Acid Dissolution Rate of Sound and White-Spot Enamel Treated with Tin(II) and Fluoride Compounds

¹ Miami Valley Laboratories, Procter & Gamble Company, Cincinnati, Ohio

Dental enamel, both sound and with incipient caries-like lesions, was treated with SnF₂, SnCl₂, or NaF at 3,000 ppm Sn(II) and 950 ppm F^-. The dissolution rate of the treated enamel was measured in lactate buffer by both a differential and an integral method. Treatment with stannous fluoride reduced the dissolution rate of either sound or white-spot enamel, and the effect of this treatment was always equal to or greater than that effected by treatment with SnCl₂ or NaF under comparable conditions. Sodium fluoride treatment also reduced the enamel dissolution rate under all conditions, but SnCl₂ treatment caused an inhibition of limited duration that was eventually lost completely. Changing the acid-exposure time altered the relationship of enamel dissolution rate effects produced by the various agents, and this could lead to contradictory conclusions from solubility studies using different dissolution conditions. The results of using enamel with incipient caries-like lesions correlated more closely with human clinical investigations than did the results from sound enamel.