埋伏牙牙周应力分布的三维有限元分析

目的通过建立埋伏牙的三维有限元模型，分析不同加载力下埋伏牙的牙周应力，从而为临床上正畸牵引治疗埋伏牙提供基础实验依据。方法选取实验模型，进行双螺旋CT扫描，应用Ansys软件建立埋伏牙的三维有限元模型，在建立的埋伏牙三维有限元模型上添加牙周膜模型。对建立的三维有限元模型进行3种工况下的力学加载，分别计算其牙周应力的分布情况。结果加载1即加载力方向与牙体长轴一致时，埋伏牙牙周应力区间较小，最大应力值较小，应力分布比较平均。加载3即加载力方向与牙体长轴垂直时，埋伏牙牙周应力区间较大，最大应力值较大，但应力分布集中于加载指向的一侧。加载2即加载力方向与牙体长轴成45°角时，埋伏牙牙周应力区间和最大应力值中等，牙周应力分布居于二者之间。结论牵引力的方向与牙体长轴一致时，埋伏牙的最大牙周应力较小，分布比较平均，有利于埋伏牙的牵引萌出。牵引力方向与牙体长轴成一定角度时，随着角度的增大，最大牙周应力变大，分布更加集中，不利于埋伏牙的牵引萌出。临床上应根据实际情况选择牵引力的方向，以使埋伏牙最终达到其正常位置。如牵引力方向与牙体长轴成角较大时，应适当增加支抗来抵抗较大的牵引力。

3-dimensional finite element analysis of periodontal stress distribution when impacted teeth are tracted

Objective To analyze stress around the impacted tooth by constituting a 3-dimensional finite element model of impacted tooth, consequently offer reference basis for clinic traction treatment. Methods The 3-dimensional finite element model of the impacted tooth was constituted by CT scan, append pericementum and alveolar bone model was used to constitute impacted model. 3 forces were loaded to 3-dimensional finite element model and the periodontal stress of impacted tooth was calculated. Results When force 1 was loaded to the model, the maximum stress was smaller, but the stress distribution was more average. When force 3 was loaded to the model, the maximum stress was larger, but the stress concentrated at the side of the force. When force 2 was loaded to the model, the stress distribution was medium. Conclusion When the direction of the force is in line with the central axis, the maximum stress is smaller, and the stress distribution is more average, while this has advantage to the eruption of the impacted tooth. When the direction of the force has angle with the central axis of the impacted tooth, the angle is larger, the maximum stress is larger and the stress distribution is more concentrate, and this goes against the eruption of the impacted tooth. The angle between the orientation of the traction and central axis of the impacted tooth is smaller, there are more advantages to the eruption of the impacted tooth. So the angle should be properly selected in order to make sure of the eruption of the impacted tooth. When the angle is quite large, more anchorage is needed to resist to the large force.