Effect of argon plasma and dentin rehydration on bond strength of dental adhesives to etched dentin.

This study investigated the effects of nonthermal atmospheric pressure plasma (NAPP) application and dentin rehydration with water (REHY) on bond strength (BS) of adhesives. Three etch-and-rinse adhesives were tested: Scotchbond Multi-Purpose (SBM / water-based primer + adhesive resin), Gluma Bond Universal (GBU / single-bottle containing acetone as organic solvent) and Prime&Bond Universal (PBU / single-bottle containing propanol as organic solvent). Adhesives were applied: 1- to phosphoric acid-etched dentin (Control), 2- after NAPP application for 45 seconds to etched dentin or 3- after REHY with water (10 seconds) of plasma-treated etched dentin. BS was performed using human molars and microtensile test, in which specimens were tested after 24 hours or one year (n=6). BS data were analyzed by three-way mixed ANOVA and Bonferroni's test (α=0.05). The morphology of etched dentin (n=3) and the dentin-adhesive interfaces (n=3) were evaluated using SEM. NAPP and REHY did not increase the BS of GBU and PBU. The BS of SBM to etched dentin not treated with NAPP (Control) reduced significantly after one year. The PBU adhesive showed the highest bond strength to dentin when the adhesives tested were applied after REHY. Phosphoric acid demineralized dentin to a depth of 5 mm that allowed the adhesive penetration into the dentinal tubules, forming the resin tags. Interfacial structures were maintained after one year. Argon plasma treatment was not beneficial in increasing the dentin bond strength of adhesives to etched-dentin at 24 hours. However, rehydration after plasma application prevented the bond strength reduction for three-step adhesive after one year.