Calcium Fluoride and Fluorapatite Formation in Fluoride-Calcium-Phosphate Complex Solutions
Objectives: Previous studies reported existence of stable solutions that contained high concentrations of fluoride, calcium and phosphate (FCP). The present study investigated the effects of the FCP solution composition on the nature and amount of precipitate formed when the FCP was triggered with an “activation solution” (AS). The results could assist in developing improved dentin desensitization and other remineralization treatments.
Methods: The FCP solution contained 0.6M NaF, 0.1M H3PO4, and 1M (FCP1) or 2M (FCP2) CaCl2. The “activation solution” (AS) contained 0.6M NaF and 0.1M (AS0.1) or 0.5M (AS0.5) K2HPO4. The FCP solution (0.75mL) was added to AS (0.75mL) and mixed well. The precipitate was washed with distilled water, dried, weighed, and analyzed by powder X-ray diffraction (XRD) for phase composition.
Results: The amount of precipitates form in the four groups were (1) (47.5±3.8) mg (mean ± s.d.; n=3) in AS0.1+FCP1, (2) (51.2±5.8) mg in AS0.1+FCP2, (3) (73.4±3.0) mg in AS0.5+FCP1, and (4) (79.7±4.2) mg in AS0.5+FCP2. Two-way ANOVA indicated that the amount of precipitation was affected by the phosphate concentration in the AS (p<0.05) but not the calcium concentration in the FCP (p>0.05). XRD analyses showed the phases present in the precipitates in the four groups were (1) CaF2>>>fluorapatite (FA), (2) CaF2>FA, (3) CaF2>>FA, and (4) FA≈CaF2. The higher calcium and phosphate concentrations in the combined solution in group 4 led to higher FA formation compared to CaF2.
Conclusions: The results show that large amounts of CaF2 and FA precipitation can be formed from a small volume of the FCP+AS solution, and that the relative amounts of CaF2 and FA in the precipitation are controllable. These compositions are useful for formulating more effective dentin desensitization treatments.