Dental x rays are pictures taken of the mouth area using high energy photons with very short wavelengths. They show the teeth and surrounding bone.
Dental x rays are effective in discovering tooth decay, broken fillings, fractured teeth, tumors, occlusal trauma, or impacted or ectopic teeth that would otherwise be unseen by the eye, in between the teeth and below the gum tissue.
Dental x rays are part of the dental examination for aiding in the diagnostic process. X rays are vital in the diagnosis of root canal treatment on checking the apical of the tooth and the surrounding structures for abscesses or bone loss. Without the aid of dental x rays, 60% of dental decay would be missed. Diagnostic x rays are essential in providing accurate information. The most common x rays taken are:
bitewing x rays (vertical and horizontal bitewings)
panoramic x rays
periapical x rays
occlusal x rays
Each is used in its own respective degree of diagnosis, with the bitewing x ray being the most common. Bitewings are the most effective in discovering tooth decay in between the teeth and on adjacent teeth. A bitewing shows only the top crown portion of the tooth structure. It is called a bitewing due to the way the patient can bite down and hold the film securely in place. The bitewing is good in diagnosing and evaluating periodontal conditions and bone levels between the teeth. They are also good in detecting tartar buildup.
The panoramic (a type of film used), or panorex (brand name) is also commonly taken on the initial visit to the dental office. This type of x ray makes a complete circle of the head from one ear to the other, to produce a complete two-dimensional representation of all the teeth. This x ray will also show bone structure beneath the teeth and the temporomandibular joint (TMJ). The panoramic is the most commonly used x ray in the aid of diagnostic decisions regarding third molar extractions (wisdom teeth) for people who are edentulous (the tooth is not there/has not erupted). This special x ray, however, has its advantages and disadvantages.
One advantage of the panoramic is that a broad area is imaged, showing many structures. Furthermore, the exposure level emits low radiation. The panoramic is excellent for evaluation of trauma, tooth development, and certain anomalies. A 1999 study at the University of Buffalo School of Dental Medicine demonstrated that calcifications in the carotid arteries, which were exposed on standard panoramic x rays, served as predictors of death from cardiovascular disease.
The main disadvantage of panoramic x rays is that the image shown does not provide the fine detail of a bitewing x ray. The procedure for taking a panoramic x ray is also somewhat confining to the patient, as the x ray machine takes a minute or more to fully encircle the head for the complete picture. These films are not good in aiding the diagnosis of decay, bone level, and certain types of periapical pathosis.
A periapical x ray is similar to a bitewing. This type of x ray shows the entire tooth area, from crown to root, and the bone surrounding the root from a side view. This type of film will reveal any root anomalies, changes in the bone and surrounding tissue, cysts, bone tumors, and abscesses. The fine detail in the periapical film is necessary in diagnosis and treatment planning, and is commonly taken during root canal treatment and crown restoration procedures.
Dental x rays
SOURCE: Alvarez, K.H. Williams & Wilkins' Dental Hygiene Handbook. Baltimore: Williams & Wilkins, 1998.
Show tooth crowns, alveolar crest, and interproximal area Check for cavities, look at previous dental work, and determine any bone loss
Check for residual pathologic conditions, or foreign bodies Detect retained teeth or root tips prior to denture construction
Full mouth series
Includes a number of periapical and bitewing x rays to identify conditions in the bones around the teeth and nerve tissue in the teeth Can be used as comparison for future problems
Shows large areas of the maxilla, mandible, or floor of the mouth Shows entire upper or lower bite and how primary or permanent teeth are developing
View the entire tooth from root to crown and its periodontal supporting structures Evaluate bone loss, determine causes of toothaches, and assess existing dental work
Supplement to periapical survey but not a substitute View general tooth development, check for specific problems such as trauma or temporomandibular joint (TMJ) pain
Occlusal films are least common. These films show the whole bite of the lower or upper jaw. Occlusal x rays, when taken, are mainly taken on children to show the eruption order of the permanent teeth.
X rays pass through hard and soft tissue in the mouth. The x ray beam is blocked by denser structures, such as teeth, fillings, jaws, and bones. Teeth appear lighter because fewer x rays go through the teeth to reach the film. Cavities and gum disease appear darker (shown by a dark spot in the tooth or loss of bone structure around the tooth) because of more x-ray penetration. On the film, the white images are the dense structures.
Cindy F. Ovard, RDA, The Gale Group Inc., Gale, Detroit,