Originally created 08/08/03

Alternatives studied for silver tooth fillings

The screeching drill in his mouth didn't seem to bother Robert Bellavance, of Grovetown. Nor did he blink at the silver amalgam that filled the hole in his tooth.

"I've had fillings in my mouth my whole life," he said.

Many dental patients are concerned about the amalgam, which contains mercury, because some dentists have advocated it be removed and because Internet hoaxes link it to everything from headaches to multiple sclerosis.

Despite assurances, a Medical College of Georgia researcher has a $1.4 million grant to study composite alternatives, which for now are more expensive and don't last nearly as long.

The controversy began with a paper published in 1979, in which new, more sensitive detectors had found tiny amounts of mercury vapor emanating from amalgam fillings, said Rod Mackert, a professor of dental materials at MCG's School of Dentistry. Soon, some dentists were telling patients that removing the fillings would cure "everything from acne to seizures to multiple sclerosis," Dr. Mackert said.

The amount of mercury released is very small - about 1 to 2 micrograms a day, far less than what is received through food and the environment, Dr. Mackert said. It would take between 265 and 310 fillings in the mouth at one time to reach a toxic level, Dr. Mackert said.

There also are problems with the composite fillings, said David Pashley, a researcher and regents professor of oral biology in the School of Dentistry.

"They're more expensive, they're more difficult to place," the grant recipient said. "And they don't last as long."

There are several reasons why. Enzymes in the tooth can break down the tooth over time.

"They have the seeds of their own destruction," Dr. Pashley said. He is looking at pre-treatments that will keep the enzymes in line, such as zinc or a common anti-bacterial agent called chlorhexadine.

Before the filling goes in, the surface of the tooth is acid-etched to help the filling stick to the surface. The problem is the tooth material is "literally like a sponge; it's very, very soft," Dr. Pashley said.

"And if you allow it to dry, it collapses."

So the surface has to be wet, and resin in the filling has to be somewhat water-absorbing, which over time makes it more vulnerable, Dr. Pashley said. His solution is to wet the surface with ethanol instead, which can be evaporated off, and to find more water-hating resins for the composites.

In the era of gene-hunting, this kind of work may seem less sexy, Dr. Pashley said.

"But there's going to be billions of dollars in dental care costs," he said. "And if we can get it right, we can save a lot of money."

Until then, silver fillings are fine.

Reach Tom Corwin at (706) 823-3213 or tomc@augustachronicle.com.


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