Homeostasis of Dental Hard Tissues

牙齿侵蚀可以定义为由于非细菌来源的酸的化学溶解而导致牙齿结构的不可逆转的损失。最常见的腐蚀原因是酸性食物和饮料。牙齿侵蚀已被描述为一个日益相关的问题。许多运输工具中的氟化物，尤其是含氟化物的牙膏，已经显著减少了因蛀牙而脱落的牙齿。然而，氟化物对牙釉质腐蚀的影响有限。再加上寿命的延长，这意味着人们不仅寿命更长，而且他们的牙齿在一生中会越来越多地接触到膳食酸。直觉上，人们可能会认为新长出的牙齿是最强壮的。然而，情况并非如此，在爆发后成熟（PEM）期间，它们通过与口腔液体的化学相互作用变得更硬，更少多孔。能够降低牙釉质溶解度的物质，如氟化物和金属离子，也会进入牙齿表面。有人提出，这一过程是由牙龈边缘形成的牙菌斑驱动的（由于刷新牙困难，部分爆发的牙齿），有助于口腔环境中脱矿和再矿化状态的不断变化。虽然我们对牙齿的物理变化已经比较了解了，但我们对唾液和牙齿之间影响这些变化的化学相互作用知之甚少，也就是说，我们知道发生了什么，但不知道是如何发生的。此外，虽然PEM对龋齿的保护作用被广泛报道，但有关PEM对腐蚀的影响的信息在文献中基本上是缺失的。该项目的目的是进一步了解PEM期间牙齿-唾液界面的物理化学相互作用对随后对侵蚀的敏感性的影响。这是通过一种新型的体外PEM ph循环模型实现的，该模型模拟了口腔环境中正常一天中去矿化和再矿化状态的波动。在ph循环之后，样品暴露于侵蚀挑战中，以便评估模型中使用的不同测试条件的有效性，使用以下技术；定量光诱导荧光（QLF-D），横向显微放射照相（TMR）和非接触表面轮廓测定（NCSP）。初步研究结果表明，与对照组相比，暴露于ph循环模型的样品对酸侵蚀的抵抗力更强。基于这些发现，在该模型的背景下，已经/正在进行评估不同抗侵蚀处理效果的研究。到目前为止，金属离子处理（即氟化锡和锌）在暴露于ph循环模型时，已经显著减少了侵蚀挑战的脱矿作用。展望未来，还将进行评估有前途的抗腐蚀剂（即四氟化钛和锶）效果的研究。除了这些研究之外，还将使用扫描电子显微镜（SEM）结合能量色散x射线光谱学（EDX）或波长色散光谱学（WDS）等技术对暴露于该模型的牙釉质的化学成分进行分析，这将为了解口腔中发生的导致PEM的化学相互作用提供急需的见解。

Dental erosion can be defined as the irreversible loss of tooth structure due to chemical dissolution by acids not of bacterial origin. The most common causes of erosion are acidic foods and drinks. Dental erosion has been described as an increasingly relevant problem. Fluoride from many delivery vehicles, but especially fluoride-containing toothpastes, has led to marked reductions in teeth lost through dental caries. However, fluoride has a limited effect on enamel erosion. Coupled with increased longevity, this means that not only are people living longer but that their teeth will be increasingly exposed to dietary acids over the life-course. Intuitively one might think that newly-erupted teeth would be at their strongest. However, this is not the case and during Post-Eruptive Maturation (PEM) they become harder and less porous via chemical interactions with the oral fluids. Species with the ability to reduce enamel solubility, such as fluoride and metal ions, are also incorporated into the tooth surface. It has been proposed that this process is driven by the formation of plaque around the gum margin (as a result of difficulty brushing new, partially erupted teeth) contributing to a constantly shifting dynamic of demineralisation and remineralisation states within the oral environment. Although the physical changes in the tooth are relatively well understood, very little is known about the chemical interactions between saliva and the tooth that effect these changes, i.e. we know what happens, but not how. Further, while the protective effect conferred against dental caries by PEM is widely reported, information relating to the effect of PEM on erosion is essentially absent from the literature. The aim of the project has been to develop greater understanding of the effects of the physico-chemical interactions at the tooth-saliva interface during PEM on subsequent susceptibility to erosion. This has been achieved using a novel in vitro PEM pH-cycling model that mimics fluctuations in the de- and remineralisation states within in the oral environment over the course of a regular day. Following pH-cycling, samples are exposed to an erosive challenge in order to assess the efficacy of different test conditions used within the model, using techniques such as; quantitative light-induced fluorescence (QLF-D), transverse micro-radiography (TMR) and non-contact surface profilometry (NCSP). Initial findings demonstrated that samples exposed the pH-cycling model were more resistant to acid erosion compared to control groups. Building on these findings, studies evaluating the efficacy of different anti-erosive treatments within the context of this model have been/ are being conducted. So far, metal ion treatments (i.e. Stannous Fluoride and Zinc) have affected significant reductions in demineralisation from erosive challenges when exposed to the pH-cycling model. Moving forward, studies evaluating the effect of promising anti-erosive agents (i.e. Titanium Tetrafluoride and Strontium) will also be conducted. In addition to these studies, analysis of the chemical composition of enamel from exposure to this model will be assessed using scanning electron microscopy (SEM) in conjunction with techniques such as energy-dispersive x-ray spectroscopy (EDX) or wavelength dispersive spectroscopy (WDS), which will provide much needed insight into chemical interactions occurring in the oral cavity which contribute to PEM.