[The effects of morphological variation of the spheno-occipital complex to the formation of skeletal facial pattern].

The purpose of this study was first to classify the morphological type of spheno-occipital complex and second to verify the relationship between the type of spheno-occipital complex and skeletal facial pattern. Materials used in this study were latelal cephalograms of 341 Japanese female adults. None of the subjects underwent any orthodontic therapy. Data were evaluated by multivariate analysis. The following results were obtained. 1. By the cluster analysis, the spheno-occipital complex was classified into three types, namely Thick type, Average type, and Slender type. 2. By the principal component analysis, it was shown that the classification was made by the factor of the inclination of posterior cranial base as the first component and the factor of the projection of sphenoidal rostrum as the second component. The Thick type group had less inclined posterior cranial base and more projected sphenoidal rostrum. 3. There was little relationship between mandibular pattern and the spheno-occipital complex. 4. The principal component analysis of the skeletal facial pattern showed that the Thick type group showed skeletal Cl. III tendency and the Slender type group showed skeletal Cl. II tendency, but there was no significant relationship between the vertical skeletal facial pattern and the spheno-occipital complex. In conclusion, the spheno-occipital complex was divided into three type groups according to the inclination of posterior cranial base and the projection of sphenoidal rostrum. It was concluded that the spheno-occipital complex has a close relationship to the skeletal facial pattern and contributes to the facial formation.