There are two main types of dental x-rays: intraoral (the x-ray film is inside the mouth) and extraoral (the x-ray film is outside the mouth).

Intraoral x-rays are the most common type of x-ray. There are several types of intraoral x-rays. Each 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 (the exposed surface) to the level of the supporting bone. Bite-wing x-rays detect decay between teeth and changes in the thickness of bone caused by gum disease. Bite wing x-rays can also help determine the proper fit of a crown (a cap that completely encircles a tooth) or other restorations (eg, bridges). It can also see any wear or breakdown of dental fillings.
  • Periapical x-rays show the whole tooth — from the crown, to beyond the root where the tooth attaches into the jaw. Each periapical x-ray shows all teeth in one portion of either the upper or lower jaw. Periapical x-rays detect any unusual changes in the root and surrounding bone structures.
  • Occlusal x-rays track the development and placement of an entire arch of teeth in either the upper or lower jaw.

Extraoral x-rays are used to detect dental problems in the jaw and skull. There are several types of extraoral x-rays.

  • Panoramic x-rays show the entire mouth area — all the teeth in both the upper and lower jaws — on a single x-ray. This x-ray detects the position of fully emerged as well as emerging teeth, can see impacted teeth, and help diagnosis tumors.
  • Tomograms show a particular layer or “slice” of the mouth and blur out other layers. This x-ray examines structures that are difficult to clearly see because other nearby structures are blocking the view.
  • Cephalometric projections show an entire side of the head. This x-ray looks at the teeth in relation to the jaw and profile of the individual. Orthodontists use this x-ray to develop each patient’s specific teeth realignment approach.
  • Another test that uses x-rays is called a sialogram. This test uses a dye, which is injected into the salivary glands so they can be seen on x-ray film (Salivary glands are a soft tissue that would not be seen with an x-ray.) Dentists might order this test to look for salivary gland problems, such as blockages, or Sjogren’s syndrome (a disorder with symptoms including dry mouth and eyes; this disorder can play a role in tooth decay).
  • Dental computed tomography (CT) is a type of imaging that looks at interior structures in 3-D (three dimensions). This type of imaging is used to find problems in the bones of the face such as cysts, tumors, and fractures.
  • Cone Beam CT is a type of x-ray that creates 3-D images of dental structures, soft tissue, nerves, and bone. It helps guide tooth implant placement and evaluates cysts and tumors in the mouth and face. It also can detect problems in the gums, roots of teeth, and jaws. Cone beam CT is similar to regular dental CT in some ways. They both produce accurate and high quality images. However, the way images are taken is different. The cone-beam CT machine rotates around the patient’s head, capturing all data in one single rotation. The traditional CT scan collects “flat slices” as the machine makes several revolutions around the patient’s head. This method also exposes patients to higher level of radiation. A unique advantage of cone beam CT is that it can be used in a dentist’s office. Dental computed CT equipment is only available in hospitals or imaging centers.
  • Digital imaging is a 2-D type of dental imaging that allows images to be sent directly to a computer. The images can be viewed on screen, stored, or printed out in a matter of seconds. Digital imaging has several other advantages compared with traditional x-rays. The image taken of a tooth, for example, can be enhanced and enlarged. This makes it easier for your dentist to see the tiniest changes that can’t be seen in an oral exam. Also, if necessary, images can be sent electronically to another dentist or specialist for a second opinion or to a new dentist (eg, if you move). Digital imaging also uses less radiation than x-rays.
  • MRI imaging is an imaging method that takes a 3-D view of the oral cavity including jaw and teeth. (This is ideal for soft tissue evaluation.)

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