Purpose: To examine the microtensile bond strength and the micromorphology of ceramic restorations bonded to sealed dentin with different protocols.
Methods: Fifty rectangular cavities were prepared in the occlusal dentin surfaces. They were randomly divided into five groups(n=10) according to the dentin sealing protocols: Group DDS: delayed dentin sealing(control group); IDS1: immediate dentin sealing with removal of O2 inhibited layer; IDS2: same as IDS1 but with dentin finishing immediately before the final cementation; IDS3: immediate sealing without removal of O2 inhibited layer; IDS4: same as IDS3 but with final dentin finishing. Temporization was performed using a provisional material (Tempfil Inlay, Kerr) for two weeks. Lithium disilicate glass-ceramic blocks (IPS e.max Press: Ivoclar, Vivadent, Liechtenstein, Schaan) were machine milled to fit inside the prepared cavities and they were cemented in place using resin cement (Rely X Unicem, 3M ESPE). Half of the restored teeth from each group was thermocycled (SD Mechatronicks THE 100 thermocycler, Germany) 5000 cycles 5-55˚C with 30 seconds dwell time. Specimens were prepared for microtensile bond strength test and micromorphological analysis with Environmental scanning electron microscope (ESEM). Data was statistically analyzed using ANOVA and Tuckey's post hoc test(P=0.05). Bond reliability was checked using the Weibull analysis.
Results: Superior bond strength values (MPa) were evident in DDS group (30.56) and IDS2 (30.21) and the lowest value was in IDS3 (21.25). Weibull test confirmed that IDS2 revealed the most reliable bond even after thermocycling. All bond strength values decreased significantly after thermocycling. SEM results supported the bond strength findings.
Conclusions: Immediate dentin sealing with removal of oxygen inhibited layer together with finishing just before final cementation are the keys for reliable interfacial bond between the dentin and ceramic restorations.