Water Absorption and 3D Expansion of Different Injectable Hyaluronic Acids

Abstract

Hyaluronic acid’s water absorption and expansion capacities define a filler’s ability to lift the tissues. Therefore, studying these properties is essential to better understand filler’s clinical performance. The aim of this study was to evaluate and compare water absorption and expansion (bidimensional and three-dimensional) of five Fillmed fillers (Universal, Fine Lines, Volume, Lips and Lips Soft). Water absorption was measured through swelling ratio 24 hours post-hydration. For two-dimensional expansion, samples were analysed quantitatively and qualitatively, using calibrated photographs, before and two hours after hydration. Three-dimensional volume was evaluated before and immediately after injecting the fillers, and 30 minutes, 2 hours and 24 hours post-injection in ex vivo pig skin. The tissue was scanned with the 3Shape TRIOS scanner and resulting STL files were compared. Group comparisons were analyzed with the one-way ANOVA test, and a p-value ≤ 0,05 was established. Lips showed a statistically higher swelling ratio than other fillers (p < 0,05). Fine Lines had the lowest swelling ratio, even if only statistically significant when compared to Universal (p= 0,021). Fine Lines had a significantly higher initial bidimensional width than all fillers (p <0,05) except Lips Soft. 24 hours post-injection, Fine Lines had the highest three-dimensional volume, which was statistically higher than Volume’s (p= 0,049). All fillers absorbed water and expanded, with Fine Lines tending to have the highest three-dimensional expansion, despite its lowest viscosity and water absorption. Further studies with larger sample sizes are needed to investigate the influence of other properties over water absorption and expansion.