Bottle of mercury from the museum of Benco Dental, Pittston, Pa.


An element commonly seen in thermometers in its silver-white liquid form, mercury vaporizes at temperatures as low as 10 degrees Fahrenheit. The vapor is colorless and odorless, is readily absorbed by the blood, and evenly distributes in the brain, kidney, heart, lungs, and liver. However, it demonstrates a predilection for collecting in the central nervous system, from which elimination is very slow.

The dangers of mercury have only been noted since the early 19th century, so it was used for all manner of medical treatment since ancient times.

It was a prime ingredient in:

  • Calomel, a 19th century medicine used to treat everything from teething babies to typhoid pneumonia.
  • Dental amalgam, starting in the 1830s. This led to discussions in dental journals concerning the debilitating effects of using mercury in dental fillings. Today, with the invention of better amalgams, those concerns have largely evaporated.

Antique Caulk mercury alloy gauge from the dental museum of Benco Dental.

What causes mercury poisoning?

Mercury poisoning or intoxication results from cumulative exposure. Muscular tremors are the first observable sign, sometimes initially seen in the handwriting. It can progress

Screenshot 2017-06-28 14.02.18

Actor Johnny Depp discusses his transformation into Disney’s Mad Hatter :

to a multisymptomatic illness characterized by fatigue, insomnia, depression, headache, slurred speech, and a host of peculiar psychic disturbances. The term “Mad as a Hatter” was coined in the 19th century due to the symptoms of mercury poisoning exhibited by milliners, who used mercury in the making of hats.

Hettingers Dental News

Advertising for the Caulk mercury scale from a 1919 dental catalog.

By the late 90s, at least 10 percent of dental offices in the United States had ambient mercury levels above the National Institute for Occupational Safety and Health recommendations. The biggest problem for dentists was inhalation of mercury vapors. Then, devices like the Mercury Vapor Sniffer, Mercury Vapor Meter, Mercury Vapor Monitor, Mercury Vapor Analyzer, and the Mercury Vapor Detector were available to find and reduce mercury vapor levels.

Thankfully, mercury use has subsided and so has the need for items like the above artifacts. See, the good old days weren’t always so good.

How does the EPA weigh in on mercury discharge from dental practices?

Good question.

According to,

The U.S. Environmental Protection Agency (EPA) will lift its hold on finalized standards to reduce the discharge of mercury and other metals in wastewater from dental practices into municipal sewage treatment plants on June 14, 2017. The rule will go into effect on July 14, 2017, with a compliance date for dental offices of July 14, 2020.

Find out what the American Dental Association President has to say on the matter: