Observing the Anti-Erosive effects of Post-Eruptive Maturation using an in vitro pH-Cycling Model

Following Amelogenesis when the permanent dentition (and the primary dentition) erupts, enamel will continue to undergo maturation over a ~10-year period, in a process known as Post-Eruptive Maturation (PEM). It has been proposed that PEM is driven by the formation of plaque creating a dynamic where sequential demineralisation events lead to the formation of subclinical carious lesions, followed by subsequent remineralisation from components present in the oral environment and external sources. Knowledge surrounding this phenomenon is limited, with most studies being related to the role of PEM with regards to protection from dental caries. No such studies exist regarding dental erosion, presenting an opportunity to address this lack of knowledge. The current ‘true-to-life’ in vitro PEM pH-cycling model was developed to simulate this demineralisation/ remineralisation dynamic, with oral environment-relevant ion concentrations, background Fluoride ion (F-) concentrations and pH, at timings applicable to events occurring in the oral environment over the course of an average day. Exposure of bovine enamel samples to this model demonstrated statistically significant reductions in fluorescence change (∆F), lesion depth (LD) and integrated mineral loss (∆Z) following exposure to a citric acid erosive challenge. Further, the addition of F- treatments into this model showed an additive protective effect from erosive attack, when compared to pH-cycling or F- treatments alone. The model was able to partially remineralise pre-eroded bovine enamel. Further, additional demineralisation events (to represent snacking) reduced the protective effect of this model, whilst showing significant reductions in ∆F, LD and ∆Z when compared to baseline enamel, suggesting a degree of tolerance to behavioural differences between individuals. When observing the effects of different anti-erosive metal ion treatments in the context of this in vitro PEM pH-cycling model, all metal ions examined demonstrated significantly reduced ∆F, LD and ∆Z following a citric acid erosive challenge when compared to their non-cycled counterparts. This demonstrated the ability of PEM to facilitate the incorporation of these ions into the enamel. The effect of Titanium Tetrafluoride (TiF4) in the context of this model was of particular interest, with no visible damage from exposure to the low pH TiF4 treatments, whilst still retaining statistically significant anti-erosive effects. A retrospective study comparing counterpart Transverse Microradiography (TMR) and Non-Contact Surface Profilometry (NCSP) data noted no significant differences between TMR and NCSP data in any of the experiments examined, and good to excellent agreement in all but one experiment. Proportional bias was present in all but two experiments, which could be attributed to improper calibration of equipment or artefactual bias. These results suggest that NCSP may be a suitable, non-destructive analogue for TMR when analysing erosive lesion characteristics. The results of this thesis suggest that teeth undergo significant physicochemical changes during PEM and are particularly receptive to targeted interventions, which may provide long-lasting anti-erosive effects. Research which looks specifically at chemical changes during PEM will provide further insight