Simultaneous Reconstruction of 3D Model of Tooth and Alveolar Bone

Objectives: In the treatment planning and simulation of orthodontic treatment, both the three dimensional (3D) model of tooth and alveolar bone are needed. Previous studies mainly focused on the reconstruction of individual tooth, while the reconstruction of alveolar bone was seldom considered. The objectives of this study were to develop an automatic method to reconstruct the 3D model of tooth and alveolar bone simultaneously from CT images, and to evaluate the performance.
Methods: The connected contours of tooth and alveolar bone of each two dimensional (2D) slice are first segmented using a global minimization level set model. The contours of tooth and alveolar bone are separated using a local level set model from the connected contours. Isosurfaces of tooth and alveolar bone are then extracted using the marching cube algorithm from the corresponding contours. Simplification and smoothing of triangular mesh is executed to the isosurfaces to obtain the final 3D model. CBCT images of ten subjects were used to evaluate the performance of the above method. The accuracy of this method was estimated by comparing to the manual segmentation results of experienced clinicians. The Dice similarity coefficient (DSC, %) and average symmetric surface distance (ASSD, mm) were used to evaluate the tooth segmentation accuracy.
Results: (1) 2D contours of tooth were extracted accurately, and the DSC and ASSD of the four types of teeth were higher than 91% and lower than 0.27 mm, respectively. (2) 3D models of tooth and alveolar bone have been reconstructed simultaneously for all tested images. (3) All procedures including the 2D segmentation and 3D reconstruction of tooth and alveolar bone were completed within 15 minutes.
Conclusions: The presented method based on the two level set models segmentation and marching cube reconstruction can be used to reconstruct the 3D model of tooth and alveolar bone simultaneously.