When you visit the dentist, you’re probably hoping that you’ll get a clean bill of dental health. Keep in mind, though, that you should also be looking closely at the health of your dentist’s office. Many dental procedures that have been used for years—from fluoride applications to amalgam fillings to root canals—are now under scrutiny for their possible role in causing health problems. Learning about the issues surrounding these procedures can make you a more informed and safer dental patient.
[2020 Editor's Update: Since the publishing of this article, new evidence and clarifications have emerged. Today, both the ADA and the APHA do not consider amalgam to be an unsafe material for fillings, although it can have a negative environmental impacts when it enters waterways. The FDA has reviewed the evidence on amalgam and found it to be safe for adults and children over 6. This classification of "safe" does not indicate that no mercury is released into the body via amalgam fillings, but rather that it has not been linked to any negative health impacts. Part of the reason for this is the distinction between different types of mercury, as the kinds of mercury found in fish is considerably more potent than the mercury found in amalgam. The article as originally published is below.]
Amalgam, or silver, fillings, which have been widely used by dentists for more than a century, are about 50 percent mercury; the balance is made up of other metals, mainly silver, copper, tin, and zinc. According to the American Dental Association (ADA), amalgam is an ideal substance for dental restorations because it’s durable, easy to use, highly resistant to wear, and cost-effective. The ADA claims that the presence of mercury in fillings is not a problem, because the fillings release only minute amounts of mercury vapor, and such low-level exposure has not been proven to be harmful.
A growing number of dental professionals disagrees. “The ADA warns that amalgam is toxic before placement and after removal, so dentists have to take precautions with these procedures,” says Dr. Robert Johnson, a biologic dentist who heads the Natural Horizons Wellness Center in Fairfax, Virginia. “There’s no reason for amalgam to suddenly not be toxic once it’s in someone’s mouth.” There’s little dispute about one thing: everyday activities like brushing your teeth, eating, and drinking hot liquids cause amalgam fillings to release mercury vapor.
The ADA acknowledges that chewing and grinding teeth may cause amalgam fillings to release one to three micrograms of mercury per day, while the World Health Organization (WHO) estimates that the average amount is actually three to 17 micrograms per day.
There’s also no doubt that mercury is dangerous: According to the Agency for Toxic Substances and Disease Registry (ATSDR), a federal agency under the US Department of Health and Human Services, exposure to “high levels” of mercury can permanently damage the brain, kidneys, and a developing fetus.
What’s still being debated is exactly how much mercury exposure it takes to cause these effects, and how much of that is likely to come from fillings. Proponents of amalgam fillings say that the amount of mercury released from them is nowhere near a dangerous level, while critics contend that research hasn’t conclusively proven that amalgam is safe.
“The bottom line is, there’s of lack of attention to this issue in the dental field,” says Dr. Michael Ziff, DDS, executive director of the International Academy of Oral Medicine and Toxicology (IAOMT). “When physicians prescribe drugs, they’re very aware of the toxicology of the medications—but when you ask dentists what the absorption rate of mercury vapor from amalgam fillings is, many of them have no idea. They take the ADA’s word for the safety of fillings instead of looking at the science.”
If potential health hazards aren’t enough to make you exercise caution around amalgam fillings, consider their effect on the Earth. Scientists agree that mercury needs to be kept out of the environment. According the nonprofit Mercury Policy Project (MPP), many dentists contribute to the prevalent problem of mercury pollution in waterways by failing to separate mercury from their wastewater, and by incinerating dental waste that contains mercury, which releases that substance into the atmosphere. Urging your dentist to adopt best management practices for mercury waste disposal—a step also endorsed by the ADA—can greatly reduce the amount of dental-related mercury pollution.
“The good news is that 25 percent of dentists across the US no longer place mercury fillings. Many recognize that mercury use reduction is good for the environment, for their patients, and for business, too,” says MPP executive director Michael Bender.
Since the 1940s, fluoride has been added to community water supplies around the US in order to prevent tooth decay. Many dentists credit fluoridated water with dramatically lowering the incidence of cavities in the population, but a reassessment of the original studies on fluoride’s contributions suggest that it might not be quite as beneficial as originally supposed. Studies on fluoride published in the Journal of Dental Research have shown that fluoride’s action occurs mainly on the surface of the teeth, meaning that the benefits of ingesting the substance are negligible. Other research suggests that fluoride might be harmful.
Fluoride is generally not considered dangerous at low levels—the key is to make sure you don’t get too much. Data from the National Toxicology Program indicates that fluoride may be a carcinogen. And a University of Utah study found “a small but significant increase” in the risk of hip fracture in elderly men and women exposed to artificial fluoridation at one part per million—a low level that’s within the range recommended by the US Environmental Protection Agency (EPA). Though the links between fluoridated water and cancer or hip fractures haven’t been definitively proven, some scientists are urging caution and calling for an end to the practice of adding fluoride to drinking water.
Advocacy groups are also raising questions about the safety of sealants. Sealants, which are usually applied to back teeth as barriers against decay-causing bacteria, are under fire because they may leach bisphenol-A (BPA), an endocrine disruptor. Endocrine disruptors have been linked to declining male fertility and increased cancer rates in humans.
Controversy began with a University of Granada study, published in Environmental Health Perspectives in 1996, which found that BPA had leached into patients’ saliva shortly after dental sealant application. In response to this study, the ADA tested the 12 brands of sealants that carry its seal of acceptance and found that 11 of them leached no detectable BPA; they contacted the manufacturer of the twelfth, who implemented additional quality control procedures and whose product then leached no detectable BPA in subsequent testing. However, many experts say much more research is needed before it can be concluded what kinds of sealants leach BPA, and whether BPA can be absorbed from saliva at harmful levels.
Some dentists are also challenging conventional wisdom on root canals. These invasive procedures are performed when bacteria infiltrate teeth through cavities or cracks and compromise the soft tissue inside. The root canal procedure removes diseased pulp and seals the tooth to prevent infection from spreading.
Some research—based largely on studies conducted by Dr. Weston Price in the early 20th century and detailed in a 2008 book by Dr. George Meinig—suggests that bacteria can continue to spread despite root canal procedures, possibly entering the bloodstream and causing harmful infections in the liver, kidney, heart, eye, or other tissue.
The American Association of Endodontists states that more recent attempts to duplicate Dr. Price’s research have not yielded the same results, and root canals are safe; the IAOMT says that contemporary studies show microorganisms persisting in root canals after treatment. Unfortunately, the current alternative to a root canal is tooth extraction, which dentists are reluctant to recommend.
“We need more research on the actual health risks to patients from this treatment, and whether techniques can be improved to reduce risk,” says Dr. Ziff. Dr. Johnson notes that the use of biocalyx, a special cement that expands as it hardens, is a developing technique that shows promise for reducing infection risk from root canals.
The Bottom Line
“The dental establishment feels threatened at the idea of finding anything harmful in the materials or practices it’s been recommending for decades,” says Dr. Johnson. “But just as we must urge the auto industry to reconsider its reliance on fossil fuels, we must urge the dental industry to support additional research on its favorite materials in order to protect human and environmental health.”
There’s reason to be hopeful, adds Dr. Ziff. “Individual dentists are making more of an effort to educate themselves, and I expect we’ll see some major positive changes over the next couple of decades,” he says.