Effect of surface conditioning methods on the microtensile bond strength of repair composite to indirect restorative materials

This study evaluated the effect of surface conditioning methods on the microtensile bond strength (µTBS) of a restorative composite to indirect restorative materials. Blocks (5 × 5 × 4 mm3) (N = 72) of (a) Zirconia (In-Ceram Zirconia, Vita) (ZR), (b) lithium disilicate glass ceramic (IPS Empress II, Ivoclar Vivadent) (LD), (c) Indirect resin composite (Gradia, GC) (GR) were fabricated (n = 24 per group) and divided randomly into three groups: 1-Control: no conditioning, 2-Silane coupling agent, 3-Hydrofluoric acid (9.5%) (HF)+silane. Each block was duplicated in resin composite. The adhesion surfaces were conditioned with airborne-particle abrasion (110 µm Al2O3 particles). Half of the conditioned blocks received no bonding and the other half one coat of bonding (ED Primer II, Kuraray). Each conditioned block was bonded to a composite block with a resin luting agent (Panavia F2.0, Kuraray). The blocks were sectioned into 1 mm2 microsticks and tested for microtensile bond strength (µTBS) (0.5 mm/min) in a μTBS testing machine. Failure types were evaluated under stereomicroscope and Scanning Electron Microscope (SEM). Data were analyzed using three-way ANOVA, Bonferroni corrected and independent sample t-tests (p < 0.05). Significant effect of the bonding (p < 0.001) and surface conditioning (p < 0.001) were observed in all groups. The highest mean bond strength values were obtained in the bonded, HF etched and silanized groups of ZR, LD and GR (12.4 ± 2.9, 28.1 ± 1.5 and 27.2 ± 2 MPa, respectively). HF acid + silane increased the repair bond values in all materials. Majority of the failure types were adhesive for ZR group, whereas HF + silane conditioned LD and GR groups presented predominantly cohesive failures in the cement.