Effect of Hydrofluoric Acid Surface Treatment of the Ceramic for CAD/CAM Crowns on the Shear Bond Strength of Self-adhesive Resin Cement

Abstract

 Purpose: This study examined the shear bond strength of self-adhesive resin cement between CAD/CAM ceramic treated with different etching times or sandblasting and the resin composite for core build-up.

 Methods: Seventy-five embedded ceramic blocks were polished using SiC#1200 papers, and were randomly assigned to five groups (n=15). The ceramic surfaces were sandblasted or etched with 9 wt% hydrofluoric acid for 0, 1.5, 5 or 30 min for each group, then the surface roughness (Ra) were measured. Disc specimens made from resin composite were adhered after priming.

 Results: Greater surface roughness was observed for the sandblasting group than the etched groups (p<0.05). The greatest bond strength was observed for the 5 min-etch group (p<0.05). The 5 min-etch group and sandblasting group had greater bond strength than the other groups (p<0.05). Significant positive correlations (r=0.450 for all etching time periods and r=0.879 for the etching time periods up to 5 min) were found between the etching time and the surface roughness. The surface roughness was found to positively correlate (p<0.05) to the bond strength (r=0.460 for all the surface roughness conditions and r=0.571 for the surface roughness obtained by etching time periods up to 5 min). Cohesive failure within the ceramic block was the dominant failure mode in the surface treated groups.

 Conclusion: The study suggested that hydrofluoric acid etching treatments achieved bond strength similar to that generally achieved by sandblasting treatment in the laboratory.