Effect of postbleaching application of an antioxidant on enamel bond strength of three different adhesives.

OBJECTIVES The aim of this study was to compare the shear bond strength (sbs) of three different adhesives on bleached enamel immediately after bleaching, bleached/delayed for 1 week, and bleached/applied antioxidizing agent. STUDY DESIGN The enamel surfaces of 144 freshly extracted incisors without any caries and restorations were flattened and divided into 12 groups. The following adhesives were investigated: Optibond FL (OFL) (three-step etch&rinse), Optibond Solo Plus (OSP) (two-step etch&rinse), Optibond All-in-One (OA) (one-step self-etch), (Kerr, Orange, USA). Unbleached enamel groups were prepared as negative controls. The remainder surfaces were bleached with 20% Opalescent PF (Ultradent, USA) 6 h/d for 5 consecutive days. Specimens were bonded immediately after bleaching, after 1 week or after using 10% sodium ascorbate gel for 6 hours. After 500 rounds of thermocycling, sbs was measured and data was analyzed with Kruskall-Wallis and Mann-Whitney U-tests ( = 0.05). RESULTS The sbs decreased for the adhesives after bleaching except for OFL. The effect of applying sodium ascorbate subsequent to bleaching was not equal for the studied adhesives. While for OFL, sbs of the sodium ascorbate group was significantly higher than the unbleached control group, for OSP, the sodium ascorbate group had no statistically significant difference with the unbleached control group and for OA, sbs was significantly lower than the unbleached control group. CONCLUSIONS Different adhesives demonstrate different degrees of reversed bond strength subsequent to applying antioxidant. It seems the method of application and the chemical composition of the adhesives could affect the antioxidant as a reducing agent.