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

Purpose: To study the effect of acid etching and the application of a hydrophobic bonding resin on the microtensile bond strengths (μTBS) and marginal sealing of the 1-step self-etch adhesive Adper Easy Bond (AEB). Methods: 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% H ₃PO ₄ 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 slowspeed diamond saw under water in X and Y directions to obtain bonded sticks with a cross section of 0.8 ± 0.2 mm ² 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). Results: AEB resulted in statistically lower mean μTBS than all other groups at P< 0.05. All the remaining groups resulted in statistically similar mean μTBS. For marginal sealing, data were grouped in three statistical subsets: Groups AEB and AEB+HR resulted in statistically less silver infiltration man 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 bom the AEB and ASB adhesive layers.