Waukesha, WI...July 15, 1994
Xrays ARE more difficult to read today than they were 20 years ago.
One of our course attendees from the Houston, TX area related this incident to me.
When he was a dental student at UT Houston eight or so years ago he accidentally dropped a set of xrays behind the panelling in the cubicle.
When the maintainance man retrieved them for him, he also found another set of xrays dated 1958.
To his amazement the 1958 xrays were far superior to his own.
His instructor could offer no explanation.
The explanation is simple but it is not comfortable.
Four major changes have occurred since the sixties that affect the quality of dental xrays.
First, when the price of silver began to skyrocket in the seventies, the manufacturers of all film, including medical and dental began to find ways to reduce the amount of silver in their film.
This results in a thinner coat of silver to turn black when exposed and developed.
The result is LOWER CONTRAST.
Second, practically every dental office today has some form of automatic processor.
These machines promise fast, dry-to-dry processing of film.
In order to do that, they use heat as a catalyst to speed up the chemical reaction between the silver and the developer.
In the photographic industry this is known as 'push-processing'.
When you push-process you gain density faster but LOSE CONTRAST.
Third, today we have faster film.
The dental equivalent of the ASA rating on photographic film is an alphabetical system, A,B,C,D,E,F, etc.
In the sixties the common film was "C" speed, the old Kodak Radiatized Film.
This was replaced with "D" speed film, Kodak Ultra-speed Film.
Each jump in letter speed doubles the speed of the film.
In ASA terms a jump from ASA 100 to ASA 200.
As the speed goes up, the CONTRAST DECREASES.
Today some dentists are using "E" speed film, Kodak Ektaspeed Film.
This is twice as fast as "D" speed and four times as fast as "C" speed.
Fourth, in addition to the movement to faster films there has been a trend, encouraged by state radiology departments, to increase the KVP on xray machines.
As you increase the KVP from 50 to 60 to 70 and then to 90 you gradually DECREASE THE CONTRAST.
Recently Eastman Kodak has come out with a new "E" speed film that has larger flatter crystals that are supposed to fix the problems they evidently had with the old "E" speed film.
Instead of widely spaced round crystals, it has overlapping flatter 'flagstone-like' crystals.
Since I have not yet tested this film (Thursday, January 15, 1998) against the "D" speed film,
I will have no comments until I do.
Some examples of the results:
He found 10 more cavities than you did."
Could be, he used lower KVP and slower film than you did.
Have you changed xray techniques or materials since those last xrays?
All of these are symptoms of the modern disease of radio-phobia that is reaching epidemic proportions as a result of the hysterical ravings in the popular media.
In the sixties it was not uncommon to use a 40 KVP xray machine, "C" speed film and exposure times of three, four or even five seconds.
In effect we were inadvertently running a large scale, long running, human experiment, exposing human subjects to what is today considered excessive doses of radiation.
I quote from Dr. Parker Mahan, who may or may not agree with me on this subject, "When, in theory, something should happen, and it does NOT, then the theory is wrong!"
If those doses of radiation thirty years ago were not safe, don't you suppose that we would be having an epidemic of cancers of the face, lips, tongue and salivary glands in the eightys and ninetys, thirty years later?
We have to be responsible practitioners.
We should use the minimal dosage of radiation that will do the job we need to do.
If the results of our radiographs are unusable, we are being irresponsible because the radiation was wasted and thus excessive.
We have a responsibility to know about radiation and to teach our patients about what is safe.
A radiologist being treated by a dentist friend of mine told him that the average chest xray is the equivalent of 325 dental films.
We all know that our xrays are safe.
It's time we let the public know.
If we sacrifice our own quality by pandering to these radio-phobes, we do ourselves, our patients and our profession a dis-service.
E-mail your comments to drjack@BetterEndo.com