Immediate Bonding of Universal Adhesive on Sodium Ascorbate-treated Bleached Dentin

Objectives: To access the effect of restorative protocol with sodium ascorbate on shear bond strength (SBS) of universal adhesive to intracoronal bleached dentin.
Methods: One hundred twenty bovine dentin fragments (5x5 mm) were planned, polished and randomly divided into twelve groups (n=10), according to bleaching procedure (unbleached and bleached) and restorative protocol (no treatment, 10% Sodium ascorbate (10SA), 35% Sodium ascorbate (35SA) and two-step etch-and-rinse (ER) or one-step self-etch (SE) Scotchbond universal adhesive approaches): I- unbleached + no treatment + ER, II- unbleached + no treatment + SE, III- unbleached + 10SA + ER, IV- unbleached + 10SA + SE, V- unbleached + 35SA + ER, VI- unbleached + 35SA + SE, VII- bleached + no treatment + ER, VIII- bleached + no treatment + SE, IX- bleached + 10SA + ER, X- bleached + 10SA + SE, XI- bleached + 35SA + ER, XII- bleached + 35SA + SE. Four whitening sessions were performed using 35% hydrogen peroxide. The samples from control groups were kept in relative humidity at 37ºC. Immediately after bleaching period, respective antioxidant solution was applied on dentin and bonding procedures were performed following either ER or SE approaches. Composite resin cylinders were made using a split Teflon mold. Data (MPa) were submitted to ANOVA and Tukey’s test (α=0.05).
Results: Lower SBS values were found for bleached specimens (8.54) when compared with those unbleached (12.13) (p<0.05). Groups restored without sodium ascorbate showed lower bond strength values for both ER (8.32) and SE (8.28)​​ adhesive strategies. The bond strength of the sodium ascorbate-treated groups was higher than those untreated, regardless of the strategy employed (p<0.05). The group treated with 10SA submitted to ER approach (10.14) was similar to untreated (p>0.05).
Conclusions: The bond strength of composite resin to intracoronal dentin was affected by restorative protocol and reduced by bleaching.