Does your smile include a flash of silver? While the internet abounds with rumors about the dangers of mercury in metal fillings (aka dental amalgam, the clinical term), you can close those browser tabs: Your fillings are not going to harm you.
Dental amalgam fillings are often referred to as silver fillings because of their color, but they’re actually a combination of metals composed of a powdered alloy with zinc, tin, silver and copper mixed with liquid mercury.
Mercury can be harmful in high dosages — mercury poisoning may cause neurological issues such as muscle weakness and loss of peripheral vision. We all absorb very small amounts of mercury through air, water and consumption of mercury-tainted seafood, but dangerous levels of exposure are extremely rare. Research by the Centers for Disease Control and Prevention (CDC) has found that most people in the United States have mercury levels far below the threshold for concern.
The mercury used in amalgam fillings is called elemental mercury, which releases a vapor that can be absorbed through the lungs. The biggest risk of mercury exposure from dental amalgam occurs while the filling is being placed or removed, so dentists take extra protective measures during those procedures.
“There’s a protocol for how to minimize exposure during placement — for instance, using a rubber dam,” says Dr. Rosalyn Sulyanto, DMD, an assistant professor at Harvard School of Dental Medicine and a pediatric dentist at Boston Children’s Hospital. “Once the amalgam has set, there’s less mercury released, and that’s far below the level that’s considered risky.”
That’s also why experts don’t recommend removing your existing dental amalgam fillings.
“If patients already have the amalgam placed, there’s going to be more exposure from removing the amalgam than there would be from just leaving it alone,” Sulyanto says.
Overall, the benefits of dental amalgam outweigh the risks for many patients: It’s durable, long lasting and often more cost effective than alternative fillings like tooth-colored composite resins and glass ionomers. It also provides good moisture control, which helps to protect the remaining tooth against bacterial growth, especially in high-saliva areas like the back of the mouth or close to the gum line.
“It’s been around for over 150 years, and it does have some advantages,” Sulyanto says.
Studies by the Food & Drug Administration, the Environmental Protection Agency and a number of scholars have also confirmed that the level of mercury exposure from amalgam fillings is far below the threshold of concern for healthy populations. However, the FDA does warn that some high-risk groups could be more susceptible to adverse effects from the mercury in dental amalgam, including pregnant or nursing women and people with pre-existing neurological disease, impaired kidney function, or metal allergies, along with children younger than six.
Despite the benefits of metal fillings, the use of dental amalgam is declining globally in favor of tooth-colored resins and glass ionomers, both for their cosmetic appeal and because they require removing less of the healthy tooth tissue.
“In dentistry, we are moving away from the ‘drill-and-fill’ approach and doing more minimally invasive treatment,” Sulyanto says. “We can do that with composites and glass ionomers more than we can with amalgams.”
Some dental offices have discontinued use of dental amalgam altogether, but Sulyanto thinks there’s still a place for the time-tested material.
“At the end of the day, it’s just a discussion between the patient and their dentist about risks and benefits,” she says. “But amalgam is still a usable material, which I’m glad about.”