dental gold?

I had a tooth extracted today. It had been crowned with gold. They gave me back the gold crown, tooth still in it of course.
I seem to recall hearing that Coca-Cola actually dissolves teeth. Is that a workable solution to removing the old tooth from the gold crown? Is there a better one?
Grant
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wrote:

The coke doesn't work. I am in the same boat, and it barely touched the tooth (if at all) before it went moldy.
Still looking for a good approach...
Doug White
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On Tue, 05 Aug 2008 22:28:14 GMT, snipped-for-privacy@alum.mit.edu (Doug White) wrote:

Dilute HCl, .1 N dissolves Hydroxyapatite. In the absence of nitrate, this will not dissolve the gold, though it may extract alloying metals such as copper from the surface, leaving a frosty surface. You can speed this up in a beaker floating in an ultrasonic cleaner. This cavitates the organic materials as well as speeding up the dissolution of the HA.
Coke will not work because it is a very dilute solution of phosphoric acid, which gave rise to stories about it removing rust from bumpers.
HA can be prepared from H3PO4 and CaOH2 .
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(Doug White)

EDTA might work. Dissolves egg shells readily.
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"Grant Erwin" wrote: (clip) I seem to recall hearing that Coca-Cola actually dissolves teeth. Is that

^^^^^^^^^^^^^^^^^^ It must be pretty slow--else most of the population would be toothless. I suggest tap-tap-tap with a small hammer. Or leave the tooth in, and have a jeweler add a small ring, so you can wear it on a chain around your neck. :-)
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Grant Erwin wrote:

Try heat. I think the glue would fail before the gold would melt. RR
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in message

Try a stronger acid. The Phosphoric and Citric acids in Coke are weak and slow.
Maybe HCL/Muriatic? Might even try a little battery electrolyte --that's Sulfuric.
Don't try a mix of Nitric and Sulfuric:-)
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BillM wrote:

Or Nitric and Hydrochloric = Aqua Regia. :-) ...lew...
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in message

My bad. For some reason I had it in my head that Aqua Regia was nitric/sulfuric.
Bill.
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Grant Erwin writes:

No.
Melt it out with a propane torch. Improvise a casting crucible by grinding and compressing bentonite clay (hidden in the grocery store disguised as the cheapest unscented store-brand kitty litter). Or from silicate furnace cement.
Gold dealers will give you about half the bullion value of the gold scrap. They're in it for a profit. Likely no more than $50 or $100 cash for an old crown, so it may not even be worth the trouble. But you could play with the jewelry style of metalworking, say casting and finishing a finger ring.
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Hammer.
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Tom Gardner wrote:

That's kind of what I am thinking. I'll try that tomorrow, let you know what happened.
Grant
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On Wed, 06 Aug 2008 05:44:26 GMT, Grant Erwin

A propane torch will just burn out the tooth from the gold. ERS
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wrote:

Beware mercury fumes. The gold in crowns may be or contain mercury-gold amalgam, not just gold-copper casting alloy.
Joe Gwinn
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why not tap with a hammer and break up the tooth - the gold is maleable and the tooth is not
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Joseph Gwinn wrote:

Gold crowns are not made from amalgams. Gold amalgams are used for fillings. Silver amalgam fillings are always removed before a tooth is crowned.
The reason that an amalgam filled tooth gets a crown in the first place, is mostly, that there is new decay around or even under the filling, so the tooth has to be cleaned and the amalgam is removed to make place for either an inlay, overlay or a full crown. You cannot prep a tooth properly for a crown, with the amalgam still in place.
It not necessary to put a torch to a tooth with a crown still on it. Since the tooth has already been extracted, it will have become brittle rather rapidly, because it is no longer fed by blood vessels and nerves. Just take a pair of pliers to it, and it'll break in pieces quite easily.
BTW, before I became a goldsmith, I spent three years in dental school at the university of Amsterdam trying to become a dentist.
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Abrasha wrote:

I put the crown, tooth in it, in a bench vise, minor closure, CRACK, all the tooth pieces fell out. Took about 3 seconds flat.
Now I have 2.7 grams of gold crown and another couple grams of whatever alloy they use under ceramic. Oh, the bench vise cracked off about 95% of the ceramic too, on that one.
Grant
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I don't doubt that you have described how it is supposed to be. But the world isn't perfect, and there is no cost to being a little cautious while heating the gold alloy. It might be contaminated if the dentist didn't get all the amalgam out.
Joe Gwinn
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Joseph Gwinn wrote:

This is almost impossible. However, in the unlikely event, that this was the case, the work was done by an exceptionally bad dentist.
Getting old silver amalgam fillings out, is quite easy, since the moment they are touched with a drill, they pretty much crumble and get ripped out. The pieces fly in all directions (inside the mouth of course), because of the characteristics of the material once it has been in a tooth for some time.
It is also very likely, that if in fact there was still some silver amalgam left under the crown, the patient would have developed new decay and with it quite a severe toothache. The crown would have failed, have to be removed, the tooth would have to be cleaned again, and a new crown would have to be made and placed.
Also, if he did choose to heat it, the cement with which the crown is affixed to the tooth would decompose long before the gold would melt.
And lastly, even if there were a silver amalgam filling under the crown, heating it would most likely be harmless. It is unlikely that he is going to get hurt from "Mercury vapors" from a single silver amalgam filling.
A mouthful of silver amalgam fillings is a lot more dangerous to a person's sustained health, than heating one that is no longer in a mouth.
http://zakstar.wordpress.com/2008/01/29/silvermercury-amalgam-fillings /
Before the advent of electroplating, precious metal smiths used the extremely poisonous technique of "fire gilding" to gold plate silver objects. This was done with gold amalgams.
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Well, it's far too late for me.

I had not heard of this technique. If it was before electroplating, it was back when an old man was 45, so they probably didn't manage to die of the mercury fumes.
I recall reading that the ancients knew how to electroplate, although they didn't understand how or why it worked.
Joe Gwinn
Joe Gwinn
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