Aging and Fatigue Crack Growth in Dentin

描述（由申请人提供）：牙齿断裂导致的修复失败是终身口腔健康的主要障碍之一。我们研究的总体假设是，修复牙齿的断裂是由牙本质随年龄增长的疲劳裂纹生长阻力降低引起的。我们的初步研究表明，疲劳裂纹往往存在于修复牙齿的牙本质中，牙本质的疲劳特性是小管方向和患者年龄的函数。尽管牙本质的结构随着年龄的增长而发生明显的变化，并且老年人的牙齿骨折发生率更高，但老化对牙本质疲劳特性的影响仍然未知。随着老年人部分和全牙列的增加，年龄对牙齿修复失败的作用变得越来越重要。我们建议量化作为患者年龄，性别和牙本质小管方向的函数的牙本质的疲劳裂纹生长特性，区分在什么年龄发生的最有害的变化，并确定，负责裂纹生长阻力降低的基本机制。疲劳裂纹的产生和扩展将在从拔除的处女磨牙的冠状牙本质制备的人类牙本质样本中进行评价。裂纹萌生和周期性裂纹扩展的机制将使用数字图像相关性的新应用程序进行表征，并根据患者的年龄和性别进行评估。牙本质的结构和化学变化也将使用分析显微镜技术进行评价。调查结果将提供牙本质的疲劳裂纹扩展特性，使详细的结构-性能关系的发展的基本理解。基于定量结果和对促成机制的理解，我们期望确定现有牙折修复治疗的关键方面，以及老年齿状人口治疗新方法的潜在需求。这些结果有望支持临床技术的发展，以阻止牙齿结构中的裂纹，包括机械和化学方法来修复。希望我们的研究结果将有助于确定增强牙齿组织抗疲劳性的方法，无论年龄如何。这些成就应减少与牙齿断裂相关的修复失败的发生率，从而节省数十亿美元的医疗保健费用，并减少人类的痛苦。

DESCRIPTION (provided by applicant): 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 approaches to 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.