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Dental Amalgam—Preserving a Proven Dental Material
Policy Date: 10/30/2012
Policy Number: LB-12-01
Related APHA Policies
Policy Statement 7711 – Dental Health in a National Health Program
Policy Statement 9910 – Preventing Human Methylmercury Exposure to Protect Public Health
Policy Statement 8807 – Surveillance of Occupational Disease and Injury
Policy Statement 201015 – Securing the Long-Term Sustainability of State and Local Health Departments
Policy Statement 200712 – Toward a Healthy, Sustainable Food System
Policy Statement 200015 – Drinking Water Quality and Public Health (Position Paper)
Dental amalgam has been used widely as a restorative dental material since the 1800s. Due primarily to aesthetic trends, there has been a decrease in the use of dental amalgam and a corresponding increase in the use of tooth-colored restorative materials. However, these materials fall short relative to dental amalgam: they are far more technique sensitive, have lower clinical survival rates, and are more expensive, and there are health concerns associated with their use. Since the inception of dental amalgam, claims have been made about possible detrimental health effects caused by the mercury in its mix. These allegations have been refuted by well-designed clinical studies. Nonetheless, increasing concern over mercury in the environment has led to a worldwide movement to phase out dental amalgam. Although there is general consensus that use of mercury should be minimized, the contribution of dental amalgam to overall mercury pollution is negligible. Continual improvements in the manipulation of dental amalgam and disposal of excess material in accordance with environmental safety protocols and professional recommendations have minimized mercury exposures in patients, dental personnel, and the environment. Phasing out dental amalgam may have detrimental public health consequences, resulting in a higher rate of failed restorations, more frequent need for retreatment, or recurrence of disease. The problem would be most critical in lower income communities and countries, in which field conditions and economic circumstances result in the alternative restorative options being less successful and less affordable. Accordingly, APHA’s Oral Health Section opposes efforts to ban the use of dental amalgam and recommends its continued use as a safe and effective restorative filling material in posterior teeth.
Dental amalgam has been used widely as a restorative dental material since the early 1800s. The clinical properties of amalgam, including its ease of placement, high compressive strength, relatively low cost, and long-term survival rates, remain largely unrivaled.
During the past 3 decades there has been a decrease in the use of dental amalgam and a corresponding increase in the use of tooth-colored restorative materials such as dental composites. This change is due primarily to aesthetic trends: one of amalgam’s limitations is its unaesthetic appearance due to its gray or silver color. However, even the newest tooth-colored materials fall short as posterior fillings relative to amalgam: they are far more technique sensitive, have lower clinical survival rates, are more expensive, and are far more difficult to use in some clinical situations.
Since the inception of dental amalgam, claims have been made about the possibility of detrimental health effects caused by the mercury in its mix. These allegations have been refuted by well-designed clinical studies. Nonetheless, increasing concern over mercury in the environment has led to a worldwide movement to phase out dental amalgam.[4,5] There is general consensus that use of mercury should be minimized to protect our environment and health. However, continual improvements in manipulating dental amalgam during clinical procedures and appropriate disposal of excess material in accordance with environmental safety protocols and professional recommendations have lowered mercury exposures among patients and dental personnel as well as environmental exposures.[6–11]
Decisions regarding phasing out dental amalgam or continuing its use as the filling material of choice for posterior teeth in the absence of an equal or superior restorative material have important public health implications. These ramifications increase when the potential replacement is a material that is less durable and more expensive and has identifiable health risks of its own.[12,13]
Economic considerations: Economically, there is still no adequate alternative for dental amalgam. Its combination of durability and low cost is unmatched by any other dental restorative material. According to Chadwick et al., “When the initial cost and the longevity are considered together, resin composite turns out to be from 1.7 to 3.5 times more expensive than amalgam.”
Multiple economic evaluations comparing the use of dental materials, including dental amalgam, have shown that dental amalgam is more cost effective and cost beneficial than tooth-colored alternatives, and it has a longer functional time and lower theoretical cost per year of function.[16,17]
Studies have estimated the macro-economic impact of regulating or banning the use of amalgam restorations in the United States. Beazoglou et al. estimated the direct costs of a ban on the use of amalgam restorations: a ban on their use in children and young people aged 0 to 19 years would increase dental expenditures by about $1.1 billion per year (totaling $13 billion from 2005 through 2020). Banning amalgams in the entire population would increase dental expenditures by about $8.2 billion in the first year and lead to an increase of $98.1 billion from 2015 through 2020. Fleming and Janosky evaluated current levels of amalgam and composite use and calculated cost increases for composite alternatives in the event of a ban. They estimated that total increased expenditures for restorations over a 10-year period would be $15.4 billion in the event of a total ban and $10.3 billion with a partial ban (a ban among children younger than 14 years and women of childbearing age).
Banning the use of dental amalgam would have a strong economic impact. The impact would be most pronounced in low-income countries with limited access to dental materials, underfunded health care delivery systems, and/or inadequate numbers of practitioners trained to replace dental amalgam.
Environmental aspects, management, and disposal: Mercury exists in 3 forms—elemental, as part of an inorganic compound, or as part of an organic compound. Although each form has its own toxicological profile, organic mercury is the most toxic, followed by elemental mercury and finally inorganic mercury.
Worldwide, the natural degassing of the earth’s crust accounts for as much as two thirds of the mercury entering the environment. According to the US Environmental Protection Agency (EPA), gold mining is by far the greatest anthropogenic source of overall air, water, and solid waste releases, accounting for 81.8% of the total. Utility coal combustion is next, at 5.3%, followed by switches and relays at 3.8%. Dental amalgam accounts for a mere 0.5% of total air, water, and solid waste releases.
To minimize mercury discharge to municipal water agencies, the American Dental Association (ADA) has spearheaded efforts focused on environmentally sound management and disposal of dental amalgam. ADA adopted a mercury hygiene protocol as guidance to dental personnel for safe handling of mercury and dental amalgam in 1999. Updated in 2003, the guidelines include proper handling of mercury and dental amalgam during the preparation and placement of amalgam restorations, office engineering, and handling of mercury spills.
In 2007, ADA released best management practices for amalgam waste to help dental offices institute the necessary precautions to reduce the amount of dental amalgam discharged into local sewer systems. These practices include using precapsulated alloys; recycling waste amalgam; using chair-side traps, vacuum pump filters, and amalgam separators; recycling extracted teeth that contain amalgam; and using appropriate line cleaners. A recent evaluation of amalgam separators showed that all of the separators assessed removed at least 95% of amalgam particles from the waste stream.
In 2008, EPA, ADA, and the National Association of Clean Water Agencies signed a memorandum of understanding to encourage ADA members to voluntarily begin using amalgam separators as part of the best management practices issued in 2007. As part of this agreement, ADA agreed to report on the use of amalgam separators by dentists nationally. In 2009, ADA reported that 40%–51% of dentists nationwide were using amalgam separators.
Twelve states and several municipalities now require the installation of amalgam separators in dental offices. In addition, Michigan has a rule that will go into effect by December 31, 2013. The use of amalgam separators continues to be voluntary in the remaining states.
In 2010, EPA released its Effluent Guidelines Program Plan, part of which focused on dental facilities’ use of amalgam separators to reduce the discharge of dental mercury into the environment. A rule was proposed to require dental facilities to install amalgam separators. Until the rule is finalized (which is expected by the end of 2012), EPA is recommending voluntary installation of amalgam separators.
Biological basis and ethical aspects: The key ethical factor that drives any action-related decision is the nature and stature of evidence in favor of the action. Recommendations regarding a potential phase out of dental amalgam must include a risk-benefit analysis.
The scientific evidence regarding harmful effects of dental amalgam is circumstantial and inconclusive. Findings indicating adverse clinical effects of dental amalgam restorations must rule out confounding sources of exposure, especially those that have been shown to be harmful.
Patients’ exposure to mercury from dental amalgam restorations during the filling procedure is minimal and well below the threshold for hazards to health. The European Scientific Committee on Emerging and Newly Identified Health Risks concluded that there is no scientific evidence for risk of adverse systemic effects and that the current use of dental amalgam does not pose a risk of systemic disease.
In the absence of clearly demonstrated risks, one must consider another important factor of dental amalgam restorations: their cost. Any decision to phase out dental amalgams must first account for availability of materials with equivalent properties and costs. A ban on amalgam restorations would have a substantial short- and long-term impact, increasing expenditures for dental care, decreasing utilization, and increasing untreated disease.
The only potential ethical argument that can be put forward for a phase out would be invoking the “precautionary principle” to prevent any possible purported harm that may occur because of these materials. The precautionary principle specifies that if any treatment has a suspected risk of causing harm to the public, the burden of proof that it is not harmful, in the absence of a scientific consensus, falls on those taking the action. But the precautionary principle is not an unyielding fixed compass for action because any study, however questionable, can derail any intervention. Furthermore, in instances in which risk of harm is suspected, the very course of action or inaction demanded by the precautionary principle is accompanied by risks of its own. Harvard legal scholar Cass Sunstein eloquently summarized the fundamental incoherence of the precautionary principle: “The regulation that the principle requires always gives rise to risks of its own—and hence the principle bans what it simultaneously mandates.”
In the case of dental amalgam, the preponderance of high-quality evidence indicates that there is no harm to humans, and the only suggestion of any adverse health effects comes from a small number of methodologically flawed studies. A decision under such circumstances to phase out dental amalgam can be viewed only as coercive action. An early landmark US Supreme Court ruling mandates that coercive public health action must be shown to be effective, necessary, proportional, impartial, and the least restrictive possible alternative.
The argument for invoking the precautionary principle is weakened substantially by the fact that the strongest studies (clinical trials) assessing the relationship of dental amalgam fillings to neurological and renal disorders demonstrate no statistically significant differences in adverse neuropsychological or renal effects between amalgam and other materials.[6,30]
In contrast, a recent randomized safety trial that assessed the relationship between resin-based composites (RBCs) and psychosocial functioning in children determined that greater exposure to bisphenol-A-glycidyl-methacrylate-based dental composites in children aged 6 to 10 years was associated with worse self-reported psychosocial functioning at a 5-year follow-up. There were no such associations with exposure to dental amalgam or compomers.
Proposed Recommendations Statement
Although the Review Committee of the APHA Oral Health Section acknowledges that the release of mercury into the environment can be harmful to the environment as well as both human and animal life and thus should be minimized and avoided whenever possible, it also recognizes that:
• The contribution of dental amalgam to harmful mercury in the environment is minimal and can be largely prevented through appropriate use of dental waste management techniques.
• Banning the use of dental amalgam would have a strong economic impact, felt most severely in low-income countries with limited access to dental materials.
• A phase out of dental amalgam could have unintended negative public health consequences, as such an action would deprive dentists and patients of a restorative option that has a very long track record of safety and effectiveness while compelling them to choose an alternative that may be less effective in some situations.
On the basis of the best available scientific evidence, the American Public Health Association recommends that dental professionals continue the use of dental amalgam as a restorative material and that schools and programs educating dental professionals place greater emphasis on education and training for all dental personnel regarding mercury hygiene. In addition, it is recommended that state regulatory agencies implement requirements for training regarding best management practices to minimize the release of mercury from dental amalgam into the environment.
Since the inception of dental amalgam, claims have been made about the possibility of detrimental health effects caused by the mercury in its mix. These allegations have been refuted by well-designed clinical studies.[6,8] Health concerns have been raised by those opposed to the use of amalgam due to its release of mercury vapors. However, scientifically sound studies have demonstrated that the discharge of mercury is so negligible that it is highly unlikely to pose any risk to humans.
As the environmental concern about mercury has increased, those in favor of discontinuing dental amalgam claim that the significant contribution of dental mercury waste and its persistence in the environment are certain. Mercury from domestic wastewater and municipal treatment plants (which includes all mercury from dental offices and human waste, as well as all other domestic and municipal sources of mercury) accounts for less than 1% of mercury entering the environment. This amount does not account for dental mercury entering the environment through the incineration of municipal waste. According to the Virtual Elimination Pilot Project: Mercury Sources and Regulations report (Table 6), “dental use” of mercury in 1995 was 2.9 tons out of 245.3 tons of total discards of mercury into the municipal solid waste stream. This represents 1.18% of the total discards. In the EPA Mercury Study report to Congress, the municipal waste combustor mercury emission was 18.7% of the total. Thus, the dental mercury contribution from incineration of municipal waste to the total mercury entering the environment is 0.22%. As a result, even if the dental use of mercury were completely eliminated, there would still be 99.78% of the current level of mercury entering the environment from incineration of municipal waste; the elimination of dental amalgam would produce essentially no benefit to the environment.
Finally, to support the phase out of dental amalgam, it is claimed that alternatives have been in clinical use for more than 30 years, with little evidence of clinically significant adverse effects to date. While the former is true (see alternative strategies), the latter is inaccurate. Amalgam lasts longer than other materials when used for restorations in the permanent dentition and for large restorations.[2,35–37] The aesthetics of tooth-colored alternatives, in particular RBCs, challenge the continued use of dental amalgam. However, scientific evidence demonstrates that RBCs are more susceptible to failure and recurrent caries, particularly in large, multiple-surface restorations and when moisture cannot be controlled.[1,38,39] In addition, numerous studies and reviews have shown that dental amalgam outlasts RBCs.[2,30,39,40] Therefore, as of today, there are no dental restorative materials as cost effective and reliable as dental amalgams. Another consideration is the fact that recent studies have revealed an association between RBCs and adverse psychosocial outcomes among children.[41,42]
Use of alternative materials has been suggested as an alternative strategy to the use of dental amalgam. However, selection of a restorative material in dentistry must take into consideration such factors as type of dentition (primary or Permanent), size of the lesion, and the caries risk of the individual patient.[37,43,44] Although resin-based composites are the most common alternative, other substitutes include glass ionomers and compomers.[2,45,46]
RBCs have been recommended primarily for single-tooth surface restorations in the primary and permanent dentition and conservative preparations in the permanent dentition.[37,38,47] Glass ionomers have been advocated as a restorative material in the primary dentition due to their ability to adhere to the dental tissue, their ease of use, and the cariostatic effect caused by continuous release of fluoride. Compomers, a cross between RBCs and glass ionomers, are superior to glass ionomers with respect to mechanical properties and wear resistance but inferior to RBCs.[48,49] In addition, they release less fluoride than glass ionomers.
Stainless steel crowns, another alternative, are recommended for multisurface restorations in the primary dentition, for restorations in the primary and permanent dentition in patients with high caries risk, and for teeth with developmental defects.[51,52]
Therefore, APHA recommends that:
• Dental professionals continue the use of dental amalgam as a restorative material (i.e., no action is necessary—dental professionals will continue to provide services as they have been doing).
• Schools and programs educating dental professionals place greater emphasis on education and training for all dental personnel regarding mercury hygiene. Dental schools, dental hygiene programs, and dental assisting programs are encouraged to incorporate training about mercury hygiene best practices into their curricula. This can be accomplished via the American Dental Education Association, the Commission on Dental Accreditation, and related agencies.
• State regulatory agencies implement requirements for training, including continuing education, regarding best management practices to minimize the release of mercury from dental amalgam into the environment. Individual state dental organizations, groups of public health dentists, and state dental boards should review and encourage the addition and/or implementation of these requirements in Dental Practice Act policies.
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