Types of Extraoral X-Rays
There are several types of extraoral X-rays that your dentist may take.
Panoramic X-rays show the entire mouth area -- all the teeth in both the upper and lower jaws -- on a single X-ray. This type of X-ray is useful for detecting the position of fully emerged as well as emerging teeth, can identify impacted teeth, and aid in the diagnosis of tumors.
Tomograms show a particular layer or "slice" of the mouth while blurring out all other layers. This type of X-ray is useful for examining structures that are difficult to clearly see -- for instance, because other structures are in very close proximity to the structure to be viewed.
Cephalometric projections show the entire side of the head. This type of X-ray is useful for examining the teeth in relation to the jaw and profile of the individual. Orthodontists use this type of X-ray to develop their treatment plans.
Sialography involves visualization of the salivary glands following the injection of a dye. The dye, called a radiopaque contrast agent, is injected into the salivary glands so that the organ can be seen on the X-ray film (the organ is a soft tissue that would not otherwise be seen with an X-ray). Dentists might order this type of test to look for salivary gland problems, such as blockages or Sjögren's syndrome.
Computed tomography, otherwise known as CT scanning, shows the body's interior structures as a three-dimensional image. This type of X-ray, which may be performed in a hospital or radiology center or a dental office, is used to identify problems in the bones of the face, such as tumors or fractures. CT scans are also used to evaluate bone for the placement of dental implants and difficult extractions. This helps the surgeon avoid possible complications during and after a surgical procedure.
There's a newer dental X-ray technique that your dentist already may be using or may soon be using. It's called digital imaging. Instead of developing X-ray film in a dark room, the X-rays are sent directly to a computer and can be viewed on screen, stored, or printed out. There are several benefits of using this new technology:
- The technique uses less radiation than the typical X-ray and there is no wait time for the X-rays to develop -- the images are available on screen a few seconds after being taken.
- The image taken, of a tooth for example, can be enhanced and enlarged many times its actual size on the computer screen, making it easier for your dentist to show you where and what the problem is.
- If necessary, images can be electronically sent to another dentist or specialist -- for instance, for a second opinion on a dental problem -- to determine if a specialist is needed, or to a new dentist (if you move).
- Software added to the computer can help dentists digitally compare current images to previous ones in a process called subtraction radiography. Using this technique, everything that is the same between two images is "subtracted out" from the image, leaving a clear image of only the portion that is different. This helps dentists easily see the tiniest changes that may not have been noticed by the naked eye.