Once a patient gets over the shock of being diagnosed with MS they then start looking for a possible cause. Patients often will find an article or hear a story about the relationship between MS and silver tooth fillings (amalgam). I have patients with MS that never had a filling or have the disease and lost all their teeth many years before they developed the disease.
After reviewing the American Dental Associations Evidence Based Dental site, http://ebd.ada.org/,and PubMed I located an article "Dental amalgam and multiple sclerosis: a systematic review and meta-analysis" by Aminzadeh and Etminan. They found a slight, non-statistically significant increase between amalgam use and risk of MS. The conclusion of the study was that future studies need to be performed taking into account the size of the silver filling, the surface area and duration of exposure.
As a conservative practitioner I cannot recommend prophylactic removal of amalgam fillings. When a silver filling fails, a tooth cracks or a cavity needs to be filled then a Resin Bonded Ceramic filing (white filling) is a reasonable option.