Metal fillings, also called dental amalgam, are not harmful for most people. They do contain about 50% mercury mixed with silver, tin, and copper, which understandably raises concern. But the mercury in a placed filling is locked into a stable alloy, and the amount that escapes during daily life is extremely small. Both the FDA and the American Dental Association maintain that amalgam is safe for the general population, though certain groups should avoid it.
What’s Actually in a Metal Filling
Dental amalgam is roughly half mercury by weight, combined with silver, tin, copper, and sometimes zinc. When these metals are mixed together, they form a hard, stable alloy. The mercury doesn’t sit in its liquid form inside your tooth. It’s chemically bound to the other metals, which is why a filling that’s been in your mouth for 20 years doesn’t behave like a pool of loose mercury.
That said, the alloy isn’t perfectly inert. Small amounts of mercury vapor do release from the surface, especially when you chew, grind your teeth, or brush. This is the core of the safety debate.
How Much Mercury You’re Actually Exposed To
Laboratory studies simulating chewing and brushing found that a single amalgam filling releases about 0.03 micrograms of mercury per day under steady conditions. To put that in perspective, the occupational safety threshold for mercury exposure in the United States is over 82 micrograms per day. Even someone with a mouth full of amalgam fillings stays far below that limit during normal use.
You also absorb mercury from food (especially fish), air, and water. The daily dose from fillings is a fraction of what most people take in from dietary sources alone. This is why large-scale reviews keep reaching the same conclusion: the mercury released by fillings doesn’t produce measurable health effects in the general population.
What the Research Says About Health Risks
The most persistent worry is that low-level mercury exposure from fillings might quietly damage the brain or kidneys over decades. Researchers have looked at this carefully. A systematic review and meta-analysis pooling data from 859 patients, including children followed for five years, found no evidence that amalgam fillings caused kidney damage compared to composite resin fillings. The results weren’t even close to statistical significance.
Links to Alzheimer’s disease and Parkinson’s disease have been proposed in observational studies, but the results are mixed and inconsistent. No meta-analysis has confirmed a causal connection. The American Dental Association notes that literature reviews by national and international health agencies continue to agree that amalgam is safe and effective.
Who Should Avoid Amalgam
The FDA does identify specific groups who may face higher risk from mercury exposure and recommends they choose alternatives when possible:
- Pregnant women and women planning to become pregnant
- Nursing mothers and their newborns
- Children under six
- People with kidney impairment
- People with neurological conditions
- Anyone with a known allergy to mercury, silver, copper, or tin
If you fall into one of these categories, the FDA strongly encourages non-amalgam options like composite resin or glass ionomer cement, provided your dentist considers them appropriate for the tooth in question.
Why Dentists Still Use Them
Amalgam fillings last significantly longer than the alternatives. A systematic review of longevity data found that amalgam restorations have a median survival time exceeding 16 years, compared to about 11 years for composite resin. That five-plus-year gap matters, especially for large fillings in molars that absorb heavy chewing forces.
Amalgam is also more forgiving to place. It’s less sensitive to moisture during the procedure, which makes it more reliable in difficult-to-reach areas of the mouth. Composite fillings require a completely dry environment and more precise technique, and they’re more expensive. For patients without dental insurance, or in clinical settings with limited resources, amalgam remains the most practical option for back teeth. This is why the ADA’s current position is that amalgam should stay available until a better alternative emerges.
The Global Trend Away From Amalgam
Despite its safety record, amalgam is being phased out in parts of the world, largely for environmental reasons rather than patient health concerns. The European Union banned dental amalgam starting in 2025, with member states required to ensure insurance coverage for mercury-free alternatives. Under post-Brexit rules, Northern Ireland follows the EU timeline, while the rest of the UK has no formal ban.
In the United States, the EPA requires dental offices that place or remove amalgam to install amalgam separators, which capture mercury waste before it enters the sewer system. Mercury from dental offices was a meaningful source of water contamination before these rules took effect in 2017. The shift away from amalgam globally is driven more by this environmental footprint than by direct risk to patients.
Should You Have Existing Fillings Removed
If your metal fillings are intact and you’re not in a high-risk group, there’s no medical reason to have them replaced. In fact, removing amalgam generates significantly more mercury vapor than leaving it alone. The drilling process heats and fragments the filling, releasing a burst of mercury that temporarily exceeds what you’d absorb from years of normal use.
If you do want them removed, or if a filling is cracked and needs replacement, look for a dentist who follows protective protocols during removal. These typically include placing a rubber dam to isolate the tooth, using high-volume suction near your mouth, sectioning the filling into large chunks rather than grinding it down, irrigating with plenty of water to reduce heat, and ensuring proper air filtration in the room. Some dentists follow a formalized protocol called SMART (Safe Mercury Amalgam Removal Technique), which adds measures like respiratory-grade masks for the dental team, protective gowns for the patient, and a charcoal rinse before and after the procedure.
Replacing amalgam with composite resin is straightforward, but keep in mind that the new filling will likely have a shorter lifespan and may need to be redone sooner. For a small, symptom-free filling in a back molar, the safest option is often to simply leave it where it is.