Prevalence of tooth size discrepancies (Bolton analysis) in sagittal malocclusions

To evaluate the prevalence of tooth- size discrepancies among orthodontic patients with sagittal malocclusions by performing Bolton analysis. Methods & Materials: Two hundred pairs of study models of skeletal Cl I, II, III and crowding were selected. All permanent teeth were present except second and third molars, without any attrition, caries or restorations on their interproximal surfaces. The greatest mesiodistal diameter was measured to the nearest 0.01 mm by means of digimatic calipers. The Bolton’s anterior and overall ratios were perfomed on these models to find tooth-size discrepancies. The mean, SD, range, CV and SE were assessed. The four groups were compared by variance analysis. The amount of obtained ratios were compared with Bolton’s ratios by T - test, and the difference over 2SD was considered significant. The tooth size discrepancy was more prevalent in crowding group (%14) regarding the overall ratio, and more in cl III group (%28) regarding anterior ratio.The means of Anterior and Overall ratios in the present study(78.21±2.69,92.01±2.45) were larger than Bolton’s measurements (77.2±1.65, 91.3±1.91) (P<0.0001). Even though the means of the tooth size ratios of the current study were significanthy different from Bolton’s results, the amount of differences were not more than 1.5 mm, hence we can apply the Bolton’s ratios for Iranian people. When the Bolton’s results were applied to our study, for the Anterior ratio 23% and for the Overall ratio 9% of patients fell outside of 2SD and tooth-size discrepancies. Regarding tooth- size discrepancies specially in crowding and crossbite cases, which are not detectable by inspection alone, it is suggested that Bolton’s tooth size analysis be performed before starting the orthodontic treatment.