Metal taste in mouth despite filling removal!

Hi all,
I had my 4 Amalgam fillings removed 4-5 years ago. However, I still sometimes get a metal taste in my mouth, sometimes like my 2 back bottom teeth are secreting a metal substance!!! It usually happens when I'm detoxing, like at the moment, it's pretty bad.
How can this be? Could it just be mercury being excreted from my tissues or the dentist didn't remove all the mercury?
She followed the right protocol, oxygen mask etc. NB it didn't seem to make any obvious difference to my health at the (I have CFS). I've never done any proper chelation.
Thanks for any comments :)
Anne