The Arsenal Files 4/The Arsenal Files 4 (Arsenal Computer).ISO/health/amalgam.txt

Text File | 1995-02-21 | 13KB | 272 lines

                           Alternatives to amalgam
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   Amalgam restorations  better known as "silver fillings"--are probably
 more familiar to millions of Americans than they would like.

   Dental amalgam is the most widely used material to fill cavities in
 decayed teeth, technically known as caries. It has been used for 150
 years; only gold has been used longer.

   Amalgam is composed of approximately equal parts of liquid mercury and
 alloy powder containing silver, tin, copper, and sometimes lesser
 amounts of zinc, palladium or indium.

   Despite amalgam's long history of use, some scientists and consumers
 are concerned that the mercury from amalgam restorations might be
 harmful. Nearly half of 1,000 adult Americans surveyed by the American
 Dental Association in 1991 said they believed amalgam could cause health
 problems.

   Besides having the broadest range of use in dental procedures,
 "amalgam is the most forgiving to place," says William Kohn, D.D.S.,
 National Institute of Dental Research, part of the National Institutes
 of Health. "It is not as sensitive to moisture saliva, which can be a
 problem. With other restorations, the dentist has to be more meticulous
 or the restoration fails when the filling is placed."

   Dental amalgam, which the Food and Drug Administration regulates as a
 medical device, is used in children and adults alike for:

   * stress-beating areas and small-to-moderate-sized cavities in back
     teeth, such as molars

   * severe tooth damage

   * when finances prohibit use of more expensive alternative filling
     materials

   * as a foundation for cast-metal, metal-ceramic, and ceramic
     restorations

   * when patient cooperation during the procedure or commitment to
 personal oral hygiene is poor. (Silver is cheaper and easier to place,
 more resistant to decay than other materials, such as composite
 plastic, tooth-colored fillings, and less costly to replace.)

   "Dental amalgam is the only material I'm aware of that, when it
 initially degrades, the restoration improves," says Corbin. "A byproduct
 builds up and seals the interface between the tooth and the
 restoration. There may be drawbacks, but amalgam has allowed people to
 keep teeth in their mouths."

   Amalgam is not used when appearance is important (as in front teeth),
 in patients allergic to mercury, or for large restorations when use of
 costlier materials is not prohibitive.

   In 1990, nearly half of the more than 200 million tooth fillings
 performed in the United States involved dental amalgam. This is down 38
 percent from 1979.

   Dental amalgam use began to decrease in the 1970s, primarily because
 dental caries among school children and young adults declined and new
 alternative materials were developed and improved.

   Not only has the incidence been reduced, but also the type of dental
 caries has changed, possibly as a result of fluoride used in toothpaste
 and topical gels and in water, sealant use, improved oral hygiene
 practices, and dietary changes.

   Stephen Corbin, D.D.S., from the national Centers for Disease Control
 and Prevention, says that dentists see fewer caries, which are generally
 less aggressive once they start, and that today early caries can
 actually be reversed clinically.

   The decision to fill a tooth is complex, whether you are replacing a
 filling, repairing a damaged tooth, or filling a tooth for the first
 time. "The decision was simpler in the past. Today there are more
 choices to make because we see different disease patterns." says Kohn.

   Alternative dental restorative materials (composites, glass ionomers,
 ceramics, and others) are being used more often because cavities are
 usually smaller and amalgam is therefore not the only choice. Since the
 alternatives are not as durable as amalgam, the most commonly used
 alternatives are not used for large fillings or stress-beating areas.
 According to Kohn, this is often an inappropriate choice.

   Approximately 70 percent of the fillings performed each year are
 replacements. Most replacements require amalgam or other metallic
 materials because, as more tooth is drilled away, the new area is larger
 with each replacement. Some patients do not want the silver showing in
 their teeth and choose other filling materials that match the natural
 tooth color.


   Amalgam Risks and Benefits

   According to Dental Amalgam: A Scientific Review and Recommended
 Public Health Service Strategy for Research, Education and Regulation,
 published January 1993 by the Department of Health and Human Services,
 scientists have shown that dental amalgam emits minute amounts of
 mercury vapor.

   "The toxicity of high-dose mercury levels in industrial settings has
 been established. Although mercury vapor can be absorbed through
 breathing and eating, research has not shown that low levels of
 mercury-containing amalgam are harmful except in rare cases of mercury
 allergies.

   A literature review of amalgam research by the U.S. Public Health
 Service found no sound scientific evidence linking amalgam to multiple
 sclerosis, arthritis, mental disorders, or other diseases, as has been
 suggested by some critics of amalgam.

   The PHS subcommittee, which prepared the amalgam report, reviewed the
 research of low-dose mercury toxicity. According to the findings, a
 fraction of the mercury in amalgam is absorbed by the body. People with
 amalgam fillings have higher concentrations of mercury in their blood,
 urine, kidneys, and brain than those without amalgam. A small proportion
 of patients may manifest allergic reactions to these restorations, but,
 Corbin says, there are only 50 cases of amalgam allergies, reported in
 the scientific literature.

   According to the PHS report, the few human studies done to determine a
 possible public health risk from amalgam have been flawed or contained
 too few subjects. If there are long-term effects from the mercury in
 amalgam, they likely are subtle--slight neurological or behavioral
 changes--and difficult to detect.

   The subcommittee could not conclude with certainty that mercury in
 amalgam fillings poses a health threat or that removing them is
 beneficial. Removal itself may, in fact, expose patients to additional
 mercury absorption since drilling into the amalgam filling releases
 mercury into the air. Many questions remain unanswered, but for now the
 PHS report does not recommend either removing or not using amalgam. The
 report does, however, recommend more research into what the specific
 health effects of low-level mercury exposure might be, whether these
 effects can be produced by amalgam, and whether certain population
 groups, such as women and children, might be particularly sensitive. The
 report also recommends research on the safety of amalgam alternatives.


   Alternatives

   No single material can completely replace dental amalgam. Gold and
 ceramic inlays and crowns can replace amalgam in larger back cavities or
 in medium-sized cavities on other stress-bearing tooth surfaces.
 Smaller cavities in premolars and molars can now be restored with
 resin-based composite materials, glass ionomers, or compacted gold.

   Alternatives to dental amalgam are not as durable, however, especially
 in larger cavities, and can cost significantly more.

   "A wholesale conversion to non-amalgam materials would drive up
 national dental health-care costs by about $12 billion in the first
 year, a tremendous cost impact," says Robert C. Eccleston, assistant to
 the director at FDA's Center for Devices and Radiological Health. "The
 cost would also increase in the years following any across-the-board
 conversion."

   Also, according to the PHS report, it is possible that alternative
 dental restorative materials could have long-term toxicity problems of
 their own that have not yet been discovered. Since no definitive data
 exist to show that mercury in dental amalgam is directly linked to
 illness, and since amalgam is less expensive, easier to place, and more
 durable than alternatives, dental amalgam should continue to be used.


   Composites

   Composites, made from synthetic resins, are used to make attractive
 restorations in the front teeth. Dentists use a combination of
 composites and sealants, technically known as preventive resin
 restorations, to treat small cavities and conserve tooth structure. But
 the use of composites as substitutes for restorations in stress-beating
 areas may be inappropriate because composites can leave a tooth
 susceptible to recurrent decay.


   Pit and Fissure Sealants

   In its report, PHS recommends dental sealants to prevent caries.
 Sealants prevent cavities by sealing with thin plastic coating the
 natural pits (round holes) and fissures (grooves) in their molars. Pits
 and fissures in permanent first molars account for 91 percent of the
 surface cavities in children up to 11 years of age.
   "The best restoration that is ever placed cannot be as good as the
 sound tooth structure that was there in the beginning," Corbin says.
 "But some of the preventive materials sealants actually improve tooth
 structure."


   Glass Ionomers

   Glass ionomers, introduced to dentistry in the 1970s, chemically bond
 to the tooth structure and have the beneficial side effect of releasing
 fluoride.
   Ionomer placement technique requires limited drilling, so the
 procedure is quick and the result fairly attractive. Because glass
 ionomers are generally not used in occlusal surfaces (biting surfaces),
 their use is limited to baby teeth and primarily root surfaces.


   Gold Foil

   Although not widely used today, gold foil restorations (compacted
 gold) date back many centuries. These fillings may last 20 years or
 longer, but are not used for large or very visible areas. Gold foil
 restorations require more skill and careful attention to detail during
 placement to prevent harm to the tooth pulp (nerve) and gums. Its high
 cost also makes gold foil a less popular choice.


   Cast Metal and Metal-Ceramic

   Cast metal and metal-ceramic restorations generally require two or
 more dental appointments and are typically used for inlays, onlays,
 crowns, and bridges. Use of metal and metal-ceramic materials depends on
 the degree of tooth destruction from decay, breakage, or amount of
 tooth removed by drilling. It is also determined by the number of
 missing teeth, how important looks are to the patient, and the patient's
 oral hygiene and financial situation.
   These restorations cost approximately eight times more than amalgam
 and are most often used:
   * in teeth involved in the stress from chewing and biting
   * when moderate to severe breakdown of the tooth requires replacement
   * if the patient demands a more pleasing appearance than that produced
 by amalgam.
   Cast metal or metal-ceramic restorations are generally not used if:
   * there is a danger of exposing the tooth pulp while preparing the
 tooth for restoration  for example, in patients under 18 whose pulp is
 higher in the tooth
   * the patient shows evidence of extensive teeth grinding or clenching
   * the patient is known to be allergic to the metals used in casting
 alloys (gold and certain non-precious casting metals).


   Regulation

   The PHS report recommends that FDA require restorative material
 manufacturers to identify the ingredients used in their products, and
 FDA is considering such an action. Industry disclosure of product
 ingredients would provide dentists with information necessary to prevent
 sensitivity reactions in allergic patients.

   The PHS findings indicate that it is inappropriate to recommend
 restrictions on the use of dental amalgam unless more studies show a
 definite link between amalgam and illness.

   "The science simply doesn't justify such an action," FDA's Eccleston
 points out. "There are several reasons for not restricting amalgam.
 First, current evidence does not show that exposure to mercury from
 amalgam restorations poses a serious health risk in humans, except for a
 very small number of allergic reactions. Second, there is insufficient
 evidence that alternative materials have fewer potential health effects
 than amalgam. And, as stated previously, amalgam use is declining."
   Laura Bradbard is a member of FDA's public affairs staff.


   PHS REPORT AVAILABLE

   For a copy of Dental Amalgam: A Scientific Review and Recommended
 Public Health Service Strategy for Research, Education and Regulation
 from the Department of Health and Human Services, January 1993, write
 to:
   Les Grams
   HFZ-220
   Subcommittee on Risk Management/ CCEHRP
   5600 Fishers Lane
   Rockville, MD 20857