Rheological and Physicochemical Analysis of Dermal Fillers

Soft tissue fillers used to eliminate facial aging are increasing and varying. Minimally invasive procedures for the correction of age-related defects in the face have become the norm not only for superficial soft tissues such as skin and subcutaneous tissue, but also for the deep anatomical layers of the face. The widespread use of soft tissue fillers has increased with the introduction of hyaluronic acid fillers, which now account for approximately 80 percent of all fillers used for rejuvenation and volume correction.

The use of hyaluronic acid fillers is becoming widespread because they have low complication rates, good durability, are relatively economical and reversible.

Hyaluronic acid fillers are a hydrogel produced from cross-linked hyaluronic acid suspended in physiological or phosphate buffered solution.

Most modern hyaluronic acid fillers are derived from bacterial hyaluronic acid due to its reduced allergenic and immunogenic potential. That is, hyaluronic acid, which is generally obtained from animal sources such as amaranth, can retain impurities that can cause adverse reactions. In fact, not all fillers are the same and clinicians choose different products for different indications in their daily practice depending on their personal clinical experience. The choice is based mainly on direct use of the products and personal experience.

Understanding the fundamentals of each rheological and biophysical property and their clinical implications facilitates the selection of the right hyaluronic acid filler and appropriate injection plane for each specific use. It is clear that a filler used in the deep plane for the restoration of facial volume has different properties than a filler used for fine lines on the skin. Fillers for deep injections are generally defined as harder, while fillers for fine lines are defined as softer.

Soft fillers have lower viscosity and elasticity and tend to spread into soft tissue. So it is ideal for fine lines and wrinkles. Hardfills, on the other hand, have higher viscosity and flexibility and provide lift and support with negligible product migration. So it is ideal for volume restoration. However, neither statement can detail the behavior of the filler after injection and its interaction with the deforming forces acting on it. After injection, fillers are subjected to compression, shear, stretching, torsion due to muscle movements, soft tissue weight, pressure applied to external surfaces and the force of gravity. All these forces change the shape, distribution, duration and degree of correction of the defect resulting from the injected filler.

Moreover, each filler is defined by the manufacturers for the same indication, without taking into account that the rheological and physicochemical properties differ significantly between filler brands. That is, fillers can share the same indication while having different rheological, physical and chemical properties. An example of such a difference exists between two large families of hyaluronic acid agents: monophasic and biphasic fillers. Monophasic filler is a homogeneous mixture of cross-linked hyaluronic acid chains of high or low molecular weight. Generally, monophasic fillers have lower elasticity and higher viscosity than biphasic hyaluronic acid fillers. Improper use of these filler types reduces the quality of the final aesthetic results.

Whichever skin filler will be used, tests and analyzes to be carried out in advanced laboratories are extremely important to ensure that it is compatible with the person's body values.

given to businesses by our organization Among numerous testing, measurement, analysis and evaluation studies, there are also rheological and physicochemical analysis services of dermal fillers.