The Effect Of Antioxidants On The Immediate Restoration Of Porcelain Veneers After Tooth Bleaching

Background and objective:Last few years,The demand for the aesthetics of the fore-teeth is increasing.Many patients with teeth severe discoloration can be encountered in clinical.Tooth bleaching combined with porcelain veneers can be a appropriate treatment.The CAD/CAM technology can complete the treatment at one time,reduce the waiting time and the number of follow-up visits of patients.But studies have found that bleaching could significantly decrease the immediate bond strengh between tooth and composite resin,and could increase the microleakage at the edge of restoration.Recently,many researches confirmed that antioxidants can improve the adverse bonding performance of immediate resin restoration after bleaching.effects of bleaching on bonding.Sodium ascorbate is an antioxidant that has been proven effective by most studies and is believed to be used as a standard to compare the effects of other antioxidants,but its optimal clinical use time is still controversial.Proanthocyanidin is a natural strong antioxidant.Its antioxidant capacity is 50 times that of SA,and it has good biocompatibility and almost no side effects.Although some studies have confirmed its ability to improve bonding strength after bleaching,the number of studies is small and the results of the studies are inconsistent.Whether the immediate CAD/CAM porcelain veneer restoration after the teeth bleaching and treated with antioxidants can meet the clinical needs is a question remains to be solved.The functional evaluation of porcelain veneer repairment mainly includes two aspects: fracture resistance and microleakage.However,most of the research conducted experiments by making tooth specimens.There is still no research on the fracture resistance and microleakage of immediate porcelain veneers repaired after bleaching.Based on the above question,this experiment evaluated the effect of bleaching on the immediate repair of porcelain veneers,and studied the effect of SA and PC on immediate porcelain veneers restoration after bleaching,compared the effects of two antioxidants and observed the optimal time through fracture resistance test and microleakage test.In order to provide clinical guidance for the future aesthetic restoration of anterior teeth.Methods:The experiment were divided into 2 control groups(unbleached group,bleached group),into 2 experimental groups(10%SA,5%PC),The experimental group were divided into 3 subgroups(30min,60 min,120min).176 maxillary central incisors extracted in the past 3 months were collected.Porcelain veneers was repaired according to the groups.The electronic universal testing machine was used to carry out the fracture resistance,record the maximum load of fracture resistance.And the failure mode was observed with a stereo microscope.Confocal Laser scanning microscope was used to observe the bonding interface of enamel-bonding agent.A stereo microscope was used to observe the microleakage and the microleakage scores were recorded.Statistical analysis of the data was performed using SPSS.Result:1、Bleaching reduced the fracture resistance load of immediate porcelain veneer repair.SA and PC can increase the fracture resistance load of the tooth with porcelain veneer.The effects of the two antioxidants were similar and increased with time.2、The use of bleaching and antioxidants had no significant effect on the fracture resistance modes.3、Laser confocal microscopy observed the bonding interface found that tooth bleaching had an effect on the bonding interface and the formation of resin protrusions,and antioxidants could improve.4、Bleaching and antioxidants had no obvious effect on the microleakage of the porcelain veneer.Conclusion:1、Bleaching reduced the fracture resistance of immediate porcelain veneer repair.2、Two antioxidants could increase the fracture resistance of the porcelain veneer,the effect of antioxidants increased with time.The use of two antioxidants for30 minutes could meet the clinical needs,and for 120 minutes could be similar to the unbleached group.And the effect of the two antioxidants were similar,PC could be an alternative to SA.3、Antioxidants could improve the microscopic morphology of the enamel-resin bonding agent interface after bleaching,and the improvement effect increased with the application time.4、Bleaching and antioxidants had no obvious effect on the microleakage of the porcelain veneer.