Malocclusion is a poor fit (alignment) of the teeth and jaws. An overjet is when the lower teeth are too far behind the upper front teeth. An underbite is when the upper front teeth are too far behind the lower teeth.

A common cause of malocclusion is teeth that have too much or too little room in the jaw. As a result, teeth may grow or drift out of place. Some people refer to it as having crooked teeth or a "poor bite."