- The Washington Times - Monday, August 16, 2004

David Bertman, a dentist who practices in Burke, has had the silver in his mouth replaced with tooth-colored fillings as the amalgams expire because, like his patients, he likes how natural the composites look. He recommends the composites to most of his patients.

“They look in their mouth, and they see a filling they barely can see. They think of themselves with their mouth being perfect,” says Dr. Bertman, a doctor of dental surgery. He provides composites for 90 percent of his patients needing fillings, he says.

That’s how Dr. Bertman’s patient Patti Stewart, 61, sees her smile.

“I can’t believe it when I get up in the morning and I see these teeth I thought I would never have,” says Mrs. Stewart, of Springfield.

Dr. Bertman replaced the four crowns on Mrs. Stewart’s upper front teeth and switched her amalgams for crowns or composites, depending on the size of the original cavity. Mrs. Stewart has a dozen crowns and two to three composites.

“Once you get it all together, your bite becomes perfect, and you don’t have gaps between your teeth,” she says.

Dental patients such as Mrs. Stewart often select composites, crowns and ceramic for their front teeth, according to a survey conducted in 1999, says J. Rodway Mackert, a doctor of dental medicine who holds a doctorate in materials science.

When it comes to their premolars and molars, 60 percent of the patients choose amalgams and 40 percent prefer composites. Less than 1 percent select gold, ceramic or a special kind of dental cement for their fillings.

“Both of these materials [amalgam and composite] provide good service,” says Dr. Mackert, a professor in the department of oral rehabilitation at the Medical College of Georgia, in Augusta, and a researcher of dental materials.

Aesthetics is what gives composites an edge over amalgams, but the metal fillings also have their advantages. Either way, both types can be expected to last several years.

“Both of them are very safe. Both are well-proven, very effective, with good track records,” says Dr. Frederick Eichmiller, DDS, director of the ADA Foundation’s Paffenbarger Research Center, located at the National Institute of Standards and Technology in Gaithersburg.

The amalgams generally last longer than composite fillings, but the time frame varies somewhat, according to the research. A study conducted in 2001, for example, shows that amalgams last a median of 12 years and composites five or more years, while another study from 2000 gives the median age for amalgams as 10 years and composites eight years, Dr. Mackert says.

When the composites first came on the market in the 1970s, they lasted about four years, half as long as they last today, says Ivar A. Mjor, a doctor odont, the Norwegian equivalent of a doctorate in dentistry, who teaches at the University of Florida College of Medicine in Gainesville.

“Two things made them last longer. Dentists were taught how to place them, and second, the materials have improved,” he says.

Composites consist 10 to 30 percent of resin and the rest of glass particles, which provide strength and filler.

Amalgam, which first was used in the late 1800s, refers to a filling consisting of silver and, in smaller portions, copper, tin, zinc and mercury.

“People have a concern with the amalgam because there is a low percentage of mercury bound up in the materials,” Dr. Bertman says. “That’s been a misunderstanding that the mercury is going to affect the rest of their systems and cause mercury poisoning. … I hear their concerns, so I would prefer not to use it.”

The concerns, however, are ill-founded, Dr. Bertman says. The mercury is bound to the other metals in the filling and is not absorbed into the body.

Teeth grinding may cause a minuscule amount of the metal to be released, but that amount is not harmful, he says.

Amalgams are chosen for their strength, durability and reliability, Dr. Mackert says.

The fillings, which cost 25 percent to 50 percent less than composites, work best for large cavities; cavities in the back of the mouth, where moisture accumulates; and cavities under the gumline, Dr. Eichmiller says.

The fillings are structured wider at the bottom to keep them in place because the metal does not bond directly with the material of the tooth.

Alternatively, composites do bind and, like glue, are not able to stick in wet environments. They work best for small cavities and require that a smaller area, the decayed portion of the tooth, be removed for placement, Dr. Eichmiller says.

A plastic adhesive is placed on the tooth to bond the composite filling to the tooth, then the filling material is added in layers. The placement of the layers is technique-sensitive.

A micro leakage can occur if a drop of saliva or blood from the gum enters the material, causing the adhesive resin to break down from acids in the mouth.

Once placed, the composites and amalgams have to contend with the “pretty hostile environment” of the mouth, Dr. Mackert says. The mouth is constantly wet and can cause the fillings to deteriorate over a long period of time.

Metals corrode, he says, and plastics degrade as they hydrolyze, a process noticeable at the microscopic level. Foods of different temperatures can cause the fillings to expand and contract.

Food contains fats and oils that can cause the materials to break down. Also, microorganisms in the mouth produce waste products, acids that can degrade natural and artificial materials.

“The patient has a big role in determining how long the fillings will last. If they take care of their teeth, their fillings will last longer,” Dr. Mackert says.

The Chicago-based American Dental Association recommends that patients brush their teeth twice a day, floss once a day, use fluoride toothpaste and rinse daily with mouthwash.

The care helps prevent cavities, which are caused by various types of bacteria in the mouth.

Bacteria, which is mostly anaerobic (able to grow where there is no air), colonize on the teeth and form a sticky white coating called plaque that can harden into tartar a dental hygienist has to remove.

The bacteria feed off sugars and carbohydrates in food and produce an acidlike material that demineralizes, or removes minerals, from teeth, causing them to weaken and cavities to form.

“You basically have a hole that develops in the tooth,” Dr. Bertman says. “You can’t leave it there. It will continue to decay over time and get bigger.”

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