Are controlled localised degradation of resin composites and remineralisation effective in preventing secondary caries?

项目简介：随着健康老龄化，牙齿填充材料的需求呈现稳步增长的趋势，预计2021年至2027年的复合年增长率为5.6%，20201全球牙齿填充材料的市场规模估计超过18亿美元。牙科树脂复合体是儿童和成人最常用的直接修复体材料，每年的失败率为1-4%。失败修复体的修复耗费了大量的临床时间，并对医疗保健系统和患者造成了高昂的经济成本。继发性龋齿是修复体替换的主要原因，其发生是由于树脂复合材料的聚合收缩导致修复体与牙齿组织之间产生微裂缝。局部退化会加速微裂纹的发展。微小龋齿的存在使唾液中的致龋菌生长，导致修复边缘的继发性龋齿。避免微裂纹和局部降解是抑制继发性龋病最有效的方法，然而，由于单体聚合和固化的性质，与光固化牙科树脂复合材料的聚合收缩相关的体积损失和由于未转化的C=C键引起的局部降解是不可避免的，因此，微裂纹是不能完全避免的。尽管人们建议使用不同的预防方法，如使用氟化物、清洁牙齿、定期检查，但其有效性强烈依赖于个人的遵从性。显然缺乏内在的预防机制。这个PHD项目旨在1)更好地了解继发性龋病的机制，2)建立实验室模型和细胞培养模型来监测微裂纹的发展和继发性龋病的进展，3)评估树脂复合材料的局部可控降解和再矿化在预防继发性龋病方面的有效性，以及4)最终开发出一种生物安全的、有效地预防继发性龋病的树脂复合材料，以改善口腔健康。成功的应聘者将有机会了解牙科树脂复合材料的配方，并根据ISO 4049-2019和牙科材料学会推荐的方法表征一系列与临床相关的性能，以了解树脂复合材料的化学、结构和性能关系。将监测微裂纹的发展和继发性龋齿的进展，并将调查生物安全性，包括细胞毒性和磷灰石形成。曼彻斯特大学亨利·罗伊斯研究所内的一系列最先进的世界级表征设施将被使用，包括纳米级AFM-IR-用于绘制局部转化程度、水降解(重水D2O)和磷灰石形成的地图。成功的候选人将有机会参加博士学院培训方案，并有机会参加和领导外联活动。我们还有机会拜访位于中国的中南大学湘雅口腔医学院的全球合作伙伴陈晓静教授。

Project Description: With health aging, the demand of tooth filling materials has shown a steady increase with an estimated compound annual growth rate of 5.6% between 2021 and 2027 and the global market size of tooth filling materials was valued at over USD 1.8 billion in 20201. Dental resin composites are the most commonly used direct restorative materials for children and adults with a reported annual failure rate of 1-4%2. The replacement of failed restorations consumes a significant amount of clinical time and imposes high financial costs for both health care systems and patients.Secondary caries is the main reason for restoration replacement and occurs as a consequence of microcracks developed between the restoration and tooth tissues due to polymerisation shrinkage of resin composites. Localised degradation can accelerate the development of mirocracks. The presence of microcarcks allows cariogenic bacteria in saliva to grow leading to secondary caries at restoration margins. Avoid micocracks and localised degradation would be the most effective ways to inhibit secondary caries, however, due to the nature of the monomer polymerisation and solidification, volume loss associated with the polymerisation shrinkage of light curable dental resin composites and localised degradation arose from the unconverted C=C bond are unavoidable, therefore, microcracks can not be completely avoided. Despite different prevention methods such as the use of fluoride, teeth cleaning, regular check-ups have been suggested, the effectiveness is strongly dependent on individual compliances. There is a clear lack of intrinsic preventative mechanism. This PhD project aims to 1) better understand the mechanism of secondary caries, 2) establish lab model and cell culture model to monitor the development of microcracks and the progression of secondary caries, 3) evaluate the effectiveness of controlled localised degradation and remineralisation of resin composites in preventing secondary caries, and 4) ultimately develop a biologically safe resin composite that is effective in preventing secondary caries for better Oral Health. The successful candidate will have the opportunity to learn how dental resin composites are formulated, and characterise a wide range of clinical relevant properties following ISO 4049-2019 and methods recommended by Academy of Dental Materials to understand the chemical, structural and property relationship of resin composites. The development of microcracks and the progression of secondary caries will be monitored and the biological safety including cytotoxicity and apatite formation will be investigated. A range of the state-of-the-art world-class characterisation facilities within the Henry Royce Institute at the University of Manchester will be used including a nanoscale AFM-IR - to be employed to map the localised degree of conversion, water degradation (heavy water D2O) and apatite formation. The successful candidate will have access to Doctoral Academy Training Programme and opportunities to participate and lead outreach activities. Opportunity to visit global partner Prof. Xiaojing Chen at the Xiangya School of Stomatology, Central South University in China may also be possible.