In this month’s letter, ADEA President and CEO Dr. Rick Valachovic spotlights how a global treaty on mercury appears to be accelerating the development of new restorative materials and prompting discussion within academic dentistry about dental amalgam’s place in the curriculum.
Think about the teeth in your mouth. If you are old enough to have had a tooth restored before 1980, it is highly likely that the material used was dental amalgam. In the unlikely event you had a tooth restored in the 1990s or later, you were probably given a choice between amalgam and resin composite.
Today, composite is pretty much considered the default restorative material in North America, although amalgam remains in use and continues to serve a vital purpose. Ten years from now, I suspect most dental offices and clinics will no longer stock amalgam—mostly in response to this long-term trend, but also because of a new environmental treaty that aims to make amalgam (and other products containing mercury) less available in the years ahead.
The Minamata Convention on Mercury represents four years of negotiation among 140 nations under the auspices of the U.N. Environment Programme (UNEP). Named for a Japanese city where inhabitants were seriously harmed by mercury pollution, the treaty calls on nations to reduce the use of mercury in small-scale gold mining, to control its release from coal-fired power plants and to ban the production, import and export of many mercury-containing products by 2020.
Dental amalgam was initially slated to be among those banned products. At the start of the negotiations, groups who view amalgam as a human health risk—despite a lack of credible scientific evidence to validate their claims—generated considerable support for a ban. A year later, two nongovernmental organizations, the International Association for Dental Research (IADR) and the Worldwide Dental Federation (FDI), joined the negotiations, bringing their scientific understanding of dentistry and human health to a political discussion framed largely by environmental concerns. The presence of a unified voice for organized dentistry turned the negotiations around. In the end, UNEP delegates agreed to a phase down—rather than a ban—of the use of dental amalgam, with no fixed date for its elimination.
For an insider’s perspective on what brought about this evolution in the delegates’ thinking, I called Dr. Dan Meyer, Senior Vice President, Division of Science and Professional Affairs at the American Dental Association (ADA). Dan acted as an ADA advisor to IADR and FDI and personally attended four of the five international meetings held to negotiate the Minamata Convention. According to Dan, many who attended the UNEP Intergovernmental Negotiating Committee meetings, especially those from countries where dentists are a rarity, were unaware of the complexities of the dental issues at stake.
“To me that’s a tragedy,” Dan said. “These representatives didn’t understand the oral health implications of limiting the use of or trying to phase out dental amalgam. They didn’t realize what a huge detriment that would be to the oral health care of the individuals they were trying to represent and protect.”
Dan dismissed many of the anti-amalgam groups’ claims as misrepresentations and misinformation not supported by science, but he told me that refuting these allegations proved a formidable task. Nevertheless, over time, he and others representing the oral health professions conveyed the message that retaining amalgam as a restorative option benefits both patients and providers.
To those of us who have been using amalgam for decades, its value as a tried and true material that is durable, affordable and less sensitive to moisture than the alternatives may be self-evident. (Those of you who are not fully acquainted with the differences between dental restorative materials can learn more from this primer.)
That said, I can also imagine a future in which we will be able to manage without amalgam, even in the procedures where it is currently the restorative material of choice. My recent conversations with researchers and materials scientists, who for decades have been following the debate surrounding amalgam use, have led me to wonder whether imminent advances in materials science, recent revelations about existing materials and shifting political priorities might not coalesce to eliminate most amalgam use in just a few years’ time.
Amalgam is touted for being less costly and more durable than other restorative materials. Those distinctions certainly held true in the past, but perhaps the time has come to re-evaluate our assumptions in light of new research and some promising developments. First, let’s consider cost.
A study published in Public Health Reports in 2007 estimated that a ban on amalgam in the United States would increase the cost of each dental restoration by $52, or nearly 20%. While those figures appear to give amalgam a clear cost advantage, they do not reflect the cost of implementing best management practices (BMPs) aimed at dealing with amalgam waste.
The use of BMPs was just beginning to take hold in the mid-2000s when the study data were collected. I can remember an earlier time when most of us routinely disposed of excess amalgam in the trash. Today our clinics recover the vast majority of that waste amalgam. Recovery protects the environment but also raises the cost of using the material.
The other commonly cited benefit of amalgam is its durability, which has traditionally been viewed as far superior to that of resin composites. Recent research suggests that this perceived advantage has also been overstated. I know many of you will beg to differ, but at least one 2010 study from the Netherlands supports this contention. The study found that, after 12 years, composite survival rates exceeded those of amalgam restorations, except in cases involving three-surface restorations in high-risk patients. Additionally, few dentists wait for a restoration to fail before replacing it. This tendency may be significantly reducing the lifespan of many restorations and skewing the data about their longevity.
So, do these re-appraisals of the cost of amalgam use and the durability of composites mean that our community can dispense with dental amalgam today? No, not yet. But the day when we can may not be far off.
Last month, the National Institutes of Dental and Craniofacial Research announced the award of $2.8 million in research grants for the development of a long-lasting composite polymer capable of replacing current restorative materials. The six groups receiving these awards are expected to work cooperatively and share data and resources to achieve the goal of developing a material with a clinical service life exceeding current commercial materials by at least a factor of two. The hope is that this collaboration will produce a viable alternative material within five years or perhaps even sooner.
Even if that timeline is overly optimistic, there’s little doubt that the use of amalgam will continue to decline. In addition to efforts to reduce its presence in the waste stream, consumers—when given the choice—are opting for materials that mimic the appearance of natural teeth.
I recently discussed this trend with Dr. Mark Wolff, Professor and Chair of the Department of Cariology and Comprehensive Care and Associate Dean for Predoctoral Clinical Education at the New York University College of Dentistry (NYUCD). He told me that at NYUCD, amalgam represents less than 20% of the restorations placed in the dental clinic, and that figure has been declining. This trend results largely from patient preferences but also from NYUCD’s decision to eliminate the requirement that students place a certain number of amalgam restorations prior to graduation. Mark believes students should still learn how to place amalgam, but he considers it unethical to force the material on patients who don’t want it.
“We still teach amalgam—in the lab,” he told me. “In the clinic, a bonded restoration is the default because we can do it more conservatively.”
Of course the most conservative approach is prevention, a strategy for reducing the use of amalgam that the Minamata Convention advocates and that everyone can agree upon. As Dan Meyer points out, “No dental restorative material is as beneficial to oral health as preserving the intact, natural tooth structure, and with the emphasis on prevention, sealants, fluoride toothpaste and public water fluoridation, we can reduce the use of all dental restoratives to a greater extent in the future.”
Next month, I’ll talk more about prevention and discuss Caries Management by Risk Assessment, better known as CAMBRA. Meanwhile, a diplomatic conference was held in Japan last week where the Minamata Convention was opened for signature. Canada was one of 92 nations to sign the document, and other nations are expected to follow suit in the year ahead. One of the implications for our schools and programs is clear. Although the time we spend teaching the placement of amalgam will continue to diminish, we will still need to teach our students how to deal with the amalgam restorations already in circulation. Some estimates put their number around 900,000, and as these fail, dentists will need to know how to recover and recycle the resulting waste.
The most recent ADA survey, completed in 2010, indicated that half of private dental practices that place amalgam restorations were using amalgam separators. In states that have enacted voluntary recycling incentives or regulatory mandates, that percentage is much higher today. So once again, politics is playing a role in the transition to the next generation of safe, effective, affordable, durable—and environmentally friendly—restorative materials.
Completing this transition may require continued political involvement. Traditional regulatory processes add years to the time it takes to bring a new product to market. If dental professionals are eager to conclude the phase down of amalgam in short order, they will need to think about advocating for the acceleration of the approval process for whatever amalgam substitute emerges.
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