I said that understanding the material properties
of an amalgam such as conductivity, resistance etc is important to a
understanding of Hg release from an amalgam. I did not say that
in the resistance of an amalgam ( or two different amalgams)
necessarily means the leakage of large amounts of Hg. Are you saying
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
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
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,
major form is as a vapor. You probably would admit that the leakage
an equation as a function of time. But you've said above that the
changes as a function of time (age). Therefore you've proved that
can be written as a function of vapor pressure (or release rate of Hg
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
rate of Hg can spike and for how long.
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
By the way does the resistance "stabilize" no matter what the
of Hg is at the surface (I.E no matter how the amalgam is mixed or
what other material it is placed next to ?)
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?
And what "evidence" is that. The data show that amalgam loses a
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
show the resistance unchanging for 30 years? Do they show the
as a function of all possible mixtures?
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
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.
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
of the resistance and how it relates (theoretically) to the vapor
I am not nor did I ever profess a particular interest in measuring the
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
as part of a calcualtion of electromagnetic properties of an
His final goal is to determine how much EM energy is given off by an
Certainly you can attempt to theoretically estimate the conductivity
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,
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
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
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.
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? it's a scientific fact. And I also stated numerous
time that I was only talking about the relationship, not the
the measurement which is a subjective conclusion anyway, since the
"usefullness" of any measuremnt is an opinion. That's your own
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
that the magnitude of the realtionship could be masked by other
in an experiment is irrelevant. However, if you took enough
and controlled the composition of the amalgams sure you could measure
the change in resistance AND vaporiztion as a function of time with
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.
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)
in an ideal amalgam.
your the one who doesn't know the meaning of science or rhetoric.
apparently your till too confused to comprehend that both the
and vaporiztion rate of an amalgam are functions of time, not
Did you pass algerbra AND chemistry?
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
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
Other issues such as crystallographic defects induced by pressure
(chewing) may also effect the resistivity (and impedance) of the amalgam.
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