Some effects of water on dentin bonding.

OBJECTIVES

The goals 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 were bonded to these surfaces, and the shear bond strength was determined after 30 d of water storage at 37 degrees C. The conversion of bonding resins containing 0.05, 0.1, 0.2, 0.4 and 0.8 mL water per mL of bonding resin was determined with FTIR.

RESULTS

The two acetone groups gave significantly (p<0.5) higher bond strength values (sigma 30s=22.2 +/- 2.1 MPa and sigma 120s=21.5 +/- 3.2 MPa) than the two water 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 reaching that of the two acetone groups. The conversion of the bonding resin was 53.5%, which decreased to approximately 25% when 0.2 mL or more water was added per mL 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 possible explanation of these results is the ability of water to interfere with the polymerization of the resin systems.