Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT, USA.
Graduate Program in Dental Sciences, Federal University of Santa Maria, Santa Maria, RS, Brazil.
Comput Methods Biomech Biomed Engin. 2022 Mar;25(4):412-423. doi: 10.1080/10255842.2021.1955869. Epub 2021 Jul 22.
Metal-ceramics (MC) are one of the oldest dental restorative systems, which are considered to be the gold standard for full crown restoration. Porcelain-veneered lithium disilicate (PVLD), on the other hand, are newer material systems that have shown high survival rate in clinical follow-ups but needs to be studied more. This study compares the stresses developed in the single crowns made from newer PVLD system against those with MC configuration. For this comparison, influence of the layer thickness and cooling rates is also taken into consideration. An experimentally validated viscoelastic finite element model (VFEM) has been developed to predict the stress profile in these systems. Three-dimensional rotationally symmetric crowns were analyzed using this validated model for both material systems, three veneer to core thickness ratios (2:1, 1:1, 1:2), and two cooling rates: slow cooling at 1.74E-5 W/mm (∼30 K/min) and fast cooling at 1.74E-4 W/mm (∼300 K/min). PVLD showed lower values of transient and residual stresses than MC. The maximum tensile residual stresses in MC systems were observed in the cusp area, whereas those in PVLD were located in the central fossa. With the reduction in veneer layer, there was reduction in residual stress in MC; however, the veneer thickness had little to no effect in PVLD. The effect of cooling rate was also evident as slow cooling resulted in lower residual and tensile stresses for both material systems.
金属陶瓷（MC）是最古老的牙科修复系统之一，被认为是全冠修复的金标准。另一方面，瓷贴面锂硅（PVLD）是更新的材料系统，在临床随访中表现出高存活率，但需要进一步研究。本研究比较了由更新的 PVLD 系统制成的单冠和 MC 配置所产生的应力。为了进行这种比较，还考虑了层厚度和冷却速率的影响。已经开发了一种经过实验验证的粘弹性有限元模型（VFEM），用于预测这些系统中的应力分布。使用经过验证的模型对两种材料系统的三维轴对称冠进行了分析，包括三种贴面到核厚度比（2:1、1:1、1:2）和两种冷却速率：以 1.74E-5 W/mm（约 30 K/min）的慢冷却速度和以 1.74E-4 W/mm（约 300 K/min）的快速冷却速度。PVLD 显示出比 MC 更低的瞬态和残余应力值。在 MC 系统中，最大的拉伸残余应力出现在尖顶区域，而在 PVLD 中则位于中央窝。随着贴面层厚度的减少，MC 中的残余应力减少；然而，在 PVLD 中，贴面厚度几乎没有影响。冷却速率的影响也很明显，因为慢速冷却会导致两种材料系统的残余和拉伸应力降低。
