Finite Element Analysis Model for Assessing Expansion Patterns from Surgically Assisted Rapid Palatal Expansion

SARPE is commonly used for maxillary expansion in skeletally mature patients. However, asymmetric expansion has been reported with unknown etiologies. This study aims to develop a novel FEA model of SARPE that can truly mimic the clinical conditions, and to investigate the expansion patterns of the hemimaxilla in all three dimensions.

Finite element analysis has been used in the dental and bioengineering field to allow in vitro simulation of surgeries, such as SARPE. In this study, four software were utilized to set up the FEA model and to predict expansion pattern. The most challenging part which most previous studies link is to simulate forces at the wound healing site across osteotomy surface.

To achieve this, springs were set in our pilot study, and is considered a novel design for SARPE FEA. This unified element model focused on expansion pattern, making a more realistic SARPE simulation through osteotomy gap creation and experience inclusion. It presents significant potential as a clinical tool for branding and its guiding SARPE procedures.

Our interdisciplinary group will work diligently to develop cutting-edge 3D models that can provide valuable insights into personalized treatment strategies to analyze and improve orthognatic surgical technique by utilizing an engineering-assisted approach, and to improve communication and collaboration between orthodontists and oral maxillofacial surgeons through engineering-assisted 3D imaging system. To begin, launch the SolidWorks software to create a one-millimeter-thick plane from the piriform aperture towards the infrazygomatic crest. Now, open the Insert menu, then click on Reference Geometry and Plane options.

From the osteotomy plane, select three feature points, and click Okay to create the O1 plane. Navigate to the plane again by clicking on Insert and Reference Geometry. This time, choose the osteotomy plane and set an offset distance of one millimeter.

Click Okay to create a lower cutting plane marked O2.Now, navigate to Split by selecting Insert, followed by Features, and choose the O1 and O2 planes in Trim Tools. Select the target bodies, and press Cut Bodies to create a cutting preview. Next, tick the check boxes in the Resulting Bodies section, and press Okay to separate the maxillary complex.

Then click on the body between the O1 and O2 planes. Right-click and press Delete under the Body section. To export the models with different buccal osteotomy angles, first click on File, then Save As, and choose Parasolid XT from the file type list.

Finally, click Save to export the models for finite element analysis software. The demonstrated analysis used the cone beam computed tomography image of a 47-year-old female with maxillary deficiency to generate a model. For accurate surgery simulation, the nasal septum, lateral nasal cavity walls, and pterygomaxillary fissure were separated.

To begin, launch the Ansys software to import the material parameters of the maxillary complex model into the software. Next, click and drag the Static Structural in the toolbox to create an analysis workspace. Double-click on Engineering Data, followed by Linear Elastic under Toolbox, and set the Young's modulus and Poisson's ratio for all the materials in Properties.

Now, double-click on Geometry, followed by File. Then select Import External Geometry File and click Generate to import the maxillary complex model. Then click Create, followed by Boolean, and generate the cortical and periodontal ligament boolean with cancellous bone and teeth.

To set up the finite element analysis model, double-click on the model, then select Geometry to determine the material properties for each part. Next, right-click on Mesh, and press Generate Mesh to build the model elements. Now, click Connections and assign the soft or small part in Contact Bodies, and the stiff or large part in Target Bodies.

Then assign the contact type and friction coefficient in Definition. Next, right-click Connections and select Insert. Then press Spring to connect the upper and lower parts of the osteotomy plane.

Set the springs to one millimeter length with a spring constant k set at 60 newtons per millimeter. Place one spring at each grid node. After setting a clinically-acceptable force along the x-axis, right-click the Static Structural option.

Press Insert, followed by Fixed Support to render the structure on the palatal plane as immovable. To apply force on the acrylic plate away from the media line, click on Static Structural, then Insert, and set the force to 150 newtons. Then right-click Solution, followed by Insert, Deformation, and Total to monitor the expansion deformation.

Finally, to carry out a convergence test, select Solve in the toolbars, and wait until the force convergence level reaches the force criterion. Then click on Solution Information, followed by Total Deformation to display the expansion results. The demonstrated model used the cone beam-computed tomography image of a 47-year-old female with maxillary deficiency to create a model.

For accurate surgery simulation, the naval septum, lateral nasal cavity walls, and pterygomaxillary fissure were separated. A preliminary test performed on both the left and right sides of the model with symmetric zero degree cuts showed that 150 newtons of force caused more than eight millimeters of expansion. Additionally, a variety of angles were built to mimic different clinical conditions.

The right and left expansions were visible as a before and after color map of the maxilla models.