Influence of antioxidant treatment on bond strength to enamel after tooth bleaching

Objectives: The objective of study was evaluate the effect of 10% sodium ascorbate (SA), 10% α-tocopherol (TP), 6.5% grape seed extract (GS) on shear bond strength of adhesive resin cement to bleached enamel in different application times.



Methods: 108 human maxillary central teeth were randomly divided into 9 groups (n=12). Except control group the labial surface of all specimens in the other groups were bleached with 40% hydrogen peroxide (HP). The groups are; GC: Restored on unbleached enamel; GB: Restored immediately after bleaching; GS7d: Restored after stored in artificial saliva for 7 days; GSA15: Treated with 10%SA for 15 min; GSA60: Treated with 10%SA for 60 min; GTP15: Treated with 10% TP for 15 min; GTP60: Treated with 10% TP for 60; GGS15: Treated with 6.5% GS for 15 min; GGS60: Treated with 6.5% GS for 60 min. After conditioning with antioxidant agents indirect restorations were immediately bonded with adhesive resin cement and stored in distilled water for 24 h at 37°C before shear bond strength testing. Failure mode were determined with stereomicroscope. The data were analyzed using one-way analysis of variance, Levene and Tukey HSD tests (α<.05).
Results: There was a significant reduction in bond strength of restored teeth immediately after bleaching p<.05). GS7d and GTP60 showed comparable shear bond strength values compared with the GC (p>.05). The shear bond strength of all antioxidant groups were similar to each other (p>.05), and except for the GTP60, all of the antioxidant groups showed comparable values with the GB (p>.05). Fracture modes were predominantly of an adhesive type.
Conclusions: All the antioxidants used in the study increased the shear bond strength of bleached enamel. Among the antioxidant groups treatment with α-tocopherol for 60 min or a delay of 7 days may be best choices after bleaching to ensure successful bonding to enamel.