Dental x-rays are a type of picture of the teeth and mouth. X-rays are a form of electromagnetic radiation, just like visible light. They are of higher energy, however, and can penetrate the body to form an image on film.

Structures that are dense (such as silver fillings or metal restoration) will block most of the photons and will appear white on developed film. Structures containing air will be black on film, and teeth, tissue, and fluid will appear as shades of gray.

The test is performed in the dentist's office. There are four types of x-rays:

• Bitewing
• Periapical
• Palatal (also called occlusal)
• Panoramic

The bitewing is when the patient bites on a paper tab and shows the crown portions of the top and bottom teeth together.

The periapical shows one or two complete teeth from crown to root.

A palatal or occlusal x-ray captures all the upper and lower teeth in one shot while the film rests on the biting surface of the teeth.

A panoramic x-ray requires a special machine that rotates around the head. The ex-ray captures the entire jaws and teeth in one shot. It's used to plan treatment for dental implants, check for impacted wisdom teeth, and detect jaw problems. A panoramic x-ray is not good for detecting cavities, unless the decay is very advanced and deep.

In addition, many dentists are taking x-rays using digital technology. The image runs through a computer. The amount of radiation transmitted during the procedure is less than traditional methods.

There is no special preparation. Notify the dentist if you are pregnant.

The x-ray itself causes no discomfort. Some people find that biting on the piece of film makes them gag. Slow, deep breathing through the nose usually relieves this feeling.