Clinic for Prosthetic Dentistry and Dental Material Science, University of Saarland, 66424 Homburg Saar, Germany.
Dent Mater. 2011 Jul;27(7):684-91. doi: 10.1016/j.dental.2011.03.010. Epub 2011 Apr 22.
The aim of this study was to evaluate the mechanical properties and the subcritical crack growth behavior of a presintered dental Y-TZP (Kavo Everest ZS) and a hot isostatic pressed Y-TZP (Kavo Everest ZH) and to perform life data analysis.
For each material 150 bending bars were produced. The initial fracture strength was determined in a four-point bending test. The subcritical crack growth parameters n and A were determined in a dynamic fatigue method at four decreasing loading rates from 110MPa/s to 0.11MPa/s in distilled water at 38°C. For each loading rate Weibull statistics were performed and the Weibull moduli m and characteristic strengths σ(0) were calculated. Using these data, strength-fracture probability-life time (SPT) predictions were derived for 1 day, 1 year, 5 years and 10 years, based on a static crack growth mechanism.
The "hipped" Y-TZP ceramic exhibited a higher initial strength (σ(c)=1618.18), characteristic strength (σ(0)=837.15) and fracture toughness (K(IC)=4.52MPa/m(1/2)) than the pre-sintered ceramic (σ(c)=1431, σ(0)=745.46 and K(IC)=3.17MPa/m(1/2), respectively). Fatigue parameters, n and A, were 28.5 and 7.97×10(-24) for Everest ZH and 30.15 and 5.47×10(-20) for Everest ZS. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was 259.34MPa for Everest ZH and 263.2MPa for Everest ZS.
Although the "hipped" Y-TZP showed favorable initial mechanical properties, no significant difference could be found in the susceptibility of both ceramics to subcritical crack growth and their long-term strength.
本研究旨在评估预烧结牙科 Y-TZP（卡沃 Everest ZS）和热等静压 Y-TZP（卡沃 Everest ZH）的力学性能和亚临界裂纹扩展行为，并进行寿命数据分析。
为每种材料制作了 150 根弯曲棒。在四点弯曲试验中确定初始断裂强度。在 38°C 的蒸馏水中，以 110MPa/s 至 0.11MPa/s 的四个逐渐降低的加载速率，通过动态疲劳法确定亚临界裂纹扩展参数 n 和 A。对于每个加载速率，进行威布尔统计，计算威布尔模数 m 和特征强度 σ(0)。基于静态裂纹扩展机制，使用这些数据，针对 1 天、1 年、5 年和 10 年的时间，推导了强度-断裂概率-寿命（SPT）预测。
“凸起”Y-TZP 陶瓷的初始强度（σ(c)=1618.18）、特征强度（σ(0)=837.15）和断裂韧性（K(IC)=4.52MPa/m(1/2)）均高于预烧结陶瓷（σ(c)=1431、σ(0)=745.46 和 K(IC)=3.17MPa/m(1/2)）。疲劳参数 n 和 A 分别为 Everest ZH 的 28.5 和 7.97×10(-24)，以及 Everest ZS 的 30.15 和 5.47×10(-20)。在预测的 10 年寿命时，失效概率为 5%的断裂应力，Everest ZH 为 259.34MPa，Everest ZS 为 263.2MPa。
尽管“凸起”Y-TZP 显示出有利的初始力学性能，但两种陶瓷在亚临界裂纹扩展的敏感性及其长期强度方面均无显著差异。
