Figure 1-25.Relationship of central ray, tooth, and film
packet in bisecting-angle technique.
GUIDELINES FOR TAKING PERIAPICAL
Take the same 14 radiographs using the same
exposure sequence as that discussed for the paralleling
technique. Complete the following steps:
1. Program the X-ray machine for the discussed
mA and kVp settings. The exposure time varies, just as
it did with the paralleling technique. Refer to the film
+40 to +45
+45 to +50
+30 to +35
+20 to +25
-15 to -20
-20 to -25
-10 to -15
-5 to 0
Figure 1-26.Average vertical angulation.
Figure 1-27.Elongated image.
Figure 1-28.Foreshortened image.
Figure 1-29.Correct and incorrect cylinder direction.
manufacturer's instructions for correct time/impulse
settings. Remember to reduce the kVp by 5 when taking
radiographs in edentulous areas, and to 70 when taking
radiographs on children.