Objective: This study aimed to examine the biomechanical effects of the fixed functional appliances reinforced with miniscrews by finite elements analysis over the cranial and facial bones, temporomandibular joint, and maxillary-mandibular teeth, which are used for the treatment of Class II division 1 malocclusions characterized as mandibular retrognathia.Methods: Three-dimensional (3-D) models of the cranial, mandibular, and maxillary bones were purchased from a company that produces 3-D models of the bones. Simulations of Forsus, screwed Forsus, Twin-Force and screwed Twin-Force appliances were conducted on the 3 D models. The miniscrew was placed in the inter-radicular area between the upper canine and first upper premolar teeth.Results: It was observed in the models that the first upper molar tooth was the most affected. The compressive stress was observed in the anterior area of the mandibular condyle neck in the Forsus appliances; however, it was observed in the posterior area of the mandibular condyle neck in Twin-Force appliances. Conclusion:It was observed that molar distalization and expansion decreases in the functional appliances with the support of miniscrew. The highest tension rates were determined in the areas of condylar and articular discs.