三种基牙材料对铸造玻璃瓷冠碎裂影响的研究

Study on effect of three abutment materials on the fraction of casting porcelain crown

目的 :研究不同种类和强度基牙材料与瓷冠破折碎裂的内在关系。方法 :选用计算机建立上颌中切牙的三维有限元模型 ,模拟陶瓷层、牙本质、核桩等结构。分析在天然齿基牙、钴铬合金基牙及复合树脂基牙情况下 ,铸造玻璃陶瓷全冠的瓷层内及残余牙本质的应力分布情况。结果 :高弹性模量的钴铬合金能够降低瓷层及残余牙本质内的最大主应力和最小主应力峰值 ,防止瓷层破折碎裂 ;而弹性模量与牙本质相近的复合树脂桩降低应力峰值的作用不明显。结论 :对于有牙髓活力的牙本质基牙 ,尽量保存牙髓活力后行全冠修复。对于行根管治疗术后的无髓牙 ,进行核桩冠修复时 ,采用高弹性模量的高熔合金 。

Objective:To investigate the relationship between different kinds and strengths of abutment and the fragmentation of porcelain which may assist to improve the design of the post core crown and full crown. Methods:A three dimensional finite element model of maxillary incisor which consisted of casting porcelain crown, post core, similar to the clinical structure, was constructed by means of Super SAP on a personal computer. The tensile stress distributions on the crown and residual dentin under three kinds of abutment which were a natural tooth, a Co Cr cast core and a composite resin core were analyzed. Results: Co Cr metal post core with high elastic modules decreased the maximum principle stress and minimum principle stress on porcelain, therefore prevented the fragmentation of porcelain. Meanwhile:This design changed the pattern of stress distribution, with high stress concentrating on the border between post and dentin. The stress distribution pattern of the composite resin post core with low elastic modules was similar to that of natural tooth abutment, but had little influence in lessening the principle stress. Conclusion:For natural tooth abutment with active pulp, we should make full crown and preserve the activity of pulp. For post core crown, we should use metal post core with high elastic modules to avoid using resin post core with low elastic modules.