Hydroxyapatite formed from Coral Skeletal Carbonate by Hydrothermal Exchange

Abstract

WE have prepared porous microstructures, having potential for prosthetic applications, consisting of hydroxapatite and of whitlockite, by employing exchange reactions at elevated temperatures and pressures. Rather demanding specifications are to be met by biomaterials being considered for tooth or bone replacement. Porous solids have the advantage of allowing circulation of body fluids and of increasing the potential for firm attachment of body tissue^1,2. Weber et al.³ successfully replicated the porous structure of echinoid skeletal material in epoxy resin and in sodium silicate; and White et al.⁴ achieved replication of the coral Porites structure with methacrylate, tin, Tichonium, and sintered Al₂O₃. This was the starting point for our attempts to reproduce such structures in the phosphatic material which is a major component of human teeth and bones, hydroxyapatite. Such a material, porous, inorganic and sterile (formed at high temperatures and pressures), should be highly compatible with body tissue, and when used as bone implants may become essentially integral with the bone. Furthermore, composites of such porous hydroxyapatite with other materials including metals⁴ may achieve optimum mechanical and physical properties for a particular application.