PURPOSE

To evaluate the laboratory dentin and enamel microtensile bond strengths (microTBS) and interfacial ultra-morphology of a new multi-purpose dental adhesive applied under different bonding strategies.

METHODS

microTBS - 36 extracted caries-free human molars were assigned to six groups: Group CSE - Clearfil SE Bond, a 2-step self-etch adhesive (self-etch control); Group SBU-SE - Scotchbond Universal Adhesive (SBU), applied as a one-step self-etch adhesive; Group OSLm - OptiBond SOLO Plus (OSL), a 2-step etch-and-rinse adhesive applied on moist dentin (etch-and-rinse control); Group OSLd - OSL applied on air-dried dentin; Group SBU-ERm - SBU applied as a 2-step etch-and-rinse adhesive on moist dentin; Group SBU-ERd - SBU applied as a 2-step etch-and-rinse adhesive on air-dried dentin. Build-ups were constructed with Filtek Z250 and cured in three increments of 2 mm each. Specimens were sectioned with a slow-speed diamond saw under water in X and Y directions to obtain bonded beams that were tested to failure in tension at a crosshead speed of 1 mm/minute. Statistical analyses were computed using one-way ANOVA followed by post-hoc tests at P< 0.05. Ultra-morphologic evaluation - dentin-resin interfaces were prepared for each of the six groups, processed, and observed under a FESEM.

RESULTS

microTBS - OSLm resulted in significantly higher mean microTBS (63.0 MPa) than the other five groups. All SBU groups ranked in the same statistical subset regardless of the dentin treatment. The lowest mean microTBS were obtained with CSE (47.2 MPa) and OSLd (50.2 MPa), which were ranked in the same statistical subset. Ultramorphologic evaluation - The two self-etch adhesives resulted in a similar ultra-morphology. Dried dentin did not preclude the formation of a hybrid layer with SBU-ERd, as opposed to OSLd.