Effect of Air-drying Pressure and Distance on Microtensile Bond Strength of a Self-etching Adhesive

Purpose: To investigate the effect of pressure and distance during air drying on the microtensile bond strength (µTBS) of a single-step self-etching adhesive to bovine dentin. Materials and Methods: A total of 36 bovine molars was used in this study. Twenty-seven teeth were used for µTBS testing and 9 teeth for the evaluation of the resin/dentin interface. The teeth were divided into 9 groups according to the variation in solvent evaporation pressure and the distance from the dentin surface. The adhesive was applied according to the manufacturer's instructions. The pressure was adjusted using a pressure regulator and the distance was fixed by measuring the distance from the tip of the syringe to the flat dentin surface. Each tooth was restored with a composite crown 6 mm in height and was cut to produce composite/dentin rectangular sticks with a cross-sectional area approximately 1 mm2 and 12 mm in length. The sticks were tested in tension until failure at a crosshead speed of 0.5 mm/min. The fracture pattern was evaluated using a stereomicroscope under 40X magnification. For the resin/dentin interface, the samples were gold sputtered and examined using SEM operated at 20 kV. Results: Two-way ANOVA showed that both pressure and distance from the dentin surface significantly affect the µTBS of the single-step self-etching adhesive (p = 0.001). The interaction of the two independent variables (pressure and distance from dentin surface) showed a significant difference (p = 0.001). Conclusion: On the basis of the µTBS data generated in this study, the single-step self-etching adhesive used proved to be technique sensitive. Keywords: dentin bonding agent, microtensile bond strength, resin composite