Dermal fillers are gel-like substances that are FDA-approved for injection beneath the skin, and a select group of these fillers, which have the appropriate level of flexibility for the dynamic mouth area, are used to augment the lips. Lip fillers are in the same class of dermal fillers that is used to restore lost skin volume and treat other signs of aging. Board certified injectors use these dermal filler products to help you achieve a more plump, defined, or symmetrical lip appearance. The procedure includes up to 1 ml of filler for the first session.