Effects of subsequent remineralization on bovine dentin after simulated internal bleaching treatment

• Main Authors: Min-Yi Sung, 宋旻怡
• Other Authors: Shyh-Yuan Lee
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/02046427454690913685

碩士 === 國立陽明大學 === 臨床牙醫學研究所 === 96 === The purposes of this experiment were to evaluate the effects of different internal bleaching agents and subsequent remineralization treatment on dentin. Selected bovine teeth were embedded, sectioned, flattened and ground with series sand papers to get 2 kinds of specimens, including proximal dentinal blocks and central dentine slabs. The former dentinal blocks were randomly divided into four groups: (1) control group treated with distilled water, (2) with 30% hydrogen peroxide, (3) with sodium perborate tetrahydrate mixed with 30% H2O2, and (4) with sodium perborate tetrahydrate mixed with distilled water. After a period of 28 days bleaching treatment, all specimens received 14 days remineralization therapy. The bleaching and remineralization agents were changed at 7 days interval, and the CIELab color parameters, Vickers microhardness were measured prior to the experiment and seven days after each treatment. The results were analyzed with a two-way repeat measurement ANOVA and Turkey multiple comparisons (p = 0.05). Randomly selected specimens from each group were subjected to micro-Raman analysis to evaluate the organic and inorganic damages of dentin. Another set of specimens, the dentine slabs (14 x 1.3 x 1 mm), were used to verify the effects of hydrogen peroxide on dentin structure with a dual energy X-ray absorptiometry (DEXA). The mineral content and density of dentine slabs, before and after bleaching and remineralization treatments, were measured and compared with a 2-way ANOVA and multiple comparison tests (p = 0.05). Meanwhile dentin powder of a human incisor was prepared by grinding with diamond burs and used to evaluate the effect of 30% H2O2 bleaching treatment on the phosphoprotein and collagen of human dentin with SDS-PAGE analysis. The results revealed that the microhardness and mineral content of bovine dentine were significantly reduced when the specimens were subjected to 30% H2O2 treatment in group 2 (p < 0.001). The less severe reduction of microhardness was also noticed in group 3 (p < 0.001), while group 4 (sodium perborate tetrahydrate) and control group did not show significant reduction in microhardness. Remineralization treatments partially recovered the microhardness of groups 2 and 3, but had no effect on groups 1 and 4. All bleaching treatments significantly increased the brightness (L*) and decreased the yellow (b*) values of bovine dentine, while remineralization treatments did not cause significant color differences. Micro Raman analyses showed that both organic and inorganic functional groups involved in bleaching and remineralization treatments. SDS-PAGE analyses revealed that collagen protein was damaged badly rather than phosphoprotein, which could be the reason that limited the effect of dentin remineralization after bleaching. In conclusion, sodium perborate tetrahydrate mixed with distilled water is highly recommended for clinical use. When there is a need to use 30% H2O2 for in internal bleaching, it is highly recommended that subsequent remineralization should be conducted. Moreover, the roles of collagen and phosphoprotein in dentin remineralization merit further investigation.