Today, injectable dermal fillers based on hyaluronic acid are very popular.
They have a number of advantages: efficiency, safety, have a natural and long-lasting effect with a minimal recovery period.
Depending on the concentration of hyaluronic acid and the method of its binding, fillers have different physical, including rheological properties.
Exclusively for estet-portal.com dermatovenereologist, cosmetologist, international trainer in contouring Yulia Dyachenko spoke about the main rheological properties of fillers and the features of their use in various areas of the face.
Which physical properties of fillers are rheological
Yu.D.: For us, cosmetologists, it is very important to understand the basic physical characteristics of fillers, including rheological properties.
Without this knowledge, we will not be able to select an effective drug for a patient with certain indications and certain injection goals.
Therefore, the doctor should look at the characteristics of the drug on the package before using it and ask the manufacturer to provide him with several studies.
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One of the most important rheological properties of fillers is the value G* («gel hardness"), which is the ratio of viscosity and elasticity.
Preparations that are not cohesive, i.e. have a small adhesive force of the substance - are inversely proportional to the G value.
Cohesivity – the ability of a gel to remain a homogeneous substance, a single whole.
For maximum efficiency, a filler requires a combination of two properties: plasticity and elasticity.
Those preparations that remain well and stable in the injection site, have high cohesiveness and are able to withstand external pressure.
However, having a high resistance and deformation profile, they can contribute to excessive swelling.
This is unacceptable, for example, on the back of the nose, as ischemia of the surrounding tissues may develop.
Therefore, it is important to know the concentration of the molecular weight of the drug, the amount of stabilizers in it and the ratio of the plastic component (G*) to the elastic component (G”).
Technological evolution of hyaluronic acid fillers
In which areas the rheological properties of fillers are especially important
Y.D.: Facial areas such as palpebromalar sulcus, dorsal bridge of the nose, lip area and temporal region zone have their own anatomical features, which will determine the choice of filler characteristics.
There is such a correlation: the thinner the zone (for example, the nasolacrimal sulcus), the less elasticity the drug should have.
Another example – back of the nose, which is covered with dense skin and has almost no subcutaneous fat.
For such areas, the minimum amount of the drug with a high G index * is used, which will ensure a lasting effect and protect against migration of the drug into nearby tissues.
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