SOME EFFECTS OF WATER ON DENTIN BONDING

Objectives. The goats of this study were to determine how: 1) the bond strengths of hydroxyethylmethacrylate (HEMA)-based dentin primers are affected by different solvents (water or acetone), 2) the application time of these primers affect the bond strength, and 3) the conversion of water contaminated bonding resins. Methods. HEMA (35%), mixed with water or acetone, was placed on moist dentin for 30 or 120 s, dried, covered with a bonding resin, and light-cured. Composite cylinders wer e bonded to these surfaces, and the shear bond strength was determined after 30 d of water storage at 37 degrees C. The conversion of bondin g resins containing 0.05, 0.1, 0.2, 0.4 and 0.8 mt water per mi of bon ding resin was determined with FTIR. Results. The two acetone groups g ave significantly (p < 0.05) higher bond strength values (sigma(30s) = 22.2 +/- 2.1 MPa and sigma(120s) = 21.5 +/- 3.2 MPa) than the two wat er groups (sigma(30s) = 7.0 +/- 3.3 MPa and sigma(120s) = 16.2 +/- 4.8 MPa). In contrast to the acetone-based primer, the water-based primer improved its bond strength with increased priming time without reachi ng that of the two acetone groups. The conversion of the bonding resin was 53.5%, which decreased to approximately 25% when 0.2 mt or more w ater was added per mt resin. Significance. Compared to acetone, water is inferior as a solvent for HEMA-based dentin primers and gives both lower bond strength and requires longer priming time than acetone. A p ossible explanation of these results is the ability of water to interf ere with the polymerization of the resin systems.