The goal of bone grafting is to replace normal bone volume and structure with healthy, well-vascularized bone that will undergo normal remodeling. The ideal bone will regenerate bone and not repair it. Currently four types of grafting material are available to clinicians for regenerative use in oral and maxillofacial surgery: autologous bone, allogeneic bone, xenogenic bone, and alloplastic bone. Additionally, bioactive agents, growth factors, are now being used to stimulate osteoinductive properties of native bone for bone regeneration. This article reviews the literature and summarizes the benefits and disadvantages of each respective graft and illustrates its use in clinical practice.
Key points
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Bone is a dynamic composite structure that provides framework to the human body. The ultimate goal of bone grafting is to regenerate bone into well-vascularized bone that will undergo normal remodeling.
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Four basic types of bone grafting materials are available for use clinically: autologous bone, allogeneic bone, xenogenic bone, and alloplastic bone.
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Bone morphogenic protein is a family of osteoinductive proteins that stimulate endochondral and intramembranous bone formation from mesenchymal cells.
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The literature reports evidence of successful, clinically significant, bone regeneration with each respective grafting material. However, autologous bone grafting remains the gold standard.
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Autogenous bone grafts will most likely remain the gold standard of grafting materials. All four types of bone grafting material show good clinical evidence of bone regeneration in different degrees, respectively.
The ultimate goal of bone grafting is to replace normal bone volume and structure with healthy, well-vascularized bone that will undergo normal remodeling. The ideal bone graft regardless of the purpose, whether it is to augment the alveolus for prosthetic reasons or reconstruct the mandible following enucleation of a cyst, is to achieve histology of bone with no distinguishing features from the original local tissue. The ideal bone will regenerate bone and not repair it. The purpose of this article is to cover the biology of bone grafting and provide an overview of the different grafting materials that are available.
Bone is a dynamic composite structure that provides framework to the human body. Bone is composed of cortical and lamellar bone originating from ectomesynchyme, an element of the developing embryo ( Table 1 ). As the body grows mesenchymal cells are stimulated by growth factors and differentiate into osteoblasts and osteoclasts. As bone is deposited around osteoblasts, it becomes embedded in the matrix, becoming an osteocyte. The spaces that house the osteocyte are referred to as lacunae. In an adult immature bone cells referred to as osteoprogenitor cells linger in the periosteum and endosteum, which reserve the potential to differentiate into osteoblasts if the need arises. For example, osteoprogenitor cells will receive cytokine signals that induce differentiation into osteoblasts following bone fracture or during exercise where the bone loading is changed.
| Type of Bone | Histologic Features |
|---|---|
| Organized matrix | 40% of the dry weight of bone. Composed of 90% type 1 collagen, noncollagenous proteins, ground substance, water, proteoglycans, cytokines, and growth factors. |
| Cells | Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts |
| Vascular and nutrient distribution | Bone receives 5%–10% of cardiac output via arterial supply through the periosteum and endosteum. Extracellular fluid is drained through microcirculation, lymphatics, and venous return. |
| Neurologic | Bone is supplied by autonomic and neurosensory networks. |
| Marrow | Serves hematopoietic and osteogenic functions. |
| Periosteum | A source of osteoprogenitor cells, neurovascular distribution, and blood supply. |
| Endosteum | A source of osteoprogenitor cells. |
| Communication systems | A network including haversian and Volkmann canaliculi lacunae and extracellular fluid. |
Hard tissue heals through stages over the period of approximately 16 weeks. The stages when listed sequentially are the inflammatory, proliferative, and the remodeling phases. Initially the healing depends on formation of a hematoma and subsequently angiogenesis and vascular invasion from the surrounding periosteum and endosteum. Within 48 hours of surgery a hematoma forms with organizing soft tissue and collagen deposition. The decreased partial pressure of oxygen in the tissue induces release of growth factors and stimulates angiogenesis and osteogenesis. A fibrin mesh forms and acts as scaffolding for the fibroblasts and capillary buds. The addition of bone grafting provides the marginating osteoblasts and fibroblasts with a macrostructure to deposit new tissue.
Four basic types of bone grafting materials are available for use clinically to augment and reconstruct the maxillofacial skeleton ( Tables 2–4 ).
| Bone Type | Description |
|---|---|
| Autograft (autogenous) | Refers to a transplant of viable cortical or cancellous bone from one location of the body to another within the same patient. |
| Xenograft | Refers to a cross-species transplantation of tissue: the use of organic bovine bone or porcine collagen subjects. |
| Alloplast | Refers to implantation of synthetic material, such as apatite or tricalcium phosphate, bioactive glass, or polymers. |
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