Dentistry's new choices offer plenty to chew on

Los Angeles Times

Cavity treatment used to be simple. A dentist drilled away the decayed part of the tooth and packed the resulting hole with silver-covered mercury amalgam. It wasn't pretty, but it did the job -- at least until the amalgam started to crack or come out.

But as dental science has become more technologically sophisticated, so too have the options for replacing the enamel, dentin and pulp ravaged by bacteria and plaque. Decayed areas of teeth can now be restored with mixtures of plastics, glass, ceramic and quartz, each with varying degrees of aesthetic appeal and durability.

The variety has been driven, in large part, by cosmetic concerns. Given the choice between a molar full of grayish metal or a synthetic compound tinted to resemble tooth enamel, patients generally opt for the latter.

"Very few people today want anything placed in their mouth that doesn't match," said Rella Christiansen of Clinical Research Associates, a Utah-based nonprofit organization that evaluates dental materials and techniques.

But with adults today keeping their teeth longer than in generations past, dentists have also been searching for cavity fillers that can last for decades.

Meanwhile, vocal consumer advocates have been fighting to rid dentists' offices of mercury amalgam, which has been used since the 1850s. Mercury has already been taken out of childhood vaccines because of potential damage to developing brains, and health authorities often warn about the danger of eating mercury-contaminated fish.

Playing it safe

The majority of U.S. dentists, following American Dental Association guidance, say that no one has proved that mercury amalgam fillings diminish health, although a small number of people develop allergic reactions to the substance. Although they acknowledge that mercury can be released from fillings when you chew and can be detected in breath vapor and in the bloodstream, they point to assurances from the ADA and a handful of federal agencies that mercury released by fillings falls well within safe levels.

Some dentists are playing it safe just the same and have stopped using mercury, according to surveys of dental preferences.

Last December, Clinical Research Association found that 27 percent of randomly sampled subscribers to its newsletter weren't using amalgam, up from 3 percent in 1985 and 9 percent in 1995.

Dental insurance, however, hasn't caught up with all the new developments. Many plans will pay only for the amalgam (except where a front tooth is involved). Consumers who want something else must make up the difference, often 30 percent or more above the cost of mercury.

"We're moving toward better access because everybody is paying attention" to how the newer materials are working, said Dr. Van P. Thompson, who heads the dental materials department at New York University College of Dentistry.

CHOOSING FROM A RANGE OF FILLINGS

Here are your options when getting a tooth filled:

Mercury amalgam. This mixture of liquid mercury, powdered silver, tin and copper has long been dentistry's workhorse for its ease of use, durability and low cost. Over time, it can expand and contract with changes in temperature, leading to cracks in the filling and tooth that may require repair or replacement.

Composite resins. These combinations of resin (liquid plastic) fortified with powdered glass, quartz, silica or ceramic, mimic the look of tooth enamel. The powdered material provides strength and helps reduce the shrinkage that occurs when it hardens.

Glass ionomers. Used mostly for cavities below the gumline, these chemical compounds are made by mixing ground-up glass with polacrylic acid. The glass and acid react chemically to form a gel, which eventually hardens. The reaction also produces fluoride that's slowly released ver time and can fight cavities by inhibiting bacteria.

Resin-modified glass ionomers. These ionomers, to which resin has been added, are tougher, more translucent, more natural-looking and easier for dentists to use than glass ionomers. As with glass ionomers, these slowly release fluoride. Many pediatric dentists use it to fill children's baby teeth, however.

Gold. Gold fillings, which must be cast in a laboratory, are durable and expensive, requiring at least two visits to the dentist's office. Today's gold fillings are cemented in place with an adhesive.

Porcelain. Also known as inlays or onlays, these fillings are made in the laboratory by firing glass particles that then melt together. They offer very natural color that can match the tooth, but tend to break more easily than composite resins and glass ionomers. They are expensive, taking at least two appointments and are cemented into the tooth.

CAD-CAM. This type of filling, with a shorthand name that refers to the technique that produces it -- computer-assisted design/computer-assisted machining -- is used by perhaps 10 percent of U.S. dentists. It removes much of the potential for human error in fitting a filling. These fillings can be done in one or two dental visits and offer durability somewhere between amalgam and porcelain.

-- Los Angeles Times