.3mm for the opposing canines
and 2.8mm for the molars” (Fujita, 2002).

6
DIFFERENCES AMONG ANGLE CLASSIFICATION
Braun in 1998 found there were differences in arch form between the
different Angle classifications such that all maxillary arch depths were similar, but
when compared to Class I the Class III’s were wider distal to the lateral-canine area
and Class II’s were narrower distal to the lateral-canine area. Comparing the
mandibular arches to the Class I casts the Class III casts showed a smaller arch depth
and greater arch width while the Class II’s had both a reduced arch with and depth
(Braun, 1998). Nojima and Kook found that Class II canine depth was greater than
in Class I samples. The Class II sample showed the smallest canine and molar width
to depth ratio, followed by Class I then Class III (Nojima, 2001, Kook, 2004). Kook
found that in Class II sample there was an increased tendency for a tapered arch form
in comparison to Class I arches and Class III sample had the highest frequency in the
square arch form (Kook, 2004).

GENDER DIFFERENCES
There is a difference in normal growth of the mandible and maxilla between
males and females. More width growth is seen in the maxilla (3mm) then the
mandible (2mm), from ages 7-12. After 12 years old there is only growth in males.
Male jaws tend to be wider than female jaws (Moorrees, 1969, Lee RT, 1999, Knott,
1972). Intercanine width and depth are not significantly related to sex (Raberin,
1993). Ferrario in 1994 studied the gender differences in the shape of the dental
arches and found that males had similar shaped maxillary and mandibular arches and
7
are superimposable. The maxillary arch shows a translation anteriorly to allow for
proper overjet. The female dental shape showed a tendency towards posterior
crossbite. The female arches were significantly smaller primarily in the maxillary
arch, while the mandibular arches were more similar in size (Ferrario, 1994).

ETHNIC DIFFERENCES
Aitchison in 1964 showed that there are ethnic differences in arch form.
Caucasians typically have a narrow palate and uneven arch form, where Australian
Aborigines have a large U-shaped arches, African Americans have wide palates and
large jaws, and the Mongoloid complex has a tendency towards a parabolic arch
(Hanihara, 1967). Taner in a study of Turkish patients found that pre-treatment
maxillary arch forms were mostly tapered and mandibular arch forms were tapered
and narrow tapered (Taner, 2004). In a study comparing Japanese mandibular arch
form with Caucasian arch form, by Nojima in 2001, found that Caucasians primarily
had tapered and ovoid arch forms, with a significantly reduced arch width and
increased arch depth, where Japanese had significantly greater number of ovoid and
square arch forms (Nojima, 2001). Kook in 2004, studied the difference between
Korean and North American white populations, he found that in Caucasian
populations the tapered arch form predominated and the square arch form
predominated in Korean populations, where the Korean arches tended to be larger
and deeper than Caucasian arches (Kook, 2004). Irey compared an Indian
population and a Chinese population; he found that the Chinese sample had
8
significantly wider arches than the Indian population (Irey, 1998). In a study of three
pacific populations, Kasai found that Fijians upper arch was more V-shaped that was
wider and longer than the aboriginal population, which had more of a U-shaped arch,
and where the Japanese population laid in between (Kasai, 1997).

IDEAL ARCH FORM/ SHAPE OF THE NORMAL HUMAN DENTAL ARCH
Since the time of Edward Angle, one ideal arch form that can be universally
applied to all human dental arch forms have been sought out, with little success.
Angle himself believed there was a “true line of occlusion” (Angle, 1907). Many
people have tried to describe the shape of the normal human arch form, such as semi-
ellipsoid (Black, 1894), parabolic (Angle, 1899), catenary, hyperbolic (Scott, 1957),
U-shaped (Martin, 1914), horseshoe shaped (Hrdicka, 1920), beta function, conic
sections, spline curves (Fujita, 2002) under the following assumptions:
1. there must be an algebraic or geometric formula to determine ideal arch form
2. all arch forms are the same shape the only variation is their size
3. arch forms are symmetrical
4. mathematical equations used make it impossible to produce asymmetry
(White, 1978).
Currently, it has not been proven that there is one universal arch form for all
human dental arches. Below are some of the more common arch form shapes:

9
Catenary Curve
MacConaill and Scher described the normal dental arches conform to a catenary
curve or to a regular deviation from that curve (MacConaill, 1944). A catenary
curve is created when a piece of chain, typically 200mm in length, is attached to a
horizontal cross bar where one end is movable to change the distance between the
free ends of the chain. For the maxillary arch “the apex of the of the curve lies over
the gingival papilla situated between and on the lingual side of the first incisors, and
the limbs of the chain lie over the central fossae of the first permanent molars. In the
case of the lower arch, the apex of the catenary is adjusted to lie over the point of
contact between the incisive edges of the first incisors, while the two limbs lie over
the buccal cusps of the first permanent molars.” While not all teeth may it in the
exact catenary curve, primarily the third molars that typically lie lingual to the curve,
the basic overall arch shape is catenary in form. This theory is justified by Scott
stating that “if teeth removed from the alveolar process, they would remain united to
one another by the transeptal fibers and by the attachment of the gingival to the
cementum of the cervical region through the gingival fibers and through the
epithelial attachment. The teeth, therefore, are united to one another in the form of a
chain and in each jaw make up a series of connected units.” A variety of human
dental arches can be described by the catenary curve, of a constant length, but a
variable distance between the ends of the chain, including the shape of the dental
lamina, the deciduous dentition, the permanent dentition, the lower border of the
mandible, as well as variation of dental arches between humans (Scott, 1957).
10
Bonwill-Hawley
Hawley in 1955 proposed a method to determine and ideal arch. The arch
was based on an equilateral triangle with a leg representing the intercondylar width
and the lower anterior teeth were aligned on the arc of the circle, whose radius was
determined by the combined width of the lower incisors and canines with the
premolars and molars aligned with the second and third molar turned toward the
center (Hawley, 1925). Bonwill believed the arc of the anterior teeth could be
related to an equilateral triangle. Most preformed arch wires, from orthodontic
supply companies are based on the Bonwill-Hawley design, even though this theory
has been largely discredited (White, 1978).

Brader
Brader in a 1972 paper concluded that “normal dental arches of the sample
more closely approximated curves with elliptic properties than they did a parabola,
the catenary curve or other curves.” The trifocal ellipse is derived form three
internal foci and is a closed, compounded elliptic curve that closely describes the
facial surfaces of the maxillary arch. His theory was justified by the formula PR=C,
which accounts for the pressures of the tissues on the shape of the teeth in an arch
(Brader, 1972). Selection of the Brader arch form is based on the second molars, the
shape is related to the facial surfaces of the teeth and the mandibular arch is always
one size smaller than the maxillary arch form. A common problem with this theory
is when it is applied it results in a severe narrowing of the cuspids (White, 1978).
11
Mathematical Calculations of Arch Form
Mathematical calculations of arch forms have been studied extensively
including quadratic equations (Biggerstaff, 1972), cubic spline, conic sections, beta
functions and polynomial curves.
BeGole described a mathematical model which takes into account
asymmetric in modeling of dental arch forms which is based on the cubic spline.
The cubic spline is based on data points called knots where a physical spline, such as
thin flexible wood or plastic is held over graph paper and forced through the knots.
This study used computer generated splines in order to study maxillary arch forms
which resulted that there was little discrepancy between the natural arch form and the
spline, including any asymmetries (BeGole, 1980).
Conic sections as described by Sampton, in 1981, addressed the modeling of
dental arches by mathematical formulas, in this case conic section, as well as
addressing the variation among the human population in order to show the average
shape of the dental arch and the variation from that shape (Sampton, 1981). Conic
sections are a family of the most simple plane curves including circles, ellipses,
parabolas and hyperbolas (De la Cruz, 1995).
Braun described the human arch form as a beta function curve in 1998. He
found an average correlation of 0.98 with a standard deviation of 0.02 for all three
Angle classifications as well as both the maxillary and mandibular arch. This
method does underestimate the arch width at the second molars by 1mm and the arch
depth by 1.5mm but can be compensated for in the calculations (Braun, 1998).
12
Uzaka et al found “dental arch forms with normal occlusion were best
expressed by the fourth-order polynomial curves, 15% by second-order polynomials,
and 13 % by sixth-order polynomials” (Uzaka, 2000). Fujita found that fourth-order
polynomials had the best fit (Fujita, 2002).
Overall, “mathematical modeling of dental arch forms is that dental arches
that are identified to have the same type of mathematical form of function do not
necessarily share the same pattern” (Fujita, 2002).

Segment concept in arch patterns
The segment concept of arch form design was theorized by Robnett in 1980,
where in stead of trying to fit one shape or mathematical formula to determine the
shape of the “normal” human dental arch he based his concept on developing a finite
number of arch patterns that can be adapted to the majority of patients. The pattern
is based on canine width, molar width and the sum of the mesiodistal diameters of
the six mandibular anterior teeth and is used to predict the basic shape of the
mandibular arch. This theory allows the practitioner to determine the canine width at
the end of treatment (Robnett, 1980).

Computer-derived Arch Design
Rocky Mountain Data Systems developed a computer based program that
takes into account facial form, intermolar width, intercanine width and arch depth
too predict a best fit mandibular arch form (White, 1978).
13
A study of best fit of the most common arch forms was undertaken by White
in 1978 and he found that 8% of Bonwill-Hawley had a “good fit” and 52% were
“poor fits,” the Brader design had a good fit of 12.5%, catenary had a good fit of
27% and equal poor fits and 92% of the Rocky Mountain Data Systems had a
moderately good fit of 92% of mandibular arch forms. While there is great
variability of fit of the common theoretical arch shapes White observed that the
“teeth apparently arrange themselves in an arc that is dictated mainly by the osseous
bases of the jaws” (White, 1978).
While numerous studies have been undertaken to study the ideal or normal
human arch form no one arch form has been proven to be universal for all patients.
Chuck in 1934 was the first to predict that there were three main arch forms seen in
the human population: tapered, square and ovoid (Chuck, 1934) where as Raberin in
1993 predicted there were five main arch forms that the natural variability in the
human population could mostly account for (Raberin, 1993).

ALTERATION OF ARCH FORM
Expansion of arches
Expansion of the dental arches has been controversial since the beginning of
orthodontics. Angle believed that there should be “a full complement of teeth and
each tooth shall be made to occupy its normal position-normal occlusion” (Hine,
1990) therefore his treatment philosophy was to expand the dental arches in order to
fit all the teeth in the mouth. Tweed, a student of Angle, although achieving good
14
results, saw that his cases were relapsing post treatment. This was dissatisfactory to
Tweed and he retreated many of his cases with extraction of premolars to gain space
in lieu of expansion.
Regardless if a patient receives extraction or non-extraction treatment it is
routinely found that there is some expansion of the lower canines and relapse of that
expansion is common. Bishara, 1973 found in a study of 30 first premolar extraction
cases that averaged 1.2 years out of retention that 71.4% of any expansion that
occurred in the lower canines resulted in relapse, with less relapse found in the upper
arch. Little in 1981 found in a follow up of 65 cases with extraction of first
premolars that the lower canine width was increased 1mm during treatment in 60 %
of the cases and after treatment intercanine width decreased in 60 out of the 65 cases,
and the constriction was usually more than 2mm.
It is currently believed that stable expansion of the maxillary arch can be
achieved. In a study by Moussa, in 1995, they looked at 55 patients with non-
extraction edgewise therapy as well as rapid maxillary expansion. After an average
of 6 years post-retention the patients showed an average expansion of 2.7mm in the
maxillary canines and 4.6mm in the maxillary first molars, which showed that the
arch expansion was stable post treatment (Moussa, 1995).
Current thought is that expansion of the mandibular arch is not stable, except
for in a few rare instances. Selwyn-Barnett believed that it is possible to expand the
lower arch in Class II division 2 situations, where the lower dentition is tipped
lingually. The lower dentition could be positioned such that the take up the space
15
where the previously lingually inclined maxillary incisors were positioned, without
disturbing the position of the lips (Selwyn-Barnett, 1991). The resultant uprighting
of the dentition increases the intercanine width, an inviolate dimension, but in the
case of Class II division 2 patients this increase in dimension is more stable than an
increase in intercanine dimension in Class I or Class II division 1 patients (Shapiro,
1974).
Lee in 1999 hypothesized that expansion in the situation of scissorbite can be
stable if it does not encroach on the space for the lips and cheeks. Expansion of the
mandibular arch as routine treatment can lead to lower incisor relapse, periodontal
breakdown (Mershon, 1936), and crowding in the buccal segments.
McNamara stated in 1993, if expansion is attempted in a patient “it seems
logical to consider increasing arch size at a young age so that skeletal, dentoalveolar,
and muscular adaptations can occur before the eruption of permanent dentition.” In
a study of the Frankel appliance, of 11 patients, with patients in post-retention of at
least 4 years showed a minimal amount of expansion in the lower 3-3 of 1.25mm, 4-
4 of 4.35mm, 5-5 of 2.3mm and 6-6 of 2.5mm (McNamara, 1993, Hine, 1990).

Extraction vs. Non-Extraction
During extraction treatment there are more changes in the dimensions of the
arches than with non-extraction treatment. Obviously arch length is decreased
significantly more in extraction patients, simply due to a reduction in tooth mass
(Shapiro, 1974). Intercanine width, in both non-extraction and extraction cases,
16
increases during treatment 1-2 mm, but in extraction cases the canines are also
moved posteriorly within the bone to a wider part of the arch (Burke, 1998). Still
there is a tendency in both extraction and non-extraction cases for the intercanine
with to relapse towards pre-treatment dimensions (Bishara, 1973, Shapiro, 1974).
Intermolar width in the extraction group decreased during treatment as opposed to
non-extraction saw an increase in intermolar width during treatment that relapsed
post-treatment to its original pre-treatment dimension (Shapiro, 1974).

ARCH WIRES
Arch Wire Expression: Extraction versus Non Extraction
In a study by Huntley, in 1989, he treated 63 cases with the same arch form,
regardless of pre-treatment arch form or extraction/non-extraction treatment plan (26
with extraction of lower first premolars, 17 with extraction of second premolars and
20 non-extraction). The arch wires achieved full expression in the lower anterior
region and close to full expression in the posterior region (Huntley, 1989).
After treatment and at least one year post-retention Tang studied 46 of the
cases to evaluate the stability of the cases. In the non-extraction sample, there was
only a very limited effect on the intercanine and intermolar distances, the premolars
were expanded 1.21mm in the first premolar and 0.93mm in the second premolar.
Overall, the arch remained stable post-retention and the expansion was maintained in
the premolar region. In the extraction sample, there was a small amount of
17
expansion in the canines, which subsequently relapsed, the molars were expanded,
but that expansion remained stable (Tang, 1991).
It can be concluded by this data that it is very important in extraction cases to
maintain pretreatment arch form.

Commercially available preformed arch wires
While the pre-treatment mandibular model is the gold standard to base
treatment arch forms from it is not always feasible or possible, as in the case of
nickel titanium wires, to adapt each treatment arch wire to the pre-treatment arch
form. There are many commercially available arch forms and in a study by Braun, in
1999, evaluates some of the popular nickel titanium preformed arch wires, Ormco
(Tru-arch II medium and Align medium, Ormco, Orange, CA) and Unitek
(Orthoform I and II, 3M Unitek, Monrovia, CA). Overall, Braun concluded that
preformed arch wires did not emulate the natural human arch form, as calculated
from the beta function curve. “The average canine width exceeded the natural
canine width by 5.95mm in the mandibular arch and 8.23mm in the maxillary arch.
The corresponding mandibular first molar and maxillary first molar widths exceeded
the natural human first molar arch width by 0.84mm and 2.68mm, respectively.” If
these nickel titanium wires are used in initial leveling and aligning and finishing
based on pre-treatment arch form is done in stainless steel wires there would be a net
round tripping effect on the dentition or if the increase in width is maintained it could
18
lead to a decrease in stability and impact facial esthetics and lip support (Braun,
1999).
Felton, in 1987, reviewed 17 commercially available arch wires and
compared them to an untreated normal sample, Class I malocclusions and Class II
malocclusions. He found that not one of the commercially available arch wires was
sufficient for more than one third of any sample. He found that Vari-Simplex
(Ormco, Orange, CA) and the Par (3M Unitek, Monrovia, CA) arch forms were very
similar and this general shape represented 44% of the untreated sample and 60% of
the Class I sample (Felton, 1987). Engel in 1979 looked at 9 commercially available
arch wires and concluded that the preformed arch wires in his study were not suitable
for many orthodontic cases (Engel, 1979).

Arch Coordination
The maxillary and mandibular arches must fit together in a consistent
relationship to achieve ideal intercuspation, canine and molar relationship as well as
proper overbite and overjet. The majority of the literature states the pre-treatment
mandibular arch form is the best to determine the treatment arch forms and the
maxillary is coordinated to the mandibular arch.
Contradicting the majority, Chuck in 1933 stated that the “mandibular arch
wire is formed is not based upon measurements taken from the mandibular teeth, but
is patterned after the maxillary chart. It is constructed inside of the maxillary chart,
using the same center for the primary circle, but a radius that is one-eighth shorter
19
than the maxillary.” Chucks construction of arch form was based on the Bonwill-
Hawley arch (Chuck, 1934).

STABILITY/ POST-TREATMENT CHANGES
The goal of orthodontic treatment is to achieve an esthetic, functional and stable
result. Stability of the end result has proven to be the most difficult goal to achieve
and prediction of which patients will remain stable and the ones who will relapse is
not currently possible (Little, 1981). Arch form is vital to proper treatment planning
and the attainment of a functional correction (Currier, 1969).
Stability of an orthodontic case has been linked to two main factors- the teeth
balanced with intraoral forces as well as the dentition centered in alveolar bone.
Angle, 1907, believed that there should be a balance soft tissue and muscular forces,
lips, cheeks and tongue, on both sides of the dentition. Halazonetis concluded in
1994 that “it is unlikely that the lips and cheeks can be encroached on to a significant
extent.” This was tested by Weinstein in 1967 found that tooth position could be
influenced by changing the natural pressure of the adjacent tissues and when the
encroachment was removed the teeth returned in the direction of their original
position, therefore supporting the balance of force hypothesis (Weinstein, 1967).
In regards to stability, there are studies that contradict each other. Taner in 2004
found that in a Turkish population 76% of the changes in arch form in the maxillary
arch and 67% in the mandibular arch was maintained 3 years post-treatment (Taner,
2004). A study was undertaken by De la Cruz where arch forms were changed
20
during treatment and the long term stability was looked at. He concluded that though
there was a large amount of individual variation, any changes that were made in arch
form during treatment tended to relapse toward their pre-treatment shape and the
greater the treatment change tendency for post treatment change was greater (De la
Cruz, 1995). In a study by Felton, cases that arch form was changed 70% returned to
their original arch form during long term post-treatment evaluation. Riedel states
that “arch form, particularly in the mandibular arch, cannot be altered by appliance
therapy” (Reidel, 1956). Therefore, using one arch form for all patients will tend to
change the original arch form and leads to an unstable result (Felton, 1987).

CRANIOFACIAL DIFFERENCES AMONG CAUCASIAN AND HISPANIC
POPULATIONS
There are known differences between populations of different descent. In a
study by Garcia, in 1975, studying the differences in lateral cephalometric norms
between a Mexican American and Caucasian population found that Mexicans were
more bimaxillary prognathic than Caucasians (Garcia, 1975). Phelan in 2004
showed there was a difference between Mexican mestizos and American whites with
Class II division 1 malocclusions. While the maxillomandibular relationship was
similar between the groups the Mexican subjects had a greater protrusion of jaws,
less divergence in the cranial base (SN-FH angle) and greater vertical tendencies
(MPA, Y-axis and palatal plane) (Phelan, 2004). Mongoloids which are
predecessors to modern Hispanic populations have been found to have parabolic arch
21
forms (Hanihara, 1967) where as Caucasians typically have a narrow palate and an
uneven arch form (Aitchison, 1963).
There are dental characteristic differences between these two populations as
well. Mexican Americans have a significantly higher amount of incisor irregularity
than do Caucasians (Buschang, 2003). Phelan found that there is more dental
protrusion seen in Mexican mestizos than American whites in both the maxillary and
mandibular incisors (Phelan, 2004). Mexicans have larger tooth sizes than do
Caucasians (Bishara, 1989). When comparing overall relationships between the
mandibular and the maxillary teeth, Caucasians showed a smaller overall ratio than
Hispanics, indicating that Caucasians mandibular teeth are smaller than Hispanics
(Smith, 2000).

22
Chapter 3: HYPOTHESES
Research hypotheses
1. There is a significant difference in the arch form between Caucasian and
Hispanics.
2. There is a significant difference in the arch dimensions between Caucasian
and Hispanics.
3. There is a significant difference in the arch form between malocclusion types:
Class I, Class II and Class III.
4. There is a significant difference in the arch dimensions between malocclusion
types: Class I, Class II and Class III.

23
Null hypotheses
1. There is no significant difference in the arch form between Caucasian and
Hispanics.
2. There is no significant difference in the arch dimensions between Caucasian
and Hispanics.
3. There is no significant difference in the arch form between malocclusion
types: Class I, Class II and Class III.
4. There is no significant difference in the arch dimensions between
malocclusion types: Class I, Class II and Class III.

24
Chapter 4: MATERIALS AND METHODS
The Caucasian cases included pre-treatment mandibular orthodontic study
models of 60 Class I, 50 Class II, and 50 Class III cases from the University of
Southern California, Department of Orthodontics and a private practice in San
Diego. The Hispanic cases included pre-treatment mandibular orthodontic study
models of 60 Class I, 50 Class II and 50, Class III cases from University of Southern
California, Department of Orthodontics. All mandibular study models were subjected
to the following inclusion criteria:
1. Class I, II, and III malocclusions of a dentoalveolar nature
2. Permanent dentitions with normal tooth size and shape
3. 3mm of crowding or less
4. Without restorations extending to contact areas, cusp tips, or incisal edges.
The occlusal surfaces of the mandibular models were photocopied (Canon PC
940, Canon, Lake Success, NY), with a ruler included for magnification correction.
The photocopied images were scanned (Epson 3100C, Epson, Long Beach, Ca),
digitized (Microsoft Digital Image Pro 9, Microsoft, Redmond, Wa), calibrated and
measured (Rootometer, J. Johnson).
Four linear measurements were recorded (Figure 1):
- Intercanine width (distance between the canine clinical bracket
points)
- Intermolar width (distance between the first molar clinical bracket
points)
25
- Canine depth (shortest distance from a line connecting the canine
clinical bracket points to the origin between the central incisors)
- Molar depth (shortest distance from a line connecting the first molar
clinical bracket points to the origin between the central incisors)
Two proportional measurements were calculated (Figure 1):
- Canine width to depth ratio (ratio of the intercanine width and the
canine depth)
- Molar width to depth ratio (ratio of the intermolar width and the
molar depth)

Templates (OrthoForm, 3M Unitek, Monrovia, CA) were overlaid onto each
patient’s photocopied mandibular arch form. Best fit was determined from first
premolar to first premolar and classified into square, ovoid, and tapered arch forms
(FIGURE 1).

FIGURE 1: Twelve clinical bracket points and 4 linear and 2 proportional
measurements of arch dimensions. 1, intercanine width; 2, intermolar width; 3,
canine depth; 4, molar depth.

26
27
STATISTICAL ANALYSIS
The means and standard deviations were calculated for each sample. Ethnic
differences in arch dimensions were analyzed by unpaired t-tests and Levene’s test
for equality of variance. The chi-square test was used to determine differences in
frequency distribution of the 3 arch forms. The subjects were then regrouped into
the 3 arch forms and the arch dimensions were re-analyzed using unpaired t-tests and
Levene’s test for equality of variance. The levels of significance were p < .05 (*), p
< .01 (**), and p < .001 (***), in addition p ≥ .05 was not considered significant.
All models were evaluated for inclusion criteria and were measured by one
examiner. The method error was assessed by statistically analyzing the difference
between duplicate measurements, by the same examiner, were taken 2 weeks apart
on 20 casts selected at random the intraclass correlation coefficients are .924 for
canine width, .967 for molar width, .839 for canine depth and .924 for molar depth.

28
Chapter 5: RESULTS
In order clarify morphologic differences between Caucasian and Hispanic
mandibular clinical arch forms in Class I, II, and III malocclusions we analyzed 320
mandibular orthodontic study models and a statistical analysis was completed.

SAMPLE CHARACTERISTICS (TABLE 1)
The mean (SD) age of the Caucasian patients was 15.35 (5.15) years and of
the Hispanic patients was 15.94 (5.64) years. Both groups had more females than
males, while the Caucasian group had 84 females and 76 males the Hispanic group
had 91 females and 69 males.

29
TABLE 1: Sample Characteristics
Caucasian
Sample n Males Females
Mean
Age
(Years)
SD
(Years)
Class I 60 23 37 16.6 5.9
Class
II 50 26 24 14.7 4.74
Class
III 50 27 23 14.5 4.32
Total 160 76 84 15.4 5.15
Hispanic
n Males Females
Mean
Age
(Years)
SD
(Years)
Class I 60 21 39 15 5
Class
II 50 28 22 16 6
Class
III 50 20 30 17 6
Total 160 69 91 16 6

30
COMPARISON OF VARIABLES BETWEEN CAUCASIAN AND HISPANIC
CLASS I, II, AND III GROUPS (TABLE 2)
The results of the unpaired t-tests showed that the Caucasian group had a
smaller intercanine width (highly significant) and intermolar width (very highly
significant) in all three Angle classifications. In the Class I group, the Hispanic group
had a significantly larger molar depth and canine width-to-depth ratio. In the Class II
group, the Caucasians had a significantly smaller molar width-to-depth ratio. When
Class I, II, and III malocclusions were combined there were statistically significant
differences in all measured variables between the Caucasian and Hispanic ethnic
groups, with the exception of canine depth. The differences between the groups
indicate that, with the exception of canine depth, the Hispanic group had
significantly larger mandibular arch form dimensions.

31
TABLE 2: Comparison of Variables between Caucasian and Hispanic
Class I, II, and III Samples

CLASS I
SAMPLE

Caucasian
(n=60)
Hispanic
(n=60)
Variable Mean SD Mean SD P value
Intercanine
width (mm) 29 1.26 30.05 2
0.001
**
Intermolar
width (mm) 49.2 2.29 51.34 2.82
<0.001
***
Canine
depth (mm) 6.29 0.88 6.1 1.31 0.34
Molar
depth (mm) 26.8 1.62 27.65 2.19 0.02*
Canine
W/D ratio 4.68 0.56 5.23 1.82 0.03*
Molar W/D
ratio 1.84 0.11 1.86 0.17 0.24
CLASS II
SAMPLE

Caucasian
(n=50)
Hispanic
(n=50)
Mean SD Mean SD P value
Intercanine
width (mm) 29 1.22 30 2
0.003
**
Intermolar
width (mm) 49 2.52 52 2
<0.001
***
Canine
depth (mm) 7 1.12 6 1 0.07
Molar
depth (mm) 27 1.97 28 2 0.09
Canine
W/D ratio 4 0.7 5 1 0
Molar W/D
ratio 2 0.16 2 0 0.01 *

32
TABLE 2, Continued
CLASS IIi
SAMPLE

Caucasian
(n=50)
Hispanic
(n=50)
Mean SD Mean SD P value
Intercanine
width
(mm) 29 1.7 30.7 2.54 0.001 **
Intermolar
width
(mm) 51 2.7 52.8 3.16
<0.001
***
Canine
depth
(mm) 5.7 1.2 5.68 1.01 1
Molar
depth
(mm) 27 2.6 27.5 2.22 0.4
Canine
W/D ratio 5.3 1 5.59 1.19 0.4
Molar
W/D ratio 1.9 0.2 1.93 0.16 0.3
TOTAL

Caucasian
(n=160)
Hispanic
(n=160)
Mean SD Mean SD P value
Intercanine
width
(mm) 29.07 1.39 30.21 2.16
<0.001
***
Intermolar
width
(mm) 49.41 2.61 51.93 2.79
<0.001
***
Canine
depth
(mm) 6.26 1.13 6.05 1.24 0.11
Molar
depth
(mm) 27.08 2.07 27.73 2.11 0.01 *
Canine
W/D ratio 4.79 0.85 5.24 1.45 0.001 **
Molar
W/D ratio 1.83 0.17 1.88 0.15 0.01 *

33
COMPARISON OF FREQUENCY DISTRIBUTION OF SQUARE, OVOID AND
TAPERED ARCH FORMS BETWEEN CAUCASIANS AND HISPANICS
(TABLE 3)
The results of the chi-square test were that in both the Class I, Class II, and
the combined (Class I, II, and III) groups there was significant differences in the
frequency distribution of the arch forms between the Caucasian and Hispanic ethnic
groups. In the Hispanic Class I sample, the square arch form was most often seen,
with the tapered and ovoid arch form presenting in equal numbers. In contrast, the
Caucasian Class I sample tapered and ovoid arch forms accounted for over 90% of
the group, the square arch form was rarely seen. The Class II Hispanic group also
presented with a majority of square pre-treatment arch forms, followed by tapered
then ovoid. 96% of the Class II Caucasian group presented with either ovoid or
tapered arch forms, with tapered being the clear majority. In both ethnic groups the
Class III’s presented with a majority of square pre-treatment arch forms, followed by
ovoid then tapered.
The differences among the groups indicate that majority of Hispanic patients
present with a square pre-treatment arch form, followed by approximately equal
numbers of tapered and ovoid. In contrast, Caucasian patients present with a
majority of tapered pre-treatment arch forms, followed by ovoid and then square.

34
TABLE 3: Comparison of Frequency Distribution of Square, Ovoid,
Tapered Arch Forms between Caucasian and Hispanics

Caucasian
Square Ovoid Tapered
Sample n % n % n %
Class I 5 8.3 27 45 28 47
Class II 2 4 18 36 30 60
Class III 22 44 16 32 12 24
Total 29 18.1 61 38.1 70 44

Hispanic

Square Ovoid Tapered P value
Sample n % n % n %
Class I 22 36.7 19 32 19 32 0.001 **
Class II 23 46 11 22 16 32<0.001 ***
Class III 26 52 15 30 9 18 0.7
Total 71 44.4 45 28 44 28
0.00
***

FIGURE 2: Class I Caucasian Arch Form Frequency

FIGURE 3: Class I Hispanic Arch Form Frequency

35

FIGURE 4: Class II Caucasian Arch Form Frequency

FIGURE 5: Class II Hispanic Arch Form Frequency

36

FIGURE 6: Class III Caucasian Arch Form Frequency

FIGURE 7: Class III Hispanic Arch Form Frequency

37

FIGURE 8: Caucasian Arch Form Frequency

FIGURE 9: Hispanic Arch Form Frequency

38

39
COMPARISION OF VARIABLES BETWEEN CAUCASIANS AND HISPANICS
FOR SQUARE, OVOID AND TAPERED ARCH FORMS (TABLE 4)
The results of the unpaired t-tests where the patients were regrouped into
their respective arch forms (square, ovoid, tapered) were that both ethnic groups
showed decreasing intercanine width, intermolar width, canine width-to-depth ratio,
and molar width-to-depth ratio and increasing canine depth and molar depth as the
mandibular pretreatment arch forms changed from square to ovoid to tapered, with
the exception Hispanic ovoid had the largest molar depth.
Between ethnic groups in the square arch form sample the Hispanic patients
had a significantly larger intercanine width and molar depth, while the Caucasian
patients had a significantly larger molar with-to-depth ratio. Both ethnic groups had
a very similar canine width-to depth ratio. Between ethnic groups in the ovoid arch
form sample the Hispanic patients had a significantly larger molar depth and
intermolar width (very highly significant), but both ethnic groups had similar canine
width-to-depth and identical molar width-to-depth ratios. In the tapered arch form
group all variables were significantly larger for the Hispanic patients, except canine
and molar depth, with the intermolar width being very highly significantly different
between ethnic groups.
The differences between the groups indicated that the trend is that
independent of the arch form shape Hispanic patients tend have a larger dimensions
in the mandibular arch in comparison to Caucasians. In addition, characteristics of
each arch form from square to ovoid to tapered show that intercanine and intermolar

40
width decrease and canine and molar depth increase, which leads to a decrease in
both the canine and molar width-to depth ratios.

TABLE 4: Comparison of Variables between Caucasians and Hispanics for
Square, Ovoid and Tapered Arch Form Groups

Square

Caucasian
(n=29)
Hispanic
(n=71)
Variable Mean SD Mean SD
P
value
Intercanine
width
(mm) 30 1.68 31 2.14
0.01
*
Intermolar
width
(mm) 52.2 2 53 2.650.19
Canine
depth
(mm) 5.27 1.11 6 1.290.22
Molar
depth
(mm) 26.2 2.71 27 2.11
0.02
*
Canine
W/D ratio 5.86 0.92 6 1.8 0.94
Molar
W/D ratio 2.01 0.19 2 0.14
0.04
*

TABLE 4, Continued

Ovoid

Caucasian
(n=61)
Hispanic
(n=45)
Mean SD Mean SD
P
value
Intercanine
width
(mm) 29 1.34 30 2 0.06
Intermolar
width
(mm) 50 2.27 52 3
<0.001
***
Canine
depth
(mm) 6 0.76 6 1 0.34
Molar
depth
(mm) 27 1.78 28 2 0.01 *
Canine
W/D ratio 5 0.48 5 1 0.86
Molar
W/D ratio 2 0.11 2 0 0.89

41

42
TABLE 4, Continued
Tapered

Caucasian
(n=70)
Hispanic
(n=44)
Mean SD Mean SD
P
value
Intercanine
width
(mm) 28 1 29 1.66
0.048
*
Intermolar
width
(mm) 48 2 50.5 2.45
<0.001
***
Canine
depth
(mm) 6.9 1.1 6.55 0.95 0.1
Molar
depth
(mm) 28 1.9 27.9 1.710.2
Canine
W/D ratio 4.2 0.6 4.52 0.690.02 *
Molar
W/D ratio 1.7 0.1 1.81 0.13 0.01 *

43
Chapter 6: DISCUSSION
With the advent of superelastic arch wires and the constant concern over a
stable orthodontic result this study addresses the pre-treatment arch form and
dimensions for Hispanic and Caucasian samples, which included all three Angle
malocclusion types. The clinical bracket point was estimated as the most facial
portion of the proximal contact area, as in studies by Nojima and Kook, and arch
form and dimensions were determined (Nojima, 2001, Kook 2004). This study
resulted in clinically significant findings that will aid the orthodontist in both
determining arch form as well as accurate ordering of preformed arch wires.

Arch Dimension- Ethnic Variation
The dimensions of the mandibular dental arch did vary between the Hispanic
and the Caucasian groups. With the exception of canine depth, the Hispanic arches
were significantly larger in all dimensions in comparison to the Caucasian sample.
This held true for all malocclusion types.
When the sample was regrouped based on arch form there were significant
differences between the Hispanic and the Caucasian groups. The square arch form
group showed that Hispanics had a significantly larger intercanine width, molar
depth and smaller molar width to depth ratio. In the ovoid arch form group
Caucasians had a significantly smaller intermolar width and molar depth. In the
tapered group the Hispanic group had a significantly larger canine width, molar
width, canine width to depth ratio and molar width to depth ratio. These findings are

44
consistent with Kook, but are not with Nojima who found, when the samples were
regrouped based on arch form there was no significant difference between the
Japanese and the Caucasian dimensions (Nojima, 2001).

Arch Form- Ethnic Variation
There was not one arch form universal for both groups. The frequency of the
arch forms varied between ethnic groups and also malocclusion type within the
ethnic groups. The majority of Hispanic patients presented with a square pre-
treatment arch form, about 70%, followed by equal numbers of tapered and ovoid.
The Caucasian group’s pre-treatment arch forms were predominantly ovoid or
tapered, about 80%, followed by square.
There is a difference in the frequency of arch forms between different ethnic
populations; this is consistent with the findings of Aitchison, Kook, Nojima, Irey and
Kasai. It is current belief that modern Hispanic populations are descendent from
ancient Asian populations, which could explain why Hispanic arch form frequency is
very similar in frequency to the results of the studies by Nojima and Kook, where
square and ovoid arch forms were predominant.
Findings of this study fit with the current understanding that there are ethnic
differences in the craniofacial complex. There are known differences between
Hispanic populations and Caucasian populations in cephalometric norms (Phelan,
2004), incisor irregularity (Buschang, 2003), tooth size (Bishara, 1998), skeletal
(Garcia, 1975) and dental protrusion (Phelan, 2004). Though these factors do not

45
have a direct impact on arch form, it further proves that there are clear differences in
the craniofacial complex between Hispanic and Caucasian populations.

Arch Dimension- Difference among malocclusion type
Braun, in 1998, found that there were differences in the dimensions of the
dental arch in different malocclusion types. They found Class II mandibular arches
were reduced in arch width and depth and Class III was greater in the arch width
dimension and reduced in arch depth in comparison to Class I arches. Consistent
with the findings of Kook in 2004 and Nojima in 2001, we found that the Class II
group had a larger canine depth and molar depth in comparison to the Class I sample.
The Class II also had the smallest canine width to depth ratio followed by the Class I
and then the Class III sample.
Canine depth was the least for the Class III sample, but had the widest
intermolar dimension.
Arch width was very similar regardless of malocclusion type, with the
exception of the Class III Caucasian sample that had an increased intermolar width.
Intercanine width was very the most consistent measurement between the three
malocclusion types.

Arch Form- Difference among malocclusion type
When comparing the Class II sample to the Class I sample there was a
decrease in the number of ovoid arch forms and an increase of square arch form in

46
the Hispanic sample and tapered arch form in the Caucasian sample. This is
inconsistent with the findings of Felton in 1987, where they found little differences
in arch form between Class I and Class II malocclusion groups.
There was a general increase in the square arch form in the Class III group,
when compared to both the Class I and II group; this is consistent with the findings
of Kook in 2004 and Nojima in 2001. Nojima postulated that this was due to the fact
that there is a “common pathogenesis of Class III malocclusion and the resultant
dental compensation by lingual tipping of the mandibular anterior teeth, causing the
anterior part of the mandibular arch to flatten” (Nojima, 2001).

Clinical Implications
Since there are differences in both arch dimension and frequency of arch
form between the Hispanic and Caucasian sample and among malocclusion type it is
essential to select a best fit arch form for non-adaptable wires and to individualize
the arch form in wires that can be altered, in order to minimize round tripping
(Braun, 1999) of the dentition and to enhance stability (Little, 1990) of the
orthodontic result.

47
Chapter 7: ASSUMPTIONS
There were several assumptions made for this study. The orthodontic patient
pool at USC Department of Graduate Orthodontics was representative of the general
population. Last names and photographs were used to assign a patient to a specific
ethnic group. Pre-treatment models were free of distortion and provided and
accurate assessment of patient’s true arch form and dimensions. Measurements were
accurate and reproducible.

48
Chapter 8: LIMITATIONS
There were several potential limitations to this study. There were a limited
number of records that satisfied the strict criteria set for the study. The study only
used orthodontic patients as opposed to the general population. Measurements were
subject to human error. Finally, the criteria for assignment into the separate ethnic
groups are difficult to define personal history, surname and appearance are good
indicators, but are not definitive.

49
Chapter 9: SUMMARY
The patients used in this study were from a large metropolitan area in the
western United States. The sampling model used would be able to generalize our
results to the rest of the population. One limiting factor was that the sample was
specifically pre-orthodontic patients. This possible threat to the external validity was
reduced by large sample sizes and randomized selection of patients included in the
study.
The results of this study could affect many aspects of orthodontic practice.
The fact that there was a significant difference arch form and dimension between
Hispanics and Caucasians as well as malocclusion types has great implications on
orthodontic treatment planning. No single arch form was unique to any one Angle
classification or ethnic group and the frequency of the arch forms varied greatly
between the groups. This study indicates that arch form should be individualized
based on pre treatment arch form, malocclusion type and ethnicity.

50
Chapter 10: CONCLUSIONS
1. Comparisons between Hispanics and Caucasians indicate that all arch
dimensions are larger in the Hispanic sample with the exception of canine
depth.
2. There is great variability in the frequency of arch forms between Hispanics
and Caucasians, with a majority of Hispanics having a square arch form and
Caucasians having a tapered or ovoid arch form
3. There is great variability in the frequency of arch forms between the different
Angle classifications
4. There is a difference in arch dimensions between the different Angle
classifications

51
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Abstract (if available)

Abstract Introduction: The purpose of this study was to clarify morphologic differences between Caucasian and Hispanic mandibular clinical arch forms in Class I, II, and III malocclusions. Methods: The study included 60 Class I, 50 Class II, and 50 Class III patients from each ethnic group. Orthodontic study models were photocopied, scanned, digitized, and measured (4 linear and 2 proportional). The dental arches were classified into square, ovoid, and tapered forms to compare the frequency distributions between the 2 ethnic groups. Results: The Caucasians had a significantly smaller arch dimensions than the Hispanics, except for canine depth. Caucasians had a higher frequency of tapered arch form whereas Hispanics had a high frequency of square arch form. Conclusion: There is a significant difference between frequency of arch forms and arch dimensions of Hispanic and Caucasian patients. Specifically, there is no arch form unique to any of Angle classification or ethnic group.

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Asset Metadata

Creator Gimlen, Amy Aland (author)

Core Title Comparative study of Caucasian and Hispanic mandibular clinical arch forms

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Defense Date 01/22/2007

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

Tag archform,OAI-PMH Harvest

Language English

Advisor Sameshima, Glenn T. (committee chair), [illegible] (committee member), Enciso, Reyes (committee member)

Creator Email gimlen@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m287

Unique identifier UC1123964

Identifier etd-Gimlen-20070222 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-157892 (legacy record id),usctheses-m287 (legacy record id)

Legacy Identifier etd-Gimlen-20070222.pdf

Dmrecord 157892

Document Type Thesis

Rights Gimlen, Amy Aland

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