Increases in dentin-bond strength if doubling application time of an acetone-containing one-step adhesive

This study investigated the microtensile bond strength (μTBS) of a one-step self-etching adhesive to human dentin and bovine enamel following different bonding treatments. Occlusal portions of human molars and labial surfaces of bovine incisors were ground flat to provide uniform dentin and enamel surfaces, respectively. Futurabond was used following five different protocols: 1) according to the manufacturer's directions, 2) acid etched with 36% phosphoric acid (H₃PO₄) for 15 seconds, 3) 10% sodium hypochlorite (NaOCl) treated for two minutes after H₃PO ₄-etching, 4) doubling the application time of the adhesive and 5) doubling the number of adhesive coats. Composite build-ups (6 mm in height) were constructed incrementally with Arabesk resin composite. The specimens were stored in 100% humidity for 24 hours at 37°C and sectioned into beams of 1.0 mm² cross-sectional area. Each beam was tested in tension in an Instron machine at 0.5 mm/minute, and mean μTBS data (MPa) were analyzed by one-way ANOVA and post-hoc multiple comparisons tests (α=0.05). Doubling the application time of Futurabond attained the highest μTBS to dentin; whereas, no differences among all bonding application parameters evaluated could be detected when the adhesive was applied to enamel.