Investigation of the role of midpalatal and circummaxillary sutures in bone-anchored rapid maxillary expansion using a verified finite-element model

Introduction: This study aimed to verify a finite element (FE) model for bone-anchored rapid maxillary expansion. In addition, the stage of ossification of the midpalatal and circummaxillary sutures and their impact on expansion were analyzed. Methods: Six patients were treated for maxillary transverse deficiency using the maxillary skeletal expansion appliance in an in vivo study. Preexpansion and postexpansion cone-beam computed tomography images were superimposed to analyze the expansion pattern of the midpalatal suture and maxilla displacement. In FE stimulation, the material property of the midpalatal suture was verified using a simple model, and the impact of 3 surrounding sutures was evaluated using a 3-dimensional skull model. Results: All patients demonstrated a parallel pattern of expansion in the midpalatal suture, with the movement of the maxilla in an upward and forward direction. In the FE simple model, the maximal reaction force on the expander was significantly decreased to the values approximated to the clinical findings when Young's modulus of the midpalatal suture was 0.15 MPa and ν was 0.1 or 0.3. Three different deformation patterns were observed in the skull model when the settings of the 3 surrounding sutures were assigned with various ossification stages. Conclusions: The material properties of the midpalatal suture play a crucial role in determining the reaction force on the expander. The ossification stage or the assumptions of material properties in surrounding sutures has a decisive influence on the expansion pattern of bone-anchored rapid maxillary expansion.