3D statistical failure analysis of monolithic dental ceramic crowns.
3D statistical failure analysis of monolithic dental ceramic crowns.
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DOI：
10.1016/j.jbiomech.2016.05.003
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发表时间：
2016-07-05
影响因子：
2.4
通讯作者：
Rokhlin SI
中科院分区：
文献类型：
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作者：
Nasrin S;Katsube N;Seghi RR;Rokhlin SI
对于各种类型的粘接性瓷冠，临床观察发现，与源自咬合表面的赫兹接触应力相反，最严重的破坏是由骨水泥界面形成的径向裂纹引起的。本文建立了单片陶瓷冠界面初始破坏的三维预测模型。通过有限元应力分析，得到了陶瓷板双轴弯曲试验确定的表面缺陷分布参数以及凹版表面多轴应力状态的点对点变化。在基于断裂力学的统计破坏概率模型的基础上，对单周期压痕载荷作用下整体冠的破坏概率进行了预测。通过已有的二维轴对称模型和实验数据验证了该方法的正确性。在冠与牙基完全结合的情况下，在冠厚度较薄的壁区出现高弯曲应力和高界面剪切应力，而在边缘区出现高界面法向拉应力分布。水泥模量降低对这些应力状态有显著影响。虽然分析仅限于单循环加载-破坏试验，但高界面法向拉应力或高界面剪切应力可能会导致陶瓷与牙本质之间的水泥结合退化。此外，冠破坏概率受小区域内高弯曲应力集中的控制，所提出的方法可能对检测初始冠设计错误有一定的价值。
For adhesively retained ceramic crown of various types, it has been clinically observed that the most catastrophic failures initiate from the cement interface as a result of radial crack formation as opposed to Hertzian contact stresses originating on the occlusal surface. In this work, a 3D failure prognosis model is developed for interface initiated failures of monolithic ceramic crowns. The surface flaw distribution parameters determined by biaxial flexural tests on ceramic plates and point-to-point variations of multi-axial stress state at the intaglio surface are obtained by finite element stress analysis. They are combined on the basis of fracture mechanics based statistical failure probability model to predict failure probability of a monolithic crown subjected to single-cycle indentation load. The proposed method is verified by prior 2D axisymmetric model and experimental data. Under conditions where the crowns are completely bonded to the tooth substrate, both high flexural stress and high interfacial shear stress are shown to occur in the wall region where the crown thickness is relatively thin while high interfacial normal tensile stress distribution is observed at the margin region. Significant impact of reduced cement modulus on these stress states is shown. While the analyses are limited to single-cycle load-to-failure tests, high interfacial normal tensile stress or high interfacial shear stress may contribute to degradation of the cement bond between ceramic and dentin. In addition, the crown failure probability is shown to be controlled by high flexural stress concentrations over a small area, and the proposed method might be of some value to detect initial crown design errors.