Low fluoride concentrations : their relevance to the inhibition of dental caries

The aim of this thesis was to investigate the effects of reduced concentrations of fluoride in dentifrices on the levels of fluoride in saliva, and to examine their potential role in the inhibition of artificial carious lesions, in vitro. A preliminary experiment studied ambient salivary fluoride levels three times weekly, in twelve subjects using dentifrices with fluoride concentrations of 0, 500, 1,000 and 1,500 ppm F (as sodium fluoride) in random order, each for one month. The results showed a significant carry-over effect. Hence, a definitive experiment was designed which employed increasing concentrations of dentifrice fluoride. Here, 20 volunteers had fluoride levels measured in saliva three times weekly whilst using the aforementioned concentrations of fluoride dentifrices for one month each. In addition, ten of these volunteers had fluoride levels assayed in plasma and plaque once per week. These data provided a range of ambient salivary fluoride values of from 0.01-0.04 ppm. The results of these experiments indicate that, lower fluoride-containing dentifrices reduce the ambient level of fluoride in whole saliva, and that in vitro, these lower levels of fluoride are associated with increased demineralisation of artificial carious lesions. Moreover, the oral mucosa is a site of fluoride retention from dentifrices and mouthrinses, and contributes to the ambient salivary fluoride levels. Thus it may be partly responsible for the prolonged nature of oral fluoride clearance and it would seem logical to conclude that further clinical and laboratory research on both the formulations and delivery of lower fluoride dentifrices is required.