Where does all of this mercury go? Into your body. Absorption of mercury from the area under your tongue and the insides of your cheeks are the fastest absorption. These areas, of course, are in close proximity to the mercury fillings, so efficiency of absorption is great. From these tissues, the mercury can destroy adjacent tissues, or travel to the lymphatic drainage system and directly into the blood stream. From the blood stream, mercury can travel to any cell in the body, where it can either disable or destroy the tissues. Mercury can also travel directly from the fillings into the lungs, into the blood stream and, as before described, every cell in the body becomes a valid target.
Mercury and its compounds are adept at traveling through the "lipid soluble" cells membranes. Cell membranes contain roughly 60% protein and 40% fat. Nerve cells are an exception, containing nearly 75% fat. These fat-rich membranes determine what enters the cell and what does not. Methyl mercury is oxidized into the "ionic" form of mercury. This is a very destructive form of mercury. (Its problem is that it cannot travel very far.) Methyl mercury is the most dangerous form due to its ability to travel great distances and enter all cells. After the trip, methyl mercury is converted into ionic form. The ionic form is what actually disrupts internal structures and metabolic pathways that keep a cell alive and producing proteins, enzymes, hormones, whatever, that are the purpose of the existence of the cell.
All of this travel and destruction is what defines mercury toxicity. It may favor nerve tissue for a destruction target, but the kidney is high up on its list of tissues to destroy. After these two areas, it can wreak havoc in any tissue that might get in its way. For this reason, it is difficult to devise a change in the normal chemistry of the body, called a test, which would "prove" mercury toxicity. It can alter almost anything in the body; therefore, mercury should not be allowed to enter for any reason.
Three times now, amalgam has been accused of initiating diseases. The first time was in the 1830's, again in the 1920's, and the third time a movement started in 1973 in which more substantial information has been available to determine the toxicity of the substance. Up until recently, it was felt that the mercury stayed within the filling. Now it is known that mercury leaches out every minute of the day. The average amalgam filling releases about 34 (plus-minus 2) micrograms of mercury daily.
Mercury changes forms. It has different costumes. It ducks into phone booths as organic, and comes out as inorganic, and then darts into a dark cell to do its damage leaving someone else's fingerprints. Mystery. It did take scientists a long time to determine how mercury changes faces so fast. Each form attacks a different aspect of the cell membrane, or your DNA or your enzymes.
Mercury atoms can attach to any cell in the body rendering it abnormal, and subject to destruction by the immune system. This condition is collectively referred to as "auto immune disease".