Multi-scale Tomography Investigation of Dental Erosion [Sponsor: GSK; FULLY FUNDED]

This PhD is part of the EPSRC Centre for Doctoral Training in Materials for Demanding Environments [M4DE CDT]; it is sponsored by GSK, and will commence September 2018.

Background
Dental erosion is the loss of dental hard tissue through chemical dissolution of the tooth structure in the absence of bacterial involvement (in contrast to dental caries) [1]. In our demanding oral environment, erosion results in progressive loss of the tooth structure often necessitating complex dental rehabilitations. It is common in both children and adults and represents a significant challenge to dental practitioners in terms of the predictable management of the damaged dentition. As a progressive condition, due to the lack of intrinsic biological repair mechanisms for dental enamel, dental erosion is of particular relevance to our ageing population and has a significant impact on the quality of life and resources of NHS.
Considerable effort has been spent on modelling dental erosion ex-vivo, these approaches typically expose animal or human tooth surfaces to an acid challenge and measure the resultant surface changes qualitatively through imaging [2, 3] or quantitatively through metrology and characterisation of surface micromechanical properties [4-7]. The two main limitations are (i) an inability to relate the specific variability of the hierarchically organised mineralised tooth structure & (ii) difficulties in monitoring the sequence of dissolution and its impact on structural integrity in real-time.
All biological tissues are three dimensional and contain structures that span a range of length scales from nanometres through to hundreds of millimetres. The human tooth is comprised of multiple organised structures such as enamel and dentine. Dentine is a permeable mineralised tissue that forms the bulk of the tooth and is perforated by tubules that extend from the pulp to the enamel-dentine or cementum-dentine junction. When either the enamel or cementum is absent, as a result of erosion and/or attrition, then the dentine is usually covered by a thin layer, composed of mineral and organic debris, termed a smear layer [8]. It is a common observation that hypersensitive dentine is devoid of a smear layer, and evidence by Addy et al [9] has indicated that in hypersensitive teeth the dentine tubules are open at the tooth surface and patent to the pulp. Understanding the mechanism of erosion/attrition of the highly organised enamel in the demanding environment of the oral cavity, with dietary acid exposure and physiological fluid with proteins that promote/depress remineralisation. This is an important step in understanding mechanisms and then being able to design, build and test new oral health care technologies to prevent the loss and damage of enamel/dentin hard tissue.

Project Outline
This project aims to study the influence of hierarchical structure of dental hard tissues on erosion and remineralisation by multi-scale 3D non-destructive X-ray tomography over time and to develop a novel high fidelity in-situ flow cell model of dental erosion permitting real-time multi-modal measurements to identify, monitor and quantify erosive and remineralisation processes in a way not possible by other techniques. Our unique combination of ex-situ and in-situ imaging approaches will provide an opportunity to gain an in depth mechanistic understanding of the kinetics of dental erosion and the effect of oral health dentifrices on the remineralisation of tooth substance (enamel and dentine). The flow-cell developed during the course of the project will provide a new tool to assess the efficacy of commercialised preventative technologies and technologies that are developed in the future.
The successful candidate will have access to the world-class characterisation facilities within the Henry Royce Institute at the University of Manchester, including X-ray imaging/tomography instruments at Henry Moseley X-ray Imaging Facility (HMXIF), suites of the latest electron microscopes and X-ray diffractometers, Solid State NMR and the state-of-the-art surface characterisation techniques such as nanoIR and Nano-Raman Spectroscopy, BioAFM imaging Facility and in-situ nanoindentation. Candidate will also have the opportunity to conduct experiments at the UK National Synchrotron Facility, Diamond Light Source, or other synchrotron facilities in the Europe. It should be noted that candidate will have placement opportunities with GSK.

About industrial sponsor
GlaxoSmithKline is a multinational healthcare company. This project will fall under Glaxosmithkline Consumer Healthcare in regards to oral health and specifically the Sensodyne brand of toothpaste, £1.3B sales/year. The industrial supervisor is Shaz Khan, Expert Visualisation Scientist, who’s role is to investigate new imaging modalities. This to elucidate the biological function of common oral health issues and understand under in vitro conditions the efficacy of new oral healthcare products and to design the next generation of oral health projects.