The influence of blood contamination on bond strengths between dentin and an adhesive resin cement.

The objective of this study was to determine in which step of adherent surface treatments blood contamination affects the bond strength between an adhesive resin and dentin. The coronal part of bovine incisors was polished flat to expose the dentin. The specimens were randomly divided into three groups and specific surface treatments were applied to each group: (1) a self-etching primer application (SP group); (2) 38% phosphoric acid etching followed by primer (non-HC group); (3) acid etching followed by 10% sodium hypochlorite solution application and primer (HC group). The dentin surface was contaminated by human blood before or after either step of the surface treatments. The contaminated surfaces were washed with water after 30-second exposure and air-dried. A stainless-steel rod was adhered on the dentin surface with Panavia 21 after completing the surface treatment(s), and the tensile bond strength was measured. Fifteen subgroups including control groups were tested. If blood contamination occurred before collagen fibers were exposed by either phosphoric acid etching or self-etching primer application, the contamination presented almost no influence on bond strength. Blood contamination of the dentin surface where collagen fibers had been exposed decreased the bond strength. However, when the contaminated collagen fibers were dissolved or when the contamination occurred after the exposed collagen fibers were dissolved, the bond strength was maintained. The bond strength was markedly decreased when the contamination occurred after the primer application (Scheffé's Comparison, SP group: p = 0.0003, non-HC group: p < 0.0001), but was restored by reapplication of the self-etching primer. This study revealed that the effects of blood contamination on the bond strength of adhesive resin to dentin vary greatly depending on the adherent surface conditions.