Hyaluronic acid (HA) fillers have become the most popular material for facial volume augmentation and wrinkle correction. Several filler brands are currently on the market all around the world and their features are extremely variable; for this reason, most users are unaware of their differences. The study of filler rheology has become a wellspring of knowledge, differentiating HA fillers, although these properties are not described thoroughly by the manufacturers. The authors of this review describe the more useful rheological properties that can help clinicians understand filler characteristics and the likely correlation of these features with clinical outcomes.

BACKGROUND: Certain manufacturing processes confer distinctive rheologic features to hyaluronic acid (HA), ensuring long-lasting effects. Skin quality improvement and the volumizing effects of the DEF_CL volumizer filler, a sterile, biodegradable, viscoelastic, transparent, isotonic, and homogenized injectable cross-linked high G′ filler for the treatment of moderate-to-severe age-related midface changes, were initially documented at 6 months after the first injection. OBJECTIVE: The authors aimed to objectively evaluate the effects of the DEF_CL volumizer filler in improving skin density, thickness, and biomechanical properties and on tissue volume augmentation in women with midface volume loss after 12 months. MATERIALS AND METHODS: Fifty women with midface volume loss were recruited in this prospective, noncomparative, single-center, postmarket study. The authors report changes in skin density, thickness, and quality and subjective and objective evaluation of facial and/or cheek volume augmentation using the Global Aesthetic Improvement Scale, as well as injection site reactions and adverse events. RESULTS: Improvements in skin quality and thickness and volumization were maintained 12 months after the first injection. Injector and patient satisfaction were highly rated with only mild adverse reactions observed. CONCLUSION: Skin improvement and volumizing effects persisted in patients treated with the DEF_CL volumizer after 12 months.