A foundation for cephalometric communication

Abstract I felt a need for a restatement of the objectives of so-called cephalometric analysis. The semantics of terms were discussed to familiarize the reader with survey, analysis, and synthesis as applied in this study. One thousand cases were studied in an effort to establish a knowledge of the most common orthodontic problems and the variation of more infrequently occurring problems. A system of five measurements from x-ray tracings was designed to provide a sensible method of informing the orthodontist of facial form and denture position. The five measurements were (1) the facial angle, (2) the XY axis angle, (3) the measure of contour, and (4 and 5) the relationship of the upper and lower incisors to the APo plane. These angles and measurements proved to be indicators of facial depth, facial height, and profile contour. Classification by assigning numerical limits of the denominators for chin location made for an easier and more informative communication of problems. Thus, the cephalometric x-ray was shown to provide a description, a comparison, a classification, and a communication of existing conditions. Certain classifications were thus proposed for future semantic purposes. The teeth were measured from the denture bases rather than to points outside the dental areas. The position of the lower incisor in relation to the APo plane was thought to be the key to communication of the problems with the anterior teeth. Thus, a line from point A to pogonion was described as the denture plane. Age changes in position of the lower incisor, facial contour, and lip relations were studied from a cross-sectional viewpoint. The average convexity decreased consistently from the deciduous dentition age to the full adult dentition age. At the same time, the lips became progressively more retracted in relation to the esthetic plane. However, the relationship of the lower incisor to the APo plane tended to be similar in the age samples studied. A system for deep structural analysis was proposed for those cases in which more detailed information is desired. This included the length and angulation of the cranial base, the location of the glenoid fossa and the condyle head, the angulation of the condyle neck to the cranial base, and the mandibular plane angle. The analysis of the nasopharynx was also employed in cases with cleft palate, speech, or breathing problems or other problems near the coronal suture complex area. I stressed the need for the concept that a survey or analysis was for the purpose of describing and understanding skeletal proportion and form. Treatment planning constitutes a separate subject embodying the factors of growth, tooth movement, and changes in function. That subject—cephalometric synthesis—should be dealt with separately.