Changes of Enamel Demineralization by Lactic and Formic Acid and/or those of a Mixture

Abstract

The effects of lactic acid, which has often been invoked as a major plaque metabolite, the effects of formic acid, whose pKa is lower and supplies hydrogen ions at a high rate, and the effects of a mixture of both acids at different ratios on early enamel caries lesions was studied using a sandwitch technique. Enamel samples of a thickness of 100μm were prepared and exposed to five types of solutions containing lactic acid alone, lactic acid and formic acid mixed at the ratios of 3 : 1, 1 : 1, and 1 : 3, and formic acid alone. These solutions were adjusted to pH 4.5 and final acid concentration was adjusted to 0.1M. Every 3 to 24hours, microradiographs of each sample were taken. The change of mineral content with the passage of time showed that there was a decreasing tendency towared maximum mineral content of the surface layer(Max.) and minimum mineral content of the lesion (Min.). There was a increasing tendency toward lesion depth (Ld) and mineral loss(⊿Z). These findings suggest that the demineralization of enamel was affected by the mixture of organic acids.