Basics of dermal filler rheology.

[BACKGROUND] Hyaluronic acid injectable fillers are the most widely used dermal fillers to treat facial volume deficits, providing long-term facial aesthetic enhancement outcomes for the signs of aging and/or facial contouring.

[OBJECTIVES] The purpose of this article was to explain how rheology, the study of the flow of matter, can be used to help physicians differentiate between dermal fillers targeted to certain areas of the face.

[METHODS] This article describes how rheological properties affect performance when filler is used in various parts of the face and exposed to mechanical stress (shear deformation and compression/stretching forces) associated with daily facial animation and other commonly occurring external forces.

[RESULTS] Improving facial volume deficits with filler is linked mainly to gel viscoelasticity and cohesivity. These 2 properties set the level of resistance to lateral and vertical deformations of the filler and influence filler tissue integration through control of gel spreading.

[CONCLUSION] Selection of dermal filler with the right rheological properties is a key factor in achieving a natural-looking long-lasting desired aesthetic outcome.