Dental Radiography: Doses and Film Speed
The FDA is encouraging dental professionals to make a simple and economic switch to "faster" X-ray film to further reduce your radiation exposure. This article explains how they can do it.
Dental intraoral radiography is a very common exam performed in the United States, with approximately 100 million done each year. In 1999, The Nationwide Evaluation of X-ray Trends (NEXT) program performed a survey of dental facilities performing this exam throughout the United States. NEXT is a federal-state cooperative effort to document through annual surveys the state of clinical practice for selected radiographic examinations.
The 1999 NEXT Dental survey provided an insight into the practice of dental radiography. Among the extensive information gathered, the survey documented the number of films taken per visit, the types of film used by dental practitioners, and measures of patient exposure. Among the findings, the survey illustrated that the majority of films taken during a routine dental intraoral examination involved either two films (32% of facilities surveyed) or four films (35% of facilities surveyed), with an overall average of close to four (3.5) films observed.
The film typically used for the intraoral bitewing exam falls into three film speed classes - D (slowest), E and F-speed (fastest). Like photographic film, the faster the film, the less exposure it needs. Film speed can be an important aspect in determining the amount of radiation exposure received by a patient. The greater the film speed, the lesser the exposure received by the patient. The types of film used by dental practices in this survey varied, with D-speed film comprising approximately 70% of the film used, E-speed film about 21%, and F-speed film about 9%.
For the 1999 Survey, the amount of radiation a person is typically subjected to for D-speed film was 1.7 milligray (mGy) (a unit of radiation exposure) per film, and 1.3 mGy for E-speed film. These results show a 23% reduction in exposure with the use of E-speed film over D-speed film. Major dental film manufacturers and literature on this subject have extensively reported similar differences in exposure between film speeds. Results reported in literature illustrate that switching from D to E speed produced a 30-40% reduction in exposure. Switching from E to F speed produced a 20-25% reduction in exposure, and switching from D to F-speed film produced a 60% reduction in exposure.
When looking at the above results, one should ask whether there is need or cause for concern. As noted in the NEXT survey, 70% of dental practitioners chose D-speed film with its higher patient dose. Dental procedures are repeated from childhood throughout life. There is a slight risk of excess cancers with today's children at greater risk.
The limited use of E or F-speed films compared with D-speed films is often due to misconceptions about price, clinical film quality, and processing. A comparison of one manufacturer's D-speed film to E-speed or F-speed film shows no significant clinical differences in quality between the films. Using E-speed or F-speed film provides a similar mean-correct diagnosis, comparable sensitometric properties (i.e. technical aspects of film imaging) and similar clarity of film compared to D-speed film. E-speed or F-speed film is processed without significant changes in processing practices to those that are used for D-speed film.
Regarding the price difference between E- or F-speed film and D-speed film, the related costs boil down to a matter of several cents increase per film from D to F! As listed by an internet on-line vendor of dental film, a package (usually containing 100 or 150 films) of F-speed film is only $4 more than for the same package of D-speed film. This amount averages to only pennies per film, with a one-third reduction in exposure to the patient.
Conclusion: The facts that E- and F-speed film products offer significant exposure reduction compared with D-speed film, cost approximately the same and offer comparable clinical benefits strongly support a change of practice for those facilities that continue to use slow-speed film products that contribute to patients' exposures which are greater than necessary. Ask your dentist or dental technician if they use the faster (E or F) speed film and tell them the reasons for your inquiry.
1. Conference of Radiation Control Program Directors, Inc. (CRCPD), Publication E-03-6, "NEXT Tabulation and Graphical Summary of the 1999 Dental Radiography Survey", November 2003
2. ADA Council on Scientific Affairs "An update of radiographic practices: information and recommendations", JADA, Vol. 132, February 2001
3. Academy of Dental Therapeutics and Stomatology, Continuing Education Course, "Successful Intraoral Radiography