Fatigue of Restorative Ceramics

牙科陶瓷因其美观而成为越来越多的修复材料。 外观、耐磨性、隔热和生物相容性。不幸的是，牙科陶瓷 与牙科合金相比，它比较脆。这种抗裂性的缺乏损害了它们的强度和 可靠性，导致寿命缩短。咬合载荷的大小很少超过324N 有限元模型预测，这些载荷将在人体内产生22至87兆帕的应力 磨牙牙冠。传统的牙科陶瓷可以承受11.6兆帕(铝瓷)到240兆帕(双色)。 单周破坏前的应力。尽管有这个安全边际，但在以下情况下，失败率高达30%(DICOR) 已经有七年的活体实验报告。循环疲劳载荷显然对最大应力有影响 这是可以承受的，疲劳失效理所当然地成为牙科陶瓷研究人员关注的问题。疲劳破坏 当初始缺陷在亚临界裂纹扩展(SCG)后达到临界应力强度时，陶瓷材料就会发生裂纹扩展。 这个项目的总体目标是开发更简单的方法来测量牙科陶瓷的SCG，并 开发更准确的方法来预测全陶瓷假体的寿命，通过以下具体的 目的：(1)发展一种建立精确的S-N-P(应力-寿命-失效概率)模型的方法 牙科陶瓷在最小数量的标准几何试件上进行循环疲劳测量。 (2)发展确定应力腐蚀和循环的单独贡献的方法 对于给定的陶瓷和应力函数，退化为SCG。(3)验证假体寿命的准确性 结合使用有限元软件和时间相关可靠性软件进行预测。(4)至 确定疲劳强度分布与单循环强度分布之间的关系。(5)至 确定通过表面重塑修复裂纹是否会影响疲劳寿命。具体目标1-4将 研究两种牙科陶瓷：一种表现出恒定的断裂韧性，另一种表现出 断裂韧性与缺陷尺寸的关系(R曲线行为)。能愈合裂缝的瓷器 行为将在具体目标5中进行分析。

Dental ceramics have become increasingly prolific as restorative materials because of their esthetic appearance, wear resistance, thermal insulation, and biocompatibility. Unfortunately, dental ceramics are brittle in comparison to dental alloys. This lack of fracture resistance compromises their strength and reliability, resulting in decreased lifetime expectancy. The magnitude of occlusal load rarely exceeds 324 N in humans, and finite element models have predicted these loads to induce stresses of 22 to 87 MPa in molar crowns. Traditional dental ceramics can withstand 11.6 MPa (aluminous porcelains) to 240 MPa (Dicor) of stress before single-cycle failure. In spite of this margin of safety, failure rates as high at 30% (Dicor) after seven years in vivo have been reported. Cyclic fatigue loading clearly has an impact on the maximum stress that can be withstood, and fatigue failure is rightfully a concern of dental ceramic researchers. Fatigue failure of ceramics occurs when initial flaws reach a critical stress intensity following subcritical crack growth (SCG). The overall goals of this project are to develop easier methods of measuring SCG for dental ceramics and to develop more accurate methods for predicting all-ceramic prothesis lifetimes through the following specific aims: (1) To develop a method for constructing accurate S-N-P (stress-lifetime-failure probability) models for dental ceramics from cyclic fatigue measurements on a minimum number of standard geometry specimens. (2) To develop a method for determining the individual contributions of stress corrosion and cyclic degradation to SCG for a given ceramic and stress function. (3) To verify the accuracy of prosthesis lifetimes predicted using finite element software in conjunction with time-dependent reliability software. (4) To determine how the distribution of fatigue strength relates to the distribution of single-cycle strength. (5) To determine whether crack healing through surface remodeling affects fatigue lifetime. Specific Aims 1-4 will investigate two dental ceramics: one that exhibits constant fracture toughness and one that exhibits dependence of fracture toughness on flaw size (R-curve behavior). A porcelain that exhibits crack healing behavior will be analyzed in Specific Aim 5.