Statement of problem

The lack of standardization regarding the loading piston material used in fatigue tests could limit the interpretation of study findings.

Purpose

The purpose of this in vitro study was to evaluate the effect of the piston material on the fatigue behavior of a lithium disilicate glass-ceramic.

Material and methods

Plate-shaped, 1.2-mm-thick, lithium disilicate glass-ceramic specimens were cemented onto a dentin analog substrate with resin cement. The specimens were divided into 4 groups according to the piston material used in the fatigue test (n=30): metal, glass fiber-reinforced epoxy resin, ceramic, and human tooth. The fatigue test was performed in a mechanical cycling machine by using the boundary technique at 2 Hz in distilled water at 37 °C. The fatigue data were analyzed by using the Weibull distribution and a lifetime-inverse power law relationship. Failures were evaluated with fractography and transillumination.

Results

The Weibull modulus (β) was similar among groups. The exponent of crack growth (n) was significantly greater for glass fiber-reinforced epoxy resin and tooth groups than for metal and ceramic; therefore, the probability of failure (P_f) of glass-ceramic specimens loaded by resin and tooth pistons depended more on load amplitude. Specimens tested with tooth showed the highest value of K (characteristic lifetime), which is an indication of greater survival. Radial crack was the only failure mode observed for all experimental groups.

Conclusions

The piston material influenced the fatigue survival of the lithium disilicate glass-ceramic. The glass fiber-reinforced epoxy resin piston closely simulated the fatigue behavior induced by the human tooth on the evaluated glass-ceramic.

中文翻译：

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活塞材料对微晶玻璃疲劳性能的影响

 问题陈述

疲劳测试中使用的加载活塞材料缺乏标准化可能会限制对研究结果的解释。

 目的

这项体外研究的目的是评估活塞材料对二硅酸锂玻璃陶瓷疲劳行为的影响。

 材料与方法

使用树脂水门汀将 1.2 毫米厚的板状二硅酸锂玻璃陶瓷标本粘合到牙本质模拟基底上。根据疲劳试验中使用的活塞材料（n=30）将试样分为4组：金属、玻璃纤维增​​强环氧树脂、陶瓷和人牙。疲劳测试是在机械循环机中使用边界技术在 37°C 蒸馏水中以 2 Hz 频率进行的。使用威布尔分布和寿命-逆幂律关系对疲劳数据进行分析。通过断口照相术和透照法评估失效情况。

 结果

各组之间的威布尔模量 (β) 相似。玻璃纤维增​​强环氧树脂和齿组的裂纹扩展指数 ( n ) 明显大于金属和陶瓷；因此，由树脂和齿活塞加载的玻璃陶瓷样品的失效概率（P _f ）更多地取决于载荷幅度。用牙齿测试的样本显示出最高的 K 值（特征寿命），这表明存活率更高。径向裂纹是所有实验组观察到的唯一失效模式。

 结论

活塞材料影响二硅酸锂玻璃陶瓷的疲劳寿命。玻璃纤维增​​强环氧树脂活塞在所评估的玻璃陶瓷上紧密模拟了人类牙齿引起的疲劳行为。