ELECTRON MICROSCOPIC OBSERVATIONS OF THE DIFFERENCES IN THE EFFECTS OF STANNOUS FLUORIDE AND SODIUM FLUORIDE ON DENTAL ENAMEL

¹ The Procter and Gamble Company, Miami Valley Laboratories, Cincinnati, Ohio

Electron micrographs of replicas of human enamel surfaces showed that stannous fluoride solutions produced no visible structural alteration, regardless of pH in the range 3 to 7, and of concentrations between 0.02 and 0.4 weight per cent (50-1,000 ppm fluoride).

These treated enamel surfaces showed no appreciable changes when subjected to acid buffer attack at pH 5 for 5 minutes, while an untreated surface showed extensive etching under the same conditions.

Enamel surfaces treated with sodium fluoride showed the typical formation of calcium fluoride crystals on the surface. As the pH of the solution decreased, this deposit formed more rapidly. The effects of an acid buffer on most of these surfaces were indeterminate because of the overlying layer of calcium fluoride. At pH 7, however, where the treatment times used were too short to yield a visible calcium fluoride layer, the results showed that no appreciable resistance to acid etching was imparted.

Nonfluoride stannous salts protected the enamel surface against the acid buffer action in a way which was qualitatively indistinguishable from the action of stannous fluoride, using the methods and technics described in this report.