Dental mercury research suggests lower toxicity

November 13, 2009

The work of a U of S research team has shown that the surface forms of mercury in older “silver” dental fillings, also called amalgams, may be less toxic than previously thought.

“The dental amalgam on the surface of an old tooth filling may have lost as much as 95 per cent of its mercury,” said Graham George, professor of geological sciences, Canada Research Chair in X-Ray Absorption Spectroscopy and study leader, “but what’s left is in a form that is unlikely to be toxic in the body.”

The work of the research team from geological sciences, which includes research associate Satya Singh and associate professor and CRC Ingrid Pickering along with Dr. Jay Hoover from the College of Dentistry, was published in the American Chemical Society journal Chemical Research in Toxicology.

George does caution that more work is needed to determine when, how and in what form the mercury is lost from fillings because the significant mercury loss revealed by the study is “still of concern.”

A university news release said that while fresh fillings contain metallic mercury that can be toxic, older fillings used a form of mercury called beta-mercuric sulfide or metacinnabar which is unlikely to be toxic. Grinding or polishing teeth during dental cleanings, therefore, is unlikely to have an adverse affect. Of greater concern is the nature of the surface mercury which may be lost through evaporation, exposure to some dental products like those containing peroxide, exposure to sulphur-containing foods like onion, garlic or coffee, or other factors.

The research team worked at the Stanford Synchrotron Radiation Lightsource to examine the amount and chemical make-up of mercury in both new fillings and aged fillings from the College of Dentistry’s tooth bank.