Silver fillings are actually made up of a silver amalgam with silver-tin alloy, copper and mercury. Silver fillings have been being used for over 100 years. There have been many studies on the mercury in these silver fillings. It is true that mercury is released when chewing and grinding, but it has been found that the amount of mercury that is released from 5 fillings is the equivalent of a tuna fish sandwich. Silver fillings last longer than composite fillings, and they cost less. Over time, silver fillings will corrode which may allow decay under the filling. Also, these fillings slowly expand and may cause tooth fracture, and the need for a bigger filling or crown.
Composite fillings are made up of a resin and inorganic materials. These fillings are natural looking, they often make the tooth stronger and they bond to the tooth creating a better seal than with silver fillings. Like silver fillings, these composite fillings will dissolve over time, and they will discolor.
It’s more common now for dentists to use composite fillings, although silver fillings are approved by the ADA and FDA.