Microharness and lesion depth studies of artificial caries lesions: a comparison of gelatin and HEC based systems

Microhardness measurements with the indenter load perpendicular to the artificial carious enamel surfaces can be employed to investigate lesion depth in de- and remineralization of fluoridation studies in vitro or in vivo. In this study, microhardness and lesion depth studies were made on bovine enamel subjected to demineralizing solutions on a gelatin base at pH = 4.5 and 37 degrees C. The parameters studied were load, demineralization period and dialysis of the gelatin. All experimental data are compared with lesions formed in acidified 6% HEC solutions under identical conditions. The results show that lesion formation and mechanical properties of artificially carious enamel are comparable for nonchared HEC and charged gelatin based systems. Because of the higher sensitivity, lesions formed in HEC are to be preferred for lesion depth determinations by means of microhardness indentations. Both gelatin - and HEC based systems show a lesion depth proprotional to the square root of the demineralization period. If gelatin or HEC is dialyzed first, and subsequently used in the demineralizing buffers, the results show that no subsurface lesions are formed but "acid-softening" of the enamel takes place.