Some scientific studies that make the news seem so plainly obvious, you wonder why anyone thought they even needed to be done. You know the kind – the kind that tells us that people who eat more vegetables are healthier or that those who get enough sleep feel better.
But here’s the thing: Such studies are actually important. Common sense might tell us that something is true, but medicine and public policy need hard data. When regulators are deciding whether to ban a possibly harmful substance or doctors are weighing treatment options, they can’t rely on intuition. They need peer-reviewed research with actual numbers.
Which brings us to a recent study in Applied Sciences that confirms what may seem like a no-brainer: The more mercury fillings you have and the longer they’re in your mouth, the more mercury you’re exposed to.
Wow.
To find this out, researchers took 224 plastic teeth and filled them with varying amounts of dental amalgam – from 1 surface to as many as 48. (A “surface” means one side or part of a tooth, such as the chewing surface on top or the sides facing your cheeks or tongue. So if a filling covers the top and two sides of a tooth, it counts as 3 surfaces.) They then submerged the teeth in artificial saliva and measured mercury release over 30 days.
By the end of the study, the research team found that the more amalgam surfaces, the greater the mercury release. They also found that older fillings released more overall. While the daily release rate was highest at the start of the study, the total accumulated mercury in the saliva kept climbing over the 30-day period as more mercury continued to leach out, just at a slower pace.
Still, there’s something interesting to notice here. For the fillings, the researchers used a type of material called Tytin amalgam, a typical high-copper formulation. Modern high-copper amalgams are designed to be stronger, more durable, and look better than older formulations.
They also release 10 times more mercury than older amalgams lower in copper. That’s because
Firstly, when subjected to wear/polishing, droplets rich in mercury are formed on the surface, showing that mercury is not being strongly bonded to the base or alloy metals. Secondly, high copper amalgams emit substantially larger amounts of mercury vapor than the low copper amalgams used before the 1970s. High copper amalgams [have] been developed with focus on mechanical strength and corrosion resistance, but [have] been sub-optimized in other aspects, resulting in increased instability and higher emission of mercury vapor.
The road to hell, as they say, and all that.
Of course, the Applied Sciences study has its limitations. For one, they used plastic teeth and artificial saliva in a controlled lab setting. Real mouths are far more complex. You’ve got chewing, grinding, toothbrushing, and temperature changes that vary throughout the day. All these factors are well-known to increase mercury release, along with other physical forces.
In other words, the mercury exposure that people with amalgams experience in the real world is probably higher than the study showed.
The good news is that plenty of great amalgam alternatives are available. In fact, modern composite resins aren’t only mercury-free; they’ve actually been shown to perform better than amalgam in some cases. A 2024 study, for instance, found that composite fillings had a significantly lower failure rate than mercury fillings, with only about 12% of composites failing compared to over 17% of amalgams.
Plus, placing composite doesn’t require us to drill away so much healthy tooth structure, and the restoration bonds directly to your tooth for a stronger, more conservative repair. All the composites we use in our office are fluoride-free and BPA-free.
Meantime, while we wait for policy to catch up with science, patients can take control of their own health. If you need new fillings, choose biocompatible alternatives. If you have amalgam fillings and want them replaced, insist on SMART-certified removal.
Image by brillenschlange, via Flickr
