数字化设计矫治下颌前突偏斜畸形的疗效评估

Evaluation of therapeutic effect of virtual design for correcting facial asymmetry of skeletal ClassⅢdeformity

目的：对下颌前突偏斜畸形患者进行数字化矫治方案设计，并评价其矫治效果，以期为临床提供参考。方法将符合纳入标准的下颌前突偏斜畸形患者35例采用随机数表方式分为2组，于自然头位下，数字化组（16例）行数字化矫治方案设计并进行手术，对照组（19例）行传统术前设计并进行手术。于术前和术后6个月分别用3dMDface系统三维照相机拍摄面部三维照片，通过计算软组织标志点的不对称系数（asymmetry index，AI）评价两组不对称畸形的矫治效果。结果术后6个月数字化组鼻下点、上唇缘点、人中嵴点、颏前点、下颌角点AI值[分别为（0.81±0.50）、（1.01±0.80）、（1.94±1.30）、（1.60±1.20）及（5.68±2.25）mm]显著小于对照组[分别为（1.49±1.10）、（1.79±1.33）、（3.52±2.50）、（2.79±2.08）及（8.43±3.94）mm]（P〈0.05）。结论基于自然头位的数字化矫治方案设计较传统设计能更有效地矫正下颌前突偏斜患者的面部不对称畸形。

Objective To establish a computer-aided surgical simulation procedure based on the natural head position（NHP） for orthognathic surgery and to access the effect for correcting facial asymmetry for skeletal Class Ⅲ deformity. Methods Thirty-five patients（male： 14 and female： 21, mean age： [21.5 ± 2.3] years） of skeletal Class Ⅲ deformity with facial asymmetry were included and divided into virtual group （16 patients） and control group（19 patients）. The computer-aided surgical simulation procedure was used in the virtual group and the intermediate and final splints were fabricated using the rapid protyping technique. The traditional model surgery based on plaster casts was used in control group, and the splints were handmade. To evaluate the symmetry, three-dimensional（3D） photos were taken for all the patients before operation and 6 months after operation using the 3dMD face imaging system. Coordinate system was built based on mirror-original alignment method on the 3D photo. Thirteen soft tissue landmarks were marked on each 3D photo. The asymmetry index（AI） of those soft tissue landmarks was calculated. Results There was no significant difference in the AI values between the two groups before surgery. Sixth month after operation, the mean AI values in the virtual group were （0.81 ± 0.50） mm for subnasale, （1.01 ± 0.80） mm for labiale superius, （1.94 ± 1.30） mm for crista philtri, （1.60 ± 1.20） mm for pogonion and （5.68 ± 2.25） mm for gonion. The mean AI values in the control group were （1.49 ± 1.10） mm for subnasale, （1.79 ± 1.33） mm for labiale superius, （3.52±2.50） mm for crista philtri, （2.79±2.08） mm for pogonion and （8.43±3.94） mm for gonion and those indexes were significantly different between the two groups（P〈0.05）. There was no significant difference in the AI values of the pronasale, alare, labiale inferius and cheilion between the two groups sixth month after operation. Conclusions The introduced procedure of the virtual design based on the estimated NHP could more effectively correct the asymmetry deformity for the skeletal ClassⅢpatients.