Henry Trendley Dean

Henry Trendley Dean (August 25, 1893 – May 13, 1962), was the first director of the U.S. National Institute of Dental Research and a pioneer investigator of fluorine in the prevention of tooth decay.

Dean was born in Winstanley Park, Illinois on August 25, 1893. He received his dental degree from St. Louis University in 1916 and entered private practice that year in Wood River, Illinois. During World War I, he served with the United States Army until 1919, when he returned to his practice. In 1921, he entered the United States Public Health Service and was stationed in several US Marine Corps hospitals until 1931 when he was placed in charge of dental research at the National Institute of Health, advancing to director of the dental research section in 1945. After World War II, he directed epidemiologic studies for the Army in Germany. When Congress established the National Institute of Dental Research in 1948, Dean was appointed its director, a position he held until retiring in 1953.

Dean's legacy comes almost entirely from his research into fluoridation. At the urging of Dr. Frederick McKay and others concerned with the brown-staining of teeth in certain regions of the country, Dean was asked to make this his first assignment at the Institute. With the help of his fellow investigators and the cooperation of dentists and other health workers in the field, it was established that high amounts of fluorine in drinking water caused mottled enamel on the teeth, while at the same time precipitating lower rates of dental caries (cavities). The rest of Dean's professional life was spent finding the optimal level of fluorine that would prevent tooth decay yet avoid staining teeth.

After his retirement, Dean joined the American Dental Association as Secretary of its Council on Dental Research. In this role, he continued to advocate and defend the addition of fluorine to public drinking water. He was frequently called to speak on the subject in the United States and abroad, mostly to refute the arguments of those who opposed water fluoridation. He died in 1962, after a long-time battle with asthma and emphysema.

The International Association for Dental Research has an award named after Dr. Dean, called the H. Trendley Dean Memorial Award, recognizing meritorious research in epidemiology and public health.