Phosphoric Acid/Sodium Hypochlorite Mixture as Dentin Conditioner: A New Approach

Purpose: To investigate the effect of a phosphoric acid/sodium hypochlorite (NaOCl) mixture as a dentin conditioner on shear bond strength, the resin/dentin interface, as well as the surface area and tubular diameter of dentin. Materials and Methods: Thirty human molars were prepared for shear bond strength testing. The teeth were randomly divided into five groups according to the method of dentin conditioning. In group I, dentin was conditioned with 37% phosphoric acid, in group II dentin was conditioned with 37% phosphoric acid followed by application of 5.25% NaOCl, and in groups III, IV, and V, dentin was conditioned with a phosphoric acid/NaOCl mixture for 15, 30, and 60 s, respectively. A resin-based restorative composite disk was bonded to the occlusal surface of each tooth and shear bond strength was measured in a universal testing machine. The resin/dentin interface was evaluated using a scanning electron microscope (SEM). The surface area and tubular diameter for different conditioning methods were assessed using atomic force microscopy (AFM). The data were submitted to one-way ANOVA at a significance level of 0.05 followed by the Tukey-Kramer Multiple comparisons test. Results: Group III showed the highest shear bond strength value (36 MPa), which was significantly higher than groups I and II. SEM micrographs revealed hybrid layer formation for all groups except group II. AFM results showed that groups II and V have significantly higher surface areas and dentinal tubular diameters than other groups. Conclusion: The use of a phosphoric acid/NaOCl mixture as dentin conditioner improved the bond strength of an etch-and-rinse single-bottle adhesive to dentin. Keywords: sodium hypochlorite, dentin, adhesion, AFM