OBJECTIVETo evaluate the effect of extraction and non-extraction decompensation to bimaxillary orthognathic surgery in skeletal class III malocclusion and the effect on postoperative.

METHODSRecords of 36 completed surgical-orthodontic treatment skeletal class III malocclusion patients were obtained from School of Stomatology, China Medical University, 18 underwent maxillary premolar extraction, the other 18 underwent non-extraction. Their post-decompensation and postsurgery cephalometric radiographs were analyzed objectively, and their profile scissors-shadows in different groups were evaluated subjectively.

RESULTSThe cephalometric index of post-presurgical orthodontics showed that there were significant deviations between the extraction and non-extraction groups including U1-SN, Overjet and Cm-Sn-UL values (P<0.05). During surgery, mandible was retruded (8.66 +/- 1.42) mm in extraction group compared with (6.21 +/- 3.06) mm in non-extraction group (P<0.05). After surgery, the extraction group achieved more normal ANB, U1-SN, NA-PA values (P>0.05).

CONCLUSIONMaxillary premolar extraction can make incisor decompensation more complete so that mandible can be retruded to more ideal position and concave face can be successfully corrected.