 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Medical Forum / General / Dentistry / August 2005Hardening Mechanism of Dental Amalgam
Anybody know the reason why dental amalgams harden from paste? Is it similar to the mercury evaporation process for gold purification? Its only a wild guess but is something similar happening - sufficient mercury evaporation via body heat causing the semi-solid solution to solidify? That is wrt to a phase diagram, % Hg composition is dropped (not neccesarily to 0%) thereby putting the metal solution into a total solid phase? No, I'm not interested in the environmental/health impact of dental amalgams - just the chemistry/thermo of hardening. On 8/6/05 10:40 PM, in article c9hJe.335$546.323@newssvr23.news.prodigy.net, > Anybody know the reason why dental amalgams harden from paste? Is it > similar to the mercury evaporation process for gold purification? Its only [quoted text clipped - 5 lines] > No, I'm not interested in the environmental/health impact of dental > amalgams - just the chemistry/thermo of hardening. It is not a vaporization process. It is probably the metal filings getting dissolved in the mercury turning into a solid solution. This is one of those topics that should be well understood. You did google--didn't you? Bill > Anybody know the reason why dental amalgams harden from paste? Is it > similar to the mercury evaporation process for gold purification? Its only [quoted text clipped - 5 lines] > No, I'm not interested in the environmental/health impact of dental > amalgams - just the chemistry/thermo of hardening. IIRC it's some sort of phase change of the alloy, especially brought on by pressure - as the dentist pushes it in.  Signature-- Ron Jones Don't repeat history, see unreported near misses in chemical lab/plant at http://www.crhf.org.uk Only two things are certain: The universe and human stupidity; and I'm not certain about the universe. ~ Albert Einstein >> Anybody know the reason why dental amalgams harden from paste? Is it >> similar to the mercury evaporation process for gold purification? Its [quoted text clipped - 8 lines] > IIRC it's some sort of phase change of the alloy, especially brought on by > pressure - as the dentist pushes it in. http://www.mse.cornell.edu/courses/engri119/Class_Notes/amalgam_technical.html > > IIRC it's some sort of phase change of the alloy, especially brought on by > > pressure - as the dentist pushes it in. [quoted text clipped - 9 lines] > > http://www.mse.cornell.edu/courses/engri119/Class_Notes/amalgam_technical.html Looks like a pretty good link. too bad the quality of amalgam is under so much control of the individual dentists. the article says that after 3 minutes amalgam should be discarded. What would happen if it wasn't discarded? I assume it is still usable since the article says "should be" discarded. Clinton, There have been huge changes in the formulation of amalgam over the years. Today it sets so very fast! Years ago it contained loads of liquid mercury and the dentist condensed (or expressed out) the excess mercury. There were squeeze cloths that were used to express excess mercury. Today, no. Joel clintonz@prodigy.net Wrote: > > > IIRC it's some sort of phase change of the alloy, especially > brought on by [quoted text clipped - 19 lines] > discarded. What would happen if it wasn't discarded? I assume > it is still usable since the article says "should be" discarded. SignatureJoel344 > Clinton, > [quoted text clipped - 7 lines] > > Joel It says however, after the amalgam is mixed. So you are saying that if an amalgam made from a capsule is left setting for 3 minutes that is no problem? >>Clinton, >> [quoted text clipped - 11 lines] > saying that if an amalgam made from a capsule is left > setting for 3 minutes that is no problem? After 3 minutes the mix is unusable. You throw it out--no problem. Steve SignatureCut the nonsense to reply >> > IIRC it's some sort of phase change of the alloy, especially brought on >> > by [quoted text clipped - 13 lines] > Looks like a pretty good link. too bad the quality of amalgam > is under so much control of the individual dentists. Not really. In the "old days" that was true: " In the bad old days triturition (=mixing) was by mortar and pestle; to make working the mix easier, excess mercury was added, then squeezed out of the mix using linen cloths. Then we had mechanical triturators but accurate measurement of small quantities of mercury was not easy. Now all amalgam is sold in pre-packaged ampules containing alloy powder and mercury, kept apart with a plastic seal. The seal is broken and the mixing is done without opening the ampule. " > the article says that after 3 minutes amalgam should be > discarded. What would happen if it wasn't discarded? It would lose the toothpaste-like consistency and you wouldn't be able to condense into the tooth. It just crumbles while condensing, and you have to start over. >I assume > it is still usable since the article says "should be" discarded. It's not usable. It'd be like trying to take partially set concrete and spreading it out evenly for a side walk. It just wouldn't work. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.