[The validity of the degrees of asymmetry in computer-supported analyses of the frontal x-ray image]

The aim of the study presented here was to evaluate the efficacy of symmetry indices when using a specially adapted computer aided mandibular analysis of symmetry degree (CMS). By means of using a series of anteroposterior cephalograms with experimentally simulated rotations and tippings of the two mandibles under study (one ideal symmetric, one severe asymmetric), it proved possible to quantify significant distortions in the degree of symmetry. It was possible to demonstrate that the determination of percentual symmetry degree is a helpful diagnostic tool in the case of skeletal mandibular asymmetry. In the two-dimensional projections of posteroanterior cephalograms, however, computer aided differential analysis of the functional and skeletal components of asymmetry were not shown to be valid. This finding can thus be generally applied to all exclusively posteroanterior cephalogram related symmetry indices.