Effect Of Arginine And Spray-Dried Chitosan Pretreatment On Microshear Bond Strength To Bleached Enamel.

Purpose: This study evaluated the effect of experimental solutions containing arginine or spray-dried chitosan on the microshear bond strength of bleached bovine enamel. Methodology: Enamel blocks (5×5×3 mm) were allocated into four groups (n=12): I) unbleached control; II) bleaching only; and bleaching followed by treatment with III) 8% arginine or IV) 2.5% spray-dried chitosan solutions for 5 min prior to adhesive procedures. Bleaching consisted of two sessions of 35% hydrogen peroxide (Whiteness HP, FGM) at a 7-day interval. Two restorations were built per block using a universal adhesive (Scothbond Universal Plus, 3M) and a nanofilled resin composite (Filtek Z350 XT, 3M). Specimens were tested for microshear bond strength (MPa), and failure mode analysis (%). Representative samples of predominant failure, as well as the arginine and chitosan powders, were evaluated by scanning electron microscopy (SEM). Results: Data were analyzed using generalized linear models, chi-square and Fisher's exact test. The unbleached group showed higher MPa values than the bleached groups, which did not differ from each other (p = 0.004). Adhesive failure was the predominant fracture pattern with no significant differences among the groups (p = 0.203). Conclusion: Treatments with arginine or spray-dried chitosan did not differ from the control bleaching group and did not reduce adhesive failures. Neither solution effectively mitigated the immediate reduction in bond strength following bleaching.