Remineralisation of the Incipient Enamel Lesion

The anticaries activity of the fluoride ion has been recognised for many years. The precise mechanism of action is not clear, although in recent years fluoride is thought to influence the natural remineralising properties of saliva on porous enamel. However, there is confusion as to the most effective means of delivery, and parameters such as concentration, duration and frequency of exposure to fluoride have been empirical. The primary aim of the work contained in this thesis, therefore, was to develop and validate a means by which remineralisation of early enamel lesions within the oral environment, could be quantitatively assessed. Thus, an in situ appliance was designed on which sections of enamel could be mounted and removed at intervals, for mineral content measurements to be carried out using microradiography and microdensitometry. The use of single sections, necessitating no other control tissue, made a major contribution to the sensitivity of mineral content changes assessed throughout the duration of this project. Validation of the technique showed conclusively that the artificial stagnation area had fundamental similarities to the environment of a natural contact point. The major part of the work was concerned with an assessment of remineralisation in early enamel lesions, when exposed to differing concentrations of dentifrice fluoride, when used by volunteers wearing in situ devices. The results indicated that in a small panel of dentally-orientated subjects, the maximum remineralising potential of a fluoridated dentifrice had been attained by 1000 ppmF, the lowest concentration investigated. Whilst being significantly better than the non-fluoridated placebo, in general no significant differences were detected between different fluoride concentrations. Nevertheless, in agreement with other workers, some person-to-person variation was detected, especially when analyses of the fluoridated dentifrices was performed. In an attempt to develop a laboratory test to mimic the in s itu results, an in vitro model was proposed. Whilst the model failed to detect differences in remineralising abilities of the fluoridated dentifrices, no significant differences were detected between those and the non-fluoridated placebo. In conclusion, the in situ device would appear to have successfully linked the advantages of the single section technique and the natural oral environment. Of further interest would be changes to the parameters investigated in this work: such as lowering of the fluoride content, the duration and the frequency of exposure to the fluoridated dentifrices. Further work into both the microbiological and biochemical changes in the plaque overlying the enamel lesion would be of considerable interest, as well as extending the technique to involve dentine caries, both coronal and root