This is what I found on a mercury website...
Do not even dream of putting a drill inside the mouth until the immune and liver detoxification systems are optimized. Patients have mineral imbalances due to diet and poor absorption. Just to give an example, we give magnesium in four different forms. We want magnesium to go to the outside and the inside of the cell wall, we want it inside the mitochondria which are the energy producers of the cell. The same applies to other minerals. from....
http://www.positivehealth.com/permit/Articles/Dentist/hall43.htmELIMINATING MERCURY
In order to remove mercury the body must have several systems in good working order.
1. BOWELS AND KIDNEYS are the main avenues of excretion for mercury. So the bowels and kidneys must be able to eliminate regularly and correctly.
2. LIVER FUNCTION: The liver is the main filtering system in the body. As mercury leaves the tissues and circulates through the blood and lymph system it will find its way to the liver to be sent out of the body.
3. ADRENAL AND THYROID FUNCTION: These glands are responsible for pumping mercury out of our tissues and sending it to the liver. Once in the liver they signal the liver to dump it out of the body.
NUTRIENTS THAT REMOVE MERCURY!
The trace element "SELENIUM" prevents mercury absorption from the intestinal tract. Other trace elements like zinc, iron, manganese, molybdenum, and vanadium help to stop mercury from absorbing into our cells and bump it out after it has settled in.
Sulfur compounds such as garlic, raw onions, slow cooked beans and eggs all aid the liver in the elimination and mobilization of mercury.
Intravenous chelation may be required if mercury levels are particularly high . This is a procedure where an I.V. is inserted into the patient. A chemical is then released into the blood that will bind with the mercury and carry it out.
I have found that this procedure removes good minerals as well as the bad ones. It can cause side effects by causing deficiencies of the good minerals. Most practitioners include supplements of the good minerals in the I.V. as an attempt to replace those minerals which may be lost. My experience has been that this is still inadequate. Therefore, I do not recommend the I.V. procedure unless it is an extreme and dangerous situation."
Here are a couple of sites for more info...
http://www.websitetoolbox.com/tool/post/kiddredd/vpost?id=1226519&highlight=prerequisites http://www.positivehealth.com/permit/Articles/Dentist/hall43.htm 
