The dosage of X-ray radiation received by a dental patient is typically small (around 0.005 mSv), equivalent to a few days' worth of background environmental radiation exposure, or similar to the dose received during a cross-country airplane flight (concentrated into one short burst aimed at a small area). Incidental exposure is further reduced by the use of a lead shield, lead apron, sometimes with a lead thyroid collar. Technician exposure is reduced by stepping out of the room, or behind adequate shielding material, when the X-ray source is activated.
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.
There's a newer 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 dental x ray 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 to previous images 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.