Porous and Flexible Polyetheretherketone (PEEK) Mesh Based on Filament Fused Fabrication Technology: A Balance between Mechanical and Biological Characteristics for Guided Bone Regeneration

Space maintenance and stability of the barrier membrane play a more crucial role than cell occlusion in alveolar bone augmentation. Polyetheretherketone (PEEK) is a promising alternative to titanium mesh due to its remarkable biocompatibility and mechanical properties that match natural bone. This study designed and manufactured a highly porous, flexible, and palisade-like PEEK membrane with pore diameters of 300 μm, 500 μm, and 700 μm through fused filament fabrication (FFF) technology. The optimum pore size fulfilling the equilibrium between mechanical properties and biological behavior was explored for severe alveolar bone regeneration. Printing accuracy, surface structural characteristics, roughness, hydrophilicity, and mechanical properties of the PEEK membranes were evaluated. Finite element analysis (FEA) was conducted to analyze the stress and strain distribution in the guided bone regeneration (GBR) model. Cell morphology, viability, and osteogenic differentiation were carried out utilizing human umbilical cord Wharton's jelly-derived mesenchymal stem cells (hWJ-MSCs) in vitro. The calvarial defect of rabbits in critical size was established, and new bone formation at 4 and 8 weeks after implantation was evaluated by micro-CT and histomorphometry. The results showed that the PEEK meshes, accompanied by one rough surface and another smooth side, exhibited great printing accuracy and hydrophobicity. The mechanical properties were inversely proportional to the pore diameter of the PEEK mesh, yet all groups had satisfactory stretchability. FEA indicated great stress dispersion, spatial retention, and mucosal integrity preservation in PEEK-300 and PEEK-500. In vitro tests showed that the macropores of PEEK-500 and PEEK-700 promoted greater hWJ-MSC migration and osteogenic differentiation. PEEK-500 demonstrated relatively higher new bone formation and stronger trabeculae at 8 weeks after implantation in vivo. Based on the palisade-like and flexible configuration, our findings supported that the 3D-printed PEEK mesh with appropriate pore size was capable of achieving a balance between mechanical and biological characteristics, showing potential for application in GBR.