Variations of the gonial angle in vertical surgical reduction of the maxillary-mandibular complex.

From an esthetic point of view, the mandibular or gonial angle plays an important role in ensuring a harmonious facial profile. The purpose of this study was to analyze the values of the mandibular angle in relation to variations of the vertical and sagittal positions of the jaw. The study was carried out on a sample of 42 patients who underwent surgery for maxillary-mandibular repositioning, advancing or raising the jaw, after a Le Fort I osteotomy and bilateral sagittal osteotomy of the jaw according to the technique described by Obwegeser-Dal Pont. In all patients, the maxillary bone was raised with a discrepancy of at least 3 mm between the anterior and posterior portions (favoring the latter) as a result of (clockwise) rotation of the bispinal plane. The data, obtained by means of cephalometric analysis according to the method of Ricketts, showed how changes in the gonial angle differed between patients who require correction of an open-bite and those who do not. In particular, in patients without an open-bite, advancement of the maxilla limited the opening of the angle. Similarly, in patients with an open-bite, the tendency to form an open gonial angle can usually be corrected by the association of advancement of the maxilla whenever possible.