THE EFFECT OF DEMINERALIZED BONE-MATRIX ON THE HEALING OF INTRAMEMBRANOUS BONE-GRAFTS IN RABBIT SKULL DEFECTS

A clinical dilemma exists regarding the type of bone that should be us ed to replace diseased or traumatized osseous tissue. Oral, plastic, a nd orthopedic surgeons normally implant viable mineralized endochondra l (EC) autografts or demineralized EC allografts. A few clinicians hav e recognized the disadvantages of using EC bone in craniofacial surger y and advocated the replacement of intramembranous (IM) bone with heal thy IM bone. However, controversy and uncertainty surround our underst anding of these matrices to induce bone formation. Recent studies have advocated the use of other materials with osteoinductive properties, such as demineralized bone matrix (DBM). The proposed delivery system used in this study included IM bone grafts, DBM, and fixation of the I M bone graft. The purpose of this work was to gain further insights in to the mechanism of healing of IM bone, in both the presence and the a bsence of DBM, and to compare the healing of IM bone grafts with that of DBM alone. Critical-sized (10 x 5 mm), full-thickness bony defects in rabbit parietal bone, devoid of periosteum, were filled with IM bon e graft (mandible) alone, demineralized cortical bone matrix (DBM) alo ne, or combined DBM-IM bone graft, or were left unfilled. Histologic c hanges were examined 14 days later. The IM bone graft healed through I M ossification with no intermediate cartilage stage. DBM and composite intermediate cartilage stage. It is hypothesized that the role of the IM graft is to induce neovascularization into the defect site, and th at the undifferentiated mesenchymal cells in the perivascular region o f the new blood vessels are induced by the bone morphogenetic protein( s) in the DBM into bone-forming cells.