The Effect Of Beyond Tooth Bleaching On The Resin-enamel Micro-tensil Strength And The Microleakage Of Resin Restoration

Objective:The purpose of this study was to investigate the effect of microtensile bond strength(uTBS) of composite resin to enamel before and after beyond tooth bleaching in differnet time;to observe the resin-enamel interface micromorphology of each group using a scanning electron microscope(SEM);to evaluate gingival microleakage of class V composite restorations.To fix the best time of composite resin restoration to tooth after beyond tooth bleaching.Method:1. using universal testing machine to test the uTBS of resin-enamel before beyond tooth bleaching and after bleaching in 1 week,2 weeks and 3 weeks to bond.2. Observing the resin-enamel bond interface micromorphology of each group using SEM.3.Using Dye penetration method to evaluate the microleakage of composite resin before beyond tooth bleaching and after bleaching in 1 week,2 weeks and 3 weeks to repair.Results:1.The uTBS of composite resin to enamel that was bonded immediately after beyond bleaching was significantly lower than that of unbleachedEnamel(P<0.05);specimens were immersed in artificial saliva for 1 week,2 weeks,3 weeks respectively,and then resin bonded,these three groups'uTBS returned to values close to those of nonbleached enamel(P>0.05);the groups immersed in artificial saliva for 2 weeks and 3 weeks,then bonded, the uTBS was significantly higher than the group that immersed in artificial saliva for 1 week bonded(P<0.05); immersed in artificial for 2 weeks and 3 weeks bonded,these two groups'uTBS have no statistically significant differences (P>0.05).2.SEM:The resin-enamel interface that was bonded immediately after beyond bleaching had gap,the adhering junction was bad.After immersing in artificial saliva for 1 week,2 weeks and 3 weeks,the resin-enamel interface is more and more densified.3. microleakage:â‘ Occlusal Margin:The margin microleakage score(MS) of resin that was repaired immediately after beyond bleaching was significantly higher than that of unbleached group(P<0.05); specimens were immersed in artificial saliva for 1 week,2 weeks,3 weeks respectively,and then resin repaired, these three groups'MS returned to values close to the control group(P>0.05); immersed in artificial saliva for 2 weeks and 3 weeks,then repaired,the MS was significantly lower than the group that repaired immediately after bleaching(P<0.05); immersed in artificial for 2 weeks and 3 weeks bonded,these two groups'MS have no statistically significant differences(P>0.05).â‘¡ingival Margin:comparison among groups,the MS have no statistically significant differences(P>0.05).â‘¢Intraclass comparison:The MS of Gingival margin was higer than the MS of Occlusal Margin in every group,the nonbleached group have no statistically significant differences(P>0.05),and the other groups have statistically significant differences(P<0.05).Conclusion:1.It is not suitable bonded to enamel immediately after beyond bleaching.2. The MS of Gingival margin is higer than the MS of Occlusal Margin before and after Beyond bleaching.3.After 1 week of Beyond bleaching,the enamel can be bonded by composite resin,but the best time is delayed 2 weeks.