Comparison of the Bolton index and Bolton tooth size discrepancies between Class II1 and II2 malocclusion

Objective To compare the Bolton index and Bolton tooth size discrepancies between Class II1 and Class II2 cases. Methods 129 casts of Class II1 patients and 81 casts of Class II2 patients were selected. Mesiodistal width of teeth was measured and Bolton index was calculated. According to Bolton rate standards, the tooth size discrepancies were calculated. Statistical analysis was made between these two groups. Results ① The total Bolton index in Class II2 cases (0.92±0.02) was significantly larger than that in Class II1 cases (0.91±0.02),(P=0.044). There were no significant differences of the anterior Bolton index between these two classes of malocclusion （P=0.240）. ② The anterior Bolton tooth size discrepancies in Class II2 patients (1.05±0.96) were significantly larger than that in Class II1 patients (0.73±0.60), (P=0.044). There were no significant differences of the total Bolton tooth sizediscrepancies between the two classes （P=0.664）. Conclusions There were differences of the Bolton index and Bolton tooth size discrepancies between Class II1 and Class II2 patients. Key words: Angle class Ⅱ division 1;  Angle class Ⅱ division 2;  Bolton index;  Bolton tooth size discrepancy