桩核材料对第一前磨牙铸瓷冠应力分布的影响

Effects of Post-Core Materials on Stress Distribution in Casting Ceramic Crown of the First Premolar

目的:研究不同种类和强度桩核材料与铸瓷冠破折碎裂的内在关系。方法:在第一前磨牙轴对称纵剖面上设计二维有限元模型,模拟陶瓷层、牙本质领、桩核等结构,绕其对称轴旋转成三维有限元模型。分析在天然牙本质、金合金、Ni-Cr合金外涂0.5 mm色瓷、铸瓷、玻璃纤维树脂、普通复合树脂6种桩核材料情况下,铸造玻璃陶瓷全冠的瓷层内及残余牙本质领的应力分布情况。结果:在6种桩核材料中,高弹性模量的金合金能够降低瓷层及残余牙本质领的最大主应力和Von Mises应力峰值,防止瓷层破折碎裂;而弹性模量最低的普通复合树脂则正好相反。其他材料界于两者之间。即铸瓷冠瓷层及残余牙本质领的应力峰值随桩核材料弹性模量的减小而增大。结论:对于行根管治疗术后的无髓牙,进行核桩冠修复时,应采用高弹性模量的桩核材料;如果使用复合树脂核,也应采用高弹性模量的复合树脂。

Objective： To investigate the relationship between different kinds and strengths of post-core materials and the fragmentation of porcelain which may be helpful to improve the design of the post-core crown and full crown.Methods： Axisymmetric finite element models of the first premolar which consisted of casting porcelain crown,post-core and dentin,which were similar to the clinical structure,were constructed by means of Auto CAD 2000 on a personal computer.Their three finite element models were achieved by their revolving arounding their axis of symmetry.Based on these models,stress distribution on the crown and residual dentin collar under six kinds of post-core materials was examined which were casting gold alloy,Ni-Cr alloy core with 0.5 mm opaque ceramic,casting ceramic core,glass fiber reinforced composite,natural dentin, and common composite resin.Results： Casting gold alloy with high elastic modules decreased the peak principal stress and Von Mises stress on porcelain and dentin collar,therefore prevented the fragmentation of porcelain. But the situation of common composite resin with the smallest elastic modules was opposite to the former.The situation of other materials were between them.This means that the peak stresses on casting porcelain crown and residual dentin collar increase when the elastic module of post-core materials decreases.Conclusion： For post-core crown,the core materials with high elastic modules are commendated,and if composite resin post core is adopted,it should also have higher elastic modules.