Evidence shows the risk that “silver” mercury amalgam fillings pose to human and environmental health. Even the FDA now advises against them for roughly two-thirds of Americans.
Still, many dentists prefer it, especially for filling the back teeth – teeth that experience more wear and tear than others from the force of biting. They can even point to a new analysis in Cochrane Reviews that concludes, on the basis of 8 studies, that mercury amalgams “are effective, enduring, and safe, while composite resin restorations are more likely to fail and lead to secondary caries.”
As is often the case, though, the devil is in the details.
For one, the review team found the evidence for amalgam to be “low certainty,” with all 8 studies at high risk of bias. All were also “quite old, and composite resin materials have likely improved since the included studies were conducted.”
In addition, the findings were imprecise and sometimes inconsistent, so we cannot be sure that the evidence is reliable.
Certainly, newer composites have proved to be very strong and durable, although just as technique-sensitive – far more than amalgam, as you can see by comparing the two videos below.
In fact, many of the most common reasons a composite filling can “fail” are due to things like the tooth not being kept dry enough, an ineffective seal, inadequate layering, or other error. Other research has suggested that both smoking and heavy alcohol use may raise a patient’s risk of having a composite fail, although the link to smoking was found only among males.
Of course, composite resins have one supreme virtue over mercury amalgam: They are far less toxic. This alone makes them preferable to packing a neurotoxin into teeth, mere inches from the brain, with mercury vapor being released with every bite and swallow. Of course, any continued use of amalgam is a problem not just for the patient or dental workers. It’s a problem for us all by sheer virtue of dentistry being such a major contributor to mercury pollution of our water, soil, and air.
That said, there are certainly some composites that may be problematic, as well, containing BPA, fluoride, and other components of concern. As the authors of another recent paper put it,
Scientific literature is now reporting on the importance of using the most biocompatible material for the patient. Research is finding that not only using the least reactive material is important, but also how that material may interact with other materials that may have already been implanted into the oral cavity. Unfortunately, even today, dental procedures are often designed simply for the functionality of the treatment, or for cosmetic purposes, even though it is well established that all foreign materials introduced into the human body will elicit an immune response.
While there are some BPA- and fluoride-free composites that are considered broadly biocompatible, the best way to make sure is to have biocompatibility testing done prior to any dental work. It’s a simple blood test to help us determine which materials may be safest for any given patient and which should be avoided at all costs due to potential allergies or sensitivities.
You can learn much more about how we ensure biocompatibility in our office here.