OSTEOGENIC RESPONSE TO HYDROXYAPATITE-FIBRIN IMPLANTS IN MAXILLOFACIAL BONE DEFECTS

Bone formation in hydroxyapatite-fibrin implants has been reported sev eral times. However, available studies refer to experimental animals, or are limited to short periods after implantation. We report the resu lts of histological, histochemical and ultrastructural studies carried out 2.5-8 yr after implantation of non-resorbable, porous hydroxyapat ite (HA) and fibrin glue in human maxillofacial bones. Prominent ossif ication was found in all cases, with the presence of normally structur ed spongy bone. HA granules were embedded in the calcified bone matrix . They had not elicited inflammatory reactions and did not induce bone resorption. Ossification was preceded by the appearance of alkaline p hosphatase activity on fibroblast-like cells, and by the formation of dense collagenous layers, similar to osteoid borders, on the surface o f HA granules. The early phases of the calcification process occurred in these borders, with the appearance of calcification nodules adjacen t to alkaline phosphatase-positive osteoblast-like cells. A remodeling process similar to that occurring in normal bones was found in the ne wly formed bone. These results justify the conclusion that HA-fibrin i mplants lead to the formation of long lasting bone that does not diffe r from that of the normal maxillofacial skeleton. Mixing the HA granul es with fibrin has the advantage of creating an easily mouldable mater ial which can be adapted to any skeletal surface and stays in place af ter surgery.