Aging and Fatigue Crack Growth in Dentin

牙齿折断导致的修复失败是影响终身口腔健康的主要障碍之一。这个 我们研究的总体假设是，修复牙齿的骨折是由于疲劳的减少而造成的 牙本质裂纹扩展抗力随年龄的变化。我们的初步研究表明，疲劳裂纹通常是 存在于修复牙的牙本质中，牙本质的疲劳特性是由 肾小管定位与患者年龄有关。尽管牙本质的结构随着年龄的增长发生了明显的变化，而且 老年人牙折多发，老化对疲劳的影响 牙本质的性质仍不清楚。随着部分和全齿老年人的增加， 因牙齿修复而导致的衰老已变得越来越重要。我们建议对疲劳程度进行量化 牙本质裂纹扩展特性与患者年龄、性别和牙本质小管方向的关系 辨别最有害的变化发生在什么年龄，并确定基本机制 负责减少裂纹扩展阻力。将对疲劳裂纹的萌生和扩展进行评估 从拔除的原始磨牙的冠状牙本质制备的人牙本质标本。它的作用机制 将使用一种新的数字图像应用来表征裂纹的萌生和循环扩展 根据患者的年龄和性别进行相关性和评估。结构和化学的变化 还将使用分析显微技术来评估牙本质的含量。调查结果将 对牙本质的疲劳裂纹扩展特性有一个基本的了解 开发详细的结构-属性关系。基于定量结果和 了解促进机制，我们希望确定现有恢复剂的关键方面 牙齿折裂的治疗和治疗老化齿状突牙的潜在需要 人口。这一结果有望支持临床止裂技术的发展。 牙齿结构涉及机械和化学方法来修复。希望我们的发现能 帮助确定增强牙齿组织抗疲劳性的方法，无论年龄大小。这些 取得的成就应该会减少与牙齿断裂相关的修复失败的发生率，从而导致 节省数十亿美元的医疗保健费用，以及减少人类的痛苦。

Restoration failures resulting from tooth fracture are one of the primary obstacles to lifelong oral health. The overall hypothesis of our study is that the fracture of restored teeth is fostered by a reduction in the fatigue crack growth resistance of dentin with age. Our preliminary studies have shown that fatigue cracks are often present in the dentin of restored teeth and that the fatigue properties of dentin are a function of both the tubule orientation and patient age. Despite distinct changes in the structure of dentin with age, and identification that tooth fractures occur more frequently in seniors, the influence of aging on the fatigue properties of dentin has remained unknown. With the increase in partially and full dentate seniors, the role of aging on restored tooth failures has become increasingly important. We propose to quantify the fatigue crack growth properties of dentin as a function of patient age, gender and dentin tubule orientation, distinguish at what age the most detrimental changes take place, and identify, the fundamental mechanisms responsible for reduction in crack growth resistance. Fatigue crack initiation axnd growth will be evaluated in human dentin specimens prepared from the coronal dentin of extracted virgin molars. The mechanisms of crack initiation and cyclic crack extension will be characterized using a novel application of digital image correlation and evaluated in terms of the patient's age and gender. Changes in the structure and chemistry of dentin will also be evaluated using analytical microscopic techniques. Results of the investigation will provide a fundamental understanding of the fatigue crack growth properties of dentin that enable development of detailed structure-property relationships. Based on both quantitative results and an understanding of contributing mechanisms, we expect to identify the critical aspects of existing restorative treatments on tooth fracture and the potential need for new approaches in treatment of the aging dentate population. The results are expected to support development of clinical techniques for arresting cracks in tooth structure that involve both mechanical and chemical approachesto repair. Hopefully our findings will help identify approaches for strengthening the fatigue resistance of tooth tissues, regardless of age. These achievements should reduce the incidence of restorative failures associated with tooth fracture, resulting in billions of dollars in savings of health care costs, as well as a reduction in human suffering.