Department of Prosthodontics, School of Dentistry, Islamic Azad University of Medical Sciences, 10 Neyestane, Pasdaran, Tehran, Iran.
J Prosthodont Res. 2011 Apr;55(2):121-5. doi: 10.1016/j.jpor.2010.04.006. Epub 2010 Oct 23.
One of the major problems of all ceramic restorations is their probable fracture against the occlusal force. The aim of the present in vitro study is to compare the effect of two marginal designs (shoulder and chamfer) on the fracture resistance of all ceramic restorations, INCERAM.
On an extracted first maxillary premolar 50 in. chamfer margin (0.7 mm) was prepared. Ten impressions were taken using a polyvinylsiloxane. The impressions were poured with epoxy resin to fabricate dies. The same tooth was retrieved and 50 in. chamfer was converted into 90 in. shoulder (1 mm). Ten impressions were taken and ten more epoxy resin dies were fabricated. Impressions of each epoxy resin die were taken using polyvinylsiloxane impression material and poured with die stone. Alumina cores with 0.5 mm thickness fabricated on the stone dies in a dental laboratory. The alumina cores were then cemented on the epoxy resin dies and underwent a fracture test with a universal testing machine and samples were investigated from the point of view of the origin of the failure.
The mean value of fracture resistance for the chamfer samples were 610.18 ± 58.79 N and 502.72 ± 105.83 N for the shoulder samples. The Student's t-test revealed a statistically significant difference between groups.
The result of this study indicates a relationship between the marginal design of the alumina cores and their fracture resistance. A chamfer margin could improve the biomechanical performance of posterior single crown alumina restorations. This may be because of the strong unity in the chamfer margin.
全瓷修复体的主要问题之一是它们可能在咬合力的作用下发生断裂。本体外研究的目的是比较两种边缘设计（肩台和倒角）对全瓷修复体 INCERAM 抗折裂性能的影响。
在上颌第一前磨牙上制备 50 度 chamfer 边缘（0.7mm）。用聚硅氧烷制取 10 个印模。用环氧树脂浇铸印模以制作模具。取出同一颗牙齿，将 50 度 chamfer 转换为 90 度 shoulder（1mm）。制取 10 个印模并制作另外 10 个环氧树脂模具。用聚硅氧烷印模材料制取每个环氧树脂模具的印模，并浇注石。在牙科实验室，用石模具制作厚度为 0.5mm 的氧化铝核。然后将氧化铝核粘接到环氧树脂模具上，并在万能试验机上进行断裂试验，从失效的起源角度对样本进行研究。
chamfer 样本的平均抗折裂力为 610.18 ± 58.79N，shoulder 样本为 502.72 ± 105.83N。学生 t 检验显示组间存在统计学差异。
本研究结果表明氧化铝核的边缘设计与其抗折裂性能之间存在关系。chamfer 边缘可以改善后牙单冠氧化铝修复体的生物力学性能。这可能是因为 chamfer 边缘具有较强的整体性。
