Vampire Teeth are clothing items worn on your Lower Face. Their rarity is Common. You must be level 1 or higher to wear them. They are Unbound. They are a Limited Edition item only available in the month of October. (Monkey Quest calls it OOK-tober!) You find them in Papa Matu's Haunted Graveyard (By smashing pumpkins.) They don't give your monkey any attributes, as being worn on your Lower Face.
The Vampire Teeth are Sharp-Like Teeth, and can be seen having blood on them. This clothing item is meant to be a decoration and doesn't do anything to help in-game.