Nagasaki was destroyed by a plutonium bomb.
MODERATOR COMMENT: Please note that this thread is from 2008, revived in Feb 2014 in post #7.
That’s OK, we don’t mind resurrecting old threads, but I just want readers to be aware of the antiquity. --CKDH
From the next-to-last paragraph:
“…Most dental porcelain sold today is uranium-free.”
Most? MOST? Who is still making these Faux Teeth of Death?
Actually, I’m wondering if Cecil might care to quantify the risks associated with a whole body dose that’s 8 times background radiation levels. I don’t expect it to be good, but I wonder if that’s even a blip compared to what airline pilots and flight crew get in the course of their jobs. IIRC the estimate I was given during my rad health physics training was that a cross continental flight gave about 10 mREM dose. Which is approximately the same dose that a person gets while standing around at sea level over the course of a month.
(Of course that exposure isn’t from radioactive isotopes, so it’s not covered by 10CFR20, IIRC…)
Maybe I’m being whooshed, but Cecil implies that the only advantage to having fluorescent teeth is that they glow under UV lights such as, say, in a disco.
Of course though, the sun radiates UV light, so fluorescent materials that absorb UV and emit visible light will look brighter and possibly whiter in sunlight. This principle is used in some washing powders; they leave a residue on your clothing that is invisible but fluorescent, so your clothing looks “whiter than white”.
Say normal yearly exposure is 500mREM/y… 8 times that is about 4REM/y. Usually you need several hundred REM in a short time period (i.e. acute dose) before you see anything that can be directly attributed to the radiation.
The concern is internal contamination, not radiation… and in all honesty, I’d worry about toxicity before radioactivity when it comes to uranium contamination.
I know that if you ask any of the nursing staff at your dentist’s office, they’re likely to reply that they don’t know. And if you ask your dentist, he’s got a pat reply that he’s repeated many times about how past stuff was bad, and current stuff is safe.
In 10 years, they’ll be talking about how the stuff they’re using today is bad, and the stuff they are using in 10 years is good.
“There is no other pill to take … so swallow the one that makes you ill” -Rage Against the Machine
I realize I’m coming rather late to the party, but …
As mentioned, natural sunlight has UV, which was the purpose of wanting fluorescence in dentures. It is also the purpose in adding fluorescent dye to laundry detergent - gets that “Whiter than white” effect.
The specific activity (measure of radioactivity per gram) for natural uranium is very, very low. (Depleted uranium is even less, since the more radioactive isotopes have been removed.) A curie of natural uranium is a cube as large as a room. And since very little was used, it was essentially a no-never-mind. :o
Like a number of other uses, it was discontinued due to concern and workable alternatives, not because of significant risk. Orange Fiestaware plates and Coleman lantern mantles were a much more significant concern. Similar amounts of it may still be used in glazes for porcelain fixtures, but those are near your butt, not in your mouth. 
The alleged death toll is a typical inflation created by use of assumptions and statistics; a key one is usually that every case of cancer in a denture wearer was caused by the uranium in their false teeth (See also: TMI, Chernobyl, Fukushima Daiichi for similar cases of letting a number off its leash).
The regulatory concept of linear effects with no threshold also contributes to this. This concept ignores the phenomenon of hormesis, which can be readily demonstrated for radiation, as well as other substances. This concept is that for many substances, while a lot is bad, a little is beneficial. (Too much vitamin A will kill you dead. Painfully. :eek: It happened to some Arctic explorers a while back.)
Summing up, uranium was and is used in consumer products, but was removed, and in most cases was not an actual health concern.
Some of the radium products, on the other hand …
I understand that radium was removed from watch dials not because it was a hazard to user, but because it was a hazard to the manufacturer.
Which is hard to totally object to, but it’s been 40 years since I had a watch that I could read in the morning darkness.
I wouldn’t go so far as to say DDT is good for peoples. But household use seems to be safe, as opposed to pouring huge amount all over our farmlands.
Brush 'em after every meal, because who knows what the dental industry will think up next?
— Cecil Adams
Isnt brushing your teeth right after eating harmful to your teeth, because of the acid attack in the mouth?
Sometimes it helps to have an every day comparison to get a grip on raw numbers.
Here’s a radiation chart from XKCD
Note that the chart is in seiverts. A seivert is roughly the result of 100 REM exposure.
The chart reports a normal day’s background dosage is 10µSv. So 8 times the daily dose would be 80µSv a day. That’s equivalent to living within 10 miles of Three Mile Island. And the health effects from that are recorded here. Read about midway down the article and you’ll discover the main effect from Three Mile Island, was stress.
Now return to the XKCD picture find Three mile Island up near the top on the right, and look at how little radiation that really is.
Yeah - the dial painters had the habit of using their mouths to put a nice point on the brush and got significant internal uptakes.
The watches (and compasses) had easily detectable radiation readings, but as you said, not a health risk. I have a couple of “sea stories” about antics ensuing from the emissions of radium dials in the “wrong place, wrong time.” 