Characterization of nano-silica coating of zirconia for resin-zirconia bonding

Abstract

Objective: To characterize silica-coated zirconia surfaces by silicon nitride (Si3N4) hydrolysis under alkaline condition + a thermal treatment, scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX) and atomic force spectroscopy(AFM). The new silica-coating method has the potential to significantly promote resin-zirconia bonding.

Method:

Polished zirconia was cut into specimens 10mmx5mmx5mm (Upcera, China) were immersed in 2M KOH solution and heated up to 90°C. Then, 0.6 wt% of Si3N4powder dispersion was prepared by adding it into the solution. Pretreated zirconia samples were immersed into the dispersion for 6, 24, and 48 h. Next, zirconia samples were air-dried and thermally treated at 1400°C for 2 h. As control, zirconia was silica-coated using Rocatec™ Sand Plus (110 µm silica-coated alumina). The surface morphology and surface roughness were examined by using SEM and AFM. The elemental composition of the zirconia surfaces were examined by using EDX. Surface roughness was measured using AFM.

Result:

The elemental compositions of zirconia surfaces after surface treatment by sandblasting and silica-coating by Si3N4 hydrolysis are shown in Table. The Si content increased with the immersion period. SEM and AFM micrographs showed that there were changes in the surface morphology of zirconia after surface treatments. The average surface roughness, Ra(µm), of zirconia after sandblasting and silica-coating were: polished only (0.113±0.023), silica-coated by sandblasted (0.296±0.038), silica-coated (6 h): (0.068±0.036), silica-coated (24 h): (0.088±0.055), and silica-coated (48 h) (0.102 ± 0.057).

Conclusion:

The new surface modification added significantly the Si content on zirconia and thereby might promote more durably resin-zirconia adhesion.