Silvery Whites: The Potential Dangers of Dental Amalgam

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Cavities are exceedingly common, with 90% of the U.S. population having one over the course of their life. When treating cavities, the affected area is drilled out to prevent the decay from spreading. But that hole, if unfilled, leaves the patient more susceptible to future decay, as the hole is thoroughly uncleanable through conventional means. That is why dentists fill the holes, a practice that dates to the Neolithic era. The most common filling in the U.S. has, in recent history, been dental amalgam.

Dental Amalgam

While it is the most common, dental amalgam is not the sole material used to fill the holes left behind when drilling away tooth decay. Colloquially, dental amalgam is referred to as silver fillings due to the silver hue taken on once hardened. According to the U.S. Food and Drug Administration (FDA), dental amalgam is a composite of liquid mercury and a powdered alloy containing silver, tin and copper. By weight, standard dental amalgam is 50% mercury. This staggering volume of mercury seems concerning, but research seems inconclusive on whether it truly is.

Mercury Exposure and Poisoning

Earlier research suggested that only sizeable amounts of mercury caused the feared adverse health effects. Which truly are terrible and deeply impact the total health of the body. Mercury poisoning comes in all different forms, depending on the composite mercury structure a patient is exposed to. All mercury is toxic to the body, but its versions and alloys can mitigate or exacerbate reactions and effects. Mercury exposure in adults can be deadly, as it impairs the digestive, nervous, respiratory, urinary, circulatory and immune systems, leading to organ failure and even death. These symptoms are even more prevalent in children, especially with the presentation of the neurological impact of mercury poisoning. Mercury is not filtered through the placenta and can cause lasting neurological and physical disabilities, including impaired speech, deformed limbs and affected cognitive function.

How Much Is Too Much?

Recent scholarship seems to suggest that even smaller sustained exposure to mercury can affect health. This makes the University of Georgia’s study tracking blood mercury levels alongside dental amalgam filling especially concerning. Their results found that people with eight or more amalgam fillings had 150% mercury in their blood. To put that into perspective of how common this problem could be, as of 2016 the average American citizen has three amalgam fillings, while 25% of the US population has 11 or more. The mercury discovered in the blood was methylmercury, the element’s most toxic form. Methyl mercury is not present within dental amalgam itself though, as it is made with pure elemental mercury. A leading scholar on the study, Xiaozhong Yu, claims this suggests that mercury methylation occurs in the body. As mercury is imbibed through consumption and inhalation, the gut microbiota (or microbiome) processes the element, rereleasing it into a more deadly state.

Amalgam Fillings

Considering recent studies that suggest even small doses of methylmercury to be toxic, these statistics are unsettling. Yet there is still little research done on the actual long-term health effects of this continued minimal mercury exposure. Thankfully, there is evidence suggesting that the composition of the mercury on the surface of the filling, meaning the part exposed to and affecting the human body, changes through continual exposure to beta-mercuric sulfide or metacinnabar. This compound is seemingly non-toxic to the human body. Amalgam fittings also lose up to 95% of their mercury saturation over time, lessening the potential extended effects of a lifetime of fillings.

Who Should Avoid Dental Amalgam?

Despite the inconclusive nature of the research, there is still worry over the mercury dental amalgams’ effect on human health, despite the compound’s continued use. Its popularity stems from its inexpensive price tag and its extended durability. Historically, it has been difficult to develop a material as durable as the mineral-rich human enamel. In spite of these concerns, the FDA maintains to this day that there is not enough evidence to suggest filling a cavity with dental amalgam causes significant health problems for the general public. They do however acknowledge it as potentially harmful, advising pregnant women, young children and people with preexisting chronic illnesses to reconsider dental amalgam.

Thankfully, for those groups barred from amalgam or unsettled by its potentially harmful effects, there are new and exciting alternatives. In the next blog post, we will explore those and discuss the alternate options for rectifying dental decay.

Works Cited

American Chemical Society. “Older dental fillings contain form of mercury unlikely to be toxic, study finds.” ScienceDaily, 12 December 2009.

American Heart Association. “Lead, mercury exposure raises cholesterol levels.” ScienceDaily, 5 November 2018.

Daley, Jason. “13,000-Year-Old Fillings Were ‘Drilled’ With Stone and Packed With Tar.” Smithsonian Magazine, 11 Apr. 2017,

U.S. Food and Drug Administration. “Dental Amalgam Fillings.” 18 Feb. 2021.

World Health Organization. “Mercury and health.” 31 Mar. 2017.

University of Georgia. “Have more than eight dental fillings? It could increase the mercury levels in your blood.” ScienceDaily, 27 September 2016.