咬合接触对颞下颌关节生物力学影响的有限元研究

Influence of teeth contact on stress distribution of TMJ by finite element method

目的建立用于研究咬合接触与颞下颌关节生物力学关系的三维有限元模型,并设计不同的工况来分析不同咬合接触情况下颞下颌关节应力的变化规律。方法尸体头颅1具,平行于眶耳平面作CT扫描;取石膏模型,以三维扫描仪对牙列(牙合)面扫描;将石膏模型扫描参数与CT扫描参数换算到同一坐标系下,在髁突上方设均厚的类关节盘,关节盘顶及下颌角作约束设计,经划分网格生成有限元模型。工况一:左侧下颌不同牙位咬合接触面加载;工况二:在包括左侧下颌第二磨牙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(牙合)、远中方向和颊侧方向三种加载部位的工况,研究不同工况下双侧髁突处应力分布变化的规律。结果(1)建立了包括双侧髁突、类关节盘及下颌牙列在内的用于分析咬合与颞下颌关节关系的三维有限元模型。(2)咬合加载牙位不同,双侧髁突应力效应不同,髁突外、中、前、顶等处为承受较高压强的区域。(3)咬合加载部位牙面承载形态不同,双侧髁突应力效应也不同,其变化包括应力性质和应力的分布特点等方面,远中加载和颊侧加载时分别可致加载侧髁突内极和加载对侧髁突内极应力集中。结论咬合接触部位及方向变化可影响髁突应力分布。

Objective To reconstruct three-dimensional finite element model with occlusion and bilateral condyles to analyze the regularities of TMJ stress distribution resuhing from dental occlusion alteration. Methods A skull was scanned with CT in the direction parallel to the Frankfort Horizontal plane. Occlusion surface of it＇s plaster casts were scanned with a 3D scanner. The parameters of the cast and CT image were converted into the same coordinate system. A simulated disc was added over each of the condyles. Constraints were applied to the upper surfaee of the disc and the angle of mandible. Load 1： Onto the different positions of the teeth in half of the dentition, FEM were applied with upright loads. Load 2： Onto three different occlusal areas of the lower second molar, ICO load,distal load,buccal load were applied. The stresses on condyle under each of the conditions above was analyzed. Results 1. The FEM containing bilateral condyles,simulated discs, and dental occlusion was formed to analyze the association of occlusion and TMJ.2. As ocelusal load was applied to different teeth on dentition from anterior to posterior, the stress distribution of bilateral condyles were found different and asymmetrical. The lateral, middle, anterior and top area of condyle were found loading with high compression. 3, The morphological features of loading area had effect on the stress characteristics and distribution of bilateral condyles. Loading from distal direction would cause stress concentrating over the medial pole of ipsi-lateral condyle while loading from buecal direction would cause stress concentrating over the medial pole of contra-lateral condyle, Conclusion The distribution of stress over condyles was found changed in response to the ahernation of occlusal contact position and direction.