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Too many dental amalgam fillings may increase blood mercury levels


Tooth with dental amalgam fillingDental amalgam has been the go-to dental filling material for more than 150 years, because it’s affordable and durable. However, about half of the compound contains mercury, a heavy metal known to be toxic at high levels, causing brain, heart, kidney, lung and immune system damage. New research suggests that methyl mercury may cause damage even at low levels.
According to its website, the U.S. Food and Drug Administration considers dental amalgam fillings safe for adults, but says, “pregnant women and parents with children under six who are concerned about the absence of clinical data as to long-term health outcomes should talk to their dentist.”

Mercury exposure from dental fillings is not a new concern, but previous studies were inconsistent and limited, according to Xiaozhong “John” Yu, assistant professor of environmental health science and co-author of the study.

The new study:
This research, which analyzed data from nearly 15,000 individuals, is the first to demonstrate a relationship between dental fillings and mercury exposure in a nationally representative population. The results were published in the December issue of the journal Ecotoxicology and Environmental Safety.

“Tooth decay is one of the most prevalent chronic diseases,” said Lei Yin, a scientist in the department of environmental health science and the study’s lead author. “I think a majority of people have experienced dental fillings, but the kind of materials the dentist uses isn’t something that’s really discussed.”

“This study is trying to provide the most accurate levels of exposure, which will form the scientific basis to make future risk assessment,” Yu said, adding that the study was the first to also control for age, education, ethnicity, race, gender, smoking and seafood consumption, which is a known contributor to mercury levels in the body.

The researchers further analyzed exposure by specific types of mercury and found a significant increase in methyl mercury, the most toxic form of mercury, related to dental fillings. Yu said this result suggests the human gut microbiota, a collection of microorganisms living in the intestines, may transform different types of mercury.

“As toxicologists, we know that mercury is poison, but it all depends on the dose. So, if you have one dental filling, maybe it’s OK. But if you have more than eight direct surface restorations, the potential risk for adverse effect is higher,” Yu said. People with numerous dental fillings who are also exposed to mercury from other sources, such as seafood or work environments, are most at risk.

The results show that individuals with more than eight fillings had about 150 percent more mercury in their blood than those with none. The average American has three dental fillings, while 25 percent of the population has 11 or more fillings.

The study also looked at dental composite resins, a mercury-free alternative for dental fillings that can release small amounts of bisphenol A, or BPA, which may cause developmental or reproductive damage. The results found no association between dental fillings and urinary BPA, but further research is needed to understand BPA exposure from resin-based materials.

“It’s important for doctors and patients to be informed in their selections,” Yin said. “We now have an excellent starting point to evaluate the potential risk of dental material on human health.”

Xiao Song from the department of epidemiology and biostatistics in the UGA College of Public Health, and Simon Lin from the University of Washington’s Center for Pediatric Dentistry also contributed to the study.

Data for the research were provided by the National Center for Health Statistics, which conducts the National Health and Nutrition Examination Survey. This work was supported by CDC R21 OH 010473, ARDF and UGA Start-up Research funding.

Story Source: Materials provided by University of Georgia. Note: Content may be edited for style and length.

The original study

Lei Yin, Kevin Yu, Simon Lin, Xiao Song, Xiaozhong Yu, Associations of blood mercury, inorganic mercury, methyl mercury and bisphenol A with dental surface restorations in the U.S. population, NHANES 2003–2004 and 2010–2012, Ecotoxicol. Environm. Safety, 134/1 (2016) 213–225. doi: 10.1016/j.ecoenv.2016.09.001

Related studies (newest first)

John Kall , Amanda Just , Michael Aschner, What Is the Risk? Dental Amalgam, Mercury Exposure, and Human Health Risks Throughout the Life Span, in: D. Hollar (ed.), Epigenetics, the Environment, and Children’s Health Across Lifespans, Springer Switzerland (2016) 159-206.  doi: 10.1007/978-3-319-25325-1_7

Hye-Jin Baek, Eun-Kyong Kim, Sang Gyu Lee, Seong-Hwa Jeong, Jun Sakong, Anwar T. Merchant, Sang-Uk Im, Keun-Bae Song, Youn-Hee Choi, Dental amalgam exposure can elevate urinary mercury concentrations in children, Int. Dental J., 66 (2016) 136–143. doi: 10.1111/idj.12214

G. Mark Richardson, Mercury Exposure and Risks from Dental Amalgam in Canada: The Canadian Health Measures Survey 2007–2009, Hum. Ecol. Risk Assess., 20/2 (2014) 433-447. DOI: 10.1080/10807039.2012.743433

Faheem Maqbool, Haji Bahadar, Mohammad Abdollahi, Exposure to mercury from dental amalgams: a threat to society, Arh. Hig. Rada. Toksikol., 65 (2014)  339-340. doi: 10.2478/10004-1254-65-2014-2543

R.J. Birch, J. Bigler, J.W. Rogers, Y. Zhuang, R.P. Clickner, Trends in blood mercury concentrations and fish consumption among U.S. women of reproductive age, NHANES, 1999–2010, Environ. Res., 133 (2014) 431–438. doi: 10.1016/j.envres.2014.02.001

Joachim Mutter, Is dental amalgam safe for humans? The opinion of the scientific committee of the European Commission, J. Occup. Med. Toxicol., 6 (2011) 2. doi: 10.1186/1745-6673-6-2

G.M. Richardson,  R. Wilson, D. Allard, C. Purtill, S. Douma, J. Gravière, Mercury exposure and risks from dental amalgam in the US population, post-2000. Sci. Total. Environ., 409 (2011) 4257-68. doi: 10.1016/j.scitotenv.2011.06.035

D.R. Laks, Assessment of chronic mercury exposure within the U.S. population, National Health and Nutrition Examination Survey, 1999–2006, Biometals, 22 (2009) 1103–1114. doi: 10.1007/s10534-009-9261-0

L. Barregard, F. Trachtenberg, S. McKinlay, Renal effects of dental amalgam in children: The New England children's amalgam trial, Environ. Health Perspect., 116/3 (2008) 394-399.  doi: 10.1289/ehp.10504

J.E. Dunn, F.L. Trachtenberg, L. Barregard, D. Bellinger, S. McKinlay, Scalp hair and urine mercury content of children in the Northeast United States: the New England Children's Amalgam Trial, Environ. Res., 107 (2008) 79–88. doi: 10.1016/j.envres.2007.08.015

James S. Woods, Michael D. Martin, Brian G. Leroux, Timothy A. DeRouen, Jorge G. Leitão, Mario F. Bernardo, Henrique S. Luis, P. Lynne Simmonds, John V. Kushleika, Ying Huang, The contribution of dental amalgam to urinary mercury excretion in children, Environ. Health Perspect., 115 (2007)  1527–1531. doi:10.1289/ehp.10249

L. Bjorkman, B.F. Lundekvam, T. Laegreid, B.L. Bertelsen, I. Morild, P. Lilleng, B. Lind, B. Palm, M. Vahter, Mercury in human brain, blood, muscle and toenails in relation to exposure: an autopsy study, Environ. Health, 6 (2007) 30. doi: 10.1186/1476-069X-6-30

Gianpaolo Guzzi, Marco Grandi, Cristina Cattaneo, Stefano Calza, Claudio Minoia, Anna Ronchi, Anna Gatti, Gianluca Severi, Dental Amalgam and Mercury Levels in Autopsy Tissues, Am. J. Forensic Med. Pathol., 27 (2006)  42–45. doi: 10.1097/01.paf.0000201177.62921.c8

B.A. Dye, S.E. Schober, C.F. Dillon, R.L. Jones, C. Fryar, M. McDowell, T.H. Sinks, Urinary mercury concentrations associated with dental restorations in adult women aged 16–49 years: United States, 1999–2000, Occup. Environ. Med., 62 (2005) 368–375. doi: 10.1136/oem.2004.016832

J. Leistevuo, T. Leistevuo, H. Helenius, L. Pyy, M. Osterblad, P. Huovinen,  Dental amalgam fillings and the amount of organic mercury in human saliva,  Caries Res, 35 (2001) 163–166. doi: 10.1159/000047450

A. Kingman, T. Albertini, L.J. Brown, Mercury concentrations in urine and whole blood associated with amalgam exposure in a US military population, J. Dent. Res., 77 (1998) 461–471. doi: 10.1177/00220345980770030501

Murray J. Vimy, Debrah E. Hooper, Wayne W. King, Fritz L. Lorscheider, Mercury from maternal “silver” tooth fillings in sheep and human breast milk, Biol.  Trace Elem. Res., 56/2 (1997) 143–152. doi: 10.1007/BF02785388

F.L. Lorscheider, M.J. Vimy, A.O. Summers, Mercury exposure from “silver” tooth fillings: emerging evidence questions a traditional dental paradigm. FASEB J., 9 (1995) 504-508. http://www.fasebj.org/content/9/7/504.long

R.A. Flanders, Mercury in dental amalgam--a public health concern?,
J. Public Health Dent., 52 (1992) 303–311. doi: 10.1111/j.1752-7325.1992.tb02293.x

L.J. Hahn, R. Kloiber, M.J. Vimy, Y. Takahashi, F.L. Lorscheider, Dental "silver" tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis, FASEB J., 3/14 (1989) 2641-2646.

D.W. Eggleston, M. Nylander, Correlation of dental amalgam with mercury in brain tissue, J. Prosthet. Dent., 58 (1987) 704–707. doi: 10.1016/0022-3913(87)90424-0

M. Nylander, L. Friberg, B. Lind, Mercury concentrations in the human brain and kidneys in relation to exposure from dental amalgam fillings, Swed. Dent. J., 11 (1987) 179–187.

M.J. Vimy, F.L. Lorscheider. Intra-oral air mercury released from dental amalgam. J. Dent. Res., 64 (1985) 1069-71. doi: 10.1177/00220345850640080901

D. Brune, D.M. Evje. Man’s mercuy loading from a dental amalgam. Sci. Total Environ., 44/1 (1985) 51-63. doi:10.1016/0048-9697(85)90050-6

U. Heintze, S. Edwardsson, T. Derand, D. Brikhed, Methylation of mercury from dental amalgam and mercuric chloride by oral streptococci in vitro, Scand. J. Dent. Res., 91 (1983) 150–152. doi: 10.1111/j.1600-0722.1983.tb00792.x

Related EVISA Resources

Link Database: All about dental amalgam
Link Database: Toxicity of mercury
Link database: Mercury exposure through the diet

Related Information

ADA American Dental Association: Statement on Dental Amalgam
American Dental Association (ASA): Dental Amalgam: What Others Say
British Dental Association (BDA): Dental amalgam - Fact file
Consumers for Dental Choice: Mercury free dentistry
DAMS, Dental Amalgam Mercury Solutions: Dental Amalgam Fillings
European Commission Scientific Committees on Emerging and Newly Identified Health Risks (SCENIHR) and on Health and Environmental Risks (SCHER): Dental amalgam
EPA: EPA's Roadmap for Mercury 
FDA: About Dental Amalgam Fillings 
GreenFacts: Tooth filling materials: Dental amalgams & alternative materials
International Academy of Oral Medicine and Toxicology: The Scientific Case against Amalgam
International Academy of Oral Medicine and Toxicology: Smooking Teeth
International Academy of Oral Medicine and Toxicology: IAOMT Position Paper Against Dental Mercury Amalgam
International Academy of Oral Medicine and Toxicology: A Comprehensive Review of the Toxic Effects of Mercury in Dental Amalgam Fillings on the Environment and Human Health. available from biovitaal.nl
Kickstarter: “You Put What In My Mouth?”
National Health Federation: The Deadly Dangers of Mercury Contamination
R. Lauer's Amalgamation Information Site (in German)
UNEP: Minamata Convention on Mercury
WHO: Future Use of Materials for Dental Restoration
Wikipedia: Dental amalgam controversy

Related EVISA News

December 29, 2013: A new study finds: Inorganic mercury stays in the brain for years if not decades
December 13, 2013: Most Canadians having dental amalgam in their mouth are exposed to mercury at levels surpassing the reference exposure level (REL)
November 20, 2013: EPA Study: Mercury Levels in Women of Childbearing Age Drop 34 Percent
October 12, 2013: Minamata Convention is adopted
August 6, 2013: Bacterial methylation of mercury not only starting from oxidized mercury
March 22, 2013: Mercury isotope fractionation provides new tool to trace the source of human exposure
January 14, 2013: Mercury Levels in Humans and Fish Around the World Regularly Exceed Health Advisory Levels

last time modified: November 27, 2023


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