Are dental amalgam fillings still safe? — Quartz

To celebrate Mother’s Day, Quartz staff collected story ideas from our mothers and sought to answer them. This mother asks: Is it possible my amalgam fillings are causing my migraines? Read more stories from the series here.

Of all the health and science advances of today, there’s one medical practice that has remained more or less consistent: using amalgam fillings to plug up our cavities.

These gray, metallic fillings contain a mixture of silver, tin, copper, and other metals, all bound together by small amounts of mercury. So if you have a metallic filling, chances are it contains mercury.

Mercury is usually synonymous with “poison” in a lot of people’s minds, and rightly so: Mercury in its elemental form can be toxic—but that doesn’t necessarily mean you should be worried about your fillings. It’s liquid at room temperature and is so goopy that it usually bounces right off skin; even if you were to swallow it, it should slide through your GI tract. Fillings are obviously solid; the mercury is only holding other metals together, and in doing so chemically changes so it won’t make its way down your throat.

However, the trouble starts if it evaporates into tiny particles in the air and is inhaled. In high levels, elemental mercury that makes its way to the lungs can cause brain and kidney damage, and small amounts inhaled over long periods of time can lead to chronic symptoms, like a persistent metallic taste in your mouth, vomiting, and swollen gums.

So why do we fill our teeth with this stuff? Mercury-containing amalgam fillings were first used in 1833 by two French dentists working in the US. At the time, they were a cheaper alternative to gold or silver, which were the norm for plugging holes and making crowns (which cover the whole tooth). With the 1800s not exactly being a prime time for dental hygiene, the introduction of these new fillings were a welcome introduction to rotting mouths (as opposed to just yanking the teeth out without sufficient pain medication, which was common practice). To this day, dental amalgams are the least expensive method of treating cavities; fillings made out of resin, porcelain, and even glass are generally more expensive, and may need to be replaced over time.

But are they dangerous? While it is possible that very small amounts of mercury can evaporate from amalgam fillings, the US Food and Drug Administration ruled in 2009 that these amounts are so low that that amalgams are safe for most people over the age of 6, the exception being those who have allergies to the filling itself.

“It has a 150-year proven track record and is still one of the safest, most durable, and affordable materials to a fill a cavity,” says Linda Vidone a periodontist practicing in Boston, Massachusetts. Vindone is also the vice president of clinical management of a dental insurance company called DentaQuest. “After years of research, mercury has been found to be the only element that will bind [silver, tin, and copper] together in such a way that can be easily manipulated into a tooth cavity.”

But this is where the controversy starts. In 1840, shortly after dental amalgams were introduced in the US, a group of dentists called the American Society of Dental Surgeons raised concerns that the mercury in these fillings was actually poisonous. Because they were so cheap and effective, however, their outcry was ignored, and amalgams continued to be the filling of choice. In 1859, a group of dentists in favor of amalgams formed the National Association of Dentists, which would later become the American Dental Association (ADA). The naysayers were silenced.

In the years that followed, there was a clear fracture in the dentist community about whether these amalgam fillings were actually benign. Today, major public health groups including the World Health Organization and the ADA state that amalgam fillings are safe (pdf) and effective at improving oral health. Yet there are still a vocal number of wholistic practitioners who are vehemently against using mercury in their dental work because they believe that the evidence is still inconclusive.

The World Alliance for Mercury-Free Dentistry, for example, refers to mercury as a “highly-polluting neurotoxin” that’s dangerous for patients, dentist implanting these fillings, and the environment. (Obtaining and discarding mercury isn’t a green practice.) The group works with global governments to advocate the elimination of these fillings. Some countries including Sweden, Norway, and Denmark have already gotten rid of amalgam fillings, although this was not on behalf of the group’s work.

On behalf of a mother of one of my Quartz colleagues, I asked Vidone if it is possible that amalgam fillings cause migraines. She said no. “When mercury is combined with other materials in dental amalgam, its chemical nature changes; it no longer has the same properties as the mercury we talk about regarding safety,” she said.

It is possible that another part of her oral health is related to her routine migraines, however. Jaw clenching, teeth grinding, and other kinds of bite changes during sleep can all cause these intense, overwhelming headaches. Although all of these should still be diagnosed and treated by a medical professional, it’s unlikely that amalgam fillings are the root of the problem.

That said, migraines are poorly understood themselves. It could be that these fillings are causing some kind of discomfort to cause the headaches, regardless of the mercury they contain. It’s possible for your dentist to replace these fillings with a new resin or porcelain filling, but it’ll likely be expensive, and there’s no guarantee it’ll alleviate the pain. Plus, the procedure itself is yet another opportunity to be exposed to vaporized mercury, although the risks associated with it are small.

Given the fact that the majority of the literature and major public-health organizations cite that amalgam fillings are safe, it seems that these fillings are nothing to lose sleep over. Switching them out for another material might not be worth the cost—even if you dentist tells you so. (Keep in mind that dentists themselves make more money if they perform more procedures, such as replacing fillings or using more expensive materials).

That said, there’s always a slight risk of the unknown; even though we don’t have any reason today to believe that amalgam fillings pose any kind of risk, data collected years later could tell a different story. And that might not be something to smile about.

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