Osteoconductivity of Hydrophilic Surfaces of Zr-9Nb-3Sn Alloy with Hydrothermal Treatment

Abstract

Zirconium and its alloys are more suitable materials for implant surgery to be performed in a magnetic resonance imaging scanner compared with other implant materials. Although they have high anticorrosion properties in the body, as do titanium and its alloys, they have little use as implants in contact with bone because of their low osteoconductivity (bone-implant contact ratio). To improve the osteoconductivity of zirconium, niobium, and Zr-9Nb-3Sn alloy, we applied a single- step hydrothermal surface treatment using distilled water at a temperature of 180°C for 3 h. The hydrothermally treated samples were stored in a ×5 phosphate-buffered saline (PBS(-)) solution to keep or to improve the water contact angle (WCA), which has a strongly positive effect on osteoconductivity. The specimen surfaces were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, surface roughness, and contact angle measurement using a 2 μL droplet of distilled water. The relationship between WCA and osteoconductivity for various surface modifications was examined using in vivo tests. The results showed that a superhydrophilic surface with a WCA ≤ 10 ° and a high osteoconductivity of up to 40% in cortical bone, about four times higher than the as-polished Zr-9Nb-3Sn and its pure alloy elements, was provided by the combination of hydrothermal surface treatment and storage in ×5 PBS(-).