摇椅弓滑动法整体内收上颌前牙的三维有限元分析

A three dimensional finite element analysis on en-masse retraction of maxillary anterior teeth by rocking-chair archwire in sliding mechanics

目的探讨摇椅弓应用于滑动法内收上颌前牙的力学效应。方法应用ANSYS软件建立上牙列三维有限元模型,分别计算不同深度摇椅弓和不同高度牵引钩内收上前牙时对6个上前牙阻抗中心产生的转矩,并观察二者联合应用时上前牙初始移动情况。结果选择不同深度的摇椅弓可产生不同的冠唇向转矩,用以抵消摩擦力及不同高度牵引钩滑动法内收产生的冠舌向转矩,进而实现上前牙的整体移动。在上颌第二前磨牙和第一磨牙之间应用种植体支抗时,2 mm深度的摇椅弓可配合使用7.2 mm高度的牵引钩来实现上前牙的压低及整体内收。结论摇椅弓可以有效改善内收前牙时出现的直立和舌倾状态,实现压低和转矩的双重控制。

Objective To investigate the effect of en-masse retraction of maxillary anterior teeth by rocking-chair arehwire （RCA） in sliding mechanics. Methods The three dimensional finite element model of maxillary teeth was created based on spiral CT data of a patient by ANSYS software. The forces on each tooth and the torques on the six center of resistance （CPO of the anterior teeth induced by the deformation of RCA with different depth and anterior retraction hook （ARH） with different height were calculated when retracted from a mini-implant between the first molar and the second premolar. The movements of anterior teeth were observed combining different depth of RCA with dif- ferent height of ARH. Results The clockwise torque in sliding mechanics to realize en-masse retraction of the anterior teeth could be counterbalanced by RCA of certain depth. The combination of 7.2 mm ARH and 2 mm RCA can be used to intrude and retract maxillary anterior teeth under the condition of applying mini-implant. Conclusion The excessive retraction that usually exists in traditional treatments can be avoided by RCA in sliding mechanics and intru- sion and torque control during anterior segment retraction can also be achieved by this method.