Traditionally, analysis of HA gels is limited to the elastic modulus G′, the viscous modulus G″, the phase angle δ (or tan δ), being connected to the former quantities (tan δ = G″/G′), and the complex viscosity η*. It is therefore essential to characterize their rheological profiles accurately.
#Janetter bourdon skin#
16, 17 As the primary function of all implants is to fill skin wrinkles and folds and restore facial volumes with good biointegration, their mechanical behavior is a key feature of their clinical use and performance. These less rigidly crosslinked HA chains are presumed to allow implants to better accompany and adapt to mechanical deformations such as muscle movements driving dynamic facial motion. 12, 15 TEOXANE Laboratories (Geneva, Switzerland) introduced a range of 4 Resilient HA fillers (TEOSYAL RHA ®) manufactured with a unique technology (Preserved Network) that is specifically designed to improve HA chain integrity throughout the gel manufacturing, thus better preserving long (high Mw) HA chains that in turn require low amounts of crosslinker to achieve clinically desirable mechanical properties and durability. 13, 14 Therefore, there is an increasing need to master the mechanical properties of the gels, anticipate their safety profiles, and develop mild manufacturing conditions to ensure HA integrity throughout the process. Accordingly, the manufactured HA gels may significantly differ in its final in vivo characteristics with potential safety issues. 11 Indeed, the usual manufacturing conditions (heat, alkali pH, and sterilization) are prone to degrade HA gels 12 and release low-Mw soluble HA (sHA) fragments. 8– 10 Hyaluronic acid chains are sensitive to manufacturing process parameters such as high temperatures and strong acidic and alkali pH. 6, 7 According to their chemical compositions, such as HA concentration, Mw of the HA, and the crosslinker content, each commercially available HA-based gel exhibits unique viscoelastic and biophysical properties intended to match its product indications. 3– 5 Many HA dermal fillers are generally composed of high-molecular weight (Mw) HA, a naturally occurring polysaccharide in the skin, containing the repetition of d-glucuronic acid and d-N-acetyl glucosamine disaccharide units, crosslinked with difunctional molecules, or crosslinkers, on the carboxyl or the hydroxyl moieties. Among all dermal fillers, hyaluronic acid (HA)-based gels have garnered increased attention over the past decades because of immediate and natural-looking visual effects on skin as well as being proven to be safe, long lasting, and easy-to-use alone or in combined treatments.
1, 2 They help by reducing the intensity of skin folds, wrinkles, lines, and creating facial volume in specific areas. Soft tissue fillers are injectable soft gels aimed to counteract skin depression and changes because of tissue ageing and loss.
0 kommentar(er)
