By SARAH AVERY
Raleigh News and Observer
January 14, 2010
About 40 million Americans have dentures and use adhesives to secure them, and the products have long been considered benign. The American Dental Association said in its statement it knows of no confirmed cases of dental glues causing nerve damage.
The products, Poligrip brands from GlaxoSmithKline and Fixodent from Procter & Gamble, use zinc as a bonding agent. Scientists have only recently drawn a possible link between the zinc-containing denture creams and neurological problems. Glaxo says its product is safe if used properly.
The poison is in the dose. Although zinc is an essential mineral for cell function, it can be harmful in high doses because it inhibits the absorption of other minerals. As a result, people who ingest too much zinc develop copper and iron deficiencies that can lead to severe numbness and weakness from nerve damage.
Most of those who have reported illness used excessive amounts of dental adhesive, often because their false teeth fit poorly and require more cream to form a bond.
"It's a pretty rare problem," said Dr. Michael Cartwright, an assistant professor of neurology at the Wake Forest University School of Medicine who has treated patients with the suspected link. "There are many, many people who use denture cream who don't develop any kind of neurologic disease. We don't know why it happens in some people -- if they're using large amounts (of denture cream), or if they have some other predisposition to copper deficiency."
GSK officials, in a written statement, said the denture glue is not harmful if used normally. In addition, the company last fall began including a package insert for its Poligrip products: "Using excessive amounts of this product over a prolonged period of time has been reported to result in serious health effects from increased zinc intake."
The insert also urges people to talk to their doctors before using Poligrip if they are also taking zinc supplements, which are popular as immune boosters to ward off colds.
The link between the dental glues and nerve damage was first noted in 2008, when scientists at the University of Texas Southwestern Medical Center published a report in a prominent medical journal. The scientists suspected dental creams were behind some patients' symptoms, and they tested tubes of adhesive for zinc, which at the time wasn't listed on the product ingredients.
The report spurred additional analyses -- one finding that a denture cream contained zinc at four times the recommended daily allowance.
Many neurologists began asking patients whether they wore dentures.
Cartwright said he first heard of the connection at a medical meeting a few years ago, and he has diagnosed some cases. He said his patients have not regained normal limb function even after the mineral imbalance is corrected. Still, he said, further harm is halted.
Johnny Howell, 53, of Winston-Salem, N.C., says Poligrip was the source of zinc poisoning he suffered over at least 20 years, causing his legs to suddenly buckle beneath him. He eventually lost his job as a mechanic and had to go on disability.
"I can't walk, I can't drive," he said. "I fell down and broke a rib because of it. I broke my ankle. I cracked my wrist."
He plans to sue GSK this week. The company faces at least 15 other lawsuits in Philadelphia, where it has another headquarters. About 70 cases have been filed against both GSK and Procter & Gamble in a federal court in Florida.
Ed Blizzard, a Houston lawyer who is representing Howell and dozens of other patients, said many of the people he represents have suffered permanent disabilities, and at least one person has died.
As a result, he said, GSK's disclosure and warnings come too late. For years, he said, consumers had no idea that the tubes of adhesive contained zinc or that zinc could be so harmful in high doses.
"Glaxo says, 'Don't use the product in excess,'" Blizzard said, "as if these people were alcoholics or something. They're just trying to keep their teeth in their mouth."
Howell said he first developed symptoms in 2004 -- 15 years after using the cream once a day on his upper plate and twice on the lower.
Scripps Howard News Service, http://www.scrippsnews.com
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