Health Problems Caused by Amalgam Dental Fillings: Before and After

Dental amalgam has long been used to repair tooth decay. Its durability and low cost keep it popular, but its elemental mercury content also carries health risks.

Studies continue to examine the possible risks of amalgam fillings, which remain in use worldwide. Research such as the Bergen Amalgam Study explores associations between fillings and particular health complaints. 

Amalgam Fillings

Dental amalgam combines liquid mercury with a metal powder called an alloy, mainly silver, tin and copper. Durable, inexpensive and moisture-resistant, it has been used to repair tooth decay for more than 150 years. 

Dental amalgams release elemental mercury vapor that can be inhaled and absorbed into the bloodstream. Approximately 80% of inhaled vapor is absorbed. Continuous mercury release makes fillings a potential source of chronic mercury toxicity, an important drawback of this inexpensive, durable material. A person with an average amount of amalgam fillings is estimated to be exposed to approximately 5 – 9 μg of mercury daily. 

Elemental mercury vapor exposure may have systemic and local effects, including effects on the peripheral and central nervous systems. Mercury's particular affinity for binding to proteins and amino acids also makes it an important chemical for human health. 

Views differ on the risks of dental amalgam. Health problems thought to be associated with it are nonspecific, complicating research. 

Despite debate over toxicity, some parts of the world have little concern about amalgam, which remains a popular choice.

Adverse Effects Attributed to Dental Amalgam: The Bergen Amalgam Study

Patients whose health problems are thought to be related to amalgam fillings generally share symptoms with patients who have  medically unexplained physical  symptoms  (MUPS). Similar complaints in these two groups allow comparisons over time.

In 2012, the Norwegian Directorate of Health launched an experimental project, the Bergen Amalgam Study, involving patients with subjective health complaints attributed to amalgam. There were three groups: an amalgam cohort (people with dental amalgam), a MUPS cohort (people with medically unexplained physical symptoms) and a healthy cohort. The target population was the amalgam group, whose fillings were all removed and replaced with other restorative materials. The MUPS and healthy cohorts served as comparison groups. 

Participants rated 11 local and 12 general health complaints on numerical scales before treatment and at follow-up after 1 and 5 years.

The study found:

• At 1 year after removal of all amalgam fillings, average symptom severity was lower than baseline for all 23 complaints in the amalgam cohort. Statistically significant changes occurred in specific complaints, with effect sizes ranging from 0.36 to 0.68.
• At 5-year follow-up, symptom intensity remained consistently lower than before amalgam removal.
• No significant change in symptom intensity occurred in the comparison groups.

The researchers concluded that local and general health complaints decreased after removal of all amalgam fillings. Because the study was not blinded, specific and nonspecific treatment effects, such as placebo or other treatment effects, could not be distinguished. 

The study is interesting, particularly for its long follow-up. Unfortunately, its design means the results say little about causality between amalgam fillings and symptoms. 

The study was also consistent with two entirely different explanations:

• Amalgam caused MUPS, so its removal permanently treated the health problems.
• Amalgam did not cause MUPS, but removing this toxic substance was sufficient for MUPS to disappear.

In summary, the study addressed an important gap, but further questions still require research.