DISSOLUTION OF VARIOUS CALCIUM-FLUORIDE PREPARATIONS IN INORGANIC SOLUTIONS AND IN STIMULATED HUMAN SALIVA

The aim of the present study was to examine the dissolution of various preparations of calcium fluoride in inorganic solutions and in human saliva. Calcium fluoride was prepared by mixing either 0.25 or 0.02 mo l/l calcium chloride with 0.5 or 0.04 mol/l sodium fluoride. After pre paration, the salts were washed in 1 mmol/l calcium chloride solution and in distilled water. A commercial product, calcium fluoride Suprapu r(R) (Merck), was used for comparison. The solubility of the salts was examined in distilled water, in a 2-mmol/l sodium phosphate solution, and in whole human saliva, produced by chewing paraffin. It was found that the calcium fluoride ion product after suspension for 1-3 h in d istilled water ranged closely around 10(-10.7) for all salts. In the p hosphate solution, the commercial product dissolved slowly, the ratio between dissolved fluoride and calcium ranged from 4 to 7, in buffered solutions approaching 2. The supernatant was not saturated by the sal t. Our two calcium fluoride salts dissolved quickly and made the phosp hate-containing solutions supersaturated with respect to fluorapatite, leading to fluorapatite formation, and because of compensating calciu m fluoride dissolution, this led to increasing fluoride concentrations in saliva of up to around 85-95 ppm. The results of this study indica te that calcium fluoride of less than Suprapur standard may dissolve q uickly in saliva, unless the dissolution is retarded by a physical bar rier, like a forming pellicle.