In brief: Ear/tooth pain. If there is an infection surrounding the root end of a tooth, this will affect the entire nerve trunk. The nerve trunk that innervates the upper teeth run back toward and around the ear canal. So this would be referred pain froom the infected tooth. If there is an infection surrounding the root end of a tooth, this will affect the entire nerve trunk. The nerve trunk that innervates the upper teeth run back toward and around the ear canal. So this would be referred pain froom the infected tooth. In brief: Ear/tooth pain.