CaF(2) formation: cariostatic properties and factors of enhancing the effect

Abstract

CaF(2) or a CaF(2)-like material/phosphate-contaminated CaF(2) is a major reaction product during topical treatment of dental hard tissues. Recently, evidence has suggested that CaF(2) is formed not only on surfaces but also to some extent in the enamel. The minimum concentration of fluoride required for CaF(2) formation is not well known and may depend on whether calcium is available from plaque fluid or only through dissolution of the dental hard tissue. Furthermore, surface adsorption of fluoride to crystals may cause local concentrations necessary for CaF(2) formation. It has been suggested that CaF(2) acts as a pH-controlled reservoir of fluoride. The rate-controlling factor appears to be phosphate, which controls the dissolution rate of CaF(2) at high pH. Increasing fluoride concentration, prolonging the exposure time or using a fluoride solution with low pH can increase CaF(2) formation. CaF(2) formed at low pH contains less internal phosphate which has been shown to be less soluble. This may be of clinical significance for fluoride applied topically a few times per year.