[Dentoalveolar compensation in skeletal Class III patients treated with orthognathic surgery]

To investigate the compensation of the upper and lower incisors in skeletal Class III patients treated with orthodontic-surgical approach.

The samples consisted of 54 skeletal Class III patients treated with orthodontic-surgical approach from November 2011 to January 2015. Lateral cephalograms were taken before treatment. The differences between the samples and the norms from Peking University normal occlusion sample library were assessed using independent-sample t test. Correlation analyses were performed to find associations between skeletal and dental parameters. According to skeletal anteroposterior discrepancy/vertical type (ANB/SN-MP), the samples were allocated into group A (ANB < -4°, SN-MP ≤ 37.7°, n = 11), group B (ANB ≥ -4°, SN-MP ≤ 37.7°, n = 16), group C (ANB < -4°, SN-MP > 37.7°, n = 14), and group D (ANB ≥ -4°, SN-MP > 37.7°, n = 13). After measurement of variables, one-way ANOVA with SNK multiple comparison test were performed.

The maxillary incisors were more proclined and the mandibular incisors more retroclined in skeletal Class III patients compared with norm values (P < 0.01). Both skeletal anteroposterior discrepancy and vertical type were correlated with the position of upper and lower incisors (P < 0.01). According to skeletal anteroposterior discrepancy/vertical type, no significant differences were found in the upper incisors' inclination among the four groups, while patients in group A and group D exhibited significant difference in lower incisor compensation.

Different skeletal anteroposterior discrepancy/vertical type resulted in varied incisors' compensation. Therefore, decompensation should be treated differently.