Effect of IDS Using Universal Adhesives on Monolithic Zirconia's Adhesion

Objectives: This study evaluated the effect of immediate dentin sealing (IDS) treatment using different universal adhesive systems on microtensile bond strength (μTBS) of pretreated monolithic zirconia-based CAD/CAM block to dentin.
Methods: Mid-coronal dentin surfaces were obtained from 32 intact human molars and randomly allocated into 8 groups according to types ofuniversal adhesives used for IDS treatment (Single Bond Universal/SBU, Clearfil Quick Bond/CUQ, Optibond Universal/OBU) and zirconia surface pretreatment methods (tribochemical silica coating with 30 µm CoJet particles/TSC and sandblasting with 50 μm Al₂O₃/SB): 1)Group TSC, 2)Group TSC+SBU, 3)Group TSC+CUQ, 4)Group TSC+OBU, 5)Group SB, 6)Group SB+SBU, 7)Group SB+CUQ, 8)Group SB+OBU. A monolithic zirconia-based CAD/CAM blocks(Lava Plus, 3M ESPE) were luted to the dentin surfaces with a self-adhesive dual-cure resin cement(Rely X U200,3M ESPE). They were subjected to 10.000 thermocycles and then sectioned. Zirconia-dentin bars(2x2x8 mm) were subjected to μTBS test with a universal test machine(Microtensile Tester, Bisco)(crosshead speed:0.5mm/min)(n=16). Failure types were analyzed under stereomicroscope. Surface roughness of pretreated monolithic zirconia were measured with contact profilometer. Surface morphology of zirconia and zirconia-dentin interfaces were analyzed under SEM(Evo LS10 Zeis). Semi-quantitative chemical microanalysis were performed with EDS. Two-way ANOVA and Bonferroni tests were used for statistical analyses(p<0.05).
Results: Regarding IDS treatments, Group TSC+OBU showed statistically higher μTBS than Group TSC(p<0.05). Group TSC+OBU and Group SB+OBU showed statistically higher μTBS than Group TSC+CUQ and Group SB+CUQ, respectively(p<0.05). No significant differences in μTBS and surface roughness were detected according to surface pretreatments(p>0.05). Rougher surface morphology and higher Si content were observed after tribochemical silica coating pretreatment. A thick, intact hybrid layer with long resin tags were observed for Group TSC+OBU and Group SB+OBU. The predominant failure mode was mixed for most groups.
Conclusions: After both pretreatment methods, IDS with Optibond Universal resulted in higher bond strength than the ones with Clearfil Universal Bond Quick.