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About 15 years ago I read an obscure government publication on the use of uranium in dental porcelain. It said uranium is added to dental porcelain for cosmetic reasons, to make the porcelain more luminous like natural teeth. It was estimated that this use of uranium causes about 2,000 cases of cancer per year. I've since mentioned this to many dentists, but none of them had ever heard of this.

Cecil, I'm counting on you to find out what's going on here. Preferably before I need more dental work. And while you're at it, what is the safest dental material?

--Pearl E. White, Chicago

You read right, friend--an accomplishment in itself these days. In one of those classic wacky moves, manufacturers once upon a time did put uranium in dental porcelain to give crowns and false teeth that certain glow.

Real teeth have natural fluorescence. If you shine a black light on your teeth they gleam a brilliant white. To give dental work the same glow, the use of uranium in dental porcelain was patented in 1942.

The timing of this was suspicious. You have to wonder if those Manhattan Project scientists, toiling over crucibles of hot uranium, got to thinking, hey, if this atom-bomb thing flops we can always go into teeth.

I should point out that the glow imparted to false teeth by uranium was not in itself a consequence of radioactivity. Uranium merely happens to fluoresce in the presence of UV light. Fluorescence is harmless. Lots of compounds do it. Uranium's advantage was that it would survive the high heat of porcelain manufacture.

However, you did have the problem that uranium also was radioactive. In the wake of Hiroshima and Nagasaki it occurred to the dental-ceramics industry that a substance that had destroyed cities might have adverse health effects if used in the mouth. Manufacturers discussed the situation with the Atomic Energy Commission in the 1950s.

The debate proceeded along the following lines. On the one hand, putting uranium in people's mouths might possibly give them cancer and kill them. On the other hand, their teeth looked great. It was an easy call. The industry was given a federal exemption to continue using uranium.

In the 1970s some began to wonder if this had been the world's smartest decision. The amount of uranium used in dental porcelain was small--0.05 percent by weight in the U.S., 0.1 percent in Germany. Nonetheless the fake teeth bombarded the oral mucosa with radiation that was maybe eight times higher than normal background radiation. None of the research I came across mentioned a specific number of cancer deaths, but clearly this was not something you'd do for the health benefits.

There was also the unavoidable fact that the aesthetic gains achieved using uranium were slight. To see the teeth fluoresce you needed UV light, and as one study sniffily noted, "UV lamps are used mainly in some discotheques and restaurants" frequented by "only a very small fraction of the population with these types of restorations."

But come on, you're thinking. If even one guy with fake teeth looked good in a disco, the prospective untimely demise of a whole bunch of other people was surely worth it.

Even that advantage turned out to be illusory, however. Though it was claimed that the best uranium compounds replicated the white fluorescence of natural teeth, research showed that some porcelain teeth fluoresced red, violet, or bright yellow. In other words, not only were you nuking your gums, but when you opened your mouth you looked like a freaking neon sign.

That put the matter over the top. Numerous authorities urged that the use of uranium in dental porcelain be discontinued, and in the mid-1980s the federal exemption was revoked. Most dental porcelain sold today is uranium-free.

What's the safest dental material? One guess: real teeth. Guaranteed against silent horrors unless someone sneaks up and bites you. Brush 'em after every meal, because who knows what the dental industry will think up next?

Is there something you need to get straight? Cecil Adams can deliver the Straight Dope on any topic. Write Cecil Adams at the Chicago Reader, 11 E. Illinois, Chicago 60611; E-mail him at cecil@chireader.com; or visit the Straight Dope area at America Online, keyword: Straight Dope.

Art accompanying story in printed newspaper (not available in this archive): Illustration by Slug Signorino.

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