牙位对不同咬合类型的下颌牙根尖应力影响的光弹实验研究

目的：探讨牙位的变化对下颌各牙根尖主应力大小及方向的影响进行分析。方法：采用透明环氧树脂复制以相同牙排列而成的正常He、深覆He、重度磨耗He、单侧部分后牙反He、单侧上颌第三磨牙伸长、单侧下颌第三磨牙伸长、单侧部分后牙缺失7种不同咬合类型的下颌模型，2．0kg力垂直加载后，投影式光弹仪上观测各牙根尖主应力的大小与方向。结果：在对称性咬合，牙位的变化对各牙的根尖主应力方向无影响。而在不对称性咬合，牙位的变化对前牙区近远中向应力及全牙列的根尖主应力颊舌向倾角都有明显影响。另外，随牙位的变化根尖主应力的大小也会发生显著变化，而且这种差异主要来自于不对称性咬合类型。结论：牙在下颌骨上相对位置的变化会对其根尖主应力大小及方向产生一定的影响，而且其影响程度还会受到咬合对称性等因素的影响。

Photoelastic Analysis of the Effects of Teeth Position to Apical Stress Distribution in Different Occlusal Patterns

Objective:To investigate the effect of teeth position variation to the apical occlusal stress distribution in three different occlusal patterns.Methods:Epoxy resin models of seven occlusal types including normal occlusion,deep overbite,severe attrition occlusion,partial posterior teeth cross-bite occlusion,unilaterally elongated mandibulsr or maxillary third molar and partial posterior teeth loss occlusion set up by identical plastic teeth were employed to determine the stress distribution in apical area under 2.0kg vertical load.The values and directions of main stress were both measured.Results:The variation of tooth position gave no effects to the directions of principle stress around apex area in symmetrical occlusal type.As to asymmetrical occlusal type, mesio-distal directions of anterior teeth and lingual-buccal directions of all the mandibular teeth could be affected by the variation of the tooth position.The magnitude of apical main stress also altered evidently with the change of tooth position and the difference mainly came from asymmetrical occlusion.Conclusions:The variation of tooth position could affect the magnitude and direction of the main apical stress,in which the symmetry of the occlusion type was also involved.