Regulatory Work Group Leader:

Carolyn A. Tylenda, D.M.D., PhD. -
Food and Drug Administration

Regulatory Work Group Members:

Betty W. Collins -
Food and Drug Administration

W. Don Galloway, Ph.D. -
Food and Drug Administration

Carol M. Lee -
Food and Drug Administration

Charles Somerville
Food and Drug Administration

RECOMMENDATIONS OF THE REGULATORY WORK GROUP

The Regulatory Work Group has considered its assigned discussion topics and has developed the following recommendations:

Determine whether the absence of definitive risk information for dental amalgams should alter the product's regulatory status as a medical device.

Classification of dental devices was published in December 1987. Dental amalgam was considered to consist of two devices: dental mercury and amalgam alloy. Dental mercury, a class I device, is defined in 21CFR 872.3700 as "a device composed of mercury intended for use as a component of amalgam alloy in the restoration of a dental cavity or a broken tooth." Class I devices are those for which "General Controls" are sufficient to assure safety and effectiveness. General Control requirements include registration of each manufacturing location, listing of the device(s), possession of a cleared Premarket Notification [510(k)], and Good Manufacturing Practices (GMPs). General Controls are minimal requirements that apply to class I, II and III devices. Amalgam alloy, a class II device, is defined in 21CFR 872.3050 as "a device that consists of a metallic substance intended to be mixed with mercury to form filling material for treatment of dental caries." A class II device is one for which reasonable assurance of safety and effectiveness can be achieved through the application of "Special Controls". Special Controls include postmarket surveillance, performance standards, patient registries, development and dissemination of guidelines, recommendations and other appropriate actions. A class III device is one for which insufficient information exists to assure that general and special controls provide reasonable assurance of safety and effectiveness. Generally, class III devices are those that sustain or support life, are of substantial importance in preventing impairment of human health or present potential unreasonable risk of illness or injury.

In recent months, data purported to establish risks associated with dental amalgam have undergone extensive scrutiny by several panels of experts. In March 1991, FDA held a meeting of the Dental Products Panel to assess the scientific evidence regarding the toxicity of dental amalgam. The Dental Products Panel consists of experts selected from across the country to help FDA evaluate the safety and effectiveness of devices and to make recommendations to FDA on device related issues. The Panel unanimously agreed that sufficient valid scientific data do not presently exist that establish dental amalgam to be a health hazard in humans. However, the Panel agreed that the information presented at the panel meeting raises questions that warrant further research. In November, 1991 the CCEHRP Subcommittee on Risk Assessment completed its report on the evaluation of risk from exposure to mercury vapor from dental amalgam, and reached a similar conclusion. While it is clear that mercury vapor is continually released from dental amalgam, it is not clear that this exposure leads to toxicity. However, the potential for toxic effects due to low levels of exposure to mercury vapor from dental amalgam restorations must not be disregarded. The FDA Dental Products Panel, the CCEHRP Risk Assessment Subcommittee, and the CCEHRP Benefits Subcommittee on Amalgam, as well, have proposed that well designed scientific studies be conducted to precisely define those potential toxic effects, if any.

The Regulatory Work Group recommends that the Food and Drug Administration view dental amalgam as a kit, in that both mercury and alloy must be used together to create dental amalgam restorative material. FDA considers the class of the kit to be that of the component of the kit assigned the highest classification. In this case the kit would be viewed as a Class II device because that is the classification of amalgam alloy. No reclassification action would be required. Because the great majority of dentists use pre-encapsulated amalgam, this consolidation would simplify and clarify FDA's handling of dental amalgam submissions.

The Regulatory Work Group feels that reclassification of dental amalgam to Class III should not be readdressed until a body of substantial scientific evidence establishes that dental amalgam restorations are a health hazard. The Research Work Group is charged with developing a list of research objectives and priorities for determining the toxicity and toxic potential of mercury vapor released by dental amalgam. In view of this activity, the Regulatory Work Group believes it is prudent to delay consideration of reclassification of dental amalgam to class III for a reasonable period of time to allow these studies to be carried out. From a practical viewpoint, it would be difficult for amalgam manufacturers to carry out the studies required for premarket approval applications that would unequivocally establish the safety of dental amalgam restorations. The variety of approach and complexity in design required to produce meaningful data would require the cooperation of the public health and scientific communities. If it becomes clear that research directed toward addressing public concerns on the safety of dental amalgam restorations will not be forthcoming, FDA could then reconsider the question of reclassification.

From a benefit versus risk standpoint, the benefit of dental amalgam restorations is clear while the risk has not been established. The Regulatory Work Group is concerned that reclassification to class III at the present time would send a strong message to the public that dental amalgam restorations are dangerous. Without definitive risk information for amalgam and other restorative materials, and as other dental restorative materials are class II devices, it is consistent for dental amalgam to be treated as a class II device.

Determine if current product labeling for amalgams is adequate and identify any needed changes.

As described in 21CFR 807.87(e), Premarket Notification [510(k)] submissions must include "proposed labels, labeling, and advertisements sufficient to describe the device, its intended use, and the directions for its use". In regard to dental amalgam, instructions would inform the user, the dentist, on proper and safe handling of the device to insure the safety of the dentist and dental personnel as well as the patient.

The status of labeling materials for dental amalgam was discussed in a joint meeting between the CDRH Dental Amalgam Task Force and the Regulatory Work Group. A review of labeling material for dental amalgams is underway to establish if current labeling meets current FDA regulatory labeling requirements.

There are other restorative materials which can be substituted for dental amalgam in certain cases. These have been identified and discussed in the CCEHRP Benefits Subcommittee report. The field of restorative dentistry is an ever growing one with new products being developed and marketed daily. The diversity of restorative materials available to the dentist today is vast in comparison to that of a decade ago. Along with this tremendous technological improvement in handling properties that result in better functional qualities, increased longevity of the restoration and improved ease of handling is an increase in the number of potentially toxic materials that are in continuous contact with the oral mucosa. While much attention has been devoted to the potential toxicity of dental amalgam, less has been paid to the vast array of other restorative materials.

On the whole, use of dental restorative materials has not generated significant numbers of reports of adverse reactions. On the contrary, the incidence of side effects from restorative materials is reported to be very low. The most commonly reported problem with these materials is that of sensitivity reaction.

The Regulatory Work Group recommends that, based on currently available information, a statement be placed in the labeling accompanying amalgam and all other restorative materials

1. advising the clinician of possible sensitivity reactions to the material, and
2. if a sensitivity reaction occurs, instructing him/her to discontinue use of that product and to substitute a suitable alternative restorative material.

While definitive information regarding the potential toxic side effects of all dental restorative materials is not yet available, the Regulatory Work Group feels that clinicians should be advised to use barrier techniques as much as possible to reduce inhalation and ingestion of restorative materials that are being placed or being removed. Possible mechanisms for accomplishing this include a statement in the labeling of the restorative material, and education of the clinician through other means. We suggest that the Education Work Group explore this issue.

The Regulatory Work Group further recommends that a comprehensive list of ingredients contained in the labeling of amalgam and other restorative materials be placed on the outside of the package containing the restorative material. By doing so, the clinician would be made aware of the materials he/she is placing in a patient's mouth, and would be better able to make an appropriate selection, and to identify a substitute, when necessary. The clinician would also be able to pass on this information to any interested and concerned patients.

The ingredients should be listed in order of decreasing percent composition (by weight), and include all coloring and flavoring agents. That is, the ingredient present in greatest amount would be listed first. Also, instructions for safe handling and disposal as well shelf life and information on optimal storage conditions should be provided.

Review adverse effects data bases (e.g. Medical Device Reporting system) to determine if any trends can be traced to amalgam use, and work with the Research Group to identify positive avenues for exporting the data to government and private researchers.

It is difficult to assess the significance of the current data base (Device Experience Network) on adverse reactions to amalgam. Publicity on an issue plays a pivotal role in generating reports of incidents. The recent wave of media attention and the resulting public concern to the potential harmful effects of amalgam have resulted, in a short time span, in an accumulation of adverse reaction reports. It is difficult to determine a trend among the numerous ailments that have been attributed to the presence of dental amalgam. Moreover, subtle, and especially delayed, adverse reactions to any material are likely to be under-reported, whereas highly publicized purported effects may be over-reported. A summary of all data collected should be made available to government and private researchers to help them identify key areas for development of clinical studies.

The data collected to date through the Device Experience Network was reviewed in a joint meeting of the Regulatory Work Group and the CDRH dental amalgam task force. It was decided that a letter will be sent to each individual who submitted a report asking that person to allow his/her physician and dentist to release information in his/her medical and dental history. Information such as medication use, family history of illness, allergies, number of dental restorations, types of dental restorative material used, and length of tune restorations were present might be helpful in detecting a commonality among this group of individuals. Documented medical findings before and after dental amalgam removal would be especially useful.

The Regulatory Work Group believes that the dental community as a whole is not familiar with existing mechanisms for reporting adverse effects from dental devices. In order to encourage the reporting of adverse reactions to dental restorative materials, the Regulatory Work Group recommends that a program be developed aimed at publicizing the Medical Device & Laboratory Product Problem Reporting Program (PPRP). We recommend that the Education Work Group develop a plan for educating the dentist, and perhaps the patient as well, about the existence of the program and the importance of reporting an adverse device reaction. It cannot be emphasized enough that it is crucial for FDA to be aware of adverse incidents involving devices in order to develop a meaningful response.

In addition to publicizing the existence of the PPRP, the format of the form and the mechanism by which device reporting forms are distributed deserve review. The form should be user-friendly, i.e., with easy to follow instructions for completion and for return to FDA. The mechanism of distribution is important in capturing the attention of the dentist and the office staff so that when the material arrives at the office, it will not be lost among the myriad of bills, magazines, advertising material and bulk mail.

Investigate the promotional practices associated with alternative materials to identify any illicit/bogus claims that could mislead consumers and/or dental professionals.

The Regulatory Work Group is not aware of unethical practices by manufacturers regarding bogus claims of toxicity from dental amalgam, and the promotion of amalgam removal and replacement by other materials. In a discussion with the American Dental Association (ADA), the ADA representative agreed with this view. Some manufacturers have promoted their products as alternatives to dental amalgam, which they are.

There are reports that some individual dentists are promoting this practice to patients in their individual offices. The present assessment of the ADA is that it is difficult to determine the extent of this activity. Information dissemination on "mercury-free" dental practices, which advocate removal of dental amalgams and replacement with alternative restorative materials, may be through newsletters published by one of several antiamalgam organizations, or by word-of-mouth.

Advertising is considered to be labeling. If individual dentists were participating in false advertising such as claiming that dental amalgams are toxic to humans or causative agents for diseases, and if literature purporting these claims were on the premises of the dentist's office, FDA would have the authority to take legal action against that dentist. However, this situation is unusual in comparison to the more common case of illegal use of a device. In view of this, the Regulatory Work Group feels that it would be more appropriate for this issue to be handled by state licensing and regulating bodies, or by the state professional association, i.e., state dental association. If there does not appear to be a problem, or if the problem is a minor one, states may elect to issue voluntary guidelines. If, however, the problem becomes blatant, and could adversely affect the dental profession as a whole, the state may wish to develop mandatory regulations.

SUMMARY

In summary, the Regulatory Work Group makes the following recommendations:

1. That FDA consider dental amalgam to be a single class II device. This would be accomplished without any reclassification activity, but by regarding dental amalgam as a "kit."
2. That labeling materials include statements about the safe handling and use of dental amalgam, as well as information on the clean-up of spills and proper handling, storage and disposal of waste amalgam.

1. That labeling materials include a list of ingredients contained in the product, in order of decreasing amount (percent composition) including flavoring and coloring agents and (certain) trace contaminants.
2. That labeling materials include a statement advising the clinician to discontinue use of any restorative material that causes a sensitization reaction in a patient, and to substitute a suitable alternative restorative material.
3. That labeling materials include recommendations on storage conditions and expiration date.
4. That efforts be made to make dentists aware of and encourage them to participate in the Product Problem Reporting Program, so that FDA will be aware of problems with dental restorative materials.
5. That the format of the Adverse Device Reporting Form be reviewed and, if appropriate, redesigned with the intent of producing a user-friendly format, and that the distribution mechanism be re-evaluated to insure that the existence and the importance of the program receive the attention of the dental community.
6. That the body of data on dental restorative material that has been compiled through the Product Problem Reporting Program be made available to any interested party to aid in directing research efforts.

October 22, 1990

The Food and Drug Administration has reviewed recent research performed in sheep in which it was shown that small amounts of mercury vapor could be released from dental amalgams and absorbed into various organs of the animal's body. Although laboratory studies of this kind are useful in that they raise preliminary questions about the safety of dental amalgams, they also leave other important questions unanswered. For example, because of basic differences in the anatomy and physiology of sheep and humans, it is unknown whether similar levels of mercury would be released in the human mouth, or whether human organs would absorb the released mercury in the same way as sheep. Assuming that a minute amount of mercury may be released from dental amalgams in humans, the question remains as to how much is released and absorbed, and, more importantly, whether this amount of mercury has any bearing on human health.

Until these questions are answered and we have reasonable evidence that dental amalgams actually can be harmful to health, we cannot take action against these products, particularly in light of the value they provide in dental care. In order to get the answers concerning potential risk we will continue to monitor and evaluate the international research in this areas (including yet-unpublished studies which have been cited in the news media concerning fetal exposure to mercury from the mother's dental amalgams). We will also raise the issue of possible hazards from dental amalgams at the next meeting of our Dental Products Panel, an advisory committee of outside experts, and get their recommendations.

If research shows that the use of dental amalgams can pose a risk to patients, FDA has several options, including removing them from the market. But we cannot exercise these options without sound scientific evidence that there is a risk.

December 1990

Historically, dental caries has been the most widespread disease known to mankind. For over 150 years, dental amalgam has been the principal restorative material used to treat dental caries and restore patients to good oral health. As a result, many people today retain their natural dentition. Without the benefit of amalgam restorations, they would be partially or completely without their teeth. Throughout its use, there has been considerable scientific study of amalgam and no documented evidence to support the contention that amalgam, or the mercury contained in amalgam, has any deleterious effect on the health or physical well-being of the millions of patients served throughout the world.

The dental profession is committed to providing the best service to the public in a safe manner at a reasonable cost. At the present time, available alternative materials are either significantly more costly or have so far failed to demonstrate comparable strength, durability, or compatibility in the oral environment.

Banning dental amalgam would be financially advantageous to dental practitioners, since its replacement would necessitate the use of other, more costly materials and procedures. It also would be a disservice to those patients who would be denied the benefits of dental care because of prohibitive cost. Any replacement of existing amalgam restorations would be both costly and impose considerable risk to otherwise healthy teeth. The ADA thus continues to believe that dental amalgam should remain available as a safe and effective treatment.

The dental profession is committed to continuous improvement in the delivery of oral health care. During the past 50 to 75 years when dental caries was extremely common, massive amounts of amalgam were used to restore teeth. During the early years, the mercury-to-alloy ratio of amalgam was in the range of eight parts of mercury to 5 parts of other materials, compared to its current formulation of much less than 1:1. During that period, because caries was so prevalent and technology was still in its infancy, cavity preparations were large and extensive amounts of amalgam were used in each preparation, with no evidence of deleterious effect on the health or physical well-being of patients. Today, it is even less likely that any such effect would be seen. Dental decay has declined significantly, as evidenced by the fact that nearly half of Americans achieve the age of 17 without experiencing any dental caries. Technology has improved as well; preparations are more conservative and alloys with much lower mercury content are now being used routinely. As a result, the amount of amalgam used today is but a fraction of that used as recently as 15 years ago.

The ADA has consistently supported research in the development of new materials that will equal or exceed the benefits of amalgam at a cost that will not be prohibitive to the average person.

The ADA has also welcomed over the years the considerable research that has been done on dental amalgams. Overwhelmingly, this research has led the scientific community to support amalgam as a safe restorative material. The research currently creating interest and controversy has been found by the scientific community to have considerable shortcomings in methodology and to be totally inconclusive as to any detrimental health ramifications for humans.

The ADA will continue to support further scientific inquiry and welcomes the amalgam review planned by the Food and Drug Administration and the materials safety workshop scheduled by the National Institute of Dental Research (NIDR). The ADA further strongly urges NIDR to fund the grant proposal pending for a major epidemiological study of humans with dental amalgams.

Based on the research and epidemiological evidence available to date, the ADA continues to support dental amalgam as a safe and effective restorative material and sees no cause for public concern about either existing or future amalgam restorations.

June 1988

At present, there are no scientific data indicating that exposure to mercury from dental amalgam causes symptoms of poisoning. The National Board of Health and Welfare's group of experts, however, underlined that amalgam is an unsuitable dental filling material from a toxicological point of view. The development should be stimulated of new dental filling materials which are technically and biologically toxicologically satisfactory. While waiting for such materials to become available as general replacement for amalgam, amalgam may therefore still be used as dental replacement material.

On the other hand, the Board of Health and Welfare is of the opinion that treatment of pregnant women with amalgam should be avoided as far as possible. This judgment has been passed awaiting further research into disorders of the reproductive system related to exposure to mercury.

Dentists shall always inform the patient about possible alternatives and take notice of the patient's right to refuse certain treatment.

The Board of Health and Welfare recommends that all handling of mercury and mercury compounds be done in such a way that both individual exposure and contamination of the environment is reduced to the lowest possible level. The use of amalgam should be gradually decreased. Alternatives like composite materials or glass ionomer cements are today considered the best when reparative treatment of small caries lesions is carried out. These alternatives should be used as far as possible in such treatment and also in other cases where it is considered indicated and when for various reasons other alternatives cannot be applied.

Polishing of and drilling in amalgam should always be done with water cooling and by using high-speed water evacuation in order to reduce exposure to mercury vapour.

Patients who have developed contact allergy against mercury should have their existing amalgam fillings exchanged for other material. This also applies to patients with lichen planus or lichenlike reactions in connection with amalgam fillings.

These general recommendations will be renewed as and when further research results appear.

The National Board of Occupational Safety and Health will publish recommendations on how to handle amalgam and mercury at dental clinics.

1992

The manufacturers' instructions for the use of amalgams by dentists are to be changed by order of the Federal Public Health Office according to latest scientific findings. From now on, amalgams are to be used solely for areas exposed to mastication (molar teeth). Additionally, only gamma-2-free amalgams are to be used. The Federal Public Health Office intends to call back the approval for gamma-containing amalgams, mainly because of the poorer quality of these materials.

The Federal Public Health Office has worked out guidelines for the use of amalgams under the newly specified conditions in dental therapy. These guidelines provide answers to the most important questions and are available to the public. The guidelines are addressed to dentists, patients, and general practitians likewise. The guidelines come in an information booklet with the title: "Amalgams in Dental Therapy" and can be requested at no charge from "Institut fur Arzneimittel des Bundesgesundheitsamtes" Seestrasse 10, W-1000, Berlin 65.

According to the latest status of scientific knowledge no reasonable suspicions that amalgam fillings are hazardous to one's health can be established from a medical point of view if one considers the already existent burden of mercury through a person's daily intake of mercury with food, water and air. Nevertheless, the use of amalgams is to be decreased as much as possible in order to reduce the strain on the human body caused by general mercury intake.

In the opinion of the Federal Public Health Office, amalgam is a means for operative dentistry on molar teeth (areas exposed to mastication) only. The Federal Public Health Office recommends the use of alternative materials for front teeth or areas that are not mainly used for mastication. Which one of the alternative materials is to be chosen depends entirely on the individual medical situation. This question should be settled between dentist and patient.

The Federal Public Health Office does not recommend to substitute already existing filling by other filling materials, unless the individual medical situation, e.g., an allergic reaction, requires that.

Patients with kidney problems should not have their cavities filled with amalgarns. Also, the use of amalgams should be very carefully considered for children under the age of six, especially up to three years, since the sensitivity to mercury is said to be highest at early age.

As already recommended in 1987 by the Federal Public Health Office, no major dental procedures involving amalgams should be done during pregnancy. Even though there are no reasons to believe that amalgams could be hazardous to the health of the unborn child, the Federal Health Office asks to observe this recommendation in the interest of preventive medicine.

By financially supporting scientific projects dealing with amalgams' potential hazards to the human health, the Federal Public Health Office has helped to gain new scientific knowledge in this matter.

Even in comparison to other comparable countries, these new recommendations for the use of amalgams in Germany represent a considerable restriction. The new recommendations are in substance being supported by the Pharmaceutic Commission of Dentist. The elimination of the use of amalgams provides that alternative filling materials are available. The Federal Public Health Office thinks that priority to research in this particular field is extremely necessary especially on the part of pharmaceutical companies.

1.0 - Safety of silver amalgam:

Silver amalgam (an amalgam of mercury, silver, copper and tin) has been used in dentistry for over 150 years as a safe and effective restorative material to replace lost tooth structure. Experience with this material has extended for over 150 years. Notwithstanding the mercury component of silver amalgam, extensive reviews of the scientific literature have not revealed any data published in refereed scientific journals to support claims that amalgam restorations have caused any adverse biological reactions other than extremely rare allergy to one of the amalgam components. Localized lichenoid reactions of the oral mucosa may occur adjacent to amalgam restorations similar to reactions which may occur adjacent to any restoration.

2.0 - Risk of mercury hypersensitivity:

It is recognized that a very small proportion of the population may have an allergy attributable to mercury and only very few of these individuals react to amalgam restorations. Such an allergy needs to be demonstrated by recognized methods by a specialist allergist. Biological reaction to mercury is most likely to be seen as oral (lichenoid) lesions adjacent to silver amalgam restorations.

Where a hypersensitivity to mercury can clearly be demonstrated by accepted means placement of silver amalgam restorations should be avoided. The use of mercury detectors for routine measurement of mercury vapour is not advocated as a standard test for mercury toxicity. Galvanic current measurement techniques are not an accepted method for the purpose of testing for toxicity at a cellular level.

3.0 - Mercury sources:

Mercury intake occurs from sources which include mercury in air, and from industry, dentistry and some medications. Mercury occurs in three forms.

3.1 Elemental mercury

Exposure to elemental mercury is usually occupational and arises from vapour inhalation. Mercury vapour is almost completely absorbed and oxidized to the inorganic forms.

3.2 Inorganic mercury

Particles of silver amalgam are inorganic mercury compounds. Inorganic mercury if ingested, is poorly absorbed from the gut. It is present in some food and medications. Following reaction with the gastric juices absorption occurs, however, such mercury tends to remain in the inorganic state whereby it is readily excreted in urine. There is no significant conversion of inorganic to organic mercury compounds in the body.

3.3 Organic mercury

Organic mercury, which is highly toxic, orginates from food, particularly seafood from contaminated waters. Organic mercury may also originate from some pesticides and agricultural herbicides. Organic mercury is readily taken up by the body. Inorganic mercury is not converted to organic mercury in the body in significant amounts.

4.0 - Food as a source of mercury:

There is a substantial intake of mercury from food, mainly fish and seafood. The contribution to the body burden of mercury from silver amalgam restorations is relatively small in comparison with that from regular food sources. Further, the amount of mercury exposure due to silver amalgam does not appear to be hazardous.

5.O - Dental clinical personnel and occupational exposure to mercury:

Dental clinical personnel when using silver amalgam should exercise proper procedures to avoid personal contact with mercury. Precautions should be taken to avoid exposure to mercury vapour in the dental environment and waste amalgam should be collected for disposal in a manner which will protect those who handle the waste, and the environment.

6.0 - Replacement of amalgam restorations not justified:

Replacement of silver amalgam restorations is not justified except when the restoration has failed; where it has fractured; where there is recurrent dental caries at its margin; where access to the dental pulp is needed; or where there is clearly-established case of mercury hypersensitivity associated with clear evidence of an adverse effect from an amalgam restoration.

The Food and Drug Administration of the United States of America in a statement made in March 1991 advises individuals against having their amalgam restorations removed.

7.0 - Silver amalgam alternatives:

Where alternative restorative materials to silver amalgam are used, consideration must be given to their potential adverse effect, both local and systemic, and also to the physical properties needed to meet the requirements of a dental restorative material.

8.0 - Materials research:

Research into and development of dental materials which could be used as alternatives to amalgam should continue and be encouraged.

9.0 - The invasive nature of all restorative procedures:

No restoration of a damaged tooth is made without inconvenience and some risk however slight. Restoration of teeth is an invasive procedure, and there are risks, however slight, associated with restorative materials and their manipulation, and with drugs such as local anesthetics required for the restorative procedure. As well, restoration of tooth structure lost through dental decay, trauma, or other causes, requires a lifelong commitment to maintenance of the restoration

10.0 - Dental caries prevention reduces need for restorations:

Where preventive dentistry programs with fluoridation of public water supplies have been employed, they have greatly reduced dental decay. Any risk that could arise from dental restorative materials or techniques used for their placement is thus lessened by reduced dental caries through preventive means such as fluorides and sealants. The role of noninvasive treatment of early carious lesions in reducing the need for restorations is also recognized.

December 1992

During the 1950s and 1960s, the world began to recognize the consequences of uncontrolled release of mercury into the environment. The most widely known episode, involving release of large quantities mercury into Minamata Bay Japan, from 1953 through the early 1960s caused methylmercury poisoning in hundreds of people who ate seafood from the bay. Later Sweden, other European countries, and the United States identified significant mercury releases from chloralkali plants and pulp-paper plants. Since the early 1970s various countries have made continuing but inconsistent effort to reduce the release of mercury into the environment.

Draft order for the discontinuation or mercury use in Denmark

In June 1989, the Danish government issued a draft order that would ban the import and sale of mercury and products containing mercury. The order included several deadlines for discontinuing the use of mercury and mercury compounds, including the use in oral thermometers, on seeds, in laboratories, and in dental amalgam.

However, because officials did not reach a policy decision concerning the draft order these deadlines have passed without compliance. Dental amalgam reportedly accounts for the single largest use of mercury in Denmark. (Grandjean, Phillipe, Institute of Community Health, Odense University, Odense, Denmark, personal communication November 3, 1992.)

Consideration of discontinuation of mercury use - Sweden

For environmental reasons, within the last year the Swedish Parliament approved a general plan to discontinue the use of mercury in that country. The National Chemical Inspectorate (NCl) and the Swedish Environmental Protection Agency (SEPA) developed suggestions about how the discontinuation should take place region by region. The government commissioned the National Board of Health and Welfare to study the requirements for discontinuing the use of mercury-containing amalgam for dental restorations. Although dental amalgam is but one use of mercury that contributes to the release of mercury into the environment, as other uses of mercury are curtailed, the mercury used in dentistry will account for a larger fraction of the total mercury released. In Sweden, the SEPA estimates that about one-third of the mercury found in waste-water sludge now comes from dental amalgam.

The investigation team of the Swedish National Board of Health and Welfare was asked to outline a possible stepwise plan for discontinuing the use of dental amalgam. The fist step is to discontinue the use of amalgam in children's temporary teeth after July 1, 1993. The second step is to discontinue the use of amalgam in the permanent teeth of children and teenagers up to the age of 19 after July 1, 1995. The plan also emphasized the potential side effects and increased costs of the alternative materials. It was also recognized that the need for amalgam restorations in these age groups of the Swedish population are minimal.

The investigation team also believed that the use of amalgam fillings could possibly be stopped for adults starting in 1997. Before such a decision is made, however, the team recommended that the effects of amalgam use and the costs of available alternatives should be evaluated. The team also recommended assessing to what extent future dental care insurance will allow patients to choose a more expensive alternative. A decision about whether to discontinue the use of amalgam restorations for adults should be made in 1996.

Environmental contamination - United States

Within the last 10 years, fish samples from some lakes and streams around the United States have shown concentrations of mercury sufficient for the responsible state agencies to issue fish advisories. According to results of a 1989 survey, 33 states had issued fish advisories because of heavy metals, 17 because of mercury. Since that time, at least three other states have issued fish advisories because of mercury contamination and another is in the process of writing such an advisory. Initial evaluations of the fish data led to a theory that the mercury contamination of fish was caused by acidification of the water from acid deposition with resulting release of mercury from the soil. However, as the mercury contamination of fish was observed increasingly around the country, it was thought that the problem was not due to acid deposition but primarily to mercury deposition. One example is illustrated by the State of Michigan Department of Natural Resources, June 24, 1992, draft report entitled, "Mercury in Michigan's Environment: Causes and Extent of the Problem" which gives an estimate of air emissions of mercury in Michigan for 1989. The contribution of dental mercury was about 1.8 percent of the total.

Efforts to reduce release of mercury -United States

Within the last several years, the U.S. Environmental Protection Agency (EPA) has become concerned about the release of mercury into the environment. As a result, EPA, together with the manufacturing industry, established a voluntary program for waste release reduction known as the 33/50 program. Its goal is to reduce the discharge of mercury and 16 other chemicals 33 percent by 1992 and 50 percent by 1995. These reductions are from base levels established by the 1988 toxic release inventory (TRI) data. Data from the Environmental Protection Agency show that mercury disposal in United States increased by more than 65 percent from 1970 to 1989 (1). That data also show that efforts to reduce the use and disposal of mercury projects a more than 75 percent reduction in mercury disposal by the year 2000. Disposal of mercury from the use of dental amalgam is projected to account for about 1.3 percent of the total for the year 2000, about the same percentage as in 1980.

In Title III of the Clean Air Act Amendments of 1990, section 112(n)(1)(B), Congress mandated that the Administrator of EPA,

"shall conduct, ... a study of mercury emissions from electric utility steam-generating units, municipal waste-combustion units, and other sources, including area sources. Such study shall consider the rate and mass of mercury emissions, the health and environmental effects of such emissions, technologies which are available to control such emissions, and the costs of such technologies."

EPA has until November 1994 to complete the study and deliver the report to Congress. Future legislation and regulation, if any, will depend upon the findings of this study.

Amalgam's contribution of mercury to body burden

Most data suggest that the daily mercury dose is 1 to 5 µg higher for subjects with 7 to 10 amalgam dental restorations than for persons with none. Clarkson and colleagues (2) estimated that for the general U.S. population "the dominant exposure (for elemental mercury) is to mercury vapor from dental amalgams." In low-level occupational exposures, the subclinical health effects detected have occurred in groups with mean tissue mercury levels that are 10 times higher than those of the general population; however, the relationship between the observed effects and the tissue levels is not clear.

German and Swedish recommendations on amalgam use during pregnancy

In 1987, Gennany's Federal Health Agency (Bundesgesundheitsamt, BOA) recommended that major procedures involving amalgam restorations should not be done during pregnancy. In 1988, the National Board of Health and Welfare of Sweden recommended that if possible, amalgam should not be used in the treatment of pregnant women. Neither of these pronouncements was based on medical evidence of reproductive health effects in humans. Rather, they were based on two observations: 1) that inhaled mercury vapor crosses the placenta and 2) that there is a 1-month spike in mercury concentration in the blood of a patient who has had an amalgam restoration placed or removed. Thus, these recommendations were made so as to prevent subjecting the child to an additional mercury exposure during the time of greatest development. It should be noted that the pregnancy restriction was recommended to be reversed by the Swedish Medical Research Council, April 1992, because of lack of scientific evidence. (Sundberg, Hans, Chief Dental Officer, National Board of Health and Welfare, Stockholm, Sweden, personal communication, November 3, 1992) It is generally considered prudent practice in dentistry and medicine to limit most drugs or extensive procedures during pregnancy because of the unknown effects on the developing child.

Restriction on use of amalgam -Germany

Early in 1992, the BGA developed guidelines for the use of amalgam. One of these withdrew gamma-2-amalgam from the market because of its poorer physical properties (gamma-2-amalgam is not used in the United States). Another requires manufacturers' instructions to dentists to limit amalgam's use solely to tooth areas exposed to mastication. While issuing the new guidelines, the BGA stated:

"According to the latest status of scientific knowledge, no reasonable suspicions that amalgam restorations are hazardous to one's health can be established from a medical point of view if one considers the already existent burden of mercury through a person's daily intake of mercury from food, water, and air." (3)

The reason given for the limitation imposed by the new guideline was:

"...the use of amalgam is to be decreased as much as possible in order to reduce the strain on the human body caused by general mercury intake." (2)

Conclusion

The European countries that have proposed or recommended restrictions on the use of dental amalgam have done so in an effort to diminish both human exposure to and environmental release of mercury and not because of any documented health effect associated with exposure to dental amalgam.

There are no credible scientific studies which show that exposure to mercury from amalgam dental restorations causes disease in humans, other than allergic response in a small segment of the population.

In studies of low-level occupational exposures, the subclinical effects detected have occurred in groups with mean tissue mercury levels that are only 10-fold higher than those of the general population; however, the relationship between the observed effects and the tissue levels is not clear.

Significant efforts are under way in the United States to reduce the amount of mercury released into the environment. These efforts may intensify following EPA's report to Congress due in November 1994.

Based on experiences with lead exposure, it would be prudent to minimize human exposure to all heavy metals—including mercury. With the efforts under way to reduce mercury use and disposal, the continued use of mercury in dental restorations -will account for an increasing percentage of the total exposure to mercury for those with amalgam dental restorations. However, its health significance may decline as reductions in other environmental mercury exposures results in a decline in overall mercury exposure.

Amalgam has been used in the United States for 150 years and has been used in over 100 million dental restorations per year for the last 20 years or more, with no scientifically documented health effects, except allergic reactions affecting a small segment of the population. This lack of documented health effects cautions against a hasty decision to replace amalgam with alternative materials about whose potential health effects from long-term, low-level exposure are not well documented.

Because no credible scientific studies show that exposure to mercury from amalgam dental restorations causes disease in humans, except for allergic reactions affecting a small segment of the population, there is no health-based reason for the Public Health Service to restrict the use of amalgam for dental restorations.

In order to reduce human exposure to mercury from dental amalgam restorations, the U.S. Public Health Service is implementing an expanded and targeted research program to develop alternative dental restorative materials for which we understand the health consequences of long-term, low-level exposure.

References

1. Palmer C. Amalgam declining as a source of Hg in Trash, American Dental Association News, 1992 Oct 5: page 12, col 1.

2. Clarkson TW, Hursch JB, Sager PR, Syversen TLM. Mercury. In: Clarkson TW, Friberg L, Nordberg GF, and Sager PR, ed. Biological Monitoring of Toxic Metals. New York: Plenun Press, 1988: 199-246.

3. Translation of the announcement in BGA Pressedienst, February 5, 1992.

PREFACE

Silver-containing amalgam is a common and efficacious dental material used to restore the function of posterior teeth. However, during the last decade the possibility of adverse effects on health resulting from exposure to dental amalgam has been raised and the issue has been discussed intensively both by the profession and the public.

The Swedish Medical Research Council has since 1989 given "ear-marked" grants to research on amalgam and other dental restorative materials.

During April 9-10, 1992, the Council held a State-of-the-Art Conference in Stockholm on the subject. The conference, entitled "Potential biological consequences of mercury released from dental amalgam", brought together scientists from various fields who, for two days, presented papers and discussed the subject in plenary sessions. On April 11 all the speakers were interviewed by a scientific panel appointed by the Swedish Medical Research Council.

The panel consisted of professor OD Bo Bergman, chairman, Umea Univesity, professor MD Harry Bostrom, Uppsala University, professor OD K. Sune Lawson, Karolinska Institute, Huddinge and professor Dr. Odont, director Harald Loe, National Institutes of Dental Research, Bethesda, Maryland, USA.

The panel weighed and analyzed the scientific evidence and responded to ten questions, which are presented in this document. The proceedings from the conference will be published separately.

Stockholm, June 1992
Tore Schersten
Secretary General
Swedish Medical Research Council

1. How is mercury released from dental amalgam?
2. Are there problems in determining small amounts of mercury in biological fluids and tissues?
3. Are there data demonstrating that mercury released from dental amalgam gives rise to, or contributes to, toxic systemic effects?
4. Are there data demonstrating that mercury released from dental amalgam may cause effects on the immune system in man?
5. Does silver amalgam cause systemic or local allergic reactions?
6. Will mercury released from dental amalgam give rise to teratological effects?
7. Are there data supporting that mental and psychosomatic disorders are potential side-effects of dental amalgam?
8. Have general or local side-effects been attributable to alternative restorative materials?
9. Is mercury in dental amalgam an environmental hygiene problem?
10. Do available justify discontinuing the use of dental amalgam or recommending replacement?

The answers to these questions, and the conclusions of the conference are contained in this report to the Swedish Medical Research Council.

Question 1: How is mercury released from dental amalgam?

Mercury is mainly released from dental amalgam in the form of elemental mercury (Hg°) vapour. This mercury vapour dissolves in the intra-oral air or in saliva and enters the organism via different routes. Mercuric ions (Hg2+) produced through electrochemical corrosion may also be released into saliva, bind to organic saliva components, and be swallowed. Fine powder particles of amalgam which might be introduced into oral mucosa during clinical operations can also undergo corrosion.

Finally, mercury can be released from amalgam particles which have been swallowed. Such pieces or particles may be dislodged during mechanical wear of amalgam fillings or produced during placement or replacement of amalgam fillings.

Vapour

Inside an amalgam filling, mercury diffuses towards the surface of the filling where a concentration gradient of mercury prevails. This concentration gradient is the apparent source of mercury. It can be distributed by various processes in the oral cavity such as the chewing of chewing-gum or tooth-brushing, resulting in an increasing mercury release rate, and it can also be passivated resulting in a decreased release rate. The diffusion process inside the amalgam filling, however, cannot be influenced by any variable other than temperature. Since the temperature in the oral cavity is relatively constant over time, this cannot appreciably change the diffusion process. Thus, the degree of diffusion of mercury within the amalgam fillings is the factor determining the rate of mercury release. The release of mercury vapour from amalgam fillings has been measured using a variety of methods. Based on such data the daily uptake, or daily dose has been calculated considering varying mouth to nose breathing ratios. Published results indicate that most of the mercury vapour released from amalgam fillings is mixed/dissolved in saliva and swallowed, while part of the mercury vapour is inhaled and exhaled respectively. The lungs absorb 80% of the inhaled mercury vapour.

Electrochemical corrosion

No reliable in vivo data exist on the degree of electrochemical corrosion of amalgam fillings. Indeed it has been questioned whether electrochemical corrosion of mercury from amalgams in the oral cavity even occurs. Theoretical data on charge transfer-potential measurements suggest that initially the metals zinc (in the zinc-containing amalgams) and tin are the corroding metals. As these metals dissolve, mainly the mercury-rich and the silver-rich phases remain, a situation which should further the release of mercury. Furthermore, in situations where the amalgam fillings are in contact with other metallic restorations electrochemical corrosion of mercury may occur, thereby producing mercuric ions (Hg2+). Mercuric ions in saliva will not remain as ions, but will chemically bind to saliva components, and be swallowed together with the saliva. Approximately 5-10%of the mercury from mercuric mercury salts ingested is absorbed, the remainder being excreted in the feces.

Particulate matter

The amount of mercury available from swallowed amalgam particles varies widely. Besides particles which are swallowed during clinical operations most of the particles are dislodged from incompletely condensed fillings and from amalgam surfaces undermined by heavy corrosion. Subjects with bruxism may release bigger and greater amounts of amalgam particles, varying to some degree with the extent and duration of the bruxism. The absorption of metallic mercury in the gastrointestinal tract is very small.

Studies in rats have shown that less than 0.01% is absorbed this way.

Considering all known forms mercury uptake and routes of absorption a patient with an average number of amalgam surfaces, 20-30, will have a daily uptake of no more than 10 µg mercury from these amalgams.

Question 2: Are there problems in determining small amounts of mercury in biological fluids and tissues?

Since the amounts of mercury vapour are small and the concentrations of mercury in body fluids and tissues are low and despite the fact that a number of reproducible and sensitive methods are available, the determination of mercury in tissues and fluids is associated with great difficulty. It is, therefore, of great importance that sampling methods and laboratory procedures be meticulously controlled to avoid contamination of mercury from air, water and other sources, as well as preventing mercury from adhering to sampling equipment, vessel walls, glassware, etc. which may jeopardize the assay.

The analytical procedures should be scrutinized and monitored continuously and internal and inter laboratory control programs should be maintained. Such programs do exist, and new laboratories are urged to adopt them.

Measurement of mercury content of body fluids is generally easier to standardize than measurement of mercury in the various tissues of the body. Also, it should be emphasized that assessments based on mercury content in hair from the scalp or the pubic region are of questionable validity, because values derived from such analyses do not reflect the amount of mercury released from dental amalgam.

A critical review of the methods and procedures used to determine the mercury content of tissues and organs in some human studies—even in many that are often cited—suggests that the results are ambiguous, inaccurate and sometimes false. For these reasons the conclusions drawn from such studies are severely impaired and at times completely useless.

Question 3. Are there data demonstrating that mercury released from dental amalgam gives rise to, or contributes to, toxic systemic effects?

Although mercury is known to be a weak allergen and allergic reactions may occur (see Question 5) no evidence exists of systemic toxic effects from mercury released from dental amalgam.

In Swedish clinical studies, including large numbers of individuals claiming to suffer from various somatic symptoms and diseases caused by amalgam, the patients were subject to detailed medical and dental examinations and follow-up for several years. None of these studies support the view that the complaints of the patients studied were related to the presence or the number of amalgam fillings.

Even the number of case reports published in scientific journals dealing with individual patients suffering from various symptoms ascribed to toxic effects of amalgam, and who claimed relief after removal of the amalgam fillings, is very small. This fact is especially important in view of the many millions of patients all over the world who have had their teeth restored with amalgam.

Kidney dysfunction following severe industrial occupational exposure to mercury has led to speculation of a similar role for mercury from dental amalgam. It should be noted that the exposure to mercury in these industrial workers was extremely high compared with the levels produced by vapour from amalgam fillings. There are currently no scientific data to support the hypothesis that mercury from dental amalgam causes disturbance of kidney functions in humans. Moreover despite the great interest devoted to clinical research on kidney function in recent decades, no observations on the existence of a relationship between mercury from amalgam and kidney function have been made.

Neurological diseases such as multiple sclerosis and amyotrophic lateral sclerosis have also been alleged to be caused by mercury released form dental amalgam. However, it must be emphasized that there is no evidence for the existence of such relationship.

Epidemiological studies in Sweden have not revealed that amalgam fillings are a risk factor for cardiovascular disease, diabetes mellitus, cancer, or early death.

Question 4: Are there data demonstrating that mercury released from dental amalgam may cause effects on the immune system in man?

Mercury compounds, as happens, require conjugation to a carrier to be able to induce a specific immune response. Intravenous injections with mercury chloride (HgCl2) have been found to polyclonally activate T and B cells in vivo as evidenced by increased proliferation and polyclonal antibody synthesis including a variety of auto antibodies. These effects have been induced by mercury in doses as low as 50-100 µg /100 g body weight given at various times. However, mercury chloride can only induce polyclonal T-cell activation in a very restricted number of rat and mouse strains. Mercury chloride appears to be unique among known polyclonal T-cell activators in its requirement for certain genes in the MHC region.

The interest has been focused on certain auto antibody specificity's such as anti-DNA antibodies, antibodies against glomerular basement membrane and immune complex mediated glomerulonephritis. However, in contrast to other known polyclonal B-cell activators, HgC12 induces disease. Most likely, the immune complexes and the antiglomerular basement antibodies are responsible for the development of certain kidney disorders such a proteinuria and nephrosis, but no renal failure develops. These auto immune manifestations require the presence of T-cells, and only occur in certain animal strains, Brown Norway rats and A. SW mice are the most susceptible to disease induction by mercury. It has been shown that the susceptibility genes were localized to the MHC region. also, in humans many auto immune diseases are under HLA-control, but no HLA-controlled specific reactivity to mercury has been found. The mechanism by which mercury can induce auto immunity is not known.

There are few studies on the effect of mercury on the immune system in humans. Mercury has been used therapeutically in various disorders and there are reports on mercury-induced membranous glomerulopathy and glomerulonephritis. These might be due to immunological reactions. Immunological reactions to mercury have been found in man and skin testing has been the most common method to evaluate hyperactivity to mercury in exposed individuals. Severe allergic reactions have been observed in people exposed to mercury ointments and mercury vapour. Some workers exposed to metallic mercury have developed nephritic syndrome and the disease has had immunological components, such as deposits of immunoglobulin and complement in the glomeruli.

Studies on possible immunological effects of mercury in silver-amalgam are few. In one study it was found that dental students showed a higher incidence of positive skin tests to mercury with longer exposure time. In another report, dental students were shown to have a higher frequency of certain sub populations of blood T cells, which has been used as a sigh of "immunoactivation." However, there is no link to specific reactivity to mercury, rather non-specific, possibly inflammatory reactions are involved. Finally, skin tests have also been performed in a study in patients with lichenoid oral mucosal lesions and in patients with burning mouth syndrome without lichenoid lesions. In one report reactions to mercury were found in one third of the patients with lichenoid lesions, but not in patients in the other two thirds. However, another study on patients with similar symptoms used biopsies from affected areas in contact with amalgam and in areas not in contact with amalgam and failed to find any differences with regard to lymphocyte sub populations or signs of immune activation.

In summary, there are no data to support the idea that the mercury from amalgam fillings is responsible for auto immune disease or kidney lesions in man, or that mercury from amalgam fillings negatively affects the immune system.

Systemic reactions to mercury from amalgam, such as urticaria and asthma, seem to be extremely rare, this is also true for delayed type IV-reactions. Contact dermatitis caused by amalgam fillings has been reported in the scientific literature in less than 100 patients. Other constituents of the amalgam than mercury may also be responsible for these reactions. Hypersensitivity demonstrated by patch tests might be derived from other sources of mercury, such as preservatives in vaccines, drugs and cinnabar in tattoos.

The incidence of local allergic reactions also appears to be low. Lichenoid oral mucosal lesions in contact with amalgam fillings do occur, and skin tests of such patients with various test antigens have, in some cases, shown hyperactivity to mercury compounds. On the other hand, studies of lichenoid lesions or normal mucosa in contact with amalgam fillings have revealed no differences in lymphocyte reactivity or in the availability of specific rnarkers in lymphocytes. When such lichenoid reactions occur, they can be eliminated by the removal of the restoration.

In summary, very few patients appear to be at risk of developing systemic or local allergic reactions in response to the placement of amalgam fillings.

Question 6: Will mercury released from dental amalgam give rise to teratological effects?

A Polish study has claimed that a significant positive correlation exists between the mercury concentration in the hair of female dental personnel with occupational exposure to mercury and their history of reproductive failures. Information obtained from the main author in 1991 revealed that the hair was assessed for mercury in 1985-86, but that the five children with spina bifida were born in 1968, 1972, 1977, 1980 and 1982. It must be emphasized that the hair samples only represent the mercury levels at the time of assessment and cannot be representative of pregnancies prior to that time. Both the methods of establishing the amount of mercury in the bodies of these women and the design of the study suggest that the results are highly questionable.

Other studies on female dental personnel have not revealed any difference in the rates of birth defects or spontaneous abortion. Adverse effects, such as decreased libido and fertility in men and menstrual disturbances and spontaneous abortions in women have been reported in industrial workers exposed to metallic mercury vapour. However, this occupational exposure was extremely high compared to that from amalgam fillings, and the results are irrelevant.

Since elemental mercury passes through the placenta, it has been inferred that mercury vapour released from dental amalgam is a potential hazard to the fetus. The concentration of a teratogen at the target tissue is determined not only by the dose and the rate of placental transfer, but also by other factors such as distribution within the mother, affinity to the fetal liver and blood, the hematocrit value and the passage through the ductus venosus. These factors might explain the toxicological mechanisms and species differences, and must be considered if the results of animal experiments are to be extrapolated to human conditions. It should also be emphasized that although measurable amounts of mercury may be incorporated in certain fetal organs, this is not evidence of a toxicological or teratological effect per se.

As an indication of human fetal exposure, the mercury concentration in cord blood and maternal blood gives a fetal to mother-ratio (F/M ratio) slightly over or close to one as 14 studies have revealed. The observation that in sheep the F/M ratio of blood-Ha in late gestation exceeded one and was in fact as high as four, has attracted a great deal of attention, but this might indicate a species peculiarity in handling elemental mercury. It has been shown that in the guinea pig elemental mercury is readily oxidized and accumulated in the fetal liver, and consequently little is distributed to other fetal organs. Also, postnatally this mercury, temporarily trapped in the fetal liver, helps to reduce exposure and avoid concentration peaks in other, more vulnerable, organs such as the brain.

Organic and inorganic mercury concentrations in human fetal brain and liver have been determined. In the brain the total mercury concentration in five fetuses ranged from 7.1-65.0 ng/g, but inorganic mercury was detected in only one. In four fetuses the total mercury concentration in the liver ranged from 26.1-89.8 ng/g and the inorganic fraction ranged from 27.2-59.9%. Pregnant women derive organic mercury from the diet. Those with amalgam restorations may, in addition, take in metallic mercury vapour from the fillings.

Restriction of amalgam therapy during pregnancy has been advocated on the grounds that the insertion of removal of amalgams causes an acute peak exposure to mercury vapour. Available scientific data do not support such a restrictive policy.

Question 7: Are there data supporting that mental and psychosomatic disorders are potential side-effects of dental amalgam ?

Available data suggested that in patients who perceive that they suffer from mercury intoxication, the symptoms are mostly of low or moderate grade, but severe enough for the patients to feel sick. Neurotic symptoms dominate with a mixture of anxiety, depression and asthenia. Probably these symptoms also explain the mandibular dysfunction's which increase the level of anxiety in vicious circles. Although in the general population there is a relationship between the number of amalgam surfaces and mercury levels in plasma and urine, the levels are far below those found in workers in the mercury industry, and also lower than those in dental personnel.

Studies have demonstrated that the mercury levels in plasma and urine are very similar in patients who believe they are mercury intoxicated and in control subjects with the same number of fillings. This does not support the hypothesis that the mental are caused by mercury. In fact, no relationship between the mercury levels and severity of mental symptoms has been established in scientific studies.

The focus on the amalgam problem may give these patients an immediate and transient relief from their anxiety and depression. However, such patients need a thorough medical, oral, psychological and social examination and counseling to address the core problems of their lives. The current health care system has not always been successful in managing these patients' problems.

Question 8: Have general or local side-effects been attributable to alternative restorative materials?

Materials to replace dental amalgam are available, but there is no one material that can completely replace amalgam. Inlays, inlays and crowns in gold and ceramic can replace amalgam in larger posterior cavities or in medium-sized cavities on stress-bearing tooth surfaces. Smaller cavities in premolars and molars can now be restored with resin-based composite materials, glass ionomers or compacted gold.

Current evidence suggests that casting alloys, composite resins, glass ionomers and ceramics placed in teeth, release chemical components and degradation products, and that these substances are released from the restorations over time. These substances may be absorbed locally, inhaled or swallowed. The general systemic reactions will depend on the chemical composition of the materials or the degradation products, and their absorption and accumulation rates, as well as on several other factors. In any event, based on available data the incidence of general biological side-effects appears to be low. However, this paucity of information on systemic toxicity could be due to the lack of longitudinal dam on some of the newer materials.

Evidence suggests that non-amalgam restorative materials may induce local reactions in some individuals. Lichenoid lesions in the oral mucosa in contact with resin-based composites have been described, but these reactions usually disappear upon removal of the restoration.

Based on analyses of 16,000 treatments in 13,000 patients, the incidence rate of systemic or local toxic or allergic reactions to all restorative dental materials in current use has been estimated to be less than 1:1000, with the reactions being of minor severity.

In summary, virtually all non-amalgam materials used in tooth restorations contain constituents that could contribute to local reactions. However, there is no clear evidence that these substances are released in sufficient quantities and forms to produce general toxic effects or severe hypersensitivity reactions in humans.

Question 9: Is mercury in dental amalgam an environmental hygiene problem ?

On a global basis approximately 10,000 tons of mercury are produced annually for anthropogenic use. It has been estimated that 3-4% is used in restorative dentistry. According to most recent statistics 1.7 tons of dental mercury is sold annually in Sweden. In dental practice approximately 50% of the freshly triturated amalgam is used to produce amalgam fillings, 10% is collected as primary surplus and the remaining 40% is discharged with the waste water or as solid waste. It should be noted, however, that these estimates are highly dependent on local clinic routines and may vary considerably.

Major chunks of amalgam produced during the fabrication of amalgam restorations are usually carefully collected and sold for reprocessing. Minor amalgam particles develop during the production of new fillings or amalgam dust is formed during the removal of old restorations.

Studies have found significantly lower levels of mercury in waste water when dental clinics were equipped with amalgam separating devices. Approved amalgam separators are now mandatory clinic equipment in a number of countries, including Sweden. Recent studies have shown that by practicing simple guidelines for the management of solid waste, including collecting extracted teeth with amalgam fillings and trituration capsules, most of this waste can be properly handled, and the amount of mercury from dental sources be significantly reduced.

Very few data are available on the potential environmental effects of amalgam fillings from deceased and buried persons. The emission of mercury from Swedish crematoria has been estimated, but published data are sparse. Emission filters that effectively reduce the release of mercury from crematoria are available and may significantly decrease the release of mercury into the air.

With proper mercury hygiene measures, mercury emerging from dental amalgam does not per se represent an environmental hygiene problem.

Question 10: Do available data justify discontinuing the use of dental amalgam or recommending replacement?

Silver amalgam has been used as dental restorative material for more than 150 years. Even today, with the advent of new synthetic non-metallic materials and novel, time-saving procedures, silver amalgam is the most widely used and cost-effective dental material in restorative dentistry.

Although minute amounts of mercury are released from amalgam restorations, these do not cause demonstrable adverse effects of significance to the general public. Published reports of systemic toxic effects documented to have been caused by mercury from dental amalgam, are not available in the scientific literature. Local allergic reactions are exceedingly rare, and when they occur, they can be eliminated by the substitution with another material. Available scientific evidence does not justify the discontinuation of the use of amalgam, nor does it endorse a clinical concept that recommends the removal and replacement of satisfactory amalgam fillings with other materials.

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