A Determination of the Cyclic Fatigue Crack Growth Properties of Human Teeth

9900296牙科修复体在维护终身口腔健康中发挥着不可或缺的作用。因此，由于反复发生的牙齿腐烂、边缘不一致和牙齿断裂而导致的牙齿修复失败，是具有重要临床意义的话题。这项研究的目的是证明牙齿中的周期性疲劳裂纹扩展是导致牙齿修复失败的一个重要且在很大程度上未被认识到的机制。要测试的假设是，牙齿中的疲劳裂纹扩展始于牙刺的空洞准备过程中引入的缺陷，并由包含标准口腔活动的循环机械和热负荷驱动。裂纹不断扩展，直至达到临界裂纹长度，从而使生物牙结构丧失或修复体体断裂。在这项研究中，人牙本质的循环裂纹扩展速率和门槛裂纹长度将通过对四点弯曲的牙本质样本进行的实验分析来确定。疲劳试件将使用数控切片机/研磨机从人的牙齿中制备。通过应用I型循环压缩，在零到最大四点弯曲疲劳载荷之前，将在每个试件中引入一个预疲劳裂纹。弯曲载荷引起的循环裂纹扩展速率将用瞬时裂纹长度和最大循环弯曲应力来量化。利用从实验分析中获得的疲劳裂纹累积扩展数据，将根据巴黎定律确定描述疲劳裂纹循环扩展的参数。实验研究的结果将确定在洞穴准备过程中引入的亚表面缺陷对修复牙齿疲劳寿命的重要性。

9900296ArolaDental restorations play an integral role in the maintenance of lifelongoral health. Consequently, the failure of dental restorations through reoccurring tooth decay, marginal discrepancies, and tooth fracture, are topics of substantial clinical significance. The objective of the research is to show that cyclic fatigue crack growth in teeth is an important and largely unrecognized mechanism that contributes to dental restoration failure. The hypothesis to be tested that that fatigue crack growth in teeth initiates at flaws introduced during cavity preparation with dental burs and is driven by cyclic mechanical and thermal loads which encompass standard oral activity. The flaw propagates until reaching a critical crack length which enables the loss of biological tooth structure or bulk fracture of the restoration. In this study the cyclic crack growth rate in human dentin and the threshold crack length will be determined from an experimental analysis conducted with four-point-bend dentin specimens. Fatigue specimens will be prepared from human teeth using a numerically controlled slicer/grinder. A pre-fatigue crack will be introduced in each specimen, prior to zero-to-maximum four point bend fatigue loading, through the application of Mode I cyclic compression. The cyclic flaw growth rate resulting from bend loading will be quantified in terms of the instantaneous crack length and maximum cyclic bend stress. Using the cumulative fatigue crack growth data obtained from experimental analysis, the parameters describing cyclic fatigue crack growth according to the Paris Law will be determined. Results from the experimental study will identify the significance of subsurface flaws introduced during cavity preparation on the fatigue life of restored teeth.