| PURPOSE: To investigate the effects of 10% sodium ascorbate, 10% sodium ascorbate combined with a surfactan（Tween，0.2%） on the microleakage of composite resin restorations after external tooth bleaching with 10% carbamide peroxide. METHODS: Fifty extracted human premolars, intact and health, were randomly divided into five groups：group 1 ,direct composite resin filling without bleaching; group 2 ,composite resin filling immediately after bleaching with 10% carbamide peroxide ; group 3 ,immersed in artificial saliva three weeks after bleaching ,then composite resin filling; group 4 ,cavity treated with 10% sodium ascorbate after bleaching and then composite resin filling; group 5 ,cavity treated with 10% sodium ascorbate combined with 0.2% Tween after bleaching and then composite resin filling. After 2000 thermal cycles, teeth were immersed in 2% methylene blue for 24 hours,then the microleakage of interface of restorations was observed under stereomicroscope. RESULTS:Group 1 displayed the least amount of microleakage, while group 2 showed the greatest amount of microleakage, group 3 and group 4 behaved similarly as group 2, having great amount of microleakage, showing no significant difference(P>0.05); the microleakage of group 5 decreased significantly (P< 0.05) compared to group 2 and group 4. CONCLUSION: The microleakage increased significantly after external bleaching with 10% carbamide peroxide, then decreased if cavities treated with 10% sodium ascorbate combined with 0.2% Tween, but delay filling and treated with sodium ascorbate only perform badly. |