There are two types of filler materials: non-biodegradable (permanent) and biodegradable (nonpermanent) filler.
Permanent Fillers (Silicone, polyacrylamide, polyalkylamide): The long-term results of permanent fillers are not yet well known. The most common complication of permanent fillers is granuloma formation. Due to its serious side effects, the FDA outlawed the use of silicone as a filler material in 1991.
Collagen: It was the most preferred nonpermanent filler material before hyaluronic acid. Animal-derived collagen may cause a hypersensitivity reaction. If animal-derived collagen is to be used, a pretest should be performed before the filler application. The pretest result is evaluated after 1 month, if it does not cause a problem, the collagen filler can be used after that. Human-derived collagen does not require such a pretest. Since there will be volume loss in the applied collagen filler over time, slightly more injections are made than the required amount.
Hyaluronic acid: Hyaluronic acid is the most widely used filler material for facial wrinkles all over the world. Hyaluronic acid is a glycosaminoglycone. It is hydrophilic, so it retains water and increases skin tension. Hyaluronic acid can be of avian (Hylafrom) or bacterial origin (Restylane / Juvederm /HydraFill). Hyaluronic acid is a safe product; it has FDA approval in the USA. It is not allergic; there is no need for pretest before application.