There are three central figures in the pantheon of North American children’s mythology: Santa Claus, the Easter Bunny and the tooth fairy. But while the origins of the first two are fairly well documented — a combination of Christian and pagan traditions, with some recent tweaks from the marketing departments at Coca-Cola and Cadbury, respectively — far less is known about the third. As recently as the 1970s, when a radio DJ in Chicago made an on-air reference to the tooth fairy, staff at the American Dental Association were inundated with calls for more information about her. “We went out of our minds,” the director of library services said at the time. “We should have at our fingertips answers to all dentally related questions. But in this area we have nothing.”