Radiation Safety in Dental Radiography
Radiation Safety in Dental Radiography
The goal of dental radiography is to obtain diagnostic information while keeping the exposure to the patient and dental staff at minimum levels.
We know that x-rays, in sufficient doses, may produce harmful effects in human beings. H owever, we do not know the size of the risk—or even if there is any risk at all—from small doses of x-rays such as those used in dental radiography. It is the consensus of dental radiologists that the dosage from dental x-ray exposure is not harmful. However, the absence of conclusive proof that estab¬lishes the absence of risk means we must assume that there is the potential of some risk from diagnostic exposure. KODAK Publication D3-70, Compendium reprint, X-Rays: Detailed Answers to Frequently Asked Questions (see last page of ordering information), addresses some of the critical questions asked by patients regarding x-rays.
W henever we consider exposing patients to x-rays, the ALARA principle (As Low As Reasonably Achievable) applies. Any dose that can be reduced without major difficulty, great expense or inconvenience, should be reduced or eliminated.
Each of us is exposed to radiation from a variety of naturally occurring sources. Most exposure comes from breathing radon in the atmosphere. We’re exposed to cosmic radiation from space and terrestrial radiation from radioactive iso¬topes in stone and building materials. We’re even exposed from internal sources. A radioisotope of potassium is found in all living things.
In addition to these natural sources of radiation, we get small doses from miscellaneous sources including tobacco, watches with luminous dials, color television, and others. A significant source of man-made radiation is diagnostic exposure in the healing arts.Full Mouth D-speed/round collimation
Full Mouth F-speed/rectangular collimation
4-Film Bite-Wing D-speed/round collimation
12 3 4 5 6 7 Days of Environmental Exposure
It is estimated that a typical full-mouth intraoral examination, using D-speed film and round collimation, gives the patient the equivalent of 7 days of environmental background exposure. In contrast, by using F-speed film and rectangular collimation for a full-mouth exam, the patient receives the equivalent of 1.2 days of background exposure.
A typical panoramic examination gives the equivalent of about one day; and the usual 4-film (D-speed film) bite-wing study (round collimation), the equiva¬lent of 7 hours or approximately three tenths of a day. Note that other common procedures in medical radiology deliver much larger doses to the patient than dental x-ray studies.
The benefitsof the use of x-rays in dentistry certainly outweigh the riskswhen proper safety procedures are followed.
The dentist is responsible for all aspects of safe radiation exposure in the dental office.
The dentist selects the patient who needs radiographs, determines which radiographs are needed, takes or supervises the exposure of the films and interprets the images.
An important method for keeping patient exposure as low as reasonably achievable is the appropriate prescription of radiographs.Radiograph Guidelines
One way to do this is with the use of radiographic patient selection criteria.
Guidelines for the prescription of dental radiographs have been developed by an expert panel of dentists sponsored by the Public Health Service.
A free brochure is available from Eastman Kodak Company (see last page for ordering information) as KODAK Publication N-80A Guidelines for Prescribing Dental Radiographs. The guidelines are voluntary and are intended only as a decision-making aid for the dental practitioner. They are used only in conjunction with a carefully taken medical and dental history and a clinical examination.
Radiation Level Factors
In any case, once the decision has been made to prescribe x-rays, every reasonable effort must be made to minimize exposure to the patient and dental office personnel.
Interestingly, the same safety procedures that minimize exposure for both patient and operator can also increase the quality of the radiographic images.There are many factors that determine the level of radiation received by the patient during a radiographic examination. These include:
• The selection of the x-ray machine
• The use of technique factors that result in low patient exposure
• The use of fast films and screen/film combinations
• Adherence to correct film processing methods
• The use of collimators and filtration
• The use of lead aprons to protect the patient from unnecessary radiation
All x-ray equipment, regardless of date of manufacture, is subject to state and federal x-ray equipment regulations.
Although proper filtration is not usually a problem with modern equipment, older x-ray machines should be tested by a radiation physicist or qualified technician to verify the presence of the correct amount of filtration.
The kilovoltage or kVp setting is one of the most important factors that determines the image contrast, as well as dosage to the patient. In the 70-90 kVp range, biological risk esti¬mates from dental radiology are essentially the same and, therefore, the diagnostic need should be the determining factor for which kVp setting to use. Settings below 65 kVp are not recommended for routine dental radiography
because of higher patient exposures.