动态咬合下牙周膜的生物力学分析

目的 分析动态咬合下加载时间、角度因素对牙周膜应力和位移的影响。方法 采用逆向工程技术建立牙周膜厚度为0.2 mm的下颌前牙—牙周膜—牙槽骨的三维模型，在与牙体长轴分别成0°、15°、30°、45°、60°、75°、90°，由颊侧向舌侧的动态咬合载荷作用下，分析不同周期下牙周膜的应力、位移变化状况。结果 在单周期下，由不同角度载荷引起的牙周膜最大残余应力极大值与最小值之比为5.5,最大位移极值之比为8.1；由5周期引起的最大位移极大值与极小值之比在1.02~1.35内随载荷角度增加；由不同角度载荷引起的最大残余应力极大值与极小值之比在1.86~3.00内随咬合周期数增加；不同角度下最大应力均集中在颈缘舌侧区域, 最大残余应力位置分布随时间在颈缘不同部位间变动；0°载荷下牙根的应力累积最严重。结论 下前牙固定桥基牙选择的临床应用中，应注意牙周膜应力累积情况以及最大残余应力分布的不确定性；临床治疗中，应避免对牙齿施加大角度载荷，尽量减少连续咬合较硬食物。

Biomechanical analysis on periodontal ligament in dynamic jaw

Objective To investigate the influences of loading time and loading angle on the stress, displacement of human periodontal ligament in dynamic jaw. Methods The three-dimensional assembly model of the mandible front teeth, periodontal ligament and alveolar bone was reconstructed by using the reverse engineering technology. The thickness of periodontal membranes was 0.2 mm. The stress, displacement at different positions of the periodontal ligaments during different jaw cycles were analyzed under dynamic load in the direction from bucca to tongue side with 0°, 15°, 30°, 45°, 60°, 75°, 90° angle to the long axis of the tooth. Results During one jaw cycle, the ratio of the maximum to minimum value of the maximum residual stress due to different loading angles was 5.5, and the ratio of the maximum to minimum value of the maximum displacement was 8.1. The ratio of the maximum to minimum value of the maximum displacement which was caused by five jaw cycles was increased in the range from 1.02 to 1.35 with the increase of loading angles. The ratio of the maximum to minimum value of the maximum residual stress which was caused by different loading angles was increased in the range from 1.86 to 3.00 with the increase of jaw cycles. The location of the maximum stress was at the tongue side of the cervical margin at different loading angles, and the location of the maximum residual stress was distributed at different positions of the cervical margin. Most stress was accumulated at the root of the periodontal ligament under the 0° dynamic load. Conclusions The situation of the accumulated residual stresses and the uncertainties in the distribution of the maximum residual stresses should be observed in the clinical choice of mandible incisors fixed by bridge abutments; large angle force applied to the tooth was harmful to the periodontal ligament and rapid succession of chewing hard food should be avoided as much as possible during the clinical treatment.