Untersuchungen zur Asymmetrie von Ober- und Unterkiefermodellenmit Methoden der geometrischen Morphometrie

Objective: Using methods of geometric morphometrics, the structures responsible for asymmetries in the jaws of adults should be identified and described. Patients and Methods: The study surveyed 242 models of orthodontically untreated adults with a full dentition using a MicroScribe 3DX digitizer. Were selected in the upper jaw 68 measuring points in the lower jaw 73 measuring points of the teeth and apical base. The xyz coordinates were analyzed with MorphoJ 1.01c. The symmetric and asymmetric components were formed by Procrustes transformation, and compared using correlation matrix. The effects of the symmetry and asymmetry-determining factors (principal components analysis, PCA) were visualized by thin-plate splines (TPS). Results: There were symmetrical and asymmetrical components for the upper jaw (Procrustes sum of squares 0.82 to 0.20) and lower jaw (0.84 to 0.23) separated. The correlation matrix showed dependence of the matrices (p = 0.000). In the PCA the first three components showed in the upper jaw a cumulative variance explanation of 49.8% (symmetrical) and 33.7% (asymmetrical) and in the mandible of 46.9% (sym.) and 33.3% (asym.). In TPS the mandibular asymmetric component are visible as lateral movement in the premolar and canine region, in the upper jaw the changes effect mainly the anterior region and the region of the canines. Moreover, the apical base in terms of a transverse asymmetry is altered here. Conclusions: The study showed that methods of geometrical morphometrics have the ability to separate symmetrical and asymmetrical components and quantify their location graphically. There were both quantitatively similar proportions of the jaw asymmetry. Lateral asymmetries seem to be manifest particularly in the canine in both the upper as well as in the mandible. Keywords: geometric morphometrics, orthodontics, dental arch, asymmetry