Features of an Ideal Panoramic Radiograph

There are two general features that distinguish this panoramic from a poor one – they are adequate exposure and correct anatomic representation.

Figure 31.
Excellent edentulous panoramic radiograph
Example of an excellent edentulous panoramic radiograph with adequate exposure and correct anatomic representation.

Adequate exposure – An assessment of adequate exposure implies that there is adequate density and contrast to recognize anatomic features.

  • Density - The ideal density should be such that structures are not obstructed by areas of darkness i.e. areas of “burn out” or areas that are too light i.e. areas of “white out”. Visually this can be assessed by looking at the mandibular parasymphyseal area and region associated with the apices of the maxillary teeth. In the maxilla this is most evident when the tongue is not held in position during panoramic exposure. Excessive or inadequate density can lead to failure to detect features such as unerupted and impacted teeth or even pathology. A dark or high-density image is usually caused by overestimation of the patient’s overall size, stature and bone density while a light or low-density image is usually caused by underestimation of the patient’s overall size, stature and bone density.
Figure 32.
Regions on a panoramic radiograph to look at to determine adequate density
Regions on a panoramic radiograph to look at to determine adequate density.
Figure 33.
Example of an overexposed panoramic radiograph
Example of an overexposed panoramic radiograph.

Example of an overexposed panoramic image:

Figure 34a.
Example of an overexposed panoramic image
Figure 34b.
overexposed panoramic image
Images demonstrating how excessive exposure can lead to failure to detect pathologic features. The image on the right is a digitally enhanced version of the left overexposed panoramic radiograph and clearly demonstrates the appearance of a radiolucent region causing expansion and thinning of the inferior cortex of the right mandible – features that were not evident on the original.

Example of an underexposed panoramic image:

Figure 35a.
Example of an underexposed panoramic image
Figure 35b.
underexposed panoramic image

Images demonstrating how inadequate exposure can lead to failure to detect pathologic features. This image on the right is a digitally enhanced version and clearly demonstrates the appearance of an impacted mandibular right third molar that was not readily apparent on the original (left). This enhancement also clearly demonstrates a large pericoronal pathology that seems to involve the right second mandibular molar.

  • Contrast – The second element of adequate exposure assessment is contrast. This can best be assessed by determining if the interface between the enamel and the dentine can be seen, usually in the molar region.
Figure 36.
Assessment of contrast in panoramic radiograph
Assessment of contrast in panoramic radiograph.

Anatomically representative – A panoramic should be a good representation of the maxillofacial structures that it images. This means that there is adequate coverage of the osseous structures and that they are represented with some degree of accuracy. To determine correct anatomic representation, a visual assessment of the panoramic radiograph should be performed for accuracy of both anatomic structures and the dentition.

  • Anatomic assessment – Several features can be used to determine anatomic accuracy including:
    • The condyles are on image – Usually in the upper outer sextant and at same level.
    • Palate and ghost images of palate should be above the apices of the maxillary teeth, running through the lower portion of the maxillary sinus.
    • Ramus width should be very similar on both left and right sides.
Figure 37.
Anatomic features to be compared in the assessment of panoramic anatomic accuracy
Anatomic features to be compared in the assessment of panoramic anatomic accuracy.

Panoramic anatomy – A reference for anatomic structures commonly observed on panoramic diagram appears below. Many of these structures are mentioned in the prior text and in the subsequent discussion of common errors.

Figure 38.
reference for anatomic structures commonly observed on panoramic diagram
1. Mandibular Condyle 12. Cervical Vertebra 23. Genial Tubercles
2. Coronoid Process 13. Zygomatic Process 24. Nasal Concha
3. Nasopharyngeal Airspace 14. Incisive Foramen 25. External Oblique Ridge
4. Oropharyngeal Airspace 15. Mandibular Foramen 26. Angle of the Mandible
5. Styloid Process 16. Mandibular Canal Space 27. Zygomatic Bone
6. Lateral Pterygoid Plate 17. Soft Palate 28. Glenoid Fossa
7. Zygomatic Arch 18. Hyoid Bone 29. Inferior Border of the Mandible
8. Articular Eminence 19. Hard Palate 30. Palatoglossal Airspace
9. Anterior Nasal Spine 20. Nasal Septum 31. Pterygomaxillary Fissure
10. Mental Foramen 21. Maxillary Sinus Floor 32. Maxillary Tuberosity
11. Infraorbital Canal 22. Nasal Fossa 33. Zygomaticotemporal Suture

Features of the Dentition – Several visual features of the dentition can be used to assess whether the teeth, particularly the anterior teeth are positioned correctly within the focal trough:

  • No or slight upward curve of teeth
  • No tooth size discrepancy on left or right side
  • Anterior teeth in focus (see pulp canal clearly)
  • Anterior teeth shape “normal”
  • Not too narrow or too wide
  • Premolars will always overlap due to inherent x-ray beam projection to the arch of the teeth in this region.
Figure 39.
Features of the dentition to be compared in the assessment of panoramic anatomic accuracy
Features of the dentition to be compared in the assessment of panoramic anatomic accuracy.
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