Biocompatibility of zirconium as an alternative biomaterial for permanent implants

A.V. GOMEZ SANCHEZ; G. S. DUFFÓ; S. CERE

Rosario (Argentina)

Taller; 1º Taller de Órganos Artificiales, Biomateriales e Ingeniería de Tejidos (BIOOMAT); 2009

Universidad Nacional de Rosario

Mechanical properties and good biocompatibility of zirconium and some of its alloys made these materials suitable for biomedical applications. Although some in vivo studies have shown that zirconium and its alloys promote the osseointegration and that its citotoxicity is very low the use of this material has not been extended, and information about its performance is scarce. The good in vivo performance of zirconium is mainly due to the presence of a protective oxide layer formed in air or in oxygenated electrolytes. This film diminishes the corrosion rate, minimizing the metal ion release to the biological media and promoting its osseointegration. Porosity control is a desired quality to enhance the facility of bone formation in contact with the implant. Although zirconium has a thermodynamic tendency to form an adherent ZrO2 surface film in air atmosphere, the films are very thin, with thicknesses between 2 and 5 nm. Porosity can be improved increasing the film thickness, having the additional advantage of enhancing its barrier effect. The oxide film can be thickened by means of anodizing, or thermal treatments. Since the implant surface plays a key role in the living tissue response, the surface characterization of materials employed in orthopaedic surgery is a topic of concern. An extensive and systematic study of the influence of surface characteristics on the biocompatibility of zirconium in vivo and in vitro is required if this material is proposed as an alternative to titanium alloys in permanent implants. With this aim, this first part of the study is devoted to the electrochemical and surface characterization of zirconium surface film in vitro, in the “as received” material and after various surface modification processes as anodic oxidation or electrochemical deposition in comparison with commercially pure titanium. The characterization techniques include scanning electron microscopy with X-ray microanalysis, atomic force microscopy, X-ray photoelectron spectroscopy, polarization curves and electrochemical impedance spectroscopy. Finally, the bioactivity zirconium with different surface finishing are studied by means of apatite formation tests in a simulated body fluid solution (SBF).