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Practical Panoramic Imaging

Course Number: 589

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.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.

Figure 33.Example of an overexposed panoramic radiograph.

Example of an overexposed panoramic image:

Figure 34a.

Figure 34b.

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.

Figure 35b

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.

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.

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.

1. Mandibular Condyle12. Cervical Vertebra23. Genial Tubercles
2. Coronoid Process13. Zygomatic Process24. Nasal Concha
3. Nasopharyngeal Airspace14. Incisive Foramen25. External Oblique Ridge
4. Oropharyngeal Airspace15. Mandibular Foramen26. Angle of the Mandible
5. Styloid Process16. Mandibular Canal Space27. Zygomatic Bone
6. Lateral Pterygoid Plate17. Soft Palate28. Glenoid Fossa
7. Zygomatic Arch18. Hyoid Bone29. Inferior Border of the Mandible
8. Articular Eminence19. Hard Palate30. Palatoglossal Airspace
9. Anterior Nasal Spine20. Nasal Septum31. Pterygomaxillary Fissure
10. Mental Foramen21. Maxillary Sinus Floor32. Maxillary Tuberosity
11. Infraorbital Canal22. Nasal Fossa33. 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.