Investigation of stress distributions in prosthesis designs produced with different materials supported by subperiostal implants placed in atrophic total edentulous maxilla using finite element stress analysis method

Aim: This study aimed to evaluate the stress distribution in the implant, surrounding bone, prosthetic framework, and fixation screws of subperiosteal implants constructed with different prosthetic materials using finite element analysis (FEA). Materials and Methods: A custom-designed titanium subperiosteal implant (SI) was modeled based on computed tomography data obtained from a completely edentulous maxilla. The SI was planned as two separate components supported by four fixation points each, engaging the canine and tuberosity regions of the maxilla, and incorporating three abutment posts per component. As the framework materials for fixed prostheses, cobalt-chromium (CoCr), titanium (Ti), polyetheretherketone (PEEK), and zirconia (Zr) were selected. Porcelain was veneered on CoCr and Zr frameworks, while porcelain and acrylic resin were used for Ti frameworks, and composite resin was applied over the PEEK framework. A vertical load of 100 N was applied to the anterior region of the prosthesis, along with a combination of 150 N vertical and 100 N oblique (30°) forces to the posterior region. Resulting stress distributions in the implant, prosthetic framework materials, surrounding bone, and fixation screws were analyzed using the finite element analysis (FEA) method. Results: According to the results of the FEA, the highest stress levels in cortical and trabecular bone, implants, and fixation screws were observed in the PEEK framework, while the lowest stress levels occurred in the CoCr framework. Among the prosthetic substructures, the highest stress was recorded in the CoCr framework (103 MPa), whereas the lowest was found in the PEEK framework (70 MPa). Titanium-acrylic resin and titanium-porcelain combinations exhibited similar stress distributions, indicating that the elastic modulus of the veneering material did not significantly influence the stress pattern. Among the prosthetic components, the highest stress concentration was recorded in the prosthetic screw of the PEEK framework, reaching 233 MPa. Stress levels in the implant screws were lower compared to the prosthetic screws, with a maximum value of 71 MPa observed in the PEEK-based prosthesis. The stress values obtained in all models remained within the physiological limits for bone, implants, and prosthetic components. Conclusions: In fixed prosthetic designs supported by subperiosteal implants with different framework materials, the distribution of stress on the jawbone, implant, and prosthetic components exhibited variability. The success of implant-supported prostheses is considered to be directly associated with the selection of a substructure material appropriate for the clinical condition. Rigid framework materials such as CoCr, Zr, and Ti demonstrated lower stress distributions in the bone, implant, and fixation screws compared to PEEK, thereby offering biomechanical advantages. Furthermore, the findings suggest that in the planning of subperiosteal implant treatments, not only the choice of framework material but also the mechanical durability of the screw components should be taken into consideration.