ABSTRACT
Several studies have shown a reduction in enamel bond strength when the bonding procedure is carried out immediately after vital bleaching with peroxides. The purpose of this study was to compare the effects of antioxidant agents [sodium ascorbate, sodium sulfite] and delayed bonding on shear bond strength of composite resin to enamel after bleaching with two different concentrations of carbamide peroxide. In this in-vitro study, 100 human premolars were collected and randomly divided into 10 groups. The investigation was conducted in two parts according to bleaching agent and elapsed time after bonding. In part I, bleaching wras with 35% carbamide peroxide [Opalescense Quick] for 30 minutes was performed. In part II, bleaching was performed with 15% carbamide peroxide [Opalescense Regular] for 6 days and 6 hours for each case. The teeth in both parts were divided in 5 groups: 1: No Bleaching-Bonding [control] 2: Bleaching-Bonding 3: Bleaching-Sodium ascorbate-Bonding 4: Bleaching-Sodium sulfite-Bonding 5: Bleaching-Saliva immersed [for 3 weeks]-Bonding After bonding and thermocycling [1000 cycles between 5-55°C] and 7 days of storage, shear bond strength was measured in all specimens. Groups differences were analyzed by using Kolmogrove Smirnov, one way NOVA and Sheffe tests. Statistical analysis indicated that treatment with antioxidant agents after bleaching with carbamide peroxide can cause such a compromised bonding comparable to the control group [p>0.05]. Antioxidant treatment can severely decrease the bonding strength