X-rays are divided into two main categories, intraoral and extraoral. With intraoral X-rays, the X-ray film is inside the mouth. With extraoral X-rays, the film is outside the mouth.
The various types of intraoral X-rays show different aspects of the teeth:
Bite-wing X-rays (right) highlight the crowns of the back teeth. Dentists take one or two bite-wing X-rays on each side of the mouth. Each X-ray shows the upper and lower molars (back teeth) and bicuspids (teeth in front of the molars). These X-rays are called "bite-wings" because you bite down on a wing-shaped device that holds the film in place while the X-ray is taken. These X-rays help dentists find decay between back teeth.
Periapical X-rays (left) highlight only one or two teeth at a time. A periapical X-ray looks similar to a bite-wing X-ray. However, it shows the entire length of each tooth, from crown to root.
Depending on your oral health and dental history your dentist may recommend a full-mouth radiographic survey, or FMX. This includes every tooth, from crown to root to supporting structures. They are X-rayed using both bitewing and periapical radiographs.
Occlusal X-rays (right) are larger than most X-rays. They highlight tooth development and placement. Each X-ray shows nearly the full arch of teeth in either the upper or lower jaw.
Extraoral X-rays are less detailed than intraoral X-rays. For this reason, they are not used for detecting cavities or flaws in individual teeth.
Panoramic X-rays show the entire mouth on a single X-ray. They include all teeth on both upper and lower jaws. This type of X-ray requires a special machine. The tube head that emits the X-rays circles behind your head while the film circles across the front. That way, the full, broad view of the jaws is captured on one film. Because the machine moves in a set path, you have to be positioned carefully. Devices attached to the X-ray machine hold your head and jaw in place. All this may look and feel intimidating, but the process is very safe. It often uses less radiation than intraoral X-rays.
Cephalometric projections are X-rays taken of the entire side of the head. They are used to look at the teeth in relation to the jaw and the person's profile. Orthodontists use cephalometric projections to determine the best type of orthodontic treatment.
