Alloy and amalgam dis-integration question

I am aware that brass screws in a marine environment will de-zinc leaving a weak pinkish 'ghost' of the original brass - presumably a porous
form of copper. I could well believe that the density of this remnant material may be half the original density of the brass.
Could the same marked density reduction either due to galvanic action or vaporisation occur to the mercury component of dental amalgam ? Since starting the thread on sci.med.dentistry copied below I did a bit more exploration. I suspected that filing the filling material may have smeared/disguised any porosity. I had another smaller piece from the same filling and placed in the jaws of some end-snips inside a polythene bag and sheared into two pieces. This showed light-grey , powdery surfaces which when lightly filed showed the silvery colour as before. Viewing under 30x magnification, the grey surfaces, then probably a porous granular material with random tiny black patches, presumably of silver oxide.
s.m.d thread repeated here Allowable level of mercury ingestion ?
Twice in one week I've read media articles about mercury / amalgam fillings. Plenty of anecdotes but nothing quantitive.
I've an odd bit of filling that dropped out six months ago and decided to do a back-of-envelope calculation. Filling now decidedly black on surface but filing a flat shows silvery metal and no apparent porosity under x30 microscope. Weight 0.58 gm +-0.01gm Volume 0.12cc +-0.02cc from displaced water in a 2mL hypodermic syringe barrel.
so Old filling density 0.58/0.12 = 4.8gm/cc
Amalgam filling composition 52% Hg, and 48% of Zn,Cu and Ag densities : 13.6,6.9,8.8,10.5 not knowing composition in more detail have taken average of Zn,Cu and Ag so new Amalgam density of 11.3
Loss over say 20 years (assumed, so a big unknown , somewhere between 2 years and 40 years ) =(11.3 - 4.8 ) * (0.58 / 4.8 ) * 0.52 = 0.41 assuming all metals are lost equally, unlikely but I've no info to quantify better. 0.41 gm over 20 years so 20 mg per year
If only mercury is totally lost, and in the limit, only leaving the other metals intact then a figure of 30mg per year of ingested mercury
No allowance for direct wear, off the filling surface, also ingested. And only one such filling considered.
What is the allowable figure for yearly ingestion of Mercury ?
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Snip
First, let us note that Paul is a NUT (notorious usenet troll) with over 800 usenet posts in the last year alone. This un-necessary cross post was well answered already by the dentists on sci.med.dentistry. The infinite monkeys pounding at typewriters occasionally spit out some Shakespeare.
The general term for the form of corrosion including dezincification is dealloying. Dealloying is possible for some amalgam fillings. See the first hit (a recent PubMed abstract) in a google search under dealloying and amalgam:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids 731616&doptstract
Also, see http://www.mse.cornell.edu/courses/engri119/Class_Notes/amalgam_technical.html Pittsburgh Pete -----------------------
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