Effect of Sodium-Ascorbate on Microtensile Bond Strength of Bleached Dentin

Objective: to assess the effect of 35% sodium ascorbate (SA) (Sigma-Aldrich Co.) on microtensile bond strength of dentin immediately after bleaching with 35% hydrogen peroxide (Pola Office/SDI). Methods: twenty-five sound human 3^rd molars were collected in order to obtain one hundred twenty five specimens. Teeth were randomly divided into five groups (n=5): Grp1 (bleaching + immediate restoration), Grp2 (bleaching + delayed restoration), Grp3 (bleaching + SA + immediate restoration), Grp4 (bleaching + SA + delayed restoration), Grp5 (Control-no treatment). After bleaching, but prior to restoration, Grps 2 & 4 were stored for 1 week in deionized water at 37°C. All samples were restored using Optibond Solo Plus (Kerr) and Filtek Z250 (3M/Espe) following manufacturers’ instructions. Teeth were sectioned into 1x1x8mm bars and microtensile bond strength was measured with a universal testing machine (Instron 8841) at a crosshead speed of 1.0mm/min. Results: a one-way ANOVA was used to test for differences among groups. Grp5 (control) showed significantly higher microtensile bond strength (37.18 ± 17.40) than Grp1 (25.83 ± 9.11), Grp2 (20.33 ± 7.06), Grp3 (26.98 ± 11.55) and Grp4 (22.48 ± 11.71). Tukey’s post-hoc comparison of the groups indicates that Grp3 exhibited slightly higher microtensile bond strength than Grp4, however this was not statistically significant. Conclusion: restorations without bleaching or SA showed the highest microtensile bond strength. Microtensile bond strength improved after the application of 35% sodium ascorbate when restoring immediately after bleaching, but it was not statistically significant when compared to the delayed restoration.