HYDROXYAPATITE-GLASS COMPOSITE AS A BONE SUBSTITUTE IN LARGE METAPHYSEAL CAVITIES IN RABBITS

This study evaluated hydroxyapatite-glass (HA-G) composite as a filler material when implanted into a proximal metaphyseal tibial cavity con sisting of medullary tissue and cancellous bone in rabbits. The repair process was compared with that of autogenous bone grafts and untreate d controls. Scanning electron microscopy, energy dispersive x-ray stud ies, radiography, histology with tetracycline fluorescence and morphom etric bone measurements were used for evaluation. Equal amounts of min eralised bone were produced in both HA-G granule and autograft groups at 3 weeks; thereafter autografts mostly resorbed, whereas there was a ppositional lamellar bone formation on the early woven bone in the HA- group. A relatively small proportion of the cavities was repaired by n ew bone. The HA-G granules were biocompatible without foreign body rea ction and showed good osteoconductive potential. Mesenchymal cells wer e able to ddifferentiate into osteoblasts on bioactive surfaces of the composite. Although HA-G was able to form Ca-P-rich and Si-rich layer s, most of the granules underwent degradation through its glass matrix , resulting in fewer bony contacts than granules with no surface degra dation.