Dental X-Rays From WebMD

There are two main types of dental X-rays: intraoral (meaning the Dental X-ray film is inside the mouth) and extraoral (meaning the Dental X-ray film is outside the mouth).

1. Intraoral Dental X-rays are the most common type of dental X-ray taken. These Dental X-rays provide a lot of detail and allow your dentist to find cavities, check the health of the tooth root and bone surrounding the tooth, check the status of developing teeth, and monitor the general health of your teeth and jawbone.
2. Extraoral Dental X-rays show teeth, but their main focus is the jaw and skull. These Dental X-rays do not provide the detail found with intraoral X-rays and therefore are not used for detecting cavities or for identifying problems with individual teeth. Instead, extraoral Dental X-rays are used to look for impacted teeth, monitor growth and development of the jaws in relation to the teeth, and to identify potential problems between teeth and jaws and the temporomandibular joint (TMJ, see document, "Temporomandibular disorders" for more information) or other bones of the face.

Types of Intraoral Dental X-Rays

There are several types of intraoral Dental X-rays, each of which shows different aspects of teeth.

• Bite-wing Dental X-rays show details of the upper and lower teeth in one area of the mouth. Each bite-wing shows a tooth from its crown to about the level of the supporting bone. Bite-wing Dental X-rays are used to detect decay between teeth and changes in bone density caused by gum disease. They are also useful in determining the proper fit of a crown (or cast restoration) and the marginal integrity of fillings.
• Periapical Dental X-rays show the whole tooth -- from the crown to beyond the end of the root to where the tooth is anchored in the jaw. Each periapical X-ray shows this full tooth dimension and includes all the teeth in one portion of either the upper or lower jaw. Periapical X-rays are used to detect any abnormalities of the root structure and surrounding bone structure.
• Occlusal Dental X-rays are larger and show full tooth development and placement. Each X-ray reveals the entire arch of teeth in either the upper or lower jaw.

Types of Extraoral Dental X-Rays

There are several types of extraoral Dental X-rays that your dentist may take.

• Panoramic Dental 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 Dental 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 Dental 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 Dental 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 Dental 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 Dental X-ray, which may be performed in a hospital or radiology center rather than a dentist's 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.

In the Pipeline

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 nice benefits of using this new technology including:

• 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 it's 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.

Source: WebMD (http://www.webmd.com/oral-health/guide/dental-x-rays-when-get-them)