Objective To simulate the dynamic procedure of bullet damage to the three-dimensional(3D) finite element(FE) model of mandible from different angle with computer-aided engineering.Methods A mandible was scanned by thin-layer CT,and then CT images were analyzed and managed with Dicom standard and Mimics software.At the same time,a simulation of the 3D FE model penetrated by a 7.62-mm bullet was carried out through LS-DYNA software from different angle.Results A 3D FE model of human mandible was established with highly-identical geometric size,and the dynamic process of bullet damage to the model was successfully simulated.The results of this work indicated that the exit wounds in model tended to be larger than the entrances resulting from the same shot.Conclusion Thin-layer CT and Dicom standard can improve the efficiency of establishment of a more precise 3D FE model of mandible.The procedure of bullet damage to the mandible can be simulated by the finite element.

Objective:To investigate the value of the lateral arm free flap (LAFF)in the repair of oral and maxillofacial defects af-ter resection of malignant tumor.Methods:22 cases received LAFF from January 2012 to December 2012 were studied.The flap size,preparation time,vessel diameter,anastomosis time,survival situation,success rate and postoperative results were observed. Results:The flap ranged from 14 cm ×8 cm to 6 cm ×4 cm.All flaps survived well without vascular crisis.Repair results were satis-factory.Conclusion:LAFF,with constant anatomy and simple preparation,can be applied in the repair of oral and maxillofacial de-fects after tumor resection.

Objective To measure the dimensional error of three dimensional printing maxilla models for the clinical application to oral and maxillofacial surgery.Methods The FDM 3D printing was employed to make standard geometric shape models and maxillary models.After the surface finish of both models being observed,the contour data and fineness of geometric models,as well as the distance error of bony markers between maxillary models and jaw bones specimen were measured.Results Within the 3D printing standard geometric model,the fiber arrange horizontally in X-Z,Y-Z surface and crosswise in X-Y surface,and the accuracy errors range from-1.67％ to 1.47％.Moreover,the maximum resolution was 0.25 mm in X and Y axis,and 0.50 mm in Z axis.Within the maxillary model,the distance error of bony markers range from-0.08 ％ to 1.96 ％,and the mean errors were 1.59 ％,0.86％,0.42％ in X,Y and Z axis respectively.The mean error in X axis was significantly larger than that in Y or Z axis (P＜0.05).Conclusion 3D printing maxilla models may possess high accuracy and apply to clinical practice.