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

本博士论文研究将通过测试牙釉质在咀嚼过程中抵抗断裂和磨损的能力，探索牙齿及其在饮食生态中的重要作用。不同灵长类动物的牙釉质将通过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。这项研究的结果将阐明牙齿咀嚼坚硬食物的机制，这可能会为研究开发更坚固的替代磨损和断裂的牙齿，以及更好地重建灭绝的人类和动物的饮食研究提供信息。这项研究将支持研究生的训练和本科实验课程的发展，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态如何影响其抵抗牙齿衰竭的功能。在微观和纳米尺度上，牙釉质是由许多小晶体以复杂的图案捆绑在一起形成的。这些图案被认为可以帮助牙齿抵抗磨损，因为它们将晶体排列在对磨损反应最强的方向上。此外，一种高度复杂的晶体交织图案被认为有助于防止裂缝穿过牙釉质，导致牙齿断裂或破裂。本研究结合离子束显微镜对牙釉质的微观和纳米结构进行精细成像，并结合材料科学工程的压痕方法来确定牙釉质结构在施加力时的反应。为了了解这些结构如何在人类牙齿中发挥作用，将与其他密切相关物种的牙齿进行比较。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，这项研究将加强从我们进化史上的化石中确定饮食时可以做出的推断，并有助于说明牙齿是如何以及为什么断裂的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.