While you might be used to putting baby teeth, once they fell out, under your pillow for the tooth fairy to come and get them, there is a whole different custom in other parts of the world. In some countries like in Greece, Korea, and Vietnam children throw their baby teeth on the roof of their houses. They do this for good fortune and to ask for a new one that will grow in healthy and straight.
Sometimes only the lower teeth are thrown on the roof while the upper ones are buried in the ground.
And sometimes kids believe that when you throw your teeth on the roof, a mouse or rat will go and get them and in return your new teeth will grow as strong as those of a rodent.