不同角度后倾曲对下颌第二磨牙作用力的三维有限元分析

目的：探讨0.018〞澳丝弯制的不同角度后倾曲对下颌第二磨牙作用力的情况。方法：应用CT扫描技术、Auto CAD及ANSYS相结合的建模程序,以中国人正常下颌骨为建模的实体参照,建立下颌第二磨牙及其牙周组织的三维有限元模型,同时建立用0.018〞澳丝弯制附5°、10°、15°、20°、25°、30°六个不同角度磨牙后倾曲唇弓的三维有限元模型,利用弯曲梁应变原理,计算出不同角度后倾曲作用下,下颌第二磨牙颊面管近中端及远中端力的大小及方向。结果：第二磨牙近中受到向伸长力,远中受到龈向压低力,其大小随着角度的增大而增大,近中力值大于远中力值。结论：后倾曲对第二磨牙产生远中倾斜力矩;随着后倾曲角度增大,磨牙呈现远中直立的趋势,同时牙冠舌向倾斜趋势加大。

Three-dimensional finite element analysis of the effects of tip-back bends with different angles on mandibular second molar.

Objective：To analyze the effects of tip-back bends with different angles on mandibular second molar.Method：Three-dimensinal finite element models of mandibular second molar and Australian Wire（0.018〞） archwire with 5°,10°,15°,20°,25° and 30°tip-back bends were built by using CT scanning images through AutoCAD software and ANSYS software.The force systems on mandibular second molar were calculated by ANSYS software.Result：Occlusal direction force was formed at the mesial point of mandibular second molar while gingival direction force was formed at the distal point.Both the mesial force and the distal force increased along with the increasing of the angle of tip-back bend while more increment of the mesial force could be obtained.Conclusion：A distal-tipping moment was formed on mandibular second molar by the tip-back bend.Tendencies of distal uprighting and lingual tipping of the molar increased along with the increment of angles of tip-back bends.