A. Testing of Methodology This project is a formalized study to test the reliability and validity of constructing three-dimensional cephalometric landmark data found on corresponding matches pairs of conventional posterior anterior and lateral cephalometric films. These two-dimensional landmarks will be converted to three- dimensional landmarks by a variant of the Ray Intersection Method commonly used in sterophotogrammetry. B. Development of a Control Database This study will analyze data on normal individuals from the University of Michigan School Study using techniques the group has developed to convert two standard two-dimensional cephalograms (i.e., lateral and posteroanterior) of the same patient into a computer synthesized 3D representation. By computing an approximate midsaggital plane from the digitalized data, other landmarks can be assigned likely positions. Mean coordinates of the reconstructed 3D points will be computed separately by age and sex with the age range of 6 through 15 years. C. Study of Hemifacial Microsomia This project involves using archival lateral and PA cephalometric film pairs from patients with hemifacial microsomia to derive a set of three-dimensional landmarks points. Sets of three points in triangles from affected and normal individuals will be compared by the tensor method. F-ratio or Bartlett's test will be used to test descriptors for fluctuating and directional asymmetry. General and specific factors will be derived from several angles for asymmetry. D. Study of Craniofacial Synostosis This project is designed to provide a three-dimensional description of symmetrical craniosynostosis syndromes (Apert, Crouzon and Pfeiffer) with an aim to improve understanding of the shape deformities involved. E. Study of Frontonasal Dysplasia vs. Craniofrontal Dysplasia Previously, from two-dimensional PA cephalometric measurements, differences and similarities were identified between 22 patients with frontonasal dysplasia and 26 patients with craniofrontonasal dysplasia. When compared with normal populations, both dysplastic groups exhibited high nasal tables and the orbital rims were reduced in size in an inferolateral direction. The object of this project is to compare the two syndromes on their 3-dimensional cephalometric landmarks with respect to the relationships found in the midface and cranial base.
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