In vitro determination of calcium fluoride formed on enamel after topical application of amine fluoride solution of different concentrations and acidity.

After brief exposure to topical fluoride agents, fluoride is retained on the dental surface as calcium fluoride-like material. It is believed that calcium fluoride (CaF2) releases F ions in the solution phase surrounding the apatite crystals, enhancing remineralization and retarding demineralisation of dental enamel minerals. The aim of this in vitro study was to examine whether the concentration and pH of amine fluoride solution influence the amount of calcium fluoride formed by topical fluoride treatment of enamel. Surgically removed human third molars were used. The teeth were randomly divided into three main groups, with 10 teeth in each group. Each group of teeth was treated with different amine fluoride concentrations (1, 0.5 and 0.25% F). Four enamel slabs were cut from the buccal or lingual surfaces of each tooth. One slab was assigned at random from each group to one of four subgroups in order to study the effects of pH. The slabs of the three subgroups were shaken for 3 min. in an amine fluoride solution on three successive days: Subgroup 1 (pH 5.3, Subgroup 2 (pH 4.5), Subgroup 3 (pH 4.0). One subgroup of slabs served as an untreated control (Subgroup 4). The formation of calcium fluoride was analysed chemically by the method of Caslavska et al. [1975]. The amounts of calcium fluoride produced with 1 and 0.5% amine fluoride solution at the same pH did not differ significantly (P> 0.05) and were superior to 0.25% amine fluoride solution (P<0.05). It was found that the amount of calcium fluoride depended on the acidity of the solution (i.e. the lower the pH, the higher amount of calcium fluoride). These data suggest the possibility of using lower concentrations of topical fluoride (which are potentially harmful because of possible side effects) at lower pH, with the same anticaries protective effect.