Class II subdivision treatment success rate with symmetric and asymmetric extraction protocols.

The purpose of this study was to compare the success rates of Class II subdivision malocclusion patients treated with either symmetric or asymmetric extractions. The sample consisted of 51 patients with Class II subdivision malocclusion. The patients were divided into 2 groups. Group 1 included 28 patients who were treated with 4 premolar extractions. The 23 patients in group 2 were treated with 3 premolar extractions (2 maxillary premolars and 1 mandibular premolar on the Class I side). The initial and final study models were evaluated by means of Grainger's treatment priority index (TPI). Individual evaluations of improvements in maxillary-to-mandibular dental midline deviation, overjet, and overbite were also made. The final mean TPI and the mean improvement in TPI and in the other variables of each group were compared with independent t tests. The results showed a statistically significant difference only for the improvement in maxillary-to-mandibular dental midline deviation of the groups. The 3-premolar-extraction group had a greater improvement of the initial interdental midline deviation. There is a tendency for a slightly better treatment success rate when Class II subdivision patients are treated with asymmetric extraction of 3 premolars, compared with extraction of 4 premolars.