Purpose: To investigate the effect of different light-curing units and adhesive systems on the bonding of leucite ceramic to dentin. Materials and Methods: Flat dentin surfaces were ground occlusally on human molars (n = 60). Hot-pressed ceramic blocks of IPS Empress (Ivoclar-Vivadent) were fabricated, air-particle abraded, and cleaned in distilled water. Following acid etching and silane treatment of ceramic, bonding procedures were performed. The teeth were divided into two groups according to the type of the adhesive system: (1) total-etch: etchant (Etch 37) and adhesive (One Step Plus); (2) self-etching: self-priming etchant (Tyrian SPE) and adhesiveOne Step Plus) (n = 30). Ceramic blocks were bonded to the dentin surfaces with dual-polymerizing resin luting cement (Duolink). For polymerization, the QTH (Blue Swan Digital, Dentanet) was used in soft-up and high-power mode, the LED (Elipar Freelight 2, 3M Espe) in exponential and standard mode, and the PAC (PlasmaStar, SP-2000, Monitex) in normal and ramp-curing mode (n = 5). Following storage in distilled water for 24 h, the samples were thermocycled for 6000 cycles. The bonded specimens were serially sectioned and trimmed to hourglass shapes with approximately 1.6 ± 0.16 mm2 cross-sectional areas, then tested with the microtensile tester at a rate of 1 mm/min. Fracture surfaces (were analyzed with SEM. The data were analyzed with three-way analysis of variance (ANOVA). Results: ANOVA revealed that adhesive systems (p < 0.001) and light-curing units (p = 0.015) had a significant effect on bond strength values. Bond strength means (± SD) in MPa were as follows: total-etch system: QTH/soft-up mode = 16.2 (5.4); QTH/high power mode = 15 (5.4); LED/standard mode = 12.1 (3.3); LED/exponential mode = 15 (5); PAC/normal mode = 19.3 (7); PAC/ramp-curing mode = 19.6 (7.4). Self-etching system: QTH/soft-up mode = 9.9 (2.1); QTH/high-power mode = 12.5 (4.3); LED/standard mode = 8.6 (2); LED/exponential mode = 13 (3.8); PAC/normal mode = 13.1 (3.9); PAC/ramp-curing mode = 8.9 (2.2). Conclusion: Results indicated that the conventional total-etch system provided more reliable bonding compared to the self-etching system. The PAC light-curing unit together with the total-etch adhesive system showed the highest mean μ-TBS values with either normal mode or ramp-curing mode.
Keywords: microtensile bond strength, leucite ceramic, light-curing units, adhesive systems.