CDRH is willing to do some more number-crunching on its 2009 decision that mercury from dental amalgam is safe for all patients, in light of new data that most of the U.S. population may be exposed to higher levels of the toxin in their fillings than is acceptable, FDA officials said at a recent advisory panel meeting.

In July 2009, the agency reclassified amalgam, used by dentists to fill cavities, from a high-risk Class III device to a moderate–risk Class II device with special controls, and declared the product to be safe for use in patients. (See “ Also see "Regulatory News In Brief" - Medtech Insight, 3 August, 2009. ” – “The Gray Sheet” Aug. 3, 2009.)

But since that reclassification decision, questions raised by four citizens’ petitions point to fresh data on the risks of mercury exposure from amalgam, data that bears further examination, CDRH’s Anthony Watson said at a panel meeting last week in Gaithersburg, Md. Watson, chief of the FDA division that evaluates dental devices, said the Dec. 14-15 gathering was convened to aid in the agency's reassessment.

New data suggests the majority of the adult population will exceed safe reference exposure levels – CDRH’s Anthony Watson

Watson pointed to new data from toxicologist Mark Richardson, Ph.D., of SNC-Lavalin.

Richardson's findings suggest the possibility that, “Regardless of which safe reference [mercury] exposure level we at FDA choose, the majority of the adult population will exceed that level," Watson said.

Richardson, who formerly conducted risk assessments for Health Canada, explained that estimates of mercury exposure from dental amalgam have improved recently because of new numbers compiled from a large portion of the U.S. population by the Centers For Disease Control and Prevention’s National Health and Nutrition Examination Survey and studies conducted for Health Canada based on dentists’ occupational exposures.

Subgroups, Confounders Will Be Considered

According to Peter Goering, a toxicologist at CDRH, FDA's adjusted risk assessment will include better analysis of varying exposure levels in different subpopulations and closer attention to more variables and confounders.

“There are confounders we haven’t even brought into this discussion. … For example, we know alcohol decreases mercury release in blood, and that smoking increases it, and so forth,” Goering said.

FDA will include better analysis of varying exposure levels in different subpopulations in its adjusted risk assessment, according to Peter Goering, CDRH toxicologist.

The toxicologist said that FDA would also consider consensus reached by panel members that urinary mercury levels used to estimate human exposures “are not the gold standard,” and should be replaced by newer technologies to detect body burdens of mercury.

Goering also agreed with the panel that several “uncertainty factors” developed by the U.S. Environmental Protection Agency should be factored into CDRH’s dental amalgam assessments to address susceptible populations such as pregnant mothers and their fetuses, very young children and persons with known sensitivities to metals.

Petitioners Call For Class III Status, Bans

Among the petitioners who called upon FDA to re-think its 2009 assessment are attorneys James Love and Robert Reeves of Tulsa, Okla.; Richard Edlich, M.D., a distinguished professor emeritus at the University of Virginia; and attorney James Turner, representing Citizens for Health. Love also filed a second petition for Moms Against Mercury in September 2009.

Love argues that there is a significant correlation between mercury dose and urinary porphyrins and requests that FDA require more clinical data on the tie-in and return amalgam to Class III status.

Edlich’s petition said that FDA should require dentists to obtain informed consent from patients who are informed of the risks of the mercury in amalgam before placing it. Ultimately, though, he recommended that amalgam be banned.

The need for full disclosure and informed consent was repeated by many speakers at the meeting and endorsed by several panelists.

“As a periodontist, I need to see these warnings [about mercury] put on these products,” panel chairwoman Marjorie Jeffcoat commented.

“As a periodontist, I need to see these warnings [about mercury] put on these products,” said Marjorie Jeffcoat, panel chair.

Dental Groups Continue To Support Amalgam

Nevertheless, representatives of several dental associations lent strong support to the use of amalgam in dental fillings, arguing that they have been used safely and effectively for more than 100 years.

“The National Dental Association believes that dental amalgam is safe,” said dentist Leslie Grant of NDA. “No new evidence shows dental amalgam is dangerous," she contended.

Mary Tavares, D.D.S., with the American Association of Dental Research, said her group “supports the agency’s decision” in 2009 to make mercury-containing amalgam a Class II device.

But the vast majority of public speakers at the meeting were individuals who argued that they had suffered neurological diseases, partial blindness, paralysis or other debilitating symptoms either shortly after their teeth had been filled with amalgam, or when it was removed.

“No new evidence shows dental amalgam is dangerous” – Leslie Grant, National Dental Association

While FDA will not necessarily change its 2009 rulemaking, the agency says it is committed to a thorough review of the scientific debate, including the issue of how much mercury vapor the average American is exposed to, and what data support that estimate.

In the meantime, many dentists have already switched to alternative composite materials.

Norway, Sweden and Denmark have placed partial bans on use of mercury in dental amalgam in recent years, says Carolyn Vickers, of the World Health Organization's public health and environment staff. However, most countries still use the amalgam because it is less expensive than alternatives, she said.

A WHO consultation in November 2009 recommended that a phase-down in the use of mercury in amalgam could be achieved by research and development and promotion of cost-effective alternatives, education of dental professionals and raising public awareness.

By Sue Darcey

FDA Will Review Safety Of Dental Amalgams In Light Of New Data

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