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A Smile That Lasts

Gold and silver dental amalgams are stronger than tooth-colored composites

SATURDAY, Jan. 5, 2002 (HealthDayNews) -- Is there strength in your smile?

With the wide range of tooth-colored dental materials now available for fillings, crowns and other restoration work, you'll probably never want to opt for the less-attractive metallic materials.

But those gold and silver amalgams that your grandfather used to have still last the longest, experts say.

Dentists turn to restorative materials, including the wide range of tooth-colored composites, when teeth crack, break or are even stained, but they are most commonly used to restore teeth that have developed cavities from decay. Left untreated, decayed teeth become extremely painful and are eventually lost.

When it comes to restoring the work horses of the mouth -- the stress-bearing molars that endure the daily grind of chewing food -- durability is of the utmost importance in preventing cracking or breaking, and nothing quite compares to metals to do the job, says Dr. Alan A. Boghosian, an assistant clinical professor in the Division of Dental Surgery at Northwestern University Medical School.

"Golds and silver amalgam have properties that are much stronger than general (composites) that are polymer-based," Boghosian says.

And as the portion of a tooth needing replacement increases, the more useful gold and silver amalgam are.

"As the size of the missing portion of a tooth increases through fracture or tooth decay, the performance of alternative composite materials starts separating itself a distance from metals, which are far more durable," Boghosian says.

As the name indicates, silver amalgams are actually an amalgamation of such materials as silver, zinc, tin, copper and mercury.

It's that last component -- mercury -- that gives many pause because reports have linked it with everything from memory loss to Alzheimer's disease. But major studies have ruled out the connection, and the use of silver amalgam in dentistry has been declared safe and is supported by the American Dental Association and most public health agencies.

In addition to being stronger, gold and silver amalgam are typically less expensive than composite materials because less time and skill are necessary to make the materials adhere to the tooth, Boghosian says.

With composites, the tooth must be prepared and treated with a conditioner, and the materials must be matched with the tooth color and then bonded to the tooth, he says.

Another popular tooth-colored option for restoring teeth, ceramic porcelain inlays, requires even more work: tooth impressions have to be made, lab work is needed to create and refine the inlay structure, and patients need to be fitted for temporary restorations during the process to prevent exposure to bacteria.

Such processes are called indirect procedures, meaning at least two dental appointments are usually required to get the job done, as opposed to direct procedures, which are completed in one visit.

And Boghosian says that's actually fine because composites do have a rightful and very effective place in dentistry -- specifically, in smaller fillings and toward the front of the mouth.

"If you're just dealing with small types of cavities, the use of composites actually becomes virtually par with that of metals such as dental amalgam," he says.

"In fact, they can be even more desirable in those cases because when you start using metals, in order to prevent the metal in the tooth from falling out, you usually have to sacrifice a little more tooth structure (than composites) to lock it in," he adds.

Because composite filling materials bond to the tooth, there is also a decreased chance of temperature sensitivity, compared to gold or silver amalgam restorations, he says.

A particular type of composite, called glass ionomers, in fact fights tooth decay by not only sealing the tooth, but also slowly releasing fluoride to further prevent decay.

And tooth-colored composites are overwhelmingly favored by patients, despite the expense and durability issues.

"I would say at least 70 percent of patients would prefer to have a shorter lasting composite restoration that they know they have to replace more often but matches their tooth structure rather than a metal restoration," says Dr. Ronald Goldstein, a clinical professor at the Medical College of Georgia School of Dentistry in Atlanta.

The average life expectancy of composites is only about five to eight years, but Goldstein say it's not uncommon to see such restorations last up to 15 years.

But he does advocate some use of gold and silver amalgam, when possible, as a better way of preventing an untimely trip to the dentist.

"I try to encourage patients to at least put metal in the back of the mouth where it can't be seen," he says.

Because the final decision is usually up to the patient, dentists should offer as much information and sound advice to patients in deciding how to restore teeth, says Boghosian.

"We have to balance a wide variety of considerations. The first one is, how many times do you want to be coming in and sitting in this chair to have your teeth fixed? If we use a material that isn't strong, it could break and you'll be back in the office spending more time and conceivably much more money because there is more damage to the tooth," he adds.

"For many, the aesthetic wishes for tooth-colored materials override that," he says. "But if aesthetics is not the highest need, the use of metals may be better in terms of cost effectiveness and durability."

What To Do

The American Dental Association's page on cosmetic dentistry offers more information on crowns and other tooth-colored materials.

And here's more information on Choosing the Dental Materials That Are Right For You from the Canadian Dental Association.

SOURCES: Interviews with Alan A. Boghosian, D.D.S., assistant clinical professor, Division of Dental Surgery, Northwestern University Medical School, Evanston, Ill.; Ronald Goldstein, D.D.S., clinical professor, Medical College of Georgia School of Dentistry, Atlanta, and author of "Change Your Smile"; ADA press release
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