4-25. MANDIBULAR BICUSPIDS
Position the instrument assembly in the patient's mouth with the bicuspids
centered on the film, ensuring that the film is parallel both vertically and horizontally.
Centering the bicuspids may not be possible in patients with small mouths. Therefore,
position the film in the center of the mouth as far forward as possible, touching the
curvature of the lower arch (see figure 4-26). Parallel film placement is the key; it
prevents dimensional distortion and overlapping. With the plastic bite-block held in
place by the occlusal surfaces of the mandibular bicuspids, insert a cotton roll between
the block and the maxillary teeth. Have the patient close his teeth holding the film in
place. Slide the locator ring along the indicator rod bringing it close to the skin surface
and align the x-ray unit extension tube with both the rod and the ring on the horizontal
and vertical planes.
Figure 4-26. Mandibular bicuspid area.