[Comparison between computer aided simulation and dental model orthognathic surgery for the treatment of patients with mandibular excess and facial asymmetries].

Objective: To evaluate the results of the orthognathic surgery with computer aided simulation-three-dimensional(3D) printed surgical guide and dental model surgery in the treatmemt of patients with mandibular excess and facial asymmetries. Methods: The coordinate system was built in ProPlan CMF 2.0 software, and the horizontal plane consisted of PoL, PoR, OrL, middle sagittal plane through nasion point and basion point and the plane perpendicular to the horizontal plane, coronoid plane through nasion point and the plane perpendicular to the horizontal plane and middle sagittal plane. The orientation of maxilla and mandibular distal segment was calculated by each triangle(U1-U6L-U6R, L1-L6L-L6R, Me-M5L-M5R) before and after orthognathic surgery. A total of 60 mandibular excess patients with facial asymmetries were enrolled in this retrospective study. They were divided into two groups, group Ⅰ with computer aided simulation, group Ⅱ with dental model surgery. The difference of maxillary occlusal plane roll and yaw angle, mandibular occlusal plane roll and yaw angle, and mandibular body plane roll and yaw angle were calculated. Statistical analysis was performed with SPSS 17.0 software. Results: The yaw angle of mandibular occlusal plane of the dental model surgery and computer aided simulation was 0.36°± 0.48° and 0.84° ± 0.36° ( P= 0.043), respectively. The roll angle of mandibular occlusal plane of the dental model surgery and computer aided simulation was 0.26°±0.79° and 0.54°±0.40°( P= 0.032), respectively. The yaw angle of mandibular body plane of the dental model surgery and computer aided simulation was 0.60°± 1.04° and 0.23°±0.52°( P= 0.008), respectively. The roll angle of mandibular body plane of the dental model surgery and computer aided simulation was 0.82° ± 0.72° and 0.53° ± 0.37° ( P= 0.028), respectively. The changes in computer aided simulation group were more obvious than that in the dental model surgery group, but the difference was not significant in the yaw angle of maxillary occlusal plane and the roll angle of maxillary occlusal plane between the two groups( P >0.05). Conclusions: It was more effective to correct mandibular asymmetry by computer aided simulation than dental model surgery.