Granuloma and plasma cell formation induced by the subcutaneous implantation of beta-whitlockite particles.

In this paper, the formation of a granuloma following subcutaneous implantation of beta-whitlockite powder is described. The implants were removed after 3, 5 and 7 wk and examined histologically. In the granuloma giant cells, macrophages, lymphocytes and plasma cells are present. The presence of plasma cells indicates that not only inflammation occurs, but that an immunoresponse also takes place. Resorption and phagocytosis of particles was observed and the particles were found in the regional lymph nodes after 7 wk. beta-Whitlockite powder induces an inflammation and both a cellular and a humoral immunological response, when implanted subcutaneously.

Bone induction by demineralized bone particles: long-term observations of the implant-connective tissue interface.

Allogeneic demineralized bone (DB) powder was applied to subcutaneous pockets and cranial defects of rats and histological, histomorphometrical, and radiological evaluation was performed one to 52 weeks after implantation. In both type of implants cartilage formation was observed after 1 week between DB particles and in former vascular channels and cervices within the particles. Foci of bone formation were observed after 2 weeks in the center of the implant. Remineralization of DB particles only occurred in close contact with the new bone tissue by which they became incorporated, indicating that remineralization of DB is a continuation of a process which has started in live bone. At all times, the interface between implant and connective tissue of the host consisted of a layer of non-remineralized DB particles embedded in fibrous connective tissue. This rim was thinner at the dura-mater-side in the cranial implants, compared with the skin-side of the same implants as well as all sides of the subcutaneous implants. The rim became thinner with time but never disappeared completely. The outer contour of the mineralized implant sometimes ran right through a DB particle. A critical concentration of bone-inducing agent leaking from DB particles seems to be necessary for bone induction. We suggest that at the interface of the implant and loose connective tissue this concentration is never reached, which results in maintenance of the rim.