ANODIZED ZIRCONIUM-NIOBIUM ALLOY (ZR-2.5NB) FOR BIOMEDICAL IMPLANTS. ELECTROCHEMICAL AND BIOCOMPATIBILITY EVALUATION

The mechanical properties of zirconium and zirconium alloys render them suitable for the manufacture of biomedical implants. Controlling implant surface characteristics is essential to optimize osseointegration and limit corrosion. Among available surface treatments, anodizing is simple and easy to apply. Objectives: The aims of this study were 1) to determine the electrochemical behavior of Zr-2.5Nb anodized at 60 and 90V in simulated physiological solution (SPS), and 2) to histologically and histomorphometrically evaluate the peri-implant bone repair process around anodized implants. Methods:Zr-2.5Nb sheets anodized in H3PO4 at 60 and 90V were used. Resistance to corrosion in SPS was assessed using polarization curves. Twenty male Wistar rats were subjected to implantation of an experimental (anodized) implant in the left tibia and a control (non-anodized) implant in the contralateral tibia. At 30 days, the animals were euthanized, the tibia were resected, radiographed and processed for embedding in acrylic resin. Histological studies were performed, and the area of peri-implant bone tissue and the percentage of bone tissue-implant contact were determined histomorphometrically. Results were compared using one-factor ANOVA. Statistical significance was established at a value of p <0.05. Results: The anodized implants showed higher resistance to corrosion than controls, even after 30 days-exposure to the SPS and regardless of the anodizing potential. The histological studies showed the presence of lamellar bone tissue and absence of inflammatory response in all groups. No statistically significant differences in the area of peri-implant bone tissue were observed between groups (C: 37.792±24.704 µm2, 60V: 44.457±10.814 µm2, 90V: 38.269 ± 20.880 µm2, p>0.05). With regard to the percentage of bone tissue-implant contact, no statistically significant differences were observed (C:12%, 60V: 5%, 90V: 8%, p>0.05). Conclusions: The anodized Zr-2.5Nb alloy showed good biocompatibility and resistance to corrosion. The anodizing voltages applied in the present study did not optimize biological response. Other voltages must be analyzed in order to obtain optimal oxide thicknesses.