Fluoride and Biological Calcification I: Effect of Fluoride on Collagen-Induced In Vitro Mineralization and Demineralization Reactions.

An in vitro system employing collagen isolated from the sheep tendons to induce mineralization and demineralization reactions was used not only to study the effect of various concentrations of fluoride on the collagen-induced mineralization and demineralization reactions but also to compare their action with the inhibitors of mineralization and/or demineralization. Studies demonstrated that under physiological conditions, at lower concentrations (5 × 10-6 to 5 × 10-5 M) fluoride inhibited while at higher concentrations (> 10-4 M), it stimulated the collagen-induced in vitro mineralization. At higher concentrations, fluoride was also found to inhibit the demineralization of the collagen bound preformed mineral phase. At low concentrations, fluoride acted like Mg2+ to inhibit mineralization while at higher concentration, it acted like crystal poisons (e.g., pyrophosphate phosphonates, citrate) to inhibit demineralization. However, unlike magnesium and pyrophosphate, fluoride at its higher concentrations was found to stimulate rather than inhibit the process of mineralization.