Resistivity of amalgams still a mystery



What would make you think there is any coorelation between resistivity and release of mercury?
I mean other than your general obsession with mercury.
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Jim Pennino

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snipped-for-privacy@specsol.spam.sux.com wrote:

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)
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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.
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Jim Pennino

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snipped-for-privacy@specsol.spam.sux.com wrote:

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.
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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?
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Jim Pennino

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snipped-for-privacy@specsol.spam.sux.com wrote:

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.
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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?
<snip nonsense>
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snipped-for-privacy@specsol.spam.sux.com wrote:

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 4.
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 ?)
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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?
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Jim Pennino

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snipped-for-privacy@specsol.spam.sux.com wrote:

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?
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<snip crap>

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.
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Jim Pennino

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snipped-for-privacy@specsol.spam.sux.com wrote:

that "crap" is the direct answer to you question. Is that also crap?

I think you are confusing me with Keith who has shown an interest in measuring the resistance. I would just like to know the theoretical derivation of the resistance and how it relates (theoretically) to the vapor release. I am not nor did I ever profess a particular interest in measuring the resistance of an amalgam for its own purpose or using the resistance data to derive Hg loss rates.

I have a pretty good idea of how to measure resistance.

I believe Keith started the thread and is interested in using the resistance as part of a calcualtion of electromagnetic properties of an amalgam. His final goal is to determine how much EM energy is given off by an amalgam.

I never said it was.
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There is no theoretical derivation of resistance of materials.
It is a measured property.
<snip rest>
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snipped-for-privacy@specsol.spam.sux.com wrote:

Certainly you can attempt to theoretically estimate the conductivity of materials. I don't know how successfull those attempts have been with amalgam. However I do agree that resistance is a measureable property. By definition V=RI, R=V/I and the current and voltage across any material are obviously real, meaurable quantities for any material, including amalgam.
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I have a rope.
Attempt to theoretically estimate how long it is.

And the universe trembles at the astounding insight.

FYI, measuring the resistance of something with a resistance in the sub-Ohm range requires some attention to detail to have any meaning.
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Jim Pennino

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[...]

Does the term "undistributed middle" mean anything to you?
--
Richard Herring

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Richard Herring wrote:

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.
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(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.
--
Richard Herring

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Richard Herring wrote:

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?
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Simplicio wrote:

I suspect a resistivity measurement is not as simple as it appears. The topology of the amalgam micro structure, impurities, grain boundaries, individual grain composition would all effect the the measured resistivity. The applied voltage may also cause ion migration in the solid that would effect resistivity with time. Performing a full blown impedance measurements and then the appropriate circuit analysis (not an easy task) may provide some clues to the amalgam stability, but it would need to be correlated with measured compositional changes. Other issues such as crystallographic defects induced by pressure (chewing) may also effect the resistivity (and impedance) of the amalgam.
Gregg
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