Bone grafting uses natural or synthetic substitutes to replace missing or broken bones, which allows the patient’s own bone tissue to generate new tissue to replace the synthetic materials used in grafting. A synthetic bone graft uses commercially produced ingredients that are structurally similar and have similar biomechanical properties to that of bone tissue. A synthetic bone graft can be created from materials such as ceramics, demineralized bone matrix, coral or a blend of those. While synthetic bone grafts are still used much less frequently than grafts created from the patient’s own bone, they do eliminate the risk of infection and pain associated with harvesting and can be used in large amounts.
Bone graft material has three major functions: osteogenic, osteoinductive and osteoconductive. An osteogenic material helps to form new bone tissue and cells. Osteoinductive grafts act to encourage the cells to change into osteoblasts. Osteoconductive grafts act as a three-dimensional structure on which new tissue can grow. A synthetic bone graft usually only contains one or two of these properties.
The majority of synthetic bone grafts use ceramic materials, which are porous and provide structure for bone growth. Ceramics containing calcium phosphate materials, such as derived hydroxyapatite compound and tricalcium phosphate composite, are osteoconductive, osteogenic and can sometimes be osteoinductive. Some ceramic materials, such as bioglass, do not contain natural growth proteins and are usually infused with bone marrow and other bone growth proteins to promote cell regeneration. These materials serve as the scaffolding for new bone tissue, and they simply dissolve once the new bone structure is in place.
Demineralized bone matrix (DBM) contains collagen and growth materials that have been withdrawn from the bones of cadavers. DBMs contain natural osteoinductive proteins called bone morphogenetic proteins (BMP), which stimulate the formation of new bone tissue. DBM comes in a paste, gel, putty or powder format because of the extensive processing required when extracting its components. Another material is usually combined with DBM if the bone graft needs structural properties.
Coral bone grafts are created from the exoskeleton of marine corals. A synthetic bone graft made from coral resembles the structure of human bone tissue, but it does not naturally contain growth proteins. Coral is preferable for patients undergoing major reconstructive surgery, because the material can be acquired in large amounts and provides a strong structure for bone regrowth.
Composite grafts are a mixture of ceramics and DBM. By combining the two materials, the graft has the structure and the growth proteins needed to form new bone tissue. Most synthetic materials only provide the strength or the proteins needed, so composite grafts can be effective in providing a scaffold for new bone formation and in promoting the growth of new cells.