Dentin and enamel bond strengths of dual-cure composite luting agents used with dual-cure dental adhesives

Objective: The purpose of this in vitro study was to evaluate and compare dentin and enamel bond strengths obtained with dual-cure composite luting agents when used with dual-cure dental adhesives. Methods: Human molars were ground flat to expose enamel (n = 80) or dentin (n = 80). Specimens in each substrate group were randomly assigned to eight treatment sub-groups, according to four adhesive-luting agent combinations and two test conditions (with or without thermocycling). Pre-polymerized composite resin posts (TPH Spectrum) were luted to either the enamel or dentin surfaces with one of the following adhesive-luting agent combinations: (1) Xeno IV Dual Cure (dual-cure self-etch adhesive) and Calibra (dual-cure luting agent); (2) Prime & Bond NT Dual Cure (dual-cure total-etch adhesive) and Calibra; (3) OptiBond All-in-One Dual Cure (dual-cure self-etch adhesive) and Nexus 2 Dual Syringe (dual-cure luting agent); (4) OptiBond Solo Plus Dual Cure (dual-cure total-etch adhesive) and Nexus 2 Dual Syringe. For each treatment sub-group, half the specimens (n = 10) were tested after 24 h storage in water at 37 °C, and the other half (n = 10) were tested after thermocycling for 1800 cycles between water baths held at 5 and 55 °C, with a dwell time in each bath of 30 s, and a transfer time of 10 s. Bond strengths were measured in shear mode, and expressed in MPa. The fracture mode (adhesive, cohesive, mixed) was examined. Data were analyzed for statistical significance with a factorial ANOVA and post hoc tests. Results: Mean enamel bond strengths ranged from 8.4 MPa for non-thermocycled OptiBond All-in-One|Nexus 2 to 35.5 MPa for non-thermocycled Prime & Bond NT|Calibra. Mean dentin bond strengths ranged from 14.5 MPa for non-thermocycled OptiBond Solo Plus|Nexus 2 to 30.9 MPa for thermocycled Xeno IV|Calibra. The fracture mode was predominantly adhesive for all groups. Conclusions: On enamel, the total-etch adhesives performed better than their self-etch counterparts, while in dentin, the opposite was found, i.e., the self-etch adhesives performed better than their total-etch counterparts. Thermocycling for 1800 cycles did not affect the SBS of the materials tested to dentin and enamel.