Download BOLTON ANALYSIS COMPARISON AMONG DIFFERENT OCCLUSIONS IN A BLACK POPULATION

BOLTON ANALYSIS COMPARISON AMONG DIFFERENT
OCCLUSIONS IN A BLACK
POPULATION
Robert E. Patterson, D.D.S.
An Abstract Presented to the Faculty of the Graduate School
of Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2010
Abstract
Objectives:
To identify the prevalence of tooth-size
discrepancies in different malocclusions (Angle Class I,
II, and III) in a Black population, and whether a
discrepancy exists among the different malocclusion groups.
Materials and methods:
165 sets of dental casts (Class I =
55, Class II = 55, Class III = 55) with complete permanent
dentition were measured at the greatest mesiodistal width
from right first permanent molar to left first permanent
molar in the upper and lower jaws, then Bolton anterior and
total ratios were determined and compared.
Results:
The
prevalence of tooth size discrepancies (±2 SD of Bolton’s
published mean) in anterior and total ratios was 17.6% and
12.1%, respectively.
There was no significant difference
found among malocclusion groups in either the anterior
ratio (P>.05) or the total ratio (P>.05).
Conclusion:
The
anterior and total tooth size ratios are not significantly
different among Angle classification groups (Class I, II,
and III) in a Black population from the United States.
1
BOLTON ANALYSIS COMPARISON AMONG DIFFERENT
OCCLUSIONS IN A BLACK
POPULATION
Robert E. Patterson, D.D.S.
A Thesis Presented to the Faculty of the Graduate School of
Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2010
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Eustaquio A. Araujo,
Chairperson and Advisor
Professor Rolf G. Behrents,
Associate Clinical Professor Donald R. Oliver
i
DEDICATION
This thesis is dedicated to Dr. Gus, who always reminds us
that there is a “Bolton.”
ii
ACKNOWLEDGEMENTS
I would like to acknowledge Dr. Eustaquio Araujo, for
his constant support and encouragement, and his idea to
search out Bolton discrepancies in the first place.
I would like to acknowledge Dr. Rolf Behrents, and his
faith that I could come through in spite of the odds and
complete my thesis project.
I would also like to acknowledge Dr. Donald Oliver,
for his subtle and gentle ways to encourage me to be more
professional and make sure to dot my “i’s” and cross my
“t’s.”
Finally, I would like to acknowledge my wife and
sweetheart, Angie, for her overwhelming support,
encouragement, and sacrifice to allow me to complete this
project.
iii
TABLE OF CONTENTS
LIST OF TABLES............................................ v
LIST OF FIGURES......................................... vii
CHAPTER 1: INTRODUCTION................................... 1
CHAPTER 2: REVIEW OF THE LITERATURE
History of Occlusion .................................... 3
Angle’s Classification of Malocclusion ................ 3
Other Classifications of Malocclusion ................. 5
Skeletal Assessment of Malocclusion ................... 7
Factors of Occlusion .................................... 8
Factors of Tooth Size Variation ......................... 9
Genetic and Environmental Factors ..................... 9
Ethnic and Gender Factors ............................ 11
Intermaxillary Tooth-size Analyses ..................... 14
Anterior Coefficient ................................. 15
Anterior Index ....................................... 15
Bolton Ratio ......................................... 16
Ethnic and Gender Differences of the Bolton Ratio ...... 19
Tooth-size Discrepancy ................................. 21
Prevalence ........................................... 22
Correlation with Malocclusion ........................ 22
Summary and Statement of Thesis ........................ 26
References ............................................. 27
CHAPTER 3: JOURNAL ARTICLE
Abstract ...............................................
Introduction ...........................................
Materials and Methods ..................................
Results ................................................
Analysis of Error ....................................
Distribution of Anterior and Total Ratios ............
Prevalence of Tooth Size Discrepancy .................
Dental Ratios and Malocclusion Classification ........
Discussion .............................................
Conclusions ............................................
Acknowledgments ........................................
Literature Cited .......................................
33
33
35
39
39
41
43
44
54
58
59
59
APPENDIX................................................. 64
VITA AUCTORIS............................................ 65
iv
LIST OF TABLES
2.1 – Data determined using the Total Ratio..............17
2.2 - Data determined using the Anterior Ratio...........17
2.3 – Prevalence of anterior and total tooth-size
discrepancies as reported in the literature........22
2.4 – Reports of whether malocclusion differences are
associated with tooth size discrepancies...........26
3.1 – Non-parametric Wilcoxon testing of anterior ratio
measurements for all groups (Class I, II, and III)
for analysis of error showing no significant
difference (P>.05) between the initial (T1) and
second set of measurements (T2)....................40
3.2 – Non-parametric Wilcoxon testing of total ratio
measurements for all groups (Class I, II, and III)
for analysis of error showing no significant
difference (P>.05) between the initial (T1) and
second set of measurements (T2)....................41
3.3 – Distribution of anterior ratios using Bolton’s
published mean of 77.2 ± 1.65%.....................41
3.4 – Distribution of posterior ratios using Bolton’s
published mean of 91.3 ± 1.91%.....................42
3.5 – Prevalence of combined anterior and total tooth
size discrepancies.................................44
3.6 – Anterior and total ratios as a function of Angle
classification.....................................45
3.7 - Anterior and total ratio means of anterior and
total ratios greater than ±2 SD from Bolton’s
published mean as a function of Angle
classification.....................................46
3.8 - Summary of anterior and total ratio means as
published in the literature compared with the
findings of this study.............................48
A.1 - Descriptives of entire sample......................64
v
A.2 - Results of ANOVA testing...........................64
vi
LIST OF FIGURES
2.1 – Determination of the anterior coefficient
as defined by Neff.................................15
2.2 – Indices used by Lundström..........................16
2.3 – Formulas
anterior
ratio of
molar to
used to determine the ratio of the
teeth, canine to canine (3-3), and the
both posterior and anterior teeth, first
first molar (6-6).........................17
2.4 – Mathematic formula to determine the millimetric
difference determined using Bolton’s analysis;
an example.........................................19
3.1 – Digital caliper for measuring tooth width..........37
3.2 - Example of mesio-distal width measurement of
anterior teeth.....................................37
3.3 – Example of mesio-distal width measurement
posterior teeth....................................38
3.4 - Formula to determine anterior and total ratios
as defined by Bolton...............................38
3.5 – Graphical representation of the distribution
of the anterior and total ratios as compared to
Bolton’s published anterior and total ratio
means..............................................43
3.6 – Mean anterior ratio as a function of Angle
classification, ±1 SD..............................45
3.7 – Mean total ratio as a function of Angle
classification, ±1 SD..............................46
3.8 – Mean anterior ratio of anterior ratios ±2 SD
from Bolton’s published mean as a function
of Angle classification............................47
3.9 – Mean total ratio of total ratios ±2 SD from
Bolton’s published mean as a function of
Angle classification...............................46
vii
CHAPTER 1: INTRODUCTION
Orthodontic treatment is accomplished in multiple
phases.
Each stage requires overcoming certain aspects of
malocclusion unique to every patient.
Every stage,
performed in sequence, should be fully accomplished for an
optimal result.
While each stage has unique challenges,
the finishing stage can be, and often is, the most
difficult.
Numerous factors add difficulty to the
finishing phase.
Of these, one is the tooth-size
relationship between the maxillary and mandibular
dentitions.
Inadequate relationships between the maxillary and
mandibular teeth can pose problems in achieving the ideal
occlusion as described in the literature.1-19
Ideal
intercuspation, overjet and overbite (both transverse and
sagittal aspects) rely on tooth form and size.
Past literature demonstrated and documented
differences in tooth width among ethnicities6,10,12-14,16,17,19-25
and gender.7,10,11,13,14,16,17,19,21-23,26-31
The “ideal” relationship
of maxillary tooth-width to mandibular tooth-width was
established using a sample of 55 cases, disregarding gender
and ethnic differences.3
In addition, several studies to
date have been completed examining tooth-size ratio
1
discrepancies of different ethnic populations compared with
Angle classifications of malocclusion.6,8,10,12-15,18-20,30,32-40
In the past, tooth-width in a Black population has
been examined and reported that, on average, it is greater
than that of a Caucasian population.
However, no studies
have demonstrated the proper tooth-size ratio in relation
to different malocclusions for this population.
The purpose of this study was to examine the potential
differences that may exist between tooth-size ratios and
Angle Class I, II, and III in a Black population.
The objectives of this study were to identify the
following:
•
Prevalence of tooth-size discrepancies in a Black
population as a function of Angle Class I, II, or
III.
•
Whether a significant discrepancy exists among the
different malocclusion groups.
2
CHAPTER 2: REVIEW OF THE LITERATURE
History of Occlusion
In 1880, Kingsley began to describe orthodontic
procedures in his book A Treatise on Oral Deformities as a
Branch of Mechanical Surgery.41
At that time, dentitions
were often lacking a full complement of teeth, and
therefore, occlusal relationships were not considered when
planning orthodontic treatment.
However, due to the need
of prosthetic denture fabrication, the concept of occlusion
later became important.
This concept logically filtered to
the natural dentition.
Angle’s Classification of Malocclusion
In 1899, Angle provided a classification of
malocclusion based on the position of the maxillary first
molars.
He indicated that the location of the upper first
molars was essential to achieving an ideal occlusion, and
determined that in a normal or ideal occlusion, the
mesiobuccal cusp of the maxillary first molar would occlude
in the buccal groove of the mandibular first molar.
If
this relationship existed and the full dentition was
arranged on a smoothly flowing dental arch form, then an
3
ideal occlusion of cusp tip to opposing sulcus would
result.42
This idea led Angle to describe three classifications
of malocclusion, each based on the relationship of the
maxillary first molar to the mandibular first molar:
•
Class I—the mesiobuccal cusp of the maxillary first
molar occludes with the buccal groove of the
opposing mandibular first molar, with the remaining
dentition exhibiting malpositioning, tipping, and/or
rotations
•
Class II—the buccal groove of the mandibular first
molar is located distal to the mesiobuccal cusp of
the maxillary first molar
o Division 1-narrowing of the upper arch, with
protruding incisors
o Division 2-less narrowing of the upper arch,
lingual inclination of the upper incisors, and
“more or less bunching of the same”
ƒ
Subdivision-the first molars are in this
relationship unilaterally
•
Class III—the buccal groove of the mandibular first
molar is located mesial to the mesiobuccal cusp of
the maxillary first molar.42
4
Other Classifications of Malocclusion
Angle’s classification scheme is not a comprehensive
scheme for describing malocclusion.
This led others to
introduce additions to Angle’s classifications and
systematically include key characteristics of
malocclusions.
Martin Dewey introduced several types to describe the
position of teeth in Class I and III malocclusions.
He
divided Class I malocclusions into Class I-mutilated (cases
with missing teeth), Class I-Types 1, 2, and 3, which
indicate general crowding, Class II canines (maxillary
canine mesial to the mandibular canine), or Class III
canines (mandibular canine in an advanced mesial position
from that of a Class I occlusion in relation to the
maxillary canine), respectively.
Class III dentitions also
incorporated Types 1, 2, and 3 to further describe key
characteristics of the malocclusion.43
Ackerman and Proffit, following the advent of
cephalometrics, added characteristics of malocclusion to
Angle’s classification system in 1969.
They proposed five
different characteristics of classification:
1. Evaluation of crowding and asymmetry within the
dental arches and of incisor protrusion, with or
without an effect on the profile
5
2. Relationship between the dentition and soft-tissue
profile
3. Consideration of transverse, vertical, and anteroposterior planes of space
4. Appropriate position of jaws in relationship to each
of the planes of space, as well as jaw proportions
and their relationship to the malocclusion
classification
5. Diagnosis is inherent in the classification44
This system indicated the necessity of evaluating both the
dental and skeletal relationships in diagnosis.
Andrews, in 1972, examined 120 casts of normal
occlusion to determine “six keys of normal occlusion.”
The
first key corresponded to Angle’s classification, taking
into account the position of the molars.
However, this was
modified slightly to fit a curve of Spee that produced
maximum intercuspation.
The ideal molar relationship,
according to Andrews’ observations, has two parts: 1) The
mesiobuccal cusp tip of the first maxillary molar is
located between the mesiobuccal and distobuccal cusps in
the buccal groove, and 2) the distal aspect of the
distobuccal cusp of the maxillary first molar occludes with
the mesiobuccal surface of the mandibular second molar.45
6
Other characteristics of normal occlusion defined by
Andrews included crown angulation (both mesiodistal and
buccolingual), no rotations, no spaces, and a flat to
slight curve of Spee in the occlusal plane.45
While this
added significantly to the complexity of the description of
a normal occlusion, it addressed specific characteristics
of occlusion that Angle failed to address.
In spite of all the important contributions to
diagnosing malocclusion, the original Angle classification
remains a simple, yet effective, way to quickly assess
potential difficulties of the patient’s occlusion.
Skeletal Assessment of Malocclusion
As Angle established the malocclusion classification,
others recognized the need to also identify skeletal jaw
relationship.44,46,47
Much of this came about through
cephalometrics.
Riedel introduced an angular measurement to relate the
maxilla to the mandible (A-N-B).46
Points A and B are
constructions on specified landmarks on the maxilla and
mandible, respectively, indicating the junction of basal
and alveolar bone in both jaws.
Nasion is a point
represented by “N” and indicates where the nasal bone meets
the frontal bone.
This angular measurement effectively
7
related the antero-posterior positioning of the maxilla and
mandible in relation to the position of nasion.
A problem with A-N-B may occur if nasion is either
more anterior or posterior. The angular measurement change
gives a false notion regarding the spatial anteriorposterior relationships of the jaws.47
A new measurement
was introduced by Jacobson from Witswaterstrand, South
Africa, using the same A point and B point, but relating it
to the functional occlusal plane by measuring the distance
between points on the line of occlusion formed from the
bisection of perpendicular lines extending from points A
and B.
Jacobson termed it the “Wits” appraisal.
This
minimized potential error that existed in Riedel’s
analysis.
However, the problem with the “Wits” appraisal
is that it is completely dependent on the orientation of
the occlusal plane.48
Factors of Occlusion
Multiple factors are involved in creating the ideal
occlusion.
These have been reported as incisor thickness,
incisor angulation, arch form, and tooth size. In order to
achieve an ideal occlusion, each of these factors must
balance with the others.2-4,6-8,11,17,21-25,27,31,45,49-51
8
Factors of Tooth Size Variation
Factors involved in tooth size variation have been
investigated in the literature.
Although varying names
such as tooth size, tooth width, tooth dimension, dental
dimension, dental crown size, arch dimension, mesiodistal
dimension, mesiodistal diameter, tooth diameter, and
mesiodistal crown dimension have been used, they all are
synonyms for the greatest mesiodistal measurement of a
given tooth.3,4,6-8,10,12-15,17-31,38,49,51-59
Etiologic factors
determining tooth size include environment and genetics,
specifically addressing ethnicity and gender.
Genetic and Environmental Factors
Horowitz, Osborne and DeGeorge studied the anterior
teeth of twins and determined that genetic variability
played a part in overall anterior tooth size.
They also
found that the canine teeth had a low hereditability
component of variability.
In addition, they found that
environmental variation was about twice as great in the
maxillary incisors than the mandibular incisors.57
In a
separate study, the authors confirmed that a strong
component of genetic variability existed for the mesiodistal tooth dimensions of the permanent anterior teeth.58
9
Potter et al performed a twin study to determine
genetic and environmental causes of correlation among tooth
size variables.
They also examined “whether genetic or
environmental influences are the results of a single or of
several different factors.”
The results of the study
determined that correlation of tooth dimension was
primarily genetic in origin.
Furthermore, they found two
genetic systems that affected dimensions in each arch
separately.54
Due to advances in technology and gene mapping,
examination of phenotypic variation and genotypeenvironment interactions became possible.
Dempsey and
Townsend studied genetic and environmental effects on human
tooth size.
In a study involving 600 mono- and di-zygotic
twins, they found that all variables tested showed
significance of added genetic variation.
Also, “the
effects of individual or unique environment ranged from 829%.”52
Baydaş and colleagues went one step further,
evaluating the effects of heredity on the Bolton tooth-size
discrepancy.
Sibling pairs, totaling 184 subjects with
permanent dentition, ranging 13-21 years of age, were
studied, with Bolton anterior and overall ratios being
calculated for all subjects.
They found that heritability
10
played a significant role in all comparisons except a malefemale comparison.
Further, siblings of the same gender
showed high heritability, but those of different gender did
not.53
Ethnic and Gender Factors
Several studies have been completed documenting the
differences among the average tooth sizes of different
ethnicities and genders.
Average tooth sizes have been reported in the
literature for ethnic groups located throughout the world.
Generally, results indicate that while tooth sizes are not
the same throughout different populations, they match those
of a certain global region or ancestry.11,21-25,31,49
Gender studies, on average, indicate that the relative
size of teeth is greater in males than females. While both
the male and female tooth sizes of one population may be
larger than those of another population, when compared to
the opposite gender within the same group, the female tooth
size is smaller.7,21,22,27
Also, the literature indicates that
not all teeth show a significant difference, and the
permanent dentition tends to exhibit sexual dimorphism
greater than the deciduous dentition.7
11
Potter and others gathered information from a Filipino
sample of 100 males and 152 females.
Tooth size of
maxillary and mandibular dentitions were recorded, and
distinctions of left and right were made.
The findings
indicated a small absolute tooth size, but Potter et al
indicated it was appropriate for the Southeastern Asian
origin.
Gender findings showed overlapping between male
and female groups.
Interestingly, the canine, which was
the strongest discriminator between genders, could only
account for 16.4% of total male-female differences in tooth
size.21
A study of tooth size in an Icelandic population by
Axelsson and Kirveskari indicated that small tooth size of
Europeans and Caucasians had become accepted.
However, due
to variations among European populations, Axelsson and
Kirveskari wanted to compare tooth sizes of populations
with differing ethnic origins.
Using a sample of 1010
Icelandic children (hereditary origins from Ireland,
Scotland, and British Isles), they compared the mean tooth
width to those of Ohio Caucasian, Native American, and
Black samples.
While results concluded a significant
difference between Icelandic and Ohio Caucasian populations
(also of Northwest European origin), no difference was
found between Icelanders and the Native American
12
populations in this study, showing a close resemblance
between the populations.
Gender differences were smaller
than expected, with male tooth size being larger than that
of their counterpart.
The lateral incisors in the maxilla,
and the central incisors in the mandible showed the
greatest variability, with the first molars being the most
stable.23
Hattab and researchers studied a Jordanian population
and measured dental casts of 198 individuals (86 males and
112 females).22
They found that maxillary lateral incisors
showed the greatest variability and the first molar the
least, supporting Axelsson and Kirveskari’s research.23
Supporting the research of Potter et al, the canines showed
the greatest sexual dimorphism compared to any other
tooth.21
Males, on average, had a significantly greater
tooth size than females, by a cumulative tooth width of
3.1mm in the maxilla and 3.6mm in the mandible.
Hattab and
colleagues also found that the differences of measurement
between the left and right sides were insignificant.
Mean
Jordanian tooth size compared closely with that of Iraqis,
but was significantly greater than that of Chinese,
Yemenite-Jews, and Caucasians.22
In 1975, Richardson and Malhotra identified
mesiodistal crown dimensions of a Black population from
13
Nashville, Tennessee.
They did not compare the sizes to
known data, however.24
In a follow-up study, Keene examined
mesiodistal crown dimensions of a Black population from
Great Lakes, Illinois.
He found that, on average, the
population from Illinois had smaller teeth than those of
Richardson and Malhotra’s study—however, correlation
between the two groups was very high, and the dimensions
remained larger than those of a Caucasian population.25
Literature by Merz et al examined a population of
Blacks and Caucasians from San Diego, California and
Richmond, Virginia.
They concluded that mandibular canines
through first molars were significantly larger in the Black
sample and that no significant difference existed in the
mesiodistal diameter of the incisors.49
Intermaxillary Tooth-size Analyses
Tooth size is taken into account when occlusion is
examined.
In order for the ideal occlusion to occur, the
overall widths of the teeth in the maxillary arch must
complement the same teeth in the mandibular arch, within a
range.
This allows for ideal intercuspation, proper
overbite and overjet.2-4,42
14
Anterior Coefficient
Due to the complexity in relating proper tooth size
and ideal occlusion, Neff defined the “anterior
coefficient” in an effort to simplify the determination of
intermaxillary tooth-size relations.
His coefficient was
determined by dividing the sum of the mandibular anterior
teeth into the corresponding maxillary teeth.
The
mathematic formula is displayed below (Fig. 2.1):
Sum maxillary (3-3)
= “anterior coefficient”
Sum mandibular (3-3)
Fig. 2.1 – Determination of the anterior coefficient as defined by
Neff.2
The range of the coefficient reported in his paper was 1.10
to 1.55.
The 1.10 was determined with anterior teeth in an
“edge-to-edge” relationship (0% overbite), and the 1.55 was
a result of 100% overbite.
No mean was published.
A
“normal” overbite of 20% gave Neff an anterior coefficient
of 1.20-1.22 in an ideal occlusion.2
Anterior Index
Lundström evaluated 319 thirteen year-old children
using the following formulas (Fig. 2.2) to identify ratios
of mandibular and maxillary tooth size relationships.60
15
1. I1-I2-C (mandible)
I1-I2-C (maxilla)
2. P1-P2-M1 (maxilla)
P1-P2-M1 (mandible)
x 100
x 100
3. I1-I2-…M1 (mandible)
x 100
I1-I2-…M1 (maxilla)
Fig. 2.2 – Indices used by Lundström. I=incisors, C=canine,
P=premolars, M=molars. The subscripted number following indicates the
tooth order from the dental midline.60
He determined that the tooth widths had a significant
influence on the alignment of the arches, overbite, and
overjet.60
Bolton Ratio
Bolton recognized a need for a clinically applicable
way to determine disharmonies in occlusion due to tooth
size.
He therefore selected fifty-five cases, drawn from
ten private practices in the Seattle, Washington area, of
excellent occlusion.
Of these, 80% had been treated
orthodontically, while the remaining 20% had not.
None had
missing teeth.3
The dimensions of the teeth from first molar to first
molar in each arch were measured.
A ratio for the total
dentition and the anterior dentition was determined.
formulas below (Fig. 2.3) describe the method:
16
The
1. Sum 3-3 (mandibular)
x 100 = Anterior Ratio
Sum 3-3 (maxillary)
2. Sum 6-6 (mandibular)
x 100 = Total Ratio
Sum 6-6 (maxillary)
Fig. 2.3 – Formulas used to determine the ratio of the anterior teeth,
canine to canine (3-3), and the ratio of both posterior and anterior
teeth, first molar to first molar (6-6).3
Using these formulas, the following data (Tables 2.1 and
2.2) was gathered:3
Table 2.1 - Data determined using the Total Ratio
Range
Mean
Standard Deviation
Standard Error of the Mean
Coefficient of variation
87.5-94.8
91.3
1.91
.26
2.09%
Table 2.2 - Data determined using the Anterior Ratio
Range
Mean
Standard Deviation
Standard Error of the Mean
Coefficient of variation
74.5-80.4
77.2
1.65
.22
2.14%
Bolton converted these data to Neff’s anterior coefficient,
which corresponded to 1.29, which, according to Neff’s
calculations, would require 35% overbite—Bolton’s study
showed an average overbite of 31.3% for the sample.3,4
The determination of the means and ratios for both the
anterior and total dentition allows for a quick analysis
17
during the diagnostic phase of treatment.
Using this
method, the clinician could initially measure the tooth
widths, thereby immediately recognizing if a discrepancy
exists by comparing the anterior and total ratios to those
published by Bolton.
This information provides the
relative size difference between the arches.
For example,
if the anterior ratio was determined to be 79.9, by
comparing to the mean given, the clinician can immediately
know that either the maxillary dentition is too small, or
the opposing mandibular dentition is too large.4
Furthermore, by comparing the means, identification
of a discrepancy in the anterior or entire dentition would
become clear.
By knowing the means, the clinician can
determine the discrepancy (in millimeters) using simple
algebra.
First, the determination of which arch is too
large or too small must be made by comparing to Bolton’s
published mean.
Then, using the tooth width measurements
of the adequate arch, the ideal opposing arch dimensions
can be obtained (Fig 2.4).
Sum mandibular (3-3)(X)
x 100 = 77.2
Sum maxillary (3-3)(48)
Fig. 2.4 – Mathematic formula to determine the millimetric difference
determined using Bolton’s analysis; an example.4 X is the value to be
determined; 48 is the known value of the sum of tooth widths of the
adequate maxillary arch.
18
By comparing the two numbers, the millimetric
difference can be determined.
For example, in a case with
86.45 anterior tooth ratio, the mandibular anterior tooth
widths were determined to be too large at 41.5mm, and the
maxillary anterior tooth widths totaled 48mm.
By using the
known mean ratio of 77.2, the ideal of 37.05mm for the
mandibular arch could be calculated using the above
mentioned formula (Fig. 2.4).
Then subtracting the “ideal”
from the “actual” gives a difference of approximately
4.5mm, in this example.4
Ethnic and Gender Differences of the Bolton Ratio
The mean values established by Bolton were from a
sample of fifty-five cases from the Seattle, Washington
area.3
Ethnicity and gender of the patients was not
specified.
As described previously, differences in tooth
size exist among different ethnicities and genders.
Therefore, studies comparing Bolton’s published ratios with
those of different ethnic populations have also been
completed (Table 2.3-Appendix B).11,16,17,26,31,51,59
Smith and colleagues examined 30 males and 30 females
from three different populations—black, Hispanic, and
white.
They found that while the anterior ratio was
19
similar to Bolton’s ratio, the total ratio was very
different for all three groups.
The overall ratios were
92.3%, 93.1%, and 93.4% for whites, Hispanics, and blacks,
respectively.
In addition, the data in this study suggest
that the overall Bolton ratio only applies to white
females.11
The tooth size discrepancy of Dominican Americans
studied by Santoro et al was found to also be different
than the Bolton ratios.
They discovered that the overall
ratio coincided with Bolton’s, at 91.3.
However, the
anterior ratio was significantly larger, at 78.1,
determining that the average Dominican American patient
would either have a Class II canine with Class I molar
relationship, or a Class I canine with a slight Class III
molar relationship.51
Uysal and Sari examined a Turkish population and
determined that the relationships and sizes of the teeth
depend on population and gender.
Gender differences were
significantly different in the overall ratio.
They
therefore determined that the Turkish population studied
did not fall within the ratios specified by Bolton.17
Similarly, Paredes and others determined that Spanish
population values and Bolton’s were significantly different
and required specific standards for Spanish people.26
20
Endo
and researchers also found that Bolton’s anterior ratio was
not applicable to a Japanese population, and that Japanese
standards were required.31
Despite the ethnic differences reported in the
literature, other studies have shown similar results to
Bolton.
Al-Tamimi and Hashim established tooth-size ratios
in a Saudi population and found that Bolton’s prediction
tables can be used.16
Mirzakouchaki et al also found that
the Bolton standards can be used for an Iranian-Azari
population.59
Tooth-size Discrepancy
While the literature indicates that the data presented
by Bolton was possibly population and gender specific, his
study was unclear as to the prevalence of the discrepancy
within a given population, since he studied both treated
and untreated “ideal” occlusions.
Further, the
relationship between malocclusion and tooth-size
discrepancy was not described.
Multiple studies have attempted to provide data
regarding this lack of information.
Both the prevalence of
tooth size discrepancy and the correlation to malocclusion
has been examined among different ethnic populations and
gender.6,8,10,12-14,17-20,26,30,31,51,61
21
Prevalence
Many studies have been completed examining the
prevalence of anterior and total tooth-size discrepancies.
In each, it is determined as a percentage of cases that had
ratios greater than 2 of Bolton’s standard deviations from
the mean.
The following table (Table 2.3) provides a
summary of the literature.62
Table 2.3 - Prevalence of anterior and total tooth-size discrepancies
as reported in the literature.
Anterior
Total
Author
Discrepancy
Discrepancy
________________________________________________________
Othman and
Harradine61
17.4%
5.4%
Santoro et al51
28%
11%
17
Uysal and Sari
21.3%
18%
Paredes et al26
21%
5%
Endo et al31
21.6%
8.3%
Araujo and Souki14
22.7%
-Crosby and
Alexander8
22.9%
-Freeman et al9
30.6%
13.5%
36
Bernabé et al
20.5%
5.4%
*Discrepancies are indicated as greater than ±2 SD of Bolton’s
published mean.
Correlation with Malocclusion
The prevalence of tooth-size discrepancies indicates
some variation among populations, and the variation of
malocclusions among populations is known.
Many researchers
have attempted to define whether malocclusion is associated
with tooth size discrepancy; findings in the literature,
however, indicate conflicting information.
22
Lavelle studied a total of 120 patients—40
Caucasians from Birmingham, England, 40 African immigrants
of less than ten years, and 40 immigrants from Hong Kong of
less than ten years.
Malocclusion classification and
skeletal classification were matched according to Class I,
Class I Division 1 and 2, and Class III.
Lavelle found
moderate correlations relating to malocclusion and overall
tooth dimension.
In addition, he reported that the overall
tooth dimensions were greatest in the Class I malocclusion
and least in the Class III malocclusion.
His data suggest
that crown size may play a role in the etiology of
malocclusion.6
Crosby and Alexander identified the occurrence of
tooth size discrepancies among Class I, Class II Division 1
and 2, and Class II surgery malocclusion groups.
They
discovered that, in fact, there was no difference in the
prevalence of tooth size discrepancies from one
malocclusion to another.
There were, however, a large
number of tooth size discrepancies in each group.8
Supporting the previous study, Hashim and Al-Ghamdi
also found no difference among malocclusion groups.
They
did, however, find significant differences between the
normal and malocclusion samples.20
Uysal and others also
found no significant differences among malocclusion groups
23
(Class I, Class II Division 1 and 2, and Class III); they
also found significantly higher overall ratios in the
malocclusion groups when compared to the normal occlusion
group.15
Basaran and coworkers found no significant
differences for all the ratios between malocclusion groups
as well.30
Conversely, Ta et al identified significant
discrepancies between Bolton’s standards and certain
malocclusion groups in southern Chinese children.
They
studied 110 subjects (50 Class I, 30 Class II, and 30 Class
III) and found a significant difference in the Class III
group for the anterior ratio.
Additionally, they found
differences between the Bolton standard and Class II group,
and between the Class II and Class III groups for the
overall ratio.12
Nie and Lin also registered significant differences in
a sample of 120, made up of 3 groups of Class I, II, and
III.
They showed significant difference for all the ratios
between the groups, with Class III > Class I > Class II.10
Alkofide and Hashim, in a study of 240 pretreatment
orthodontic casts (60 each of Class I, II, and III and 60
normal occlusion casts), reported no significant
differences in the prevalence of tooth size discrepancies
for the overall ratio and anterior ratio between
24
malocclusion groups, except for the anterior ratio of Class
III malocclusion.13
In a study of 300 Brazilian patients, Araujo and Souki
found those with Class I and III malocclusions had
significantly greater prevalence of tooth size
discrepancies than those with Class II malocclusions.
Additionally, they determined that the mean anterior tooth
size discrepancy was greater in Class III patients than the
other malocclusion groups.14
Fattahi and others found that the overall ratio of
Class III patients was greater than other malocclusion
groups, and that the mean anterior ratio of the Class III
group was greater than that of the Class II group.
Endo
and colleagues did not find differences in the ratios among
malocclusion groups; however, when corrected to
millimeters, the mandibular correction showed differences
for the overall ratio between Class I and Class III
subjects.18
Oktay and Ulukaya found no difference in the anterior
ratio, but found significant differences in the total and
posterior ratios among malocclusion groups in a study of
500 Turkish subjects.
They summarized that tooth size
ratios “may vary in different malocclusion types and
may...contribute to the severity of a malocclusion.”40
25
The table below (Table 2.4) summarizes information
contained in the above-mentioned studies regarding toothsize discrepancy and malocclusion types.
Table 2.4 - Reports of whether malocclusion differences are associated
with tooth size discrepancies.
Author
Country
Malocclusion Diff.
__________________________________________________________
Lavelle6
USA
Yes
Crosby and Alexander8
USA
No
20
Saudi Arabia
No
Hashim and Al-Ghamdi
Nie and Lin10
China
Yes
Uysal et al15
Turkey
No
Basaran et al30
Turkey
No
Alkofide and Hashim13
Saudi Arabia
Yes
Araujo and Souki14
Brazil
Yes
Fattahi et al18
Iran
Yes
Endo et al19
Japan
Yes
12
Ta et al
Southern China Yes
Oktay and Ulukaya40
Turkey
Yes
Summary and Statement of Thesis
It is clear that various factors exist regarding tooth
size variation—specifically environment and genetics, which
includes gender and ethnicity.
Further, ethnicity exhibits
a wide range of anterior and overall ratios in comparison
with Bolton’s published data.
While conflicting data
exists regarding whether malocclusions are correlated with
tooth size discrepancies, knowing the data for a given
population could be useful in orthodontic diagnosis.
Knowledge of tooth size discrepancies during diagnosis
can allow the clinician to prepare for possible
difficulties that may arise during the finishing phase.
26
This includes coordinating treatment with a restorative
dentist to possibly increase the dimension of tooth width.
Therefore, the finest possible finish can be accomplished
with foreknowledge of these factors.
The purpose of this study is to examine a Black
population using dental casts of untreated patients to
determine anterior and posterior tooth size discrepancies
and compare the findings with the Angle classification
(Class I, II, or III) of each individual.
This would give
the clinician a better understanding of potential
difficulties that might arise in the finishing phase of
orthodontic treatment of a Black patient, whether they are
classified as Class I, II or III.
This will also help
determine the possible need for cosmetic bonding,
interproximal reduction, or both to accomplish an ideal
result.
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Bolton tooth size discrepancies among different
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S. Applicability of Bolton's tooth size ratios to a
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31
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contributions to variation in human tooth size. Heredity.
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Anthropol. 1976;44:391-395.
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dental dimension. II. Independent genetic determinants. Am
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Factors In Tooth Dimensions, A Study Of The Anterior Teeth
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alignment and occlusion. Acta Odontol Scand. 1955;12:265292.
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Bolton's ratios: a literature review. J Orthod. 2006;33:4551; discussion 29.
32
CHAPTER 3: JOURNAL ARTICLE
Abstract
Objectives:
To identify the prevalence of tooth-size
discrepancies in different malocclusions (Angle Class I,
II, and III) in a Black population, and whether a
discrepancy exists among the different malocclusion groups.
Materials and methods:
165 sets of dental casts (Class I =
55, Class II = 55, Class III = 55) with complete permanent
dentition were measured at the greatest mesiodistal width
from right first permanent molar to left first permanent
molar in the upper and lower jaws, then Bolton anterior and
total ratios were determined and compared.
Results:
The
prevalence of tooth size discrepancies (±2 SD of Bolton’s
published mean) in anterior and total ratios was 17.6% and
12.1%, respectively.
There was no significant difference
found among malocclusion groups in either the anterior
ratio (P>.05) or the total ratio (P>.05).
Conclusion:
The
anterior and total tooth size ratios are not significantly
different among Angle classification groups (Class I, II,
and III) in a Black population from the United States.
Introduction
Orthodontic treatment is accomplished in multiple
phases.
Each stage requires overcoming certain aspects
33
unique to every patient.
Every stage, performed in
sequence, should be fully accomplished for an optimal
result.
While each stage has unique challenges, the
finishing stage can be, and often is, the most difficult.
Numerous factors add difficulty to the finishing phase.
Of
these, one is the tooth-size relationship between the
maxillary and mandibular dentitions.
Inadequate relationships between the maxillary and
mandibular teeth can pose problems in achieving the ideal
occlusion as described in the literature.1-19
Ideal
intercuspation, overjet and overbite (both transverse and
sagittal aspects) rely on tooth form and size.
Past literature demonstrated and documented
differences in tooth width among ethnicities6,10,12-14,16,17,19-25
and gender.7,10,11,13,14,16,17,19,21-23,26-31
The “ideal” relationship
of maxillary tooth-width to mandibular tooth-width was
established by Bolton using a sample of 55 cases,
disregarding gender and ethnic differences.3
In addition,
several studies to date have been completed examining
tooth-size ratio discrepancies of different ethnic
populations correlated with Angle classifications of
malocclusion.6,8,10,12-15,18-20,30,32-40
In the past, tooth-width in a Black population has
been examined and reported that, on average, is greater
34
than that of a Caucasian population.
However, no studies
have demonstrated the proper tooth-size ratio in relation
to different malocclusions for this population.
The purpose of this study was to examine the potential
differences that may exist between tooth-size discrepancies
and Angle Class I, II, and III in a Black population.
The objectives of this study were to identify the
following:
•
Prevalence of tooth-size discrepancies in a Black
population as a function of Angle Class I, II, or
III.
•
Whether a significant discrepancy exists among the
different malocclusion groups.
Materials and Methods
The dental casts used in this study were obtained
using the archived and active records of patients at the
Center for Advanced Dental Education at Saint Louis
University in Saint Louis, Missouri.
Patients for this
study were living in Saint Louis or in the surrounding
areas, including both western-Illinois and Missouri.
A
total of 165 patients were randomly selected and assigned
to three separate groups according to the Angle
classification scheme.
Fifty-five patients were designated
35
to each group as Class I, II, or III.
Using cephalometric
measurements—ANB angle and the “Wits” appraisal—the
skeletal pattern was determined (see Table A.1).
The sample was selected based on the following
criteria:
•
Black descent
•
Dental classification and skeletal pattern matched (in
cases of ANB angle and “Wits” discrepancy, “Wits” was
used)
•
All permanent teeth were erupted in both the maxillary
and mandibular arches, from the central incisor
through the first permanent molar
•
Absence of any record of tooth modification (proximalsurface restorations, interproximal stripping, or
prosthetic alterations)
•
Dental casts lacked supernumerary, extracted, or
deformed teeth
•
Dental casts had to be of good quality, with no
fractured or altered teeth.
The greatest mesiodistal dimension of each incisor,
cuspid, premolar, and first permanent molars were measured
using a digital caliper with sharpened tips (Figs. 3.1-
36
3.3), accurate to 0.01mm.
Each measurement was recorded at
the 0.01mm, with the anterior 3-3 and total 6-6 sums
recorded at the 0.1mm level.
All measurements were made by
the same examiner, and reliability of measurements was
determined by randomly selecting and re-measuring 18 dental
casts one week after initial measurements, then subjecting
the data to nonparametric Wilcoxon statistical testing.
Fig. 3.1 – Digital caliper for measuring tooth width.
Fig. 3.2 – Example of mesio-distal width measurement of anterior teeth.
37
Fig. 3.3 – Example of mesio-distal width measurement posterior teeth.
Both the anterior and total tooth-size ratios for each
set of dental casts were determined using the formulas as
described by Bolton (Fig 3.4):
Sum 3-3 (mandibular)
Sum 3-3 (maxillary)
Sum 6-6 (mandibular)
x 100 = Anterior Ratio
x 100 = Total Ratio
Sum 6-6 (maxillary)
Fig. 3.4 – Formula to determine anterior and total ratios as defined by
Bolton.3
Analysis of variance (ANOVA) was used to compare the
mean Bolton anterior and total tooth-size ratios as a
function of Angle classification, for the total sample and
for those greater than ±2 SD of Bolton’s published mean.
Statistical testing was performed using SPSS 15.0.
38
Statistical differences were determined at the 95%
confidence level (P<.05).
Results
Analysis of Error
Reproducibility of the data was demonstrated through
re-measurement of 18 dental casts (Class I = 6, Class II =
6, Class III = 6), randomly selected from the original
dental casts.
All measurements were made by the same
examiner one week following the last measurements of all
dental casts.
There was no significant difference (P>.05)
found between the initial set of measurements (T1) and the
second set of measurements (T2) using the nonparametric
Wilcoxon test (Tables 3.1 and 3.2).
39
Table 3.1 – Non-parametric Wilcoxon testing of anterior ratio
measurements for all groups (Class I, II, and III) for analysis of
error showing no significant difference (P>.05) between the initial
(T1) and second set of measurements (T2).
Descriptive Measurements
MeasureGroup
Class I
Class II
Class III
ment
n
Min-
Max-
imum
imum
Mean
SD
T1
6
74.3
82.1
77.5
2.7
T2
6
74.7
82.0
77.1
2.6
T1
6
74.3
84.2
78.4
3.8
T2
6
74.6
81.9
78.7
2.6
T1
6
74.5
78.9
76.3
1.7
T2
6
74.3
84.2
76.8
1.9
40
P
.345 (T1=T2)
.753 (T1=T2)
.753 (T1=T2)
Table 3.2 – Non-parametric Wilcoxon testing of total ratio measurements
for all groups (Class I, II, and III) for analysis of error showing no
significant difference (P>.05) between the initial (T1) and second set
of measurements (T2).
Descriptive Measurements
MeasureGroup
Class I
ment
n
Min-
Max-
imum
imum
Mean
SD
T1
6
90.3
93.9
92.0
1.3
T2
6
90.6
93.3
91.9
1.0
T1
6
90.1
97.6
92.9
3.0
T2
6
89.4
96.5
92.7
2.6
Class III T1
6
88.0
93.0
91.1
1.7
T2
6
90.0
94.2
91.8
1.5
Class II
P
.463 (T1=T2)
.345 (T1=T2)
.116 (T1=T2)
Distribution of Anterior and Total Ratios
The distribution of anterior ratios and total ratios
is shown in Tables 3.3 and 3.4, respectively.
A graphical
representation of the distributions is shown in Fig. 3.5.
Table 3.3 – Distribution of anterior ratios using Bolton’s published
mean of 77.2 ± 1.65%.3
< -2 SD
< -2 SD < -1 SD
±1 SD
< 1 SD < 2 SD
> 2 SD
Total
n
8
19
80
37
21
165
% of sample
4.8
11.5
48.5
22.4
12.8
100
41
Twenty-nine subjects had anterior ratios greater than
±2 SD from Bolton’s mean.
Of these, 8 subjects were less
than -2 SD and 21 subjects were greater than +2 SD.
Fifty-
eight subjects had anterior ratios greater than ±1 SD but
less than ±2 SD, with 19 subjects less than -1 SD and 37
greater than 1 SD.
The remainder (80) fell within ±1 SD
from the mean published by Bolton.3
Table 3.4 - Distribution of posterior ratios using Bolton’s published
mean of 91.3 ± 1.91%.3
< -2 SD
< -2 SD < -1 SD
±1 SD
< 1 SD < 2 SD
> 2 SD
Total
n
0
3
98
44
20
165
%
0
1.8
59.4
26.7
12.1
100
Conversely, only 20 subjects exhibited a total ratio
greater than +2 SD, while there were no total ratios less
than -2 SD.
Forty-seven subjects had a total ratio greater
than ±1 SD but less than ±2 SD, with only 3 subjects less
than -1 SD and 44 greater than +1 SD.
The remaining
subjects (98) were within ±1 SD of Bolton’s published mean.3
42
98
100
Number of subjects (n)
90
80
80
70
60
50
30
21 20
19
20
0
Total Ratio
37
40
10
Anterior Ratio
44
8
3
0
>
<
±1
<
<
2
1
SD
<
SD
SD
SD
SD
-2
-2
2
<
SD
-1
SD
Distribution
Fig. 3.5 – Graphical representation of the distribution of the anterior
and total ratios as compared to Bolton’s published anterior and total
ratio means.3
Prevalence of Tooth Size Discrepancy
The prevalence of tooth size discrepancies was
determined using the published ratios as described by
Bolton: 77.2 ± 1.65% and 91.3 ± 1.91% for the anterior and
total ratios, respectively.3,4
Ratios within ±1 SD were
considered “normal,” and those that were greater than ±1 SD
were labeled as having a tooth size discrepancy (Table
3.5).
43
Table 3.5 - Prevalence of combined anterior and total tooth size
discrepancies.
< -2 SD
< -2 SD < -1 SD
< 1 SD < 2 SD
> 2 SD
Total
n
0
3
20
13
36
%
0
1.8
12.1
7.9
21.8
Not all subjects who had an anterior ratio exhibited a
total ratio, and vice versa.
A total of 36 out of 165
subjects had both anterior and total tooth size
discrepancies within the same category (Table 3.5).
Three
subjects had anterior and total tooth size discrepancies
that were less than -1 SD but greater than -2 SD.
Twenty
subjects had combined tooth size discrepancies greater than
+1 SD but less than +2 SD, and the remaining 13 had
combined tooth size discrepancies greater than +2 SD from
Bolton’s mean.3
The other 129 subjects had either no tooth size
discrepancy (62), no anterior tooth size discrepancy but a
total tooth size discrepancy (18), no total tooth size
discrepancy but an anterior tooth size discrepancy (36), or
a combination of tooth size discrepancy >±1 SD and >±2 SD
(13) between the anterior and posterior.
Dental Ratios and Malocclusion Classification
The anterior and total tooth size ratios were
compared as a function of Angle classification using
44
Analysis of Variance (ANOVA)(Table A.1).
No significant
differences were found among the malocclusion groups for
either ratio(P>.05)(Table A.2).
A summary of mean values
and standard deviations is presented below (Table 3.6,
Figs. 3.6 and 3.7):
Table 3.6 – Anterior and total ratios as a function of Angle
classification.
Anterior
Total Ratio
Class
n
Ratio Mean
SD
Mean
SD
I
55
78.1
2.67
92.7
1.65
II
55
77.9
2.51
92.7
2.13
III
55
77.9
2.55
92.7
2.18
Anterior Ratio (%)
82.0
80.0
78.0
76.0
74.0
78.1
77.9
77.9
I
II
III
72.0
Angle Classification
Fig. 3.6 – Mean anterior ratio as a function of Angle classification,
±1 SD. The dotted line represents Bolton’s anterior ratio mean of 77.2
± 1.65%.
45
Total Ratio (%)
96.0
94.0
92.0
90.0
88.0
92.7
92.7
92.7
I
II
III
86.0
Angle Classification
Fig. 3.7 - Mean total ratio as a function of Angle classification, ±1
SD. The dotted line represents Bolton’s total ratio mean of 91.3 ±
1.91%.
Descriptives of both anterior and total tooth size
discrepancies greater than ±2 SD are presented in Table 3.7
and Figs. 3.8. and 3.9. The sample size was too small to
compare as a function of Angle classification.
Table 3.7 – Anterior and total ratio means of anterior and total ratios
greater than ±2 SD from Bolton’s published mean as a function of Angle
classification.
Class
n
Anterior Ratio Mean
n
Total Ratio Mean
I
10
80.7
5
96.0
II
11
79.7
7
96.4
III
8
79.5
8
96.4
46
Anterior Ratio (%)
81
80.5
80
79.5
80.7
79.7
79.5
I
II
III
79
Angle Classification
Fig 3.8 – Mean anterior ratio of anterior ratios ±2 SD from Bolton’s
published mean as a function of Angle classification.
Total Ratio (%)
97
96.5
96
95.5
96.0
96.4
96.4
I
II
III
95
Angle Classification
Fig. 3.9 - Mean total ratio of total ratios ±2 SD from Bolton’s
published mean as a function of Angle classification.
The mean ratio findings of this study were compared to
others as published in the literature.
3.8) is presented below:
47
The summary (Table
Table 3.8 – Summary of anterior and total ratio means as published in the literature compared with the
findings of this study.
Author(s)
Occlusion
Type
Subject
Demographic
n
Lundström41
*
319
Neff2
Bolton4
Stifter32
*
*
Ideal*
Normal*
Class I
Swedish
schoolchildren
*
*
Lavelle6
48
Richardson &
Malhotra24
Crosby &
Alexander8
Ho & Freer42
Freeman et
al9
*
Class I
Class II
Div 1
Class II
Div 2
Class II
Surgery
*
Total
Ratio Mean
%
97.2 ± 2.1
***
91.3 ±
90.0 ±
91.1 ±
91.7 ±
90.8 ±
93.5 ±
92.9 ±
92.6 ±
92.1 ±
94****
Year
Published
1954
Male
Female
Black
Male
Female
East Asian Male
Female
Black
20
20
20
20
20
20
162
79.0**
77.2 ±
77.6 ±
78.6 ±
76.8 ±
77.5 ±
79.4 ±
78.6 ±
78.7 ±
78.2 ±
77
Orthodontic
patients from
Richardson and
Dallas, TX
30
30
77.2 ± 2.7
78.2 ± 3.1
91.3 ± 2.4
91.7 ± 2.3
29
76.8 ± 5.3
91.5 ± 3.1
20
77.5 ± 2.7
91.3 ± 2.2
60
78.7 ± 2.1
92.0 ± 1.6
1994
157
77.8 ± 3.1
91.4 ± 2.6
1996
Caucasian
Australian
subjects
Caucasian, Black,
and other
200
55
24
Anterior
Ratio Mean
%
78.5 ± 2.1
48
1.7
2.7
2.4
1.5
1.6
2.1
1.9
1.7
1.4
1.9
2.1
1.8
2.0
1.9
2.4
1.8
2.5
1.6
1957
1958
1958
1972
1975
1989
Table 3.8 - Continued
Nie & Lin10
Smith et al11
49
Santoro et
al43
Ta et al12
Normal
Mainland Chinese
Bimax
subjects
protrusive
Class II
Div 1
Class II
Div 2
Class III
Class III
Surgery
*
White
Black
Hispanic
Male
Female
*
Dominican
Americans
Southern Chinese
Class I
Male
Female
Class II
Male
Female
Class III
Male
Female
60
60
81.5 ± 2.8
81.5 ± 2.7
93.3 ± 2.5
93.5 ± 2.5
60
80.6 ± 3.2
92.2 ± 2.5
60
81.0 ± 3.1
92.0 ± 2.5
60
60
82.8 ± 3.2
82.6 ± 2.6
95.6 ± 2.7
95.6 ± 2.5
60
60
60
90
90
54
79.6
79.3
80.5
80.1
79.5
78.1 ± 2.9
92.3
93.4
93.1
93.3
92.6
91.3 ± 2.2
25
25
15
15
15
15
77.6
77.5
77.8
77.7
77.9
79.2
91.1
90.2
90.4
90.4
91.2
91.7
1999
2000
2001
2001
49
±
±
±
±
±
±
1.8
1.8
1.7
1.4
3.1
1.8
±
±
±
±
±
±
1.0
1.2
1.8
0.7
2.1
1.4
Table 3.8 - Continued
Alkofide &
Hashim13
Class I
Class II
Class III
Laino et al35
Araujo &
Souki14
50
Skeletal
Class I
Class II
Class III
Class I
Class II
Class III
Bernabé et
al36
*
Al-Tamini &
Hashim16
*
Saudi Arabian
Male
Female
Male
Female
Male
Female
Italian
Brazilian, Belo
Horizonte
Male
Female
Peruvian
Male
Female
Saudi Arabian
40
40
40
40
40
40
93
78.8
78.8
78.6
78.8
79.7
77.3
78.1
±
±
±
±
±
±
±
2.3
3.2
2.7
2.2
2.5
2.0
2.4
92.1
92.4
92.5
93.1
93.2
92.2
91.4
100
100
100
145
155
78.2
78.2
79.0
78.4
78.5
±
±
±
±
±
2.8
2.2
2.4
2.5
2.5
***
2003
91.3 ± 2.1
90.8 ± 1.7
2005
91.4 ± 1.5
2005
100
100
65
50
78.4 ± 2.8
77.8 ± 2.4
77.4 ± 1.8
±
±
±
±
±
±
±
1.6
2.3
2.2
2.2
2.2
2.0
2.0
2002
2003
Table 3.8 – Continued
Uysal et al15
Normal
Turkish
Class I
Class II
div 1
Class II
div 2
Class III
51
Nourallah et
al37
Paredes et
al26
*
Syrian
*
Spanish
Total
Male
Female
72
78
6
150
75
78.2
78.3
78.7
78.4
78.7
±
±
±
±
±
82
11
78.4 ± 3.6
79.6 ± 3.4
91.1 ± 4.0
90.8 ± 2.3
23
58
55
55
78.7
78.0
78.0
79.0
89.8
92.3
91.0
92.3
±
±
±
±
2.8
2.4
3.1
3.2
3.1
4.6
3.7
3.1
2.2
89.8
91.7
91.6
91.6
91.2
±
±
±
±
±
±
±
±
±
2.3
2.3
3.5
3.0
2.5
4.6
3.7
3.6
2.1
2005
2005
2006
100
70
30
51
78.3 ± 2.4
78.3 ± 2.2
78.3 ± 2.6
92.0 ± 2.0
92.1 ± 1.7
91.9 ± 2.0
Table 3.8 – Continued
Fattahi et
al18
Class I
Class II
Div 1
Class II
Div 2
Class III
Overall
52
Akyaçin et
al38
Class I
Class II
Class III
Total
Class
Class
Class
Mirzakouchaki Class
et al44
Endo et al19
*
I
II
III
I
Iranian
Total
Male
Female
Male
Female
Male
Female
Male
Female
Male
Female
Turkish
Male
Female
Male
Female
Male
Female
Iranian-Azari
subjects
Japanese
Total
Male
Female
200
25
25
25
25
25
25
25
25
100
100
79.0
80.1
78.8
78.5
76.9
79.0
78.4
80.6
79.7
79.6
78.4
±
±
±
±
±
±
±
±
±
±
±
2.8
2.3
3.8
2.4
1.6
2.4
2.4
3.3
2.4
2.7
2.8
91.7
92.2
91.5
90.5
90.6
91.0
91.2
93.6
92.7
91.9
91.5
±
±
±
±
±
±
±
±
±
±
±
2.2
1.8
2.6
1.7
1.8
2.0
2.1
2.0
1.7
2.2
2.2
22
26
28
32
24
20
78.4
77.9
78.2
78.6
79.0
76.8
±
±
±
±
±
±
3.4
3.6
4.4
4.0
3.0
3.9
91.6
91.1
90.6
90.8
91.8
89.6
±
±
±
±
±
±
2.5
2.3
2.9
3.0
2.0
2.8
48
60
44
50
78.2
78.4
78.0
78.0
±
±
±
±
3.4
4.1
3.7
3.1
91.3
90.8
90.8
92.0
±
±
±
±
2.3
2.9
2.6
2.4
60
30
30
78.4 ± 2.2
78.2 ± 2.2
78.6 ± 2.2
52
91.6 ± 2.1
91.9
91.8
2006
2006
2007
2007
Table 3.8 – Continued
Othman and
Harradine45
Mixed
Freire et
al39
Endo et al31
Normal*
Class I
Class II
Class III
53
Patterson
Class I
Class II
Class III
Ethnicity unknown
Total
Male
Female
Brazilian
Japanese
Male
Female
Male
Female
Male
Female
Black – US
150
96
54
30
78.5 ± 2.3
78.6
78.6
77.8 ± 2.2
30
30
30
30
30
30
77.6
77.3
77.9
77.9
77.5
78.2
±
±
±
±
±
±
1.8
2.5
2.3
2.3
1.9
2.4
55
55
55
78.2 ± 2.7
77.9 ± 2.5
77.9 ± 2.6
*Data not specified/defined.
**Converted value from anterior coefficient.
***Not included in this study.
****Includes second molars.
Classification and gender are included if they were specified in the study.
53
91.8 ± 1.8
91.9
91.8
91.5 ± 1.6
91.4
90.9
91.4
91.2
91.5
91.8
±
±
±
±
±
±
2.1
2.2
2.0
1.9
1.5
2.2
92.7 ± 1.7
92.8 ± 2.1
92.7 ± 2.2
2007
2007
2008
Discussion
Tooth size discrepancies (TSD) play an important role
in orthodontic finishing.
The necessity of appropriate
tooth size ratios has been well established in the
literature1-19 and accepted among orthodontists.
A lack of
proper relationships between the upper and lower teeth
during orthodontic finishing may result in an occlusal
relationship that either does not have good coupling in the
anterior or suitable cusp-to-fossa/embrasure alignment in
the posterior. Other factors, including incisor angulation
and tooth thickness have also been considered as meaningful
in achieving an ideal occlusion.46
The high prevalence of TSDs in the anterior and
posterior regions in this sample indicates the importance
of recognizing TSDs as part of orthodontic diagnosis.
Being aware of tooth size discrepancies prior to initiation
of treatment provides an advantage to making decisions for
the finishing phase.
This study showed that in a Black
population, 85 (51.5%) of 165 subjects exhibited an
anterior TSD greater than ±1 SD as defined by Bolton, 67
(40.6%) of 165 subjects had a total TSD greater than ±1 SD,
and only 36 (21.8%) displayed a discrepancy greater ±1 SD
in both the anterior and total ratios.
54
The prevalence of anterior TSD (greater than ±1 SD) of
51.5% corresponds to the high prevalence reported by Araujo
and Souki14 (56%, n=300), but contrasts that reported by
Bolton (29%, n=100) and Richardson4 (33.7%, n=205).
This
difference could possibly be explained by variations due to
demographics and ethnicity.
Because clinicians would be reluctant to reduce or add
tooth size with a discrepancy of ±1 SD (approx. 1.5mm
clinically, or 0.75mm each side), several
authors8,9,14,17,26,36,45,43 have used ±2 SD as the benchmark for
establishing a clinically significant discrepancy, which is
equivalent to approximately 3mm or more, an amount more
likely to be corrected by removal of tooth structure and/or
prosthetic alteration.
The anterior TSD prevalence of
17.6% agrees with that reported by Othman and Harradine,45
and is close to that of Uysal and Sari,17 Paredes et al,26
Endo et al,31 Araujo and Souki,14 Crosby and Alexander,8 and
Bernabé et al.36
The total TSD prevalence of 12.1% falls
among those published by several others.9,17,26,31,36,45,43
However, Othman and Harradine46 suggest that the ±2 SD
range generally underestimates the prevalence of a
discrepancy and therefore recommend disregarding the Bolton
standard deviation as a measure of the prevalence of
clinically significant discrepancy.
55
Further, a delineation
using standard deviation between what is clinically
relevant and what is not does not accurately determine what
is needed clinically.
For example, a TSD of 1.5mm spread
throughout the entire maxillary dentition represents a
clinically insignificant amount, whereas a discrepancy of
1.5mm on a lateral incisor would be considered a
significant clinical discrepancy.
Interestingly, the presence of a discrepancy in the
anterior tooth size ratio did not necessarily correspond
with a discrepancy in the total tooth size ratio and vice
versa, as would be expected.
A similar finding was
reported by Uysal et al,15 using a Turkish population,
suggesting large variation in tooth size among the anterior
teeth.
This indicates that variation in tooth size in the
anterior teeth can be independent of variation in the tooth
size of posterior teeth.
Of 29 (17.6%) subjects found to
have an anterior tooth size discrepancy of greater than ±2
SD, only 13 (7.9%) also had a total TSD greater than ±2 SD.
In addition, 8 (4.8%) subjects had an anterior TSD greater
than ±2 SD, but a total TSD of greater than ±1 SD but less
than ±2 SD, while 5 (3.0%) had a total TSD greater than ±2
SD but an anterior TSD greater than ±1 SD but less than ±2
SD.
56
To fully establish prevalence of TSDs in a Black
population, an epidemiological study with a greater sample
size should be used.
Differences among ethnic groups
regarding tooth size and prevalence of TSDs in the
literature warrants future investigation.
Bolton published his anterior and total ratio means as
77.2 ± 1.65% and 91.3 ± 1.91%, respectively.3,4
The
anterior ratio mean was 78.0 ± 2.56% and the total ratio
mean was 92.7 ± 1.99% in this study.
This is slightly
higher on average than that reported by Bolton.
Several studies comparing TSDs to malocclusion have
been reported to date;6,8,10,12-15,18-20,30,32-40 however, this has
generally been conflicting data.
These studies have been
of several ethnic groups (Saudi Arabian, Chinese, Turkish,
Brazilian, Iranian, and Japanese).
In the present study,
no significant difference between malocclusion groups was
found.
This supports data published by Crosby and
Alexander,8 Hashim and Al-Ghamdi,20 Uysal et al,15 and
Basaran et al.30
However, Crosby and Alexander did not
include Class III malocclusions in their study.
Others have found significant differences between
malocclusion groups.
Lavelle6 surmised from his study that
maxillary tooth width was least among Class III
malocclusions, and suggested that this could be a
57
contributing factor to the malocclusion.
Nie and Lin10
similarly stated that mandibular teeth in Class III
malocclusion had overall larger dimensions than other
malocclusions.
Sperry et al33 also concluded that the Class
III group, when compared with the Class I and II groups,
had an overall excess in mandibular tooth size.
Alkofide
and Hashim13 found a difference in the anterior tooth size
discrepancy among Class III malocclusions; Araujo and
Souki14 found a significant difference in the prevalence of
anterior tooth size discrepancy for Class I and III
malocclusions when compared to Class II; and Fattahi et al18
found a significant difference in Class III malocclusions
for both the anterior and total tooth size ratios.
Conclusions
Based on the findings of this investigation, the
following conclusions can be made:
•
The means found in this study for anterior and total
ratios were higher than those published by Bolton.
•
There were no statistically significant differences among
Angle Class I, Class II, and Class III malocclusion
groups as a function of anterior and total tooth size
ratios.
58
•
There exist in this sample a large number of subjects who
exhibited tooth size ratios greater than ±1 SD of
Bolton’s published means.
Acknowledgments
The author wishes to acknowledge Dr. Eustaquio Araujo
for his guidance and support, Dr. Donald Oliver and Dr.
Rolf Behrents for proofreading and guidance, Dr. Steven
Harrison for assistance in gathering the sample, and Dr.
Heidi Israel for statistical guidance and analysis.
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63
APPENDIX
Table A.1 – Descriptives of entire sample
Descriptives
Anter
-ior
Ratio
Total
Ratio
64
I
II
III
Total
I
II
III
Total
N
55
55
55
165
55
55
55
165
Mean
78.1
77.9
77.9
78.0
92.7
92.7
92.7
92.7
SD
2.67
2.51
2.55
2.56
1.65
2.13
2.18
1.99
SE
.36
.34
.34
.19
.22
.29
.29
.15
95% Confidence
Interval for
Mean
Lower
Upper
Bound
Bound
78.9
77.4
78.6
77.2
78.6
77.2
78.4
77.6
93.2
92.3
93.3
92.2
93.3
92.1
93.0
92.4
Minimum
73.49
73.54
72.79
72.79
89.84
89.47
88.00
88.00
Maximum
86.86
84.22
84.88
86.86
96.69
97.57
97.23
97.57
Table A.2 - Results of ANOVA testing
ANOVA
Anterior
Ratio
Between Groups
Within Groups
Total
Sum of
Squares
2.325
1076.297
1078.622
Total
Ratio
Between Groups
Within Groups
Total
.044
648.396
648.440
df
2
162
164
2
162
164
Mean
Square
1.162
6.644
.022
4.002
F
.175
Sig.
.840
.006
.994
VITA AUCTORIS
Robert Edwin Patterson was born in Castro Valley, CA,
on September 29th, 1977 to Robert Frank Patterson and Ruth
Stearns Patterson.
He is the fourth of six children.
Robert grew up in, and attended elementary, middle, and
high schools in Castro Valley, CA.
Robert attended Brigham Young University from the fall
of 1995 and graduated in May of 2002.
From 1996 to 1998,
on a hiatus from university studies, he completed a
proselyting mission for The Church of Jesus Christ of
Latter-day Saints in Seoul, Korea.
Upon his return to the
United States, he began his bachelor’s degree study at
Brigham Young University of Korean.
In the summer of 2002, Robert began attending Virginia
Commonwealth University School of Dentistry.
In June 2006
he obtained his D.D.S. degree and began an Advanced
Education in General Dentistry program at the same school
to further his education, earning a certificate in June
2007.
Robert began his current residency in orthodontics at
Saint Louis University Center for Advanced Education.
expects to graduate and receive his master’s degree in
January 2010.
65
He
Robert enjoys athletic activities including running,
cycling, soccer, and volleyball.
time with his family.
He spends much of his
He and his spouse, Angela Davis
Patterson, have three children – Colden, Dylan, and
Evelynn.
66