AIM: To determine the size of individual permanent teeth together with Bolton’s ratios in an Italian population, and to compare the distribution of clinically significant tooth size discrepancy (TSD) according to both Bolton’s rule method and a millimetric method.
MATERIALS AND METHOD: Dental casts of 150 Italian subjects (90 females mean age 15.9 ± 6.4 years, 60 males 14.5 ± 4.2 years). TSD was calculated considering both Bolton’s index [mean ± standard (SD)] and millimetric discrepancy. RESULTS: Overall and anterior Bolton’s ratios (%) were 91.3 ± 2.0 and 77.9 ± 2.7, respectively. According to Bolton’s rule, the normal range set is within the mean ± 2 SD range, 5.3 and 20.0 per cent in the overall and anterior Bolton ratios, respectively, were out of such normality. However, greater frequencies of 52.6 and 21.4 per cent in the overall and anterior millimetric discrepancies, respectively, were above 1.5 mm. By merging the overall and the anterior millimetric discrepancies, up to 56.7 per cent of the sample presented a value of at least 1.5 mm. No differences between genders were seen.
CONCLUSION: There were relevant differences in the interpretation of the degree of TSD between Bolton’s index rule and absolute millimetric discrepancies. The rule of the 2 SD range was not able to detect all clinically relevant TSDs. An underestimation of TSD using the current Bolton rule may not lead to optimal case finishing at the end of fixed orthodontic treatment.
