Effects of Cusp Inclination and Light-curing Time on Microshear Bond Strength of a Dual-cure, Self-adhesive Composite Cement to Zirconia

Purpose: To evaluate the effect of cusp inclination and light-curing time on the microshear bond strength (μSBS) between zirconia and a dual-cure self-adhesive composite cement and zirconia. Materials and Methods: Forty U-shaped specimens with angled surfaces, simulating different cusp inclinations (0 degrees, 20 degrees, and 30 degrees), were fabricated from zirconia blocks (Zenostar, Wieland). The specimens were randomly divided into two groups (n = 20) according to different light-curing times of the adhesive composite cements (20 s and 40 s). Three polyethylene tubes filled with a dual-curing self-adhesive composite cement (Multilink Speed, Ivoclar Vivadent) were bonded to the surfaces of each specimen with light-curing times of 20 s and 40 s. The μSBS was tested using a universal testing machine with a crosshead speed of 0.5 mm/min. Failure analysis was performed. Two-way ANOVA (cusp inclination and light-curing time) followed by two independent samples t-test were used for statistical analyses (α = 0.05). Results: The composite cement showed various bond strengths to angled zirconia surfaces (7.07 ± 1.69 to 13.91 ± 3.11 MPa). The μSBS between composite cement and 0-degree zirconia surfaces was statistically higher than that of 20- and 30-degree zirconia surfaces. The composite cement light cured for 40 s showed nonsignificantly higher μSBS than did the composite cement cured for 20 s. Adhesive failure was the most common failure mode. Conclusions: Cusp inclination affected bond strength between the dual-curing self-adhesive composite cement and zirconia. Keywords: cusp inclination, light-curing time, microshear bond strength, composite cement, zirconia