Mucin layer behaviour and its role in dental tribology

Over the past few decades, the prevalence of tooth loss has gained more attention within the realm of oral and dental tribology. Corrosion and tribocorrosion are areas for concern, with the potential to cause increased tooth loss in vulnerable populations who cannot naturally produce saliva to protect their tooth enamel. Improvements to therapies are required to provide enhanced protection to tooth enamel. This thesis investigates the role of mucin from the perspective of tooth enamel protection, by uncovering mechanisms of dental lubrication with mucin, whilst understanding mucin’s contribution to of tooth tribocorrosion and its overall viability for protection. Mucin-environments and mucin-surface adsorption experimented were completed using DLS, AFM, QCM-D, and in-situ QCM-D tribometer techniques, which provided further insight into the mechanical and rheological properties of mucin layers. Static and dynamic tribocorrosion experiments investigated the individual components of overall tooth wear, and whether mucin provided protection under these conditions. Experiments indicated that solution composition and surface chemistries were critical factors of mucin layer adsorption, surface coverage, mucin structures and subsequent lubrication. The load-bearing properties of mucin were quantified by using an AFM, which was influenced by PBS. PBS significantly improved enamel wear resistance, which was linked to load-bearing, with evidence of increased mucin within wear sites. In-situ investigations were developed that examined the role of mechanical interactions, which provided insight into the potential compaction of mucin layer within the tribological interface, and subsequent tribofilm. Tribocorrosion experiments uncovered the components to quantify the total tooth degradation, and mucin was observed to not provide any additional benefit to lubrication, or surface protection within an acidic environment. From the findings presented in this thesis, mucin has been shown to provide enhanced protection and lubrication within a neutral pH PBS environment. However, for mucin to protect enamel in an acidic environment, a complementary component is required.