Digital Model Construction for Finite Element Analysis from CBCT Scans

Objective: A computerized tomography scan produces a compilation of X-ray images from several different angles to assemble a cross sectional grayscale-based image of bones and other soft tissue. Segmentation of the images is necessary to differentiate between different types of bone and tissue and to produce separate 3D digital models of PDL, bone and tooth.  The purpose of this project was to evaluate the feasibility of 3-dimensional segmentation from cone-beam computed tomography (CBCT) scans using the computer program ScanIP. The digital segmentations will be used to produce finite element models to locate the center of resistance of orthodontic buccal segment configurations.

Methods: A CBCT of a maxilla of a dry skull was obtained with the iCAT CBCT system with a resolution of 0.125mm. We utilized the software ScanIP (Simpleware, UK) and segmentation techniques such as floodfill, threshold filters, paint with threshold, and morphological filters to separate PDL, bone and tooth. The maxillary bone, teeth and respective PDLs were assigned their own masks, which are color-coded segmentations that allow for individual 3D rendering.

Results: A 3-dimensional model of four maxillary posterior teeth including bone and PDL was created using ScanIP segmentation techniques from cone-beam CT scans of the maxilla. The distinct tooth and tissue types were separated into different masks. These models will later be used to produce 3D meshes for the finite element analysis of any combination of the four posterior teeth and tissues.

Conclusion: Cone-beam CT scans of maxillary teeth were viably made into 3-dimensional volumetric models by segmentation with ScanIP.  This model can be used for further study with Finite Element Analysis to determine the center of resistance and the mechanical environment around buccal segment structures with different orthodontic loads.