. Elementary and dental radiography / by Howard Riley Raper . Film Fig. 91. Diagrammatic illustration of the pose seen in Fig. 90, showing the X-rays striking thetooth and film at such an angle as to cause shortening of the shadow cast on the film, 102 DEXTAL RADIOGRAPHY teeth and film is not right. This position of the tube would be correct, ifthe film were parallel with the teeth; but it is impossible to place the filmin this relation to the upper teeth. Fig. 89 is a diagrammatic illustrationof the pose shown in Fig. 88. With the film placed in the mouth as per Fig. 85, Fig. 90 illustratesan
. Elementary and dental radiography / by Howard Riley Raper . Film Fig. 91. Diagrammatic illustration of the pose seen in Fig. 90, showing the X-rays striking thetooth and film at such an angle as to cause shortening of the shadow cast on the film, 102 DEXTAL RADIOGRAPHY teeth and film is not right. This position of the tube would be correct, ifthe film were parallel with the teeth; but it is impossible to place the filmin this relation to the upper teeth. Fig. 89 is a diagrammatic illustrationof the pose shown in Fig. 88. With the film placed in the mouth as per Fig. 85, Fig. 90 illustratesanother incorrect pose. The X-rays do not strike the teeth and film atthe correct angle and the teeth in the resulting radiograph are too 91 is a diagrammatic illustration of the pose shown in Fig. 90. A study of Figs. S~, 89 and 91 will show that in order to make aradiograph which will not picture the teeth too long nor too short the. Film Fig. 9: X-rays should strike the film almost, but not quite, at right angles to itssurface. This same idea has been expressed thus: The X-rays shouldbe directed at right angles to a neutral line drawn between the film andthe tooth. Another writer expresses the same idea so: Bisect theangle made by the plane of the teeth, and the plane of the film, and directthe rays so they will fall perpendicularly to this bisecting plane. The angle of the film in Figs. 87, 89 and 91 is what it would be in theaverage mouth. Suppose, however, the vault is very flat. In such anevent the angle of the X-rays as illustrated in Fig. Sy to be correct, wouldcause a marked lengthening of the shadow, as illustrated by the dottedlines and drawing in Fig. 92. The angle of the X-rays should be as inFig. 91 to avoid, as nearly as possible, any distortion. (Notice in Fig. 92that the bending of the film would cause a lengthening of the shadow.) MAKING DENTAL RADIOGRAlllS 103 Just in proportion as the vault beco
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