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

Zirconia restorations have attracted considerable attention because of their favorable mechanical and esthetic properties, which meet the requirements for both anterior and posterior restorations.

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.

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.

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.

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.