Dental radiographsare commonly calledX-rays.Dentistsuseradiographsfor many reasons: to find hidden dental structures, malignant or benign masses, bone loss, and cavities.
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. Teeth appear lighter because less radiation penetrates them to reach the film.Dental caries, infections and other changes in the bone density, and theperiodontal ligament, appear darker because X-rays readily penetrate these less dense structures. Dental restorations (fillings, crowns) may appear lighter or darker, depending on the density of the material.
The dosage of X-ray radiation received by a dental patient is typically small (around 0.150mSvfor a full mouth series, according to the American Dental Association website), 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). Incidental exposure is further reduced by the use of a lead shield, lead apron, sometimes with a lead thyroid collar. Technician exposure is reduced by stepping out of the room, or behind adequate shielding material, when the X-ray source is activated.
Oncephotographic filmhas been exposed to X-ray radiation, it needs to be developed, traditionally using a process where the film is exposed to a series of chemicals in a dark room, as the films are sensitive to normal light. This can be a time-consuming process, and incorrect exposures or mistakes in the development process can necessitate retakes, exposing the patient to additional radiation. 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. They may require less radiation and are processed much more quickly than conventional radiographic films, often instantly viewable on a computer. However digital sensors are extremely costly and have historically had poorresolution, though this is much improved in modern sensors.
This preoperative photo of tooth #3,(A), reveals no clinically apparent decay other than a small spot within the central fossa. In fact, decay could not be detected with anexplorer. Radiographic evaluation,(B), however, revealed an extensive region of demineralization within the dentin (arrows) of themesialhalf of the tooth. When aburwas used to remove theocclusalenameloverlying the decay,(C), a large hollow was found within the crown and it was discovered that a hole in the side of the tooth large enough to allow the tip of the explorer to pass was contiguous with this hollow. After all of the decay had been removed,(D), thepulp chamberhad been exposed and most of the mesial half of the crown was either missing or poorly supported.
It is possible for bothtooth decayandperiodontal diseaseto be missed during a clinical exam, and radiographic evaluation of the dental and periodontal tissues is a critical segment of the comprehensive oral examination. The photographic montage at right depicts a situation in which extensive decay had been overlooked by a number of dentists prior to radiographic evaluation.
Theperiapical(PA) view is taken of bothanterior and posteriorteeth. The objective of this type of view is to capture the tip of the root on the film. This is often helpful in determining the cause of pain in a specific tooth, because it allows a dentist to visualize the tooth as well as the surrounding bone in their entirety. This view is often used to determine the need forendodontic therapyas well as to visualize the successful progression of endodontic therapy once it is initiated. It can be used in case of detectionhyperdontia(supernumerary teeth) & impacted teeth.
The nameperiapicalis derived from the Greekperi, which means "around," andapical, which means "tip."
The bitewing view is taken to visualize the crowns of the posterior teeth and the height of thealveolar bonein relation to thecementoenamel junctions, which are the demarcation lines on the teeth which separate tooth crown from tooth root. Routine bitewing radiographs are commonly used to examine for interdental caries and recurrent caries under existing restorations. 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. Because bitewing views are taken from a more or less perpendicular angle to thebuccalsurface of the teeth, they more accurately exhibit the bone levels than do periapical views. Bitewings of the anterior teeth are not routinely taken. The namebitewingrefers to a little tab of paper or plastic situated in the center of the X-ray film, which when bitten on, allows the film to hover so that it captures an even amount ofmaxillaryandmandibularinformation.
Theocclusalview reveals the skeletal orpathologicanatomy of either the floor of the mouth or thepalate. The occlusal film, which is about three to four times the size of the film used to take a periapical or bitewing, is inserted into the mouth so as to entirely separate the maxillary and mandibular teeth, and the film is exposed either from under the chin or angled down from the top of the nose. Sometimes, it is placed in the inside of the cheek to confirm the presence of asialolithin Stenson's duct, which carriessalivafrom theparotid gland. The occlusal view is not included in the standard full mouth series.
A full mouth series is a complete set of intraoral X-rays taken of a patients' teeth and adjacent hard tissue.This is often abbreviated as either FMS or FMX (or CMRS, meaning Complete Mouth Radiographic Series). The full mouth series is composed of 18 films, taken the same day:
two maxillary premolar periapicals (left and right)
two mandibular molar periapicals (left and right)
two mandibular premolar periapicals (left and right)
six anterior periapicals
two maxillary canine-lateral incisor periapicals (left and right)
two mandibular canine-lateral incisor periapicals (left and right)
two central incisor periapicals (maxillary and mandibular)
TheFaculty of General Dental Practiceof theRoyal College of Surgeons of EnglandpublicationSelection Criteria in Dental Radiographyholds that given currentevidencefull 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. Contrary to advice that emphasises only conducting radiographs when in the patient's interest, recent evidence suggests that they are used more frequently when dentists are paid under fee-for-service