Biomechanical and functional comparison of moulded and 3D printed medical silicones

Modern 3D printing of implantable devices provides an important opportunity for the development of personalized implants with good anatomical fit. Nevertheless, 3D printing of silicone has been challenging and the recent advances in technology are provided by the systems which can print medical grade silicone via extrusion. However, the potential impacts of the 3D printing process of silicone on its biomechanical properties has not been studied in sufficient detail. Therefore, the present study compares 3D printed and moulded silicone structures for their cytotoxicity, surface roughness, biomechanical properties, and in vivo tissue reaction. The 3D printing process creates increased nanoscale roughness and noticeably changes microscale topography. Neither the presence of these features nor the differences in processes were found to result in an increase in cytotoxicity or tissue reaction for 3D printed structures, exhibiting limited inflammatory reaction and cell viability above the threshold values. On the contrary, the biomechanical properties have demonstrated significant differences in static and dynamic conditions, and in thermal expansion. Our results demonstrate that 3D printing can be used for establishing a better biomechanical microenvironment for the surrounding tissue of the implant particularly for fragile soft tissue like epithelial mucosa without having any negative effect on the cytotoxicity or in vivo reaction to silicone. For engineering of the implants, however, one must consider the differences in mechanical properties to result in correct and personalized geometry and proper physical interaction with tissues.