For many years, amalgam has been one of the materials used for dental restorations to fill cavities in posterior teeth. However, there are environmental and health concerns about exposure to mercury, one of the components of dental amalgams.1 These concerns are outlined by the Minamata Convention, a global treaty to protect against the adverse effects of mercury, which has 128 worldwide signatories.2 Sweden, Norway, and Germany have banned the use of amalgam for restorations, but other countries, such as the U.S., are following the phasedown approach as outlined in the Convention.3 The U.S. Food and Drug Administration (FDA) recommends that high-risk populations avoid amalgam when possible but maintains that amalgam is safe for other populations.4 High risk populations include patients ages six or younger, patients who are pregnant, breastfeeding, or trying to become pregnant, and patients with certain sensitivities to metal or certain pre-existing conditions. However, since amalgam restorations have better longevity than restorations using other materials, amalgam might preferentially be used in patient populations where future dental care follow-up is less assured.5
We sought to understand whether the proportion of dental fillings that used amalgam has changed over time and whether those rates differ across populations. We studied 1,346,918 posterior tooth filling encounters in the U.S. from 2017 to 2022 and assessed the rate of amalgam fillings compared to resin or composite fillings each year. We found that the rate of amalgam fillings has decreased from 21.5% of fillings in 2017 to 5.7% of fillings in 2022, as shown in Figure 1.
When comparing the rates of amalgam fillings across social vulnerability index quartiles, we found that those most socially vulnerable were most likely to have an amalgam filling, as shown in Figure 2. The rate of amalgam restorations in that group has decreased 58% since 2017, which compares to a 73% decrease in the overall rate of amalgam fillings.
Analysis by insurer and rural and urban classification showed similar declines in amalgam use across commercial and government payers as well as rural and urban areas. The proportion of amalgam fillings for patients with Medicaid has decreased 70% since 2017, with less than 7% of fillings using amalgam in 2022.
Additionally, the proportion of fillings that used amalgam decreased across all age groups. Patients under age six, who are considered an at-risk group for mercury exposure per the FDA, had the least decrease in rate over the five-year period and were most likely to receive an amalgam filling compared to other age groups in 2022, as shown in Figure 3. However, children under age six accounted for less than 2% of all posterior tooth filling encounters in 2022, which supports that amalgam fillings are relatively infrequent in this age group.
Patients aged 15-48 account for the majority of posterior tooth fillings and thus represent the majority of patients with amalgam fillings in the general population. This age group also had the greatest decline over time in the proportion of fillings that used amalgam, as shown in Figure 3. This age group is most likely to include patients who are pregnant, breastfeeding, or attempting to become pregnant, indicating that mercury exposure may be decreasing for this group that the FDA considers high-risk.
This analysis demonstrates that the U.S. appears to have made significant progress in the phasedown in amalgam use. Though there appear to still be some apparent demographic differences, amalgam use in all populations across the U.S. has decreased dramatically.
