抄録
In this study, in vitro experiments were conducted using an acid erosion model to investigate and compare changes in enamel demineralization over time in different age groups. A total of 34 human extracted teeth with no caries were used, 17 of which came from subjects in their 20s at the time of extraction and 17 from subjects in their 60s. To measure the depth and the volume of enamel demineralization, the teeth were immersed in demineralization solution (0.1 N HCl) for durations of 30 seconds, two minutes, one hour and five hours. In terms of the results, one important finding was that on the outermost layer of the enamel exposed to the acidic solution, an acid resistance layer was observed after only 30 seconds of exposure and after up to five hours of exposure. Detailed investigation of this hypermineralized layer revealed that the molar ratio for Ca/P was 1.16 ± 0.02, the width of the layer was 0.9 ± 0.2 μm, and dense depositions of large and small quadrilateral crystals were observed. Another important result is that the volume of enamel lost per second of exposure to the demineralization solution initially declined exponentially over time, with the largest rate of loss observed at 30 seconds of demineralization, after which the demineralization time increased and a tendency was seen for a state of equilibrium to be reached. Based on the results of this study using an acid erosion model, we conclude that while the demineralization solution penetrated into the interior of the enamel even after only a few seconds of exposure, minerals eluted from the crystals were confirmed to have been remineralized. In terms of age, enamel demineralization was not considerably influenced by age since no statistically significant differences in demineralization depth or volume were observed between the 20s and 60s age groups.
