This is a great question with a lot of fascinating science behind it. Over the years, physicians using injectables were finding that as patients returned for follow-up sessions; they required less volume. Further study found that the placement of product, whether hyaluronic acid, calcium hydroxylappatite, or poly-l-lactic acid, not only causes fibroblasts to stretch; it also engages a cellular pathway (TGF-β). Through these two mechanisms, your own body makes more collagen.
Fibroblasts are cells in our dermis, our middle layer of skin, which make collagen. Collagen is the main structural protein in the scaffolding of the dermis. When we see sagging skin, most of what we see is loss of volume in the dermis, movement of normal fat pads, and loss of facial fat. In an interesting read, you’ll see that gravity was acquitted of playing a role in sagging skin (O’Connor, A., NY Times, Oct 26 2004). In this article, Dr. Lambros explains that what robs people of their youthful appearance is deflation; “it’s the loss of subcutaneous fat and volume.” While sun-damaged skin gets thinner and some of its elasticity decreases, it’s the volume loss that gives sagging skin.
Once your facial volume is repleted and your skin milieu is restored; you will not need the same amount. Patients are intrigued by the science behind injectables, as are many of my co-physicians in other specialties. These treatments are not simply aesthetic and passive but active biostimulatory treatments.