Enamel Fluoride Reactivity of Professional Fluoride Products Is Not Correlated With Their Total Fluoride Content.

Purpose: To assess the in vitro reactivity of professional fluoride products with tooth enamel as a function of their fluoride content. Methods: One water-based treatment and three varnishes (9,500-22,600 ppm F) were tested. Their total fluoride concentration and the concen- tration in their soluble fraction (after centrifugation to remove most insoluble material) were determined. Products were applied on sound and demineralized enamel slabs and immersed in flowing artificial saliva for 15 minutes or four hours following manufacturers' instructions. Fluoride reactivity was estimated by determining loosely bound fluoride concentration in enamel; fluoride released to the saliva was also determined. Correlations between total and soluble fluoride in the products and fluoride release to saliva and reactivity were tested using Pearson's correlation (r; α equals five percent). Results: Fluoride concentration in the products' soluble fraction (50±9 to 9,728±316 ppm F), but not their total fluoride concentration (9,713±184 to 22,558±272 ppm F), was significantly correlated with enamel fluoride reactivity (r equals 0.52 for sound enamel and r equals 0.83 for demineralized enamel; P<0.001). Similar positive correlations were found between the fluoride released to the artificial saliva and fluoride reactivity (r equals 0.59 for sound enamel; r equals 0.80 for demineralized enamel; P<0.001). Conclusion: Soluble fluoride in formulations or their ability to release fluoride are good indicators of fluoride reactivity of professional products.