Problem #4: Bitewing Images Not Ideal
Example: Bitewing image is not balanced, there is more mandible than maxilla.
Discussion: Bitewings are not just for opening contacts. Bitewings are critical for capturing true bone levels. The vertical angulation used for periapical images often distorts the bone levels and the dentist is at a disadvantage when diagnosing periodontal bone loss. Because of the position of the teeth in the jaws (Figure 4), +5 degrees is needed to create an ideal bitewing image.
Solution: Remember the statement from earlier in this presentation: “The Path of Radiation must include the area of interest (teeth and surrounding bone) and active sensor.” When the patient bites on the bitewing holder, the aiming ring is often tilted downwards towards the floor, as in Figure 25A. In this negative path, active sensor may not be in position behind the maxillary crestal bone. The crowns of the maxillary teeth will appear on the image, but not the bone levels. When this happens, position the PID at +5 degrees across the maxillary bone and center across the arches of teeth (Figure 25B).
Figure 25 - Bitewing not balanced.
(A) Negative vertical angulation across a bitewing will often cut off the Maxillary crowns and bone levels.(B) The PID hs been placed to the suggested +5 degrees, and is not following the aiming ring.
Example: No Maxillary restoration margins or bone levels on the bitewing.
Discussion: When critiquing bitewing images, identify restoration margins and bone levels on both the maxillary and mandibular arches. When restorations are large and extend further apically along the root, the full restoration and its position against the natural tooth may not be captured with a traditional bitewing position. In Figure 26, the crown margin of #13 is barely visible, #14 can be seen, and the distal of #15 was not imaged. The crown margins of #’s 18, 19, and 20 are apparent and diagnostic. Insufficient positive vertical angulation is the reason the maxillary margins are missing.
Solution: The positive vertical angulation in Figure 27B has remedied the problem. When the maxillary bone loss is extensive, the PID may need +5 to +10 degrees, and should be positioned higher across the actual position of the crestal bone that is desired (Figure 27C).
Figure 26 - Bitewing image did not capture Maxillary margins or bone.
(A) The crown margins and bone levels of tooth #'s 13, 14, 15, do not appear in the image, because the patient's bite caused the sensor holder to pitch downward with negative vertical angulation, and the aiming ring was followed (B).
Figure 27 - Ideal bitewing image.
(A) The image is balanced with crown margins and bone levels on both arches. (B) The PID was set at +5 degrees across the occlusal plane, and did not follow the aiming ring. (C) In patients with moderate to severe periodontal disease, the PID can be positioned over the area of Maxilla that is desired.