BACKGROUND: The surface oxide layer of titanium plays a decisive role in determining biocompatibility. However, there are some reports demonstrating that the natural oxide film may not be sufficiently protective in the aggressive biologic environment. PURPOSE: The goal of this study was to examine the effectiveness of a thick oxide layer on corrosion resistance in vitro and the bone formation around titanium implants in vivo. MATERIALS AND METHODS: A plasma source ion implantation (PSII) method was used to increase the thickness of the surface oxide layer. Several instruments were employed to confirm the surface properties before and after the surface modification. Potentiodynamic polarization measurements in a phosphate-buffered saline (PBS) solution were carried out to investigate corrosion resistance in vitro. Bone formation around this surface-modified specimen was examined in a rabbit model and assessed in histomorphometry. RESULTS: Improved corrosion resistance was demonstrated by the potentiodynamic polarization measurements. Light microscopic histomorphometry showed that all implants were in contact with bone and had some proportion of bone within the threads at 4 weeks; however, there were no significant differences compared with as-machined controls. CONCLUSIONS: The results indicate that in spite of improved corrosion resistance in vitro, a thick oxide layer fabricated with the PSII method does not influence early bone formation around titanium implants in vivo.
BACKGROUND: The surface oxide layer of titanium plays a decisive role in determining biocompatibility. However, there are some reports demonstrating that the natural oxide film may not be sufficiently protective in the aggressive biologic environment. PURPOSE: The goal of this study was to examine the effectiveness of a thick oxide layer on corrosion resistance in vitro and the bone formation around titanium implants in vivo. MATERIALS AND METHODS: A plasma source ion implantation (PSII) method was used to increase the thickness of the surface oxide layer. Several instruments were employed to confirm the surface properties before and after the surface modification. Potentiodynamic polarization measurements in a phosphate-buffered saline (PBS) solution were carried out to investigate corrosion resistance in vitro. Bone formation around this surface-modified specimen was examined in a rabbit model and assessed in histomorphometry. RESULTS: Improved corrosion resistance was demonstrated by the potentiodynamic polarization measurements. Light microscopic histomorphometry showed that all implants were in contact with bone and had some proportion of bone within the threads at 4 weeks; however, there were no significant differences compared with as-machined controls. CONCLUSIONS: The results indicate that in spite of improved corrosion resistance in vitro, a thick oxide layer fabricated with the PSII method does not influence early bone formation around titanium implants in vivo.