CHANGES IN MICROHARDNESS OF ENAMEL FOLLOWING TREATMENT WITH LACTATE BUFFER

¹ University of Alabama, Medical Center, Birmingham, Ala.

Human incisor teeth were exposed to 0.001 M lactate buffer at pH 5.0 and 35° C. The rate of softening of the enamel was measured by microhardness tests for exposure times up to 10 hours. A linear rate of softening was found and the softening could be measured as per cent drop of hardness per hour. Cows' teeth gave similar results but the rate of softening was somewhat greater than for human teeth.

Intact enamel surfaces were found to soften at a slower rate than ground surfaces, and the rates were closely similar for all teeth studied. The rate of softening was independent of the initial hardness. Since hard teeth took longer to soften to a given hardness, hard teeth may be considered to be more resistant than soft teeth.

Prior exposure of enamel to fluoride solution reduced the rate of softening of ground surfaces but not of intact surfaces.

The results suggest that the effects of buffers are similar to true carious attack on enamel.