A roentgenographic cephalometric analysis of cephalo-facio-dental relationships

Abstract

1. 1. This article is a contribution to roentgenographic cephalometrics. It is based, in principle, upon the assumption that, in an individual person, cephalo-facial proportionality is achieved by a balance between certain growth loci or segments. We have sought, therefore, to elucidate a basic architectural pattern. 2. 2. Our findings are based upon cephalometric x-ray films on file at the Philadelphia Center for Research in Child Growth. We have used 100 lateral headplates (fifty-one girls and forty-nine boys, mostly of the Mediterranean white race). Of these, fifty have normal occlusion, twenty have Class I malocclusion, twenty have Class II, and ten have Class III (Angle) malocclusions. 3. 3. We have used four main horizontal planes of reference, each centering in an area of growth-adjustment. These are as follows: 3.1. a. Cephalofacial or upper.—Anterior cranial base plane. 3.2. b. Midfacial.—Palatal plane. 3.3. c. Dental.—Occlusal plane. 3.4. d. Mandibular or lower.—Mandibular base plane. 4. 4. We hold that a face is well proportioned when the axes of these four planes, prolonged posteriorly, meet or intersect in a single common point, 0 . This point 0 is usually posterior to the occipital contour. The location of 0 may vary with age, closer to or within, the occipital contour in younger children, and farther or beyond, the contour in older children. This remains to be tested. 5. 5. With the point 0 as a center, we establish two arcs: (a) anterior, with 0 -ANS as radius; and (b) posterior, with 0 -S p as radius. 6. 6. In a well-proportioned face, the anterior arc intersects, from above down, the frontoethmoid junction, nasion, anterior nasal spine, incisal edge of the upper central incisor, and pogonion. 7. 7. Similarly, the posterior arc intersects the posterior wall of sella turcica and gonion. 8. 8. The relation of our four planes to the common point 0 permits of the classification of four facial types: 8.1. Type I: Anterior cranial base plane does not pass through 0 . 8.2. Type II: Palatal plane does not pass through 0 . 8.3. Type III: Occlusal plane does not pass through 0 . 8.4. Type IV: Mandibular base plane does not pass through 0 . 9. 9. Since, in each facial type, the deviant plane may pass above (A) or below (B) the point 0 , we may recognize subtypes, as IA or IB and so on. 10. 10. In our sample, we determined that a well-proportioned face invariably has normal occlusion. Normal occlusion alone, however, is not sufficient to define or establish a well-proportioned face. 11. 11. The axial relation of upper and lower permanent teeth to the palatal plane and mandibular plane has been studied (upper Il and Ml, lower il and ml). Their respective relationships to the palatal plane and mandibular plane are such that angle M′ = angle I′ + 10 degrees and angle m′ = angle i′ + 5 degrees. 12. 12. In other angular relationships we have found that the axial inclination of the lower incisors to the palatal plane is the same as that of the upper incisors to the occlusal plane. 13. 13. We have found that the angle formed by the ramal plane with the occlusal plane is equal to the angle formed by the axial inclination of the lower central incisor with the occlusal plane (angle R = angle i). 14. 14. Via the serial case history method, we have analyzed facial angle relationships during growth and also during the course of orthodontic treatment. As a result of these procedures, we have presented a section entitled “Diagnostic and Treatment Plan”, in which we outline the step-by-step application of our concepts of architectural harmony (proportionality). 15. 15. Since we feel that cephalometric x-ray films are a means, rather than an end, we emphasize the basic importance of the clinical examination. In our thinking, the model is the best objective link between clinician and x-rays. Hence, we offer a method of trimming the casts that will orient the teeth to: (1) the palatal plane, (2) the occlusal plane, and (3) the mandibular base plane. 16. 16. We suggest that our analysis is of potential value in phylogenetic studies, in family line inheritance studies, and in the allied dental fields of oral surgery, periodontics, and prosthetics. Pilot studies in these areas of investigation will be undertaken at the Growth Center in due time.