The mouth is an opening into the body.  As a sexual object, it represents a substitution for the vagina.  It offers the dreamer a source of power over the "other" since the mouth is a gateway to the intellect and reason.  The lips provide a sensual connection to sexual desire.  The mouth is not only a way the human body consumes nourishment, but it provides a means for communication, taste and arousal. 
Botticelli