The Food and Drug Administration is warning certain individuals to avoid getting “silver” fillings — known as dental amalgams — due to the potential risk of “adverse health effects of mercury exposure.”

The warning, issued as part of dental amalgam guidelines released last month, applies to: 

  • Pregnant and nursing women
  • Developing fetuses and newborns
  • Children under age 6
  • Patients with preexisting neurological conditions
  • Patients with impaired kidney function
  • Individuals with metal allergies to copper, tin, silver or mercury

Dental amalgams are widely used to fill cavities. More than 100 million people have these amalgams, according to the American Dental Association, that are typically made of a mixture of tin, copper and silver and about 50% mercury, by weight. 

Mercury has the potential to leak out into the body and, according to the FDA, may be to blame for a range of health problems. In general, people with multiple dental amalgam fillings tend to have more mercury in their blood, but not at unsafe levels, the FDA noted in a patient advisory

The agency, however, isn’t going as far as banning dental amalgams, noting the “weight of existing evidence” suggests the fillings aren’t harmful to the general population.

Health Issues Linked to Dental Mercury

The FDA is concerned dental amalgams may expose patients to unsafe levels of mercury — although the agency is uncertain what constitutes an acceptable level of mercury gas. Liquid mercury may convert over time into a more dangerous gaseous form, particularly during chewing, the FDA noted. This gaseous form can then convert into many harmful mercury compounds.

The conversion process may explain the negative health outcomes the FDA has recorded related to dental amalgams, including:

  • Mood disorders
  • Sleep difficulties or disturbances
  • Fatigue
  • Memory troubles or disturbances
  • Tremors 
  • Difficulties with coordination
  • Vision changes
  • Changes in hearing
  • Kidney damage

The ADA, however, maintains that dental amalgams have demonstrated a “record of safety.” The ADA cites studies from 1998 onward that have failed to find delta amalgams to be harmful based on existing evidence.

What Should Patients Do?

The FDA advises patients in at-risk groups with amalgam fillings to regularly check in with their dentist, maintain a healthy diet and practice good oral hygiene to preserve the dental amalgam for as long as possible. The FDA doesn't recommend removing existing dental amalgam fillings that are in good condition unless a health care professional deems the removal medically necessary.

At-risk patients who feel uncertain about getting dental amalgams “should discuss treatment options, including the associated benefits and risks of using dental amalgam or an alternative non-mercury filling material” with their dentist, the FDA advises.

Until mercury-based dental amalgams are proven hazardous, the FDA suggests using mercury-based dental amalgams as the longest-lasting option for dental replacements. 

The FDA further recommends that dentists inform themselves of the types of patients who are at-risk and avoid using the term “silver filling” to prevent confusion. They also should follow best practices to avoid metal-on-metal contact with other fillings to prevent incidental exposure to mercury.