Abstract
This study aimed to evaluate the effect of self-etching primer (Monobond Etch & Prime; MEP), hydrofluoric acid (HF), and air-abrasion (A) protocols on shear bond strength (SBS) of resin cement and flexural strength (FS) of nanoparticle-filled resin-based CAD/CAM material. Bar- and rectangular-shaped specimens (n = 130 for each) were obtained from a resin-based material (Cerasmart 270). The specimens were divided into 13 subgroups according to surface treatments: Control (C); HF for 60, 90, and 120 s; MEP for 60, 90, and 120 s; air-abrasion for 10, 15, and 20 s; air-abrasion followed by HF; air-abrasion followed by MEP; HF followed by MEP. Surface roughness (Ra) values were measured using a profilometer (Surftest SJ-210) by applying 9 readings per specimen. One specimen per group was examined by atomic force microscopy (AFM; Multimode 8) in a 20 μm × 20 μm area, and scanning electron microscopy (SEM; EVO LS-10) under ×1000 magnification. FS and SBS data were obtained using a universal test device (Marestek) at a crosshead speed of 1 mm/min. Air-abraded groups showed the highest Ra (A10: 1.331 ± 0.213; A15: 1.409 ± 0.110; A20: 1.491 ± 0.111; A + HF: 1.415 ± 0.138; A + MEP: 1.309 ± 0.071 μm) and the lowest FS values (A10: 122.59 ± 16.80; A15: 118.94 ± 11.74; A20: 117.22 ± 11.18; A + HF: 114.42 ± 18.09; A + MEP: 128.98 ± 19.74 MPa). FS values of HF- and/or MEP-applied groups were statistically similar to the control group (C: 167.37 ± 27.02; HF60: 186.74 ± 30.66; HF90: 162.79 ± 29.31; HF120: 184.11 ± 17.18; MEP60: 171.98 ± 29.65; MEP90: 162.49 ± 20.38; MEP120: 173.55 ± 22.50; HF + MEP: 175.09 ± 21.64 MPa). SBS values of MEP-applied groups were higher than those of HF-etched groups with the same duration. Significant differences in SBS values were found after etching protocols with different durations (HF60: 4.14 ± 0.64; HF90: 4.48 ± 0.33; HF120: 6.76 ± 1.65; MEP60: 6.24 ± 1.23; MEP90: 9.92 ± 1.25; MEP120: 10.22 ± 1.27 MPa). Prolonged MEP application (90 s and 120 s) can be the preferred surface treatment for resin-based CAD/CAM materials. However, air-abrasion may adversely affect its mechanical properties.
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