Objective The purpose of this study was to analyze the changes of hard tissues at each treatment stage in patients with skeletal Class Ⅲ malocclusion after orthodontic-orthognathic surgery, and to assess the longterm stability after treatment. Methods 24 patients with skeletal Class Ⅲ malocclusion were selected. Standardized lateral cephalograms at the following stages were taken for each patient: Before treatment（T0）, 3 months after surgery （T1）, 1 year after surgery（T2）, 3 years after surgery（T3）. A total of 16 hard tissue landmarks were selected and evaluated at different stages. SPSS 12.0 soft ware was used to study the changes of the hard tissues. Results 1）Comparison of angles between stage T0 and T1, except N-S-Ar, N-S-Ba, N-S-Go, NBa-PtGn and Y axis, other discrepancies all had statistical significances. 2）Comparison of angles between stage T1 and T2, only SNPo and U1-SN had significant differences. 3）Comparison of angles between stage T1 and T3, only U1-SN had an obvious change. 4）Comparison of the angles between stage T2 and T3, all angle changes had no statistical significance. Conclusion From three months to one year after surgery, the hard tissue angles varied more or less, but that did not essentially affect the surgery results. It is concluded that the orthodontic-orthognathic treatment of skeletal Class Ⅲ malocclusion had a long-term stability.
