Abstract
The time-course changes in remineralization were examined to establish the necessary period of remineralization treatments in vitro. Enamel blocks were cut from the labial side of bovine incisors. To produce artificial caries lesions, the samples were immersed in a 0.1 M lactic acid gel at 37℃ for 3w. Subsequently, they were divided into 7 groups (n=10-12 per group). One group was not treated further after demineralization (group A). The samples in groups C-G were remineralized at 37℃ for 8 d in 20 mM HEPES buffer solutions (pH 7) containing 1.5 mM CaCl_2 and 130 mM KG with Ca/P ratios of 0.67, 1.17, 1.67, 2.17, and 2.67. The Ca/P ratios were adjusted by addition of a 0.1 M KH_2PO_4 solution. The samples in group B were exposed to a similar solution without Ca and P. To assess time-course mineral recovery, enamel surfaces were partly coated with nail varnish at days 2 and 4. Sections of about 80 μm were cut from enamel blocks and microradiographed. The lesion depth (l_d, μm) and mineral loss value (△Z, vol%・μm) were measured and the mineral uptake value (△M, vol%・μm) was calculated. The changes in the l_d, △Z, and △M values were significantly higher on days 2 and 4 (p<0.05), and lower from days 4 to 8. The △M value in each group reached 40-50% of the day 8 value by day 2 and about 85% by day 4. Regardless of the Ca/P ratios, the mineral recovery rates decreased with the remineralization period. In conclusion, it is suggested that an early period of reaction up to 4 d is optimal for examining and comparing the degree of remineralization in enamel lesions in vitro.
