Long-term Evaluation of Dentin Bonding Properties of the Photoinitiator System Contained in Universal Adhesives Used in Fiber-Post Luting Procedures

This study evaluated the long-term push-out bond strength (PBS) and nanoleakage (NL) of universal adhesives with different photo-initiator systems in the root canals of teeth in which fiber posts were luted. One-hundred twenty endodontically treated human premolars were randomly divided into 12 groups based on the following factors: adhesives (Scotchbond Universal [SBU], Ambar Universal [AMB], and Ambar Universal APS [AMB-APS]); adhesive strategy (etch-and-rinse and self-etch), and time of testing (immediately vs after 2 years). The posts were cemented, sectioned into slices, tested for PBS at 0.5 mm/min, and examined for NL using scanning electron microscopy immediately thereafter or after 2 years of water storage. Data were evaluated using a four-way ANOVA (root thirds vs time vs universal adhesive vs adhesive strategies) and Tukey's test (α = 5%). For both evaluation times, AMB-APS demonstrated no significant difference in the PBS or NL when different radicular thirds were compared (p > 0.05). However, for SBU and AMB, the cervical third demonstrated higher PBS and lower NL than those of the apical third at both time points (p < 0.0001). AMB-APS exhibited higher PBS and lower NL in the apical third in comparison with SBU and AMB (p < 0.0001). SBU and AMB displayed a significant decrease in the PBS and increased NL after 2 years (p < 0.0001), whereas AMB-APS demonstrated no significant signs of degradation even after 2 years of water storage (p > 0.05). Independent of the root third evaluated, the universal adhesive containing APS photo-initiator system demonstrated bonding stability at the adhesive interface between the root canal and fiber posts, even after 2 years of water storage.