Three-dimensional Finite Element Analysis Of Maxillary Skeletal Expander And Surgically Assisted Rapid Maxillary Expansion

Objective:The purpose of this study was to evaluate the biomechanical effect of RME with different therapies including surgically assisted rapid maxillary expansion and Maxillary skeletal expander,and defining the same load conditions for adult by using a 3D FEM.It can be used to guide clinical practice and provide theoretical basis for the selection of treatment methods for adult in clinical.Materials and methods: A three-dimensional finite element model of the skull and maxilla is established by using spiral CT scanning,Mimics,Solidworks and Abaqus software.On the basis of this model,the position of the osteotomy line is set at the mid-palate suture,the osteotomy position was broken,and the traditional Hyrax expander is assembled to establish the model of the surgically assisted rapid maxillary expansion.Meanwhile,Maxillary skeletal expander is assembled on the basic model as the model of MSE group.The forced lateral displacement of 5mm along the X axis is applied to simulate the clinical application.The X-axis displacement,Y-axis displacement and z-axis displacement of each point are calculated respectively under the loading condition of the two models,so as to evaluate the stress distribution and displacement trend of the maxilla and teeth under the orthodontic load.Results: The maximum stress of surgically assisted rapid maxillary expansion is located in the frontal process of maxilla,followed by the buccal alveolar of anchorage teeth.The maximum stress of MSE group is located in the area around the implant,followed by the buccal alveolar of teeth,and the stress value is greater than that of the surgically assisted rapid maxillary expansion.Cross-sectional,the open amount of palatal in the operation group is nearly consistent.In MSE group,the palatal opened more in the posterior and less in the anterior;On the coronal section,from the alveolar bone to the base of the skull,the open volume of the operation group presented a "pyramid" shape,but the difference between the upper and lower is small.The maxilla and teeth of the two models show a tendency of forward in sagittal direction.In the vertical direction,the maxilla and teeth have a downward movement trend in the surgically assisted rapid maxillary expansion group,while the maxilla and teeth of the MSE group have an upward movement trend.The first premolars and the first molars in the two groups show coronal buccal and root lingual oblique displacement,and the degree of buccal inclination of the first premolars in surgically assisted rapid maxillary expansion group was larger than that in the MSE group.The maximum of osseous expansion effect in the surgery group was 80.2%,and that in the MSE group was 70.4%.Conclusion:(1)It is feasible to use spiral CT tomography,Mimics,Solidworks and Abaqus software to construct the 3D finite element model of maxillary.The model provides a reliable basis to the biomechanical study of the jaw.(2)In the MSE group,the maxillary posterior teeth could be pushed vertically upward,which alleviate the adverse tendencies of buccal inclination,palatal apical droop of the posterior teeth.And the mandibular plane shows a counterclockwise rotation trend.It is beneficial to control the vertical dimension of patients with high mandibular angle.(3)The new MSE can approach the bone effects of surgically assisted rapid maxillary expansion,but it does not completely eliminate the effect of teeth.For adults,Using MSE can partly replacement surgery for the correction of maxillary transversal deficiency.