Shear bond strength of resin cement to a CAD/CAM millable alloy subjected to various surface treatments.

Resin cements are widely used to cement dental restorations; however, limited studies are available on the bond strength of these cements to computer-aided design/computer-aided manufacturing (CAD/CAM) base metal alloys. This study compared the shear bond strength between a self-etching resin cement (Panavia F 2.0) and a millable cobalt-chromium alloy (Ceramill Sintron) following various surface treatments. A total of 40 cylindrical alloy cores (6 mm in diameter × 8 mm in height) were milled and assigned to 1 of 5 groups for different surface treatments (n = 8): control (no surface treatment); sandblasting; metal primer; sandblasting + metal primer; or acid etching. Resin cement was then used to bond cylindrical composite resin specimens to the pretreated core surfaces. The specimens underwent a 1500-cycle thermocycling procedure and shear bond strength testing. The data were analyzed using 1-way analysis of variance, and P < 0.05 was considered statistically significant. The mean (SD) shear bond strength values in the different surface treatment groups were significantly different (P < 0.05): sandblasting, 16.59 (7.10) MPa; acid etching, 15.63 (2.94) MPa; sandblasting + metal primer, 13.28 (1.27) MPa; metal primer, 8.90 (2.08) MPa; and control, 8.86 (3.57) MPa. The mean differences in shear bond strength values were significant between the sandblasting and control groups (P = 0.003) and between the acid-etching and metal primer groups (P = 0.013). Surface roughening procedures--either sandblasting or acid etching of the alloy surface--improved the shear bond strength of resin cement to milled alloy surfaces. The use of metal primer between the alloy surface and resin cement did not significantly increase the bond strength.