Cephalometry without complex dedicated postprocessing in an oriented magnetic resonance imaging dataset: a pilot study.

OBJECTIVES: Magnetic resonance imaging (MRI) enables a 3D-volume-imaging without ionizing radiation. Therefore, it was the aim of this study to present a post-processing-free method for cephalometric analysis of a MRI-dataset and to examine whether there is a significant difference between cephalometric analysis of conventional 2D cephalograms and MRI scans. METHODS: One MRI scan each was performed on three cadaver heads using a 3T-MR-scanner. Cephalometric analysis was conducted directly on the 3D dataset. All reference points were projected onto a virtual sagittal plane that was perpendicular to the Frankfort horizontal plane. Double-sided points were averaged. Cephalometric angles were measured from the projected points. Results were compared with cephalometric measurements on conventional lateral cephalometric radiographs (LCRs). The cephalometric analysis was performed by five raters. RESULTS: 390-angle measurements were obtained. The inter-rater reliability was high [intraclass correlation coefficients (ICCs) ≥ 0.74 for all angles]. Differences between the measurements on the cephalograms and MRI scans ranged between -0.91° (-1.88°, 0.07°) and 0.97° (-0.63°, 2.57°) on average and were equivalent with respect to a margin of [-2°, 2°] in all angles except L1-Me-Tgo (Bonferroni-Holm-corrected P < 0.05 in all angles except L1-Me-Tgo). The best match was found for the SNA angle. CONCLUSION: The clinical comparability of the MRI- and LCR-based cephalometry could be stated. Using MRI in orthodontics would reduce radiation exposure and the risk of stochastic radiation damage, which is of importance especially in younger patients.

Can different occlusal positions instantaneously impact spine and body posture? : A pilot study using rasterstereography for a three-dimensional evaluation.

PURPOSE: Orthodontists influence dental occlusion directly. To suggest any link between dental occlusion and body posture is highly contentious, as evidenced by the literature. Rasterstereography, an optical technique that enables three-dimensional (3D) body measurements to be collected, has not yet been used to impartially examine whether different occlusal positions could instantaneously alter spine and body posture. We therefore set out to use this technique to nonsubjectively evaluate this question under static conditions. METHODS: Optical body scans were collected for 44 subjects, using the Diers formetric 4D system, for seven different mandible positions. In total, ten spinal and body posture parameters were assessed (trunk inclination, trunk imbalance, pelvic tilt, pelvic torsion, fleche cervicale, fleche lombaire, kyphotic angle, lordotic angle, surface rotation, and lateral deviation) for each mandible position and compared with scans performed with habitual intercuspation (HIC). RESULTS: Significant body posture deviations were found for the fleche cervicale (position of the mandible: right eccentrically), fleche lombaire (positions of the mandible: physiologic rest position, cotton rolls on both sides, bite elevation 1 mm), and the kyphotic angle (positions of the mandible: cotton rolls on both sides, right eccentrically). No other significant differences were detected. CONCLUSIONS: Data for the parameters that varied with different dental occlusions generated high standard deviations. Therefore, within the limitations of this pilot study, we could not conclusively associate dental occlusion to an instantaneous impact on the tested parameters. The posture changes that we detected could also have arisen from individual neuromuscular compensation; a possibility that must now be ruled-in, or out, by further research studies with a higher number of subjects.