Effect of a re-wetting agent on the performance of acetone-based dentin adhesives

Purpose: To compare the in vitro bond strengths of two acetone-based one-bo ttle dentin adhesives applied to four surface moisture conditions. The test ed hypothesis was that wetting a dried dentin surface with an aqueous HEMA solution would result in bond strengths similar or higher than those obtain ed by leaving the surface moist as per manufacturers' instructions. Materia ls and Methods: Eighty flat dentin bonding sites were polished to 600-grit on middle dentin of the labial surface of bovine incisors mounted in acryli c resin. The specimens were equally and randomly divided between two aceton e-based dentin adhesives (One-Step and Prime & Bond 2.1) and four different levels of surface moisture (moist dentin, dentin dried for 1 s, dentin dri ed for 5 s, and dentin dried for 5 s followed by re-wetting with Aqua-Prep, an aqueous HEMA solution). A composite post was then adapted to the treate d area and light-cured. After thermocycling, the bond strengths were determ ined by testing the specimens in shear. Field Emission SEM examinations wer e carried out to evaluate the effects of different treatments on the dentin -resin interface. Results: Statistical analysis revealed that the applicati on of One-Step resulted in similar mean shear bond strengths for the groups in which moisture was present on the dentin surface (12.0-14.2 MPa). The m ean shear bond strengths for the group in which One-Step was applied to a d ried dentin surface was significantly lower (6.0 MPa). For Prime & Bond 2.1 , the application of a re-wetting solution significantly increased mean she ar bond strengths (13.9 MPa). The remaining three Prime & Bond 2.1 groups y ielded statistically similar mean bond strengths, regardless of the surface condition (6.6-8. 1 MPa).