Objective <p>The purpose of this study was to investigate the biomechanical behavior of different fixation systems used in advancement genioplasty using finite element analysis (FEA). The study aimed to provide numerical insight into stress distribution and displacement patterns under controlled loading conditions, rather than to evaluate clinical performance or long-term stability.</p> Methods <p>A three-dimensional finite element model of a human mandible was reconstructed from the Visible Human Project dataset. Cortical and trabecular bone, fixation plates, and screws were modeled as homogeneous, isotropic, and linearly elastic materials. Advancement genioplasty was simulated at different advancement distances, and fixation was achieved using various plate configurations. A static horizontal load of 100&#xa0;N was applied to the distal segment. Stress distribution and displacement were evaluated for the fixation devices and surrounding bone structures.</p> Results <p>As advancement increased, principal stress values in cortical and trabecular bone decreased in both L-plate and X-plate models due to increased plate length and material volume. X-plate models consistently produced higher stresses on bone, plates, and screws compared with L-plates. Bicortical screw fixation generated the lowest stress values in bone; however, increasing advancement reduced screw penetration into the proximal segment, increasing local stress concentrations. All plates stresses remained below the material’s yield strength.</p> Conclusions <p>Within the limitations of a simplified, static finite element model, the findings provide comparative biomechanical insight into the mechanical response of different fixation systems used in advancement genioplasty. The results should be interpreted as numerical trends rather than indicators of clinical superiority or long-term stability.</p>