VARIATION TO THE EXPOSURE FACTORS AND FILM ALIGNMENT

Some variations to the exposure factors and film alignment may be necessary for a specific area of the patient's anatomy.

The dentist may request a radiograph of an impacted third molar. If so, you would prepare the paralleling device in the usual manner, placing the film packet off center in the backing support so the film extends posteriorly to cover the entire third molar area. When you place the paralleling device in the patient's mouth, position it so the anterior edge of the film includes the distal half of the first molar.

Use special film placement procedures when a patient has a low palatal vault or edentulous arches. Place one cotton roll on each side of the bite-block as shown in figure 1-22. This ensures that the X-ray film will be parallel with the long axis of the teeth being radiographed.

BISECTING-ANGLE TECHNIQUE Use the bisecting-angle technique when paralleling devices are not available; or when a patient finds it painful or impossible to close on the bite-block; or when an X-ray is needed when a rubber dam is in place. This technique incorporates the use of a tube head with an X-ray source to cylinder end