1.Beijing Institute of Technology;2.Taiyuan University of Technology
目的：用有限元方法分析不同弹性模量、厚度、牙齿移动方式对隐形矫治器形变的影响,为正畸医生制定矫治方案提供理论依据。方法：建立四种厚度、三种弹性模量共12种厚度均匀的隐形牙齿矫治器有限元模型,不同的牙齿移动方式下施加不同的边界条件。(1)对12种模型施加倾斜移动的位移载荷,分析矫治器最大Von mises应力和形变量；(2)对最适模型分别施加倾斜、平行以及压低移动的位移载荷,分析矫治器变形情况。结果：(1)最大Von mises应力随弹性模量、隐形矫治器厚度的增大而增大。形变量随矫治器厚度增大而减小；(2)倾斜和平行移动时,隐形矫治器均在拟移动牙齿对应部位有最大的形变,拟不动牙齿对应部位有的向唇侧外凸变形,有的向舌侧内凹变形；压低移动时,矫治器严重向牙冠顶端偏移。结论：(1)最适厚度为0.75 mm,临床上目前使用的弹性模量816.31 MPa是合适的；(2)在数字模型上将向唇侧外凸部位对应的牙齿的舌侧面和向舌侧内凹对应的牙齿的唇侧面增厚,用增厚后的数字模型制作隐形矫治器,优化矫治器。
Objective: To analyze the effects of different elastic modulus, thickness and tooth movement on the deformation of invisible dental appliance by finite element method (FEM), and to provide theoretical basis for orthodontics to formulate the orthodontic treatment scheme. Methods: Four finite element models of 12 kinds of invisible tooth appliance with four thickness and three elastic modulus were established. (1) the maximum von mises stress and shape variables of the appliance were analyzed by numerical simulation. (2) the deformation of the appliance is analyzed by applying the displacement load of tilt, parallel and low displacement to the optimal model. Results: (1) The maximum Von mises stress increases with the increase of the elastic modulus and the thickness of the invisible appliance. The shape variable decreases with the increase of appliance thickness. (2) When the tooth was tilted and moved parallel, the maximum deformation was found in the corresponding part of the tooth. Some of the corresponding parts of the immovable teeth are deformed to the lip convex side and some to the tongue side internal concave deformation, and the appliance deviates seriously to the top of the crown when the tooth is depressed and moved. Conclusions: (1) The optimum thickness was 0.75 mm, and the current elastic modulus of 816.31 MPA was suitable; (2) In the digital model, the tongue side of the teeth corresponding to the labial protruding part and the lip side of the tooth corresponding to the concave side of the tongue side are thickened, and the invisible appliance is made with the thickened digital model to optimize the appliance.