Discipline of Biomaterials, Faculty of Dentistry, The University of Sydney, Sydney, NSW 2010, Australia.
Acta Biomater. 2012 Dec;8(12):4426-37. doi: 10.1016/j.actbio.2012.08.006. Epub 2012 Aug 16.
The objectives of this study were to identify the effect of design parameters, namely marginal thickness, degree of convergence and the different interfacial conditions, on the initial failure load that induces cracking from the margin in glass-simulated dental crowns. Crown-like glass cylinders were prepared to simulate posterior all-ceramic crowns with two different marginal thicknesses (0.8 or 1.2mm) and degrees of convergence (6° or 12°). A three-step bonding system was used complementarily with a silane coupling agent to adhesively bond the specimens to resin dies. The crowns were subjected to an axial applied load to generate hoop tensile stress at the crown margin. The entire loading and fracture processes were recorded by video camera. The loading data were compared with the other two interfacial treatments (Vaseline grease and directly poured uncured resin on glass). The Weibull distribution was used to statistically analyze the characteristic failure load and the mean values. The fracture surfaces were fractographically analyzed along with the load-displacement curves, and the degrees of crack stability for each parameter were also identified. It was found that there is no difference in the initial failure load between the different marginal thicknesses in all interfacial conditions. The bonded crowns present more resistance to crack propagation. The higher convergence crown preparation can reduce the initial failure load at the crowns' margin, which can be resisted by a strongly bonded interface. Clear interactions between margin design parameters and their effects on the stress development and crack propagation are necessary to develop an appropriate design of all-ceramic crowns.
本研究旨在确定设计参数（即边缘厚度、收敛度和不同界面条件）对玻璃模拟牙冠从边缘开始产生裂纹的初始失效载荷的影响。制备了类似于牙冠的玻璃圆柱体，以模拟具有两种不同边缘厚度（0.8 或 1.2mm）和收敛度（6°或 12°）的后牙全瓷冠。使用三步粘接系统，并用硅烷偶联剂辅助，将试样粘接到树脂模具上。牙冠承受轴向施加的载荷，在牙冠边缘产生环向拉伸应力。通过摄像机记录整个加载和断裂过程。将加载数据与其他两种界面处理（凡士林油脂和直接浇注未固化树脂在玻璃上）进行比较。使用威布尔分布对特征失效载荷和平均值进行统计分析。对断裂表面进行断裂分析，并结合载荷-位移曲线，确定每个参数的裂纹稳定性程度。结果表明，在所有界面条件下，不同边缘厚度的初始失效载荷没有差异。粘接到牙冠上可以提高其抵抗裂纹扩展的能力。较高的收敛牙冠制备可以降低牙冠边缘的初始失效载荷，而具有强结合界面的牙冠可以抵抗这种载荷。为了开发合适的全瓷冠设计，有必要对边缘设计参数及其对应力发展和裂纹扩展的影响进行明确的交互作用研究。
