Objective: In order to predict the effect of orthodontic treatment on lower third facial soft tissue, a generic 3D Finite Element (FE) Model of the craniofacial soft and hard tissues was built. Individualization of the generic model was tested.
Methods: Spiral CT data of a volunteer with normal occlusion was collected. The data was imported into MIMICS for image filtering to reduce noise and delete redundant part. Different parts of soft and hard tissues were segmented and reconstructed based on varied image density. Then the worked data were imported into ANSYS. 7 pairs of main peri-oral muscles were constructed based on a combination of CT image and anatomical method. The integrated facial FE model included skin, fat, muscles, teeth and skeleton. And the model was meshed into tetrahedral elements. Different parts were defined with specific mechanical properties. Then a patient’s Cone beam CT data were obtained and reconstructed. Based on selected corresponding characteristic landmarks, the generic FE model was transformed into a patient specific one through calculation of the new coordinate of nodes using Radial basis functions (RBF) method.
Results: Average deviation between the transformed model and the real reconstructed one was 0.47±0.77mm and 0.75±0.84mm in the soft and hard tissue respectively.
Conclusion: Patient specific 3D facial FE model including different layers of soft tissue could be obtained through mathematical model transformation. With boundary condition defined according to treatment plan such FE model might be helpful in predicting the result of orthodontic treatment on facial soft tissue in the future.