Specific dimensional relationships must exist between

ORIGINAL ARTICLE Intermaxillary tooth size discrepancy and mesiodistal crown dimensions for a Turkish population Tancan Uysal a and Zafer Sari b Kayseri and Konya, Turkey Introduction: The aims of this study were to determine the size of individual permanent teeth, tooth-size ratios for the maxillary and mandibular dentitions, and sex differences for those variables in a Turkish population, and to compare the figures obtained with those of the Bolton analysis. Methods: The data were derived from dental casts of 150 Turkish subjects (72 men, mean age 22.09 3.11 years; 78 women, mean age, 21.11 2.08 years) with normal occlusions. The mean, standard deviation, and minimum and maximum values were calculated for individual tooth size, and overall and anterior ratios, separately for men and women. To determine whether there are sex differences in intermaxillary tooth size discrepancies, an independent samples t test was performed. Results: The mesiodistal dimensions of the maxillary teeth showed greater variability than the mandibular teeth, with the first molar dimensions having the greatest variability. The overall and anterior ratios were found to be 89.88 2.29 and 78.26 2.61, respectively. A statistically significant sex difference was found only in overall ratio (P.001). According to Bolton s mean values, a discrepancy in the overall ratio was found in 18% of Turkish normal occlusion subjects, and anterior ratios outside 2 standard deviations from the Bolton mean were found in 21.3% of our sample. Conclusions: These findings indicate that population-specific standards are necessary for clinical assessments. Bolton s original data do not represent Turkish people, and therefore it is appropriate to use Turkish norms in daily orthodontic practice for Turkish patients. (Am J Orthod Dentofacial Orthop 2005;128:226-30) Specific dimensional relationships must exist between the maxillary and mandibular teeth to ensure proper interdigitation, overbite, and overjet. Because patients with interarch tooth-size discrepancies require either removal (eg, interdental stripping) or addition (eg, composite build-ups/porcelain veneers) of tooth structure to open or close spaces in the opposite arch, it is important to determine the amount and location of tooth-size discrepancies before starting treatment. 1 Many studies have shown a correlation between the mesiodistal tooth width of the maxillary and mandibuler teeth. 2-5 Bolton 6 analyzed the relationship between the mesiodistal tooth width of the maxillary and mandibular teeth by studying 55 white subjects with excellent occlusions. Using the mesiodistal width of 12 teeth, he obtained an overall ratio of 91.3% 1.91%; a Assistant professor, Department of Orthodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey. b Assistant professor, Department of Orthodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey. Reprint requests to: Dr Tancan Uysal, Erciyes Üniversitesi, Diş Hekimliǧi Fakültesi Ortodonti A.D. Kayseri, 38039, Turkey; e-mail, tancanuysal@yahoo.com. Submitted, November 2003; revised and accepted, April 2004. 0889-5406/$30.00 Copyright 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2004.04.029 using the 6 anterior teeth, he obtained an anterior ratio of 77.2% 1.65%. Stifer 7 replicated Bolton s study in Class I dentitions and reported similar results. Subsequently, other authors obtained the normal values of Bolton analysis of different races, eg, that of Chinese, 8-10 black, Hispanic, and white 1 populations. Most investigators concluded that there are significant differences among ethnic and racial groups, and, as a result, many standards have been developed. Most studies indicated that normal measurements for 1 group should not be considered normal for other race and ethnic groups. Different racial groups must be treated according to their own characteristics. Smith et al 1 derived data from systematically collected preorthodontic casts of 180 patients, including 30 men and 30 women from each of black, Hispanic, and white groups. They concluded that Bolton ratios apply to white women only; the ratios should not be indiscriminately applied to white men, blacks, or Hispanics. Lew and Keng, 8 studying a group of Singaporian Chinese, reported an anterior ratio comparable with the Bolton standard, even though Singaporean Chinese had smaller maxillary central incisors and larger maxillary lateral incisors. Mesiodistal tooth sizes in southern 226

American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 2 Uysal and Sari 227 Chinese people were found to be generally larger than those of other Chinese subraces 9 or whites. 10 Such variation in mesiodistal dimensions could affect the anterior and overall ratios between the maxillary and mandibular teeth. 11 Arya et al 12 showed that there were differences in tooth size between sexes, as reported by other authors. Lavelle 13 showed that there was sexual dimorphism in tooth dimensions and in the ratio of maxillary to mandibular arch tooth size. No published data establish Bolton values for diagnosis and treatment planning of Turkish patients. With these points in mind and using the analysis of Bolton, we attempted to determine sizes of individual permanent teeth, tooth-size ratios for the maxillary and mandibular dentitions, and sex difference for those variables, and to compare these figures with those of the Bolton analysis for the Turkish population. MATERIAL AND METHODS Orthodontic dental casts were taken from 150 Turkish subjects (72 men, mean age 22.00 3.11 years and 78 women, mean age, 21.11 2.08 years) with normal occlusions and well-balanced faces. The following selection criteria were used: (1) Turkish with Turkish parents, 20 to 35 years of age; (2) Class I occlusion with minor or no crowding; (3) well-aligned dental arches; and (4) good-quality study models. The following rejection criteria were used: (1) gross restorations, buildups, crowns, onlays, Class II amalgams, or composite restorations that affect a tooth s mesiodistal diameter; (2) congenital defects or deformed teeth; and (3) obvious interproximal or occlusal wear of teeth. A digital caliper was used to measure the casts to the nearest 0.01 mm. The mesiodistal crown diameters of all teeth were measured according to the method described by Moorrees et al. 14 The width of each tooth was measured from its mesial contact point to its distal contact point at its greatest interproximal distance. Bolton anterior (canine to the canine) and overall (first molar to first molar) ratios were calculated with the following formulas: Sum mandibular 12 100 overall ratio (%) Sum maxillary 12 Sum mandibular 6 100 anterior ratio (%) Sum maxillary 6 Bolton s normal-range values were used in the comparisons of Turkish values. According to the Bolton analysis, a significant discrepancy was defined as one whose value was outside 2 SD from Bolton s mean 15 because approximately 95% of Bolton s subjects were within this range. For the overall 12 ratio, a significant discrepancy is therefore defined as a ratio below 87.5 or above 95.1, with ratios in between falling within 2 SD of Bolton s mean. Likewise, any ratio below 73.9 or above 80.5 was considered to be a significant discrepancy for the anterior 6 ratio. To determine the errors associated with measurements, 25 dental casts were selected randomly. Their measurements were repeated 8 weeks after the first measurements. A paired t test was applied to the first and second measurements. All statistical analyses were performed with a software package (Statistical Package for Social Sciences, Windows 98, version 10.0, SPSS, Chicago, Ill). For each variable, mean, standard deviation, minimum, and maximum values were calculated and also separately for men and women. To determine whether there were sex differences in intermaxillary tooth-size discrepancies, an independent samples t test was performed. RESULTS The skewness and kurtosis statistics showed that the variables were normally distributed. It was found that the difference was insignificant between the first and second measurements of the 25 dental casts to determine the errors associated with the measurements. The molars had the largest errors; the premolars and the canines had the smallest errors. Table I shows the mean, range, and standard deviation of the width of the maxillary and mandibular teeth in the male and female subgroups. The mean overall 12 ratio for the Turkish population was found to be 89.8 (Table II), with a standard deviation of 2.29. The values ranged from 84.9 to 98.6, and the median was 90.0. The mean anterior 6 ratio for the Turkish population was found to be 78.2, with a standard deviation of 2.61. The values ranged from 72.4 to 88.4, and the median was 78.0. The following results were obtained through the independent samples t test applied to compare the measurement differences of men and women. The mean anterior and overall ratios for Turkish men and women are shown in Table II. A statistically significant sex difference was found in the overall ratio (P.001). The overall ratios were 89.8 for men and 91.7 for the women. In our sample, both men s and women s anterior ratio measurements followed similar distribution patterns, with the men having slightly larger dimensions. The anterior ratios were 78.1 for men and 78.3 for women. The frequency of tooth-size discrepancy outside 2

228 Uysal and Sari American Journal of Orthodontics and Dentofacial Orthopedics August 2005 Table I. Permanent tooth widths in Turkish adults (78 women, 72 men) Men Women Total Tooth Mean (mm) SD Range Mean (mm) SD Range Mean (mm) SD Range Maxillary I1 8.4 0.53 7.4-10.0 8.4 0.48 7.5-9.9 8.4 0.50 7.3-9.9 I2 6.7 0.54 5.7-7.9 6.6 0.56 5.1-8.3 6.7 0.55 5.1-8.3 C 7.7 0.48 6.5-9.4 7.6 0.45 6.8-8.7 7.7 0.46 6.4-9.3 P1 6.9 0.47 6.2-8.1 6.9 0.50 5.8-8.2 6.9 0.49 5.8-8.2 P2 6.7 0.49 5.8-7.8 6.7 0.49 5.8-7.7 6.7 0.49 5.8-7.7 M 10.3 0.55 9.4-11.5 10.1 0.58 9.3-11.7 10.2 0.57 9.3-11.7 Mandibular I1 5.3 0.29 4.7-6.1 5.3 0.32 4.6-6.1 5.3 0.30 4.6-6.1 I2 5.8 0.35 5.2-6.7 5.8 0.33 5.2-6.9 5.8 0.34 5.2-6.9 C 6.7 0.42 6.0-8.0 6.6 0.38 5.9-7.8 6.6 0.40 5.9-8.0 P1 6.9 0.44 6.0-8.1 6.9 0.45 6.0-8.3 6.9 0.45 6.0-8.3 P2 7.1 0.46 6.3-8.3 7.1 0.46 6.0-8.3 7.1 0.45 6.0-8.3 M 11.0 0.45 10.0-12.2 10.8 0.54 9.7-12.2 10.9 0.50 9.7-12.2 I1, Central incisor; I2, lateral incisor; C, canine; P1, first premolar; P2, second premolar; M, first molar. Table II. Maxillary and mandibulor tooth-size ratios in 150 Turkish adults (78 women, 72 men) Overall ratio Anterior ratio Descriptives Total Women Men P value Total Women Men P value Sample size 150 78.00 72.00 150 78.00 72.00 Mean 89.88 91.73 89.83 78.26 78.33 78.18 SD 2.29 2.26 2.33 2.61 2.42 2.82 Median 90.00 92.00 90.00 78.00 78.00 78.00 Range 84.91-98.68 87.36-100.84 84.91-95.75 * 72.47-88.43 73.64-84.23 72.47-8843 NS SE of mean 0.19 0.25 0.27 0.21 0.27 0.33 Skewness 0.50 0.97 0.22 0.50 0.40 0.60 SE of skewness 0.20 0.27 0.28 0.20 0.27 0.28 Kurtosis 0.82 2.93 0.31 0.69 0.30 1.28 SE of kurtosis 0.39 0.54 0.56 0.39 0.54 0.56 SD, Standard deviation; SE, standard error; NS, not significant; *P.001. standard deviations from the Bolton mean for overall and anterior ratio was calculated in a normal sample of Turkish adults. Figures 1 and 2 summarize the Turkish values according to Bolton s mean. DISCUSSION In this study, a young group was chosen to minimize the alteration of the mesiodistal tooth dimensions because of factors such as attrition, restoration, or caries. The mesiodistal dimensions of the maxillary teeth showed greater variability than the mandibular teeth, with the first molar dimensions having the greatest variability. The size of the maxillary lateral incisor also was highly variable. In addition, the individual toothsize data reported by Santoro et al 16 imply high variability for the maxillary first molar and lateral incisor; this agrees with our findings. This suggests that these teeth could be responsible for incongruity in the anterior ratio and should be examined clinically at the beginning of treatment to detect any major size and shape variations. The values obtained in this study resemble very closely the data available for Dominican American, 16 Dominican, 17 and North American 18 groups. Most of the values were slightly lower than those for the other populations. These differences could be attributed to differences in measurement techniques among these studies or even to different nutrition regimens in these populations. The mean overall 12 ratio from first molar to first molar of the normal Turkish occlusion group was found to be 89.88, with a standard deviation of 2.29. This ratio was 93.2 2.48 19 and 90.9 1.10 9 in Chinese, 91.3 1.91 in Dominican Americans, 16 92.30 in whites, 93.40 in blacks, and 93.1 in Hispanics. 1 In general, the Turkish sample in this study resembles more closely the Chinese 9 and Dominican American 16 samples than the others.

American Journal of Orthodontics and Dentofacial Orthopedics Volume 128, Number 2 Uysal and Sari 229 Fig 1. Distribution of 150 Turkish adults overall tooth-size ratios according to Bolton s mean and 2 SD. Fig 2. Distribution of 150 Turkish adults anterior tooth size ratios according to Bolton s mean and 2 SD. The mean anterior 6 ratio from canine to canine for the Turkish group was found to be 78.26, with a standard deviation of 2.61. This ratio was 77.5 1.8 9 in Chinese, 78.1 2.87 in Dominican Americans, 16 79.6 in whites, 79.3 in blacks, and 80.5 in Hispanics. 1 The Turkish samples anterior ratio mean value resembles those values closely. There were significant differences between men and women. The statistically significant difference was due to both the anterior and posterior arch-segment relationships, even though only the posterior ratio showed a significant difference. Both men s and women s anterior ratio measurements had similar distribution patterns. Significant overall differences could be explained by the relatively larger mandibular arch segments of men. Nie and Lin 19 found no statistically significant sex differences in their Chinese population. Smith et al 1 found larger overall ratios in men in black, Hispanic, and white populations. Lavelle 13 also reported relatively larger overall ratios in men compared with women in white, black, and Mongoloid populations. The tooth-size data reported by Moorrees 11 and Moorrees et al 14 also imply sex differences in the overall ratio; this agrees with our findings. Other studies with similar ratios for men and women suggest that sex differences in the overall ratio might be population-specific. 20,21 Bolton s original sample might have been composed primarily of white women; this suggests that the Bolton ratio applies only to white women. 1 Although Bolton s published results did not specify the number of men and women or their ethnicity, most orthodontic patients in the 1950s were white women. 22 Both Turkish men s and women s overall

230 Uysal and Sari American Journal of Orthodontics and Dentofacial Orthopedics August 2005 and anterior ratios fell within 1 standard deviation confidence interval. The frequency of tooth-size discrepancy outside 2 standard deviations from Bolton s was used as the index of the clinical significance of tooth-size imbalance in our normal sample. A discrepancy in the overall ratio was found in 18% of Turkish subjects with normal occlusions (24 subjects [16%] 87.5 and 3 subjects [2%] 95.1). The discrepancy in the anterior and overall ratio outside 2 standard deviations from the Bolton mean was 29.71% in our sample. In other populations, values of 13.4% for overall ratio 17 and 30.6%, 17 28%, 16 and 22.9% 23 for anterior ratio were reported. CONCLUSIONS Bolton s original data do not represent Turkish people, and therefore this population-specific normative study was performed. In establishing normative data for tooth size and tooth-size ratios for a sample of 150 Turkish subjects with normal occlusions, the following general conclusions can be drawn: 1. Greater size variability was found in maxillary teeth compared with mandibular teeth. The first molars and the maxillary lateral incisors had significant variability, and these teeth should be examined clinically to exclude any major size and shape discrepancies. 2. The relationships between the sizes of the mandibular and maxillary teeth depend on population and sex. Our study indicated that population-specific standards are necessary for clinical assessments. 3. Significant sex differences were shown for the overall ratio. These differences can be explained by men s relatively larger mandibular arch segments. 4. A discrepancy in the overall ratio was found in 18% of Turkish subjects with normal occlusions, and anterior ratios outside 2 standard deviations from the Bolton mean were found in 21.3% of our sample. Even if the values are not significantly higher than previous ones available in the literature for orthodontic patient populations, a careful analysis of interarch relationships should be included in the diagnostic procedures. REFERENCES 1. Smith SS, Buschang PH, Watanabe E. Interarch size relationships of 3 populations: does Bolton s analysis apply? Am J Orthod Dentofacial Orthop 2000;117:169-74. 2. Ling JYK. A morphometric study of the dentition of 12-year-old Chinese children in Hong Kong [thesis]. Hong Kong: University of Hong Kong; 1992. 3. Ballard ML. Asymmetry in tooth size: a factor in the etiology, diagnosis and treatment of malocclusion. Angle Orthod 1944;14: 67-71. 4. Neff CW. Tailored occlusion with the anterior coefficient. Am J Orthod 1949;35:309-14. 5. 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Relation of sex and occlusion to mesiodistal tooth size. Am J Orthod 1974;66:479-86. 13. Lavelle CLB. Maxillary and mandibular tooth size in different racial groups and in different occlusion categories. Am J Orthod 1972;61:29-37. 14. Moorrees CFA, Thomsen SO, Jensen E, Yen PKJ. Mesiodistal crown diameters of the deciduous and permanent teeth in individuals. J Dent Res 1957;36:39-47. 15. Bolton WA. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Am J Orthod 1958;48: 113-30. 16. 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: 303-7. 17. Crosby DR, Alexander CG. The occurrence of tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop 1989;95:457-61. 18. Moyers RE, van Der Linden FPGM, Riolo ML, McNamara JA. Standards of human occlusal development. Monograph 5. Ann Arbor, Mich: Center for Human Growth and Development; University of Michigan; 1976. 19. Nie Q, Lin J. Comparison of maxillary tooth size discrepancies among different malocclusion groups. Am J Orthod Dentofacial Orthop 1999;116:539-44. 20. Garn SM, Lewis AB, Swindler DR. Genetic control of sexual dimorphism in tooth size. J Dent Res 1967;46:963-72. 21. Richardson ER, Malhotra SK. Mesiodistal crown dimension of the permanent dentition of American Negroes. Am J Orthod 1975;68:157-64. 22. Proffit WR. Forty year review of extraction frequencies at the University Orthodontic Clinic. Angle Orthod 1994;64:407-14. 23. Freeman JE, Maskeroni AJ, Lorton L. Frequency of Bolton tooth size discrepancies among orthodontic patients. Am J Orthod Dentofacial Orthop 1996;110:24-7.