WASHINGTON, D.C. ? Silver fillings used to patch cavities aren’t dangerous even though they expose dental patients to the toxic metal mercury, federal health researchers said Friday.

The Food and Drug Administration reviewed 34 recent research studies and found “no significant new information” that would change its determination that mercury-based fillings don’t harm patients, except in rare cases where they have allergic reactions.

The FDA released a draft of its review ahead of a two-day meeting next week to discuss the safety of mercury used in dentistry.

Consumer groups opposed to its use disputed the FDA’s conclusions. The groups plan to petition the agency for an immediate ban on use of the cavity-filler in pregnant women.

Amalgam fillings, also called silver fillings, by weight are about 50 percent mercury, joined with silver, copper and tin. Dentists have used amalgam to fill cavities since the 1800s.