Problem #3: Fail to Capture Distal of Canine on Premolar Bitewing Image
Example: Not capturing the distal canine crown on the premolar bitewing image.
Discussion: There are many reasons for this problem and several solutions. Examples include malpositioned canine crowns that are too far forward, uncomfortable positioning that causes the patient to move the mandible forward and away from the sensor, and dead zones on the sensors.
In Figure 21, the sensor is positioned for a premolar bitewing, where the criteria includes imaging the distal crown of canines #11 and #22. As seen inside the red circle, there is dead zone behind premolar #’s 12 and 21. The full first premolars and the distal canine crowns will not appear on the image.
Figure 21 - Premolar Bitewing.
The deadzone of the sensor is behind tooth #21 within the red circle. The premolars and the distal canine crowns will not be captured in the image.
1. Purposefully position the PID to pass radiation over the canine, whether the sensor is fully behind the canine or not. By moving the PID forward, you are changing the radiation’s path allowing a portion of the canine crown to be imaged. In Figure 22, the PID is not following the aiming ring in the horizontal plane as evidenced by the unequal gap between the PID and the ring.
The PID may be intentionally placed away from the aiming ring when it is determined that the ring is not creating the needed radiation path to open the contacts.
2. Corded sensors often have a larger dead zone at the corded end. Figure 23 shows two solutions with the featured sensor, which has rounded corners and a fuller active area on the far end (away from the cord) of the sensor. The corded end of the sensor is posterior, and the cord has been gently turned forward to come out of the mouth (ensure that the active side of the sensor is toward the PID). Figure 23 B shows the reversed sensor in the bitewing holder. Figure 23 C shows the use of a simple bite-tab on a reversed sensor, which eliminates the bulkiness of the bitewing holder, positioning ample active sensor behind the canine crowns. Use this technique with caution, and only as a last resort, as bending the cord may damage the sensor.
Figure 23 - Premolar Bitewing.
(A) Sensor deadzone is behind the premolars... the required canine and premolar will not be captured in the image. Solutions to position active sensor behind the canine crown include reversing the sensor in a traditional holder (B), or by using a simple tab with a reversed sensor (C).
3. When positioning the sensor for a premolar bitewing, the anterior mandibular bone is in contact with the sensor, and if painful, the patient moves the mandible forward and away from the sensor. When the above methods are unsuccessful in capturing the distal of the mandibular canine crown, use a periapical holder instead of a bitewing holder (Figure 24). The mandible cannot move away from the periapical holder as it can with a bitewing holder. Use zero degrees vertical angulation across the mandibular premolar-canine to create the ‘bitewing’ look of the crowns and interproximal contacts.
Creating a bitewing-like image of the mandibular premolar crowns using a periapical sensor holder and 0 degrees vertical angulation.