"Chattery Teeth" is a short story written by Stephen King. It was first published in the Fall 1992 issue of Cemetery Dance, and later included in King's own 1993 collection Nightmares and Dreamscapes.
Salesman Bill Hogan notices an odd pair of walking "chattery teeth" (odd due to their unusually large size and the fact that they are made of metal) in a convenience store display. The clerk ends up giving Hogan the teeth, claiming they had been dropped and no longer work. Hogan reluctantly (having been robbed by a hitchhiker once before) gives a ride to a hitchhiker outside the convenience store; his fears prove prophetic when the hitchhiker tries to carjack him and then kill him. During the struggle, Hogan wrecks the van, and before the hitchhiker can recover and kill him, the teeth come to life and gruesomely dispatch the criminal. Hogan, trapped when his seatbelt malfunctions and refuses to release, passes out and then awakes a short time later. Behind him in the van, he hears the teeth moving. Eventually he sees them pull themselves up onto his lap, at which point he passes out again. The next time he wakes up, he is surprised to find the teeth, which he had expected to kill him as well, had instead chewed through his seatbelt, releasing him. When he exits the van to examine the surroundings, he is just in time to see the hitchhiker's feet go over a nearby rise, as though his body is being dragged.
9 months later, Hogan returns to the same convenience store where he first got the chattery teeth. The original owner had died, leaving the store to his wife. He had also left something with her for Hogan - the chattery teeth had returned to the store after the accident. The store owner assumed Hogan had just dropped them and kept them so that they could be returned to him the next time he stopped in. Hogan put the teeth in his pocket and left the store, coming to think of them as a protector of sorts.
The audiobook version of this story, in the Nightmares and Dreamscapes collection, is read by Kathy Bates, who played Annie Wilkes in the film adaptation of Misery and Dolores Claiborne in the film adaptation of that novel.