The following study published by the Scandinavian Journal of Dental Research in 1993 followed a group of 218 people with self-diagnosed oral galvanism. The researchers discovered that the symptoms experienced by all 218 patients could also be explained by several reasonable alternative diagnoses:

- Mental Disorder  in 42.7%.

- Additionally 40% were out of work due to medical reasons or unemployment.

Furthermore, the study also looked into whether some effect of mercury "leeching" was occurring, but found that the blood mercury levels in all of the patients were well below the accepted threshold of 50 nmol/l.

Scand J Dent Res. 1993 Aug;101(4):232-7

The United States Department of Health and Human Services also published a report in January 1993 on the use of dental amalgam fillings and concluded that recommending the removal/replacement of amalgam fillings was unwarranted.

http://web.health.gov/environment/amalgam1/ct.htm