Ti and Ti-alloys have good biocompatibility, appropriate mechanical properties and excellent corrosion resistance. However, the widely used Ti-6Al-4V is found to release toxic ions (Al and V) into the body, leading to undesirable long-term effects. Ti-6Al-4V has much higher elastic modulus (100 GPa) than cortical bone (20 GPa). Therefore, titanium alloys with low elastic modulus have been developed as biomaterials to minimize stress shielding. Objective: The electrochemical behavior of surface-modified and MC3T3-E1 cell-cultured Ti-30(Nb,Ta) alloys with low elastic modulus have been investigated using various electrochemical methods. Methods: Surfaces of test samples were treated as follows: 0.3μm polished; 25μm, 50μm and 125μm sandblasted. Specimen surfaces were cultured with MC3T3-E1 cells for 2 days. Average surface roughness (Ra) and morphology of specimens were determined using a surface profilometer, OM, and FE-SEM. Corrosion behavior was investigated using a potentiostat(EG&G PARSTAT 2273), and electrochemical impedance spectroscopy was performed (10 mHz to 100 kHz) in 0.9% NaCl solution at 36.5±1oC. Results: The microstructures of the Ti-30(Ta,Nb) alloys had a needle-like appearance. The Ra of polished Ti-30Ta and Ti-30Nb alloys was lower than that of the sandblasted Ti alloy. Cultured cells displayed round shapes. For polished alloy samples, cells were well-cultured on all surfaces compared to sandblasted alloy samples. In sandblasted and cell-cultured Ti-30(Nb,Ta) alloy, the pitting potential decreased and passive current density increased as Ra increased. Anodic polarization curves of cell-cultured Ti alloys showed unstable behavior in the passive region compared to non-cell-cultured alloys. From impedance tests of sandblasted and cell-cultured alloys, the polarization resistance decreased as Ra increased, whereas, Ra for cell-cultured Ti alloys increased compared to non-cell-cultured Ti alloys. Conclusions: The corrosion resistance of these alloys decreases as surface roughness increases. Cell-cultured surfaces show good corrosion resistance against chloride ion-like halides.
Journal: TechConnect Briefs
Volume: 2, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 2
Published: May 20, 2007
Pages: 744 - 747
Industry sector: Medical & Biotech