COMMERCIALLY PURE TITANIUM AND TI6AL4V IMPLANTS WITH AND WITHOUT NITROGEN-ION IMPLANTATION - SURFACE CHARACTERIZATION AND QUANTITATIVE STUDIES IN RABBIT CORTICAL BONE

Nitrogen-ion implantation is a surface modification of interest for biomedical materials. In this study screw-shaped commercially pure titanium and Ti6Al4V alloy implants were nitrogen-ion implanted and analysed by scanning electron microscopy (SEM) and scanning Auger electron spectroscopy (AES). The surface topography was essentially similar for treated and non-treated samples. AES survey spectra showed an incorporation of nitrogen into the surface of the nitrogen-ion treated commercially pure titanium and Ti6Al4V implants, as judged by the ratio between the intensities of the peaks at 390 and 420 eV. AES depth profiles revealed a similar oxide thickness (7.5 nm) for the nitrogen-ion implanted and the non-treated samples. In nitrogen-ion implanted screws nitrogen was detected up to depths of about 150 nm below the surface, with a maximum nitrogen concentration at about 50 nm. Light microscopic examination of the 10 mum-thick ground sections 3 months after the insertion of nitrogen-ion implanted and non-treated commercially pure titanium and Ti6Al4V screws in the proximal tibial methaphysis of rabbits showed that bone filled a large portion of the area within the threads. A fibrous capsule was not observed. Light microscopic morphometry did not reveal any statistically significant differences in bone metal contact or bone area within the threads of nitrogen-ion treated and non-treated implants. The ''mirror-image'' analysis showed that for all implants examined significantly more bone was present immediately outside than inside the threads. The results from this study indicate that nitrogen-ion implanted, screw-shaped, commercially pure titanium and Ti6Al4V implants heal as well in cortical bone as non-treated samples.