By David Kennedy, DDS, MIAOMT, Amanda Just, MS, and Jack Kall, DMD, MIAOMT

One of the first reports documenting the dental amalgam controversy and the dangers of using mercury in dentistry dates back to 1841. At that time, dental amalgam mercury fillings had just been brought to the United States, and a committee of the American Society of Dental Surgeons, which was the first U.S. dental group, warned that amalgam was not safe.^[1] The same group made its members pledge not to use mercury because of its known toxicity,^[2] and meanwhile, the New York Dental Society expelled members or forced them to resign if they would not pledge to be amalgam-free.^[3]

This marked the beginning of a time period referred to as the “Amalgam War” due to the many debates and arguments that ensued over dental mercury. Three notable examples of evidence against amalgam from this time period include 1) a report from Dr. Amos Westcott warning that dental mercury could cause issues with the stomach and issues with gold fillings; 2) a case study published in the American Dental Review of a patient whose health improved after amalgam removal, and 3) the recommendation from Dr. Elisha Townsend, formerly a renowned proponent of amalgam, that the use of dental mercury should be avoided.^[4]

By 1856, the American Society of Dental Surgeons had disbanded because of the Amalgam War, and in 1859, the American Dental Association (ADA), a group who supported the use of amalgam, became the nation’s new dental society. However, concerns about dental amalgam continued. A July 1873 article in the Chicago Medical Journal warned of the “poisoning of thousands of people all over the world from corrosive sublimate generated in the mouth from amalgam plugs in the teeth; neither cholera, smallpox, or any malarious disease [is] doing more injury in the world than this poison.”^[5]

Meanwhile, in 1867, the St. Louis Odontological Society recognized health risks from amalgam fillings and voted not to use them,^[6] and in 1878, the Canada Lancet noted that the use of dental mercury “is radically wrong, and should not be ventured upon if the patient’s welfare is to be considered.”^[7] Additionally, based on a series of experiments, Dr. E. Talbot warned that “all amalgams will send off the vapor of mercury.”^[8] His work was published in the Ohio State Journal of Dental Science in 1882.

Equally important was Dr. J. Tuthill’s research entitled “Mercurial necrosis resulting from amalgam fillings,” which was published in The Brooklyn Medical Journal in 1898. Dr. Tuthill read his work, including a number of case studies, before a medical society, and in it he passionately stated:

In presenting this subject to the society for consideration, I want to show that by the use of amalgam in filling teeth there is a possibility of mercurial poisoning, which seriously affects the nerve centers, impairs locomotion by heaviness of limb and stiffness of joint, gives rise to obstinate diseases of the skin, and makes a mental wreck of its victim, whose imaginations and hallucinations are more than my pen can describe.^[9]

Dr. Tuthill and others continued to fight the use of dental mercury, and the dental amalgam controversy continued into the twentieth century, when scientific progress allowed for many more studies to validate that mercury remains a toxic threat when it is amalgamized and placed into teeth.

In one of the first studies to measure the amount of dental mercury vapor emitted from fillings, German chemist Alfred Stock shared evidence that mercury vapor is released from amalgam fillings in amounts significant enough to produce adverse health impacts. Stock himself suffered mercury poisoning, and his research appeared in a series of papers published in German scientific journals. Based on his data and experiences, in The Dangerousness of Mercury Vapor, Dr. Stock declared in 1926 that the introduction of mercury in amalgam fillings was “a nasty sin against humanity.”^[10]

Because of new technology and scientific advancements, research conducted in more recent decades has been able to more accurately examine issues related to dental amalgam mercury. Moreover, the increase in the number of published research articles has resulted in the development of science designed to evaluate specific risks related to mercury exposure from dental amalgam. Some of the areas of research addressed in recent scientific literature include

• dentist and dental staff occupational exposure to mercury^{[11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41]}
• mercury vapor releases from amalgam fillings^{[42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63]}
• mercury vapor releases increased by the number of fillings, chewing, teeth-grinding, brushing, dental treatments, and hot liquids ^{[64] [65] [66] [67] [68] [69] [70] [71] [72] [73]}
• genetic traits impacting response to dental mercury^{[74] [75] [76] [77] [78] [79] [80]}
• fetal and infant exposure to mercury via maternal dental mercury amalgam^{[81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96]}
• mercury excreted in breast milk of mothers with dental mercury amalgam fillings, increasing with the number of amalgam fillings^{[97] [98] [99] [100]}
• dangers of dental mercury use in children^{[101] [102] [103] [104] [105] [106] [107] [108] [109] [110]}
• allergy/hypersensitivity to dental mercury^{[111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128]}
• dental amalgam mercury’s impact on patients with autoimmune disorders/immunodeficiency^{[129] [130] [131] [132] [133] [134] [135]}

• dental amalgam mercury’s impact on patients with kidney disease^{[136] [137] [138] [139] [140]}
• dental amalgam mercury’s impact on patients with multiple sclerosis^{[141] [142] [143] [144]}
• dental amalgam mercury’s impact on patients with oral lichenoid reaction^{[145] [146] [147] [148] [149] [150] [151]}and oral lichen planus^{[152] [153] [154]}

Awareness of occupational hazards, environmental dangers, and patient risks as a result of dental mercury usage has grown with new science. In fact, by the turn of the millennium, the world slowly began to take action against dental mercury, following the exact same delayed course that occurred with asbestos and lead.

Norway banned dental amalgam in 2008,^[155] Sweden banned the use of dental amalgam for almost all purposes in 2009,^[156] and Denmark, Estonia, Finland, and Italy use it for less than 5% of tooth restorations.^[157] Japan and Switzerland have also restricted or almost banned dental amalgam.^[158] France has recommended that alternative mercury-free dental materials be used for pregnant women, and Austria, Canada, Finland, and Germany have purposely reduced the use of dental amalgam fillings for pregnant women, children, and/or in patients with kidney problems.^[159]

In December of 2016, three EU institutions (the European Parliament, the European Commission and the Council of the European Union) reached a provisional agreement to ban dental amalgam fillings for children under 15 and pregnant and breastfeeding women as of July 1, 2018, and to consider banning dental amalgam completely by 2030.^{[160] [161]}

The United Nations Environment Programme’s Intercessional Negotiating Committee agreed upon the text of a global, legally-binding mercury treaty in 2013, and over 100 nations have since signed the “Minamata Convention on Mercury.” The United States was the first country to give its support for ratification of the international agreement, which entered into force in 2017. Annex A, Part II, includes the following initiatives with regards to dental mercury amalgam:^[162]

1. Setting national objectives aiming at dental caries prevention and health promotion, thereby minimizing the need for dental restoration;
2. Setting national objectives aiming at minimizing its use;
3. Promoting the use of cost-effective and clinically effective mercury-free alternatives for dental restoration;
4. Promoting research and development of quality mercury-free materials for dental restoration;
5. Encouraging representative professional organizations and dental schools to educate and train dental professionals and students on the use of mercury-free dental restoration alternatives and on promoting best management practices;
6. Discouraging insurance policies and programmes that favour dental amalgam use over mercury-free dental restoration;
7. Encouraging insurance policies and programmes that favour the use of quality alternatives to dental amalgam for dental restoration;
8. Restricting the use of dental amalgam to its encapsulated form;
9. Promoting the use of best environmental practices in dental facilities to reduce releases of mercury and mercury compounds to water and land.^[163]

After many years of inaction, the U.S. Food and Drug Administration (FDA) finally updated its recommendations in 2020 by warning certain high-risk groups to “avoid getting dental amalgam whenever possible and appropriate.” The FDA goes on to specify that the “groups that may be at a greater risk for potential harmful health effects include:

• Pregnant women and their developing fetuses;
• Women who are planning to become pregnant;
• Nursing women and their newborns and infants;
• Children, especially those younger than six years of age;
• People with pre-existing neurological disease such as multiple sclerosis, Alzheimer’s disease or Parkinson’s disease
• People with impaired kidney function; and
• People with known heightened sensitivity (allergy) to mercury or other components of dental amalgam.”[164]

This is definitely a step in the right direction. However, it should be acknowledged that for many years, the FDA had publicly stated that it considered dental amalgam fillings safe for adults and children ages 6 and above.[165] Due in part to concerns about this lack of protection, the IAOMT had filed a lawsuit in 2014 against the FDA over its classification of dental mercury amalgam at that time.[166] As part of the case, the IAOMT secured an internal document from the FDA that had proposed restricting dental mercury amalgam use in pregnant and nursing women and children under the age of six, as well as individuals with mercury allergies and pre-existing kidney or neurological disease.[167] Yet, allegedly for administrative or political reasons, the FDA communication (dated January 2012) was never released to the public.

Recently, the U.S. Environmental Protection Agency (EPA) utilized measures in the Clean Water Act to develop standards for dental offices/clinics to use amalgam separators so that dental mercury is not flushed down the drain and into the environment.^[167] These standards went into effect on July 14, 2017, and the EPA has estimated that it could reduce the discharge of mercury by 5.1 tons annually.

The IAOMT has been working to educate dental and medical professionals, policy-makers, and the public about the risks of dental mercury since 1984. While the IAOMT applauds the actions that have been taken against dental mercury over the past two decades, the group warns that it is essential to remember that it is still being used in many countries, and even if the day should come that dental mercury is banned worldwide, it is already in the mouths of millions of patients. For this reason, in addition to encouraging the end of dental mercury, the IAOMT also encourages the use of the Safe Mercury Amalgam Removal Technique (SMART) when amalgam fillings are removed. SMART was developed to mitigate mercury exposures that can occur when the fillings are taken out of people’s mouths, which often occurs due to device failure, hypersensitivity, and/or patient preference.

Meanwhile, some will ignore the warnings and continue to debate the use of amalgam, which they have been doing for over a century. Yet, science will continue to prove that using a toxic material in people’s teeth can have serious health consequences. A famous quote from philosopher Arthur Schopenhauer offers an interesting analogy as to why it is taking so long to end the use of dental mercury: “All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.”

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