This review analyzes the literature of bone grafts and introduces tissue engineering as a strategy in this field of orthopedic surgery. We evaluated articles concerning bone grafts; analyzed characteristics, advantages, and limitations of the grafts; and provided explanations about bone-tissue engineering technologies. Many bone grafting materials are available to enhance bone healing and regeneration, from bone autografts to graft substitutes; they can be used alone or in combination. Autografts are the gold standard for this purpose, since they provide osteogenic cells, osteoinductive growth factors, and an osteoconductive scaffold, all essential for new bone growth. Autografts carry the limitations of morbidity at the harvesting site and limited availability. Allografts and xenografts carry the risk of disease transmission and rejection. Tissue engineering is a new and developing option that had been introduced to reduce limitations of bone grafts and improve the healing processes of the bone fractures and defects. The combined use of scaffolds, healing promoting factors, together with gene therapy, and, more recently, three-dimensional printing of tissue-engineered constructs may open new insights in the near future.

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Healing and regeneration of bone injuries, particularly those that are associated with large bone defects, are a complicated process. There is growing interest in the application of osteoinductive and osteogenic growth factors and mesenchymal stem cells (MSCs) in order to significantly improve bone repair and regeneration. MSCs are multipotent stromal stem cells that can be harvested from many different sources and differentiated into a variety of cell types, such as preosteogenic chondroblasts and osteoblasts. The effectiveness of MSC therapy is dependent on several factors, including the differentiating state of the MSCs at the time of application, the method of their delivery, the concentration of MSCs per injection, the vehicle used, and the nature and extent of injury, for example. Tissue engineering and regenerative medicine, together with genetic engineering and gene therapy, are advanced options that may have the potential to improve the outcome of cell therapy. Although several in vitro and in vivo investigations have suggested the potential roles of MSCs in bone repair and regeneration, the mechanism of MSC therapy in bone repair has not been fully elucidated, the efficacy of MSC therapy has not been strongly proven in clinical trials, and several controversies exist, making it difficult to draw conclusions from the results. In this review, we update the recent advances in the mechanisms of MSC action and the delivery approaches in bone regenerative medicine. We will also review the most recent clinical trials to find out how MSCs may be beneficial for treating bone defects.