Periapical Radiograph

General Description

A periapical radiograph is an intraoral diagnostic study in which X-rays or other ionizing radiation are applied to obtain detailed images of a tooth, including the apex (the terminal part of the root), the root, the surrounding bone tissue, the periodontal space, and the interdental areas.

Body tissues absorb more radiation the denser they are, which results in different shades appearing in the image:

• The tooth and bone tissue are denser, absorb more radiation, and appear almost white.
• The gums, which are less dense soft tissues, appear in gray tones.
• Metal and materials used in previous procedures, such as fillings and orthodontics, appear completely white.
• Cavities, abscesses, and other periapical lesions appear in dark tones because they do not absorb radiation.

When Is It Indicated?

A periapical radiograph is performed to analyze the entire tooth and detect any abnormalities that cannot be observed through a physical examination or a panoramic dental radiograph. Some of the conditions that can be diagnosed include:

• Periodontal problems such as bone loss, periodontal pockets, or calculus below the gum or between teeth.
• Periapical cysts.
• Dental cavities and their level of impact on the enamel, dentin, or nerve.
• Interproximal cavities (between the teeth).

Additionally, a periapical radiograph is used as a monitoring and follow-up method for various dental treatments.

How Is It Performed?

A periapical radiograph is taken by placing small radiation receptor plates inside the mouth. X-rays are emitted from an external device, and upon striking the tissues, they are recorded by the plate, forming an image. In older equipment, a radiation-sensitive photographic plate was used, which then needed to be developed. Currently, in digital periapical radiography, digital sensors are used to generate the image automatically and display it on a computer screen.

There are two methods for performing a periapical radiograph:

• Bisecting Angle Technique: The receptor plate is placed as close as possible to the tooth, at an angle with the tooth’s longitudinal axis. The central X-ray beam is directed perpendicularly to the bisecting line formed by the plate and the tooth. This is the most commonly used technique as it is simpler, although it produces greater geometric distortion in the image.
• Paralleling Technique: The plate is positioned parallel to the tooth’s longitudinal axis, and the beam is directed perpendicularly to both the tooth and the plate. This technique is more precise and results in less geometric distortion.

Risks

A periapical radiograph exposes the patient to radiation, which has been linked to the development of certain types of cancer and other health problems. However, the exposure time is very short, and the radiation dose received in this test is minimal (0.005 mSv, equivalent to the natural background radiation an adult is exposed to in a day), making it a completely safe procedure, especially when additional protective measures are used, such as the placement of lead aprons to shield other body parts. For pregnant women, these precautions are essential, as radiation can affect the fetus.

What to Expect from a Periapical Radiograph

A periapical radiograph is performed with the patient seated or semi-reclined in the dental chair. After removing any possible metal objects, a lead apron is placed on the patient to protect the torso and neck from unnecessary radiation exposure. Then, the receptor plate is wrapped in a disposable plastic cover and inserted into the patient's mouth. To facilitate the process, especially when using the paralleling technique, a positioner may also be inserted—this device ensures the correct placement of the plate in the mouth and the proper alignment of the X-ray emitter.

The patient must keep their mouth closed around the receptor and remain still with relaxed oral muscles during the imaging process, as movement can cause blurring in the images.

The X-ray application to capture the images lasts only a few seconds, and the entire procedure typically takes no more than ten minutes. It is a completely painless study that does not cause any discomfort beyond the minor inconvenience of having the receptor in the mouth and keeping it still. After the procedure, the patient can resume their routine normally.

Specialties That Request a Periapical Radiograph

A periapical radiograph is commonly requested in the fields of dentistry and oral and maxillofacial surgery.