Dynamics of Bio-Oss Collagen incorporation in fresh extraction wounds: an experimental study in the dog

The objective of this experiment was to analyze processes involved in the incorporation of Bio-Oss Collagen in host tissue during healing following tooth extraction and grafting.

Five beagle dogs were used. Four premolars in the mandible ((3)P(3), (4)P(4)) were hemi-sected, the distal roots were removed and the fresh extraction socket filled with Bio-Oss Collagen. The mucosa was mobilized and the extraction site was closed with interrupted sutures. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2 and 4 weeks of healing could be obtained. The dogs were euthanized and perfused with a fixative. Each experimental site, including the distal socket area, was dissected. The sites were decalcified in EDTA, and serial sections representing the central part of the socket were prepared in the mesio-distal plane and parallel with the long axis of the extraction socket. Sections were stained in hematoxylin and eosin and were used for the overall characteristics of the tissues in the extraction socket. In specimens representing 1, 2 and 4 weeks of healing the various tissue elements were assessed using a morphometric point counting procedure. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells positive for tartrate-resistant acid phosphatase activity (TRAP), alkaline phosphatase and osteopontin were identified.

The biomaterial was first trapped in the fibrin network of the coagulum. Neutrophilic leukocytes [polymorphonuclear (PMN) cells] migrated to the surface of the foreign particles. In a second phase the PMN cells were replaced by multinuclear TRAP-positive cells (osteoclasts). The osteoclasts apparently removed material from the surface of the xenogeneic graft. When after 1-2 weeks the osteoclasts disappeared from the Bio-Oss granules they were followed by osteoblasts that laid down bone mineral in the collagen bundles of the provisional matrix. In this third phase the Bio-Oss particles became osseointegrated.

It was demonstrated that the incorporation of Bio-Oss in the tissue that formed in an extraction wound involved a series of different processes.