Zinc Poisoning Linked to Popular Denture Creams
Reports Suggest Overuse of Fixodent and Older Version of Poligrip May Cause Nerve Damage
Linking Zinc Poisoning to Denture Cream continued...
"To fact-check my revisions, I shared it with a colleague at P&G," Shay tells WebMD. "I said, 'Don't share this around, but I'm interested in if the following facts are true or not. ... There was no sense of 'Squash this,' or anything. It was entirely my way of trying to make sure my review was accurate."
The ABC report implied that Shay managed to delay publication of the Nations report by about two years. In fact, it appeared some 15 months after it was submitted, "in line with standard time frames," according to the American Academy of Neurology.
And regardless of how the Nations team measured zinc, Shay -- a geriatric dentist at the Ann Arbor VA who has studied dental-cream use -- admits that many patients with poorly fitting dentures use wildly excessive amounts of denture cream to make them fit.
The irony, he says, is that the cost of using dental cream in this way quickly exceeds the cost of new, better-fitting dentures.
Is Fixodent Safe? Is Poligrip Safe?
Before May 2010, Poligrip contained a relatively small amount of zinc -- about 34 milligrams per gram in the original formulation and about 27.5 milligrams per gram in the Polyseal formulation, Nations and colleagues found. In February 2010, GlaxoSmithKline sent a "Dear Doctor" letter warning that excessive use of the product by patients could be dangerous.
"These patients should be advised to consult their dentist for advice," wrote GlaxoSmithKline chief medical officer Howard Marsh, MD.
Fixodent contains smaller amounts of zinc -- about 17 milligrams per gram, according to the Nations study.
According to P&G spokeswoman Tricia Gottlieb, the amount of zinc "an average denture adhesive user would ingest from daily usage of Fixodent" is less than the zinc in most daily multivitamins, less than the zinc in six oysters, and comparable to the zinc in 6 ounces of ground beef.
Gottlieb notes that when used correctly, a 2.4-ounce tube of Fixodent should last six to eight weeks. Patients suffering nerve damage tended to use far more: two or even three tubes a week.
What isn't known is how many people have been using such large amounts of dental cream or how long they've been doing it. Those who continue to use Fixodent in this way are clearly at risk.
Symptoms of Zinc Overdose
Hedera and colleagues examined 11 patients with nerve damage linked to dental cream. Seven had been using Poligrip, three had been using both Poligrip and Fixodent, and one had used only Fixodent.
Symptoms began with numbness and movement difficulty affecting the feet and legs. This rapidly progressed to the arms, and patients began losing their sense of balance.
The patients' bone marrow suppression -- resulting in low counts of both red and white blood cells and platelets -- got better when they stopped using dental cream.
Some of the patients' neurologic symptoms improved, but most remained impaired. Three remain in wheelchairs, five need walkers, and one uses a cane. One no longer needs a cane, and another patient, who never lost the ability to walk, made an "almost complete recovery."