[Restoration of the alveolar crest with a biomaterial filler. A clinical and histological study].

The implantation of biocompatible hydroxyapatite is used for human mandibular ridge augmentation in edentulous patients. Histologically, we studied such a material after a long period of implantation (1 1/2 to 2 years) in two patients. The histologic study showed a narrow meshed net of collagen tissue surrounding the hydroxylapatite particles. In the periphery of that tissue, we could see an osteogenesis: the bony trabeculae thus formed firstly were made of an immature bony matrix with an irregular "woven" pattern; secondarily, a mature bone, quite similar to the normal bone, occurred. In our two observations, there was an unusual inflammatory reaction characterized by cellular infiltration of lipophages, lymphocytes and plasma cells in the connective tissue and in one case by a true ischaemic necrosis with granuloma and bacteria. In spite of that inflammation, the whole material was well tolerated, without foreign-body granuloma. Such a granuloma was only found in superficial areas of the gingiva, around extruded particles of the biomaterial.