Dental Radiography (OPG, Periapical, Bitewing)
Dental radiography images the teeth, the supporting alveolar bone, the jaws, the maxillary sinuses and the temporomandibular joints. Intraoral films (periapical, bitewing, occlusal) show fine detail of individual teeth, and extraoral films (orthopantomogram or OPG, cephalometric, and cone beam computed tomography) show the whole dentition and facial skeleton.
The periapical view shows the whole tooth, from crown to root apex and the surrounding bone, and is used for infection, trauma, root canal treatment and root form. The bitewing view shows the crowns of upper and lower posterior teeth together with the crest of the alveolar bone, and is the best view for interproximal caries and early bone loss.
The occlusal view shows the floor of the mouth (salivary stones in the submandibular duct) and the palate. The OPG is a panoramic tomographic film of both jaws, all the teeth, the sinus floors and the temporomandibular joints in a single image. The cephalometric view is used by orthodontists to measure skeletal relationships.
Cone beam CT gives three dimensional images at a lower dose than medical CT and is used for implants, impacted teeth, complex roots, pathology and trauma. Effective doses are very low: about 0.001 to 0.005 mSv for a bitewing or periapical film, 0.01 to 0.03 mSv for an OPG, and 0.03 to 0.2 mSv for a cone beam CT of the jaws (higher for large fields of view).
Dental caries affects 60 to 90% of school children and nearly all adults in many populations, periodontal disease affects up to half of adults, and impacted third molars and periapical infection are among the commonest reasons for dental and facial surgery referral.
Radiographs reveal disease that is not clinically visible: about half of interproximal caries and nearly all early periapical and bone loss are found only on films. Radiography is justified by clinical findings and risk, not by a fixed schedule.
Indications. Dental pain, swelling, sinus tract or abscess (periapical views). Suspected caries between teeth in patients at risk (bitewings). Periodontal disease assessment (bitewings and periapical views). Trauma to teeth and jaws. Impacted or unerupted teeth, retained primary teeth, missing teeth and developmental anomalies (OPG).
Pre-operative assessment for third molar surgery, implants, orthodontic treatment and endodontics. Jaw lesions (cysts, tumours, infection). Unexplained jaw, facial or sinus pain. Temporomandibular joint pain or limitation. Salivary stones (occlusal view). Staging of dental development and dental age. Follow up after surgery or treatment of lesions.
Not for routine screening of low risk patients on a fixed schedule.
Contraindications and precautions. No absolute contraindication. Pregnancy: dental radiographs give a negligible dose to the foetus, and necessary imaging should not be withheld, with a thyroid collar and apron used. Children: use the lowest dose, rectangular collimation, fast receptors and a thyroid collar where it does not interfere with the image.
Remove dentures, earrings, necklaces, hairpins, spectacles and removable appliances from the field. Gagging patients may need modified films, such as an OPG. Dentoalveolar trauma should be imaged before manipulation.
Preparation and technique. For an OPG, the patient bites on a bite block, the chin rests on the support, the head is positioned in a midsagittal plane with the tongue against the palate, and the patient stays still during the 10 to 20 seconds of rotation. Intraoral films use a paralleling technique with a holder to reduce distortion. In children, smaller films and fewer views are used.
