Her body suddenly started to twitch, she had nightmares and her face erupted in boils so painful that it hurt to roll over in bed and touch the pillow.

Doctors suggested drugs for acne and psychological disorders, but MacArthur turned instead to her dentist. He removed nine metal fillings and replaced them with plastic substitutes, and soon she was doing the tango again.

MacArthur, 40, of Alpharetta is one of a growing number of people who believe their medical problems are caused by mercury in dental fillings. Even though dentists often refer to metal fillings as "silver," they are an amalgam of half mercury and the other half a mixture of silver, copper, tin and zinc.

The dental community is sharply divided over whether mercury in fillings is harmful. The American Dental Association stands firmly behind such fillings, saying they only rarely cause problems, in people with mercury allergies, and are more durable than the alternatives. Meanwhile, a legion of "mercury-free" dentists insists that their mercury-using colleagues are slowly poisoning patients because the fillings release the element into the blood. Research findings are mixed.

Lawmakers are starting to say that patients have a right to hear about the pros and cons of mercury fillings. A bill introduced in the Georgia Legislature in March would require dentists to tell patients about the risks of, and alternatives to, the fillings. The bill, by Rep. Bob Holmes (D-Atlanta), also would ban mercury fillings in children and in women age 45 or younger. Last fall, a California congresswoman announced a bill to ban dental mercury nationwide.

Meanwhile, the U.S. Food and Drug Administration is proposing to strengthen its dental mercury regulations with new guidelines for labeling and reporting of side effects, and the National Institutes of Health is spending $9 million for two large studies of mercury fillings in chidlren.

Last week, lawsuits were filed against dental groups on behalf of nine Georgia children with autism, claiming that mercury from their mothers' fillings caused the disease and arguing that dentists deceive patients by calling the fillings "silver." Suits in California and Maryland have accused the American Dental Association of imposing a "gag rule" forbidding anti-mercury dentists from having open discussions with patients.

Caught in the middle are the patients, who don't know whether to rush out and get rid of those shiny spots in their teeth. Some dentists suggest that symptomatic people such as MacArthur, who may have a mercury allergy, should consider getting fillings removed. This is even more true if fillings are old and need to be replaced anyway.

But because removing fillings can actually release more mercury into the body temporarily, the procedure is more risky for people who feel fine.

What is clear is that mercury fillings do release small amounts of colorless, odorless mercury vapor into the bodies of the 100 million Americans who have them, especially after chewing food or brushing teeth. And mercury is a known neurotoxin. The question is whether the emissions are high enough to cause health problems.

Giving 'false hope'

Dr. Michael Ziff, a retired dentist who fought a four-year legal battle over mercury with the dental board in Florida, is now executive director of the Orlando-based International Academy of Oral Medicine and Toxicology, a leading anti-mercury group that has about 400 dentist members. The average American has seven mercury fillings, Ziff said. "It's kind of like holding seven leaking mercury thermometers in your mouth 365 days a year, 24 hours a day."

Dr. Rod Mackert, a dentistry professor at the Medical College of Georgia and one of the ADA's main spokesmen on the issue, said the fillings emit from 1 to 3 micrograms of mercury a day, while people take in 5 to 6 micrograms a day through food, water and air. The ADA prohibits its members from suggesting that patients have fillings removed, though members can comply if a patient requests it.

Mercury fillings have been used for at least 150 years, Mackert said.

"It is unethical to allow the removal of fillings for the curing of any disease, because there is no evidence linking it to systemic disease," he said. "It would be giving the patient a false hope."

A January survey by the Chicago-based Dental Products Report found that 20 percent of dentists no longer use mercury fillings. Among those who do, two-thirds use them in fewer than half the fillings they place.

Dentists who frequently remove mercury fillings, such as Dr. Ron Dressler of Norcross, usually do so for patients who are referred by doctors who treat chronic pain. The doctors run hair or urine tests to detect mercury levels, and high amounts lead to a suggestion to remove fillings.

Dressler performs another test to determine how much mercury vapor is in the mouth. Holding a boxy instrument, he scrapes a straw-like device around the gums, and the detector registers the gas.

Mercury fillings are generally removed in groups, one-fourth of the mouth at a time. They're usually replaced with composite fillings of reinforced plastic resin or, sometimes, with other materials such as gold or porcelain. During metal filling extraction, dentists use vaccuums, air filters, eye covers, oxygen masks and rubber dams over teeth to protect the patient from exposure to excess mercury.

But the process can increase the body's mercury load before decreasing it. To reduce systemic mercury, patients are advised to use some form of chelation, in which drugs that bind to metals are taken orally or intravenously, eliminating the metals through the urine.

Dr. Mark Merlin, a physician at the Atlanta Center for Alternative Medicine in Dunwoody, who tests many patients for mercury, said chelation is crucial when fillings are removed. "You have to get [the mercury] out of the body; it's been leaking into the body for years."

Merlin prescribes amino acids, herbs, vitamin C and intravenous drips of DMPS, a chelating agent. The treatments cost at least $1,000 over several months and often aren't covered by insurance. Health plans generally cover the cost of about $100 per mercury filling, but they often don't pay the additional cost of plastic fillings. Those fillings may run $150 or more.

'Time bomb' in mouth?

Many patients who have had their mercury fillings removed and undergone chelation say the process is worth the price. MacArthur, the ballroom dancer, had her fillings out nearly three years ago. Her nightmares and body twitches disappeared immediately, and her facial boils gradually went away.

"I had a time bomb ticking in my mouth," she said. "You could never convince me that it wasn't mercury."

Hyacinth Meeks, a patient of Merlin's, had a similar experience. Plagued by migraines that made her head throb when she walked even a block, Meeks became frustrated with doctors who put her on mind-numbing sedatives and painkillers. Her dentist was at first reluctant to take out her seven fillings but eventually agreed.

"Within six months, there were no headaches," said Meeks, 48, of Austell, an office manager for an Atlanta wood products firm. "It has totally changed my life."

Felicia Gaston of McDonough believes that her 3-year-old daughter Tylicia's autism was caused by mercury in fillings that seeped into breast milk. She is one of the plaintiffs in the Georgia lawsuits.

"I should have been aware" that metal fillings contain mercury, Gaston said. "I feel like her life has been taken away from her."

Some mercury-free dentists say they're treated like pariahs by their peers, and many are unwilling to speak publicly for fear of reprisal. Dr. Wayne King, a Marietta dentist who opposes mercury, said that, several years ago, the Georgia Board of Dentistry threatened to punish him after he ran a newspaper ad depicting a skull and crossbones with the questions, "Is there poison in your mouth? Do you have symptoms of mercury poisoning?"

King was merely given a letter of reprimand, he said, and records show no official sanctions against him by the dental board. But to King, the don't-rock-the-boat message was clear. "They're afraid to let patients know what we're doing to them," he declared.

Conflicting research

The research is inconclusive, with studies both suggesting and seemingly refuting links to various ailments. The debate even divides institutions: One chemistry study at the University of Kentucky found a relationship between dental mercury and the conditions leading to Alzheimer's disease, while another report at the same school, relying on brain autopsies, found no connection. Research by University of Georgia microbiologist Anne Summers suggests that mercury from dental fillings makes the body more resistant to some antibiotics.

Yet some studies indicate that plastic fillings also may leak hazardous substances into the body, such as xenoestrogens that can disrupt cell activity, said Mackert, the professor and mercury supporter. "Everything has a theoretical risk," he said.

The U.S. Public Health Service says there is no evidence to support claims of adverse effects from mercury fillings except in cases of allergy.

A few countries, such as Sweden and Denmark, recommend that dentists try to use alternative fillings, especially for children and pregnant women. Arizona, California, Colorado and Maine have laws requiring dentists to explain potential mercury risks to patients, said Charles Brown, a lawyer with Consumers for Dental Choice. Brown, a former attorney general of West Virginia, has represented the group in lawsuits in California and Maryland contending that the dental profession threatens dentists who oppose mercury and deceives patients by referring to fillings as "silver."

Last year, the California State Assembly disbanded the state's dental board over the mercury issue. A state senator who took part in that action, Democrat Diane Watson, is now a U.S. representative and, in November, announced a bill calling for stricter warnings, an inmediate ban on mercury fillings in children and pregnant women, and an eventual ban for everyone.

In February, the FDA announced a proposal to upgrade dental mercury from a Class 1 to a Class 2 medical device, which would require the makers of metal fillings to list all product ingredients on labels and encourage dentists and patients to report side effects.

Mackert said patients should ask their dentists about mercury fillings if they're concerned. Most dentists will say the fillings are safe and more durable than plastics, especially for large fillings, but they may grant a patient's request for an alternative.

And a sea change may be beginning. When Mackert needed repair of a tiny mercury filling a few weeks ago, he went with plastic.

THE FILLINGS FILE

A look at the three main materials dentists use for fillings:

Metal

An amalgam of mercury, silver, copper, tin and zinc.