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