Resistivity of amalgams still a mystery

That's funny.

Some years ago under the newsgroup thread "Dental Amalgam and the Absorption of Electromagnetic Energy", professor Harvey Rutt, the Deputy Director of the School of Electronics & Computer Science at the University of Southampton in the UK told me:

"About the only relevant property is the resistivity."

Would you suggest that Professor Rutt was mistaken?

Also, until recently the website of electronic equipment manufacturer Gore Electronics used to make the following assertion regarding the electromagnetic properties of materials*:

"If you can describe the permittivity, permeability and conductivity of a material, you can describe completely how electromagnetic energy behaves within that material."

I'm sure I don't need to explain to you the relationship between conductivity and resistivity. However I am beginning to wonder if you yourself understand this subject as well as you might.

Keith P Walsh

• If I were the "conspiracy theory" type I might wonder if Gore Electronics had been persuaded to remove this statement from its website by someone not purporting to represent the interests of the dental profession.

When you put it in the context of tiny bits of metal in a mouth, no, because the likelyhood of any RF effects, unless you stick your head in a microwave oven, where permittivity and permeability become important are somewhere between nil and not at all.

But that just ignores the biggest part of you lunacy.

First you have to establish as fact that very low level electricity in the mouth is harmfull in some way and then determine the harmfull level.

If and when you do that, then you can ask the question is an amalam filling capable of generating a harmfull level.

Of course, you are totally ignoring all the other metal things that are used in dentistry, but that's only because you are obsessed.

So I disagree with Prof. Rutt (except that the teeny bit of energy dissipated in the amalgam would depend on resistivity although the other factors would affect the delivery of the energy). Note: Gore electronics mentions permittivity and permeability before resistivity. Possibly the statement was pulled because it was considered a trite truism.

My previous comments hold.

Dammit, see what a mistake the University of Illinois made in giving me a PhD in Electrical Engineering! Possibly I know enough to know my limits. Do you?

mercury sure ain't bubble gum, and amalgams release a lot of merucury. Since resistance IS derived from the basic material properties of amalgam it iS ultimately relevant to understanding the toxicity of amalgam.

What would make you think there is any coorelation between resistivity and release of mercury?

I mean other than your general obsession with mercury.

What would make you think there isn't? (Please don't cite personal experience since the personal experiences of a jerk aren't something I am eager to read about)

You are the one making the rather bizarre claim that the resistivity of amalgam somehow correlates to mercury leaching.

The burden of proof that any such correlation exists is on you.

I said that understanding the material properties of an amalgam such as conductivity, resistance etc is important to a theoretical understanding of Hg release from an amalgam. I did not say that changes in the resistance of an amalgam ( or two different amalgams) necessarily means the leakage of large amounts of Hg. Are you saying that changes in the resistance of an amalgam cannot result from Hg leakage?

So your contention is that no matter how much Hg is lost from an amalgam no change in resistivity anywhere on the amalgam will occur.

The resistivity of any amalgam, which would include dental amalgam, is going to depend upon the materials in it and several other factors including, but not limited to, age of the amalgam.

OK, so what?

The typical resistivity of dental amalgam is known and has been measured.

What are you going to do with that set of numbers?

What has that set of numbers to do with mercury leaching?

At this point you probably would admit that amalgam leaches mercury, one major form is as a vapor. You probably would admit that the leakage follows an equation as a function of time. But you've said above that the resistivity changes as a function of time (age). Therefore you've proved that resistance can be written as a function of vapor pressure (or release rate of Hg vapor). That's what a resistance measurment has to do with mercury leaching.

What am I going to do with that quantitative relationship? I'm going to try to understand the theoretical derivation of it and apply it to non-ideal, or non-typical conditions which would exist in practice, although I'm not really interested in the resistance # as much as the concentrations and chemical bonds formed in the remaing material because I want to know if the release rate of Hg can spike and for how long.

No, I haven't proved that.

Further, the resistance of an amalgam stabilizes in a period measured in days.

So now what are you going to do with the resistivity numbers?

Ok, so if I measure the resistance on day 4 and then take another measurement 30 years later after the amalgam has lost a large % of Hg I'll get the same number since the resistance has "stabilized" on day

2. By the way does the resistance "stabilize" no matter what the concentraton of Hg is at the surface (I.E no matter how the amalgam is mixed or what other material it is placed next to ?)

In message , Simplicio writes

Does the term "undistributed middle" mean anything to you?

What leads you to believe that an amalgam loses a "large %" of Hg after 30 years when the empirical evidence says they don't?

That is, if they did, they would start to crumble and this doesn't appear to happen.

Since you are talking about dental amalgam, the how and what of the mixture has defined limits.

The resistance curves are out there.

What other material are you sticking in your mouth?

Answer the question. Can the resistance be written as a function of time....I'll help Yes. Can the change in emission of vapor be written as a function of time Yes. Can the change in (total) resistance be expressed as the change in rate of vaporization?

U see as the amalgam ages and Hg is released the resistance changes. As the concentration of Hg changes so does the rate of diffusion to the surface. In fact phase changes also occur which contribute to changes in resistance and release of Hg

You might not like the fact that BECAUSE amalgams lose so MUCH mercury the resistance can be expressed as a functon of time as well as the magnitude of the release of Hg in vapor form and therefore they can be expressed in terms of each other, but U know what? Just because the ADA didn't "tell U to think it yet" doesn't mean it isn't true.

And what "evidence" is that. The data show that amalgam loses a significant amount of Hg over time. It has to, because so much Hg is coming off as a vapor.

Even the dentists such as Joel Eichen admit that amalgam can loses up to 30% of it's Hg without changing it's structure. Try looking at photos of the grain structure. Next You'll tell me that if amalgam lost Hg it would "shrink", which many dentists on the group were arguing for quite a while.

Really? what is the limit on the concentration of Hg which can be left at the surface of an amalgam? 60%? 90%?

In other words can't or won't directly answer the question. Do these curves show the resistance unchanging for 30 years? Do they show the resistance as a function of all possible mixtures?

In message , Simplicio writes

(I'll take that as a "no".)

What question?

Your rhetoric appears to be an attempt to prove that resistivity is a useful measure of Hg release rate. You'll need to ask and answer a lot more questions to get to that point. Here are a few suggestions:

Is the time-dependent change in either of these quantities significantly greater than the variation across samples? Or the variation associated with phase changes? Is the function connecting them even monotonic?

And they are all best answered by presenting empirical evidence, not rhetoric.

"U" appear to be confusing me with somebody else.

Rhetoric? it's a scientific fact. And I also stated numerous time that I was only talking about the relationship, not the "usefulness" of the measurement which is a subjective conclusion anyway, since the "usefullness" of any measuremnt is an opinion. That's your own ridiculous conclusion

The point is that the VAPORIZTION RATE IS A FUNCTION of time. SO IS THE CHANGE IN THE RESISTANCE. That is as "simple" as it gets.

I'm talking about a theoretical relationship NOT an experiment. The fact that the magnitude of the realtionship could be masked by other factors in an experiment is irrelevant. However, if you took enough measurments and controlled the composition of the amalgams sure you could measure the change in resistance AND vaporiztion as a function of time with statistical certaintiy, BECA:USE THEY ARE a function of time.

THE PHASE CHANGE would contribute to the change in the RESISTANCE and Vaporiztion rate as a function of time. It's not independant.

zzzzzzzzzzzzzzzzzzzzzzz The function, would probably be something like R=Ke(-t) and vaporiztion rate = H e(-t). Now solve for R as a function of (total) vaporiztion rate in an ideal amalgam.

zzzzzzzzzzzzzzzzzzzzzzzzzz your the one who doesn't know the meaning of science or rhetoric. apparently your till too confused to comprehend that both the resistance and vaporiztion rate of an amalgam are functions of time, not constants. Did you pass algerbra AND chemistry?

What does it matter and what would you do with resistivity?

Are you going to compare it to some random sample of some random age of some random mix and get some random number?

You do realize that you only get to do this once since resistivity is a geometric property and to measure the resistivity of an existing filling means you have to remove it and reshape it into a known geometry?

So, what would you do with resistivity if you had charts of resistivity for all the mixes and all the ages of all the fillings put in over the last 150 years?

And no more nonsense about mercury leaching. There are real methods to detect mercury leaching and the resistivity of an existing filling isn't one of them.