Peer assessment rating index analysis of different extraction modality in skeletal Class Ⅲ malocclusions

Objective To assess the effect of different extraction modalities on treatment outcomes in skeletal Class Ⅲ malocclusions. Methods One hundred and nine skeletal Class Ⅲ patients (50 males and 59 females) with a mean age of 16.11±4.47 years were collected. The subjects were divided into four groups according to the extraction modality. They were T0 (non-extraction group), T1 (premolar extraction group), T2 (molar extraction group) and T3 (lower incisor extraction group). The PAR (peer assessment rating) index of each of the pre- and post-treatment cast was assessed. The differences of pre- and post-treatment weighed PAR score, reduction in weighed PAR score, percentage reduction in weighed PAR score and the degree of improvement between the four groups were compared. Results (1) Significant differences (P＜0.001＝ of the reduction in weighed PAR score and percentage reduction in weighed PAR score existed between different extraction modality groups. And the order of reduction from high to low was premolar extraction group, molar extraction group, non-extraction group and lower incisor extraction group.(2) There were no "Worse-no different" cases among the four groups. 97 cases were greatly improved and accounted for 89%. There were 12 cases (11%) in improved category. (3) Greatest improvement was found in premolar extraction group and the least improvement was found in lower incisor extraction group. Conclusions Treatment outcomes of the four extraction modalities in skeletal Class Ⅲ were all satisfied. Cautions should be paid in lower incisor extraction.