Production of porous hydroxyapatite by the gel-casting of foams and cytotoxic evaluation

This study presents the manufacture of highly porous hydroxyapatite by a no vel technique that employs the foaming of suspensions prior to the in situ polymerization of organic monomers contained in the compositions. This meth od produces strong gelled bodies with up to 90% porosity that can withstand machining in the green state. Complex-shaped components can be obtained if the process comprises casting in one of the processing steps. The organic additives are eliminated at temperatures above 300 degrees C, and sintering is carried out for consolidation of the ceramic matrix. Spherical intercon nected cells with sizes ranging from 20 to 1000 mu m characterize the porou s structure, depending on the specimen density. Cytotoxicity tests were con ducted on extracts from sintered HA foams based on a quantitative method of cell colony formation and the determination of cell death after indirect c ontact of the porous material with mammalian cells. This in vitro test of b iological evaluation revealed that the original purity of the biomedical-gr ade hydroxyapatite powder was affected neither through processing nor by th e employed reagents. (C) 2000 John Wiley & Sons, Inc.