Comparative Stress Analysis of Maxillary Implant Prostheses With Different Retention Designs and Restorative Materials

Introduction: Implant-supported restorations are widely used to replace missing teeth; however, their long-term success depends largely on the biomechanical behavior of the implant-prosthesis complex. This study aimed to evaluate and compare stress distribution patterns in maxillary implant-supported restorations with different retention methods and crown materials under axial and oblique loading conditions using three-dimensional finite element analysis. Materials and methods: A three-dimensional finite element model of a partially edentulous maxillary premolar region was constructed. A titanium dental implant with an abutment was positioned vertically within the cortical and cancellous bone. Four restorative configurations were analyzed: cement-retained porcelain-fused-to-metal, screw-retained porcelain-fused-to-metal, cement-retained zirconia, and screw-retained zirconia crowns. All materials were assumed to be homogeneous, isotropic, and linearly elastic. Two loading conditions were simulated: a vertical axial load of 100 N applied along the implant axis and an oblique load of 100 N applied at 30° to the implant axis. von Mises stress distribution was evaluated in the crown, abutment, implant, prosthetic screw, and surrounding bone. Results: Cement-retained restorations demonstrated a more uniform stress distribution than screw-retained restorations, particularly at the implant-abutment interface. Porcelain-fused-to-metal crowns exhibited relatively lower stress concentrations in prosthetic components than zirconia crowns. Oblique loading generated higher stress values than axial loading in all models, with maximum stresses localized at the implant neck and the crestal cortical bone. Conclusion: Within the limitations of this finite element study, cement-retained porcelain-fused-to-metal restorations exhibited more favorable biomechanical behavior in the maxilla than screw-retained titanium-based restorations. The results highlight the importance of retention type, restorative material, and occlusal loading direction in achieving optimal implant-supported restoration performance.