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ADA study finds about half of restored teeth in US contain amalgam

Research can be used to assess future caries prevention, amalgam reduction efforts

June 22, 2021

By Mary Beth Versaci

Slightly more than half of restored teeth in the U.S. contained amalgam as of 2015 and 2016, according to a study from the American Dental Association Science & Research Institute.

Published online in May by the Journal of Public Health Dentistry, "Dental Amalgam Restorations in Nationally Representative Sample of U.S. Population Aged ≥15 Years: NHANES 2011-2016" analyzed three two-year cycles of National Health and Nutrition Examination Survey data from U.S. participants who were at least 15 years old and underwent an oral health examination. The percent of the U.S. population with at least one restoration of any material was relatively constant throughout 2011-16, ranging from 64.4% to 67.1%. In the 2015-16 cycle, the data included the type of material used for restorations, indicating 51.5% of restored teeth contained amalgam — the first-ever estimate of amalgam-restored teeth in the U.S.

"These data serve as a baseline for future analysis and evaluation of the use of dental amalgam in the U.S. and will facilitate monitoring compliance with the Minamata Convention," said Cameron Estrich, Ph.D., health research analyst with the ADA Science & Research Institute and one of the paper's authors.

The other authors include Marcelo Araujo, D.D.S., Ph.D., CEO of the ADA Science & Research Institute and chief science officer of the ADA, and Ruth Lipman, Ph.D., director of scientific information for the ADA Science & Research Institute.

In 2013, the U.S. joined the Minamata Convention on Mercury, a global agreement that aims to limit mercury emissions. The convention calls for a phasedown of dental amalgam through increased prevention efforts, research into viable alternatives and increased use of other restorative materials.

A first step in phasing down the use of dental amalgam is to establish the current prevalence of amalgam as a measure against which to evaluate the success of strategies taken to reduce its use. Previous estimates regarding the frequency of amalgam use in the U.S. have been limited because studies relied on administrative records or data from third-party payers that may not have been representative of the population.

The ADASRI study confirmed that more molars and premolars were restored than other types of teeth and found amalgam was used more frequently than other materials in these restorations. Because of this, prioritizing research and development of materials particularly suited to meet the structure and force requirements to restore surfaces in these teeth has the greatest potential to reduce the use of amalgam, according to the study.

Caries risk is reported to be the predominant factor in choosing to use amalgam, so focusing on caries management efforts — first and foremost, prevention — could reduce amalgam use as well, the study stated.

"In terms of treatment, our study presents evidence that there are still a lot of amalgam restorations in patients' mouths and any future replacement will have an impact on their dentition. Preventing secondary caries lesions should be prioritized over replacing amalgam restorations for aesthetic reasons," Dr. Araujo said. "In terms of policy, this information has great value to affirm the timing proposed by the U.S. delegation on a phasedown of amalgam compared with the phaseout approach chosen by some European countries and Japan."

In addition to tooth type, the study found the presence of amalgam in restorations varied by the age and race/ethnicity of the survey participants but not by their sex.

Among those with restored teeth, the mean number of teeth with amalgam restorations increased with age from 4.71 among 15- to 24-year-olds to 7.03 among those 75 years old or older. Non‐Hispanic white participants with restored teeth had the highest mean of teeth with amalgam restorations at 5.94 while non‐Hispanic Black participants had the lowest at 5.08.

The interpretation of these observed demographic differences is limited by a lack of data evaluating participants' access to dental care over time, differences in their personal preferences regarding dental care and specifics on restoration materials. The differences may, in part, reflect systemic health care inequities, according to the study. Differences that appear to be related to age may be exacerbated by age-related tooth loss and access-to-care issues and may reflect when new restorative materials were approved for use.

The ADA is supporting the FDI World Dental Federation and International Association for Dental Research as they prepare for the fourth meeting of the Conference of the Parties to the Minamata Convention on Mercury, which is scheduled for November.

For more information on amalgam from the ADA, visit ADA.org/amalgam and the Center for Professional Success.