Thermoelectric Potentials in Metal Dental Fillings

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It is normally assumed that electrical potentials measured in metal dental fillings are the result of electrolytic action on the surfaces of the fillings by saliva in the mouth. However, a scientific paper published in 1952 describes experiments where electrical potentials were measured in amalgam dental fillings when they were not in contact with any saliva at all (Ref.1). The authors "explained" this result by presuming that "Since the teeth were dry the potential difference V1 (Fig. 3) was the e.m.f. (e) caused by the action of the bone fluid on the two fillings, i.e., e = V1." However, they made no attempt to identify positively that "bone fluid" acts electrolytically on the surfaces of amalgams, and they made no attempt to investigate whether or not the electrical potentials they measured could have been produced by some other physical process than an alectrolytic one (e.g. thermoelectric, electromagnetic). Is it possible that the authors' assumption that electrolytic action by bone fluid must be producing the measured potentials is simply the result of the common but entirely false belief that this kind of electrical potential can ONLY occur by means of electrolysis? Dental amalgams are inhomogeneous mixtures of dissimilar metals (Ref.2), and they are subjected to temperature gradients in the mouth all the time. According to the established scientific understanding of thermoelectric phenomena, when an amalgam filling is subjected to a temperature gradient across its thickness, thermoelectric eddy currents must flow around the inclusions of dissimilar metal held within the solid matrix of the material (And Professor L I Anatychuk of the Ukraine has written several papers describing how the electromagnetic effects produced by these eddy currents can be detected at the surfaces of inhomogeneous materials). Has anyone ever bothered to measure the thermoelectric behavior of amalgam dental fillings? And if not, why not? Keith P Walsh References: 1 2

By the way, a few years ago

By the way, a few years ago the organisation "Health Canada" issued the following statement via the website of the Canadian Dental Association with regard to the placement of metal amalgam dental fillings:

"It should be noted that Health Canada has taken the position that new amalgam fillings should not be placed in contact with existing metal devices in the mouth"

I wrote to the Canadian Dental Association regarding this statement with the following query:

"Is this recommendation intended to apply to metal alloy retaining pins screwed into the root sockets of a patient's tooth?"

And I received the following reply from Dr Philip Neufeld of Health Canada:

"Dear Mr. Walsh:

... it is unlikely that a metal retaining pin implanted into the tooth or the jaw bone would cause galvanic currents. In order for galvanic currents to be created, the pin would have to be in contact with an electrolyte such as saliva or extracellular fluids, and such retaining pins are usually not exposed. ...

Yours sincerely,

Philip Neufeld, Ph.D."

(you can read the complete reply at:

However, in their paper entitled "ELECTROMOTIVE FORCES AND ELECTRIC CURRENTS CAUSED BY METALLIC DENTAL FILLINGS" (Ref.1), William Schriever of the University of Oklahoma and Louis E. Diamond of the University School of Medicine, Oklahoma City, state the following:

"Since the teeth were dry the potential difference V1 (Fig. 3) was the e.m.f. (e) caused by the action of the bone fluid on the two fillings, i.e., e = V1."

Is there a degree of contradiction here?

And is it possible that both parties are failing to take into account significant effects of thermoelectric phenomena in metal fillings? (Remember that dental amalgams are inhomogeneous mixtures of dissimilar metals in their own right.)

Any opinions?

Does anyone know if anyone has ever bothered to actually measure thermoelectric phenomena in metal dental fillings?

Keith P Walsh


And also, would

And also, would thermoelectricians be so arrogant as to presume that the scientific way to deal with potentially embarrassing aspects of thermoelectric phenomena is to completelely ignore them?

Keith P Walsh

Dear ITS and ZTforum

Dear ITS and ZTforum readers,

Whenever I scan the literature for the latest developments in thermoelectric technologies I am always amazed and impressed by the range of advances which are being made in this particular area of physical science.

However, I am still not able to reconcile the fact that we should know so much about thermoelectric phenomena in general, and yet still know NOTHING AT ALL about the thermoelectric behavior of metallic dental restorations.

The kind of amalgams which are commonly used for filling cavities in teeth are inhomogeneous mixtures of dissimilar metals in their own right (ref.1).

Not only that, but it has also been common practice for dentists to screw metal alloy retaining pins into the root sockets of patients' teeth and encase the heads of the pins in amalgam, thereby creating yet further opportunity for thermoelectric effects to arise along the contours of the retaining pins.

Dental restorations of this type are placed in children's teeth.

And they are subjected to thermal gradients in the mouth all the time. (Ever heard of an "ice-cream headache"?).

It doesn't make any sense at all that experimental investigations to measure the thermoelectric performance of metallic dental restorations should never have been carried out.

And it makes even less sense when you realise that the whole of the dental profession appears to have been mis-led into believing that the only way that metal dental restorations are able to generate electrical potentials is by becoming involved in "galvanic activity" (i.e., "electrolysis").

It is a simple matter to demonstrate that from this position of ignorance the dental profession is now in some confusion as to exactly how the amalgam potentials arise. And again, it appears that many dentists have been misled into believing that such potentials can only be the result of electrolytic action by saliva in the mouth on the exposed surfaces of the fillings.

This is not true.

It was demonstrated as long ago as 1952 that the electrical potentials generated by amalgam dental fillings are present even when the fillings are not in contact with any saliva. But in the depths of their ignorance even the scientists who discovered this fact were only able to explain it by presuming (without looking for any corroborating physical evidence) that the "necessary" galvanic activity must in this instance have been caused by the electrolytic action of "bone fluid" UNDERNEATH the fillings (Ref.2).

When is an offical delegation from the community of thermoelectric science going to point out to the dental profession that it has been known for more than 170 years that metals, mixtures of metals, and dissimilar metals in contact with each other are able to generate electrical potentials as a result of their thermoelectric properties, and it is not necessary for there to be any electrolysis taking place in order for this to happen?

And that the materials used in restorative dentistry are not exempt from the laws of nature?

According to the established principles of scientific understanding, the only way to determine accurately the thermoelectric performance of a metallic dental restoration would be to measure it. (Remember Cronin, guesswork on its own does not constitute science, not even yours.) Does anyone know of any reason why it should not be possible to do this?

I believe that this question is important because, from our present position of ignorance, we cannot be certain that the dental profession might not be misled into believing that many common neurological disorders, as well as a myriad of so-called "psychiatric" disorders, have got nothing to do with the thermoelecric potentials generated by metallic dental restorations. Would anyone disagree?

Keith P Walsh