酸性条件下人牙的摩擦-酸蚀-再矿化自修复耦合作用机制研究

There has been a worldwide increase in the consumption of soft drinks, fruit juices, and sport drinks. Thus, exposure of teeth to an acid environment is becoming commonplace, and erosion has gradually become a main cause for toothwear. Given the fact that erosive substance loss of human teeth is a dynamic process with demineralization and remineralization periods, tooth erosion caused by excessive intake of acidic beverages could be prevented from the headstream by strengthening remineralization of tooth surface under acidic conditions. Thus, it is very necessary to study the tribological behaviour of human teeth in acid solution and then reveal the interaction mechanism of friction, erosion, and remineralization during the process of tooth wear, which could aid in the development of preventive measures for tooth erosion. In this project, the effect of typical acid agents and mineralization agents used in daily foodstuffs on surface morphology, chemical composition, microstructure, mechanical and tribological properties of human teeth will be investigated using in vitro simulation testing, aiming to reveal the interaction mechanism of friction-erosion-remineralization of human teeth. Moreover, further research work on the effect of physiological and pathological factors will be carried out, aiming to find the prerequisite for remineralization self-repair of tooth erosive wear. On this basis, the optimization criterion of acidic beverages will be explored from the aspect of reducing tooth erosion and wear. The results of this research would help deepen the scientific understanding of the tribological properties and self-repair mechanism of natural biomaterials, and then provide important theoretical basis and key technical support for the development of new beverages with low tooth erosion.

酸性饮料过量摄入导致的牙齿酸蚀症日趋严重，酸蚀会显著降低牙齿耐磨性，引发牙齿过度磨损，严重影响人们的生活质量。鉴于酸蚀是牙齿表面脱矿与再矿化平衡被打破的表现，强化牙齿在酸性条件下的再矿化作用，能从源头上抑制牙齿酸蚀损伤。因此，亟需研究人牙在酸性介质中的摩擦磨损行为，阐明人牙的摩擦-酸蚀-再矿化自修复耦合作用机制，为牙齿酸蚀磨损防护措施的研究提供理论依据。本项目拟采用体外模拟试验，研究常见饮料酸味剂、可食用矿化剂等对牙齿表面形貌、化学成分、组织结构、力学性能、摩擦学性能等的影响，揭示酸性条件下人牙的摩擦-酸蚀-再矿化自修复耦合作用机制；在此基础上，进一步考察生理、病理因素的影响，阐明人牙酸蚀磨损再矿化自修复的必要条件，从牙齿减腐降磨的角度探索酸性饮料矿化改性的设计准则。研究成果有助于深化对天然生物材料摩擦学特性及其自修复机制的科学认识，为新型护齿功能饮品的开发提供重要理论基础和关键技术支持。

人体天然牙是人体内最重要的咀嚼器官，牙冠最外层的牙釉质是人体内最硬的组织，对咀嚼磨损具有较好的抵抗力。随着酸性饮料摄入量的增加和人类平均寿命的提高，牙齿酸蚀问题日趋严重，酸蚀磨损已成为现代人类牙齿过度磨损的主要诱因。因此，开展人牙釉质酸蚀损伤及再矿化修复行为的系统研究具有非常重要的理论意义和现实意义。.本项目采用纳米压痕/划痕仪，扫描电子显微镜、电子能谱仪、激光共聚焦扫描显微镜、X射线衍射分析等材料表面分析测试设备，以体外模式开展了再矿化对酸蚀人牙釉质表面形貌、纳米力学性能和微摩擦学行为的影响研究。所取得的主要结论如下：.（1）不同矿化剂的矿化能力和作用机制不同。CPP-ACP溶液对酸蚀牙釉质的纳米力学性能和微观摩擦学性能均有显著修复，但其再矿化层的无定型微观结构和天然牙釉质存在明显差异；天然药物五倍子中鞣酸和没食子酸对酸蚀牙釉质的机械性能和抗磨性均有一定修复作用，但是仅鞣酸作用下的HAP晶体特征接近天然牙釉质；釉原蛋白相关氨基酸有矿化修复作用，Asn诱导的HAP晶体在其C轴存在择优生长，Ser诱导的HAP晶体颗粒较大，小肽3NSS诱导的HAP晶体不仅定向生长且颗粒大，其修复作用显著；柠檬酸溶液中添加微量黄原胶可全面抑制其酸蚀潜力；而添加微量阿拉伯胶则仅对酸蚀牙釉质形貌有改善。.（2）由于组成和结构的差异，乳牙釉质酸蚀耐受性明显低于恒牙釉质。相同酸蚀时间乳牙釉质酸蚀损伤程度较恒牙釉质严重，其机械性能和抗磨性的下降更明显。尽管酸蚀乳牙釉质的再矿化程度不及恒牙釉质，但仍可得到一定程度的修复。.（3）口腔pH环境的改变将显著影响牙釉质表面唾液吸附膜对牙釉质的润滑减磨作用。无柠檬酸影响时，经体外吸附1 min后，牙釉质样品表面可观察到一层20 - 30 nm厚的均匀致密唾液吸附膜；柠檬酸酸蚀后，唾液膜表面的摩擦系数和磨损量明显大于正常唾液膜。酸作用可能引发唾液膜中的吸附蛋白变性和聚合，从而影响唾液吸附膜的多级结构，进而导致其润滑减磨性能的下降。