Wet or dry, normal or deproteinized dentin surfaces as substrate for dentin adhesives

Bond strength between resin composite and dentin mediated by several dentin adhesives applied to dry or wet acid-etched dentin or to dry or wet acid-etched and deproteinized dentin were measured and analyzed. Human dentin were A) acid-etched and blot-dried for 1 sec (= wet), B) as A but dried with air for 10 sec (= dry), C) acid-etched and treated with hypochlorite and then dried for 1 sec, and D) as C but dried with air for 10 sec. Eight dentin adhesives were used in each group for bond strength measurements. The results were compared by means of ANOVA and the Tukey test. Collagen removal increased significantly the strength of the bond by 10-18 MPa for five adhesives when tested dry (D versus A). When tested wet, collagen removal increased the strength by 10-12 MPa for three adhesives (C versus A). Normal etched dentin showed a reduction in strength of 14-15 MPa for three or the adhesives when tested dry instead of wet (B versus A). For one dentin adhesive no significant change in bond strength due to collagen removal and/or drying conditions was observed. It was hypothesized that low technique sensitivity of an adhesive may be linked to its ability to wet and adhere to collapsed collagen fibers and to the surface of the underlying mineralized tissue. Comparisons of bond strengths obtained by using dried or wet acid-etched dentin and dried or wet acid-etched and deproteinized dentin may be useful for evaluating the efficiencies or dentin adhesives.