The purpose of this study was to search for demineralizing conditions which did not cause erosion on human enamel surface. Twenty human premolar enamel surfaces were divided into two groups. In one the original enamel surface was ground down about 400μm (Group A), and in the other it was not ground (Group B). Two types of 0.1M lactic acid buffer, pH4.5 and 4.0, were also prepared for demineralization. Both buffers contained 3.0mM Ca, 1.8mM P and 1.0% carboxymethylcellulose. Exposure times were 6, 12, and 18 hours for Group A, and 1 day and 1 week for Group B. The degree of demineralization was evaluated by microradiograph using calculated mineral content.
Subsurface enamel lesions were seen in Group B. The minimum mineral content in the body of lesions was 7.2% when exposed for 1 week in lactic acid buffer at pH 4.0. This showed the possibility of complete demineralization in the body of the lesions.
Softened enamel lesions were seen in Group A. Erosions of the surface enamel were observed in all cases at pH 4.0 and after 18 hours demineralization at pH 4.5. These results indicated that the demineralizing conditions without erosion were less than 12 hours exposure at pH 4.5.
