The mentalis muscle, which together with the jaw bone forms the chin, can be hyperactive or too large, resulting in an appearance to the lower face that is less than ideal. For some people, chronic spasm of the muscle makes the chin move in an uncontrollable fashion, resulting in short lines that mark the skin of the chin, creating a ‘dimpled/pebblestone’ appearance.
Some people also have a liner crease/shadow under the lip and above the chin, or a very narrow chin giving the appearance of a retracted face. All of these can be corrected with Botox to the chin muscle