Dental Group Defends Mercury Fillings Amid Mounting Evidence of Risks

For decades, the American Dental Association has resolutely defended the safety of mercury fillings in the teeth of more than 100 million Americans, even muzzling dentists who dared to warn patients that such fillings might make them sick.

The association has lobbied the Food and Drug Administration to ensure the fillings, which contain one of the world’s most menacing toxins, receive a government seal of safety and wouldn’t be tightly regulated.

For years, the ADA also resisted Environmental Protection Agency rules that would force dentists to stop dumping tons of mercury debris down public sewer lines, even as the US and 128 other nations negotiated a treaty to curb mercury’s global spread.

But now, evidence is emerging of the potential consequences of the US dental industry’s long-time reliance on mercury and its chief advocacy group’s determined crusade to fend off any and all challenges.

New scientific research has found that the fillings may indeed harm millions of people, especially men and boys. Further, the lax controls over dental clinic discharges have allowed the chemical to spread into rivers and streams, into the air through sludge incineration and even onto cropland as fertilizer.

The new research, by a team based at the University of Washington, concluded that low-level releases of mercury from fillings present long-term risks of brain damage for people with certain genetic variants. The findings are based on data underpinning one of the same two pivotal clinical studies of American and Portuguese children that the dental association has cited as proof the compounds are safe.

In 2006, after results of the initial studies were published, several of the researchers decided to re-evaluate data from 330 Portuguese students to identify those with subtle genetic impairments and see if they were more vulnerable to mercury inhalation in annual tests of their memory, concentration and other neurological activities. Kids with mercury fillings performed significantly worse on the tests than those who got mercury-free treatments.

The results, in four papers published in scientific journals from 2011 to 2014, have escaped public attention, although the authors say up to 40 per cent of the population has at least one of the genetic traits and could be affected. – Greg Gordon

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Many dentists use a “rubber dam” to isolate a single tooth before implanting or drilling out mercury fillings. Mercury is odourless and invisible, and so neither dentists nor patients know how much is in their breathing zones during work with these compounds. Some dentists now wear moon suits with self-contained breathing devices and give their patients separate oxygen supplies to protect them. (Courtesy of Randall Moore)