Three-dimensional mandibular regional superimposition in growing patients

•Three-dimensional voxel registrations were performed in the mandible.•The anterior contour of the chin and the inner cortical plate of the symphysis are stable regions for registration.•The lower contour of the third molar crypt is not as stable as the chin or symphysis.•Registration using the combined chin and symphysis region is reliable. IntroductionThe 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.MethodsThree-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.ResultsThe 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.ConclusionsThe chin and symphysis regions are stable areas for 3-dimensional mandibular regional superimpositions.