This doctoral thesis addressed the topic of additive manufacturing of biofunctional craniomaxillofacial implants made of plastics by filament-based material extrusion. It is the goal of the researcher that the chosen technical approach will ultimately overcome the shortcomings of medically-established additive processes such as restricted material variety, aesthetic limitations, or long manufacturing times. As a result, implementing material extrusion should shorten healing periods and increase the long-term well-being of patients. The defined goal of the work was a successful filament-based material extrusion of medically applicable implants. The underlying vision was the implants’ clinic-internal and operation-accompanying application. Following a literature search, the first experimental stage, a preliminary study, established a systematic method for the investigation of the interface interaction between plastic and tissue. This took place in the cell laboratory with a newly-developed cell carrier system. The cell carrier system included injection-molded slides made of a defined range of plastics in standard microscope format. The aim of this preliminary study was to reduce the complex system to a simple model system in order to provide starting points for the later interface design of the printed implants. The second experimental stage involved a stepwise material selection based on the preliminary investigations, followed by in-depth biological and plastics material testing. Bioactivated compounds and unfilled references comprised the material basis. Digitally-prepared 3D models of a cranial and a maxillofacial implant were printed based on the material selection. A specially-developed dynamic testing method, based on a falling weight test, was utilized to conduct the mechanical implant testing. A coordinate measuring machine and an ex-vivo model of the implant environment evaluated dimensional and fitting traits of the implants. The preliminary study revealed a significant influence of surface energy and its anisotropy on cell adhesion and cell morphology. Based on the consecutive material selection in the beginning of the second experimental phase, glycol-modified PET (PETG) and thermoplastic polyurethane were finally selected for the implant printing. These plastics had high cell acceptance, good mechanical properties, and optimal printability. Compounding with bioactive additives proved not to be effective. The subsequent material extrusion and mechanical tests or shape tolerance measurements yielded two different implant strategies: the standard mono-implant made of PETG with a build-up rate of approximately 10 g/h, and the biofunctional hybrid implant with a TPU outer layer and a PETG core with a build-up rate of approximately 4 g/h. The standard implant is meant to be intraoperatively applied, as the print time is below three hours even for larger skull defects. Standard implants proved to be well fitting, mechanically stable and very clean printed. The hybrid implant showed in addition particularly cell-friendly behavior due to the chemical constitution of the TPU shell and great mechanical stability due to the crack-absorbing TPU/PETG combination. This constellation could be used in high-risk patients, but is less suitable for intraoperative actions due to increased manufacturing duration. In summary, filament-based material extrusion has been identified as a suitable manufacturing method for personalized implants in the craniomaxillofacial area. A further clinical study has been recommended.