Biomaterials, substitutes, and tissue engineering in bone repair: current and future concepts

Bone is a complex, constantly changing organ comprised of mineralized hard tissue. This important structural component of vertebrate’s body serves a variety of functions. Healthy bone system is essential for lifelong execution of these functions. Millions of people worldwide suffer from bone defects due to various reasons, including trauma, tumor, bone diseases, congenital defects, and aging. These defects are increasingly becoming the majority of the clinical cases in orthopedics. For all the aforementioned cases in which the normal process of bone regeneration is either impaired or simply insufficient, there are currently a number of treatment methods available which can be used either alone or in combination for the enhancement of bone healing and regeneration. Accordingly, bone repair has been the focus of many research activities related to clinical therapies. The traditional bone repair procedure widely used in current era involves the use of bone-grafting methods such as autografts, allografts, and xenografts; however, these methods are associated with number of limitations. Therefore, to overcome these problems, tissue engineering as a new and developing option had been introduced recently. In order to provide ideal bone substitutes, a wide range of biomaterials and synthetic bone substitutes are available depending on the goal, each has advantages and disadvantages. The combined use of different bone substitutes together with healing promotive factors, stem cells, gene therapy, and more recently, three-dimensional printing of tissue-engineered constructs may open new insights in bone regeneration in near future. In this review, we describe developments and recognized properties of some of the most utilized materials in bone regenerative medicine heretofore. It may be concluded that presently strong requirements are still to be met in the repair and regeneration of bone defects.