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A cephalometric roentgenographic comparison of the upper face and associated structures in Class II, Division 1 and Class III malocclusions of the teeth
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ABSTRACTS
AND
REVIEWS
A. From the anterior superior surface of the condyle to the posterior inferior surface of the articular eminence. This represents the articular surface of the joint when the teeth are in occlusion. B. From the most superior surface of the condyle vertically to the roof of the fossa. C. From the most posterior surface of the condyle horizontally to the ant,erior surface of the postglenoid tubercle. In order to check the reliability of temporomandibular joint radiographs, each skull was orientated in Frankfort horizontal plane and the Lindblom apparatus utilized to obtain a radiograph of the articulation with the wax in place. Measurements were then made on the radiographs at the same points as on the wax impressions and the two compared statistically. Twenty sets of measurements were obtained in this manner. A statistical analysis of the measurements thus obtained indicated that carefully orientated radiographs give an accurate portrayal of the relationships which actually exist in the temporomandibular joint. Due to the variable amount of shrinkage and distortion present even in carefully selected skulls, mean values found for the measurements on the skull material would not necessarily coincide with mean values of the living population. It can be stated, however, that t,he distance at point A is the smallest of the three and also is more constant, than those at points B and C. The average distortion produced by angulation and distances such as those used in the Lindblom apparatus is approximately 0.25 mm. The possible maximum distortion in any given case would not be over 1 mm. Distortion implies changes in size only and not changes in relationships of the joint structures.
A Cephalometric Roentgenographic Comparison of the Upper Face and Associated Structures in Class II, Division 1 and Class III BIalocclusions of the Teeth: Ry Willis .J. McCormick, B.S., D.D.S., Northwestern University. The purpose of the thesis was to determine if there are any essential, or characteristic, differences of the maxillae and associated structures in Class II, Division 1 and Class III malocclusions of the teeth; and, if such differences exist, to determine their magnitude. The data were obtained from tracings of lateral head radiographs, obtained by utilizing the Broadbent-Bolton rephalometer to position accurately the head and film cassette during exposure. The t,racings consisted of the anatomical components of the upper face and associated structures, and the posterior arch and tubercle of the atlas? or first cervical vertebra. The mandible and associated struct,ures were omitted from the tracings. The Class II, Division 1 sample consisted of 35 individuals, and the Class III sample consisted of 34 individuals. Angular measurements were made to attempt to relate certain maxillary dental structures, which are frequently discuwed in cephalometric analysis of orthodontic cases, to the cranial base. Linear measurements were made between the various structures of the upper face in order to visualize the relationship of these structures to each other in terms of proportion. In addition, indices were established between certain of these measurements. The data were subjected to biometric analysis, the results of which indicated that there are no essential differences in the relationships of the structures of the upper face, either to each other or to the cranial base, in cases of Angle Class II, Division 1 malocclusion and Angle Class III malocclusion, with the exception of variations in arch length which are commonly noted clinically.
ABSTRACTS
AND
REVIEWS
A. From the anterior superior surface of the condyle to the posterior inferior surface of the articular eminence. This represents the articular surface of the joint when the teeth are in occlusion. B. From the most superior surface of the condyle vertically to the roof of the fossa. C. From the most posterior surface of the condyle horizontally to the ant,erior surface of the postglenoid tubercle. In order to check the reliability of temporomandibular joint radiographs, each skull was orientated in Frankfort horizontal plane and the Lindblom apparatus utilized to obtain a radiograph of the articulation with the wax in place. Measurements were then made on the radiographs at the same points as on the wax impressions and the two compared statistically. Twenty sets of measurements were obtained in this manner. A statistical analysis of the measurements thus obtained indicated that carefully orientated radiographs give an accurate portrayal of the relationships which actually exist in the temporomandibular joint. Due to the variable amount of shrinkage and distortion present even in carefully selected skulls, mean values found for the measurements on the skull material would not necessarily coincide with mean values of the living population. It can be stated, however, that t,he distance at point A is the smallest of the three and also is more constant, than those at points B and C. The average distortion produced by angulation and distances such as those used in the Lindblom apparatus is approximately 0.25 mm. The possible maximum distortion in any given case would not be over 1 mm. Distortion implies changes in size only and not changes in relationships of the joint structures.
A Cephalometric Roentgenographic Comparison of the Upper Face and Associated Structures in Class II, Division 1 and Class III BIalocclusions of the Teeth: Ry Willis .J. McCormick, B.S., D.D.S., Northwestern University. The purpose of the thesis was to determine if there are any essential, or characteristic, differences of the maxillae and associated structures in Class II, Division 1 and Class III malocclusions of the teeth; and, if such differences exist, to determine their magnitude. The data were obtained from tracings of lateral head radiographs, obtained by utilizing the Broadbent-Bolton rephalometer to position accurately the head and film cassette during exposure. The t,racings consisted of the anatomical components of the upper face and associated structures, and the posterior arch and tubercle of the atlas? or first cervical vertebra. The mandible and associated struct,ures were omitted from the tracings. The Class II, Division 1 sample consisted of 35 individuals, and the Class III sample consisted of 34 individuals. Angular measurements were made to attempt to relate certain maxillary dental structures, which are frequently discuwed in cephalometric analysis of orthodontic cases, to the cranial base. Linear measurements were made between the various structures of the upper face in order to visualize the relationship of these structures to each other in terms of proportion. In addition, indices were established between certain of these measurements. The data were subjected to biometric analysis, the results of which indicated that there are no essential differences in the relationships of the structures of the upper face, either to each other or to the cranial base, in cases of Angle Class II, Division 1 malocclusion and Angle Class III malocclusion, with the exception of variations in arch length which are commonly noted clinically.