Secondary alveolar bone grafting: the dilemma of donor site selection and morbidity.

Fresh autogenous cancellous bone is ideal for secondary alveolar cleft bone grafting because it supplies living, immunocompatible bony cells that integrate fully with the maxilla and are essential for osteogenesis. Recent animal studies have shown that the dynamics of cancellous inlay bone grafts are different from those of cortical onlay bone grafts, and they refute the assumption that membranous bone grafts are superior to endochondral bone grafts because of their embryological origin. These studies prove that inlay endochondral cancellous specimens have a higher percentage increase in actual bony volume than cortical membranous and cortical endochondral inlay bone grafts. There are various donor sites for secondary alveolar cleft bone grafts. Currently the main sites for autogenous cancellous bone are iliac crest, calvarium, mandibular symphysis, and tibia. Some authors have suggested that the iliac crest donor site causes an unacceptably high degree of postoperative morbidity, but it is still the first choice for secondary alveolar cleft bone grafts and should not be rejected solely because of such concerns. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is now an attractive bony substitute that promotes the differentiation of pluripotential cells into bone-forming cells that lay down new host bone in the site of the defect. Much more research and development are necessary to find a suitable carrier for rhBMP-2, and to study the properties of newly formed bone that it has induced before it can be a substitute for autogenous bone.