Ectopic osteogenesis with biphasic ceramics of hydroxyapatite and tricalcium phosphate in rabbits

Porous calcium phosphate ceramics consisting of hydroxyapatite (HA) and tri calcium phosphate (TCP) with different HA to TCP ratio were implanted intra muscularly in rabbits for six months in order to carry out a comparative st udy on osteogenic activity of the ceramics. Bone formation was detected onl y in HT73 (HA to TCP ratio; 7-3) specimens. Other implants, HT28 (2-8) and HT010 (0-10), could not induce bone. After a six-month period of implantati on, HT28 and HT010 implants showed obvious degradation of the implants chan ging their shape and size macro and microscopically. Microscopically, they showed aggregates of fine particles and appearance of multinucleated cells. However, HT73 implants was less degraded and could maintain their original structure macro and microscopically. This study showed that HT73 ceramics can induce bone in rabbit muscle tissue and it is considered that maintenan ce of porous structure, that is, degradation rate of the materials may be o ne of the affecting factors in ceramic-induced osteogenesis. (C) 2001 Elsev ier Science Ltd. All rights reserved.