Dental imaging allows a dentist to be proactive in dental healthcare by seeing potential problems before they become visible or painful for the patient. Both the patient and the dentist benefit from catching a potential problem in the early stages. There are two main types of dental imaging techniques that are used for diagnostic purposes: conventional X-rays and computed tomography (CT) imaging. The most common X-rays used in dental imaging are either intraoral or extraoral, depending on whether the X-ray film is inside or outside the mouth, and are classified by what they show as either bitewing X-rays, periapical X-rays or occlusal X-rays.

An intraoral X-ray, which is taken with the film inside the mouth, is the most common type. This type of X-ray enables the details of the tooth, root and jaw area to be seen. It can also be used to view teeth that are developing.

Bitewing X-rays focus on the crowns of the teeth in one section of the mouth and are used to check for tooth decay, bone density decay and gum disease. A periapical X-ray shows the entire teeth in one section, on either the top or the bottom of the mouth, and it can show any root or bone structure problems. The third type of intraoral dental imaging X-ray is the occlusal style, which shows entire tooth development and their placement.

An extraoral X-ray is taken from the outside of the mouth. This type does not have the detail of the intraoral X-ray but is very useful to find potential problems with the teeth and jaw. The extraoral X-ray also finds detail on impacted teeth and provides details on the relationship between the jaw and the teeth relationship as well as potential problems that might exist between the two. One type of extraoral dental imaging X-ray is a panoramic type which shows the entire mouth. A tomogram X-ray shows only a particular portion in detail.

It is sometimes helpful for the dentist to see the entire head for a diagnosis. In these cases, a cephalometric projection is used. Orthodontists often use this type of X-ray to work out their treatment plan for a patient.

For some patients, a dentist will order a sialography X-ray to look for gland problems. This type of X-ray requires the use of a dye, called a radiopaque contrast agent. The dye allows the soft tissue of the glands to show up on the film.

The last major tool a dentist uses for diagnostic purposes is the CT scan. This type of scan allows the inside of the head to be seen in a three-dimensional image. This type of test is normally conducted in a hospital setting instead of a dentist office.