Rosa Vinicius, Yoshimura Humberto N, Pinto Marcelo M, Fredericci Catia, Cesar Paulo F
Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, São Paulo, Brazil.
Dent Mater. 2009 Jun;25(6):736-43. doi: 10.1016/j.dental.2008.12.009. Epub 2009 Feb 23.
To determine the effect of ion exchange on slow crack growth (SCG) parameters (n, stress corrosion susceptibility coefficient, and sigma(f0), scaling parameter) and Weibull parameters (m, Weibull modulus, and sigma(0), characteristic strength) of a dental porcelain.
160 porcelain discs were fabricated according to manufacturer's instructions, polished through 1 microm and divided into two groups: GC (control) and GI (submitted to an ion exchange procedure using a KNO3 paste at 470 degrees C for 15 min). SCG parameters were determined by biaxial flexural strength test in artificial saliva at 37 degrees C using five constant stress rates (n=10). 20 specimens of each group were tested at 1 MPa/s to determine Weibull parameters. The SPT diagram was constructed using the least-squares fit of the strength data versus probability of failure.
Mean values of m and sigma(0) (95% confidence interval), n and sigma(f0) (standard deviation) were, respectively: 13.8 (10.1-18.8) and 60.4 (58.5-62.2), 24.1 (2.5) and 58.1 (0.01) for GC and 7.4 (5.3-10.0) and 136.8 (129.1-144.7), 36.7 (7.3) and 127.9 (0.01) for GI. Fracture stresses (MPa) calculated using the SPT diagram for lifetimes of 1 day, 1 year and 10 years (at a 5% failure probability) were, respectively, 31.8, 24.9 and 22.7 for GC and 71.2, 60.6 and 56.9 for GI.
For the porcelain tested, the ion exchange process improved strength and resistance to SCG, however, the material's reliability decreased. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was also higher for the ion treated group.
确定离子交换对牙科陶瓷的慢裂纹扩展（SCG）参数（n、应力腐蚀敏感性系数和σ(f0)，比例参数）以及韦布尔参数（m，韦布尔模量，和σ(0)，特征强度）的影响。
按照制造商的说明制作160个瓷盘，研磨至1微米，并分为两组：GC（对照组）和GI（在470℃下使用KNO3糊剂进行离子交换处理15分钟）。通过在37℃的人工唾液中以五种恒定应力速率（n = 10）进行双轴弯曲强度试验来确定SCG参数。每组20个试样在1MPa/s下进行测试以确定韦布尔参数。使用强度数据与失效概率的最小二乘拟合构建SPT图。
m和σ(0)（95%置信区间）、n和σ(f0)（标准差）的平均值分别为：GC组为13.8（10.1 - 18.8）和60.4（58.5 - 62.2）、24.1（2.5）和58.1（0.01），GI组为7.4（5.3 - 10.0）和136.8（129.1 - 144.7）、36.7（7.3）和127.9（0.01）。使用SPT图计算的1天、1年和10年寿命（失效概率为5%）的断裂应力（MPa），GC组分别为31.8、24.9和22.7，GI组分别为71.2、60.6和56.9。
对于所测试的陶瓷，离子交换过程提高了强度和抗SCG能力，然而，材料的可靠性降低。离子处理组在10年寿命、5%失效概率下的预测断裂应力也更高。
