Dermal filler is a substance that is injected into the dermis of the skin. It can effectively treat sunken cheeks by plumping targeted areas. Although there are many different types of fillers, the most popular are hyaluronic acid (HA) fillers. Dermal fillers can have different structures and consistencies that make them more suitable for treatment of different areas. For example, when treating the cheeks, we use a filler that is firm and smooth in order to volumise and define the cheeks.