c. Avoid movement of the film during exposure.
d. In placing the film packet in the mouth, avoid contact between the film and
oral tissues until the film is in approximately the desired position. Many patients tend to
gag when film is moved along in contact with oral tissues. Patience and gentleness will
help to reduce gagging. Allowing anesthetic lozenges to dissolve on the tongue before
film is placed in the mouth is sometimes helpful. Instructing the patient to breathe
deeply through the nose also aids in controlling the gag reflex.
4-5.
PERIAPICAL RADIOGRAPHIC TECHNIQUES
Periapical radiography is designed to give diagnostic images of the apical
portions of teeth and their adjacent tissues. A full mouth intraoral examination consists
of 14 periapical radiographs with two bite-wing films and provides an image of all teeth
and related structures. Single periapical radiographs are often made of individual teeth
or groups of teeth to obtain information for treatment or diagnosis of localized diseases
or abnormalities. The bisecting (short-cone) and paralleling (long-cone) techniques are
two of the most commonly used techniques. Both techniques have advantages and
disadvantages. The dental officer's preference determines which technique will be
used.
Section II. BISECTING (SHORT-CONE) PERIAPICAL EXPOSURE TECHNIQUES
4-6.
GENERAL
A short cone is used to take x-rays with bisecting angle exposure techniques.
The target-film distance is 8 inches. The resulting image x-ray is somewhat larger using
the short cone rather than using a long cone (see figure 4-1). The bisecting plane is
halfway between the plane of the dental film and the longitudinal axis of the tooth. The
average angle of projection is the angle between the occlusal plane and the angle of the
central ray. The angle of the central ray is in relation to the bisecting plane.
Figure 4-1. Comparison of 8-inch and 16-inch target-film distances.
MD0512
4-3
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