Surface Characterization of Titanium Implant Materials

7th World Biomaterials Congress, Sydney, Australia, May 2004

Mazzei, A. C. A.1 2, Ferreira, I.1, Reis, G. M. Jr.2, Cintra, P. T.2.
1 University of Campinas, Campinas, SP, Brazil
2 GM Reis Implants, Campinas, Brazil

Abstract

Titanium and titanium alloys metallic biomaterials are widely used to fabricate orthopedic implants because of their high biocompatibility combined with good mechanical properties. The processes used to modify the surface of these biomaterials are known and described in current literature. In these processes it can occur deposition or formation of dissimilar materials by physical and chemical processes and the aim of these surface modifications are to produce a porous coating which improves the osteo-integration (bone ingrowth) [1] and the fixation of the bone on the surface of the implant [2, 3]. The objective of the present work was to characterize the surface obtained by electrochemical anodization of Ti-6Al-4V (ASTM F 136) alloy using sulfuric acid as electrolyte.

In the case of this process it was observed the formation of a thin titanium oxide film that was preferentially in the crystalline phase anatase, which is an antibacterial material because of its catalytic property for the redox reaction of hydrogen peroxide [4]. In order to verify the existence of this crystalline phase, low angle X-Ray diffraction tests were conducted in 15 x 15 x 3 mm anodized samples. The semi-quantitative analyses of the X-Ray spectrums reveled 68% of anatase in the oxide film.

Two different tests were used to evaluate the oxide film thickness: electrochemical impedance measurement and Scanning Electron Microscopy (SEM) of the transversal section of the oxide film, as shown in figure 1(a). The values obtained for the oxide film thickness were 6.20m m and 5.89m m, using SEM analyses and electrochemical impedance measurement, respectively. SEM observations were also used to evaluate the oxide surface film morphology as shown in figure 1(b). The rough surface observed has a porosity of 36%. Oxide film thickness greater than 2m m and surface porosity about 35-40% are desirable to improve osteo-integration [3].

Chemical analysis of the oxide film using Energy Dispersive Spectroscopy (EDS) in conjunction with the Scanning Electron Microscopy (SEM) did not reveal the presence of toxic chemical elements that could be provided by the electrolyte. The detected elements were Al and V, possibly from the alloy; and Ti, from the alloy and the oxide film.

Keywords

Titanium (alloys), surface modification, surface analysis.

Acknowledgments

The authors would like to thank DEMA / Faculty of Mechanical Engineer -UNICAMP and GM Reis Implants.

(a) Transversal section

(b) SEM of the oxide film. Surface of the anodized sample.

Conclusions

The surface characterization revealed that the employed electrochemical anodization process produced a surface with properties that improve osteo-integration.

References

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[2] Amigo, V., Salvador, M.D., Romero, F. Solves, C. Moreno, J. F.. Microestructural Evolution of Ti-6Al-4V During the Sintering of Microspheres of Ti for Orthopedic Implants. Mat. Proc. Tech. Article in Press, 2003.
[3] Brooker, A. F., Collier, J. P.. Evidence of bone ingrowth into a porous-coated prosthesis. A case report. J Bone Joint Surgery. Am. A 66 (1984) 619.
[4] Tanaka, Y., Cross Sectional TEM Observation of Anodized Titanium Surface, International Academic Exchange Seminar by faculty members of Nagasaki University School of Dentistry, 2003.