Composite Resin Bonding to Bleached Enamel : Influence of concentration and duration of application of Sodium ascorbate hydrogel

The effect of different concentrations of hydrogel of sodium ascorbate on bond strength of bleached enamel for varying periods of time and the mode of failure was evaluated.Seventy enamel surfaces were obtained from 35 human extracted premolars. Specimens were divided into four groups: no bleaching (control), bleaching with carbamide peroxide gel, bleaching and application of 10% / 20% sodium ascorbate hydrogel for 30, 60, 120 min. Surfaces were bonded with a total etch bonding system and composite resin. Specimens were tested for shear bond strength. Mode of failure was determined by stereomicroscope. Data were analyzed using a two-way analysis of variance, and Scheffe's post hoc test. Sodium ascorbate hydrogel application following bleaching increased the resin-enamel bond strength and was directly proportional to its duration of application. However, there was no difference in bond strength with an increase in the concentration of sodium ascorbate hydrogel. Immediate bonding of composite resin to bleached enamel is possible after treatment with antioxidant sodium ascorbate hydrogel.