Thermal Dynamics of Laser-Irradiated Trilayer Bonded-Zirconia Structures

This study aims to assess the thermal dynamics of supporting structures during laser-assisted debonding of bonded yttrium-stabilized zirconia (YSZ) ceramic. We tested the hypothesis that the heat transfer to dentin analog material and composite resin resembles that of dentin. Thirty sintered YSZ (ZirCAD, Ivoclar, Schann, Liechtenstein) slabs (4 mm diameter, 1 mm thickness) were air particle abraded, followed by two coats of Monobond Plus (Ivoclar). The slabs were bonded to exposed occlusal dentin, NEMA G10 dentin analog, or composite resin cylinders using Multilink Automix (Ivoclar) dual-cured cement. The bonded YSZ specimens (n = 10/group) subjected to irradiation with an Er,Cr:YSGG laser (Waterlase MD, Biolase, Foothill Ranch, CA, USA) at 7.5 W, 25 Hz, with 50% water and air for 15 s. Heat transfer during laser irradiation was monitored with an infrared camera (Optris PI 640, Optris GmbH, Berlin, Germany) at 0.1-s intervals. Data were analyzed using one-way ANOVA, which showed no significant differences in mean temperature between zirconia and cement layers across the substrates (composite resin, G10, dentin) (p = 0.0794). These results suggest flexibility in substrate choice for future thermal dynamics studies under laser irradiation.