While the phrase “mad as a hatter” might bring up images of  Alice’s Adventures in Wonderland, what it described was hardly the stuff of fantasy.

 Back in the 18th and 19th centuries, workers typically used mercury to convert animal pelts into felt for hats. Mercury is highly toxic, especially to the brain. Exposed to so much of the stuff, hat makers often developed tremors (known as “hatter’s shakes”), speech difficulties, emotional instability, and hallucinations. A hat maker could appear quite literally “mad” or “crazy.”

 Yet Some Thought Filling Teeth with This Toxin Was a Good Idea

Despite mercury’s known danger to human health, an early 19th century English chemist used mercury in an alloy he had developed for filling decayed or damaged teeth. By 1830, American dentists had begun using this dental amalgam, and it wasn’t long before harmful effects were being reported.

 Ultimately, our country’s first professional association of dentists, the American Society of Dental Surgeons, took a stand and discouraged the use of mercury amalgam. They even required their members to take a pledge that they would never use the material.

 But some dentists kept using it, largely for the same reasons it continues to be used by many dentists today: Amalgam is cheaper, and it’s faster and easier to place than alternative materials, so you can treat more patients in less time. These renegade dentists eventually formed a rival organization that went on to normalize mercury fillings: the American Dental Association (ADA).

 Waking Up to the Dangers of Dental Mercury

For over 150 years, the ADA held that mercury fillings were completely safe. Even after the FDA updated its guidance in 2020 and now discourages the use of amalgam in nearly two-thirds of the American population, the ADA held firm. “Dentists have used dental amalgam for a long time, and we know that it’s durable, reliable and safe,” said ADA President Chad P. Gehani in a news release issued in response to that new guidance.

 Recently, the ADA started to pivot. According to Charles Brown of Consumers for Dental Choice, the ADA “substantially realigned its position on amalgam, pulling back from its hard-line position of pushing amalgam onto American consumers,” as reflected in the organization’s mercury policy statement.

 ·         They no longer say mercury amalgam poses no health hazards.

·         They now support reducing environmental mercury, much of which comes courtesy of the dental industry.

·         They have withdrawn its policy of supporting dental boards in attacking mercury-free dentists.

 Other events led up to this, of course. First came the Minamata Convention on Mercury, a global treaty that includes provisions toward a phase down of dental mercury. The FDA’s revised guidance followed years of other nations, including those in the EU, taking action to limit the use of dental amalgam. Soon, the two biggest makers of dental problems opted to quit the amalgam business altogether.

 This was all helped along by people becoming more informed about the risks of mercury fillings and the availability of nontoxic alternatives that are also far more aesthetic.

 All this is a welcome change.