As we age, the fat, muscles, bone, and skin in our face begins to thin. This loss of volume leads to either a sunken or sagging appearance of the face. Injectable poly-l-lactic acid is used to create structure, framework, and volume to the face. PLLA is known as a bio-stimulatory dermal filler, this means it stimulates your own skin to produce new collagen. Over time your skin breaks down PLLA into water and carbon dioxide. The effects of PLLA appear gradually over a few months, producing natural results.