Prevalence of Bolton tooth–size discrepancies among Iranian orthodontic patients

Objectives: The purpose of this study was to evaluate the prevalence of tooth-size discrepancies among orthodontic patients by performing Bolton analysis on them.

Methods: For this reason, 300 pairs of study casts of skeletal cl I , II , III and crowding were selected which had good quality and permanent teeth were present except second and third permanent molars. All teeth were morphologically normal, without any attrition, caries or restorations on their interproximal surface. The greatest mesiodistal diameter was measured to the nearest 0.01 mm by means of digimatic calipers. Then Bolton's Anterior and overall ratios were preformed on these models to find tooth-size discrepancies. The amount of obtained ratios were compared with Bolton's ratios, and the difference over 2SD was considered significant.

Results: The amount of Anterior and Overall ratios found to be 78.34 ± 2.58 and 92.31 ± 2.63 respectfully. Statistically there were significant differences compared with Bolton's means. 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 had tooth-size discrepancies. Even though the means of Anterior and overall ratios in this study were significantly different from Bolton's results, but the amount of differences were not more than 1.5 mm. According to Proffit, the discrepancy less than 1.5 mm is rarely important, hence we can apply the Bolton's ratios for Iranian people, accepting that our measurements can be different to +1.21.

Conclusions: Regarding tooth-size discrepancies specially in anterior crowding cases are not detectable by inspection alone, therefore, it is suggested that Bolton's tooth-size analysis be performed before initiation of orthodontic treatment.