复合转矩弓丝在内收前牙时牙周组织应力分布三维有限元分析

目的比较平直的0.46mm×0.64mm的不锈钢方丝和复合转矩弓丝(retraction and torque arch)内收前牙,关闭拔牙间隙时上颌4个切牙的位移趋势和牙周组织应力分布。方法运用三维有限元分析,在已建立的模型上进行加载,加载点为托槽中心牙冠表面,复合转矩弓丝对4个切牙施加14N.mm、方向为牙冠唇向、牙根舌向的力矩,计算得到牙周膜应力分布情况。结果在前牙内收时,无论是使用不锈钢方丝还是复合转矩弓丝,牙颈部应力值均最大,其次最大值出现在根尖部。上颌4个切牙有远中移动和舌向移动的趋势,而在使用复合转矩弓丝的情况下,牙周膜最大主应力均比应用平直不锈钢方丝显著减小。结论在前牙内收阶段使用复合转矩弓丝,能显著保持4个前牙的正常唇倾度,前牙接近整体移动,更符合生理移动的要求。

3D dimensional definite analysis of stress distribution in periodontal tissue using compound retraction arch in retraction of anterior teeth

Objective To compare the differences of creep tendency and stress distribution in periodontal tissue by the use of traditional stainless steel rectangular arch and the retraction and torque arch in retraction of the 4 upper incisors. Methods A model was established by 3D finite element analysis,on which two kinds of arch were loaded. An additional 14 N＊mm moment was added to the model with the retraction and torque arch. Then the stress distribution in periodontal tissue was calculated.Results The maximum stress appeared in dental cervix and root tip in both models. The four incisors had a creep tendency to the distal and lingua tips. However,the maximum stress of the compound retraction arch model was less than that of the traditional stainless steel arch. Conclusion Ideal bodily movement could be achieved when compound retraction arch was used.