HIRSCHFELD, ISADOR (1882–1965), U.S. specialist in gum diseases. Hirschfeld, who was born in Riga, Latvia, was taken to the U.S. in 1890. In 1916 he began teaching at the New York Postgraduate School of Dentistry. From 1915 to 1925 he was chief of the first periodontological clinic in a U.S. hospital, at the New York Nose, Throat and Lung Hospital. Hirschfeld occupied similar positions at the Beth Israel Hospital (1924–34) and at the New York Hospital for Joint Diseases (1927–34). In 1928 he founded and headed the department of periodontology at the Columbia University Dental School. From 1929 to 1947 he was attending surgeon at New York's Presbyterian Hospital. In 1941 he was president of the American Academy of Periodontology. In addition to many articles in dental publications, he wrote The Toothbrush: Its Use and Abuse (1939). He was active in raising funds to advance dentistry in Israel.