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Types of Dental X-Rays

X-rays (radiographs) are divided into two main categories, intraoral and extraoral. With intraoral X-rays, the X-ray film is inside the mouth. With extraoral X-rays, the film is outside the mouth.

Intraoral X-rays

Intraoral X-rays are the most common type. They give a high level of detail. These X-rays allow dentists to:

  • Find cavities
  • Look at the tooth roots
  • Check the health of the bony area around the tooth
  • See the status of developing teeth
  • Otherwise monitor good tooth health

The various types of intraoral X-rays show different aspects of the teeth:

Bite-wing X-rays highlight the crowns of the back teeth. Dentists take one or two bite-wing X-rays on each side of the mouth. Each X-ray shows the upper and lower molars (back teeth) and bicuspids (teeth in front of the molars). These X-rays are called "bite-wings" because you bite down on a wing-shaped device that holds the film in place while the X-ray is taken. These X-rays help dentists find decay between back teeth. Children don't need bite-wing X-rays until the teeth in the back of the mouth are touching each other. Sometimes this doesn't happen until they get their first permanent molars (also called the 6-year molars).

Periapical X-rays highlight only one or two teeth at a time. A periapical X-ray looks similar to a bite-wing X-ray. However, it shows the entire length of each tooth, from crown to root. This type of X-ray lets the dentist see a child's permanent teeth growing below the baby teeth. It also is used to look for abscesses and gum disease.

Depending on your oral health and dental history your dentist may recommend a full-mouth radiographic survey, or FMX. This includes every tooth, from crown to root to supporting structures. They are X-rayed using both bitewing and periapical radiographs.

Occlusal X-rays are larger than most X-rays. They highlight tooth development and placement in children. Each X-ray shows nearly the full arch of teeth in either the upper or lower jaw.

Extraoral X-rays

Extraoral X-rays are made with the film outside the mouth. These can be considered the "big picture" X-rays. They show teeth, but they also provide information on the jaw and skull. Extraoral radiographs are used to:

  • Keep track of growth and development
  • Look at the status of impacted teeth
  • Examine the relationships between teeth and jaws
  • Examine the bones of the face

Extraoral X-rays are less detailed than intraoral X-rays. For this reason, they are usually not used for detecting cavities or flaws in individual teeth.

Panoramic X-rays show the entire mouth on a single X-ray. They include all teeth on both upper and lower jaws. This type of X-ray requires a special machine. The tube head that emits the X-rays circles behind your head while the film circles across the front. That way, the full, broad view of the jaws is captured on one film. Devices attached to the X-ray machine hold your head and jaw in place. All this may look and feel intimidating, but the process is very safe. It often uses less radiation than intraoral X-rays.

Panoramic X-rays may be used for a child in case of an injury to the face or orthodontic problems. Panoramic X-rays, unlike other types, do not require a film to be put in the child's mouth. This is helpful for children who gag easily or who have small mouths. This X-ray has to be exposed for 12 to 18 seconds. The patient must be able to sit or stand still for that whole time.

Cephalometric projections show the entire head from the side. They are used to look at the teeth in relation to the jaw and the person's profile. Orthodontists use them to make an accurate diagnosis and develop a treatment plan.

Cone-beam computed tomography (CT) provides three-dimensional images. You stand or sit while the machine rotates around your head. The beam is cone-shaped, instead of fan-shaped as in a standard medical CT. A cone-beam scan uses less radiation than a medical CT scan but far more than any standard dental X-ray. The cone-beam CT is particularly useful for dental implant selection and placement.

Standard computed tomography (CT) usually must be done in a radiologist's office or a hospital. Typically, you will lie down while the image is taken. The radiation exposure is higher for this type of CT than for a cone-beam CT. A standard CT scan may be done to determine size and placement location for implants.

Digital X-rays

Digital radiographs are one of the newest X-ray techniques. Standard X-ray film is replaced with a flat electronic pad or sensor. The image goes into a computer, where it can be viewed on a screen, stored or printed out. Digital X-rays taken at different times can be compared using a process that highlights differences between the images. Tiny changes therefore can be caught earlier. With proper technique, digital X-rays use about half the radiation of conventional film.



Last updated August 8, 2012