Comparison of clear aligner mandibular advancement appliance and twin block appliance used in the treatment of class II malocclusion using 3D finite element method

The aim of this study is to compare the effects of the Twin Block and Mandibular Advancement (MA) appliances, which are used in the functional orthodontic treatment of individuals with Class II malocclusion, on the maxillomandibular complex and temporomandibular joint (TMJ) using the three-dimensional finite element method (3D FEM). Due to the different design and force transmission characteristics of each appliance, separate modeling was performed for each. In this context, two different simulation models were created. In the first model, the Twin Block appliance was modeled. On the dental models obtained during the computer-aided modeling process, in the maxilla, the second premolar and first molar teeth; and in the mandible, including all anterior and premolar teeth, the area contacting the occlusal surfaces was designed in three dimensions with a thickness of approximately 4–5 mm. In the literature, it has been reported that the posterior fibers of the temporalis muscle generate an average force of 12 N in the resting position when the mandible is positioned forward. Based on this scientific data, in this study, the mandibular advancement effect of the Twin Block appliance was simulated with a force value of 12 N. In the second model, the MA appliance was used. The MA appliance was modeled in three dimensions using ANSYS SpaceClaim (Version 22.0, Canonsburg, Pennsylvania, USA) to cover all teeth and with an average thickness of 0.75 mm. Since the posterior fibers of the temporalis muscle generate an average force of 12 N in the resting position when the mandible is positioned forward, the force was also taken as 12 N for this appliance. The simulation results showed that the Twin Block appliance resulted in more displacement of the teeth and greater proclination of the lower incisors. In both appliances, distalization of the teeth in the maxilla and mesialization of the teeth in the mandible were observed. In addition, the amount of stress generated in the condyle and disc in the Twin Block simulation reached higher levels compared to the MA appliance. The amount of displacement at maxillary and mandibular bone points was found to be higher in the Twin Block simulation. According to the findings obtained in our study, the dental and skeletal effects of the Twin Block appliance were observed to be greater compared to the MA appliance. KEYWORDS: Twin Block, MA, 3D FEM