The temporomandibular joint (TMJ) is one of the most difficult areas to investigate radiographically. This fact is underlined by the many types of investigations that have been developed over the years. Several plain radiographic projections and various modern imaging modalities are used for showing different parts of the complex joint anatomy. The clinical problems are complicated by the broad spectrum of conditions that can affect the joints, which can present with very similar signs and symptoms, and by prolonged searches for objective signs to explain TMJ pain dysfunction.
In addition to this knowledge of the static anatomy, clinicians need to be aware of the types and range of joint movements which result in the condyles moving downwards and forwards when patients open their mouths. These include:
Previously described transorbital and transcranial views are now seldom used and are only of historical interest.
The main clinical indications are the same as for a conventional panoramic radiograph. If the equipment includes specific TMJ programmes these should be regarded as the views of choice as additional information can be provided when the mouth is opened.
• The patient is positioned with their Frankfurt plane angled 5° downwards within a panoramic unit with their mouth closed but using a special nose/chin support as shown in Fig. 30.5A instead of the bite-peg
• The distance from the external auditory meatus to the canine light is measured and the anteroposterior position of the chin support adjusted manually to ensure that the condyles appear in the middle of the image
1. The patient holds the cassette against the side of the face over the TMJ of interest. The film and the mid-sagittal plane of the head are parallel. The patient’s mouth is open and a bite-block is inserted for stability.
2. The X-ray tubehead is positioned in front of the opposite condyle and beneath the zygomatic arch. It is aimed through the sigmoid notch, slightly posteriorly, across the pharynx at the condyle under investigation, as shown in Fig. 30.7. Usually this view is taken of both condyles to allow comparison.