Washington: U.S. health officials are again examining what is known and what is still to be learned about the safety of a mercury mixture that has stirred controversy since dentists began using it to fill cavities in the 1800s. A joint panel of outside experts has voted to reject a draft report that concluded that dental fillings used by millions of people are safe. Yet the panel did not go so far as to declare the mercury-laden amalgam a danger, only that more study is needed because of the risk it poses to some groups.

"For the general population, amalgams are safe. There is evidence of that," said Karl Kieburtz, a University of Rochester Professor and chairman of one of the two panels brought together by the Food and Drug Administration.

An FDA survey of 34 recent research studies did not counter what the agency has said for years: The fillings do not harm patients, except in rare cases where they have allergic reactions.

Research is needed on the effect of mercury on children, the foetuses of pregnant women with fillings and others whose bodies may absorb, distribute, process and eliminate mercury differently, Prof. Kieburtz and others said.