Bond Strength of Self-adhesive Resin Cements to Zirconia

Objectives: This study investigated the bond strength of four auto-mixing self-adhesive cements, including one experimental resin cement, to zirconia.Methods: Pairs of disk specimens (10 mm in diameter by 3 mm in thickness, and 8 mm in diameter by 3 mm in thickness) were prepared using a dental zirconia system (Cercon, Dentsply Ceramco). Bonding surfaces of disks were polished with 600-grid silicon carbide paper and air abraded with 50 µm alumina particles. Bonding area was regulated using an adhesive tape with an opening (5 mm in diameter). Shear bond specimens were fabricated by bonding a pair of disks using one of four self-adhesive cements which included Experimental resin cement (SAC-A, Kuaray Medical), Multilink Sprint (Ivoclar Vivadent), RelyX Unicem Aplicap (3M ESPE), Maxcem (Kerr). Number of test specimen was 5 for each group. Test specimens were immersed in 37°C distilled water for 24 hours. Shear bond strength was determined before and after thermo-cycling (4°C - 60°C, 1-minute dwell time) at a crosshead speed of 1.0 mm/min. The data were statistically analyzed by two-way ANOVA and Tukey's test (a=0.05).Results: Before thermo-cycling, there was no significant difference among four cements (SAC-A : 56.3±6.7 MPa, Multilink Splint : 58.6±7.5 MPa, ReluX Unicem Aplicap : 46.2±9.3 MPa, Maxcem : 55.1±5.4 MPa ). SAC-A maintained high bond strength (57.9±4.9 MPa) after thermo-cycling, however, it was not significantly different from that of Multilink Sprint (52.4±7.8 MPa). The bond strength of RelyX Unicem Aplicap after thermo-cycling was 44.4±6.1 MPa, which was significantly lower than that of SAC-A. All the specimens bonded with Maxcem failed during thermo-cycling. Most of the specimens showed adhesive failure at the zirconia-cement interface.Conclusion: The experimental self-adhesive resin cement (SAC-A) provided excellent and clinically acceptable bonding to zirconia compared to other self-adhesive cements.