Panoramic radiographs are good for a general assessment of jaw bone size and teeth / anatomical structures. However, the inherent magnification and difficulty of placing the jaws inside the focal trough, together with lack of third dimension can produce significant problems in assessing bone morphology. The panoramic image Figure 1 below of a 76 year old lady shows a moderately atrophic mandibular ridge but there does appear to be bone above the mylohyoid ridge in the posterior regions. However, in Figure 2 the reformatted CBCT panoramic shows none on the left and a little on the right.
Tracing of the inferior alveolar nerve canal in figure 4 shows the mental foramen at the level of the alveolar ridge.
In Figure 5 cross sections across the mandible show the left mental foramen opening onto the ridge crest and a lingual knife edge ridge running from the mental
foramen region posteriorly. A similar appearance was found on the right side. None of this was apparent from the panoramic image although an experienced
clinician might be suspicious of the apparent panoramic ridge height .
If you are planning implants cross sectional CBCT should always be performed after your initial pan assessment.
Dr Douglas K Benn BDS, M Phil, DDS, PhD, Diplomate of Dental Radiology (Royal College of Radiologists, England)
Professor of Oral and Maxillofacial Radiology
Creighton University School of Dentistry
Boyne room 207
2802 Webster Street • Omaha NE • 68178