| Summary: | 碩士 === 國立成功大學 === 口腔醫學研究所 === 100 === Tooth bleaching is a common treatment for correcting dental esthetics. For both in-office and at-home bleaching, the primary reactive agents are hydrogen peroxide and carbamide peroxide (CP). The bleaching efficacy is based on the ability of release peroxide to penetrate the tooth structure and produce free radicals that oxidize the coloured organic molecules. During the procedures, some side effects including the tooth demineralization and sensitivity are noted. Previous studies have suggested that fluoridated bleaching agents may prevent these associated problems. However, these fluoridated bleaching agents need more evaluation on the biological aspect of their cytotoxic effects especially on pulp cells. This study was proposed to evaluate effects of fluoridated bleaching agents on the cell responses of the pulp cell.
The first experiment was to measure the diffusion of H2O2 into dental pulp during bleaching. The following four groups: Group 1, untreated controls; Group 2, treatment with 10% carbamide peroxide (CP) bleaching agent; Group 3, treatment with 10% CP containing 0.11% fluoride; Group 4, treatment with 15% CP and 0.11% fluoride. The four groups were applied on the artificial pulp chamber for 1, 2, 4, 8 h to measure the dose of hydrogen peroxide penetrating though enamel-dentin or sole dentin. Additionally, 35% CP containing 0.11% fluoride (group 5) was also applied for 30 min to simulate the in-office bleaching. The trans-enamel and dentine penetration was analyzed by HRP/OPD assay for determination of the H2O2 concentration. For sole dentin, the CP groups showed time-dependent of H2O perfusion. After 8h, G2 showed a higher concentration of H2O2 penetration (1.51 mM) than that of G3 (1.28 mM). The application of G5 for 30 min resulted in 0.28 mM of H2O2 penetration. The second experiment was to measure the cytotoxicity of fluoridated bleaching agents were evaluated on human dental pulp cells. Cell viability was evaluated by the WST-1 assay. The results showed that H2O2 induced a concentration-dependent (0-1 mM) cytotoxic effect and decreased odontoblast-related gene and protein expression treated pulp cells, while fluoride in the diffusion (0-5 ppm) was not significantly cytotoxic. Moreover, co-incubation with 1ppm fluoride unable to enhanced the cytotoxic effects of H2O2 (0.4, 0.6, 0.8 mM) on pulp cells. The third experiment was to measure the differentiation, and mineralization functions of fluoridated bleaching agents were evaluated on human dental pulp cells. H2O2 at concentration of 0.5 mM was decreased the mRNA levels, protein levels of differentiation markers, ALP activity and mineralized nododules formation of pulpc ells. Moreover, our data also indicate that 1 ppm fluoride, when co-incubated with 0.5 mM H2O2, can promote mineralization of dental pulp cells. The fluoridated bleaching agents can reduce the penetration of active bleaching agent into the tooth structure.
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