Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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” 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. References 1. Ballard M. Asymmetry in Tooth Size: A Factor in the Etiology, Diagnosis and Treatment of Malocclusion. Angle Orthod. 1944;14:67-71. 2. Neff CW. Tailored occlusion with the anterior coefficient. Am J Orthod. 1949;35:309-313. 3. Bolton WA. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod. 1958;28:113-130. 27 4. Bolton WA. The clinical application of a tooth-size analysis. Am J Orthod. 1962;48:504-529. 5. Sanin C, Savara BS. An analysis of permanent mesiodistal crown size. Am J Orthod. 1971;59:488-500. 6. Lavelle CL. Maxillary and mandibular tooth size in different racial groups and in different occlusal categories. Am J Orthod. 1972;61:29-37. 7. Arya BS, Savara BS, Thomas D, Clarkson Q. Relation of sex and occlusion to mesiodistal tooth size. Am J Orthod. 1974;66:479-486. 8. Crosby DR, Alexander CG. The occurrence of tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop. 1989;95:457-461. 9. Freeman JE, Maskeroni AJ, Lorton L. Frequency of Bolton tooth-size discrepancies among orthodontic patients. Am J Orthod Dentofacial Orthop. 1996;110:24-27. 10. Nie Q, Lin J. Comparison of intermaxillary tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop. 1999;116:539-544. 11. Smith SS, Buschang PH, Watanabe E. Interarch tooth size relationships of 3 populations: "does Bolton's analysis apply?". Am J Orthod Dentofacial Orthop. 2000;117:169-174. 12. Ta TA, Ling JY, Hägg U. Tooth-size discrepancies among different occlusion groups of southern Chinese children. Am J Orthod Dentofacial Orthop. 2001;120:556-558. 13. Alkofide E, Hashim H. Intermaxillary tooth size discrepancies among different malocclusion classes: a comparative study. J Clin Pediatr Dent. 2002;26:383-387. 14. Araujo E, Souki M. Bolton anterior tooth size discrepancies among different malocclusion groups. Angle Orthod. 2003;73:307-313. 15. Uysal T, Sari Z, Basciftci FA, Memili B. Intermaxillary tooth size discrepancy and malocclusion: is there a relation? Angle Orthod. 2005;75:208-213. 28 16. Al-Tamimi T, Hashim HA. Bolton tooth-size ratio revisited. World J Orthod. 2005;6:289-295. 17. Uysal T, Sari Z. Intermaxillary tooth size discrepancy and mesiodistal crown dimensions for a Turkish population. Am J Orthod Dentofacial Orthop. 2005;128:226-230. 18. Fattahi HR, Pakshir HR, Hedayati Z. Comparison of tooth size discrepancies among different malocclusion groups. Eur J Orthod. 2006;28:491-495. 19. Endo T, Abe R, Kuroki H, Oka K, Shimooka S. Tooth size discrepancies among different malocclusions in a Japanese orthodontic population. Angle Orthod. 2008;78:994-999. 20. Hashim HA, Al-Ghamdi S. Tooth width and arch dimensions in normal and malocclusion samples: an odontometric study. J Contemp Dent Pract. 2005;6:36-51. 21. Potter RH, Alcazaren AB, Herbosa FM, Tomaneng J. Dimensional characteristics of the Filipino dentition. Am J Phys Anthropol. 1981;55:33-42. 22. Hattab FN, al-Khateeb S, Sultan I. Mesiodistal crown diameters of permanent teeth in Jordanians. Arch Oral Biol. 1996;41:641-645. 23. Axelsson G, Kirveskari P. Crown size of permanent teeth in Icelanders. Acta Odontol Scand. 1983;41:181-186. 24. Richardson ER, Malhotra SK. Mesiodistal crown dimension of the permanent dentition of American Negroes. Am J Orthod. 1975;68:157-164. 25. Keene HJ. Mesiodistal crown diameters of permanent teeth in male American Negroes. Am J Orthod. 1979;76:95-99. 26. Paredes V, Gandia JL, Cibrian R. Do Bolton's ratios apply to a Spanish population? Am J Orthod Dentofacial Orthop. 2006;129:428-430. 27. Haralabakis NB, Sifakakis I, Papagrigorakis M, Papadakis G. The correlation of sexual dimorphism in tooth size and arch form. World J Orthod. 2006;7:254-260. 28. Schwartz GT, Dean MC. Sexual dimorphism in modern human permanent teeth. Am J Phys Anthropol. 2005;128:312-317. 29 29. Guatelli-Steinberg D, Sciulli PW, Betsinger TK. Dental crown size and sex hormone concentrations: another look at the development of sexual dimorphism. Am J Phys Anthropol. 2008;137:324-333. 30. Basaran G, Selek M, Hamamci O, Akkuş Z. Intermaxillary Bolton tooth size discrepancies among different malocclusion groups. Angle Orthod. 2006;76:26-30. 31. Endo T, Shundo I, Abe R, Ishida K, Yoshino S, Shimooka S. Applicability of Bolton's tooth size ratios to a Japanese orthodontic population. Odontology. 2007;95:57-60. 32. Stifter J. A Study Of Pont's, Howes', Rees', Neff's And Bolton's Analyses On Class I Adult Dentitions*. Angle Orthod. 1958;95:457-461. 33. Sperry T, Worms F, Isaacson R, Speidel T. Tooth-size discrepancy in mandibular prognathism. Am J Orthod. 1977;72:183-190. 34. Heusdens M, Dermaut L, Verbeeck R. The effect of tooth size discrepancy on occlusion: An experimental study. Am J Orthod Dentofacial Orthop. 2000;117:184-191. 35. Laino A, Quaremba G, Paduano S, Stanzione S. Prevalence of tooth-size discrepancy among different malocclusion groups. Prog Orthod. 2003;4:37-44. 36. Bernabé E, Major PW, Flores-Mir C. Tooth-width ratio discrepancies in a sample of Peruvian adolescents. Am J Orthod Dentofacial Orthop. 2004;125:361-365. 37. Nourallah AW, Splieth CH, Schwahn C, Khurdaji M. Standardizing interarch tooth-size harmony in a Syrian population. Angle Orthod. 2005;75:996-999. 38. Akyalçin S, Doğan S, Dinçer B, Erdinc AME, Oncağ G. Bolton tooth size discrepancies in skeletal Class I individuals presenting with different dental angle classifications. Angle Orthod. 2006;76:637-643. 39. Freire SM, Nishio C, Mendes ADM, Quintão CCA, Almeida MA. Relationship between dental size and normal occlusion in Brazilian patients. Braz Dent J. 2007;18:253-257. 30 40. Oktay H, Ulukaya E. Intermaxillary tooth size discrepancies among different malocclusion groups. Eur J Orthod. 2009. Available at: http://www.ncbi.nlm.nih.gov/pubmed/19729399 [Accessed October 11, 2009]. 41. Kingsley N. A treatise on oral deformities as a branch of mechanical surgery. (London): Lewis; 1880:15867813. Available at: http://openlibrary.org/b/OL22895658M/treatise _on_oral_deformities_as_a_branch_of_mechanical_surgery. [Accessed October 7, 2009]. 42. Angle EH. Classification of Malocclusion. Dental Cosmos. 1899;41:248-264. 43. Dewey M. Practical Orthodontia. Saint Louis: The C. V. Mosby company; 1914:342. 44. Ackerman JL, Proffit WR. The characteristics of malocclusion: a modern approach to classification and diagnosis. Am J Orthod. 1969;56:443-454. 45. Andrews LF. The six keys to normal occlusion. Am J Orthod. 1972;62:296-309. 46. Riedel RA. The relation of maxillary structures to cranium in malocclusion and in normal occlusion. Angle Orthod. 1952;22:142-145. 47. Jacobson A. The "Wits" appraisal of jaw disharmony. Am J Orthod. 1975;67:125-138. 48. Proffit W, Fields H, Sarver D. Section III, Diagnosis and Treatment. In: Contemporary Orthodontics. 4th ed. Saint Louis, MO: Mosby; 2007:212. 49. Merz ML, Isaacson RJ, Germane N, Rubenstein LK. Tooth diameters and arch perimeters in a black and a white population. Am J Orthod Dentofacial Orthop. 1991;100:53-58. 50. Lee S, Lee S, Lim J, Ahn S, Kim T. Cluster analysis of tooth size in subjects with normal occlusion. Am J Orthod Dentofacial Orthop. 2007;132:796-800. 51. Santoro M, Ayoub ME, Pardi VA, Cangialosi TJ. Mesiodistal crown dimensions and tooth size discrepancy of 31 the permanent dentition of Dominican Americans. Angle Orthod. 2000;70:303-307. 52. Dempsey PJ, Townsend GC. Genetic and environmental contributions to variation in human tooth size. Heredity. 2001;86:685-693. 53. Baydaş B, Oktay H, Metin Dagsuyu I. The effect of heritability on Bolton tooth-size discrepancy. Eur J Orthod. 2005;27:98-102. 54. Potter RH, Nance WE, Yu PL. Genetic determinants of dental dimension: a twin study. Prog Clin Biol Res. 1978;24 Pt C:235-240. 55. Potter RH, Nance WE. A twin study of dental dimension. I. Discordance, asymmetry, and mirror imagery. Am J Phys Anthropol. 1976;44:391-395. 56. Potter RH, Nance WE, Yu PL, Davis WB. A twin study of dental dimension. II. Independent genetic determinants. Am J Phys Anthropol. 1976;44:397-412. 57. Horowitz SL, Osborne RH, DeGeorge FV. Hereditary Factors In Tooth Dimensions, A Study Of The Anterior Teeth Of Twins. Angle Orthod. 1958;28:87-93. 58. Osborne RH, Horowitz SL, DeGeorge FV. Genetic Variation in Tooth Dimensions: A Twin Study of the Permanent Anterior Teeth. Am J Hum Genet. 1959;30:350-356. 59. Mirzakouchaki B, Shahrbaf S, Talebiyan R. Determining tooth size ratio in an Iranian-Azari population. J Contemp Dent Pract. 2007;8:86-93. 60. Lundström A. Intermaxillary tooth width ratio and tooth alignment and occlusion. Acta Odontol Scand. 1955;12:265292. 61. Othman S, Harradine N. Tooth size discrepancies in an orthodontic population. Angle Orthod. 2007;77:668-674. 62. Othman SA, Harradine NWT. Tooth-size discrepancy and 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. Literature Cited 1. Ballard M. Asymmetry in Tooth Size: A Factor in the Etiology, Diagnosis and Treatment of Malocclusion. Angle Orthod. 1944;14:67-71. 2. Neff CW. Tailored occlusion with the anterior coefficient. Am J Orthod. 1949;35:309-313. 3. Bolton WA. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod. 1958;28:113-130. 4. Bolton WA. The clinical application of a tooth-size analysis. Am J Orthod. 1962;48:504-529. 5. Sanin C, Savara BS. An analysis of permanent mesiodistal crown size. Am J Orthod. 1971;59:488-500. 6. Lavelle CL. Maxillary and mandibular tooth size in different racial groups and in different occlusal categories. Am J Orthod. 1972;61:29-37. 7. Arya BS, Savara BS, Thomas D, Clarkson Q. Relation of sex and occlusion to mesiodistal tooth size. Am J Orthod. 1974;66:479-486. 59 8. Crosby DR, Alexander CG. The occurrence of tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop. 1989;95:457-461. 9. Freeman JE, Maskeroni AJ, Lorton L. Frequency of Bolton tooth-size discrepancies among orthodontic patients. Am J Orthod Dentofacial Orthop. 1996;110:24-27. 10. Nie Q, Lin J. Comparison of intermaxillary tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop. 1999;116:539-544. 11. Smith SS, Buschang PH, Watanabe E. Interarch tooth size relationships of 3 populations: "does Bolton's analysis apply?". Am J Orthod Dentofacial Orthop. 2000;117:169-174. 12. Ta TA, Ling JY, Hägg U. Tooth-size discrepancies among different occlusion groups of southern Chinese children. Am J Orthod Dentofacial Orthop. 2001;120:556-558. 13. Alkofide E, Hashim H. Intermaxillary tooth size discrepancies among different malocclusion classes: a comparative study. J Clin Pediatr Dent. 2002;26:383-387. 14. Araujo E, Souki M. Bolton anterior tooth size discrepancies among different malocclusion groups. Angle Orthod. 2003;73:307-313. 15. Uysal T, Sari Z, Basciftci FA, Memili B. Intermaxillary tooth size discrepancy and malocclusion: is there a relation? Angle Orthod. 2005;75:208-213. 16. Al-Tamimi T, Hashim HA. Bolton tooth-size ratio revisited. World J Orthod. 2005;6:289-295. 17. Uysal T, Sari Z. Intermaxillary tooth size discrepancy and mesiodistal crown dimensions for a Turkish population. Am J Orthod Dentofacial Orthop. 2005;128:226-230. 18. Fattahi HR, Pakshir HR, Hedayati Z. Comparison of tooth size discrepancies among different malocclusion groups. Eur J Orthod. 2006;28:491-495. 19. Endo T, Abe R, Kuroki H, Oka K, Shimooka S. Tooth size discrepancies among different malocclusions in a Japanese orthodontic population. Angle Orthod. 2008;78:994-999. 60 20. Hashim HA, Al-Ghamdi S. Tooth width and arch dimensions in normal and malocclusion samples: an odontometric study. J Contemp Dent Pract. 2005;6:36-51. 21. Potter RH, Alcazaren AB, Herbosa FM, Tomaneng J. Dimensional characteristics of the Filipino dentition. Am J Phys Anthropol. 1981;55:33-42. 22. Hattab FN, al-Khateeb S, Sultan I. Mesiodistal crown diameters of permanent teeth in Jordanians. Arch Oral Biol. 1996;41:641-645. 23. Axelsson G, Kirveskari P. Crown size of permanent teeth in Icelanders. Acta Odontol Scand. 1983;41:181-186. 24. Richardson ER, Malhotra SK. Mesiodistal crown dimension of the permanent dentition of American Negroes. Am J Orthod. 1975;68:157-164. 25. Keene HJ. Mesiodistal crown diameters of permanent teeth in male American Negroes. Am J Orthod. 1979;76:95-99. 26. Paredes V, Gandia JL, Cibrian R. Do Bolton's ratios apply to a Spanish population? Am J Orthod Dentofacial Orthop. 2006;129:428-430. 27. Haralabakis NB, Sifakakis I, Papagrigorakis M, Papadakis G. The correlation of sexual dimorphism in tooth size and arch form. World J Orthod. 2006;7:254-260. 28. Schwartz GT, Dean MC. Sexual dimorphism in modern human permanent teeth. Am J Phys Anthropol. 2005;128:312-317. 29. Guatelli-Steinberg D, Sciulli PW, Betsinger TK. Dental crown size and sex hormone concentrations: another look at the development of sexual dimorphism. Am J Phys Anthropol. 2008;137:324-333. 30. Basaran G, Selek M, Hamamci O, Akkuş Z. Intermaxillary Bolton tooth size discrepancies among different malocclusion groups. Angle Orthod. 2006;76:26-30. 31. Endo T, Shundo I, Abe R, Ishida K, Yoshino S, Shimooka S. Applicability of Bolton's tooth size ratios to a Japanese orthodontic population. Odontology. 2007;95:57-60. 61 32. Stifter J. A Study Of Pont's, Howes', Rees', Neff's And Bolton's Analyses On Class I Adult Dentitions*. Angle Orthod. 1958;95:457-461. 33. Sperry T, Worms F, Isaacson R, Speidel T. Tooth-size discrepancy in mandibular prognathism. Am J Orthod. 1977;72:183-190. 34. Heusdens M, Dermaut L, Verbeeck R. The effect of tooth size discrepancy on occlusion: An experimental study. Am J Orthod Dentofacial Orthop. 2000;117:184-191. 35. Laino A, Quaremba G, Paduano S, Stanzione S. Prevalence of tooth-size discrepancy among different malocclusion groups. Prog Orthod. 2003;4:37-44. 36. Bernabé E, Major PW, Flores-Mir C. Tooth-width ratio discrepancies in a sample of Peruvian adolescents. Am J Orthod Dentofacial Orthop. 2004;125:361-365. 37. Nourallah AW, Splieth CH, Schwahn C, Khurdaji M. Standardizing interarch tooth-size harmony in a Syrian population. Angle Orthod. 2005;75:996-999. 38. Akyalçin S, Doğan S, Dinçer B, Erdinc AME, Oncağ G. Bolton tooth size discrepancies in skeletal Class I individuals presenting with different dental angle classifications. Angle Orthod. 2006;76:637-643. 39. Freire SM, Nishio C, Mendes ADM, Quintão CCA, Almeida MA. Relationship between dental size and normal occlusion in Brazilian patients. Braz Dent J. 2007;18:253-257. 40. Oktay H, Ulukaya E. Intermaxillary tooth size discrepancies among different malocclusion groups. Eur J Orthod. 2009. Available at: http://www.ncbi.nlm.nih.gov/pubmed/19729399 [Accessed October 11, 2009]. 41. Lundström A. Intermaxillary tooth width ratio and tooth alignment and occlusion. Acta Odontol Scand. 1955;12:265292. 42. Ho CT, Freer TJ. The graphical analysis of tooth width discrepancy. Aust Orthod J. 1994;13:64-70. 62 43. Santoro M, Ayoub ME, Pardi VA, Cangialosi TJ. Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans. Angle Orthod. 2000;70:303-307. 44. Mirzakouchaki B, Shahrbaf S, Talebiyan R. Determining tooth size ratio in an Iranian-Azari population. J Contemp Dent Pract. 2007;8:86-93. 45. Othman S, Harradine N. Tooth size discrepancies in an orthodontic population. Angle Orthod. 2007;77:668-674. 46. Othman SA, Harradine NWT. Tooth-size discrepancy and Bolton's ratios: a literature review. J Orthod. 2006;33:4551; discussion 29. 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