牙科陶瓷材料弯曲强度可靠性和亚临界裂纹扩展研究

Reliability of flexural strength and subcritical crack growth of dental ceramics

目的:研究口腔临床修复中常用的玻璃渗透氧化铝陶瓷(in-ceram alumina,IA)弯曲强度可靠性和循环载荷下亚临界裂纹扩展(SCG)情况。方法:采用Weibull法分析由三点弯曲强度测量方法获得15个IA样本的弯曲强度数据和由循环疲劳测试获得的15个IA样本循环疲劳断裂次数数据;通过帕里斯定律(Paris law)分析IA试件在循环载荷下的亚临界裂纹扩展情况,SCG行为通过裂纹扩展速度和最大应力强度因子(Kimax)的函数关系来描述。结果:通过Weibull法得到IA试件的Weibull模数为7.9,破坏概率为1%、5%、63.21%时弯曲强度分别为246.8、303.4、438.3 MPa。IA在循环载荷下发生亚临界裂纹扩展后导致材料断裂,在应力强度因子KI为临界应力因子KIC的55%时发生裂纹传播。结论:牙科玻璃渗透氧化铝陶瓷循环载荷下存在亚临界裂纹扩展;采用三点弯曲强度测试并结合使用Weibull分析方法能加深对牙科陶瓷弯曲强度可靠性的理解。

Objective： To evaluate the reliability of flexural strength and subcritical crack growth（SCG） under cyclic loading of glassinfiltrated alumina-based（in-ceram alumina, IA）. Methods： Bar-shaped specimens of IA （n = 30） were fabricated and loaded in three-point bending and cyclic fatigued. The flexural strength and the number of cycles to fracture were obtained from three point fie xure test and cyclic fatigue test respectively. Data was examined using Weibull statistics. Paris law was used to analysize the SCG,the behavior of which was described in terms of crack velocity as a function of maximum stress intensity factor （ Klmax ）. Results： The Weibull moduli of IA was 7.9, with the fractural probabilities of 1% , 5% and 63.21% the flexural strength（MPa） of IA was 246.8, 303.4 and 438.3 respectively. IA was prone to SCG ,with crack propagation occurring at KI as low as 55% of its critical stress intensity factor（K/c）. Conclusion：Glass-infiltrated alumina-based dental ceramics cause pronounced SCG. Weibull analysis can be used as a design parameter of brittle ceramic for clinical practice which will introduce a well-understanding of the tested values.