FRIDAY, April 8, 2005 (HealthDay News) -- In good news for expectant moms with cavities, a new study suggests pregnant women aren't threatening their newborn's birth weight by getting mercury-based silver amalgam fillings.
Silver amalgam fillings, a mainstay of dentistry for 150 years, have been controversial because of concerns the mercury they contain will leach into the body. Several European countries have recommended that pregnant mothers avoid silver fillings to prevent birth defects.
However, this latest research revealed no connection between use of the fillings and low birth weight, said study co-author Dr. Philippe P. Hujoel, a professor of dental public health sciences at the University of Washington at Seattle.
"You cannot prove absolute safety, but mercury seems to have quite a bit of data on it now indicating that it shouldn't be of concern," Hujoel said.
The use of silver amalgam fillings has dipped over the past couple of decades. They made up 68 percent of all fillings in the United States in 1990, but dropped to 30 percent in 2003, said Dr. Rod Mackert, a spokesman for the American Dental Association and a professor of dentistry at the Medical College of Georgia.
Resin-based fillings known as "white" fillings have become more popular, and some dentists have abandoned silver fillings because of concerns about the safety of mercury.
While silver amalgam fillings are commonly known just as "silver," they're actually made of several metals, including silver, tin, mercury and copper. The fillings "are a very good filling material. They're very long-lasting and have good properties as far as dental material," Hujoel said.
Concerns about mercury exposure have grown in recent years, especially regarding its presence in foods such as fish. However, the U.S. government has declared that there is "scant evidence that the health of the vast majority of people with amalgam (fillings) is compromised."
In the new study, Hujoel and his colleagues studied a dental insurance company's records of 1,117 Washington state women who gave birth to low-weight infants and 4,468 women who gave birth to infants of normal weight.
The findings appear in the April 15 issue of the American Journal of Epidemiology.
The researchers found no connection between getting amalgam fillings during pregnancy -- nearly 5 percent of the women did so -- and giving birth to a underweight baby. Even women who had as many as 11 fillings during pregnancy weren't more likely to give birth to a low-weight child.
The study "is another paper in a growing body of evidence that amalgam is safe and effective way to repair teeth that have been damaged by decay or trauma," Mackert said.
Learn more about amalgam fillings from the U.S. Centers for Disease Control and Prevention.