Influence of various nanosilica coating techniques on the zirconia surface and bond strength to resin cement

BACKGROUND: Zirconia restorations have attracted considerable attention because of their favorable mechanical and esthetic properties, which meet the requirements for both anterior and posterior restorations. OBJECTIVES: This study aimed to evaluate the microshear bond strength (μSBS) between resin cement and zirconia surfaces dip-coated with nanosilica and nanozirconia suspensions of different compositions. MATERIAL AND METHODS: An extra translucent (XT) zirconia disc composed of 5 mol% yttrium-stabilized zirconia was sectioned into 66 samples and divided into 6 groups: untreated zirconia as the control group; zirconia blasted with silica-coated alumina; and zirconia dip-coated with nanosilica-nanozirconia suspensions at volume ratios of 100:0, 75:25, 50:50, and 25:75. The coated surfaces were analyzed using energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Resin cement cylinders were bonded to the treated zirconia surfaces, and μSBS testing was performed. The differences between the groups were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's post hoc test, with the significance level set at p ≤ 0.05. RESULTS: The highest μSBS was observed for the 50:50 nanosilica-nanozirconia group (51.63 ±5.56 MPa), whereas the lowest values were recorded for untreated zirconia (17.38 ±3.74 MPa). Zirconia blasted with commercially available silica-coated alumina showed μSBS of 31.00 ±6.54 MPa. CONCLUSIONS: Dip coating with nanosilica-nanozirconia suspensions appears to be a feasible method for improving resin-zirconia bonding while preserving the zirconia structure. Among the tested compositions, the 50:50 nanosilica-nanozirconia suspension produced the highest μSBS.