| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2012: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2011: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
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| Research Abstract |
This study aimed to examine the level of in vitro demineralization of human tooth enamel after bleaching using two common bleaching regimens: home-bleaching(HB), and office bleaching(OB). For the HB group, 10% carbamide peroxideHB gel was combined with artificial saliva. This mixture was applied to enamel for 2 h every day for 7 days. In between exposures, teeth were replaced in artificial saliva.For the OB group, teeth were exposed to 35% hydrogen peroxide OB agent and light curedthen maintained in artificial saliva before demineralization(OB+AS). We also included two control groups. The first was teeth that were completely untreated (Control). The secondcontrol was Light cured group (LC) that were not subjected to any bleaching but were light cured. The reduction in enamel density and the release of calcium into solution following storage of treated teeth in a demineralizing solution for 2 weeks was measured using fluorescence spectroscopy. We also visualized and quantified mineral d
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istribution in demineralized bleached enamel over time using a desktop micro-CT analyzer. HB or LC showed increased demineralization. In contrast, OB+AS was more resistant to demineralization. As mineral content and density decreases toward the dentin-enamel junction, whereas that of the enamel protein increases, this resistance todemineralization is presumably due to peroxide permeating to deeper layers of enamel before being activated by light curing, which enhances mineralization.OB+AS should be more highly mineralized and have higher resistance to acid attack. Consequently, OB＋AS were less demineralized than the other samples, even in the demineralizing solution, suggesting that the office bleaching regime exerts aprotective effect on tooth enamel. The present micro-CT evaluation revealed changes in the mineral distribution gradient in LC samples. This, concomitant with an increase in low density (i.e. less mineralized) enamel, can be permissive to severe enamel erosion in LC samples. Less
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