下颌第二磨牙咬合接触变化对颞下颌关节应力分布的影响

目的 用力学研究方法结合有限元技术分析下颌第二磨牙咬合接触部位改变时，相同压强咬合载荷条件下颞下颌关节应力的变化。方法 在包括左侧下颌第二磨牙在内的颞下颌关节三维有限元模型上，设计下颌第二磨牙牙尖交错He(ICO)、远中和颊侧3种加载部位的工况，通过有限元运算探讨双侧髁突应力分布的变化规律。结果 由于咬合加载部位的牙面承载形态不同，在双侧髁突上产生了不同的应力效应，其变化包括应力性质和应力分布特点等方面，远中加载和颊侧加载时对侧髁突的Von Mises应力最大值由ICO加载时的51．51MPa分别增加到72．15MPa和69．57MPa。结论 与单侧下颌第二磨牙承载部位变化相关的咬合力方向变化，可使同一力值的咬合力产生不同的双侧髁突应力效应。

Effect of change in occlusal contact areas of the mandibular second molar on temporomandibular joint stress distribution:a 3-dimensional finite element analysis

Objective To investigate the regulation of stress distribution on TMJ when the location of occlusal load on the mandibular second molar was changed by using the 3-dimensional Finite Element Method (FEM). Methods A 3-dimensional FEM TMJ model including left mandibular second molar and mandible was established. In finite element analysis software ANSYS the same boundary constraints were applied to the TMJ FEM model with different load cases. The occlusal loads were applied to simulate ICO load, distal load, and buccal load and the stress values of condyles of the FEM model were calculated. Results As the occlusal load was applied to different tooth contact areas with various shapes, the stress distributions of bilateral condyles were found different and asymmetrical. The condyle stress on TMJ FEM model in three loading cases was diversed, not only in stress character but also in stress distribution style. The maximum value of Von Mises in the opposite condyle was 51.513 MPa when ICO load was applied. But when the distal load or the buccal load was applied, the maximum value of Von Mises in the opposite condyle increased to 72.145 MPa or 69.566 Mpa respectively. Conclusions The same level but in different direction of occlusal load that resulted from difference of loading spots by changing the occlusal contact area, would induce different stress features on bilateral condyles.