The Food and Drug Administration recently asserted that mercury in fillings might be harmful to pregnant women, fetuses, children, people who are sensitive to mercury exposure and to those who have a weakened immune system.

"Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses," wrote the agency on its site.

There will be brought out a new ruling on mercury fillings by July 2009.

When amalgam fillings are placed in or removed from teeth, they release mercury vapor. Mercury vapor is also released during chewing.

The FDA has analyzed this issue before, but it used to assert that there were no scientific proofs to show that amalgam was unsafe. Agency’s officials argued that mercury amalgams were used with skepticism in other countries for no other reasons that environmental. But after concluding an agreement with consumer advocates, the agency revised its view.

FDA pledged it will initiate controls on mercury fillings in July 2009. These controls will consist of giving patients information and adding warnings to prohibit use of the fillings in some categories of people. It is not likely that bans be issued.

About 30% of patients have mercury fillings, according to an assessment made by the American Dental Association. Alternatives to mercury fillings are tooth-colored resin composites, glass cement, porcelain, and other metals like gold. However, mercury was always preferred by dentists, as it was the cheapest and most lasting option.