Comparison of effects of different surface preparation methods on the bond strength between the CAD/CAM blocks and repair composite materials

Aim: The aim of this study was to evaluate the effect of surface treatments on the shear bond strength of resin repair composites to three different CAD/CAM blocks and investigate the contribution of roughening with bur. Material and Method: In our work, 189 pieces of 3 different CAD- CAM blocks were used, 63 pieces in each group and with dimensions of 2 mm thickness. The tested materials were divided into nine subgroups according to the surface treatment technique (control, sandblasting, Cojet, HF acid, phosphoric acid, bur+ sandblasting, bur+ Cojet, bur+ HF acid, bur+ phosphoric acid). Silane + bond + composite resin was applied to all sample surfaces after the thermal cycle process was applied. Then specimens were subjected to universal testing machine for shear bond strength test. Failure modes were examined using a stereomicroscope and SEM. The data were analyzed with Mann Whitney U, Kruskal Wallis and post-hoc tests. Results: In terms of bond strength, a significant relationship was found between the block type and surface treatments used (p<0,001). Highest binding values were observed in HF acid samples in the Vita Enamic group and the lowest binding values were detected in control samples in the Lava Ultimate group. There is no statistically significant effect on the bonding strength of roughening with bur. (p> 0.05). There was a statistically significant difference in the bond strength between ceramic varieties (p <0.05). The highest values were found in the Vita Enamic group and the lowest values were seen in the IPS e-max ceramic type. Conclusion: The bond strength of composite resin to CAD-CAM materials is influenced by surface treatment. Roughening with bur increased the bond strength but no statistically significant difference was found. Key Words: CAD/ CAM, composite resin, repair, surface treatment, bond strength