Application of a preliminary light-curing unit for enhanced bonding between a gold alloy and veneering materials

PURPOSE: To evaluate the effectiveness of a preliminary light-curing unit when it was used in a procedure to bond veneering material to metal. METHODS: Two light-activated composite materials (Artglass and Cesead II) were separately placed onto gold alloy disks (Pontol LFC), and polymerized using one of the following three methods: (1) exposure with a high-intensity laboratory light-curing unit (Hyper LII) for 90 seconds; (2) exposure with a preliminary light-curing unit (Targis Quick) for 20 seconds, followed by exposure with the high-intensity unit for 90 seconds; and (3) exposure with the preliminary unit for 90 seconds, followed by exposure with the high-intensity unit for 90 seconds. Shear bond strengths were determined and compared by analysis of variance and post-hoc multiple comparison intervals. The curing depths of the two materials polymerized with the two curing units were determined using a scraping technique described by the International Organization for Standardization (ISO) 4049 with the aim of evaluating the difference in curing performance between the two units. RESULTS: The group polymerized using the preliminary unit for 90 seconds showed statistically improved bond strengths over the group polymerized without the preliminary unit (P < 0.05) regardless of the materials. Regarding the Cesead II material, both groups polymerized using the preliminary unit also indicated significantly improved bond strength compared with the group polymerized with high-intensity only. Also, curing depth results revealed that the high-intensity unit demonstrated greater curing performance than the preliminary unit for both types of materials examined.