Investigations 1

Having made the decision that an x-ray is indicated in your patient with mandibular trauma, or suspected TMJ dislocation, the next question is which x-ray techniques are available to image the mandible and TMJ?

In the UK, two techniques are commonly used:

• Orthopantomogram (also known as OPG, or panoramic radiograph)
• Standard mandibular series (AP, reverse Towne’s and two lateral obliques)

Which of these is the most accurate?

A number of comparisons have been made of the two techniques in mandibular fracture. A BestBets review concluded that the OPG is the most accurate technique and consequently the best initial film for screening, but should be followed by additional views if clinical suspicion remains [10].

A more recent analysis agreed with this conclusion, but noted greater diagnostic accuracy if the OPG was combined with an AP view of the mandible [11].

The OPG is also the best initial screening radiograph for TMJ dislocation [12], although specific TMJ views may also demonstrate the dislocation.

Learning Bite

The OPG is the best x-ray technique for accurate diagnosis of mandibular fracture and TMJ dislocation. Its accuracy in mandibular fracture is even greater when combined with an AP view of the mandible.