Medical ceramics based on hydroxyl-apatite

Suitable materials for bioactive bone implants are discussed. They should have open porosity, with a pore size exceeding the finest elements of red blood cells, i.e. 9-15 micron. The production of ceramics and articles from hydroxylapatite was examined. The powder, which was synthesised from Ca(OH)2 and H3PO4, consisted of aggregates of crystals 2-6 micron in size. The relationship between the ceramic density and the fabrication pressure is shown. The casting slips have a thixotropic-dilatant nature. Hydroxylapatite blanks can be made by all the main ceramic techniques. Ceramic with a general porosity level above 30%, and with 50-90% open pores (mainly 8-10 micron in size) were obtained by firing at 1250-1300 C. 5 refs.