Shear Bond Strength of a Leucite-Reinforced Glass Ceramic to Enamel

Objective: To determine the bond strength of a leucite-reinforced glass ceramic to enamel using a resin cement in either a dual- or light-cured mode. Methods: Ingots of Empress Esthetic (Ivoclar) were pressed into samples using an 8-gauge sprue as a pattern. To simulate a ceramic veneer, the resulting cylinders were sliced into buttons 1.3+/- 0.1 mm thick with a diameter of 3.18 +/- 0.05 mm (Isomet, Buehler). Each button was treated with 5% hydrofluoric acid and a silane coupling agent. Twenty extracted human molars were mounted in dental stone in PVC pipe. Two groups of 10 teeth each (N=10) were prepared with a sanding disk to yield a flat enamel surface on the mesial or distal surface and “freshened” with 600 grit sandpaper. Optibond Solo Plus and Nexus 2 (Kerr) were applied following the manufacturer's instructions in either its light-cured (base only) or dual-cured (base and catalyst) mode. Both groups of specimens were photopolymerized with a LED curing light (Bluephase 16i, Ivoclar) for 40 seconds. The samples were loaded perpendicularly in a universal testing machine (Instron) at a crosshead speed of 1.0 mm/min until bonding failure occurred. A mean shear bond strength (MPa) and standard deviation were determined per group. Results: Mean shear bond strengths: light-cured 18.63 ± 2.96 MPa; dual-cured 13.24 ± 4.24 MPa. An unpaired t-test disclosed a significant difference between the two groups (p=0.003). Conclusions: The strongest bond of Empress Esthetic to enamel was produced when Nexus 2 was used in a light-cure only mode (i.e., no catalyst).