Fluoridation and the Prevention of Tooth Decay

Overview

Early in the twentieth century dentists became aware that tooth decay, or dental caries, was a public health problem. Several scientists had investigated tooth decay and connected it to bacteria residing in the plaque or build-up on the teeth. Proper hygiene and care were being encouraged and research led to an unusual source of prevention—fluoride. Fluoride is a chemical found in water in some areas of the country. At very high levels it is toxic. Because of this fact, many groups objected to the addition of fluorine to the public drinking supplies of a town. The pros and cons of adding fluoride continue today.

Background

As the nineteenth century ended, researchers in the tradition of Louis Pasteur (1822-1895) and Robert Koch (1843-1910) proposed that bacteria might be a cause of tooth decay. The processing of food that became popular between 1860 and 1960 doubled the average consumption of sugar. This led to an increase in tooth decay as well as other health problems like diabetes. In 1890 Willoughby Miller, a student of Dr. Koch, described his findings in the book Microorganisms of the Human Mouth. Miller stated how food bits would decay between the teeth, attack the enamel of the tooth, and cause cavities. Another scientist, J. Leon Williams, showed that dental decay results from acid acting on a particular spot on the tooth. That acid is produced by bacteria in an area of plaque buildup. A gelatinous "gunk" prevents that area from coming in contact with the saliva, which has a germicidal effect. Williams advocated frequent and thorough cleaning of the teeth. In 1896 he introduced the slogan, "A clean tooth never decays."

The connection between dental decay and oral hygiene was the subject of much research at the turn of the twentieth century. In 1910 Sir William Hunter pointed out that infections around the teeth affect general health. He wrote an article called "The Role of Sepsis and Antisepsis in Medicine." He also advocated teaching medical subjects to dental students, as heart disease and other problems are related to the condition of the teeth.

When W. G. Ebersole became chairman of the Oral Hygiene Committee of the National Dental Association in 1909, he campaigned for dental colleagues to wage war for good dental hygiene. He designed a plan to teach school children about good dental care. The discovery of fluoride added perfectly to this idea of prevention.

Impact

Fluoride propelled dentistry into the area of prevention rather than just correcting problems. In 1901 Frederick Sumter McKay left the East coast to set up a dental practice in Colorado Springs, Colorado. He was intrigued by the large brown, chocolate stains on the teeth of many area residents. Many people had stains so severe that the entire tooth was splotched the color of chocolate candy. No one could explain the condition, and there was nothing written about it in the literature of the day. The natives attributed it to such things as too much pork, inferior milk, and calcium-rich water. McKay decided to launch his own investigation. He sought the help of local dentists, but they were not interested in the problem and scoffed at McKay for undertaking such studies.

McKay suspected that the stains, which became known as the Colorado Brain Stain, might have something to do with the water. A big break came in 1909 when McKay posed the problem to renowned dental researcher Greene V. Black (1836-1915) of Northwestern University. Black made his way to Colorado Springs and, likewise, was amazed that such a disorder would not be reported in dental literature. The Colorado Springs Dental Society did issue a report that 90% of the city's locally born people had signs of the brown stain. While watching the children of Colorado Springs at play, Black lamented that it was not just a problem of childhood but a deformity for life.

When Black died in 1915 he had spent six years investigating the condition. He and McKay had determined: (1) the mottled teeth resulted from a developmental imperfection to teeth; (2) people with the stain had fewer cavities. There were still no clues as to the cause. A big break came in 1923 when McKay was invited to Oakley, Idaho, across the Rocky Mountains to talk with parents who had noticed strange brown stains on their children's teeth. They noted that the stains appeared after the community had installed a pipeline coming from a warm spring five miles away. McKay suggested they abandon the pipeline for another. It worked; the stains began to disappear.

McKay and Dr. Grover Kempf of the United States Public Health Service were invited to Bauxite, Arkansas, a town owned by the Aluminum Company of America (Alcoa). They analyzed the water but found nothing. At Alcoa's head office in Pennsylvania, their report came across the desk of head chemist H. V. Churchill. He brought samples from Bauxite and used a very sophisticated technique of water analysis called photospectrographic analysis. He could hardly believe it when he found the element fluorine in the water. He wrote a letter to McKay about his revelation and then asked him to send water samples from all the communities with the brown stain problem. McKay had his answer. The connection was made between the mottling and the presence of fluorides in the water.

Fluorides are compounds of the element fluorine. The element is in the same chemical family as chlorine, a group called halides, and in many substances in nature. Actually, by itself fluorine is a strong, brownish-yellow, poisonous gas. It is very reactive and combines with most elements. The term fluoridation began to be used with the addition of the chemical to the water supply.

Armed with the initial studies, health scientists started looking seriously at fluoride. H. Trendley Dean, head of the Dental Hygiene Unit at the National Institute of Health, became interested in fluorine in 1931. He wanted to know how high the level of fluoride must be before staining began. He assigned Dr. Elias Elvove, a chemist, the task of determining this level. He had state-of-the-art equipment that could measure an accuracy of 0.1 parts per million (ppm). He traveled the Untied States measuring fluorides in drinking water and determined the safe threshold was 1 ppm. Above this level, fluorosis—the term given to the accumulation of fluoride in teeth enamel—began to occur.

In 1938 the Public Health Service was involved in a study of two communities. Galesburg, Illinois, a community with a high degree of tooth mottling, was compared to Quincy, Illinois, where the water was free of fluorides. The study showed children of Galesburg had fewer cavities than the children of Quincy.

The Public Health Service then went in another direction. Having determined that one part of fluoride per million of water was the ideal level to prevent tooth decay but not cause mottling, they reasoned that adding fluoride to a community's water would reduce decay. Extensive tests were done on animals, and in 1945 the Public Health Service concluded it was safe to begin tests. Water systems in Newburgh, New York, and Grand Rapids, Michigan, became the first to add the chemical sodium fluoride to water. The city of Kingston, New York, was a control group. During a 15-year study, researchers monitored the rate of tooth decay among Grand Rapids' 30,000 school children. The conclusion was that fluoride dropped decay by about 60%. A group of dentists in Wisconsin also added fluoride in their state.

Results from these initial studies indicated a reduction of dental caries by two-thirds. The results encouraged the Public Health Service to recommend in 1950 that fluorides be added to the public water supplies of all communities. The next year the American Dental Association (ADA) also endorsed it. The medical, dental, and public health communities were solidly behind adding fluoride to water.

A large outcry arose among some groups who believed that adding fluorides might be unsafe and risky. Some groups decried the addition of a chemical that, in large amounts, was toxic. Others objected that people did not have a choice if they wanted the chemicals or not. Some communities resisted and turned down the proposal in a referendum. Today, about 60% of people live in communities with fluoridated water. About 30 other countries practice fluoridation.

Other ways of applying or getting fluorides emerged. The fluoride may be taken in tablet form, in a mouthwash solution, or painted onto the teeth. In the early 1950s Proctor and Gamble (P&G) had the idea of adding the chemical to toothpaste. Researchers at the University of Indiana, working with stannous fluoride, found a way to bond the substance to teeth. Then, in 1956, P&G introduced its "Crest" toothpaste with fluoristan and launched an immediate media blitz with the refrain, "Look mom, no cavities." The timing was right because television was just coming into households throughout the country. Later, the Council on Dental Therapeutics gave "Crest" their seal of approval.

The "Crest" claim that cavities could be reduced by two-thirds has since been modified to about 20-25%. However, the addition of fluoride, combined with education, has been an effective tool for dental care and prevention of cavities.

EVELYN B. KELLY