Evaluating fillers performance in motion: Teoxane introduces two new rheological parameters

Among all dermal fillers, hyaluronic acid (HA)-based gels have gained tremendous interest for the past 20 years. Natural and immediate outcomes, longevity and safety are part of the qualities that one can benefit from using them, alone, or combined with other dermatologic solutions¹ . When manufacturing such dermal fillers, HA chain integrity is often impacted by temperature or pH, with potential safety issues² . Anticipating those safety issues and mastering mechanical properties of HA-based gels by ensuring HA integrity has then become a top priority for Teoxane.

Introducing a range of 4 resilient HA fillers, Teoxane improved HA chain integrity with a bespoke technology (Preserved Network), better preserving long HA chains, therefore requiring minimum amounts of crosslinking. Such manufacturing processes allow dermal filler to better adapt to muscles movements  in dynamic facial motion^3,4 .

Historically, the elastic modulus G’ was used to characterize fillers but was shown not to be sufficient to describe their performance, especially in motion, since G' is measured in nearly static conditions⁵ . Aiming at better assessing said properties, Teoxane introduced two new rheological parameters measuring the propensity of a filler to deform and thus adapt to facial animation for natural-looking results⁶ .

The first parameter, called Strength, illustrates the range of stresses and deformation a dermal filler can endure while preserving its elastic modulus G’. This range is called the linear viscoelastic region (LVER). So to speak, Strength reflects the range of stresses over which a gel can still deliver its mechanical performance without disruption.
The second parameter, termed as Stretch, represents the ability of a gel to deform and adapt to stresses due to tissue stretching, such as upon smiling for example.

To establish the accuracy of those parameters, they were tested on a library of dermal fillers chosen among market leaders. All fillers were crosslinked HA gels and produced with different manufacturing technologies. Various indications and class of fillers were included in the library.

Interestingly, within each filler range, dermal fillers designed for more superficial indications showed the highest Stretch scores, whereas volumizers exhibited the highest Strength scores. When comparing fillers altogether, the Teosyal RHA^® products showed the largest Strength and Stretch ranges, eventually proving optimized mechanical gel properties well adapted to the respective product uses.

This study highlights that the elastic modulus G’ on its own is no longer sufficient to predict in vivo behavior of dermal fillers due to its assessment’s static conditions. Specifically designed to provide accurate information on rheological properties to injectors, Strength and Stretch concepts paved the way to a new, optimized way of characterizing dermal fillers performance.

You can read the full article by clicking here: https://pubmed.ncbi.nlm.nih.gov/33492870