Trendley Dean was the 20th century's most influential dental scientist and administrator. In the 1930s, Dean was the first dental officer at NIH. In the 1940s his studies proved fluoridated water curbed dental caries. After becoming NIDR director in 1948, Dean put in place the structure prevailing today, although his focus was more on training and intramural research than extramural activities. Dean won the Lasker Award in 1952 and retired the next year.

On June 24, President Truman signed the National Dental Research Act. The measure was inspired by revelations that more than 20 percent of wartime inductees could not meet baseline dental requirements and concerns about a postwar shortage of dentists. The act was supported by influential proponents in the American Dental Association and in Congress.

Testing NIH epidemiologist Trendley Dean's hypothesis that fluoridated drinking water could prevent dental caries, on January 25, the Public Health Service began treating the Grand Rapids, Michigan supply. A long-term school-based caries examination program confirmed Dean's hypothesis. Among the most successful public health efforts in history, the Grand Rapids study bolstered the reputation of the soon-to-be established dental institute.