Time of Application of Sodium Ascorbate on Bonding to Bleached Dentin

This study examined the effects of different application times of sodium ascorbate (SA) on the bond strength of composite resinto bleached dentin. Specimens with an exposed dentin surface were divided into 3 groups according to the type of bleaching agentused: Group A, mixture of sodium perborate (SP) and distilled water (DW); Group B, mixture of SP and hydrogen peroxide (HP);control group, no bleaching. Each group was classified into 10 subgroups. Subgroups IB and DB underwent immediate bonding anddelayed bonding, respectively. 10% SA was applied to 3, 5, 10, and 30 minutes and 1, 24, 48, and 72 hours, respectively. Microtensilebond strength (𝜇TBS) was measured after restoration, and the data was analyzed by one-way ANOVA and Scheff ́e’s test. Beforerestoration, the dentin surfaces were examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy(EDS). SEM showed that most dentin surfaces were filled with crystals when SA was applied to more than 24 hours. EDS revealedpeaks of calcium, carbon, oxygen, and sodium. The application of SA for 5 minutes to 48 hours or for 30 minutes to 24 hours issuggestedwhenamixtureofSPandDWorHPisused,respectively.