The paper describes a new method for converting the existing oxide layer of implants of titanium and titanium alloys in calcium containing surface layers. The layers were generated by dipping the implants in a salt melt consisting of calcium nitrate at temperatures of 520°C until 560°C for 2 until 4 hrs. The melt reacted with the surface layer of the implants by forming calcium titanate surface layers. Besides, the thickness of the TiO 2 layer of the implants became larger. Several methods for the determination of the layer thickness were investigated related to their suitability. The micro hardness of the layer and the tribological behaviour were investigated. The presented procedure can be used for generating calcium containing surface layers on implants of titanium alloys even with complicated forms.

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Nowadays total joint replacement is an indispensable component of modern medicine. The surfaces characteristics of cementless prostheses may be altered to achieve an accelerated and enduring bony integration. Classic surface coatings bear the risk of loosening or flaking from the implant body. This risk is excluded by the chemical conversion of the naturally existing TiO(2) surface layer into calcium titanate. The aim of this experimental animal study was to investigate the bony integration of implants with a new calcium titanate surface (Ca(4)Ti(3)O(10)) compared with a conventional standard Ti6Al4V surface. Cylindrical implants, made of titanium alloy (Ti6Al4V) were implanted in both lateral femoral condyles of New Zealand white rabbits. In each animal, an implant with and without surface treatment was inserted in a blinded manner. Animals were sacrificed after 4, 12, and 36 weeks, respectively. The axial pull-off forces were determined for 25 animals using a universal testing machine (Zwick Z010, Ulm, Germany). Furthermore, a histological analysis of the bony integration of the implants was performed in 12 specimens. In general, the pull-off forces for untreated and treated implants increased with longer survival times of the rabbits. No significant difference could be shown after 4 weeks between treated and untreated implants. After 12 weeks, the treated implants revealed a statistical significant higher pull-off force. After 36 weeks, the pull-off forces for treated and untreated implants aligned again. Titanium implants treated with calcium titanate, may offer an interesting and promising implant surface modification for endoprosthetic implants. They might lead to an accelerated osseointegration of total hip and knee replacements.

Discs of TiAl6V4 were cleaned and stored in calcium containing salt melt. The characterization of the reaction layer was realized by TF-XRD, SEM, SIMS, AES, and eddy current. The release of Ca ions was determined after storing the samples in TRIS-HCl buffer solution under physiological conditions for at least 16 weeks. The thickness of the generated calcium titanate layer varied in dependence on salt melt composition, temperature, and storing time in the range of 0.4-0.9.m. The Ca content of the layer depends on melt composition, temperature and storing time and was in the range from 5-42.g●cm-2 in correlation with the thickness. The morphology of the layers also changed in dependence on the salt melt composition and the storing time and temperature.