The problem is thought to be rare. The peculiar thing about this finding is that no amount of safety testing on the zinc itself could have detected the problem. That's because the problem does not come directly from zinc. Rather, is in the effect that zinc has upon the absorption of copper.
From a recent issue of Neurology ($ for full access):
Denture cream
An unusual source of excess zinc, leading to hypocupremia and neurologic disease
NEUROLOGY 2008;71:639-643
doi:10.1212/01.wnl.0000312375.79881.94
Background: Chronic, excess zinc intake can result in copper deficiency and profound neurologic disease. However, when hyperzincemia is identified, the source often remains elusive. We identified four patients, one previously reported, with various neurologic abnormalities in the setting of hypocupremia and hyperzincemia. Each of these patients wore dentures and used very large amounts of denture cream chronically.
Objective: To determine zinc concentration in the denture creams used by the patients as a possible source of excess zinc ingestion.
Methods: Detailed clinical and laboratory data for each patient were compiled. Tubes of denture adhesives were analyzed for zinc content using dynamic reaction cell-inductively coupled plasma-mass spectrometry. Patients received copper supplementation. Copper and zinc levels were obtained post-treatment at varying intervals.
Results: Zinc concentrations ranging from about 17,000 to 34,000 µg/g were identified in Fixodent and Poli-Grip denture creams. Serum zinc levels improved in three patients following cessation of denture cream use. Copper supplementation resulted in mild neurologic improvement in two patients who stopped using denture cream. No alternative source of excess zinc ingestion or explanation for hypocupremia was identified.
Conclusion: Denture cream contains zinc, and chronic excessive use may result in hypocupremia and serious neurologic disease.
This illustrates a subtlety in toxicity testing. It is unlikely that any feasible testing regimen would have led to an a priori anticipation of the toxicity.
At least, that is the way it seems to me. Perhaps someone with greater expertise in toxicology could chime in.
Comments
No surprise.
http://www.google.com/search?q=zinc+fume+fever
http://scholar.google.com/scholar?q=zinc+fume+fever
Zinc toxicity on cultured cortical neurons: involvement of N-methyl-D-aspartate receptors
JY Koh, DW Choi - Neuroscience, 1994 - grande.nal.usda.gov
Author: Koh, JY : Choi, DW. Citation: Neuroscience. ...
Just picking one paper arbitrarily out of the many that show up.
Anyone who's done soldering indoors without sufficient ventilation has probably experienced this to some extent.
Posted by: Hank Roberts | September 1, 2008 2:38 AM
This is pretty good, full text available; extensive footnotes
http://www.cmaj.ca/cgi/content/full/169/2/129
CMAJ • July 22, 2003; 169 (2)
© 2003 Canadian Medical Association or its licensors
Element of caution: a case of reversible cytopenias associated with excessive zinc supplementation
-------excerpt---follows------
Copper-deficiency anemia secondary to zinc excess was first reported in 1977,7 and 18 cases have subsequently been reported.8,9,10,11,12,13,14,15,16 Most of these cases involved self-medication with OTC dietary supplements; the daily amount of zinc ranged from 29 mg for 7 months12 to 2000 mg for 3 months.16 The daily zinc intake of our patient was 100 to 120 mg for 5 years. Instructions on a bottle of OTC zinc lozenges recommend 5 to 20 mg every 2 hours during the onset of a cold, to a maximum of 50 mg daily.
Copper deficiency secondary to zinc excess arises from an indirect interaction between the 2 metals in the intestine. When exposed to excess dietary zinc, the absorptive duodenal cells upregulate metallothionein, an intracellular metal-binding ligand.17 Metallothionein binds both zinc and copper ions but has a much greater affinity for copper. Dietary copper that is bound to metallothionein becomes sequestered within the duodenal enterocytes, which are sloughed into the intestinal lumen.18 Increased oral copper intake is ineffective in restoring the zinc–copper balance in the presence of excess dietary zinc, as the induced metallothionein continues to intercept the copper and reduce its absorption. This explains why our patient, despite taking twice the RDA of copper, became copper-deficient over time. Since ceruloplasmin, the main copper metalloprotein in the blood, is produced by the incorporation of cupric ions into a protein moiety, copper deficiency also results in reduced production and therefore a reduced serum concentration of ceruloplasmin....
Posted by: Hank Roberts | September 1, 2008 2:44 AM
OK, the references about zinc toxicity are not directly relevant, since the denture-adhesive-using patients did not have zinc toxicity. But the ones about zinc supplementation are pertinent. Still, the patient described in the CMAJ paper had anemia; the neurological symptoms were attributed to her underlying illness.
50mg of zinc is equal to 50,000 micrograms. The denture adhesives have 17,000 to 34,000 µg/g. I don't know how many grams of adhesive typically would be used. I would think one or two grams would do, so I guess that would fall into the correct range. How much of that is absorbed? Again, don't know, I would guess much less than 100%. But the idea of a patient developing problems from the zinc is not so improbable as I had thought. Thanks for finding that.
Posted by: Joseph j7uy5 | September 1, 2008 3:49 AM
This news is shocking to me. I am a dentist who sees quite a number of denture patients. Until today, when I saw an ad on television from a lawyer searching for patients who have "nerve damage due to use of denture adhesives" I had no idea there was a problem with its use. Certainly I considered the digestive issues with patients who excessively use denture adhesive, but certainly not neurological issues. I am glad to now be aware, and have more knowledge base to answer the questions that I am sure will now arise when patients see the same advertisement I did.
Posted by: Lisa | March 13, 2009 7:25 PM
I have been using fixedent for a number of years in November of 2008 I developed arthiritis and was told I now have a frozen shoulder where do I go to get tested for zinc and what other problems will it cause. Thank you
Posted by: Carole Lackey | March 25, 2009 2:37 PM
Denture creams, like Poligrip and Fixodent have been associated with a variety of neurologic health problems and several lawsuits have been filed by people who claim to have been sickened by these products. It is expected that many more will be filed in the coming months. There is some good information on the health and legal implications involved with this issue at: http://www.denturecreamlawyer.com/
Posted by: Cynthia | September 1, 2009 1:55 AM
The new warning about zinc in Super Poligrip is not adequate. The warning states that swallowing small amounts of Super Poligrip is not harmful; however, the warning is misleading and might be doing more harm than good. Ingesting even small amounts of Super Poligrip has been found to be harmful; people who used normal amounts of Super Poligrip, and who swallowed small amounts of the product, suffered from zinc poisoning and neurological problems. Here is a site that is very informative and offers some help: http://poligrip-lawsuit.com/about-us.html
Posted by: Cynthia | October 19, 2009 9:26 AM
Denture creams such as Poligrip and Fixodent have been linked to neurological and other problems. This site has some good information and recourse options: http://www.denturecreamlawyer.com/
Posted by: Cynthia | November 16, 2009 7:58 AM