Dental amalgams, whether gold or silver, contain mercury, one of the most toxic metals to our body. Having amalgam fillings, is like having a constant supply of toxic mercury, released slowly but constantly.
Removal and replacement of amalgam fillings instantly removes the source of mercury supply, however the mechanical removal process itself (drilling) can temporarily increase the concentration of mercury in your body.
When you decide to replace amalgams, make sure that you are already on the detoxification program and that you tell your dentist to apply a lot of suction during the removal process, reducing the concentration of mercury vapours.
Note, that it may take a considerable amount of time for your body to neutralise and excrete the mercury that has accumulated in your body over many years.