Bone formation in tricalcium phosphate-filled periodontal intrabony lesions. Histological observations in humans.

The capacity of a tricalcium phosphate (TCP) ceramic to promote bone formation after grafting in intrabony defects was studied in humans. Five biopsies were collected from 4 patients during reentry surgery 16 to 40 months after implantation. They were processed without demineralization for histological examination. In the less mature samples, the grafted material was surrounded by a highly fibrous, highly cellular, and poorly vascularized connective tissue. Howship's lacuna-like cavities were clearly visible at the surface of the material. They contained resorbing mononuclear phagocytes. At a more mature stage, TCP granules were embedded in an acellular fibrous material which underwent mineralization from the medullary spaces towards the granules. The bone formed was subsequently remodeled. The implanted material itself was progressively modified. It first acquired the staining appearance of bone. After its structure became loose and vacuolated, it was invaded by cells and vessels. The present data indicate that TCP has osteogenic potential and is subject to degradation. Unlike in experimental wounds, these processes are of long duration in human defects.