Microtensile bond strengths and interfacial examination of a polyalkenoate-based 1-step adhesive

To study the effect of acid etching and the application of a hydrophobic bonding resin on the microtensile bond strengths (microTBS) and marginal sealing of the 1-step self-etch adhesive Adper Easy Bond (AEB).

Middle dentin was exposed in 30 extracted molars and randomly divided into six groups: (1) AEB applied as per manufacturer's directions; (2) as in AEB, but one coat of hydrophobic resin (HR) was applied and cured over AEB (AEB+HR); (3) etching with 35% H3PO4 for 15 seconds followed by AEB (Etch+AEB); (4) as in group Etch+AEB, but one coat of HR was applied and cured over AEB (Etch+AEB+HR); (5) Adper Single Bond Plus, the 2-step etch-&-rinse adhesive control (ASB); (6) Adper Scotchbond Multi-Purpose, the 3-step etch-&-rinse adhesive control (SBMP). Buildups 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 sticks with a cross section of 0.8 +/- 0.2 mm2 and tested to failure in tension mode at a crosshead speed of 1 mm/minute. Statistical analyses were computed using one-way ANOVA followed by Duncan's post-hoc test at P<0.05. For marginal sealing, 36 Class V preparations were restored with one of the six adhesive combinations and processed with 50% ammoniacal silver nitrate. After sectioning, specimens were observed under a backscattered FE-SEM to evaluate silver infiltration into the resin-dentin interface, which was measured in ranks (0-4) and compared with non-parametric statistical tests (P<0.05).

AEB resulted in statistically lower mean microTBS than all other groups at P0.05. All the remaining groups resulted in statistically similar mean microTBS. For marginal sealing, data were grouped in three statistical subsets: Groups AEB and AEB+HR resulted in statistically less silver infiltration than groups Etch+AEB and Etch+AEB+HR. Groups ASB and SBMP resulted in similar silver infiltration compared to Groups AEB and AEB+HR. The nanoleakage pattern consisted of agglomerates of silver deposits located predominantly in the hybrid layer, while reticular or water-tree silver deposits were observed in both the AEB and ASB adhesive layers.