[Investigation of the facial symmetry of cases with cross bites needing surgical orthodontic treatment using postero-anterior roentgenographic cephalometrics].

Of the patients who visited the Dental Hospital (Orthodontic Treatment Section), Nihon University School of Dentistry at Matsudo, and received surgical orthodontic treatment for mandibular protrusions (true Class III), 30 (12 with cross bite and 18 without) were selected as study subjects. Postero-anterior roentgenographic cephalometrics were taken of these subjects and, based on these cephalograms, facial symmetry was investigated using an analytical method devised by this study. The results can be summarized as follows. 1. The analytical method is beneficial because it provides a standard for analyzing facial symmetry and it helps to determine if a given part of the face is symmetrically disposed. 2. In this study, the facial symmetry of the cases with cross bites tends to become worse in lower part of the face. This tendency is especially apparent below the plane (JL-JR plane) connecting the intersection where the contour lines of right and left maxillary tuberosities meet the zygomatic alveolar crests. 3. I concluded that surgical orthodontic treatment should be different for cases with cross bites than for those without. For cases without cross bites surgical treatment can be properly planned depending mainly on paper surgery using lateral roentgenographic cephalometrics. For cases with cross bite, however, paper surgery should first be done separately for right and left mandibles using lateral roentgenographic cephalometrics, and paper surgery based on postero-anterior roentgenographic cephalometrics should follow. Finally, combining the results from those three types of paper surgery, overall paper surgery should be done to finish a proper and comprehensive surgical plane.