Hello everybody:
Here is what I heard about amalgam from "my" dentist.
He said that amalgam leeches out most of its mercury during the first few months, with the highest rate of this process taking place during the first few weeks.
After that there is relatively little mercury left at the periphery of a filling. So if your amalgam fillings are old, then, according to him, it makes sense to wait till that filling would need replacement.
I heard that when 60 Minutes broke that story, there was a mad rush to replace amalgams and dentists made lots of money out of that.
But the vast majority of those replacements were probably unnecessary.

Again, those are his words, I am not an expert in this.
He said that in some cases amalgam is pretty much the only option. The material, which is used by white fillings is not tolerated well by dentin and apparently the problem is serious enough to necessitate the use of a liner, a special material which is placed between dentin and white filling.

If a cavity is large, after preparing it, there may be a very thin layer of dentin left between the filling and the pulp chamber. In that case even a liner may be of no use, as a white filling could degrade dentin sufficiently to cause serious problems.

Amalgam does not have this problem, according to what he said.

Amalgam is also more suitable as material for cervical fillings, from structural point of view. White cervical fillings pop out with a much greater frequency than amalgam.

One could probably say that this dentist is just trying to obscure the issue.
I, obviously, can only guess about that, but his comments were made in reference to the question of REPLACING existing amalgam fillings. With just one exception, I was always insisting on white fillings when doing restorations with him.

In my opinion he is an honest dentist. For example, he takes care to save a tooth even when the cavity is so deep that he can see a pulp chamber "shining through" the remaining dentin after he finished preparing a cavity.
He advises his patient about the situation and tells him that white filling for this case would not be suitable. If he insists on white, then he may well have a complication some time later, which can become a real emergency.

As a contrast, some dentists would not trouble themselves trying to save such teeth, they simply drill the remaining millimeter or two of dentin right into the pulp chamber and make you pay for hte root canal.

The reason many folks are not aware about this shady reality of running a dental practice is probably because "their" dentists are not in the habit of advising them about the course of the treatment.
Pretty much all you would hear is "Please bear with me, I'll do my best!"

Pardon for a harsh claim, but the reality of running a dental practice is such that drilling right "through" the marginal cases brings in much more money.
If you came to fill a pretty large cavity, a dentist may well break into a pulp chamber without even bothering to tell youi anything. This way he gets money for the root canal and a crown ($1000-$1200 total, possibly $1500 and even more for the more complex root canals).
Legally he is not obligated to tell you anything!

But trying to save a cavity, which extends 1-2 millimiters to the pulp chamber is simply too much trouble!
It is, of course, possible, but why bother? What is his gain? To be able to charge you at the higher end of a fee spread for that type of a restoration?

Root canal alone would bring in at least twice as much! Plus a dead tooth has to be crowned, and you see the picture!
And in the existing legal environment you simply cannot prove anything!

Let's also not forget that every time a cavity is filled, it has to be prepared.
It is very unfortunate, but some dentists do not take sufficient care, when preparing cavities. Some use an oversized bore for a small cavity, or the same bore when preparing two cavities (large and small).

This way he can make it faster, but you would be losing more of your healthy dental tissue than "necessary".
And it is a fact of life that some folks begin wearing partial dentures already in their mid-fifties. Some even earlier!

This was just an illustration that the dentist from whom I was buying treatment over the last several years seems to be an honest one.
I am sure he would not mind to make some money by jumping at an opportunity to replace a few amalgam fillings, but he advised me not to do it, since those are many years old.
Since I found out about amalgam toxicity, I was telling dentists to put a white one. Only on a couple of occasions I had to agree to amalgam because of the condition of those teeth.

It is not my intention to start arguing about the toxicityof mercury. I am very much aware what kind of a poison it is!

Personally I did not feel any perceptible problems from amalgam fillings, maybe because I did not have to replace them often.
I have several amalgam fillings, which are at least 15 years old. I am not sure white fillings would last this long.

However, I am an active runner, I run year round, I did 17 marathons, plus a great many shorter races, and, quite naturally, that means sweating a lot.

I would imagine that helps to detoxify my body.
I have also been taking MSM for quite a few years already.
Among other things, MSM increases permeability of cellular membranes, thus making it easier for cells to dispose of waste products and toxins. They are dumped into the interstitial space and taken through the lymphatic system into the blood stream and, hopefully, out.
You can read about MSM on http://www.whyCrave.com/msm.htm

And here is a list of other sources of mercury: fungicides, bactericides in antifouling paints and mildew-proofing preparations. Used in coal mining, textile mills, timber product processing, petroleum refining, rubber processing, paint and ink formulation. Also used in thermometers, barometers and various industrial pressure and rate-of-flow indicators.
All closed sports arenas have a big problem with mold, since people there breathe and sweat a lot. Closed-roof swimming pools are also in need of antifouling paints and mildew-proofing preparations.
Once I signed up for an indoor track, thinking that it would help me with my running during winter, but withdrew after the first workout. the air was unbearable, too much mold and it also smelled of smth like pesticide.
I would rather be running in cold weather, but outside!
best regards: Oleg