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I recently heard this claim referred to on House M.D. when the titular character is experiencing phantom sounds, and the show appeared to give the idea some credibility. So I decided to look it up, but only found half hearted explanations or theories.

The question is three-fold:

  1. Can fillings (presumably on metallic fillings) "pick up" radio waves?
  2. If so, under what conditions can this occur?
  3. If so, can the radio waves be "interpreted" correctly or near enough to make the noise identifiable as a broadcast?
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I remember seeing this demonstrated many years ago on a television episode of Gilligan's Island. =D –  Randolf Richardson May 25 '11 at 19:53
Having built a crystal radio as a kid, I don't think it's all that doubtful. If there's an AM transmitter nearby, almost anything will pick it up. Add a diode of some kind, and there you are. –  Mike Dunlavey May 25 '11 at 20:51
In theory any metal can act as an antenna, but dental fillings are probably very bad ones. The demodulation is more tricky. Decoding FM (frequency modulation) should not be possible "by accident", AM (amplitude modulation) like Mike said, is more likely but I still don't think so. Experiencing some form of sound might be somehow possible, but personally I don't think that people can hear real messages. (I'm a M.Eng. for Communication Eng.) –  Martin Scharrer May 25 '11 at 23:08
@Martin: It doesn't need to be metal, just conductive, and I can suppose some fillings (maybe old-fashioned ones) could rectify. It doesn't have to be perfect. The field near an AM station can be pretty powerful. –  Mike Dunlavey May 26 '11 at 2:35

2 Answers 2

I've heard the story that at higher outputs (250,000 watts and up) than the traditional 50,000-watt "clear channel" stations, dental fillings became receivers. Here's someone who reports experiencing such an occurrence:

Your wifi, your cellphone, your Bluetooth, all have antennas buried in them. But at 800 or 1850 or 1900 or 2450 Mhz, their wavelengths are VERY short, a few cm of a metal strip against the plastic case under your hand. HF antennas at much lower frequencies must be longer, much longer. Here's a proper HF transmitting antenna: http://www.hawkins.pair.com/voanc/voanc14.jpg It's about 400M high for reference, but we can't fit it on the boat! It radiated to Europe for 50 years American propaganda, mostly for Russians. The transmitter was from 250,000 to 1,000,000 watts. I've been there when it was on the air. Your tooth fillings talk to you... (c;

Here's the antenna in question:

enter image description here

Maybe he's exaggerating, maybe not. Here's more testimony from the Geophysical Institute at the University of Alaska:

According to Robert Hunsucker, a professor emeritus at the Geophysical Institute with the University of Alaska Fairbanks, my phone isn't that complicated, and neither is a receiver circuit. A receiver is so simple, Hunsucker said, that anything from a phone to a person's mouth can act as one ... Hunsucker said the problem can sometimes be cured with a radio-frequency filter that can be attached to the phone line. He also said that if the radio signal is very strong, a filter might not be enough.

Such is the extremely rare case when a person's mouth acts as a receiver. The electrical conductivity of the human body can act as an antenna. A metallic filling in a tooth, reacting just so with saliva, can act as a semiconductor to detect the audio signal. The speaker in this case could be anything that vibrates within the mouth enough to produce noise, such as bridgework or maybe a loose filling. [Emphasis added.]

He says it's extremely rare, but he also describes how it could happen. Failure to reproduce the case by Mythbusters shouldn't hold any water in that case. A thing may be rare and difficult to reproduce, yet still happen.

Edit to add a further account from a seemingly credible source:

It's real. I attended a Field Day setup a few years ago, staged by the Westside Amateur Radio Club in Los Angeles. They had one of their stations inside a trailer, and the radio had an automatic antenna tuner. Well, SOMEBODY didn't ground the thing right. I was inside the shack about 5' from the radio when the op said, "Well, 15 meters is dead; let's tune it up on 20." He changed bands and hit the deadly little "Automatic Tune" button. The radio began buzzing as the tuner went to work. Also, I let out a scream as one of my teeth with a nice filling in it suddenly felt like a dentist was drilling in it with NO anesthetic! I RAN from that trailer uttering obscenities and the pain vanished as soon as I got clear of the thing. Needless to say I didn't hang around that particular shack much during the rest of the contest.

I am persuaded by the proximity argument. Since electromagnetic radiation diminishes proportional to the square of the distance, it is credible that running away would decrease the effect. If he was standing five feet away from the transmitter to start, ten feet would reduce the effect to 25%, 20 feet to 6.25%, etc.

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Snopes has an article regarding a story told by Lucille Ball of just such a thing happening to her personally. It's listed as 'undetermined' but does seem somewhat plausable.

The filling would basically need to function much like a Diode (possible due to dissimilar metals which can form a junction similar to a semiconductor), and the transmission would have to be AM (Amplitude Modulated), in which case the theory is that the filling would work much like a little crystal radio and the sound heard via bone conduction.

So has this ever has this ever actually have been documented to have happened? The folks at 'The Straight Dope' ferreted out two instances outside of LucyB, one of which sounds like this exact phenomina. Which would make it pretty darned rare (and might explain why the Mythbusters were unable to reproduce it)

Can it happen? well it seems we have at least two instances claimed, (outside of wacky tv sitcoms etc) so the answer would appear to be yes, but it is apparently extremely uncommon if so, so would be extremely difficult to replicate in lab conditions inside someone's mouth

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I'd say experiments designed to replicate that showed no effect trump claims by celebrities thus saying the answer would appear to be no in the nature of rational skepticism. –  The Real Bill May 26 '11 at 2:18
If the reported rate of the phenomena occurring naturally is one in millions, then it would point to it being very difficult to purposely construct a filling to replicate the effect. For example in one case a brass post was said to be involved, and if the experiment used only a standard amalgam filling constructed in standard methods, you would expect it to behave as the millions of 'normal' fillings, and not function as a diode due to an interface between dissimilar metals –  Chuck van der Linden May 26 '11 at 7:17
I don't recall the Mythbusters episode but there's a good reason they would have failed--to get a signal you must have a semiconductor involved and no semiconductors are used in dental work. The only way it could actually work is if you have something in there other than what the dentist installed--namely, corrosion. That takes time, something I very much doubt the Mythbusters applied enough of. –  Loren Pechtel yesterday
How do you know that the way it would function is like a diode? –  Oddthinking yesterday

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