| |
 |
|
|
Science Forum Index » Materials Forum » The Latest on Amalgams and Thermoelectrics
Page 5 of 5 Goto page Previous 1, 2, 3, 4, 5
|
| Author |
Message |
| Keith P Walsh |
 Posted: Sat Jan 12, 2008 10:52 am |
|
|
|
Guest
|
On Dec 17 2007, 1:56 pm, "D. C. Sessions" <d...@lumbercartel.com>
wrote:
Quote: In message <1c68bc3b-c836-4eb8-bf3d-fa5006...@w40g2000hsb.googlegroups.com>, Keith P Walsh wrote:
Do you know of any dental materials science textbook or published
scientific paper which quotes values of electrical resistivity for
typical dental amalgams in appropriate scientific units?
No, for the simple reason that it's trivial and not interesting.
There are, after all, an infinite number of possible material
combinations. Unless one has a particular reason that its
resistivity should be worth discussing, it's simply not worth the
bother to publish it.
I'm sorry D.C. but I don't buy this.
And I will explain why not.
In their book "Restorative Dental Materials", Robert G. Craig and John
M. Powers make the following assertion:
"The conductivity of materials used to replace tooth tissue is of
concern in restorative dentistry." (from Chapter 3, "Optical, Thermal
and Electrical Properties", page 55.)
Oddly this statement is not expanded upon in the book.
However, it clearly contradicts your own assertion with regard to the
resistivity of amalgams that, ".. it's trivial and not interesting."
(May I assume that you understand the relationship between electrical
conductivity and electrical resistivity?)
First you presumed that the reistivity of amalgams was "known" (a
presumption which, by the way, ought to be a reasonable one). Then
when you found out that it wasn't known you simply guessed that it's
not important.
And the statement by Craig and Powers quoted above contradicts your
guesswork so directly that I shall repeat it again with an emphasis of
my own added for effect:
"The conductivity of materials used to replace tooth tissue IS of
concern in restorative dentistry."
I think it is interesting enough to note that Craig and Powers quote
electrical resistivities for the following materials:
Human Enamel: 2.6-6.9x10^6 ohm.cm
- someone thought it was worth the bother to measure that and publish
the results.
Human Dentin: 1.1-5.2x10^4 ohm.cm
- someone thought it was worth the bother to measure that too.
Glass Ionomer Dental Cement: 0.8-2.5x10^4 ohm.cm
Zinc Oxide-Eugenol Dental Cement: 10^9-10^10 ohm.cm
Zinc Polyacrylate Dental Cement: 0.4-4.0x10^5 ohm.cm
Zinc Phosphate Dental Cement: 2.0x10^5 ohm.cm
You see, somebody took the bother to measure the electrical
resistivities of all of these dental materials, and to publish the
results.
And Messrs. Craig and Powers have also bothered to quote the values in
their book, presumably because, "The conductivity of materials used to
replace tooth tissue IS of concern in restorative dentistry."
(Go on then, I'll say it - electrical conductivity is the reciprocal
property of electrical resistivity.)
So tell me D.C., what's so special about dental amalgam such that it
should be the ONLY dental material whose electrical resistivity is not
worth bothering to know?
Back in 1950s someone agreed that it would be worth a masters degree
each to Richard J Schnell and Ralph W Phillips for them to bother
publishing the electrical resistivities of a range of dental amalgams.
The trouble is, as we have seen, their paper is useless because it
quotes all of the electrical resistivities in meaningless units, and
it doesn't specify the calculation used to derive the resistivities
from the measured resistances, see:
http://jdr.iadrjournals.org/cgi/reprint/43/4/501
And this paper is STILL the only document that anyone can find
anywhere in the world which purports to give electrical resistivities
(or electrical conductivities) of dental amalgams.
If I were the guessing kind I might guess that there's something
untoward about the electrical behavior of dental amalgam which is
indicated by the honest findings of experimental procedures to measure
it's electrical properties.
But then of course I would never presume that my guesswork was correct
until such findings had been verified scientifically.
Is that the main difference between my position and yours I wonder? If
it is then I should remind you that guesswork on its own never
constitutes science, not even your guesswork.
(And don't be misled by whoever it is who keeps following your
postings around giving them five-star ratings - the liklihood is that,
when it comes to the
electrical properties of dental amalgams, they're just as ignorant as
you are.)
Keith P Walsh |
|
|
| Back to top |
|
| Guest |
| Posted: Tue Jan 22, 2008 6:56 am |
|
|
|
|
<snip>
Quote: I can't help but find it ironic that Mr Walsh will quote Feynman stating how >a hypothesis can only be validated through experiment, and yet Mr
Walsh has never made any attempt to validate his own hypothesis by
running experiments himself...
Mr. Walsh
Why haven't you done any experiments? |
|
|
| Back to top |
|
| |
Page 5 of 5 Goto page Previous 1, 2, 3, 4, 5
All times are GMT - 5 Hours
The time now is Sat Aug 30, 2008 2:14 am
|
|