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

[9900296]口腔修复在维持生命和口腔健康方面起着不可或缺的作用。因此，由于反复发生的蛀牙，边缘差异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主题。研究的目的是表明牙齿的循环疲劳裂纹扩展是一个重要的和很大程度上未被认识的机制，有助于牙修复失败。要测试的假设是，牙齿疲劳裂纹的增长始于在用牙刺准备腔时引入的缺陷，并由包含标准口腔活动的循环机械和热负荷驱动。裂纹扩展到一定的临界裂纹长度，使修复体丧失生物牙结构或本体断裂。在本研究中，人类牙本质的循环裂纹生长速率和阈值裂纹长度将通过对四点弯曲牙本质样本进行实验分析来确定。疲劳试样将从人的牙齿准备使用数控切片机/磨床。通过I型循环压缩的应用，在零至最大四点弯曲疲劳加载之前，每个试件将引入预疲劳裂纹。弯曲荷载引起的循环裂纹扩展速率将被量化为瞬时裂纹长度和最大循环弯曲应力。利用实验分析得到的累积疲劳裂纹扩展数据，确定符合巴黎定律的描述循环疲劳裂纹扩展的参数。实验研究的结果将确定在空腔制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.