Tip-Edge力系后倾曲对上颌磨牙初始位移影响的三维有限元分析

Analysis of tip back bend on initial displacement of the maxillary first molar in Tip-Edge force system by three-dimensional finite element method

目的研究Tip-Edge力系中上颌第一磨牙在后倾曲作用下的初始位移情况,探讨后倾曲曲度和位置对上颌第一磨牙初始位移的影响。方法采用牙列完整的干颅,用CT扫描建立Tip-Edge差动直丝弓三维有限元模型,模拟5种后倾曲曲度(20°、30°、40°、50°、60°)以及4种后倾曲位置(2、4、6、8 mm)对模型进行加载,计算上述情况下磨牙的初始位移情况。结果在后倾曲作用下,上颌第一磨牙出现远中方向移动以及伸长移动。当后倾曲曲度增加时,磨牙的远中初始位移以及伸长位移增加;当后倾曲距离增加时,磨牙的远中初始位移以及伸长位移减少。结论通过改变后倾曲的曲度和位置,可以有效地控制Tip-Edge力系下上颌磨牙的初始位移方式以及移动量。

Objective The aim of this study was to analyze the initial displacement of the maxillary first molar by tip back bend in Tip-Edge force system and to explore the relationships between the displacement and the degree or position of tip back bend.Methods The Tip-Edge three-dimensional finite element model was constructed by CT scan of a dry skull with all teeth.The conditions of five types of degree（20°,30°,40°,50°,60°） and four types of position（2,4,6,8 mm） of tip back bend were added to the three-dimensional finite element model and the initial displacements of the maxillary first molar were calculated.Results Under the effect of tip back bend,distal and ex-trusive displacement of the maxillary first molar occurred.The distal and extrusive movement increased as the degree of tip back bend increased or the position of tip back bend moved distally.Conclusion The initial displacement of the maxillary first molar could be controlled by the precise control of the degree and position of tip back bend.