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ADA Laboratory Tests Find Lead Not Released From Dental Crowns
Crowns subjected to testing conditions far more extreme than found in mouth
CHICAGO, March 24, 2009—Comprehensive testing and analyses by the American Dental Association (ADA) found no detectable amount of lead released from the 102 porcelain–metal dental crowns evaluated even under extreme laboratory testing conditions.
Scientists from the ADA Division of Science and the ADA's Paffenbarger Research Center (PRC) laboratories in Gaithersburg, Md., conducted the tests in response to concern over the safety of dental crowns. The PRC laboratory analyzed 44 porcelain powders –raw materials used to make dental crowns–from different manufacturers and 102 finished porcelain-metal crowns produced by domestic and foreign dental laboratories.
Scientists evaluated dental materials for lead content, release of lead
Lead can be found in a number of porcelain products such as dinner plates and figurines. Feldspathic porcelain is a natural mineral that is mined from the earth and refined for dental use. As such, porcelain will contain naturally occurring trace elements of lead in varying concentrations, depending on the source and refining process.
In assessing for total lead content, ADA scientists completely dissolved the powders and finished crowns, and measured the amount of lead remaining in the solution, finding only trace amounts of the naturally occurring element. The results ranged from below detectable to 113 parts per million (ppm) in the 44 porcelain powders, and an average of 46 ppm in the 102 porcelain dental crowns.
Second, but more importantly, the researchers also tested the finished crowns for the release of lead (to test the potential body exposure to the element) under laboratory conditions far more extreme than could occur in the mouth. This testing yielded no measureable lead escaping from the porcelain crown (with a limit of detection at one ppm), even under accelerated acidic conditions at elevated temperatures.
"Based on all the information to date, both from our own testing as well as reports of other analyses, we are confident that no measurable levels of lead are released from dental crowns made from dental porcelain typical of available sources," explains Clifton Carey, Ph.D., administrative director, PRC.
He added, "Moreover, we intentionally added lead to a separate sample of dental crowns and found that even up to 500 ppm of lead levels, no measurable amount was released. This was a much higher total concentration than any laboratory-fabricated crown tested."
Questions were raised in February 2008 about lead in dental restoratives such as crowns and bridges when an Ohio woman speculated in a news report that the problems she experienced with her bridge might be because of its manufacture at a dental laboratory in China. At a time when other products from China were under scrutiny, the local news station investigated the issue and sent the bridge to a local laboratory for lead testing. The station then had several dental crowns manufactured in China tested, and one crown reportedly tested positive for lead. At the time however, no accepted standardized method existed to measure lead content of dental materials such as porcelain, or whether lead is released from dental crowns in the mouth.
ADA commits time, resources to design lead test, conduct laboratory testing
The ADA reacted quickly to the news story, notifying member dentists, posting information for the public and contacting the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) to ensure that the agencies were aware of the issue.
In addition, the ADA designed a new research method to measure lead concentration, obtained sample dental crowns from laboratories in China, the U.S. and other countries, and then tested the crowns to determine the amount of lead present and, most importantly, whether any lead is released from the crowns.
The ADA has shared these test results with the CDC and the FDA—the regulatory agencies responsible for protecting the public's health. In addition, the ADA has posted information on www.ada.org for dental professionals and the public.
About the American Dental Association
Celebrating its 150th anniversary, the not-for-profit ADA is the nation's largest dental association, representing more than 157,000 dentist members. The premier source of oral health information, the ADA has advocated for the public's health and promoted the art and science of dentistry since 1859. The ADA's state-of-the-art research facilities develop and test dental products and materials that have advanced the practice of dentistry and made the patient experience more positive. The ADA Seal of Acceptance long has been a valuable and respected guide to consumer dental care products. The monthly Journal of the American Dental Association (JADA) is the best-read scientific journal in dentistry. For more information about the ADA, visit the Association's Web site at www.ada.org
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