X-rays

Dental procedure
Overview
Panoramic dental X-ray for assessment of developmental status.

A panoramic radiograph allows the dentist to assess a patient’s growth and development status, check for missing or extra teeth, and evaluate the teeth and bones of the facial area for disease processes.

Dental X-rays (radiographs) are used by dental health professionals to evaluate hard tissue (teeth and bones) for signs of disease process or abnormalities.

The type of X-rays prescribed is determined by the type of information the dentist needs to evaluate a patient’s dental condition and plan any required treatment. X-ray imaging techniques that are commonly used in dentistry include bitewings; cephalometric X-rays (cephs); cone beam computed tomography (CBCT) scans; full mouth series of X-rays; occlusal X-rays; panoramic X-rays (pano films); and periapical X-rays.

Orthodontic tracings on a lateral cephalometric X-ray (radiograph).

A cephalometric radiograph is a type of X-ray image showing the bones of the skull, mandible, and cervical spine, as well as the teeth. The orthodontist measures the relative position and angles of certain bones, and of the teeth to determine the extent and type of orthodontic treatment needed by the patient. (Image courtesy Thomas J. Melcher, DDS, MS).

Radiographs are an essential diagnostic tool of dental professionals. Even with promising emerging technologies, there is little doubt X-ray technology will continue to be a primary means of identifying and recording problems for the foreseeable future.

Since dental benefits became available, there has been controversy about how often a patient should be evaluated with routine X-rays. Unfortunately, the decision is sometimes made on the basis of how often dental plans will pay for them, rather than how often the patient’s dental history (e.g. decayed, missing and filled teeth); clinical findings (chips, cracks, decay, gum disease, etc.); and ALARA (As Low As Reasonably Achievable) exposure principles suggest they should be prescribed. Dental plans typically base payment of benefits for X-rays on the annual needs of an average plan participant. However, some patients may require more frequent imaging, and some less than others, based on individual needs.

Your dentist is the best qualified individual to evaluate your dental condition and prescribe appropriate radiographs on an appropriate interval.

The process

The following is the general process for bitewing and periapical X-rays:

  • The radiographic technician will place a lead apron around your upper body, and and a lead collar around your neck. This is done as a safety measure, to shield sensitive tissues (thyroid gland, etc.) that are not part of the tissue being examined against direct or reflected ionizing radiation from the X-ray imaging device. Although dental X-rays produce low levels of ionizing radiation, it’s good to be conservative with exposure.
  • A radiographic imaging film or digital imaging sensor will be placed in your mouth behind the tooth or teeth to be imaged, and you will be asked to bite gently on a stabilizing device that holds the imaging film or sensor in position. This can produce momentary discomfort that is typically minor.
  • The X-ray tubehead will be aligned with the imaging sensor or film near your cheek.
  • X-ray exposure is initiated when the technician presses a switch. The amount and duration of the exposure varies according to the type of radiograph that is being exposed, and the type of tissue that is being examined. Normally, the exposure is rapid, lasting only a fraction of a second.
  • The image will be processed, either by traditional film processing techniques, or with some type of digital scanner. Traditional film takes 5 to 10 minutes to process. Digital images may appear within seconds of exposure, depending on the type of digital equipment being used.
  • Your dentist will analyze your radiographs for any sign of abnormalities, and will include them as part of your diagnostic record.
  • Your dentist will make recommendations appropriate to the diagnostic findings.
Advantages and benefits of dental X-rays

Dental radiographs provide diagnostic information that cannot currently be obtained by any other practical means. The dentist can tell if problems are arising in the tooth or bone, and can prescribe and perform effective treatment to solve any problem before it becomes more serious. It is generally believed that the risks of dental radiographs are exceedingly low compared to the benefits conferred by having them done.

Disadvantages and risks

X-rays, like all forms of ionizing radiation, have a cumulative effect on human tissues. Some tissues, such as glandular tissues (for example, thyroid, etc.), are more vulnerable than others to these effects. The effects, at high enough doses are harmful. The goal of dental radiography is to obtain the necessary diagnostic information, while keeping the exposure levels to the patient and staff As Low As Reasonably Achievable, also known as the ALARA principle. It is the consensus of radiation physicists, and radiologists alike that dental X-ray exposure is low enough not to be harmful, especially when high speed film, phosphor intensifying screens, proper collimation, lead shielding aprons, and digital radiography (where available) are used. However, it is important that all radiographic imaging follow ALARA principles.

Keep in mind that all living things are continually exposed to ionizing radiation from a variety of sources, the most common of which is radon gas in the atmosphere. We are also continually exposed to radiation from the sun and space, as well as terrestrial sources like stone and building materials. A radioactive isotope of potassium is found in all living creatures.

For comparison purposes, consider the following: A full mouth series of dental X-rays using D-speed film imparts about the same exposure to X-rays as walking around in your normal environment for 7 days. Using F-speed film for the same imaging series cuts the exposure to a little over 1 day. Digital radiography sensors are so good at detecting X-rays and building a diagnostic image from them, that as little as a tenth of the dose required for X-ray imaging film may be used. With F-speed film, a typical 4-bitewing X-ray series is equal to about an hour-and-a-half of background radiation. A single periapical X-ray using F-speed film is about 20 minutes of background radiation equivalent. And a single digital radiograph may be a fraction of that.

Keep in mind that radiographs are often more suggestive of problems than they are conclusive. This is why effective oral diagnosis frequently requires several different diagnostic tools to be used.

Other care that may be needed

Generally, if a radiograph is exposed, an examination will be performed, and a separate fee will be charged. When radiographs are exposed as part of a periodic checkup, some type of hygiene procedure will also be performed and charged (for example, a prophylaxis). Emergency visits to the dentist frequently involve other diagnostic procedures like pulp vitality testing, in which heat, cold and electrical tests may be performed to rule out tooth abscesses. Some type of pain-relieving procedure may be performed, based on the diagnostic findings, and charged as a separate procedure. Diagnostic photographs may be taken to enhance the diagnostic information that is gathered. Study models (casts) may also be made to complete the diagnostic picture. Laser caries detection and infrared measurements are newer techniques for evaluating teeth for decay (caries).

Other treatment options

Dental problems can sometimes be diagnosed without radiographs. However, keep in mind that radiographs are also a good way to permanently record the problem(s). They also establish a legal record of the treatment. Other diagnostic tools used by dental professionals include:

  • Visual and tactile examinations in which different types of hand instruments are used to probe and measure on and around the teeth. Reporting the findings is subjective, however, as no objective record is normally produced. There is controversy as to whether use of a dental explorer can actually cause harm by transferring decay-producing bacteria from one tooth to another, or whether the instruments themselves are capable of harming the tooth directly. The majority of dentists continue to use them, as they have a long and successful history of detecting early pit and fissure cavities, cracks, and other defects in teeth.
  • Use of laser caries detection devices is becoming more common. These devices measure the difference in fluorescence patterns of healthy and unhealthy tooth enamel. Their use is based on the fact that healthy tooth enamel does not fluoresce, whereas decayed tooth enamel does—in proportion to the amount of caries (decay) present. Unfortunately, laser fluorescence meters do not produce a permanent record like a radiograph, although the readings are generally written down by a dental auxiliary, and entered into the patient record.
  • A new science called visible light imaging is emerging that uses visible light to image teeth. Among these technologies is Digital Fiber-Optic TransIllumination (DIFOTI), which has the advantage of producing no harmful ionizing radiation, while producing an image that can be saved. Its use is not very widespread, however.
  • AC Impedance Spectroscopy (for example, CarieScan®)—a device that measures changes in the mineral density of tooth enamel, such as occur when the tooth begins to decay.
  • Diagnostic photographs are very useful for recording and communicating problems, especially when magnification is used.
What if I do nothing?

If a dentist cannot visualize the dental hard tissues and jaw bones, he or she will have an incomplete picture of your dental health status.

  • Refusing bitewing radiographs may mean tooth decay goes undetected for prolonged periods, leading to the possibility of pain, infection, and un-necessary tooth loss. Nonetheless, for people who have never had dental caries or periodontal disease, and who are considered low risk for dental disease, the length of time between radiographic surveys can frequently be extended. People who have a history of tooth decay or periodontal disease should be more closely monitored.
  • Refusing periapical radiographs may mean infections, fractures or other disease process inside a tooth / surrounding bone go undiagnosed. This can lead to (potentially expensive) treatment of a tooth that may not be in the mouth for very long.
  • Refusing panoramic radiographs may mean that abnormal developmental conditions such as congenitally missing teeth, and disease processes like infections, cysts or tumors go undiagnosed. If these conditions aren’t diagnosed in a timely manner, the ability to plan for and effectively treat the condition may be compromised. The severity of the outcome depends on the condition that is overlooked.
  • Refusing cephalometric radiographs may mean that essential growth and development, or evidence of disease process or fractures may be overlooked. Again, the severity of the outcome depends on the condition that is overlooked.
  • Refusing cone beam computed tomography (CBCT) scans may mean that important three-dimensional relationships between nerves, arteries teeth and the jaw bones are not adequately understood. The severity of the outcome depends on the positional relationships that are not understood. An example of a poor treatment outcome that could occur as a result of refusing to be imaged is that permanent injury to a major nerve might occur that could leave the patient without feeling in their lip.

Author: Thomas J. Greany, D.D.S.
Editor: Ken Lambrecht
This page was reviewed by members of our review board.

This page was last updated on July 3, 2015.

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Caries
Casts
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Missing Teeth
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Orthodontics
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For dentists and dental school students

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Links to additional (more technical) dental information on the Web

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Background information

Assessing the accuracy of caries diagnosis via radiograph—Film versus print
Otis, Linda L., DDS and Sherman, Robert G., DMD
The Journal of the American Dental Association
2005 136 (3): 323-330

Filmless Imaging—The uses of digital radiography in dental practice
Van Der Stelt, Paul F., DDS, PhD
The Journal of the American Dental Association
2005 136 (10): 1379-1387

Imaging of occlusal dental caries (decay) with near-IR light at 1310nm
Buhler, Christopher, et.al.
Optics Express: The International Electronic Journal of Optics
2005 13 (2): 573-582

Minimally invasive dentistry
Murdoch-Kinch, Carol Anne, DDS, PhD, and McLean, Mary Ellen, DDS
The Journal of the American Dental Association
2003 134: 87-95

The technologically well-equipped dental office
Schleyer, Titus K.L., DMD, PhD, et al.
The Journal of the American Dental Association
2003 134 (1): 30-41

Diagnosis of Occlusal Caries: Part I. Conventional Methods
McComb, Dorothy, BDS, MScD, FRCD(C), and Tam, Laura E., DDS, MSc
Journal of the Canadian Dental Association
2001 67 (8): 454-457

Diagnosis of Occlusal Caries: Part II. Recent Diagnostic Technologies
McComb, Dorothy, BDS, MScD, FRCD(C), and Tam, Laura E., DDS, MSc
Journal of the Canadian Dental Association
2001 67 (8): 459-463

Digital enhancement of radiographs: Can it improve caries diagnosis?
Shrout, Michael K., DMD, et al.
The Journal of the American Dental Association
1996 127 (4): 469-473

An algorithm for ordering pretreatment orthodontic radiographs
Atchison, Kathryn A., DDS, MPH, et al.
American Journal of Orthodontics & Dentofacial Orthopedics
1992 102 (1): 29-44

Quantum Detection of Tooth Decay
Hamilton, Tyler
MIT Technology Review

Radiation protection: ALARA
Wikipedia web site
Last viewed: 9/23/2010
Editor’s notes: An illustration of the ALARA principal (As Low As Reasonably Achievable exposure to ionizing radiation, including X-rays)

The American Academy of Oral and Maxillofacial Radiology
The American Academy of Oral and Maxillofacial Radiology web site
Last viewed: 9/23/2010
Editor’s notes: This organization supports safe imaging techniques, prescription behaviors, and interpretation of images obtained using ionizing radiation.

Information you may wish to read before making a decision on treatment

A systematic review of the performance of a laser fluorescence device for detecting caries
Bader, James D., DDS, MPH and Shugars, Dan A., DDS, PhD
The Journal of the American Dental Association
2004 135 (10): 1413-1426

Caries detection using laser fluorescence
Croll T.P., Tyma M.S.
Compendium of Continuing Education in Dentistry
2001 22 (10): 838-842, 844