Dental radiography
A radiographic image is formed by a controlled burst of X-ray radiation which penetrates oral structures at different levels, depending on varying anatomical densities, before striking the film or sensor.
Dental caries, infections and other changes in the bone density, and the periodontal ligament, appear darker because X-rays readily penetrate these less dense structures.
The dosage of X-ray radiation received by a dental patient is typically small (around 0.150 mSv for a full mouth series[1]), equivalent to a few days' worth of background environmental radiation exposure, or similar to the dose received during a cross-country airplane flight (concentrated into one short burst aimed at a small area).
Digital X-rays, which replace the film with an electronic sensor, address some of these issues, and are becoming widely used in dentistry as the technology evolves.
The photographic montage at right depicts a situation in which extensive decay had been overlooked by a number of dentists prior to radiographic evaluation.
When there is extensive bone loss, the films may be situated with their longer dimension in the vertical axis so as to better visualize their levels in relation to the teeth.
Indications: 1) Detection of any sialoliths in submandibular salivary glands 2) Used to demonstrate unerupted lower 8's 3) Assess the size of lesions such as cyst or tumours in the posterior of body and angle of mandible[4] A full mouth series is a complete set of intraoral X-rays taken of a patients' teeth and adjacent hard tissue.
The full mouth series is composed of 18 films, taken the same day: The Faculty of General Dental Practice of the Royal College of Surgeons of England publication Selection Criteria in Dental Radiography[citation needed] holds that given current evidence full mouth series are to be discouraged due to the large numbers of radiographs involved, many of which will not be necessary for the patient's treatment.
An alternative approach using bitewing screening with selected periapical views is suggested as a method of minimising radiation dose to the patient while maximizing diagnostic yield.
[13] This technique is based on the principle of aiming the central ray of the X-ray beam at 90° to an imaginary line which bisects the angle formed by the long axis of the tooth and the plane of the receptor.
[15] Placing the photographic film or sensor outside the mouth, on the opposite side of the head from the X-ray source, produces an extra-oral radiographic view.
A lateral cephalogram is used to evaluate dentofacial proportions and clarify the anatomic basis for a malocclusion, and an antero-posterior radiograph provides a face-forward view.
It was later discovered that while panoramic films can prove very useful in detecting and localizing mandibular fractures and other pathologic entities of the mandible, they were not very good at assessing periodontal bone loss or tooth decay.
[18] There is increasing use of CT (computed tomography) scans in dentistry, particularly to plan dental implants;[19] there may be significant levels of radiation and potential risk.
Specially designed CBCT (cone beam CT) scanners can be used instead, which produce adequate imaging with a stated tenfold reduction in radiation.
[20] Although computed tomography offers high quality images and accuracy,[21] the radiation dose of the scans is higher than the other conventional radiography views, and its use should be justified.
In the recent years, CBCT has been developed specifically for its use in the dental and maxillofacial areas[4] to overcome the limitations of 2D imaging such as buccolingual superimposition.
[4] Indications of CBCT, according to the SEDENTEXCT (Safety and Efficacy of a New and Emerging Dental X-ray Modality) guidelines include:[4][26] Developing dentition Restoration of dentition (if conventional imaging is inadequate) Surgical Research A cross sectional diagnostic study compared and correlated bone sounding and open bone measurements with conventional radiograph and CBCT for periodontal disease.
[29][30] Other indications for radiographic localization include: separating the multiple roots/canals of teeth in endodontics, assessing the displacement of fractures, or determining the expansion or destruction of bone.
Alongside an efficient clinical examination, a dental radiograph of a high quality can show essential diagnostic information crucial for the ongoing treatment planning for a patient.
This is immensely variable due to differing use of: image receptor type, X-ray equipment, levels of training and processing materials etc.
In simplistic terms as depicted by the World Health Organisation, "this is a well designed quality assurance programme which should be comprehensive but inexpensive to operate and maintain."
These dental radiographies have been indicated as a risk factor for cancer of salivary gland and for intracranial tumors due to improper protection from radiation.
[43] The above regulations are specific to the United Kingdom; the EU and USA are principally governed by the directive 2013/59/Eurotam[44] and The Federal Guidance For Radiation Protection, respectively.
[45] The goal of all these standards, including others governing other countries, is primarily to protect the patient, operators, maintain safe equipment and ensure quality assurance.
