Evaluation of a New Universal Adhesive Using Different Bonding Strategies

Objectives: To measure the dentin/enamel microtensile bond strengths (μTBS) of a novel universal adhesive.

Methods: Dentin – 36 human molars (middle dentin) were assigned to 6 groups (n=6): (1) Group CSE – Clearfil SE Bond (Kuraray), a 2-bottle self-etch adhesive (self-etch control); (2) Group OSL – OptiBond SOLO Plus (Kerr), a 2-bottle etch&rinse adhesive applied on etched moist dentin (etch&rinse control); (3) Group OSLd - OSL applied on etched dried dentin; (4) Group SBU-SE - Scotchbond Universal Adhesive (SBU, 3M ESPE), a 1-bottle universal adhesive, applied as a self-etch adhesive; (5) Group SBU-ERm – SBU applied as an etch&rinse adhesive on etched moist dentin; (6) Group SBU-ERd - SBU applied as an etch&rinse adhesive on etched dried dentin. Enamel - 24 enamel rectangles from 12 human molars were assigned to three groups: (7) SBU-SE; (8) OSL; (9) SBU-ERm. Buildups were constructed with Filtek Z250. Specimens were sectioned with a slow-speed diamond saw to obtain bonded sticks which were tested to failure in tension mode at a crosshead speed of 1 mm/min. Statistical analyses (separate for enamel and for dentin) were computed using ANOVA followed by Duncan’s test at p<0.05.

Results: (MPa±SD, different superscript letters indicate statistical difference):

	CSE	OSL	OSL-d	SBU-SE	SBU-ERm	SBU-ERd
Dentin	47.2±22.9±c	63.0±25.0a	50.2±20.6bc	54.4±18.5b	54.0±18.8b	53.9±18.4b
Enamel	-------	41.1±17.6A	------	28.7±10.5B	40.1±17.9A	-----

Dentin – OSL resulted in significantly higher mean μTBS than those of the other five groups. All SBU groups ranked in the same statistical subset regardless of the dentin treatment. The lowest mean μTBS was obtained with CSE, but was not statistically different from that of OSLd. Enamel – OSL and SBU-ERm resulted in statistically similar mean μTBS, which were statistically higher than those of SBU-SE.

Conclusions: On dentin, SBU was not affected by the adhesion strategy or by dentin moisture. On enamel, phosphoric acid etching is still recommended.