GRAND RAPIDS, MICH. -- When Dr. Willard VerMeulen came here in 1924, this industrial city was filled with the penniless Dutch immigrants who turned out much of America's furniture. As a dentist he had expected to see suffering, but even he was shocked by what he found.

"Not one person in 10 had a mouth full of teeth," he recalled recently. "The children were the worst. We had a room with three beds next to my office and every Saturday morning I would put a few 5- or 6-year-olds to sleep and clean out a hopelessly infected mouth."

Tooth decay plagued the United States well past World War II. Almost 10 percent of the 2 million men examined by the Army in 1942 were rejected for service because they didn't have 12 solid teeth out of 32. In 1945, more than 90 percent of all adults had lost at least one permanent tooth.

Then came fluoride. In an experiment that began mostly by chance in Grand Rapids, scientists discovered that adding a tiny amount of the mineral to drinking water would harden teeth and prevent cavities at a nominal cost. Soon after first pumping fluoride into the water system in 1945, researchers realized they had begun one of the most successful public health efforts in medical history.

The results have been startling: Fluoride has helped reduce tooth decay in the United States by 90 percent since 1940. In 1944 more than 90 percent of American children had some form of tooth decay; by 1987, 51 percent of American children had never had a cavity.

"Over the last 40 years we have come very close to eliminating tooth decay in this country," said Dr. Harold Loe, director of the National Institute of Dental Research. "What was once unthinkable is now taken for granted."

But as public health officials gather here this week to celebrate the unparalleled success that began so quietly 43 years ago, fluoride remains one of the country's most contentious public health issues. Despite hundreds of studies that prove its safety and effectiveness, almost half of the population has no access to fluoridated water. Millions of Americans -- in cities from Los Angeles to Newark -- have simply refused to accept it.

When they dropped the bomb on the Soviet Union in Stanley Kubrick's classic 1964 film "Dr. Strangelove," it was done in large part to "protect our nation's precious bodily fluids" from communists who would fluoridate the water. In the fluoride debate, facts have always played second fiddle to emotions.

"I was called a murderer and a communist," said Dr. Winston B. Prothro, the director of public health in Grand Rapids during the early days of fluoride use. "I must have had letters from every city in America, and plenty from other countries too. It fell on me to defend the physical and moral health of our entire city."

Opponents range from staunch anticommunists who insist that fluoridation is a government conspiracy to civil libertarians who believe that nobody should be forced to "take compulsory medication" in their water. Conservatives have objected to the tax costs and some environmentalists say they don't want additives in anything they eat or drink. The issue has gone to court dozens of times.

Fluoride has regularly been accused of causing cancer, heart disease, sterility and blindness. A study in a 1978 issue of Consumer Reports described the opposition as "one of the major triumphs of quackery over science."

Dozens of studies have disproved each claim, but new ones always emerge. Most recently, the foes of fluoride have charged that it causes acquired immune deficiency syndrome (AIDS).

"Fluoride is a well orchestrated government hoax," said John Y. Yiamouyiannis, head of the Ohio-based Center for Health Action and the unquestioned leader of the antifluoridation movement. "The decrease in tooth decay is a historical change. I don't know what has caused it and neither does anybody else. But it is not fluoride."

He asserts that fluoride, at high levels, can be a poison, but his detractors point out that would be true for any substance, including water.

"Everything has a toxic dose," said Loe. "With fluoride, we know what the dangers are and we know how totally safe it is at the correct dosage. Millions of people have benefited from its use."

Yiamouyiannis also points to the fact that tooth decay has decreased in the past 40 years even where there is no fluoride in the water. Health officials agree, but they say that the American diet has improved vastly, and most toothpaste used by children contains fluoride.

The case for fluoride had been documented extensively over the past four decades.

By 1942 scientists had noticed that people living in parts of the United States with naturally fluoridated water had fewer cavities than those without access to fluoride. At first dentists were put off by the mottled brown teeth that were so commonly found in places like Colorado Springs where fluoride occurs naturally in high concentrations.

But after research, they realized that, when added to the drinking water at a level of 1 part per million, the substance was able to fortify teeth without causing stains.

Public Health Service officials then set out to find two similar cities and add fluoride to the water in only one. Grand Rapids and Muskegon, Mich., were selected for the experiment, designed to last from 1945 to 1960.

Dental examiners poured into both cities and examined 50,000 youngsters in the first year, every schoolchild in each city. Each year they returned for months at a time to perform follow-up exams.

"It was a once-in-a-lifetime chance to study the effects of something on an entire population," said Dr. David B. Scott, who was the only Public Health Service examiner to participate in the entire course of the study. "How many people would ever get the chance to look at that many people and see the sharp improvement in their health?"

Grand Rapids became the first city in the world to add fluoride to its water on January 25, 1945. Five years later the city's schoolchildren had reduced by nearly 60 percent their level of tooth decay. With parents in revolt, Muskegon withdrew from the experiment and added fluoride to its water.

Dozens of communities quickly followed suit.

The vast majority of all drinking water in the metropolitan Washington area contains fluoride. For some rural communities, the cost is often prohibitive and children use special rinses in school.

Dental researchers say that for every dollar spent on fluoridation, $50 can be saved on dental treatment and the Public Health Service estimates that each year $2 billion is saved through water fluoridation.

"There is no other medical discipline in the United States where prevention has become so clearly the backbone of health care," said Loe. "I only wish I could understand why it is so easy for people to oppose this simple, effective treatment."

-----FIGHTING CAVITIES WITH FLUORIDE -----

THE EFFECTS OF FLUORIDATION ON TOOTH DECAY

This graph, based on information from the National Institutes of Health and the National Dental Caries Prevalence Survey, looks at children ages 5 to 17 and how many of their teeth are decayed, missing or filled (DMF).

The results of three surveys are shown: a 1944-45 Grand Rapids, Mich., survey conducted before water was fluoridated; 1954 and 1959 surveys conducted after water was fluoridated; and a U.S. survey conducted in 1980.

GRAND RAPIDS

BEFORE FLOURIDATION

GRAND RAPIDS

AFTER FLOURIDATION

U.S.

TOTAL