A new bioactive material which transforms in situ into hydroxyapatite

A new route of obtaining bioactive ceramic materials, which improve the ingrowth of new bone into implants (osseointegration), is presented. This involves obtaining eutectic structures from selected systems, bearing in mind the different bioactive behaviour of the phases. In this work the eutectic binary system wollastonite-tricalcium phosphate was chosen because wollastonite is bioactive and tricalcium phosphate is resorbable. The eutectic material is formed by spherical colonies composed of alternating radial lamellae of wollastonite and tricalcium phosphate. The eutectic material, in in vitro experiments, reacts by dissolving the wollastonite phase and forming a porous structure of hydroxyapatite by a pseudomorphic transformation of the tricalcium phosphate lamellae, which in turn mimic porous bone. Later, a hydroxyapatite layer is formed by precipitation on the surface of the material. The procedure developed by the authors opens the opportunity to obtain a new family of bioactive materials for which the general name of bioeutectic(R) is proposed. (C) 1998 Acta Metallurgica Inc.