Adhesion of resin cement to dentin: effects of adhesive promoters, immediate dentin sealing strategies, and surface conditioning

Purpose: This study evaluated the shear bond strength (SBS) of resin cement to dentin after applying two adhesive (A) systems with a combination of four different immediate dentin sealing (IDS) strategies, and two surface conditioning (SC) methods. Material and methods: Human third molars (n = 140) were collected and randomly split (n = 70 each) between the two A systems (Clearfil SE Bond; Kuraray [AC] and Optibond FL; Kerr [AO]). The A groups were further divided into four IDS strategies (2 x one adhesive layer (IDS-1L); 2 x two adhesive layers (IDS-2L); 2 x one adhesive layer and one flowable layer (IDS-F); 2 x no adhesive layer (delayed dentin sealing [DDS]). Finally, each strategy group was categorized into one of the two SC methods (only pumice [SC-P] or pumice and silica coating [SC-PS]), except the DDS group, where only SC-P was used. This resulted in 14 groups of 10 specimens each. The occlusal coronal third was removed from each molar crown with a diamond saw (Isomet 1000), and IDS was applied, followed by temporary restorations. These were removed after 2 weeks of water storage, and the IDS surfaces were subsequently conditioned. The standard adhesive procedure (Syntac Primer and Adhesive, Heliobond; Ivoclar Vivadent) was executed, followed by the application of a resin cement (Variolink II; Ivoclar Vivadent) and photopolymerization. All specimens were subjected to thermocyclic aging (10,000 cycles, 5°C to 55°C). Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). Fracture types and locations after loading were classified. The data were analyzed using analysis of variance (ANOVA) and independent samples t tests. Results: AO groups exhibited higher mean SBS values (14.4 ± 6.43) than AC groups (12.85 ± 4.97) (P = 0.03). ANOVA showed the main effect of the applications on the SBS in the different groups (P = 0.00). Both DDS groups showed significantly lower SBS values compared with all the IDS groups (IDS-1L, IDS-2L, IDS-F). No significant differences in SBS results were found between the IDS groups (P = 0.43) and between the SC methods (P = 0.76). Dentin-cement interface failures diminished with the application of IDS. Conclusion: IDS improves the SBS compared with DDS. No significant differences were found between the tested conditioning methods.