Mineral flux of surface enamel and root surfaces in acidified gelatin gels.

Gels of crude gelatin were dialyzed to eliminate fluoride, and then acidified with 75 mM lactic and 25 mM acetic acid at pH 4.2 and interfaced with enamel and root surfaces in gel-surface ratio of 0.2 ml/0.15 cm2. Enamel and root surface to gel mineral flux was reduced by initial inclusion of 0.5 and 1.0 mM fluoride with 2.5 mM calcium and 1.5 mM phosphate in gels at pH 4.2. Inclusion of 0.25 mM fluoride in the gels without added mineral ions had no effect in the first 22-day interface. The 0.25, 0.5 and 1.0 mM fluoride remarkably increased remineralization in a second 12-day interface. This indicated that the first fluoride exposure initiated formation of fluorapatites in the enamel which required a lower degree of gel saturation for enhanced remineralization in the second acid exposure. Fluoride had the same effect, but greater effectiveness on enamel than root-surface remineralization. Gels of crude gelatin may contain sufficient mineral ions to alter remineralization-demineralization of enamel and root surface.