Anodic plasma-chemical treatment of CP titanium surfaces for biomedical applications

The anodic plasma-chemical (APC) process was used to modify CP titanium surfaces for biomedical applications. This technique allows for the combined chemical and morphological modification of titanium surfaces in a single process step. The resulting conversion coatings, typically several micrometer thick, consist mainly of titanium oxide and significant amounts of electrolyte constituents. In this study, a new electrolyte was developed containing both calcium—stabilized by complexation with EDTA—and phosphate ions at pH 14. The presence of the Ca-EDTA complex, negatively charged at high pH, favors incorporation of high amounts of calcium into the APC coatings during the anodic (positive) polarization. The coating properties were evaluated as a function of the process variables by XPS, GD-OES, Raman spectroscopy, SEM and tensile testing, and compared to those of calcium-free APC coatings and uncoated CP titanium surfaces. The maximal Ca/P atomic ratio in the coating produced with the new APC electrolyte was approximately 1.3, with higher Ca concentrations than reported in conventional APC coatings. The dissolution behavior of the incorporated, amorphous CaP phases was investigated by exposure to a diluted EDTA solution. The coatings produced in the new electrolyte system exhibit favorable mechanical stability. The new APC technology is believed to be a versatile and cost-effective coating technique to render titanium implant surfaces bioactive.