Thompson J Y, Anusavice K J, Naman A, Morris H F
Department of Dental Biomaterials, College of Dentistry, University of Florida, Gainesville 32610-0446.
J Dent Res. 1994 Dec;73(12):1824-32. doi: 10.1177/00220345940730120601.
The goal of this study was to establish a protocol for the retrieval and fractographic analysis of failed restorations, and to compare the fracture surface features of clinically failed ceramic restorations and with those of controlled laboratory test specimens fabricated from the same materials. Ten fractured Dicor crowns and 12 fractured Cerestore crows were retrieved and analyzed. Optical microscopy of the failed crowns revealed that the critical segments of nine of the 10 (90%) Dicor crowns and nine of the 12 (75%) Cerestore crowns were acceptable for fractographic analysis. Twelve disks of each material were fabricated as controls and fractured by bi-axial flexure for analysis of the similarities and/or differences between the fractographic features of fractured clinical crowns and the disks. Each of the 10 Dicor crowns was observed to fail along the internal surface. For 78% of the Cerestore crowns, failure initiation occurred at the porcelain/core interface or inside the core material. Critical flaw sizes of the failed Dicor crowns ranged from 127 to 272 microns. Failure stresses of the Dicor crowns, estimated by fractographic techniques and fracture mechanics relationships, ranged from 65 to 94 MPa. Estimated failure stresses for two of the Cerestore crowns which had failure initiation sites in the porcelain layer were 15 and 68 MPa. It is concluded that the fracture initiation sites of dental ceramics are controlled primarily by the location and size of the critical flaw, and not by specimen thickness.
本研究的目的是建立一个用于取出失败修复体并进行断口分析的方案，并比较临床失败的陶瓷修复体与由相同材料制成的对照实验室测试样本的断口表面特征。取出并分析了10个断裂的Dicor全冠和12个断裂的Cerestore全冠。对失败全冠的光学显微镜检查显示，10个Dicor全冠中的9个（90%）和12个Cerestore全冠中的9个（75%）的关键部分可用于断口分析。每种材料制作12个圆盘作为对照，并通过双轴弯曲使其断裂，以分析断裂临床全冠和圆盘的断口特征之间的异同。观察到10个Dicor全冠中的每一个都沿着内表面失败。对于78%的Cerestore全冠，失败起始发生在瓷/核界面或核材料内部。失败的Dicor全冠的临界裂纹尺寸范围为127至272微米。通过断口分析技术和断裂力学关系估算的Dicor全冠的失败应力范围为65至94兆帕。在瓷层中有失败起始部位的两个Cerestore全冠的估算失败应力分别为15和68兆帕。得出的结论是，牙科陶瓷的断裂起始部位主要由临界裂纹的位置和尺寸控制，而不是由样本厚度控制。
