Three-Dimensional Printing for Craniofacial Bone Tissue Engineering

The basic concepts from the fields of biology and engineering are integrated into tissue engineering to develop constructs for the repair of damaged and/or absent tissues, respectively. The field has grown substantially over the past two decades, with particular interest in bone tissue engineering (BTE). Clinically, there are circumstances in which the quantity of bone that is necessary to restore form and function either exceeds the patient's healing capacity or bone's intrinsic regenerative capabilities. Vascularized osseous or osteocutaneous free flaps are the standard of care with autologous bone remaining the gold standard, but is commonly associated with donor site morbidity, graft resorption, increased operating time, and cost. Regardless of the size of a craniofacial defect, from trauma, pathology, and osteonecrosis, surgeons and engineers involved with reconstruction need to consider the complex three-dimensional (3D) geometry of the defect and its relationship to local structures. Three-dimensional printing has garnered significant attention and presents opportunities to use craniofacial BTE as a technology that offers a personalized approach to bony reconstruction. Clinicians and engineers are able to work together to produce patient-specific space-maintaining scaffolds tailored to site-specific defects, which are osteogenic, osseoconductive, osseoinductive, encourage angiogenesis/vasculogenesis, and mechanically stable upon implantation to prevent immediate failure. In this work, we review biological and engineering principles important in applying 3D printing technology to BTE for craniofacial reconstruction as well as present recent translational advancements in 3D printed bioactive ceramic scaffold technology. Impact statement Surgical reconstruction for extensive bone defects has evolved over the last 20 years toward a more customized treatment approach which fulfill functional outcomes. Additionally, the merger of surgical and microvascular principles has given rise to custom tailored patient-specific free tissue flaps which reconstruct bony maxillofacial defects while rebuilding lining, soft tissue mass, and facial subunits-all of which are key to achieving outcomes that approach normalcy. The contemporary techniques for complex boney defect reconstruction remain constrained: autologous bone transfer is complicated by limited bone stock and shape, donor site morbidity, surgical site infection, delayed healing, long operative times, and cost. Due to the shortcomings associated with autologous bone, advances in bone tissue engineering (BTE), such as 3D printing for patient and site-specific devices, have sought to restore bone deficiencies using customizable devices (scaffolds).