[ RadSafe ] FDA encouraging dental professionals to switch to faster X-ray film

[John Jacobus]

>From the Food and Drug Administraion's Web site

http://www.fda.gov/cdrh/radhlth/dentalradio.html
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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
milli-Gray (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.


REFERENCES

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”

Updated April 27, 2005

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"Embarrassed, obscure and feeble sentences are generally, if not always, the result of embarrassed, obscure and feeble thought."
Hugh Blair, 1783

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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