Abstract
Objectives:The aims of this investigation in a group of Emiratis were (1) To study overall and anterior tooth size ratios in Class I normal occlusion, (2) To estimate overall and anterior tooth size ratios in different malocclusion groups, (3) To compare overall and anterior tooth size ratios in Class I normal occlusion with the Bolton standards, and (4) To determine the distribution of overall and anterior tooth size ratios ± 2 SD from Bolton mean values in all occlusion groups.Materials and Methods:In this cross-sectional investigation, consecutive patients’ files, including dental casts, were selected from the archives of orthodontic clinics of the Dubai Health Authority. The final sample was formed following the application of specific inclusion criteria. The sample consisted of 521 pairs of dental casts representing both sexes (males: 188; females: 333) and different malocclusion groups (Class I: 288; Class II: 110; Class III: 30) and Class I normal occlusion (93). The mean age of patients was 16.18y for Class I, 15.73y for Class II, 15.83y for Class III, and 16.55y for Class I normal occlusion. The dental casts were scanned and digitized by the first author using the Ortho Insight 3D laser scanner. Measurements were made regarding maxillary and mandibular sums of mesiodistal tooth dimension of the overall (6-6) and anterior (3-3) groups of teeth. Statistical analysis included descriptive statistics, paired t-test and Analysis of Variance (ANOVA). The level of significance was set at p<0.05.Results:There were statistically significant differences among malocclusion groups with regard to overall and anterior tooth size ratios. However, the comparison between the Class I normal occlusion group and the Bolton standards showed no statistically significant differences. Only five cases in Class II malocclusion presented an anterior tooth size discrepancy outside plus 2 SD from Bolton mean values and one case in Class I malocclusion presented with an overall tooth size discrepancy outside plus 2 SD from Bolton mean values.Conclusion:This study of the different occlusion groups of the Emirati sample concluded that (a) Class I normal occlusion cases presented similar overall and anterior tooth size ratios to Bolton standards; (b) Overall and anterior tooth size ratios among different malocclusion groups exhibited statistically significant differences; (c) Five cases in Class II malocclusion presented an anterior tooth size discrepancy outside plus 2 SD from Bolton mean values, and (d) One case in Class I malocclusion presented an overall tooth size discrepancy outside plus 2 SD from Bolton mean values.
Highlights
After completing orthodontic treatment, specific dimensional relationships should exist between the maxillary and mandibular teeth to ensure ideal conditions of interdigitation, overjet and overbite [ 1 ]
Five cases in Class II malocclusion presented an anterior tooth size discrepancy outside plus 2 SD from Bolton mean values and one case in Class I malocclusion presented with an overall tooth size discrepancy outside plus 2 SD from Bolton mean values
No statistically significant differences in overall and anterior tooth size ratios were found in relation to gender (Table 4) and between the normal occlusion Emirati group and the Bolton standards (Table 5)
Summary
Specific dimensional relationships should exist between the maxillary and mandibular teeth to ensure ideal conditions of interdigitation, overjet and overbite [ 1 ]. Since natural teeth match well in most individuals, tooth size discrepancy of less than 1.5 mm is rarely significant, but larger discrepancies create treatment problems and must be included in the orthodontic problem list [ 2 ]. Patients with interarch tooth size discrepancies typically require special finishing steps, such as enamel removal (interproximal reduction) or crown material addition (composite buildups or porcelain veneers), to correct this discrepancy so that the teeth occlude harmoniously. The degree of disproportional relationships between upper and lower teeth (in total or anterior) with regard to the mesiodistal dimension, often called Bolton analysis after its developer, is carried out by measuring the mesiodistal width of each permanent tooth excluding second and third molars [ 3 ]. Bolton concluded that the normal ratio for physiologic occlusion is an overall ratio of 91.3+1.91 and an anterior ratio of 77.2+1.65 [ 4, 5 ]
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