See my first post on this thread.
Abrasion of the natural tooth structures and restorations like crowns and fillings gradually changes the way the teeth interact with the jaw joints and the muscles. And, of course, the joints slowly change their shape too. Even dental repair measures may contribute to this very slow loss of the correct way of masticatory function. It's an utterly complicated process. I guess 1000 pages would not suffice to cover the basics.
Usually the affected person does not even realize that something is wrong, because the changes took years, very often even decades to occur. You don't perceive a change of one thousandth of a millimeter per month, but it adds up.
The result is a whole host of symptoms, among them facial pain, muscle tension, inability to concentrate, ear noise, headache, dizziness, neck pain, constant tiredness, bad sleep, you name it. In other words: It's the same list as all the symptoms amalgam is blamed for.
The funny thing is, those symptoms occur at exactly the same rate in persons that never had amalgam fillings. A Swedish study in the early 1990s even showed that the none-amalgam group had slightly more of those symptoms than the amalgam group.
Now, as I mentioned above, when a dentist removes all amalgam fillings and carefully replaces them (please note the word, "carefully!), the natural consequence is a huge improvement of the function, because all that wear and tear, a.k.a abrasion, attrition and few other fancy terms, get's removed too. The natural balance between the teeth and the other structures of the masticatory system gets reinstalled, and the patient feels much better, and that even apart from placebo effect.
So far, so good, but in most cases the same effect can also be achieved without removing any amalgam fillings, just by correcting the way the upper and lower teeth interact with one another and with the joints and muscles. That is normally done by milling / grinding tiny amounts of hard material (natural and / or articial) where it interferes with the harmonic paths of movement while biting or chewing on food.
Equally important is the correction of areas that provoke so called occlusal parafunctions, which means exertion of force on the teeth and joints that have nothing to do with normal function, such as bruxism (gnashing of teeth -- very frequent, and most of the patients have no idea they are doing it!), excessive pressure of the tongue, lips or cheeks on the teeth and many other "bad habits" that normally go unnoticed.
I've seen patients that had suffered of daily headache or other ailments for decades, had visited dozens of doctors to no avail and had no idea that such occlusal interferences were the most likely reason of their suffering. Some of them needed fairly long and careful examination and planning, while others actually can be read like a book at first glance.
The treatment proper usually is simple, consisting, as said above, of minute corrections. Sometimes twenty minutes suffice to remove the interferences, sometimes substantially more work is needed, but it is far less invasive than removal of any fillings. The success rate, however, is exactly the same.