The Smile Daily

According to Dr. Timothy Johnston:

Prior to modern x-ray technology (pre1960's), there was indeed a good deal of scatter radiation that went all around the head and neck. This was due to the type of machine used to produce the radiation.This was called a point-source x-ray machine. It produces all the radiation at the very tip of the machine, and so radiation just went everywhere. That's why the technician always stepped out of the room, and why patients wore lead aprons. The amount of radiation was also quite high due to the inefficiencies of the x-ray film.

The first big improvement on all this was the "culminated" x-ray head. The point of radiation production (the point source) got moved to the back of the machine, then a leaded tube (the column) only let radiation out through the end of the tube. There is still some spread... but only a small degree. Think of the old point source like a stick of dynamite: it explodes and goes in every direction. The culminated version is more like a shotgun. There is still an explosion in the gun, but everything is directed down the barrel, with just a little spread once it leaves the end of the barrel.It was at this point that the risk of radiation spreading to the rest of the body really diminished. So much so, that many European countries don't even mandate the use of lead aprons in dental offices anymore. To prove this point to my staff several years ago, I taped paperclips to x-ray films, and stuck them all over the lead apron: in the neck area, chest, tummy, & lap. If any scatter radiation hit them, we would have seen an image of the paperclip on the film after processing them. We put that apron on a patient, and took the normal "full mouth series" of 18 x-rays. We then developed all the paperclip films, and found absolutely nothing on them.The next improvement came in the sensitivity of the film itself. By improving the sensitivity, the film required less radiation to produce the same quality image. When I graduated dental school in 1989, the industry standard was "D" speed film. "Ecta" speed had just come out, and required even less radiation. Then came "F" speed, cutting the radiation in about half.The next big thing was digital x-rays. The term "digital x-ray" is really a misnomer. The x-ray, or radiation, hasn't changed (other than using less of it), It's the sensor that is digital. By putting computer sensors in your mouth instead of x-ray sensitive film, we have been able to turn down the amount of radiation being delivered to 1/4 (yes, one-fourth) of what it was with D speed film. We switched over to digital x-ray sensors in my practice in 2003.Statistics to prove the point further:

• Dental x-ray rooms only need the normal sheetrock on the walls to meet code for x-ray blockage (and that was for D speed film)
• Standing 6 feet away, with no barrier, also yields no exposure risk.
• One GI series in the hospital will give you more radiation than an entire life-time of dental x-rays.
• Traveling on an airplane across the country gives you the equivalent radiation exposure of 4 bitewing x-rays.
• Just being alive in the US exposes you to the equivalent exposure of 360 dental x-rays EVERY YEAR. (Natural background radiation)
• It would take 5,000 dental x-rays (again... with D speed film, so more like 20,000 films using digital) to get to the maximum safe YEARLY occupational exposure, as determined by the government.
• My lead aprons, at this point, are superfluous. Totally unnecessary. But I don't want to take the time to explain all of the above to each and every patient... so we keep using them. The "flip-up" cervical collar Dr. Oz mentions isn't even on my aprons. They got in the way of taking lower jaw x-rays, so we ordered aprons without them 20 years ago.

Hope that clears things up... according to Dr. Tim!