Development of Mesoporous Silica Nanocatalyst for Dental Bleaching Application

• Main Authors: Ying-Ting Tseng, 曾穎婷
• Other Authors: 李苑玲
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47197799425640350257

碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 100 === Several mesoporous silica nanoparticles (MSN) with immobilized ferric or ferrous ions via histidine have been reported as efficient catalysts for light-free tooth bleaching. However, the optimal working environment and the catalyst stability are still unclear. The purpose of this study was to investigate the effects of initial environmental pH, concentration of H2O2, and the stability of catalysts on the tooth bleaching reaction using Fe3+-histidine@Al-MSN as the catalyst, and furthermore to find out the best reacting condition for in-office power bleaching. Orange II (0.15mM) was selected as the dye used to evaluate the bleaching activity of H2O2 in test tubes and stained tooth models. The efficacy of the catalyst, Fe3+-histidine@Al-MSN, on the bleaching reaction of H2O2 with different concentrations (0, 1, 2, 4, 6, 8 and 10%) at different initial pH environments (3, 5, 7, 9 and 11) was evaluated by measuring the final pH value of environment and residual Orange II concentration after reaction. Furthermore, the used catalyst was collected and then reacted with fresh Orange II and H2O2 to investigate the stability of the catalyst. In stained tooth model, the teeth were stained with Orange II (0.15mM) solution for 72 hours, and bleached with 4% or 10% H2O2, which were catalyzed by Fe3+-histidine@Al-MSN at initial pH 7. Image analysis technique with CIE color code analysis was used to analyze the color change of bleached teeth. In test tube model, there was no obvious change of environmental pH during the reaction in the group with initial pH 3. However, the other groups with higher initial pH demonstrated a significant dropdown of environmental pH within 15 minutes after reaction and became plateau latter. The groups reacted at initial pH 3, 5, 7 and 9, in which the final pH values were between 3 and 3.5 after reaction, exhibited more Orange II degradation than the group reacted at initial pH 11, in which the final pH value was 7 and unfavorable for Fenton-like reaction. The efficacy of Fe3+-histidine@Al-MSN catalyst on bleaching reaction increased when the concentration of H2O2 increased from 0% to 4%, but presented similar when the concentration of H2O2 was over 4%. These results indicate that raising H2O2 concentration, up to 4%, may enhance the catalytic effect of Fe3+-histidine@Al-MSN , but no benefit when the concentration of H2O2 was over than 4%, because of the scavenge effect. In addition, when the reused-cycle increased, the efficiency of used catalysts declined gradually, and 4% H2O2 had most benefit for the catalyst with less decline of its catalytic effect. Consistently, with ICP-MS analysis and SEM observes, we found Fe and Al leaching out from the catalyst and aggregation of the used catalyst, which would cause the decline of the efficiency. In stained tooth model, H2O2 solution with Fe3+-histidine@Al-MSN as a catalyst showed noticeable bleaching effect. The group reacted with 4% H2O2 had similar efficiency with 10% H2O2 at initial pH 7. Due to these results, it was concluded that Fe3+-histidine@Al-MSN reacted with 4% H2O2 at initial pH 7 is the best reacting condition for developing in-office power bleaching agent.