Processing of Ca-P Ceramics, Surface Characteristics and Biological Performance

Surface pollution by Mg and carbon has been identified by X-Ray Photoelectron Spectroscopy (XPS) analysis on monophasic (100% stoichiometric hydroxyapatite) or biphasic (70% hydroxyapatite, 30% β-tricalcium phosphate) ceramics obtained by sintering of Ca-P powder of standard purity. Magnesium was the main impurity, although it is present only as traces in synthesised Ca-P powders, it concentrates on the surface of the ceramic during the sintering process due to its poor solubility in HA. Carbon pollution is common on all materials and generally assigned to the adsorption of atmospheric volatile organic compounds, although other types of pollution may occur. These surface species alter the surface energy of the ceramics which has been shown to be related to cell adhesion, The change in surface composition and physical properties can interfere with the sintering process as well as with the biological behaviour of the ceramics and a special effort should be made to control these events at all levels from processing to handling, storage and packaging.