A mouth mirror is a medical_instrument typically used by a dentist. It consists of a small mirror attached to a metal stick. It is tipically used by dentists to view places in the mouth that ordinarily would take an act of physical contortion to see, making it easier to find tooth decay or other potential oral problems that would otherwise go undetected, but it also provides an easy way to move a tongue or push on the inside of your cheek without doing so with their hands.