Evaluation of Mandibular Growth Using CBCT in a Rabbit Model

Objectives: The aim of this study was to describe three-dimensional (3D) remodeling changes resulting from normal growth in a rabbit model using cone-beam computed tomography (CBCT) and image registration techniques. Methods: CBCT scans were taken in three growing New Zealand white rabbits at baseline and fortnightly for eight weeks. Metallic tantalum 1-mm spheres were implanted as bone reference markers. The data sets consisting of rabbit mandibles acquired at different times were segmented, then registered by using different registrations techniques, i.e., rigid, affine, and non-rigid. The registration accuracy was quantified by the maximal of the mean minimum distances and by the Hausdorff distance. Surface meshes were extracted and colour maps were then used to visualise mandibular growth. Results: The mean absolute error for the image registration procedure was 0.4 mm and never exceeded 1 mm. As revealed by 3D growth maps, mandibular growth was consistent in all rabbits and ranged from 0.6 to 5.7 mm. During the study period, vertical ramus growth in the rabbit mandible was more prominent than sagittal and transverse growth, especially at the condyles and the posterior border of the ramus. The proposed method of using CBCT was feasible in evaluating mandibular growth in a rabbit model and the animals coped well with the experimental procedures. Conclusion: 3D evaluation of mandibular growth in a rabbit model using CBCT represents a promising approach to be used in future intervention studies.