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

Lead Research Organisation: University of Manchester
Department Name: School of Medical Sciences


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.


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