Thermoelectric Eddy Currents in Metal Dental Fillings

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The article entitled "Basics of Thermoelectric Effect with Magnetic Readout", by Johann H. Hinken and Yury Tavrin, shows a schematic diagram of the thermoelectric eddy current and associated electromagnetic field which are produced whenever a thermal gradient is maintained across an element* of one electrically conductive material which is completely enclosed within another dissimilar conductor. See: http://www.hs-magdeburg.de/fachbereiche/f-iwid/ET/Personen/Hinken/forsch... (Figure d is particularly instructive.) The metal amalgams used for filling cavities in teeth comprise a great many elements* of one particular electrically conductive material (unreacted dental alloy) which are all enclosed within a matrix of a dissimilar electrically conductive material (dental alloy mixed in solution with mercury). See: http://www.bookbootusers.co.uk/setting.htm If we can assume that the materials used in restorative dentistry are not exempt from the laws of nature, then we should expect that when a temperature gradient is established across a piece of this material thermoelectric eddy currents and their associated local electromagnetic disturbances will be induced around each of the elements* of "unreacted alloy". The material should "come alive" with thermoelectric eddy currents. Does anyone know of any experiment which might be employed in order to try and detect this thermoelectric activity inside the material from a position just outside its surface? And does anyone know if the electromagnetic effect produced by the eddy currents would be strong enough to have an influence on neurological tissue in the vicinity of a metal dental filling in someone's mouth? Keith P Walsh * in this context I am using the word "element" to mean "piece", and not in the sense of the term "chemical element".

Academic Correspondence I

Academic Correspondence

I have some academic correspondence concerning this topic (see below).

If professor Wang offers any further reply I shall append it later.

Best regards,

Keith P Walsh
*******************************************************

Dear Professor Wang,

I am indebted to Dr Pan for forwarding my initial enquiry to you.

I appreciate that your answer may be valid for metals with a high degree of material homogeneity. However I would be grateful if you could consider this matter again, taking into particular account the degree of material inhomogeneity which is present in dental amalgams.

In its final form an amalgam dental restoration has a high degree of material inhomogeneity, as illustrated by the two diagrams attached.

In a material of this nature it should be expected that the application of a temperature gradient will induce thermoelectric eddy currents to circulate around each of the inclusions of "unreacted alloy" (Y).

The local electromagnetic effect arising from the application of such a thermal gradient in this type of material is therefore not simply dependent upon the coupling parameter defined for any single (i.e. homogeneous) metal, but must also take into account the influence of the eddy currents induced in the material as a result of its inhomogeneity.

I would like to emphasise this point by further asking you to consider the findings of Hinken and Tavrin in their paper "Basics of the Thermoelectric Effect with Magnetic Readout" which can be seen at:

http://www.hs-magdeburg.de/fachbereiche/f-iwid/ET/Personen/Hinken/forsch...

Figure 1d shows the thermoelectric eddy current and associated electromagnetic effect produced when a temperature gradient is maintained across a conductor which has an inclusion of a dissimilar conductive material inside it.

If there was no such inclusion, the theoretical electromagnetic field produced by the thermal gradient acting on the homogeneous material alone would be too weak to detect at the surface of the material - because the "coupling parameter" for the homogeneous material would not be significant enough.

I believe that it is the condition analogous to this one that you have considered when giving your answer to my enquiry.

However, when there IS an inclusion of a dissimilar metal within the larger piece, the temperature gradient then has the effect of inducing an electric current to circulate within the material. This current continues to circulate for as long as the temperature gradient is maintained, and it in turn induces a much more significant local electromagnetic effect which IS detectable at the surface of the material.

Dental amalgam may be described as a great many elements of one electrically conductive material all enclosed within a matrix of another, dissimilar, electrically conductive material.

Would you agree that the electromagnetic effects induced by the application of a temperature gradient across a typical dental amalgam should be more significant than those induced in most other metals, and that this would be as a direct result of the greater material homogeneity of the dental amalgam?

And do you know of any experimental procedure which may be employed to determine whether or not it is possible to detect the local electromagnetic effects induced by thermal gradients in dental amalgams?

Fig.1 Schematic representation of the microstructure of a lathe-cut alloy-based amalgam - from "Introduction to Dental Materials", Richard van Noort, Mosby, 1994, ISBN 0 7234 1963 9

Fig.2 electron probe photograph provided by Professor David B Mahler of The Oregon Health & Science University School of Dentistry, showing the microstructure of a set dental amalgam against a scale of 15 microns

Best regards,

Keith P Walsh

3 Pittengardner Farm Cottages
Fordoun
Laurencekirk
Aberdeenshire
AB30 1SB

Tel: 01561 320869
Mobile: 07777 679340

e-mail: keith.p.walsh@btinternet.com

----- Forwarded Message ----
From: "Pan,Ernian"
To: Keith Walsh
Cc: "Wang,Xu" ; "ernian_pan@yahoo.com"
Sent: Monday, 15 December, 2008 8:35:46 PM
Subject: RE: Thermoelectric Behavior of Metal Dental Fillings

Keith,

Thanks for sharing the interesting topic with us! I shared your email with my colleagues Prof. Xu Wang, and attached below is his comments.

Happy Holidays!

Best, Ernie

--------------------

Theoretically electromagnetic field will be generated by thermal gradient. But the thermoelectric coupling parameter in most metals is very low (0.001-0.01). So I don't think the induced electromagnetic field is significant enough to influence the neurological tissue nearby.

----------------------

Ernie Pan, Ph.D.
Professor of Civil Engineering
Professor of Applied Mathematics
The University of Akron
330-972-6739 (O); 330-972-6020 (F)
pan2@uakron.edu
www.civil.uakron.edu/~pan

From: Keith Walsh [mailto:keith.p.walsh@btinternet.com]
Sent: Sunday, December 14, 2008 12:36 PM
To: Pan,Ernian
Subject: Thermoelectric Behavior of Metal Dental Fillings

Dear Dr Pan,

I am a private researcher and I am trying to prove that the electrical potentials generated by metal amalgam dental fillings are not able to dissipate electrical energy through the nerves in people's heads.

As part of this work I feel obliged to take into account the possible thermoelectric behavior of materials used in metal dental fillings.

And as you may be aware, dental amalgams are inhomogeneous mixtures of dissimilar metals. You can see a schematic diagram of a 2-dimensional cross-section of a typical dental amalgam at:

http://book.boot.users.btopenworld.com/setting.htm

If a metal dental filling made of this material were subjected to a thermal gradient, would you expect thermoelectric eddy currents to circulate within the material?

And, if so, would you expect to be able to determine whether or not the resulting local electromagnetic fields have any physical influence on neurological tissue nearby?

Yours faithfully,

Keith Walsh

3 Pittengardner Farm Cottages
Fordoun
Laurencekirk
Aberdeenshire
AB30 1SB

Tel: 01561 320869
Mobile: 07777 679340

e-mail: keith.p.walsh@btinternet.com