Bonding of lithium-disilicate ceramic to enamel and dentin using orthotropic fiber-reinforced composite at the interface

Abstract

Objective. To evaluate the effect of orthotropic fiber-reinforced composite (FRC) at the interface on bonding of lithium-disilicate ceramic to dentin and enamel using different adhesive systems. Material and Methods. Dentin and enamel surfaces were ground occlusally on human molar teeth. Ceramic blocks of IPS Empress 2 (Ivoclar-Vivadent) were fabricated. Following acid etching and silane treatment of the ceramics, the teeth were divided into two groups (dentin and enamel). Ceramic blocks were bonded to the tooth substance with or without a layer of FRC and dual-polymerizing composite cement (Duolink). Total-etching (etchant (Etch 37) with adhesive (One Step Plus)) and self-etching (self-priming etchant (Tyrian SPE) with adhesive (One Step Plus)) systems were used, with five test specimens in each group. The cement was polymerized with a LED curing unit (Elipar Freelight LED 2) with standard mode of 40 s. The specimens were thermocycled for 6000 cycles and tested with the microtensile tester at a rate of 5 mm/min. Fracture mode analyses were done by light microscope and with SEM. The data were analyzed using three-way analysis of variance (ANOVA). Results. ANOVA showed that enamel had statistically significant (p<0.001) higher bond strength values than dentin. Bond strength values were significantly higher (p=0.012) with the total-etching system than with the self-etching system. The existence of FRC also had a minor effect on bond strength values (p=0.013). Conclusions. The enamel and total-etching system provided more reliable bonding than dentin and the self-etching system. Use of an FRC layer at the interface did not improve bond strength values, but instead changed fracture pattern behavior.