Possibly mercury from dental amalgum. Those "silver" fillings are approximately 50% mercury: http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/De

Possibly mercury from dental amalgum. Those "silver" fillings are approximately 50% mercury: http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DentalProducts/DentalAmalgam/ucm171094.htm http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedur... Generally inert in place and it has to be inhaled to be absorbed. However, drilling/removal/chipping can release absorbable particles. Edit: Also note -- because they are inert in place so advice from the FDA is to leave them be as long as the fillings are in good condition and there is no decay beneath the filling. In other words -- don't panic and take an ice pick to your perfectly good fillings.