Effect of different etching and air-abrasion protocols on flexural strength and resin cement bonding of hybrid CAD/CAM material

Aim: The aim of this study was to evaluate the effect of hydrofluoric acid (HF), self etching ceramic primer (MEP) and air-abrasion protocols on the surface roughness (Ra), flexural strength, and resin cement bonding of hybrid CAD/CAM material. Materials and Methods: A total of 130 bar-shaped and 130 rectangular-shaped specimens were obtained by cutting from a hybrid material (Cerasmart 270) using a low-speed diamond saw under water cooling. The specimens were divided into 13 subgroups according to surface treatments applied: Control (C), HF for 60 s (HF60), HF for 90 s (HF90), HF for 120 s (HF120), MEP for 60 s (MEP60), MEP for 90 s (MEP90), MEP for 120 s (MEP120), air-abrasion for 10 s (A10), air-abrasion for 15 s (A15), air-abrasion for 20 s (A20), air-abrasion followed by HF (A+HF), air-abrasion followed by MEP (A+MEP), HF followed by MEP (HF+MEP). Ra values were measured by using a profilometer. One specimen per group was examined under atomic force microscope and scanning electron microscope. Flexural strength and resin bond strength data were obtained by using a universal test device. Failure types were evaluated by a stereomicroscope. One-way ANOVA, Tukey's HSD, and Tamhane's T2 tests were performed for statistical analyses. Results: The highest Ra and the lowest flexural strength values were found in air-abrasion groups (P<0.05). Flexural strength values of HF and MEP groups were statistically similar to that of control group (P>0.05). Resin bond strength values of MEP groups were higher than those of HF groups treated with same durations. Significant differences in resin bond strength values were observed after etching protocols with different durations (P<0.05). Conclusion: MEP application can be a preferable surface treatment for hybrid CAD/CAM material. Air-abrasion may adversely affect the mechanical properties of the hybrid material.