FDA's 2020 amalgam recommendations: the seven groups to steer toward non-mercury fillings, and the fillings it says to leave alone

What it says#

On September 24, 2020 the FDA issued a safety communication, with a statement from the director of its Center for Devices and Radiological Health, recommending that non-mercury restorations such as composite resins and glass ionomer cements be used, when possible and appropriate, in people who may be at higher risk from mercury exposure. It named seven groups: 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; people with impaired kidney function; and people with known heightened sensitivity or allergy to mercury or other components of dental amalgam. The statement gives multiple sclerosis, Alzheimer's disease and Parkinson's disease as examples of the neurological conditions it has in mind.

The reasoning is stated as uncertainty rather than finding. After more than 20 years of literature review, adverse event monitoring and public meetings, including a Dental Products Panel in December 2010 and an Immunology Devices Panel in November 2019, the FDA says the key open questions are the acceptable reference exposure levels for mercury vapor, the potential for mercury from amalgam to convert to other mercury compounds in the body, and whether the degree of accumulation results in adverse outcomes. Elemental mercury is known to cause harm at high exposures, in people with a reduced ability to clear it, and in people who are sensitive to it, and the communication says little to no information exists about the effect of amalgam exposure on the listed groups. So the recommendation steers those groups away from amalgam while the general-population conclusion stands: the majority of evidence shows exposure to mercury from dental amalgam does not lead to negative health effects.

Two things the FDA specifically did not do. It did not ban amalgam: it says the available evidence does not support a complete ban, that amalgam's longevity is better than that of alternatives, especially for large restorations, and that a ban could mean deferred or no treatment in communities where alternatives are scarce. And it does not recommend that anyone, in the listed groups or out of them, have intact amalgam fillings in good condition removed or replaced unless a health care professional considers it medically necessary, for example a documented hypersensitivity to the material. Removing an intact filling produces a temporary increase in mercury vapor exposure and costs healthy tooth structure; the FDA's view is that the removal carries more risk than the filling.

The communication carries a list for dentists. Review the patient recommendations and discuss the risks and benefits of amalgam and the alternatives so patients can make informed choices, sharing the FDA's patient information before consent. Avoid the term "silver filling," which the FDA says misstates what the material is. When using amalgam, use encapsulated amalgam and avoid bulk elemental mercury to limit occupational exposure, avoid placing amalgam in direct contact with other fixed or removable metallic devices in the mouth, follow mercury hygiene best practices, and use an amalgam separator to keep amalgam waste out of the environment.

On the material itself, the FDA's current dental amalgam page says amalgam is approximately half elemental mercury by weight, mixed with a powdered alloy of silver, tin and copper; that it releases low levels of mercury vapor, highest during placement and removal and temporarily higher with chewing, brushing and grinding; that the vapor is absorbed mainly through the lungs and that small amounts can collect in tissues including the kidneys and brain, and in a pregnant woman in the blood reaching the fetus; and that the concentrations released are low compared with those associated with clinical signs of toxicity. Its benefits, in the FDA's words: strong and long-lasting, useful in patients at high risk of decay, for large preparations and where moisture makes bonding difficult, the least expensive filling material, and in use for more than 150 years. Resin composites are color-matched, contain no heavy metals and usually require less tooth removal; their disadvantages include shrinkage that can open marginal gaps, hypersensitivity to unreacted methacrylate components, limits on placement and longevity, and more time and cost.

Who it applies to#

Any patient in one of the seven groups who needs a restoration, and the dentist treating them. The question is asked at the medical history: pregnancy, plans for pregnancy, nursing, age under six, a neurological diagnosis, kidney disease, or a known reaction to mercury, silver, copper or tin. For those patients the FDA's recommendation is a non-mercury material where the tooth's structure and location allow it and where there is no allergy to the alternative; the FDA's page adds that a patient allergic or sensitive to any of the metals should not get an amalgam filling at all.

For everyone else, the FDA's position is that amalgam is one acceptable option among several and that the choice belongs to the patient and the dentist after the risks and benefits are discussed. The recommendations are advice to patients and clinicians, not a device restriction. Dental amalgam, dental mercury and amalgam alloy have been class II devices under a single regulation since the 2009 rule, which took effect November 2, 2009, with a special controls guidance document as the control; the 2020 action changed the advice, not the classification.

What changed#

The 2009 rule settled the regulatory question, classifying amalgam as class II with special controls. Its preamble had already singled out developing fetuses, breastfed infants and children under six as potentially sensitive subpopulations, and concluded that the limited human data did not demonstrate an association between the mercury in amalgam and adverse reproductive outcomes such as low birth weight or miscarriage. A decade of panels and reviews followed. In September 2020 the FDA moved from a general statement about safety to a named list of groups and a recommendation to use other materials for them, framed around the uncertainties in the evidence for those groups rather than any new finding of harm. The 2020 documents also introduced the explicit instruction not to remove intact fillings for prevention, the plain statement that a ban is not supported, and the practical list for dentists, including the retirement of "silver filling."

For the office, the change is in the conversation. Before 2020 a dentist could describe amalgam as safe and leave it there; now the FDA itself says a pregnant patient, a nursing mother or a five-year-old should get something else where appropriate, and the patient who has read that online is right. The FDA's page says it will update the public if significant new information becomes available; this entry will follow.

Where the source is#

The September 24, 2020 safety communication and the CDRH director's statement were published on fda.gov, but fda.gov no longer serves either page at its original address; the links here open Internet Archive copies of both as they appeared in 2021. The FDA's current dental amalgam page carries the same seven groups, the same recommendation for non-mercury materials, the instruction not to remove intact fillings and the risk-and-benefit description quoted above, and links a graphics page for patients and an appendix summarizing the classification history. The 2009 classification rule is on govinfo at 74 FR 38686. The EPA's amalgam page covers the environmental side. All of it is public and free to copy.