To fill is to position a material of diverse nature in the correct anatomical plane with the objective of recreating, restituting or modelling volumetrically the cutaneous, subcutaneous or mucosal surface, with the goal of achieving a rejuvenating effect or obtaining an accentuation of a physical attribute or a physiological improvement.
An ideal filler, consists in a substance easy to manipulate (preservation and administration), inexpensive, biocompatible, non-immunogenic, non-toxic, non-carcinogenic, no inflammatory (acute /chronic), non-migratory, long lasting, highly volumetric, painless, with no downtime and versatile. Unfortunately perfection is a condition difficult to achieve, so one should obtain the right balance between the strengths and weakness of each substance, to make the right election of the material, for each case in particular. The better election will depend on the knowledge of the materials and the special expectations of each patient. The best result will be obtained therefore, with the right choice of the material, its correct anatomical administration, the use of the appropriate quantity, and a satisfactory evolution in time. There is not a single material that can correct all defects, or be injected in any skin layer; so many times they have to be combined for an appropriate result.
Fillers are classified based on their origin in natural (xenogenic, homogenic and autogenic) and synthetic. Because of the recent combination of natural and synthetic products, at present is more suitable to classify them according to their lasting in temporal and permanent.
Knowledge of the composition, physiological tissue reaction, and lasting time, of the different substances is crucial to avoid and treat fillers adverse effects.