Outside Job: A Look at Today’s Extraoral Radiography





By Rebecca Stone August 22, 2019

While clinicians typically rely on digital intraoral radiography to capture full mouth X-rays and bitewings, sometimes you just need a big picture. Extraoral radiographic imaging may be either film based or digital, and either two-dimensional (2D) as in panoramic or cephalometric imaging, or three-dimensional (3D) as in cone beam computed tomography (CBCT).

Many radiographic units these days often incorporate all three, or at least the capability of all three, for those who prefer to add technologies as they go.

Cephalometric Radiography

Cephalometric radiography, or “ceph,” is most frequently used by orthodontists and oral surgeons to help formulate diagnoses and treatment plans. Cephs capture structures from the neck up in lateral and frontal views to facilitate the study of the relationship between the teeth and bones in the head via the identification of anatomical landmarks.1

There are two approaches to this type of analysis. The metric approach measures the distances between landmarks on linear and angular planes. The graphic approach allows visual comparisons through manual pinpointing of landmarks on a paper tracing of the cephalogram. Before and after treatment markings can then be compared by placing one tracing over another.1

Panoramic X-rays

Panoramic technology captures a 2D image of the teeth, jaws, sinuses and temporomandibular joints. Images are taken via a sensor as it circumnavigates the patient’s head. The result is a flattened view of the curvature of the mouth, jaws, and teeth for a broad depiction of the oral cavity and sinuses.2

In contrast to film-based pans, digital formats offer benefits as cost-saving, radiation-sparing, higher-quality technologies. Direct imaging captures images via vertical, fan-shaped beams and sensors that can process images automatically. Indirect digital units require the use of photostimulable phosphor plates (PSPs) that store the exposed image, which is subsequently read by laser scanners to render diagnostic-quality radiographs that can be manipulated via software.2

Often called a “pan” for short, this type of radiography is also often incorrectly identified as the “Panorex.” In reality, that was the trademarked name of a machine introduced in 1959, which no longer exists.2

CBCT

Cone beam computed tomography (CBCT) has significantly impacted all facets of dentistry. Few can dispute the ultra-cool look of 3D imagery compared to 2D shots. And though we can learn a great deal from 2D cephs and pans, CBCT offers a much more accurate representation of structural relationships within the patient’s head, allowing a more complete analysis. In fact, many clinicians view this technology as the most significant recent advancement in dentistry.3, 4

CBCT produces detailed imagery by assembling hundreds of slices of radiographic information and combining it into a 3D view. Diagnostic analyses can then be made through the use of software into which the visual information is imported. This can be extremely helpful in the case of implant placement.3

CBCT emits considerably more radiation than other radiographies. However, when used with the appropriate care, CBCT’s enhanced ability to reveal anatomical landmarks on a 3D image is becoming invaluable in modern dentistry.3

Of course, isolation systems such as Isolite are not typically used during extraoral radiography. But for treatment strategies developed as a result of these X-rays, such adjuncts, are, in themselves, invaluable. It all boils down to the fact that by employing many of the cutting-edge tools continually becoming available to dentistry, clinicians have a shot at improving accuracy, predictability, cost savings, efficiency and ultimately, success.

REFERENCES

  1. Stone R. The big picture. Mentor. 2014; 5(01):36–39.
  2. Stone R. Scan artist. Mentor.2013; 4(8):14–16,18–19.
  3. Stone R. Special delivery. Mentor. 2017; 8(8):24–26,28–29.
  4. Stone R. Life in the fast lane. Mentor. 2018;9(5):10–14.