Sasha Milbeck, National Center for Health Research
For years, dentists have used fillings to treat cavities or repair cracked and broken teeth. Today, numerous types of dental fillings are available, and teeth can be filled with gold, porcelain, tooth-colored plastic, resin, or silver amalgam. Silver amalgam consists of mercury mixed with silver, tin, zinc, and copper.
When amalgam fillings are placed in or removed from teeth, they release a small amount of mercury vapor. Most people have small amounts of mercury in their bodies, and those who eat more fish typically have higher mercury levels.
Although mercury is a naturally occurring substance found in soil, water, and air, it can be very dangerous. Mercury poisoning can result in psychiatric disorders, gastrointestinal problems, and a type of neurological disorder referred to as “Mad Hatter Disease”. The term “mad as a hatter” described the psychotic or odd behavior caused by mercury poisoning experienced by felt-hat makers in the early 20th century, years before the Mad Hatter was created in Lewis Carroll’s Alice in Wonderland.
Metallic mercury is the pure form of mercury and can release vapors at room temperature or higher. Breathing in large amounts of metallic mercury vapor can cause poisoning. The mercury enters your bloodstream from your lungs, and can travel throughout your body, causing the most damage to your brain and kidneys. Mercury can also pass through the placenta into fetal circulation and can be found in the milk of breast-feeding women with mercury in their bloodstream.
Since the 1990s, patients with amalgam fillings have reported health problems that they believe are caused by their exposure to mercury, but the FDA has downplayed the risks. Meanwhile, The International Academy of Oral Medicine and Toxicology (IAOMT), a nonprofit network of dentists, health professionals, and scientists who research the bio-compatibility of dental products, including the risks of mercury fillings, have expressed concerns because dental products are not usually required to prove they are safe for long-term use.
The amalgam is known to release small amounts of mercury over time, and while low levels of mercury vapor is not known to be harmful for most people, the long-term health risks of mercury inhalation are not clear. And, even if low levels of mercury are not obviously harmful for most people, they might be for some groups.
The agency is urging for the following groups to avoid getting amalgam fillings whenever possible: 
- 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 preexisting neurological disease such as multiple sclerosis, Alzheimer’s disease or Parkinson’s disease
- People with impaired kidney function
- People with known heightened sensitivity (allergy) to mercury or other components of dental amalgam.
Since amalgam mercury vapor release is highest during placement and removal of a filling, the FDA is not recommending anyone to remove existing amalgam fillings unless it is considered medically necessary by a dentist. Removing the filling can lead to more mercury vapor being released and result in additional health risks.
There are safer alternatives to amalgam. The two most commonly used dental fillings are composite resin fillings and glass ionomer cement fillings. Composite resin fillings are made of tooth-colored plastic and powdered glass. The advantages of composite resin fillings are that they blend in easily with other teeth, have high strength, and require less removal of healthy bone tissue for placement. However, they are more expensive, and may need more frequent replacement than amalgam fillings.
Glass ionomer fillings are made of cement and act as cavity sealants. The cements have a glass component that releases fluoride over time. The fluoride helps protect your teeth and prevent future cavities. However, fluoride can also be toxic, with common side effects including gastrointestinal problems. While glass ionomers have many benefits, they lack the strength and durability of composite and amalgam fillings. They are mainly used for temporary and small restorations.
If you are on the FDA’s list of “high-risk individuals,” read up on your options before talking to your dentist about those options. Due to the lack of research and low FDA standards for dental devices, dentists may have limited information about amalgam fillings and these newer alternatives, and there is a natural tendency for health professionals to assume that the products that FDA allows on the market are safe. There is not enough research to determine long-term dangers of mercury vapor inhalation, and only you can decide if the potential risks are ones you are willing to take.
To find out more about mercury and where it can be found, click here.
1. APA Dictionary of Psychology. (n.d.). Retrieved from https://dictionary.apa.org/mad-hatters-disease
2. “Toxic Substances Portal – Mercury.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.atsdr.cdc.gov/PHS/PHS.asp?id=112&tid=24.
3. “Mercury in Dental Amalgam.” EPA, Environmental Protection Agency, 10 Jan. 2020, www.epa.gov/mercury/mercury-dental-amalgam#amalgamsafety.
4. Commissioner, Office of the. “FDA Issues Recommendations for Certain High-Risk Groups Regarding Mercury-Containing Dental Amalgam.” U.S. Food and Drug Administration, FDA, www.fda.gov/news-events/press-announcements/fda-issues-recommendations-certain-high-risk-groups-regarding-mercury-containing-dental-amalgam.
5. Center for Devices and Radiological Health. “Alternatives to Dental Amalgam.” U.S. Food and Drug Administration, FDA, www.fda.gov/medical-devices/dental-amalgam/alternatives-dental-amalgam.
6. Aoun, Antoine, et al. “The Fluoride Debate: The Pros and Cons of Fluoridation.” Preventive Nutrition and Food Science, vol. 23, no. 3, 2018, pp. 171–180., doi:10.3746/pnf.2018.23.3.171.