It's a relatively small change - a rewritten page buried deep in the Food and Drug Administration Web site that will list possible health hazards from the use of mercury in dental fillings.
But for a small, vocal group of advocates, it's the culmination of a 32-year battle against the dental establishment, as well as a 10-year lawsuit against the government to force official recognition of their position that these common dental repairs may be a cause for concern.
"I'm really glad that people are starting to wake up to this and realize that putting mercury toxins into our bodies has consequences, and that we need to protect the public," said Gabrielle Hart, a Northwood mother of two and member of Moms Against Mercury, which has struggled with the FDA over the issue.
Under the terms of a lawsuit settlement reached in June, the FDA agreed to finish "classifying" dental mercury and the amalgam fillings that contain it by July 28, 2009 - an agreement that critics call a victory for their cause.
It means the agency will officially investigate and list the possible hazards involved with mercury-based fillings, a process it has delayed for those 32 years. The results will be posted on the FDA Web site.
The American Dental Association, which represents 156,000 American dentists, insists that dental fillings containing mercury are safe. The group cites repeated studies which, it says, prove that such fillings have no ill effects.
The organization also discourages dentists from routinely replacing sound, mercury-based fillings with materials that contain less toxic ingredients.
Still, critics note that dental amalgam is composed of 40 percent to 50 percent mercury, a neurotoxin that can damage the immune system and cause a variety of speech, hearing and vision problems.
Young children are especially vulnerable to its effects, and the government has warned pregnant women and young children to limit their consumption of fish with relatively high mercury levels.
Manufacturers have also removed the mercury-based preservative thermiosol from most children's vaccines. For years, vocal parents have charged that the mercury in vaccines caused autism and other problems in their children, an assertion the government and most scientists vehemently dispute.
For dental use, mercury is mixed with an alloy powder of silver, tin, copper and zinc, and in this so-called "encapsulated" form, most dental authorities say it is perfectly safe.
Dentists in the United States have used it for more than 150 years because it's durable and relatively easy to work. The main alternative filling material is a white resin, which is more aesthetically pleasing because it matches tooth color but generally does not last as long.
According to the trade publication Dental Products Report , 67 percent of dentists use amalgam filings, and most people with fillings have one or more made from amalgam. But critics cite other surveys showing that 72 percent of dental patients aren't aware their fillings contain mercury. This bothers even some who say they believe amalgam is safe.
"Patients need to know what's being placed in their mouths," said Dr. Howard E. Strassler, director of operative dentistry at the University of Maryland Dental School. "Tens of millions of Americans have amalgam in their mouths."
Critics say there are still plenty of concerns about dental amalgam, particularly regarding the developing fetuses of pregnant women.
As a byproduct of the amalgam fillings, small amounts of mercury are released in vapor form, particularly among patients who grind their teeth. The question is how much of a danger this represents.
Dr. Shane S. Que Hee, a professor of environmental health sciences at the University of California, Los Angeles School of Public Health, said the risk "depends on how eroded [the filling] is." As amalgam fillings get old, they deteriorate, increasing the chance of mercury leeching out.
"If they're pretty new, they're pretty safe," said Que Hee. It takes five to 10 years for a filling to start showing signs of wear, he said.
There is little scientific evidence of direct mercury poisoning from amalgam fillings. In 2006, the Journal of the American Medical Association published the results of a five-year study concluding that there was no significant difference in the average IQs of children with amalgam fillings and those with resin fillings.
"Studies over and over again show no long-term effects," said Dr. Caroll-Ann Trotman, associate dean for academic affairs at the University of Maryland Dental School.
As a result, the FDA says patients should not have their amalgam fillings routinely replaced unless they are damaged or fall out, a position echoed by the dental association and many practitioners.
The U.S. Centers for Disease Control and Prevention agrees. Its official position: "At present, there is scant evidence that the health of the vast majority of people with amalgam is compromised, nor that removing amalgam fillings has a beneficial effect on health."
Defenders of amalgam frequently cite these recommendations. "People depend on the FDA and other government health agencies to help protect their health. It's critically important that public health recommendations are based on sound scientific evidence," said Dr. Mark J. Feldman, the American Dental Association president.
"Every time a filling is replaced, it puts the nerve of the tooth at risk," added Maryland's Strassler, who is not a member of the ADA. "To take out an existing filling, additional tooth structure must be removed, which may cause patients to need root canals in the future."
Experts say taking out mercury fillings also temporarily increases levels of mercury in the system.
The Maryland Board of Dental Examiners says dentists cannot remove sound amalgam fillings without telling their patients that there are no verifiable benefits and that removing the fillings could seriously compromise the integrity of their teeth.
Critics say there haven't been enough long-term studies to determine the ultimate safety of amalgam fillings - and they accuse the dental association and FDA of being too cozy. The ADA, they charge, is more worried about avoiding lawsuits than learning the truth.
Charles Brown, attorney for the plaintiffs in the FDA lawsuit, said the longtime use of amalgam is basically for the "dentist's convenience." Although mercury and silver are both expensive, he said, a dentist's time is even more so, and resin-based fillings take about 50 percent longer to complete than amalgam.
"Just because they've used this for 150 years doesn't make it safe," Brown said.
Some countries, including Norway, Sweden and Russia, have banned amalgam in dental fillings - as much for environmental as medical reasons. The World Health Organization says mercury in dental amalgam is the biggest source of mercury vapor in nonindustrial settings.
Maryland has no regulations for the disposal of dental amalgam, although the ADA Web site has a list of "Best Management Practices" that include recommendations.
At the University of Maryland Dental School, amalgam is separated from waste that's incinerated or winds up in sewer systems, according to Strassler. Disposed of properly he said, "mercury from dentists isn't even a measurable amount."
At a glance
The controversial use of mercury-based dental fillings, also called amalgam fillings, prompted consumer group Moms Against Mercury to take the FDA to court - a case that has lasted 10 years.
Although the settlement reached in June required the FDA to change its Web site content pertaining to amalgam and to classify amalgam and its components by July 28 of next year, the idea of getting informed consent from patients receiving such fillings remains an issue. Many patients are unaware that mercury makes up roughly 50 percent of each filling.