Doctoral Dissertation Research: Microstructure and Mechanical Properties of Primate Tooth Enamel

这项博士论文研究将探索牙齿的一个重要方面及其在饮食生态学中的作用，通过测试牙釉质抵抗咀嚼过程中施加的力的断裂和磨损的能力。来自不同灵长类动物物种的牙釉质将使用材料科学工程的方法进行成像和机械测试，以更好地了解牙齿内部结构与其性能之间的关系。这项研究的结果将说明牙齿咀嚼坚韧食物的机制，这可能会为研究开发更强大的磨损和破碎牙齿的替代品提供信息，以及更好地重建灭绝人类和动物饮食的研究。该研究将支持研究生培训和本科实验室课程的开发，强调在工程应用中使用牙科生物学和人类学的概念。本研究将探讨牙釉质的形成如何有助于其抵抗牙齿失效的功能。在微米和纳米尺度上，釉质是由许多小晶体形成的，这些小晶体以复杂的模式捆绑在一起。这些图案被认为有助于牙齿抵抗磨损，通过将晶体排列在对磨损反应最强烈的方向上。此外，一种高度复杂的交织晶体模式被认为有助于防止裂纹穿过釉质并导致牙齿碎裂或开裂。这项研究结合了离子束显微镜对釉质的微观和纳米结构进行精细成像，以及材料科学工程的压痕方法，以确定施加力时釉质结构的反应。为了了解这些结构如何在人类牙齿中发挥作用，将其特性的变化与其他密切相关的物种进行比较。出于这个原因，分析样本包括人类和一系列非人类灵长类动物的牙齿，包括黑猩猩和狒狒。最终，这项研究将加强在我们进化史上从化石中确定饮食时可以做出的推论，并有助于说明牙齿如何以及为什么会断裂。这个奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

This doctoral dissertation study will explore an important aspect of teeth and their role in dietary ecology, by testing the ability of tooth enamel to resist fracture and wear from forces applied during chewing. Tooth enamel from different primate species will be imaged and mechanically tested using methods from materials science engineering to better understand the relationship between the internal structure of teeth and their performance. The results of this study will illustrate the mechanisms that allow teeth to chew tough and hard foods, which may inform research to develop stronger replacements for worn and broken teeth, as well as research to better reconstruct the diet of extinct humans and animals. The study will support graduate student training and the development of undergraduate laboratory coursework that emphasizes the use of concepts from dental biology and anthropology in engineering applications. This study will address how the form of enamel contributes to its function in resisting tooth failure. At micro- and nanometer scales, enamel is formed out of many small crystals that are bundled together in complex patterns. These patterns are thought to help teeth resist wear by aligning crystals in a direction where they are strongest in response to abrasion. Additionally, a highly complex pattern of interwoven crystals is believed to help prevent cracks from moving through enamel and leading to a chipped or cracked tooth. This study combines ion beam microscopy to image micro- and nanometer structures of enamel in fine detail, and indentation methods from material science engineering to determine how enamel structures respond when forces are applied. To understand how these structures function in human teeth, the variation in their properties will be compared with those of other closely related species. For this reason, the analytical sample includes teeth from humans and a range of non-human primates including chimpanzees and baboons. Ultimately, this study will strengthen the inferences that can be made when determining diet from fossils in our evolutionary past, and help to illustrate how and why teeth break.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.