Masahito Maeda

Reproducibility of maxillofacial anatomic landmarks on 3-dimensional computed tomographic images determined with the 95% confidence ellipse method.

OBJECTIVE To assess the plotting reproducibility of landmarks on 3-dimensional computed tomography (3D-CT) images through use of the 95% confidence ellipse in order to propose sufficiently stable coordinate systems for 3D-CT measurements. MATERIALS AND METHODS Six dentists plotted 19 landmarks twice on 3D-CT images. Scatterplots and the 95% ellipses were produced 3-dimensionally, and the areas of the ellipses were calculated for evaluating the reproducibility of landmarks. RESULTS The plotting reproducibility of each landmark showed characteristic features. Among five landmarks (the sella [S], nasion [N], basion [Ba], orbitale [Or], and true porion [Po]) that are frequently used as reference points on cephalograms, Ba showed the smallest areas for all three coordinate axes, indicating high reproducibility. The coronoid process (CP) and the tooth-related landmarks showed relatively high reproducibility. CONCLUSION Sufficiently stable coordinate axes could be proposed for different treatments and studies.

Changes in skeletal asymmetry after sagittal split ramus osteotomy for patients with mandibular prognathism: three-dimensional computed tomographic assessment

ObjectivesWe evaluated the clinical utility of a three-dimensional computed tomography (3D-CT) system to assess changes in the symmetry of patients undergoing sagittal split ramus osteotomy (SSRO) for mandibular prognathism.MethodsNine patients who underwent SSRO for mandibular prognathism were analyzed before and after their treatment using a 3D-CT system that we developed for evaluating maxillofacial skeletal asymmetry. Asymmetry indices for selected landmarks were calculated before and after treatment and compared with those of normal controls. Three regions were assessed: the maxillary, mandibular body, and mandibular ramus regions. Based on these regional assessments before and after treatment, changes in asymmetry types were determined for each patient.ResultsThe asymmetry index was frequently improved for tooth-related landmarks, whereas no changes were observed in the anterior nasal spine, orbitale, or porion. In the maxillary and mandibular body regions, all nine patients showed improvement or no change in asymmetry. Deterioration was observed only in the mandibular ramus region of three patients who had preoperative asymmetry in the maxillary region.ConclusionOur 3D-CT system is effective for postoperative evaluation of facial asymmetry in patients with mandibular prognathism.