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Microshear bond strength of universal adhesives to dentin used in total-etch and self-etch modes

Purpose To determine the dentin bonding ability of three new universal adhesive systems under different etching modes using microshear bond strength (μSBS). Materials and methods Futurabond U, Single Bond Universal, and Tetric N-Bond Universal were used in this study. Sixty noncarious human molars were assigned to three groups based on the type of the universal adhesives. Two etching modes (total-etch and self-etch) were employed for each adhesive group. The adhesives were applied on dentin surfaces according to the manufacturer's instructions then composite resin (Z350 XT, nanocomposite) was condensed through a polyethylene tube with a 1 mm internal diameter and 2 mm height attached firmly to dentin surfaces and light cured. All samples were thermocycled for 500 cycles from 5 to 55°C. The μSBS was measured by using universal testing machine at cross-head speed of 0.5 mm/min. The bonded surfaces were examined under a stereomicroscope at magnification ×50 to determine the mode of failure. Dentin slices were prepared for each group to evaluate the resin–dentin interface a resin composite with each adhesive were placed 2 mm thick to form composite core. The segments were sectioned longitudinally and prepared to be examined under scanning electron microscope. Results Among the universal adhesives, Futurabond U and Tetric N-Bond Universal in total-etch mode showed significantly higher μSBS values than in self-etch mode. Single Bond Universal did not show any significant difference in μSBS between the total-etch mode and self-etch mode. Conclusion Performance of universal adhesives was shown to be material-dependent. The results indicate that universal adhesives used on dentine performed better in total-etch mode than self-etch mode.