Comparison of various methods of restoring adhesion to recently bleached enamel

Abstract

Aim: This study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel.

Methods: Seventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined.

Results: ANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher's exact test revealed a significant difference in failure modes among the groups (P = 0.047).

Conclusions: The three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

Keywords: Antioxidants; Ascorbic acid; Composite resins; Curing light; Enamel; Polymerization; Shear strength; Tooth bleaching.

Fig. 1

Comparison of micro-shear bond strength (µSBS) values (MPa) among the study groups (Group 1: Unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: 10% sodium ascorbate solution; Group 4: Removal of bleached enamel; Group 5: Increased curing time of the bonding agent)