Biomechanical Impact of Implant Thickness and Screw Diameter on Patient-Specific CFR- PEEK Subperiosteal Implants: A Three-Dimensional Finite Element Analysis

Objectives: The aim of this study is to evaluate the effects of implant thickness (1.0 mm and 1.5 mm) and screw diameter (1.5 mm and 2.0 mm) on the biomechanical behavior of patient-specific subperiosteal implant systems made from 60% Carbon Fiber Reinforced Polyetheretherketone (CFR-PEEK) material 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 thicknesses and two screw diameters were analyzed in combination using 60% CFR-PEEK biomaterial. Three loading scenarios were simulated: (1) Bilateral 150 N perpendicular force to the buccal tubercles 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. Von Mises stresses in the bone, subperiosteal implant, abutment, and metal substructure; maximum and minimum principal stresses in the bone; and total displacement values ​​were evaluated. Results: Increasing the implant thickness from 1.0 mm to 1.5 mm reduced the stresses in the bone tissue while increasing the stress values ​​accumulated on the subperiosteal implant and metal substructure. Increasing the screw diameter from 1.5 mm to 2.0 mm reduced the stresses on the bone and implant but increased the stress concentration in the metal substructure. 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 substructure led to higher stress values ​​in these structures. Conclusions: Implant thickness, screw diameter, and material stiffness have a decisive effect on stress distribution and stability in patient-specific subperiosteal implant systems. Optimizing these parameters requires considering the stress reduction in bone tissue while also addressing potential stress increases in the implant and prosthetic substructure. Clinical Relevance: This study demonstrates that CFR-PEEK is biomechanically feasible as an alternative biomaterial to titanium in patient-specific subperiosteal implants. Increasing implant thickness and screw diameter was found to enhance stress distribution and support implant stability in severely atrophic maxillae. However, the elevated stress values observed within the implant body indicate that the success of subperiosteal implants depends not only on surgical execution but also on surgeon-driven, patient-specific digital design optimization.