Role of Water in Dental Hard Tissues

总结 水是牙体硬组织的三大主要成分之一，但水的结构和如何形成牙体硬组织， 在牙齿形成、退化和损伤过程中，水与牙齿硬组织中的其他组分相互作用 仍然不清楚。核磁共振（NMR）和红外吸收（IR）是可以 直接探测生物组织中的水分。然而，它们的性能是有限的，因为NMR仅 测量样品的平均效果，而IR需要对牙齿等组织进行特殊准备， 改变组织的性质。最近，我们证明了荧光压缩拉曼光谱 具有探测牙齿硬组织中的水的能力，并显示水的光谱分布是 牙本质和牙釉质之间的差异在不同的测试中，即使在釉质中，这些特征也不同 斑点。这些结果表明，拉曼光谱可以提供有关的作用， 牙齿硬组织中的水，以及可能影响对牙齿硬组织机制理解的细节。 问题拟议项目的主要目的是使用拉曼光谱来确定 牙齿硬组织中的水含量和结构的变化可能与牙齿组织相关 病理学目标1将确定最佳可用的拉曼光谱配置， 探测牙齿硬组织中的水含量。三种常见的荧光抑制方法，即， 近红外激发结合InGaAs探测器、UV共振拉曼和时间选通拉曼光谱 将被比较，以确定如何与水相关的拉曼信号的信噪比可以 最大限度地增强。我们期望将系统灵敏度提高一个或更多个数量级。目标2将 考察拉曼光谱反映的水量变化和结构变化 并确定这些变化是否与牙科硬组织中的其他化学/物理变化相关 组织中牙齿与不同程度的脱矿物质和有机物分解将准备显示 不同程度的化学成分变化。将从这些模拟样品中获得拉曼光谱 并用作探测具有自然发展的龋齿的牙齿中的组成变化的参考。拉曼 光谱学也将与微观力学测试相结合，以确定水之间的相关性 含量和结构的变化以及力学性能的变化。

Summary Water is one of the three major constituents of dental hard tissues, but the structure of water and how water interacts with other components in dental hard tissues during teeth formation, degradation, and lesion remain unclear. Nuclear magnetic spectrometry (NMR) and infrared absorption (IR) are the methods that can directly probe water from biological tissues. However, their performances are limited because NMR only measures the average effect of the sample, while IR requires special preparations to tissues like teeth and could alter the properties of the tissues. Recently, we demonstrated that fluorescence compressed Raman spectroscopy has the capability of probing water in dental hard tissues and showed that the spectral profiles of water are dramatically different between dentin and enamel. The profiles varied even within enamel at different testing spots. Those results indicate that Raman spectroscopy may provide additional information about the role of water in dental hard tissues with details that may impact the understanding of the mechanisms of dental problems. The major aim of the proposed project is to use Raman spectroscopy to identify how the changes in water content and structure in dental hard tissues may correlate with dental tissue pathologies. Aim 1 will determine the best available Raman spectroscopy configurations for probing water contents in dental hard tissues. Three common fluorescence suppression approaches, i.e., near-infrared excitation combining InGaAs detector, UV resonance Raman, and time-gated Raman spectroscopy will be compared to determine how the signal to noise ratio of the water-related Raman signals can be maximumly enhanced. We expect to increase the system sensitivity by one order or more. Aim 2 will investigate the changes in water amount and structure changes reflected by Raman spectroscopy and identify if these changes are correlated with other chemical/physical changes in dental hard tissues. Teeth with various degrees of demineralization and decomposing of organics will be prepared to show deferent levels of chemical compositional changes. Raman spectra will be acquired from these simulated samples and used as references for probing compositional variations in teeth with naturally developed caries. Raman spectroscopy will also be combined with micro-mechanical testing to identify correlations between water contents and structure change and mechanical property changes.