Ion adsorption on titanium surfaces exposed to a physiological solution

Changes in surface properties of titanium platelets exposed to a physiologi cal solution (Hanks' solution) were studied by Auger electron spectroscopy and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy fo r surface chemical composition analysis and by Scanning Force Microscopy fo r surface topography measurements. An adsorbed layer of calcium-phosphate w as spontaneously formed on the titanium oxide surface and its thickness as well as the Ca/P ratio was found to increase with immersion time. After 71 days of immersion, the Ca/P ratio corresponded to that of brushite or monet ite and after 6 months it was close to the value of hydroxyapatite. A highe r Ca/P ratio was found for adsorption from solutions where the pH had been increased. After adsorption, the grains of the evaporated titanium substrat e appeared slightly smoother because they were covered by a thin layer of c alcium phosphate. A comparison between immersion in a Hanks' solution and s olutions containing only phosphates or only calcium ions, showed that the p resence of phosphates is necessary for the adsorption of Ca-ions. (C) 1999 Elsevier Science B.V. All rights reserved.