. Elementary and dental radiography / by Howard Riley Raper . will remain positive always, unless the pole changing switchis changed and he may connect his tube to the coil accordingly. Posing tne Patient and Adjusting the XRay Cube and film or Plate. Dental radiographs, or odontoradiographs, have been divided into twoclasses: (1) The intra-oral and (2) the extra-oral. Intra-oral radio-graphs are made by holding films in the mouth; extra-oral radiographsare made on plates, or films, usually plates, placed outside of the mouthfor exposure. MAKING DENTAL RADIOGRAPHS 95 IntraoralRadiographs It ma
. Elementary and dental radiography / by Howard Riley Raper . will remain positive always, unless the pole changing switchis changed and he may connect his tube to the coil accordingly. Posing tne Patient and Adjusting the XRay Cube and film or Plate. Dental radiographs, or odontoradiographs, have been divided into twoclasses: (1) The intra-oral and (2) the extra-oral. Intra-oral radio-graphs are made by holding films in the mouth; extra-oral radiographsare made on plates, or films, usually plates, placed outside of the mouthfor exposure. MAKING DENTAL RADIOGRAPHS 95 IntraoralRadiographs It makes no difference what sort of a radiographis to be made, it should always be borne in mind,while posing the patient and adjusting the tube andplate, or film, that you are using your X-rays as a source of light to cast ashadow of some object—, the object being radiographed—on a screen—, the film or plate. To impress this idea more firmly in your mind observe Fig. 82. Thesource of light, the candle, casts a distorted—an elongated—shadow of. Fig. 82. the object, a plaster of Paris tooth, on a white screen. As you observe thisillustration contemplate what would have to be done to overcome the ex-treme distortion of the shadow and make it approximately the same lengthas the tooth. Is it not true that either the light must be moved upward orthe screen must be placed more nearly parallel with the tooth, or perhapsa little of both? If you follow this reasoning you are on the way to mak-ing proper poses for radiographs, for the principle involved is the ideal pose for making a radiograph is to have the focal ray, orcentral ray, indicated by the pointer at the end of the cylinder in Fig. 83,directed to strike the object being radiographed, and the plate or film, 96 DENTAL RADIOGRAPHY at right angles. (See Fig. 70.) This is impossible much of the time inthe practice of Between As tlie beginner first attempts posing patient and X-Ray tube an
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