Three-dimensional mandibular regional superimposition in growing patients

Introduction: The aims of this study were to identify stable mandibular structures in 3 dimensions in growing patients using a regional implant technique and to test the reproducibility of mandibular regional superimposition in 3 dimensions using the regions identified. Methods: Three-dimensional voxel-based regional mandibular registrations were performed on bone plates, and screws were placed in the anterior chin and symphysis regions of 20 growing patients (mean age, 12.1 +/- 1.3 years). Three-dimensional models of the resulting superimpositions were built for the chin, symphysis, and third molar crypts. Absolute mean errors were calculated for each region to evaluate stability. Longitudinal cone-beam computed tomography scans were obtained of 25 patients (mean age, 12.7 +/- 1.4 years) with different skeletal malocclusions (20 Class II, 5 Class III). To evaluate reliability of mandibular registrations using the chin and symphysis regions, voxel-based superimpositions were performed independently by 2 observers. The resulting superimpositions between the 2 examiners were overlaid, and the mean difference along the entire surface of the mandible was calculated. Results: The chin and symphysis regions showed high levels of precision (chin absolute mean error, 0.37 +/- 0.16 mm; symphysis absolute mean error, 0.4 +/- 0.15 mm). The third molar region had a high registration error (absolute mean error, 1.94 +/- 0.06 mm). The voxel-based registrations using the chin and symphysis were reliable and reproducible between examiners (absolute mean error, 0.12 +/- 1.1 mm). Intraclass correlation coefficient results showed a high degree of agreement between examiners. Conclusions: The chin and symphysis regions are stable areas for 3-dimensional mandibular regional superimpositions.