Bonding Quality of Etch-and-Rinse Adhesives in Root Canals upon Different Pretreatments

Purpose: To evaluate the effect of ethanol-wet/hydrophobic resin bonding (EWB) in a simplified dehydration protocol with ultrasonic agitation (UA) of etch-and-rinse adhesives on the bonding quality in root canals. Materials and Methods: 56 extracted human maxillary central incisors were divided into 4 groups (n = 14) according to the procedures of bonding fiber posts in root canals: A: conventional etch-and-rinse adhesive as control (All-Bond 3, Bisco); B: EWB in a simplified dehydration protocol, ie, after 100% ethanol dehydration (30 s, 3 times), ethanol/hydrophobic resin (50% bis-GMA + TEG-DMA, 50% ethanol) was applied into the root canal as a primer, followed by applying pure co-monomer adhesive; C: EWB in a standard dehydration protocol, ie, ascending concentrations of ethanol (50%, 70%, 80%, 90%) for 30 s and 100% ethanol (30 s, 3 times) for dehydration, with the remaining procedure conducted as in group B; D: EWB in a simplified dehydration protocol under ultrasonic agitation (UA), ie, 100% ethanol under ultrasonic agitation for 30 s, ethanol/hydrophobic resin as a primer applied under UA for 60 s, followed by the application of pure co-monomer adhesive. All the specimens were cemented with Duo-Link (Bisco) and immersed in artificial saliva for 24 h or thermocycled for 10,000 times. Bond strength, failure mode, and nanoleakage were evaluated. Hybrid layer and resin tags were also observed with SEM. Data were analyzed with two-way ANOVA (bond strength) and Kruskal-Wallis analysis (nanoleakage, resin tag score) (α = 0.05). Results: Significant differences existed in bond strength (p = 0.02) and nanoleakage (p = 0.02) among groups. After 24 h and after thermocycling, group D exhibited higher bond strengths than did group B (p = 0.02 after 24 h, p = 0.03 after aging) and group A (p = 0.06 after 24 h, p = 0.04 after aging). Bond strength and nanoleakage showed no significant difference after aging (p > 0.05). There was no significant difference in resin tag scores between any of the groups, but the apical third of the roots exhibited the lowest score (p = 0.001). Conclusion: The synergistic effects of the two pretreatment strategies (EWB in a simplified dehydration protocol and UA) improved the bonding quality. UA had a positive effect on the adhesion of the etch-and-rinse adhesives, when EWB in a simplified procedure was applied into the root canal. Keywords: adhesion to dentin, adhesive bond strength, fiber post, ultrasound