WEDNESDAY, Dec. 15 (HealthDay News) -- U.S. Food and Drug Administration advisers urged the agency to take a new look at data that may indicate potential safety problems with dental fillings that include mercury.

The FDA had ruled in 2009 that mercury used in so-called amalgam dental fillings is safe.

"We need to see where the science is and if there are gaps," said the panel's chairwoman, Dr. Marjorie Jeffcoat, a dentist and researcher with the University of Pennsylvania, CNN reported.

The advisory panel noted that the FDA's 2009 decision was solid, based on scientific findings available at the time. The panel also stressed that more studies need to be done on the fillings, especially in children, CNN said.

The FDA advisory panel met in response to challenges from consumer and dental groups that contended the FDA relied on flawed data when it set the guidelines for mercury safety levels. Critics of fillings that use mercury as a component contend that they can pose neurotoxic health risks, especially to fetuses and young children.

In July 2009, the FDA placed tighter safety controls on the use of mercury dental fillings, but said they were safe for most people.

Since that time, the agency has categorized the fillings as Class II devices, which puts them into the middle range of risk. Class II devices usually carry some kind of precautions regarding their use.

But FDA officials said at the time of the 2009 vote that the fillings pose no real harm to most people.

"Patients are not at risk for long-term, mercury-related adverse health events," Dr. Susan Runner, of the FDA's Division of Anesthesiology, General Hospital, Infection Control and Dental Devices, said during a July 28, 2009, news conference. "There have only been 141 adverse event reports over 20 years. None resulted in death."

The FDA did recommend in 2009 the following labeling changes: a warning against the use of these fillings in patients with mercury allergy; a warning that dental professionals use adequate ventilation when handling the material for the fillings; and a statement discussing the scientific evidence on the benefits and risks of dental amalgam.

"We're not contraindicating dental amalgam in any patient group [other than those who have allergies]," Runner said at the news conference.

The 2009 ruling brought an angry reaction from the consumer organization Consumers for Dental Choice.

"I'm outraged. FDA broke its word," Charles Brown, the group's national counsel, said at the time of the 2009 vote. "They put a warning a year ago on the Web site and promised to keep those warnings on the Web site that warned of neurological damage to children and unborn children. Bowing to the dental products industry, FDA has, for the first time in memory, withdrawn a warning about neurological harm to children and the unborn. It's a contemptuous attitude toward lower income and minority children because they're the ones that get amalgam. The rich get resin."

The agency decision followed a lengthy debate on the supposed dangers of these fillings, which included a lawsuit filed in 2006 against the FDA by several consumer groups, including Moms Against Mercury and Consumers for Dental Choice.

As part of that settlement, the FDA agreed to classify mercury fillings, also known as dental amalgam, by July 28, 2009, and posted a notice on its Web site that said: "Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses."

Dental amalgam contains elemental mercury combined with other metals such as silver, copper, tin and zinc. The fillings, about 50 percent mercury, have been used for generations to stabilize decaying teeth. Dental experts contend that when mercury is bound to the other metals, it's "encapsulated" and doesn't pose a health risk. Consumer groups, however, contend that mercury, a known neurotoxin, does leak out in the form of mercury vapor and then gets into the bloodstream.

According to the American Dental Association, the use of amalgam is declining. In 1990, dental amalgams made up 67.6 percent of all dental restorations, but by 1999 it was 45.3 percent and, in 2003, an estimated 30 percent. Cavities that previously would have been treated with dental amalgam are now mostly filled with a resin composite.

Several countries have already either banned or advised against the use of mercury fillings.

More information

The U.S. Centers for Disease Control and Prevention has more on amalgam fillings.