Patient-specific cranioplasty, by direct and indirect additive manufacturing of biopolymers and implantable materials

Background: Autologous bones are traditionally used in surgical reconstruction of skullcap. Since patients’ bones are often unavailable or cause of infections, implantable synthetic materials emerged as promising alternative. These can be shaped by different technologies, while 3D printing offers remarkable chances in terms of flexibility, accuracy, cost-saving and customizability. Methods: This study aims to evaluate strengths and limitations of the three main strategies that imply additive manufacturing for the implementation of cranial prosthesis: (i) direct printing of PLA (polylactic acid) skullcaps, mould casting of poly(methyl methacrylate) (PMMA) prosthesis using (ii) silicone mould manufactured from a 3D printed master, (iii) 3Dprinted TPU (thermoplastic polyurethane) mould. Results: All solutions achieved good geometric accuracy and excellent mechanical resistance. Direct printing of the PLA resulted in the fastest strategy, followed by PMMA casting in a silicone mould. Conclusions: The use of silicone was overall more advantageous, due to lower costs and the possibility of sterilization by using autoclaving.