Magnetic Susceptibility of Dental Amalgams

This is correct. I tried it once but I got a call from her lawyer .........

Chew on some tin foil. :-)

Well for a start this statement is factually incorrect.

The Penguin Dictionary of Physics gives the following description of the "Kelvin (or Thomson effects)" under the general heading "Thermoelectric Effects"

""A potential difference is developed between different parts of a single conductor if there is a temperature difference between them; for a temperature difference dT between two points, the e.m.f. in this element is udT (u = greek letter mu) where u is the Thomson coefficient."

So you were wrong about that.

What complicates matters further in the case of dental amalgam is that dental amalgam is not in fact a "homogeneous metallic substance".

Dental amalgam is an inhomogeneous mixture of dissimilar metals. See:

And one might expect the thermoelectric behavior of this material to differ from that of a homogeneous metallic substance accordingly.

You can get an idea of the kind of thermoelectric processes occuring when an inhomogeneous material is subjected to a temperature gradient at:

Apparently, not only does the temperature gradient induce thermoelectric eddy currents in the material giving rise to the localised electromagnetic effects shown, but the reverse effect whereby an applied electromagnetic field gives rise to induced eddy currents and associated temperature gradients is also possible.

Dental amalgams are subjected to thermal gradients all the time.

And amalgam fillings are placed in children's teeth.

I believe that the thermoelectroic properties of dental amalgams should therefore have been measured.

And I am confident that I am right.

Amalgam is an inhomogeneous mixture of dissimilar metals.

Not necessarily.

It has 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 providing further opportunity for thermoelectric effects to occur at the interface between the amalgam and the alloy.

I believe that the only scientific way to determine whether or not these effects are significant is to measure them.

And again I am confident that I am right.

Keith P Walsh

PS, enquiries concerning the electrical properties of dental amalgams can be found at:

Keith P Walsh

First of all the letters are talking about deal with a galvanic reaction not a thermoelectric effect which you are describing. These are 2 different things. I gave you my comment of the Galvanic reaction earlier. As far as your thermoelectric effect, that requires a thermal gradient meaning one end of the amalgam filling must be heated and the other end cooled at the same time. In the mouth that can never happen even if the patient eats ice cream after drinking hot coffee. The gradient needs to be applied at the same time. You are just trying to confuse the issue by bringing in different effects of electromagnetics. Amalgam is a homogenous mixture of several metals.

Where's the temperature difference in the amalgam? None? Oh well, you're wrong again. Why don't you figure out mu for an amalgam and then see what kind of dT you would need for it to fry a person's neurons. This is electromagnetics, and we need to see equations and hard numbers, not haphazardly used definitions which have no applicability.

Temperature gradient is ubiquitous in Nature.

Dental amalgams are subjected to temperature gradients all the time.

The latest thermoelectric wristwatch batteries are able to generate voltages of up to 1.5 volts from a temperature gradient of only 1K. See:

Nevertheless, levels of temperature gradient much greater than 1K are commonplace in the human mouth.

Material properties are not "figured out".

They are measured.

I would expect any electrical potential arisng in a single homogeneous metallic material due to its Thomson coefficient to be "small".

What makes the situation more complicated in the case of dental amalgam is that dental amalgam is not a single homogeneous material, it is an inhomogeneous mixture of dissimilar metals. See:

The electrical potentials, currents and energy dissipations involved in human neurological processes are also "small". (But not too small to be measured.)

What is not in doubt here is that it has been demonstrated experimentally that amalgam dental fillings generate electrical potentials with magnitudes of up to 350 millivolts. See:

With regard to the first question, dentists confidently tell us that newly placed amalgam fillings quickly acquire a layer of metal oxide on their exposed surfaces as the result of a small degree of electrolytic corrosion, and that this layer adheres permanently to the surface thereby preventing further electrolysis from taking place.

(I have no reason to doubt that this is the case.)

So for an answer it might be necessary to consider other phenomena by which electrical potentials are induced in metallic materials. And two which come to mind are thermoelectric phenomena and electromagnetic phenomena (which we know are linked with each other).

Unfortunately (and some might suggest inexplicably) it appears that neither the dental profession nor any other organisation in the world knows anything at all about the thermoelectric or electromagnetic properties of dental amalgams.

I wonder if this might be due in some part to the answer to the second question.

(Remember, if it can be shown that thermoelectric and electromagnetic phenomena are between them not able to generate electrical potentials as large as 350 millivolts in dental amalgams, then this does not necessarily mean that this figure is false. It would simply make it necessary for us to conclude that we still DO NOT understand where it comes from.)

Keith P Walsh

PS, This thread started with an enquiry about the magnetic susceptibility of dental amalgams.

In view of the fact that dental amalgam is an inhomogeneous mixture of dissimilar metals, would you expect the magnetic susceptibility of the material to vary from point to point within the material?

And, if so, would you expect to be able to establish scientifically that it is not possible to measure this variation without ever having bothered to try?

When Bates, Baker and Meakin of the University of Nottingham in the UK wished to investigate the magnetic susceptibility of a NON-homogeneous material they chose to use "amalgams of metals in dilute solution in mercury".

Are you saying that they made the wrong choice?

Keith P Walsh

PS, the abstract from the resulting paper reads:

"A description is given of a new apparatus and technique for the examination of the magnetic susceptibility of a non-homogeneous material, with particular reference to the investigation of amalgams of metals in dilute solution in mercury. An important feature of the apparatus is that the electromagnet has one pole tip with a cylindrical surface and one pole tip with a plane face, so that when an amalgam is placed in a vertical tube suspended from a torsion balance, each portion of the amalgam is exposed to the same value of the gradient of H2 in the direction along which motion of the tube is possible; consequently, measurements can be made with amalgams which separate on standing."

- and the whole thing can be purchased via;

REPLY

Keith must be right. My mouth lights up from 350 millivolts of electricity every time I chew on my amalgams.

REPLY

I agree. Its fun to eat Baked Alaska and try to get a piece with both the ice cream and the carmelized sauce .........

Generally, a single element of thermoelectric devices generates a voltage of 200 microvolts by a temperature difference of 1 C. To *** ########## obtain 1.5 volts by a temperature difference of 1 C, it is necessary to connect at least 7500 elements in series. It was obvious that *********************** extraordinary difficulties would follow in machining the elements and ensuring their reliability.

Now, how about 7500 amalgam fillings in one mouth, to produce 1,5 Volts... ?

Regards,

Aribert Deckers

I think you've misconstrued the analogy.

If a single amalgam filling were analogous to a single wristwatch battery, then the individual grains of unreacted alloy in the filling (coupled with the binding matrix of reacted metal surrounding them) would be analogous to the individual thermoelements in the battery.

Do you think that it should be possible to demonstrate experimentally that the thermoelectric voltages generated by amalgam fillings are negligible?

Keith P Walsh

of course not, you can never prove a negative. no matter how good your test setup someone else may find a different condition where it is true. what is lacking in this 'discussion' is any significant correlation between amalgam fillings and the effects you are looking for. be it due to thermoelectric effects, galvanic action, or magnetic induction, voltage is voltage. there are lots of metals used in dental work, and plenty of chances to have ill effects. why don't you start by finding cases where ill effects have been directly caused by amalgam fillings rather than posing open ended questions in group2 that is not really interested in your speculations.

the original title of this thread was about the magnetic susceptibility of amalgams, this has no relation to the current discussion. the susceptibility would only matter if you were worried about a big magnet pulling the fillings out of your teeth, it has nothing to do with induced voltages in the fillings.( unless maybe you wrap some coils of wire around the fillings and use them as a transformer core)

i recommend you go chew on a piece of aluminum foil for a while and see if it changes your personality for the better.

I know ,,, I hooked up my new watch to four amalgams and it works just great.

Joel

You CAN prove a negative if your name is Jan Drew and if you post in sci.med.dentistry ......... at least she thinks she can!

Joel

i don't read dentistry groups. i see this stuff in sci.physics.electromag where it is getting rather repetitive... probably time to mark his threads to ignore and be done with it.

Think small. The 7500 elements fit in a watch battery so they can't be very large*. Maybe equal to the silver droplets in the mercury homogenate (in an amalgam). Some watch batteries are small enough to fit in a molar..

Do you believe Timex should be legally obligated to inform people that no controlled studies have been published demonstrating that these potentials are not able to dissipate electrical energy through the nerves in people's heads? And what about the poor souls that carry a pocket watch? Think of the potential consequences!

carabelli

I do not read sci.med.dentistry either although I do post there. Reading is far more cumbersome than posting.

Joel

You need to post some hard numbers, not some "philosphy of science" stuff about ubiquity of temperature gradient. By "figure out" I thought I was clear in suggesting that you put the equations down on paper and determine the value of mu based on an amalgam model. This shouldn't be hard to derive at all. I believe you will find based on a properly calculated mu that the dT will be in the hundreds if not thousands in order to provide even 1 mV of change in potential.

You continue to post generalizations and scattered quotations from all over the place. Please prove your point by doing at least a little simple math.