Face
Normal anatomy: mandible
The orthopantomogram (OPG)
The OPG is a technique for demonstrating the mandible, temporomandibular joints and teeth in a single plane. The X-ray tube and the film cassette rotate around the patient and the exposure lasts a few seconds. A panoramic image is obtained.
Analysis: the checklists
Midface injury
The midface anatomy appears very complex. Try this approach. Think of the zygoma (malar bone) as a midface stool with four legs. The seat of the stool is very strong. The four legs are much weaker, so you need to assess each leg very carefully.
A five-point checklist
Inspect the OM views as follows:
Concentrate on the stool’s legs. For each leg compare the injured side with the other (normal) side. Look for any asymmetry or any difference between the appearance of the matching legs. Check as follows:
2. Leg 2: frontal process of the zygoma.
4. Leg 4: lateral wall of the maxillary antrum.
5. Look for fractures and look for:
□ a fluid level (blood from a fracture) in the maxillary antrum;
Always apply this rule: If any one of the legs is fractured then always, always, double check whether the other three legs of the midface stool are intact (see Tripod fracture, p. 63).
Midface stool—Legs 2 & 3
Normal radiograph.
Midface stool—Leg 4
Lateral wall of the maxillary antrum (arrow).
Normal radiograph.
Suspected blow-out fracture
Evaluate the OM view (see p. 66).
Injury to mandible
Evaluate the OPG view (see pp. 68–70).
