Answer to Question #11055 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Dental

The following question was answered by an expert in the appropriate field:

Q

I'm 38 years old and am trying to get an idea of my approximate radiation dose from x rays performed 30 years ago. Can you tell me how dental x-ray dosage compares from 1980 to today (traditional film). I know this varies depending on speed, operators, etc., so an approximation is fine. I understand that digital x rays today are much lower dosages too.

A

I wish there were an easy answer to this question; but, unfortunately the majority of dental offices establish their office radiology protocols based on what the dentist learned in school, and then continue that practice indefinitely. For instance, as the chart below from an article published by Farman & Farman in 2000 shows, D-speed film was introduced to the dental community in 1955 and most dental offices that are still using film are still using D-speed film even though F-speed film is readily available and results in one half the radiation dose to the patient. It is simply a matter of ordering a different film and film processing chemicals from the dental supplier. Yes, some dentists claim that the image looks slightly different, but multiple scientific articles prove that dentists using F-speed film can diagnose dental cavities and periodontal disease (gum disease) and other dental problems just as accurately as with D-speed film. Professional organizations recommend that dentists use the faster F-speed film and several states have regulations stating that dentists should use the fastest film possible; however, enforcement is spotty. One other change in technique can greatly reduce radiation dose for intraoral imaging; and, that is rectangular collimation. The limiting factor for adoption of this technology is that it takes extra time to learn and while the staff is learning the technique, there are “retakes,” or bad, nondiagnostic x rays that need to be reexposed; however, after this brief learning curve, patients see an approximate 50 percent decrease in radiation dose.

The following table is a short synopsis of some selected radiation doses, adapted from the work of Dr. John Ludlow, a professor and international authority on oral and maxillofacial radiation safety at the University of North Carolina School of Dentistry: (see notes below)

Examination Dose µSv Background equivalency
Panoramic (average) 16 2 days
FMX (Digital or F-speed film round collimation) 171 21 days
FMX (Digital or F-speed film rectangular collimation) 35 4.3 days
FMX (D speed film round collimation 388 47 days
4 BWs (Digital or F-speed round collimation) 38 4 days
4 BWs (Digital or F-speed rectangular collimation 5 17 hours
Notes:
1) The panoramic dose has not changed significantly over the years whether a dentist is using film or a digital technique due to the use of intensifying screens in film systems.
2) Background equivalency is based on an average daily dose of ionizing radiation of 8 µSv per day per person; the panoramic example would be the dose of 16 µSv divided by 8 µSv to yield two days.

In summary, the actual radiation dose for an individual patient from 1980 to 2014 may have changed very little, depending on the radiographic practices of the dental office in which the patient has been seeking care. On the other hand, if the practice has upgraded its radiographic facilities, the radiation doses may have improved by a factor of 50 percent, if a more efficient receptor such as F-speed film or a digital technique is being used. And, if rectangular collimation for intraoral imaging (bitewings and periapicals) has been introduced, a further reduction of another ~50 percent in radiation dose for intraoral imaging has been achieved. Industry-wide, approximately 60 percent of dentists are now using digital receptors for intraoral imaging, but the majority of the remaining 40 percent still use D-speed film.

Jeffery B. Price, DDS, MS
Associate Professor and Director of Oral and Maxillofacial Radiology

Reference

  • Farman TT, Farman AG. Evaluation of a new F speed dental x-ray film. The effect of processing solutions and a comparison with D and E speed films. Dentomaxillofacial Radiology 29:41–5; 2000.
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