About 4000 cavities form daily in the mouths of children and teenagers in the metropolitan Boston area. Most dental and public health experts believe that more than half of these cavities can be prevented cheaply and easily by fluoridating the water supply. On Jan. 1, 1978, after ten years of state planning and construction, the Metropolitan District Commission (MDC) will begin fluoridating the water supplied to Boston and 33 surrounding communities.

The fluoridation will affect more than 2 million people and will be particularly beneficial to those families who cannot afford dental care, Dr. Robin M. Lawrence, regional consultant for dentistry for the United States Public Health Service for New England, says.

"Fluoridation is by far the single most cost-effective way to prevent tooth decay on a large scale," Lawrence says. The cost of maintaining a public fluoridation system adds up to only 10 to 20 cents per person per year, he adds. Installing the new system will cost $1.15 million and annual maintenance will cost $650,000, James Gillis, associate civil engineer for the Water Division of the MDC, says.

The system will pay for itself many times over, Lawrence says. Every dollar spent on water fluoridation saves $35 of dental bills, and the state will save money by ultimately paying out less in dental insurance, he says.

Despite such apparent benefits, many groups such as the Massachusetts Citizens' Rights Association, Inc., have lobbied against the state project since the plan's inception ten years ago. The group opposes fluoridation on the basis of individual rights, Elizabeth E. Dyer, secretary of the association, says.

"We are entitled to freedom of choice, and no segment of the population can tell us what we should drink," Dyer says. "We don't believe we should be made guinea pigs," she adds.

The organization also argues that excessive amounts of fluoride in drinking water may be carcinogenic. Dyer cited a 1975 study by Dr. John Yiamouyiannis, science director of the National Health Federation (NHF), another anti-fluoridation group, based in California. That study indicated that during a 20-year period cancer death rates in ten large fluoridated cities surpassed those in comparably sized non-fluoridated cities.

The National Cancer Institute in Washington, D.C. has repeatedly refuted the NHF study, showing that it is statistically unsound and unscientific. More than ten separate government studies have shown conclusively that there is no link between fluoridation and cancer, Dr. William Bock, chief of Dental Disease Prevention Activity at the Atlanta Center for Disease Control, says.

Edward A. Sweeney, assistant dean for curriculum at the Harvard Dental School and chairman of the Massachusetts Committee for Fluoridation, also notes that the Yiamouyiannis study was wholly unscientific and did not account for other carcinogenic agents common to industrialized areas.

"The National Health Federation is composed of a group of charlatans," Sweeney believes. Using NHF statistical techniques, "one could show sugar to be carcinogenic," he adds.

In addition, Sweeney points out that humans are exposed to small amounts of fluorine found naturally in the environment. "We get it in our food, even in utero the fetus is exposed to small amount of fluorides. Fluorine in the drinking water at a concentration of one part per million (ppm) is no new material to our bodies," he says.

James H. Shaw, professor of Nutrition at the Dental School, supports Sweeney's argument, explaining that putting fluorine in the water is not introducing an additive, but merely readjusting existing fluorine levels to an optimum concentration.

"Fluoridation is the best tested of all public health procedures. It is both effective and safe," Shaw said.

No NHF officials were available for comment last week. Yiamouyiannis's secretary did say that directly before becoming science director of the federation, Yiamouyiannis was in business for himself making salad dressing for two years. Prior to that he edited chemical abstracts in Columbus, Ohio.

Despite their opposition to fluoridation because of alleged "side effects," anti-fluoridationists reluctantly admit that the process does have some beneficial effect on teeth. "Fluoridation does delay a few cavities in children," Dyer says.