饰瓷/核瓷厚度比对IPS e.max全瓷冠强度影响的非线性接触有限元分析

Non-linear Contact Finite Element Analysis of Veneer/core Thickness Ratio on the Strength of IPS E.max

目的:基于非线性接触有限元数值计算方法探讨不同饰瓷与核瓷厚度比对IPS e.max全瓷冠强度的影响。方法:建立5组轴对称下颌第一磨牙形态试件的有限元模型,饰瓷与核瓷厚度比分别为1∶4、1∶2、1∶1、2∶1、4∶1。采用半径为4.5mm的半球形加载头对各组模型进行加载,得到各组模型在不同载荷下的应力分布状态及变化规律,并通过最优化理论进行分析。结果:饰瓷的最大主应力峰值出现在饰瓷咬合面与加载头接触的外侧周围;核瓷的最大主应力峰值出现在加载头接触区下方的核瓷与粘接剂之间;饰瓷和核瓷所受的最大主应力均随载荷的增大而增加。基于最优化理论饰瓷与核瓷厚度比为1∶4时断裂强度最大。结论:基于本实验有限元模型分析,临床上在满足美观要求的情况下,应尽量减小饰核瓷厚度比,以期增加全瓷冠整体断裂强度,提高使用寿命。

Objective：To investigate the effect of different veneer /core thickness ratio on the strength of IPS e.max with non-linear contact finite element method.Methods：Axisymmetric finite element models with different veneer /core thickness ratio of all-ceramic crown of mandibular first molar（1：4、1：2、1：1、2：1、4：1,respectively）was established.A 4.5-mm diameter ball was applied to load on the all-ceramic crowns.The stress distribution and its regularity in the model were calculated with different loads,the optimal thickness ratio was selected by the optimization theory.Results：The maximum principal stress of core ceramic concentrated in the interface of cement and core under the load area.The maximum principal stress of veneer existed on the surface of the crown,particularly around the places the ball contacted.As the load increased,the maximum principal stress of porcelain and core ceramic did.The biggest fracture strength of the five different veneer /core thickness ratio was 1：4 according to the optimization theory.Conclusion：Based on the study of finite element model veneer /core thickness ratio should be minimized,while the aesthetic requirement could be met,in order to increase the fracture strength of all-ceramic crown and improve lifetime.