Collagen removal and tubular occlusion influence on dentin bond strength

Objectives: to evaluate the effect of NaOCl and an oxalate desensitizer (BisBlock, BB, Bisco), applied after acid etching, on dentin bond strength. Methods: Sixteen human molars were transversally sectioned and dentin surfaces were ground flat on a #180-grit sandpaper. Specimens were divided in 4 groups, receiving the following treatments: AO, acid etching (Uni-etch, Bisco, 15 sec); AHO, acid etching and collagen removal (10% NaOCl, 1min); ABO, acid etching and tubular occlusion (BB, 30 sec); ABHO, acid etching, tubular occlusion and collagen removal. All groups were restored with One Step Plus (Bisco) and AElite All-purpose Body (Bisco) according to manufacturer's instructions. The restored teeth were sectioned for microtensile bond strength test into rectangular beams of approximately 0.8mm² of transversal section area. Tensile strength was performed by an Instron 4444 universal testing machine. Results: Bond strength values expressed in MPa (±SD) were: AO=42.61±14.84b; AHO=53.49±16.81a; ABO=39.83±15.82b; ABHO=49.29±15.38ab (ANOVA / Tukey p=0.05). Conclusions: It is concluded that tubular occlusion with BisBlock does not affect dentin bond strength. Collagen removal, when not associated to tubular occlusion, may increase bond strength for the tested adhesive.