Ausiello P, Apicella A, Davidson C L, Rengo S
School of Dentistry, University of Naples, Federico II, Policlinico Edificio 14, Via Pansini 5, 80131 Naples, Italy.
J Biomech. 2001 Oct;34(10):1269-77. doi: 10.1016/s0021-9290(01)00098-7.
The combination of diverse materials and complex geometry makes stress distribution analysis in teeth very complicated. Simulation in a computerized model might enable a study of the simultaneous interaction of the many variables. A 3D solid model of a human maxillary premolar was prepared and exported into a 3D-finite element model (FEM). Additionally, a generic class II MOD cavity preparation and restoration was simulated in the FEM model by a proper choice of the mesh volumes. A validation procedure of the FEM model was executed based on a comparison of theoretical calculations and experimental data. Different rigidities were assigned to the adhesive system and restorative materials. Two different stress conditions were simulated: (a) stresses arising from the polymerization shrinkage and (b) stresses resulting from shrinkage stress in combination with vertical occlusal loading. Three different cases were analyzed: a sound tooth, a tooth with a class II MOD cavity, adhesively restored with a high (25 GPa) and one with a low (12.5GPa) elastic modulus composite. The cusp movements induced by polymerization stress and (over)-functional occlusal loading were evaluated. While cusp displacement was higher for the more rigid composites due to the pre-stressing from polymerization shrinkage, cusp movements turned out to be lower for the more flexible composites in case the restored tooth which was stressed by the occlusal loading. This preliminary study by 3D FEA on adhesively restored teeth with a class II MOD cavity indicated that Young's modulus values of the restorative materials play an essential role in the success of the restoration. Premature failure due to stresses arising from polymerization shrinkage and occlusal loading can be prevented by proper selection and combination of materials.
多种材料与复杂几何形状的结合使得牙齿中的应力分布分析非常复杂。在计算机模型中进行模拟可能有助于研究众多变量的同时相互作用。制备了人类上颌前磨牙的三维实体模型，并将其导出为三维有限元模型（FEM）。此外，通过适当选择网格体积，在有限元模型中模拟了II类MOD窝洞制备和修复的一般情况。基于理论计算和实验数据的比较，执行了有限元模型的验证程序。为粘结系统和修复材料赋予了不同的刚度。模拟了两种不同的应力情况：（a）由聚合收缩产生的应力和（b）由收缩应力与垂直咬合负荷共同产生的应力。分析了三种不同的情况：一颗完好的牙齿、一颗有II类MOD窝洞的牙齿，分别用高弹性模量（25 GPa）和低弹性模量（12.5 GPa）的复合材料进行粘结修复。评估了聚合应力和（过度）功能性咬合负荷引起的牙尖运动。由于聚合收缩产生的预应力，刚性较高的复合材料的牙尖位移更大，而在咬合负荷作用下的修复牙齿中，柔性较高的复合材料的牙尖运动较小。这项关于用II类MOD窝洞粘结修复牙齿的三维有限元分析的初步研究表明，修复材料的杨氏模量值在修复成功中起着至关重要的作用。通过适当选择和组合材料，可以防止因聚合收缩和咬合负荷产生的应力导致的过早失败。
