No abstract

In this study fluoride was added to an artificial caries system in vitro. Both the fluoride concentration and the pH of the gel system had an effect on subsequent lesion formation. At pH 4.0 the addition of fluoride to a concentration of 10 ppm did not inhibit lesion formation. Gross loss of surface tissue was noted beneath which laminated lesions were formed with histological features characteristic of remineralization deep within the lesion. However, at pH 4.5 the presence of fluoride at the same concentration (10 ppm) resulted in either partial or complete inhibition of lesion formation.

The aim of this study was to determine whether the extent of an initial artificial caries-like lesion was related to its rate of progress after two applications of APF (1.23% F) and exposure to artificial saliva during lesion formation in vitro. Treatment of small lesions (mean depth 65.7 μm) resulted in their reversal or arrest while the same treatment of larger ones (mean depth 127.4 μm) did not prevent their progress despite evidence of some remineralisation. This suggests that the caries inhibitory effect of fluoride is optimal in the small, early lesion.

A single application of APF to sound enamel before exposure to an artifical caries system in vitro had no effect on subsequent lesion formation. However, when initial lesions were treated with APF (1.23%F) and re-exposed to the artificial caries system histological changes were produced indicative of remineralization within the lesion. This suggests that topically applied fluoride may exert its maximal effect on initial lesions rather than on sound enamel.

Significantly more fluoride was found to be deposited in enamel in vitro from successive applications of acidulated phosphate fluoride (APF; 1.23% F, pH 3.1) and NaF (1.23% F, pH 7.5) than from APF alone. When the effect of these treatments to both sound enamel and initial lesions was compared using an artificial caries system, no differences were found in either histological appearance or depth between the resulting lesions. It would appear that there may be an optimal level of fluoride uptake beyond which no additional benefit is gained.