Dental X-rays help dentists visualize diseases of the teeth and surrounding tissue that cannot be seen with a simple oral exam. They also help the dentist find and treat dental problems early on, which can help save you money, unnecessary discomfort, and maybe even your life.
What Problems Can Dental X-Rays Detect?
In adults, dental X-rays can be used to:
- Show areas of decay that may not be visible with an oral exam, especially small areas of decay between teeth
- Identify decay occurring beneath an existing filling
- Reveal bone loss that accompanies gum disease
- Reveal changes in the bone or in the root canal resulting from infection
- Assist in the preparation of tooth implants, braces, dentures, or other dental procedures
- Reveal an abscess (an infection at the root of a tooth or between the gum and a tooth)
In children, dental X-rays are used to:
- Watch for decay
- Determine if there is enough space in the mouth to fit all incoming teeth
- Determine if primary teeth are being lost quickly enough to allow permanent teeth to come in properly
- Check for the development of wisdom teeth and identify if the teeth are impacted (unable to emerge through the gums)
- Reveal other developmental abnormalities, such as cysts and some types of tumors
Types of Dental X-Rays
There are two main types of dental X-rays: intraoral (meaning the X-ray film is inside the mouth) and extraoral (meaning the X-ray film is outside the mouth).
- Intraoral X-rays are the most common type of dental X-ray taken. These 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.
- Extraoral X-rays show teeth, but their main focus is the jaw and skull. These 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 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 temporomandibular disorders for more information) or other bones of the face.
Types of Intraoral X-Rays
There are several types of intraoral X-rays, each of which shows different aspects of teeth.
- Bite-wing 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 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 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 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 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.
How Often Should Teeth Be X-Rayed?
This often depends on your medical and dental history and current condition. Some people may need X-rays as often as every six months; others with no recent dental or gum disease and who visit their dentist regularly may get X-rays only every couple of years. If you are a new patient, your dentist may take X-rays as part of the initial exam and to establish a baseline record from which to compare changes that may occur over time.
Some general guidelines your dentist may follow regarding the frequency of dental X-rays is as follows:
Dental X-Ray Schedule for Children, Adolescents, and Adults
|New patients||Repeat patient, high risk or decay is present||Repeat patient, no decay, not at high risk for decay||Current or history of gum disease||Other comments|
|Children (before eruption of first permanent tooth)||X-rays if the teeth are touching and all surfaces cannot be visualized or probed||X-rays taken every 6 months until no decay is present||X-rays taken every 12 to 24 months if the teeth are touching and all surfaces cannot be visualized or probed||X-rays of areas where disease is seen in the mouth||X-rays to check for growth and development are usually not indicated at this age|
|Adolescents (before eruption of wisdom teeth)||A full series of X-rays is indicated when there is evidence of dental disease or history of extensive decay.||X-rays taken every 6 to 12 months until no decay is present||X-rays taken every 18 to 36 months||X-rays of areas where disease is seen in the mouth||X-rays should be taken to check for development of wisdom teeth|
|Adults with teeth||A full series of X-rays is indicated when there is evidence of dental disease or history of extensive decay.||X-rays taken every 12 to 18 months||X-rays taken every 24 to 36 months||X-rays of areas where disease is seen in the mouth||X-rays to check for growth and development are usually not indicated.|
|Adults without teeth||X-rays are usually not indicated unless specific dental disease is clinically present.|
People who fall into the high risk category who may need X-rays taken more frequently include:
- Children. They generally need more X-rays than adults because their teeth and jaws are still developing and because their teeth are smaller. As a result, decay can reach the inner part of the tooth, dentin, quicker and spread faster.
- Adults with extensive restorative work, such as fillings to look for decay beneath existing fillings or in new locations
- People who drink a lot of sugary beverages. The sugary environment creates a perfect situation for cavities to develop.
- People with periodontal (gum) disease. X-rays can monitor bone loss.
- People who have dry mouth -- called xerostomia -- whether due to medications (such as antidepressants, anti-anxiety drugs, antihistamines, and others) or disease states (such as Sjögren's syndrome, damaged salivary glands, radiation treatment to head and neck). Dry mouth conditions can lead to the development of cavities.
- Smokers. The X-rays monitor bone loss resulting from periodontal disease (smokers are at increased risk of periodontal disease).
How Safe Are Dental X-Rays?
Exposure to all sources of radiation -- including the sun, minerals in the soil, appliances in your home, and dental X-rays -- can damage the body's tissues and cells and can lead to the development of cancer. The dose of radiation you are exposed to during the taking of dental X-rays is extremely small, especially if your dentist is using digital X-rays.
Advances in dentistry over the years have led to a number of measures that minimize the risks associated with X-rays. However, even with the advancements in safety, the effects of radiation are added together over a lifetime. So every little bit of radiation you receive counts.
If you are concerned about radiation exposure due to X-rays, talk to your dentist about how often X-rays are needed and why they are being taken. While some people need X-rays taken more frequently, current guidelines require that X-rays be given only when needed for clinical diagnosis.