As the years go by, the outer shell of the human body changes its appearance. These skin alterations are often narrowly focused on facial wrinkles, one of the most visible signs of the aging process. Therefore, the majority of approaches intending to reverse skin-aging signs are focused on the treatment of wrinkles.1 However, it recently became evident, that simply treating wrinkles is insufficient to restore a youthful facial appearance. Moreover, the loss of facial volume beneath the skin is considered to be the major contributor to the appearance of advanced age.2,3
In a youthful face, deep and superficial fat is balanced, creating a round and even distribution of facial fullness.4-6 However, as skin ages abrupt contour changes occur including sagging, prominent nasolabial folds, hollow cheeks or deep circles under the eyes.4,7 For many years, these skin aging signs were believed to be caused by gravity,8,9 but recent research elucidated that subcutaneous adipose fat of the face is partitioned into multiple, discrete compartments, or fat pads, rather than being one confluent mass.6 With aging, atrophy of adipose tissues of the face, due to a progressive breakdown of subcutaneous cell components occurs, resulting in inferior volume shift inside each compartment as well as migration of some compartments independently of each other, appearing then as separate entities.4,10 The reorganization of the fat pads with aging, together with craniofacial remodeling consequently led to predictable facial volume loss resulting in dramatic changes to the overall contour of the face.
Various surgical options to treat facial volume loss are available including cheek implants or face-lift in combination with volume redistribution.11 Although effective, surgery always implies the inherent risk of anesthesia and requires substantial time for recovery. Additional procedures, in which volume is augmented is the use of autologous fat. However, this technique requires a previous invasive procedure (eg, liposuction) to harvest subcutaneous adipocytes, which adds to the risks of this type of treatment.12,13 Due to recent advances in aesthetic dermatology, volume restoration can also be accomplished with minimal risk by using injectable dermal fillers.
The purpose of this article is to review the injectable dermal fillers for volume augmentation and restoration approved by the US Food and Drug Administration (FDA), namely poly-L-lactic acid (PLLA), calcium hydroxylapatite (CaHA), and low-molecular- weight (LMW) 20mg/ml hyaluronic acid (HA).
Injectable Volume Fillers
The first dermal injections for tissue augmentation were described in the late 19th century, when Franz Neuber used autologous fat as filler material to correct depressed facial defects. Shortly thereafter, in 1899, the physician Robert Gersuny introduced paraffin for tissue augmentation, which eventually became a very common filler material for several years, until the high incidence of severe side effect became evident.14
Towards the end of the last century numerous injectable dermal fillers were developed, such as collagen and hyaluronic acid.15 Although the introduction of these dermal fillers was a turning point for the treatment of facial wrinkles, the realization that using injectable filler implants in the deep dermal and