Induction of multinucleated giant cells in response to small sized bovine bone substitute (Bio-Oss™) results in an enhanced early implantation bed vascularization

PURPOSE: The host tissue reaction to the xenogeneic bone substitute Bio-Oss™ (Geistlich Biomaterials, Wolhousen, Switzerland) was investigated focusing on the participating inflammatory cells and implantation bed vascularization. MATERIALS AND METHODS: Bio-Oss™ was implanted subcutaneously into CD1 mice for up to 60 days and analyzed by means of specialized histological and histomorphometrical techniques after explantation. RESULTS: Bio-Oss™ induced within the first 15 days an early high vascularization combined with a marked presence of multinucleated giant cells. The latter cells were associated mainly with the smaller sized granules within the implantation bed. Toward the end of the study the number of multinucleated giant cells decreased while the tissue reaction to the larger granules was mainly mononuclear. CONCLUSION: The results of the present study showed that smaller xenogeneic bone substitute granules induce multinucleated giant cells, whereas the larger-sized ones became integrated within the implantation bed by means of a mononuclear cell-triggered granulation tissue. Obviously, the presence of multinucleated giant cells within biomaterial implantation beds is not only related to the type of synthetic bone substitute material, but also to the granule size of the natural-based xenogeneic bone substitute material.