Although the use of mercury amalgam to fill teeth has declined dramatically in recent years and even more countries are banning the material outright, amalgam still has its defenders.
What benefits could it have that outweigh the risk of having a neurotoxic metal implanted in living teeth?
For one, mercury amalgam is cheap. It’s what dental insurers (and government benefits) will pay for. Amalgam can also be placed more quickly and easily than tooth-colored composite. Here’s an example of what placing an amalgam filling can look like:
Compare that to the more intricate and technique-sensitive process of placing composite, which must be built up and cured (hardened) in layers, which requires precision in application, proper curing of each layer, and skillful shaping to achieve a natural look and proper function:
This layering technique offers several advantages, including minimized risk of shrinkage or gaps and improved bonding to the tooth structure, not to mention better looking results.
Mercury amalgam is also often credited with being stronger and more durable than composite, better able to handle the pressures of chewing. Yet it’s been shown that some mercury is released from those fillings with every bite and swallow. Exposure to heat does the same, and magnetic fields and different types of radiation can increase mercury release. If those fillings are made with modern high copper amalgam, the mercury release can be even greater – up to 10 times as great, according to one 2017 study on the matter.
High copper amalgams [were] developed with focus on mechanical strength and corrosion resistance, but [were] sub-optimized in other aspects, resulting in increased instability and higher emission of mercury vapor.
Inhaled mercury is especially dangerous, for once in the lungs, it can quickly and easily enter the general circulation and be carried throughout the body. Mercury is especially prone to building up in the brain, as well as the liver and kidneys. According to autopsy studies, up to 95% of all mercury deposits found in the human body come courtesy of dental amalgam.
What’s more, science has shown that amalgam actually isn’t more durable when compared to the advanced composites available to us today.
Consider the study published earlier this year in Bioengineering. Using records from more than 650,000 patients at a large Israeli dental care provider, its authors compared the longevity of posterior (back of the mouth) fillings between 2014 and 2022, amalgam and composite alike. So long as a tooth didn’t need to be redone, root canaled, or extracted, the filling was considered to be a success.
For amalgams, the failure rate was roughly 17.5%, or about one-fifth of the 113, 281 mercury fillings that had been placed. The failure rate for composites? Just under 12% – even as about 5 times as many of these fillings were placed during the study period.
“The current study found no evidence of the superiority of amalgam over composite restorations,” the research team concluded.
At a time when a global environmental decision has been made to reduce the use of mercury, it seems that there are no clinical reasons to continue treatments with amalgam alloy in dentistry. We found that more composite restorations are being placed; this may be due to aesthetic concerns, generally higher compensation, or because some healthcare providers believe that composites are safer. This study, based on big data, indicates that composite restorations have a lower replacement rate than amalgams, and there is now strong evidence to end the long-standing debate on the longevity of amalgam and composite materials. Hence, we can strongly support the Minamata recommendations for the use of composite resin materials only.
As do we. As we have for years, committed to caring for our patients with mercury-free, mercury-safe dentistry.
