In updated guidelines, the U.S. Food and Drug Administration (FDA) is warning that dental amalgam fillings may cause health problems for some high-risk groups because of mercury vapor leaks. Among those advised to avoid amalgams, which contain mercury, silver, copper and tin, are pregnant women; women that plan to become pregnant or are nursing; children, especially those under the age of 6; and those with kidney problems or preexisting neurological conditions such as multiple sclerosis, Parkinson’s or Alzheimer’s. Over time, amalgams can release small amounts of mercury vapor, depending on how extensively people grind their teeth or chew gum and how old the filling is, studies show. It’s a more cautious tone for the FDA, which along with the American Dental Association, has long maintained that amalgams are safe, a finding disputed by health advocates. Mindful of health and aesthetics, patients are increasingly opting for tooth-colored resin composites. Nearly half of all U.S. dentists no longer use mercury, and its use is being legally phased out in more than a dozen countries.