Dr. Cristina GodoyAHMED HANEY ABDULRAHMAN KATIB2022-06-012022-06-01https://drepo.sdl.edu.sa/handle/20.500.14154/54348Objective: to evaluate the efficacy of 40% sodium ascorbate (SA) in restoring the shear bond strength (SBS) of enamel immediately after bleaching with 40% hydrogen peroxide. Methods: Twenty-five anterior bovine teeth were collected and tested. Teeth were divided into five different groups (n=5). Group 1 (Negative Control, restoration only); Group 2 (Bleaching + 1-week delayed bonding, Standard of Care); Group 3 (Bleaching + immediate bonding); Group 4 (Bleaching + 40% SA + 1-week delayed bonding); and Group 5 (Bleaching + 40% SA + immediate bonding). Teeth in the delayed restoration groups (2&4) were stored in deionized water at 37C, after being submitted to bleaching, following manufacturer’s instructions. Four cylindrical tubes were fabricated per tooth using Filtek Supreme Ultra Universal Composite (3M, St. Paul, MN, USA) and bonded to the enamel of bovine teeth using OptiBond FL (Kerr, Orange, CA, USA) giving a total of 100 specimens with a 3mm diameter and a 3mm height each. SBS was measured using a universal testing machine (Instron model 8841, Instron, Canton, MA), a blade was placed perpendicular at teeth/composite interface and force was applied at a crosshead speed of 0.5mm/min and then statistically analyzed (Kruskal-Wallis, Dunn’s, p<0.05). Results: There was a significant difference in SBS between groups 1,2,4 and 3,5; whereas no significant difference was found between groups 3 and 5. Conclusion: SBS did not improve after application of 40% SA in the bleaching and immediate bonding group (Group 3), however, a significant improvement was noticed in group 4 where 40% SA was applied after bleaching with a 1-week delay in bonding.en