Evaluation of rapid maxillary expansion with hybrid appliances with and without corticotomy by using finite element analysis

In this in-vitro study, it was aimed to investigate the stress distribution and amount of displacement on craniofacial structures of rapid maxillary expansion (RME) treatment using hybrid appliances with and without corticotomy by finite element analysis. In our study, a 3-dimensional finite element model of craniofacial bones and maxillary teeth were obtained using cone beam computed tomography images of a 22-year-old female patient having maxillary transverse deficiency, in the archieve of Department of Orthodontics, Faculty of Dentistry, Gaziantep University. On this model, three different RME models were designed, as hybrid hyrax supported with palatal bone by two mini-screws and reinforced with two molars (Type A), corticotomy assisted hybrid hyrax supported with palatal bone by two mini screws and reinforced with two molars (Type B), and corticotomy assisted traditional tooth-supported hyrax (Type C). In models, the hyrax screw is activated at least 0.25 mm in the transversal direction. At the end of the study, more transversal movement was observed on the models in Type B and Type C models with corticotomy compared to the Type A model. The amount of tipping in the posterior teeth was greater in Type A model, and higher stress was observed around the mini screws in this model than other models. In addition, in Type B model, the rotation of the maxillary plates was limited due to the mini screws, and more parallel transversal expansion was obtained. As a result, Types B and C models showed more transversal expansion in the anterior region according to Type A model. Rotation of the maxillary plates was less common in Type B model. As a conclusion; a more parallel and more effective transversal expansion was achieved on models with the mini-screw supported and corticotomy applied hybrid hyrax expansion appliance. Besides, surgically assisted RME could be recommended in adults. Key words: Corticotomy, finite element analysis, hybrid appliance, maxillary transverse stenosis, rapid maxillary expansion.