Shear bond strength between titanium alloys and composite resin: sandblasting versus fluoride-gel treatment

The aim of this study was to investigate the effect of fluoride gel treatment on the bond strength between titanium alloys and composite resin, and the effect of NaF solution on the bond strength of titanium alloys. Five titanium alloys and one Co-Cr-Mo alloy were tested. Surface of the alloys were treated with three different methods; SiC polishing paper (No. 2000), sandblasting (50-microm Al2O3), and commercially available acidulated phosphate fluoride gel (F-=1.23%, pH 3.0). After treatment, surfaces of alloy were analyzed by SEM/EDXA. A cylindrical gelatin capsule was filled with a light-curable composite resin. The composite resin capsule was placed on the alloy surface after the application of bonding agent, and the composite resin was light cured for 30 s in four different directions. Shear bond strength was measured with the use of an Instron. Fluoride gel did not affect the surface properties of Co-Cr-Mo alloy and Ni-Ti alloy, but other titanium alloys were strongly affected. Alloys treated with the fluoride gel showed similar bond strengths to the alloys treated with sandblasting. Shear bond strength did not show a significant difference (p<0.05) regardless of treatment time (5, 10, and 20 min) of fluoride gel. After the ultrasonic cleaning subsequent to the fluoride-gel treatment, residues of fluoride ion or any other titanium-fluoride complexes were not detected. NaF solution did not reduce the shear bond strength of titanium alloys. To enhance the bond strength of composite resin to titanium alloys, fluoride-gel treatment may be used as an alternative technique to the sandblasting treatment.