There are two main types of dental X-rays: intraoral (meaning the X-ray film
is inside the mouth) and extraoral (meaning the X-ray film is outside the
Intraoral X-rays are the most common type of dental X-ray
taken. These X-rays provide a lot of detail and allow your dentist to find
cavities, check the health of the tooth root and bone surrounding the tooth,
check the status of developing teeth, and monitor the general health of your
teeth and jawbone.
Extraoral X-rays show teeth, but their main focus is the
jaw and skull. These X-rays do not provide the detail found with intraoral
X-rays and therefore are not used for detecting cavities or for identifying
problems with individual teeth. Instead, extraoral X-rays are used to look for
impacted teeth, monitor growth and development of the jaws in relation to the
teeth, and to identify potential problems between teeth and jaws and the
temporomandibular joint (TMJ, see document, "Temporomandibular disorders" for more information) or other
bones of the face.
Types of Intraoral X-Rays
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
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.
Types of Extraoral X-Rays
There are several types of extraoral X-rays that your dentist may wish to
Panoramic X-rays show the entire mouth area -- all the
teeth in both the upper and lower jaws -- on a single X-ray. This type of X-ray
is useful for detecting the position of fully emerged as well as emerging
teeth, can identify impacted teeth and aid in the diagnosis of tumors.
Tomograms show a particular layer or "slice" of
the mouth while blurring out all other layers. This type of X-ray is useful for
examining structures that are difficult to clearly see -- for instance, because
other structures are in very close proximity to the structure to be
Cephalometric projections show the entire side of the
head. This type of X-ray is useful for examining the teeth in relation to the
jaw and profile of the individual. Orthodontists use this type of X-ray to
develop their treatment plans.
Sialography involves visualization of the salivary glands
following the injection of a dye. The dye, called a radiopaque contrast agent,
is injected into the salivary glands so that the organ can be seen on the X-ray
film (the organ is a soft tissue that would not otherwise be seen with an
X-ray). Dentists might order this type of test to look for salivary gland
problems, such as blockages or Sjogren's syndrome.
Computed tomography, otherwise known as CT scanning, shows
the body's interior structures as a three-dimensional image. This type of
X-ray, which is performed in a hospital rather than a dentist's office, is used
to identify problems in the bones of the face, such as tumors or
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