MORPHOLOGICAL INVESTIGATIONS ON BONE-FORMATION IN HYDROXYAPATITE-FIBRIN IMPLANTS IN HUMAN MAXILLARY AND MANDIBULAR BONE

The tissue reaction and bone formation which occur in contact with gra nules of porous hydroxyapatite moulded with fibrin ''glue'' and implan ted in human maxillary and mandibular bone defects were studied. Fourt een specimens from twelve patients were examined at different times af ter implantation (from 4 to 26 months). Histology and electron microsc opy showed the presence of implanted hydroxyapatite, fibrillar connect ive tissue and bone trabeculae. The fibrillar connective tissue predom inated in the 4- to 9-month-old implants, while the osseous trabeculae were approximately 30% or less in volume. The osseous trabeculae pred ominated and constituted more than 80% of the volume in the implants b iopsied after 13-26 months. The development of bone tissue occurred th rough osteoid-like condensation of fibrillar connective tissue, differ entiation of fibroblast-like cells into roundish, osteoblast-like cell s, and appearance of alkaline phosphatase activity in both cell types. The bone tissue enclosed hydroxyapatite granules. Free granules were resorbed by osteoclast-like cells. Bone remodeling and replacement of woven with lamellar bone were present in the oldest implants. The resu lts show that porous hydroxyapatite granules can be profitably used in oral and maxillofacial reconstruction because their mixture with fibr in glue yields a material that can be adapted to bone defects of every shape, is not displaced during healing and, above all, is osteoconduc tive.