Biomechanical effect of implant thickness and screw diameter on CFR-PEEK subperiosteal implants: a three-dimensional finite element analysis

Objectives: The aim of this study is to evaluate the effects of subperiosteal implant framework thickness and screw diameter on the biomechanical behavior of patient-specific subperiosteal implant systems made from 60% Carbon Fiber Reinforced Polyetheretherketone (CFR-PEEK) using three-dimensional finite element analysis (FEA). Materials and Methods: Four three-dimensional FEA models were constructed using a single patient-specific maxillary geometry derived from computed tomography (CT) data in these models, two implant framework thicknesses (T:1.0 mm and 1.5 mm) and two screw diameters (SD: 1.5 mm and 2.0 mm) were analyzed in combination using 60% CFR-PEEK biomaterial. Three loading scenarios were simulated: (1) Bilateral 150 N perpendicular force to the buccal cusp tips of the first and second premolars and the first molar, (2) Unilateral 100 N oblique force at a 30° angle from buccal to palatal to the same areas, and (3) Bilateral 150 N perpendicular force to the central and lateral incisors. Total displacement values, maximum and minimum principal stresses in the bone; Von Mises stresses in the bone, subperiosteal implant, abutment, and metal framework were evaluated. Results: Increasing the subperiosteal implant framework thickness was found to reduce stresses that were particularly elevated in the posterior maxillary region under various loading conditions, while simultaneously increasing the stresses on the subperiosteal implant and metal framework. Increasing the screw diameter decreased the stresses on both the bone and implant, but resulted in higher stress concentrations within the metal framework. The 60% CFR-PEEK material with a high elastic modulus reduced stresses in the bone, but the concentration of applied loads in the implant body and metal framework led to higher stress values in these structures. Conclusion: Subperiosteal implant framework thickness, screw diameter, and material stiffness appear to have a significant influence on stress distribution and overall stability in subperiosteal implant systems. Although this study is limited to finite element analysis, the findings suggest that CFR-PEEK based designs may satisfy the essential biomechanical requirements for clinical application.