Radiographs are obtained to confirm the presence of clinically suspected fractures and to rule out additional fractures not clinically evident. Most mandibular fractures occur in pairs--often one is clinically evident while the other is not.
Types of Radiograph Films
The following radiograph films are useful in diagnosing fractures of the mandible and midface. Each film gives specific information and has its limitations. These are discussed in detail on the following pages.
The panoramic film is probably the most valuable film available for diagnosing fractures of the mandible. Fractures of the following areas can be detected:
Displacement in a superior or inferior direction can be readily assessed with this view, but lateral or medial displacement cannot be determined.
Caution: Some subcondylar fractures may be difficult to diagnose from this radiograph. Fractures of the ramus and angle require additional films to determine if displacement is present. A fracture of the angle can appear to be non-displaced on a panoramic view when, in fact, the ramus may be displaced considerably in a medial or lateral direction. Failure to diagnose such fractures can lead to very poor treatment results.
The mandible series consists of three films–a PA mandible and right and left lateral obliques. When studying these radiographs, it is often helpful to have a dry skull available to aid in orientation and identification of landmarks.
The PA Mandible radiograph provides an excellent image of the entire mandible except for the condylar heads and the immediate subcondylar area. Fractures in the following areas can be detected:
Since the PA mandible film is exposed from a perspective of 90 from that of the panoramic or lateral oblique view, it provides valuable information regarding medial or lateral displacement of fragments.
Mandible Series–Left and Right Lateral Oblique Films
The left and right lateral oblique radiographs provide much of the same information as the panoramic view. Fractures in the following areas can be detected:
These films do not provide good images of the symphysis region. If a good panoramic radiograph is available, the lateral obliques are not necessary. Often on weekends or evenings a panoramic view will not be available and the mandible series can be easily obtained and will provide adequate information for fracture diagnosis.
AP Towne’s Mandible Film
The AP Towne’s mandible is the best radiograph for assessing the mandibular condyles and subcondylar region. This view is taken in such a way that other bony structures are not superimposed over the condyles. If a condylar head or subcondylar fracture is suspected, obtain an AP Towne’s mandible view.
Water's View Film
The Water’s View must be obtained when fractures of the midface are suspected. This film is often difficult to interpret, and the use of a dry skull is recommended. You should look for asymmetry, fracture lines, or opacity of the maxillary sinuses. Fractures, if present, are likely to be noted at the lateral orbital rims, infraorbital rims, lateral wall of the maxillary sinus, and the zygomatic arches. All patients with midface fractures should be referred to the appropriate specialist.
Submental Vertex View Film (SMV)
The SMV is specifically indicated to confirm or rule out fractures of the zygomatic arch. If fractures are noted, the patient again needs to be referred. This view is often called the “jughandle.”
Dental radiographs are often very helpful in diagnosing facial fractures. The sharp detail produced on these films can provide needed information regarding teeth in the line of fracture, fractured teeth, etc. An occlusal film can help determine the displacement of the inferior border of the mandible in the symphysis area. Do not overlook the value of these films.
Two periapical radiographs are taken: one through the area where the impacted tooth is suspected to be, and one by moving the cone more distally. The radiographic film is placed in the same position for both exposures. Three possibilities will exist. The unerupted tooth:
appears to move farther distally with a fixed landmark tooth.
moves mesially as the cone moves distally, then the erupted tooth lies labial to the landmark tooth.
remains stationary, then it lies at the same depth as the landmark tooth.
Maxillary Occlusals. Occlusal views are valuable if the central ray can pass through the long axis of the teeth. Because this is difficult to do in the maxilla, maxillary occlusals can be very deceiving.
Mandibular Occlusals. Mandibular occlusals which have the central ray passing through the long axis of the teeth, can be very helpful in determining the position of impacted teeth in the bicuspid region.