Background <p>This study aims to evaluate, through finite element analysis, the biomechanical changes in three superstructure materials with distinct mechanical and thermal properties during implant-supported reconstruction of maxillary defects using fibular grafts under environmental temperature fluctuations.</p> Methods <p>A model of maxillary defect reconstruction was established using images of a vascularized fibula derived from the Cone Beam Computed Tomography (CBCT) database. The defect spanned from the right central incisor to the left first molar. For the two different implant position designs, independent finite element analysis models were created. Mechanical study models were constructed according to different temperature conditions (0&#xa0;°C and 60&#xa0;°C), prosthetic materials (zirconia, titanium, and polyetheretherketone), and loading modes (intercuspal occlusion, canine-guided occlusion, and group function occlusion), respectively. DICOM data were processed using Mimics Research 21.0, Geomagic Wrap 2021, and SolidWorks 2023 to reconstruct, assemble, and refine the 3D models of the maxilla, fibula, and implant-prosthetic components. Mesh generation for all the parts was performed in Ansys Workbench 2024. A sequential thermal‒stress coupling analysis was conducted to evaluate the mechanical response of the prosthesis under thermal cycling. A cyclic thermal load (0&#xa0;°C and 60&#xa0;°C) was applied as a boundary condition, and the resulting transient temperature field was imported into the structural module as a body load. Subsequently, 25 chewing cycles within a 5-second period were simulated. The von Mises stress and principal stresses in all prosthetic components and bone tissue were assessed. Based on implant distribution, two groups were designed: Group A (implant sites 11, 22, 24, and 26) and Group B (implant sites 11, 23, 24, and 26).</p> Results <p>(1) At the same implant site, the von Mises stress values of the restorations, abutments, implants, and central screws made from all three materials were greater under low-temperature conditions than under high-temperature conditions. (2) Under identical temperature and material conditions, the von Mises stress values for Group A were consistently greater than those for Group B, indicating a biomechanical advantage of canine site placement. (3) Among the three materials, the abutments, implants, and central screws of the PEEK prosthesis presented the highest von Mises stress values, with stress primarily concentrated on the implant. (4) The von Mises stress values in the canine-guided occlusion group were lower than those in the group functional occlusion group.</p> Conclusions <p>Low-temperature environments and material selection significantly influence the mechanical behaviour of restorative systems: stress in restorations made of zirconia is concentrated within the restoration itself, potentially reducing the load on the supporting structures; PEEK, on the other hand, transfers more stress to the implant and abutment; and pure titanium has the most uniform stress distribution. Furthermore, stress is concentrated in the cortical bone neck of the first molar region of the fibular flap, and the use of canine implant sites or canine-protected abutments can reduce overall stress levels.</p>