Particulate mercury is significant source of exposure to mercury in dental profession

Authors Drs. David Warwick, Matthew Young, John J. Palmer and Robin Warwick Ermel noted that there are many people in the dental profession who are at significant risk of exposure to mercury from dental amalgam. They include dental office staff, dentists, dental assistants, dental hygienists, dental students, dental instructors, dental laboratory staff and sterilization technicians. The authors stated that it has previously been reported in other studies that members of the dental profession have been found to have higher mercury levels in blood, urine, stool, nails, hair and organs than controls had. It is also well documented that mercury vapor can be absorbed through the skin or by inhalation.

The results of the study showed that drilling dental amalgam generates particulate that volatilizes significant amounts of mercury vapor generally for more than an hour after removal of the amalgam. The levels of the mercury vapor created by this procedure frequently exceed the safety thresholds of several jurisdictions and agencies. A report by the National Capital Poison Center stated: “In the absence of a compelling reason, such as an allergic reaction, it is not recommended that amalgam fillings be removed. In fact, the drilling required to remove amalgam fillings can expose the individual to a minor increased amount of mercury in blood plasma.”

There are many factors that can cause a dentist to use high-speed drilling on dental amalgam. Warwick and his colleagues list some of these. They include sectioning of a tooth to facilitate dental extraction, failed seal of an existing amalgam restoration, recurrent caries under a filling, fracture of a tooth with an amalgam filling, adjustment of an incorrect bite, preparation for a fixed or removable prosthesis, root canal access opening, reshaping of an existing amalgam restoration, removal of an amalgam restoration that has an open interproximal contact, removal to prevent galvanism with another intraoral metal, removal for health reasons, removal to reduce exposure of mercury and removal owing to mercury sensitivity. In addition, it can be necessary as part of the treatment for periodontal disease.

At the upcoming third meeting of the Conference of the Parties to the Minamata Convention on Mercury, dental amalgam will be a focal point. Although dental amalgam is one of the top intentional use products containing mercury, the risk of exposure while removing dental amalgam has not yet been investigated. This new information on exposure in the dental profession reveals a problem that needs to be addressed, and that has not been included in previous meetings.

The study, titled “Mercury vapor volatilization from particulate generated from dental amalgam removal with a high-speed dental drill—a significant source of exposure,” was published online on July 17, 2019, in the Journal of Occupational Medicine and Toxicology.

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