The Effect of Surface Conditioning Methods on the Bond Strength of CAD/CAM Composite Resin with Dentine

Objective: To evaluate the effect of surface conditioning methods on the bond strength of a self-developed dental CAD/CAM composite resin material (polymethylmethacrylate/nano SiO2-ZrO2) and dentine, and to select appropriate resin cements from three resin luting agents. Methods: A total of 210 cylindrical composite resin blocks were divided into 7 groups (n = 30) and treated by 7 different surface conditions: (1) no treatment, (2) etching with phosphoric acid and application of adhesive agent, (3) silane coupling agent (S), (4) etching with hydrofluoric acid (HF) and silanisation, (5) sandblasting (Sa), (6) Sa + S, and (7) Sa + HF + S. Each group was further divided into three subgroups for application of three resin cements (RelyX ARC, Panavia F, or Variolink II) to bond the treated composite blocks and dentine. Subsequently, the shear bond strengths were measured and the failure mode examined. The composite surface treatments of 400-grit silicon carbide paper, PA, HF, Sa and Sa + HF were examined with a scanning electron microscope to determine the effect of these conditions. Results: For the same resin cement, the three sandblasting treatment groups showed the highest bond strengths except for the Sa + S and Sa group when using Variolink II. For the same surface treatment, there were no differences among the three resin cements. After sandblasting treatment, the occurrence of adhesive failures at the composite-luting cement interface was greatly reduced. Sandblasting presented the greatest topographical relief with evident irregular morphological change. Conclusion: Sandblasting treatment was the main factor responsible for improving the bond strength of indirect composite resin and dentine. Keywords: CAD/CAM, composite resin, dentine, shear bond strength, surface treatment