This book is a real classic in Norway.The book is about two men, Karius and Baktus, who live in the teeth in the mouth of a boy named Jens. They feed on whatever Jens eats, especially when he eats candy. If he keeps his teeth clean, Karius and Baktus starve. But Jens loves candy, so they have plenty of food. When they're not hungry, the two men make holes in Jens' teeth (the holes are their houses).
In Norway, parents read this story to their children in order to teach them to keep their teeth clean.