The objective of this study was to conduct a computer assessment of the biomechanical stability of locking fixation plates of different thicknesses, made of titanium alloy and carbon-fiber- reinforced polyetheretherkotone (CFR-PEEK) in Class III atrophic mandibular fractures. Class III atrophic mandibular models were constructed using three-dimensional finite element models. After simulation of fracture on the left side, plates with different thicknesses (1.0, 1.5, 2.0, and 2.5 mm) were adapted to the models and three locking screws on each side of the fracture were used for fixation. Titanium alloy and CFR-PEEK material properties were assessed for all plate models. Von Mises stress values decreased gradually with an increase in plate profile thickness. Von Mises stress values for screws and plates were lower in models using CFR-PEEK plates. An increase in plate profile enhanced the load-sharing performance of the fixation systems, with rigid titanium alloy plates sharing the load among the screws more evenly. 1.0 mm, 1.5 mm, and 2.0 mm CFR-PEEK plates produced strain values of 2-10%, which promote proper healing via formation of callus in the fracture line. In terms of investigated biomechanical parameters, and with a Young's modulus similar to that of cortical bone, CFR-PEEK materials appear to be suitable for the treatment of atrophic mandibular fractures. (C) 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.