Comparative numerical finite element analysis of tooth–implant- versus implant–implant-supported three-unit fixed prostheses under oblique loading

To investigate the biomechanical performance of fixed dental prostheses supported by either tooth-implant or implant-implant configurations, fabricated from zirconia or polyetherketoneketone (PEKK), under oblique loading using three-dimensional finite element analysis (FEA). Three mandibular posterior models were developed: M1 (implant at the first molar and natural tooth at the first premolar), M2 (implant at the first premolar and natural tooth at the first molar), and M3 (implants at both the first premolar and first molar). Each model was restored with a three-unit prosthesis fabricated from either zirconia or PEKK. The digital workflow included anatomical segmentation using Mimics software, refinement of bone and soft tissues with 3-Matic software, and integration of implants, abutments, and prosthetic components, followed by meshing and FEA using ANSYS software. All models were subjected to oblique loading of 50 N at 30° and 45°, and von Mises stress and deformation were recorded. M3 exhibited the most favorable biomechanical behavior, showing the lowest von Mises stress across almost all components. The hybrid tooth-implant models (M1 and M2) showed higher stress concentrations, particularly M2 with PEKK (loading angle 45°), which recorded the highest implant stress (312 MPa) and the greatest deformation (75 µm). The highest screw stress was recorded in M1 with PEKK, reaching 483 MPa. Zirconia exhibited higher stress within the prosthesis, but lower deformation, whereas PEKK resulted in greater deformation in the tooth and periodontal ligament (PDL). Implant-implant-supported prostheses showed the most favorable biomechanical behavior under oblique loading. Tooth-implant models, especially with anterior implant placement, exhibited higher stress and deformation. Zirconia offered greater rigidity and dimensional stability, while PEKK provided better stress dissipation but required careful design to manage its flexibility.