Terletskyi R. Clinical and Experimental Justification of Patient-Specific Endoprostheses for Alloplastic Temporomandibular Joint Replacement

According to recent scientific studies, prolonged functioning of temporomandibular joint (TMJ) endoprostheses and other joint replacements (hip, knee) leads to the formation of wear debris due to friction. These debris consist of microparticles of the materials from which the endoprosthesis components are made. Upon migration into soft tissues, these particles may potentially provoke an inflammatory response and stimulate unpredictable tissue scarring, ultimately reducing the functional outcome of treatment in the long term. Considering the complex anatomy of the TMJ and the significant load it endures during function, there is a pressing need to develop an algorithm for optimizing the design of patient-specific, two-component endoprostheses, as well as methods for their application in TMJ pathology treatment, taking into account etiological and clinico-anatomical features. This dissertation scientifically substantiates and practically addresses an urgent issue in maxillofacial surgery—the improvement of total TMJ replacement efficiency by increasing the accuracy and predictability of surgical interventions, reducing postoperative complications, and enhancing both short-term and long-term functional outcomes. These goals were achieved through the introduction of advanced patient-specific, two-component endoprostheses with a titanium-PEEK articulating pair, manufactured using CAD/CAM technologies. The proposed new material for the artificial glenoid fossa demonstrated superior clinical, biological, and physicomechanical properties compared to traditional titanium-UHMWPE endoprostheses. At the initial stage of research, experimental bench studies with prolonged cyclic loading of 1 million cycles revealed that the wear of the artificial PEEK glenoid fossa was 1.57 times lower by mass and 2.2 times lower by volume compared to the UHMWPE glenoid fossa. During friction between articulating surfaces of titaniumPEEK and titanium-UHMWPE, wear debris were formed, consisting of polymer particles ranging in size from <0.1 µm to 100 µm. These particles had rounded, granular, plate-like, and needle-like shapes and were capable of forming aggregates and complexes of varying sizes and morphologies. The total number of particles generated under cyclic loading for UHMWPE was 2.84 times greater than for PEEK (1.02×10⁹ vs. 0.36×10⁹).