EFFECT OF POLYMERIZATION MODE OF A DUAL-CURED RESIN CEMENT ON TIME-DEPENDENT SHEAR BOND STRENGTH TO PORCELAIN

Purpose: To evaluate the shear bond strengths to porcelain and setting times of a dual-cured resin cement with light/chemical curing (dual) or chemical only curing versus time. Materials and Methods: Variolink resin cement was bonded to specimens of etched, silanated porcelain. G roups of specimens were cured by dual cured or by chemical curing only . Shear bond strengths were recorded at 2, 3, 5, 60 minutes and 24 hou rs for dual cured and at 10, 20, 40, 50, 60 minutes and 24 hours for c hemical-cured only after mixing. Kinetic-temperature profiles of dual and chemical curing modes of cement were calculated. Results: Maximum bond strengths and time to attainment were 17.5+/-2.7 MPa at 60 minute s for chemical-cured and 26.1+/-2.3 MPa at 5 minutes for dual-cured. T he peak in the kinetic-temperature setting profiles were 14.1+/-0.9 mi nutes for chemical curing and 52.2+/-5.2 seconds for dual curing. Dual curing provided significantly higher shear bond strengths versus chem ical curing at both the 60-minute and 24-hour time periods.