Problem #5: Comparison of periapical images versus bitewing images
Question: Will a periapical of maxillary teeth show caries at the crown margin as well as a bitewing?
Answer and Discussion: NO. The maxillary periapical image is created using +10 to +30 degrees of vertical angulation as compared to a bitewing that is usually created with +5 degrees. The greater vertical angulation changes the way the crown looks on the image. The buccal and lingual margins superimpose part of the root, making diagnosis of the margin impossible. Figure 28 compares a periapical and bitewing of the same crowns. Caries can only be diagnosed from this bitewing image, as the crown margins are covering the root immediately adjacent to the margin on the periapical image.
Solution: Well-taken bitewing images are far superior to periapical images for imaging crown margins and bone levels. The goal is to keep the crown separate from the neighboring tooth and bone. First, level the occlusal plane. Stand in front of the patient, look at the buccal and lingual margins of the crown and place them on a single line, then follow that line with the PID’s vertical angulation.
Use this technique when verifying crown margins prior to cementation. Do not use the aiming ring, your goal is to parallel the margins of the crown. Better to do that by positioning the PID directly across the crown margins.
Figure 28 - Comparison of periapical and bitewing images of the same crowns in the same patient.
(A) The periapical image is not diagnostic for bone levels and crown margins. (B) The crown margins and bone are visible for examination on this ideal Bitewing image.
Figure 29 - Imaging crown margins.
Create a single plane across the buccal and lingual margins with the Path of Radiation to create an ideal image.
Question: Is a periapical of maxillary molars the best image to portray the periodontal bone status and show the furcation areas?
Answer: Usually not, because of limitations in the oral cavity, such as a shallow palate, preventing the sensor from paralleling the teeth.
Discussion: As mentioned in the introduction, excessive vertical angulation can foreshorten the structures on an image. When there is adequate room in the palate for the sensor to parallel the teeth, the image will be ideal. When the sensor does not parallel the teeth because of a narrow or small palate, the sensor must flatten towards the occlusal plane, thereby increasing the vertical angulation, positioning the aiming ring towards the ceiling.
Solution: The vertical bitewing technique can be used in the maxillary arch when a non-foreshortened image of a molar is needed (Figure 30). This is particularly helpful when assessing periodontal bone loss and furcation involvement. In a patient with a flat, shallow palate, the sensor cannot align fully with the maxillary roots. The operator used +10 degrees and the molar’s apex is nearly off the image (Figure 30B). The furcation, crown margins, and the bone levels are visible in this diagnostic image. There is no superimposition of the maxillary process of the maxilla or the zygomatic arch. This technique will work well in a patient with a high palate.
Figure 30 - Maxillary periodontal assessment of bone levels and furcations using the vertical bitewing holder.
(A) Lift the PID over the desired area at +5 to +10 degrees. (B) The bone levels and furcation are imaged true, though the entire apex is not visible. (C) Offset the sensor towards the Maxilla.