Positioning the Tube Head

Figure 1-19.—Film and cylinder placement: mandibular cuspid area. and the plane of the film should be nearly parallel. In patient gently holds the device with the hand from the order to project the proper image of the tooth onto the film, you must visualize an imaginary line bisecting the long axis of the tooth and the plane of the dental film (fig. 1-25). The central ray is then directed perpendicular (a 90° angle) to the bisecting line. This will project the proper dimensions of the tooth onto the film without elongation or foreshortening. If the anterior curvature of the patient's arch is narrow, insert a cotton roll between the packet and the teeth. This prevents the film from bending excessively and producing a distorted image. Once the film packet is properly positioned, guide a free hand of the patient to the holding device. The opposite side of the arch being radiographed. WARNING: The assistant should never hold the film packet in position during an exposure. Each time you take radiographs, use the standard film positions. This helps when comparing radiographs made at different times. Positioning the Tube Head After the film is inserted in the patient's mouth, position the tube head so the end of the cylinder is near the area to be radiographed. Then, position the tube head for correct vertical and horizontal angulation 1-17