Abstract: PURPOSE: To investigate the changes of soft and hard tissue after bimaxillary surgery in osseous Class Ⅲ patients, in order to predict postoperative soft tissue profiles. METHODS: Twenty-six adults patients were selected as the experimental group, cone-beam CT (CBCT) scans were conducted. InVivo 5 software was used to transform CBCT into cephalogram from CBCT(CCB) which were imported into the software named Geometer's Sketchpad. All points were measured in the system of rectangular coordinates and were used for statistical analysis SPSS17.0 software package. RESULTS: There was a linear relationship between soft and hard tissue. The correlation in mandible was stronger than that in maxilla, Sn:A=0.18:1, UL:Ui=0.31:1, LL:Li=0.80:1,Si:B=0.84:1,Pg':Pg=0.90:1. There was no correlation between the thickness of nasal floor and the changes of the soft and hard tissue. The same was the thickness of chin. There was negative correlation in the thickness of lip with the soft and hard tissue changes. The upper lip became thinner, the lower lip became thicker. CONCLUSIONS: There was a linear correlation between the hard tissue and the soft tissue. The correlation and ratio of mandible was stronger than maxilla. Changes of hard tissue had major effects on the soft tissue of nasal floor and chin, but minor effects on lip. There was better mobility in thinner upper lip than thicker lip.

Key words: Osseous Class Ⅲ, malocclusion deformity, Hard and soft tissue correlation, Thickness of soft tissue, Cone-beam CT, Cephalogram