Bond Durability of Luting Cements to Lithium Disilicate Ceramic

Objectives: This study evaluated the long-term bond strength of various luting cements to lithium disilicate ceramic (IPS Empress 2, IvoclarVivadent) and the influence of the polymerization mode on bond strength. Methods: Lithium disilicate samples were pre-treated with ceramic-etching gel for 20 seconds. To silanize the ceramic, a silane-coupling agent was used for 60 seconds. Following cements were tested: 1a) PermaCem self-cured (SC) (DMG), 1b) PermaCem light-cured (LC), 2a) RelyX ARC SC (3M ESPE), 2b) RelyX ARC LC, 3a) Panavia F SC (Kuraray), 3b) Panavia F LC, 4a) Variolink II SC (IvoclarVivadent), 4b) Variolink II LC, 5a) Nexus2 SC (Kerr), 5b) Nexus2 LC, 6a) Calibra SC (DentsplyDeTrey), 6b) Calibra LC, 7a) RelyX Unicem SC (3M ESPE), and 7b) RelyX Unicem LC. Eight specimens per group were fabricated: One group was aged and tested after 150d 37°C water storage (Time I); the other group after 150d at 37°C water storage, subsequently thermal-cycled (37,500X, 5-55°C) (Time II). Shear loading tests were performed using a universal testing machine. A three-way ANOVA model and multiple pairwise comparisons (Tukey) were performed to analyze the data. Results: Significant differences (p<0.0001) were observed between the seven luting cements, the polymerization method, and the two times of measurement. Cement 7 reached overall the highest bond strength values (13.1 +/- 2.4 MPa). Cements 4, 2 and 3 followed with results of 12.5 +/- 5.4 MPa, 11.5 +/- 4.1 MPa and 11.4 +/- 3.5 MPa respectively. Light-polymerization achieving a mean value of 12.9 +/- 3.7 MPa had advantages over auto-polymerization with a mean of 9.4 +/- 2.8 MPa (p<0.0001). Time II attained lower bond strengths (9.9 +/- 3.5 MPa) compared to Time I (12.3 +/- 3.6 MPa) (p=0.0004). Conclusions: Cement 7 produced the highest bond strength to lithium disilicate ceramic. Clinically, accessible restoration margins should be cured with a polymerizing light.