Investigation of the effects of different expansion appliances and surgical incisions on maxillary expansion by finite element analysis

Objective: In orthodontics, the rapid maxillary expansion protocol is used to treat skeletal transversal stenosis of the maxilla, which allows the separation of the midpalatal suture by means of a force transmission that exceeds the physiological limit. In adults, the surgically assisted rapid maxillary expansion (SARPE) protocol is routinely used to avoid the side effects of expansion. In recent years, the miniscrew-assisted rapid maxillary expansion (MARPE) protocol has been used as an alternative protocol to SARPE. The aim of this study was to evaluate the effects of different surgical techniques and three different expansion appliances on maxillary expansion in adults using finite element analysis (FEA), focusing on maxillary displacement and stress on surrounding structures. Materials and methods: Seven models were created using ANSYS software to compare different surgical approaches to MARPE, SARPE, and three different expansion appliances. Model I is the MARPE expansion appliance, which is supported with miniscrews without surgical assitance. Model II, Model III and Model IV are SARPE models without pterygomaxillary suture (PMS) separation. Model V, Model VI and Model VII are SARPE models with PMS separation. Results: In the models without PMS separation, there was an increase in displacement along the z-axis from the second molar to the central incisor, whereas in the models with PMS separation, an equal amount of displacement was found in all teeth. In all models, the amount of displacement along the z-axis was greater in the medial pterygoid process than in the lateral pterygoid process. According to the stress analysis, the highest stress was observed in Model I. Conclusion: The stress values were significantly higher in the miniscrew region of the MARPE model. The various appliance designs showed near zero stress levels in the PMS separated SARPE models. The MARPE model showed a transversal and upward rotation of the maxilla. In SARPE models without PMS seperation, a 'V' shaped expansion pattern was observed in the maxilla. In contrast, a parallel expansion pattern in the maxilla was observed in the models with PMS separation. Keywords: Finite element analysis, Miniscrew assisted rapid maxillary expansion, Palatal expansion techniques, Pterygomaxillary suture, Rapid maxillary expansion This study has been approved by the Başkent University Medical and Health Sciences Research Board (Project no: D-KA23/02) and funded by the Başkent University Research Fund.