Effect- The magician reaches into a spectators mouth, pulls out their tooth, sticks it in his own mouth, chews it, and spits it back into the spectators mouth, where it reappears in a flash.
Preparation- You need to have a willing assistant who will play the part of a random spectator, a fake tooth, a piece of white hard candy, and some black lipstick. First, color in one of your assistants front teeth with the lipstick so it looks like the tooth is missing. Then, take the hard candy, still in its wrapper, and tap it with something hard until it cracks into several pieces. Open the candy, find the most tooth like piece, and put it in your mouth. Now, all you need is a fake tooth (or, if you have access to a real one, go with that) to palm in your right hand, and youre ready to go. You can find fake teeth from any novelty shop, or in many stores around Halloween. You can even substitute a completely white, press on finger nail if youre desperate.
Presentation- Approach your assistant, and pretend that they are a random spectator. With the fake tooth palmed in the right fingers, quickly reach up, and pretend to remove the spectators tooth. This should be done quickly, and without explanation. Briefly show the tooth, and hole in the spectators mouth, and then pop it in your own mouth. Now, with your tongue, place the fake tooth in the area between your cheek and your gum, so you can keep it hidden. Crunch down on the hard candy a few times, being careful not to break your teeth, and then suddenly blow in the spectators face. As you do this, your spectator should reach up with their tongue, and rub off the lipstick. Timed perfectly, it will seem like you just blew the tooth back into their mouth. The key to selling this effect are that the audience believes your assistant is just a spectator, and acting, both on your part, as well on that of your assistants.