Effects of adhesive composition on microtensile bond strength to human dentin

To evaluate the role of adhesive composition (solvent and filler content) on microtensile bond strength (muTBS) to human dentin.

15 third molars were ground to expose superficial dentin, which was polished to 600-grit. The dentin was etched for 15 s with 37.5% phosphoric acid, rinsed, and blotted with tissue paper. The surface remained visibly moist for all specimens. The following adhesives were applied to the etched dentin according to manufacturers' directions: Single Bond (SB), experimental Single Bond (with filler) (ExpSB), Prime & Bond NT (NT), experimental Prime & Bond NT (without nanofiller) (ExpNT), and One Coat Bond (with filler) (OC). Each adhesive was applied to three teeth, and a cylinder of resin-based composite was built up on the occlusal surface. After 24-hour water storage, each tooth was vertically sectioned with a low-speed saw to produce a series of 0.7 mm slabs. Each slab was then sectioned to obtain "sticks" with a cross-sectional area ranging from 0.35 to 0.45 mm2. muTBS were determined using an Instron universal testing machine. Data were analyzed using one-way ANOVA, and Duncan's test.

For filled adhesives, mean bond strengths ranged from 57.9 MPa for ExpSB to 48.2 MPa for NT. The unfilled adhesives SB and ExpNT had mean bond strengths of 75.9 MPa and 38.7 MPa, respectively. Unfilled SB had a significantly higher mean bond strength than the experimental filled version. The ethanol-based adhesive SB had a significantly higher mean bond strength than either the nonvolatile solvent-based OC or the acetone-based NT.