单侧部分后牙反下颌牙根尖应力分布的光弹实验研究

目的 :探讨单侧部分后牙反牙合对下颌牙根尖应力的影响特点。方法 :采用透明环氧树脂复制以相同牙排列而成的单侧部分后牙反牙合及正常牙合下颌模型各 1副 ,2 .0kg垂直加载 ,投影式光弹仪上观测各牙根尖主应力的大小与方向 ,并分析其与下颌牙根轴倾角之关系。结果 :在近远中方向上 ,反牙合双侧下颌牙根轴倾角及根尖主应力均比正常牙合更偏远中。但在颊舌方向上 ,反牙合侧根轴倾角比正常牙合更偏舌侧 ,而反牙合对侧根轴与正常牙合相比 ,无显著变化 ,但双侧的根尖主应力都比正常牙合更偏颊侧。而且单侧部分后牙反牙合的双侧牙根尖应力大小与正常牙合相比并无显著差异 ,但其根尖应力在各牙位上的分布特征与正常牙合明显不同。结论 :源于牙尖斜面引导方式改变的咬合类型的变化对下颌牙根尖主应力大小及方向具有重要影响

Photoelastic analysis of apical stress distribution in normal and cross-bite occlusion of partial posterior teeth

AIM: To investigate the effect of cross-bite occlusion to the apical occlusal stress distribution. METHODS: Epoxy resin models of normal and partial posterior teeth cross-bite 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 measured. The long axes inclination of the mandibular teeth were also considered. RESULTS: Mesial-distally, long axes inclination, as well as its directions of main apical stress, of cross-bite occlusion all directed more distally than those of the normal. While those were different buccal-lingually. Long axes of the teeth on the side with cross-bite relation directed more buccally than the normal and those of opposite side showed no difference with the normal occlusion. But the directions of main apical stress of both sides all directed more buccally to the mormal. Though the main apical stress values of both sides of cross-bite occlusion had no difference to those of the normal, the feature of distribution changed obviously. CONCLUSION: Alterations of occlusal pattern caused by changes of guiding direction of cuspal working plane may influence the directions and values of main apical stress of mandibular teeth.