Filling in for mercury

  • Health
  • Sunday, 26 Jan 2003

There’s no proof dental amalgam is unsafe, but there are options for the wary, writes JENNIFER HUGET. 

A DEBATE has been running for decades about the safety of amalgam tooth fillings (the silvery-looking ones most people are familiar with). Some public-interest groups and consumers say that since such fillings contain mercury – a known toxin – and amalgam has never been proved safe, these fillings should not be used.  

The dental industry and most government groups say dentists should remain free to use amalgam fillings because amalgam has never been proved harmful, has a long history of safe use and is supported by the Food and Drug Administration (FDA), the National Institutes of Health (NIH), the World Health Organisation and many other credible bodies. Two NIH-sponsored studies comparing the health of more than 1,000 children given either amalgam fillings or a mercury-free kind are due to end in 2006; more than six years into the study, the researchers have found no ill effects.  

The controversy erupted anew recently, when legislation that in effect would ban the use of mercury in dental fillings was introduced in the US House of Representatives. Though no action has yet been taken, the ensuing debate has been heated.  

We’re not here to resolve the dispute. But if what you have heard about amalgam fillings has made you queasy about getting any more mercury installed in your mouth and you want to know about alternatives, read on. You do have other choices – a bit more costly, perhaps, less likely to be covered fully by insurance and occasionally inappropriate. But the choices are there.  

Dentists have used silver-coloured mercury amalgam (mercury mixed, about 50/50, with a combination of silver, tin, copper and other metals) to fill cavities for at least 150 years. Because it’s strong, easy to work with, long-lasting, relatively cheap and, according to most experts, safe, amalgam remains the first choice for, say, filling big cavities in rear molars, where strength is often more important than aesthetics.  

But while amalgam has proved a reliable workhorse, its use has declined over the past few decades:  

A 1993 report from the FDA noted that nearly half the 200 million-plus fillings placed in the United States in 1990 involved amalgam, about 38% fewer than in 1979. Advances in cavity prevention, through fluoride treatment and application of sealants to cavity-prone teeth, have reduced people’s need to get fillings. Beyond that, amalgam’s role has shrunk, partly because of patients’ fears, but mostly because new, specialised materials have moved in on amalgam’s turf.  

“The primary driving force” behind developing alternatives to amalgam “has been to get something tooth-coloured” says Frederick Eichmiller, director of the American Dental Association (ADA) Health Foundation. “The second has been to get something that will actually stick to teeth.”  

Amalgam, he explains, “has to mechanically wedge itself” into a hole sculpted by the dentist’s drill in the tooth once the decayed portion is removed; materials that bond to teeth need smaller footholds and thus let dentists preserve more of the damaged tooth.  

Filling materials are used in two basic ways. For direct fillings, the material is inserted immediately after the dentist removes the decayed part of the tooth. For indirect fillings, the dentist takes an impression of the hole in the tooth from which a mold can be made; a filling is then cast and inserted in the tooth.  

Of the materials used in direct fillings, dental composite is, after amalgam, the most commonly used. The dentist mixes powdered glass and plastic resin to make a putty, which he then colours to match the tooth and glues in with an adhesive.  

Composite fillings match natural tooth colour and translucency pretty well (though they’re liable to stain over time). According to Eichmiller, they can be counted on to last about 10 years (as compared with amalgam’s 15-plus years).  

While the ADA says composite is not as strong as amalgam, this is disputed, as well. Susan Baker, a dentist in Rockville, argues that because composite doesn’t expand and contract with temperature changes as amalgam does, and because it bonds to the tooth, it is actually more durable than amalgam and even can help strengthen the tooth.  

When a dentist ascertains that a patient’s tooth is likely to continue decaying after the filling is in, he may recommend a glass ionomer filling, which is like composite in most respects but which slowly releases cavity-preventing fluoride.  

Neither composite nor ionomer can be used in areas of the mouth that can’t be kept utterly dry during the filling process; they won’t ever adhere to the tooth if they get wet. But for small and easily isolated or highly visible cavities, they’re a popular choice, particularly since their cost is similar to or only slightly higher than that of amalgam, depending on the complexity of the procedure, the location of the tooth and the individual practice’s fee structure.  

For strength and durability, though, the gold standard for tooth restoration is, well, gold. Indirect filling techniques allow dentists to use gold, gold alloy and other metals that are cast in a lab. When appearance counts, a cast metal filling can be fused to a tooth-coloured porcelain overlay, combining the strength of metal with the aesthetics of porcelain. Because they require at least two appointments (one for removing decay and taking the impression, the other for fitting the filling) and lab work, indirect fillings can cost anywhere from five to 10 times as much as amalgam.  

Dentists note that in the eyes of insurance companies, all fillings are not created equal.  

“Insurance will sometimes pay for the lesser of two acceptable options,” says Daniel Deutsch of the Washington Centre for Dentistry, a large practice in the District of Columbia. Patients who choose composite over amalgam in instances where either material will do may find themselves paying the difference between the costs of the two fillings.  

If you are freaked out about mercury fillings, be aware that most dentists will caution you against making a decision based on that fear. Baker says she frequently sees patients who say they don’t want “those silver fillings”, either because they “look awful” or because they’ve heard they’re dangerous.  

“I would never say, ‘Let’s do a white filling because mercury’s dangerous,’” Baker says. “I’d do it because it looks better, bonds to the tooth and makes the tooth stronger.”  

Deutsch says that about once a month, a patient will object to mercury amalgam fillings because of the controversy; more commonly, the objection centres on aesthetics. Despite this small number of mercury-phobes in his practice, Deutsch maintains that “a lot of people have concerns”, especially when they’ve been exposed to worrisome information on Web sites or in the media.  

“I want them to voice their concerns, and they want a professional opinion regarding which material to use,” he says. “They can benefit from my professional experience.”  

Like Baker and Deutsch, your dentist should be able to walk you through your options and recommend one kind of filling over another. In the end, though, it’s your choice, says Eichmiller. “Which is the best choice depends on the application,” he says. “But the patient should really make the decision.” – LAT-WP 

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