Fillers are a non-surgical procedure that involves injecting a substance under the skin to restore volume to sunken areas and reduce wrinkles. Hyaluronic acid (HA), for example, is a substance naturally present in the skin and is widely used due to its safety and reversibility; if necessary, it can be dissolved and adjusted using the enzyme hyaluronidase. Other options include calcium hydroxyapatite (CaHA), which stimulates collagen production; poly-L-lactic acid (PLLA); PMMA, which has semi-permanent properties; and autologous fat. For HA fillers, products with different gel viscosities and firmness are selected and used depending on the treatment area, such as nasolabial folds, the corners of the mouth, cheeks, lips, and under the eyes (tear troughs). The duration of results varies significantly depending on the type and injection site; while HA results generally last from several months to about one year, individual results may vary. Bruising, swelling, asymmetry, and nodules may occur, and although rare, serious complications such as vascular occlusion have been reported; therefore, you should thoroughly discuss product selection and injection sites with a specialist. This information is for reference only and does not constitute a diagnosis. Please consult a specialist regarding actual procedures.
[Source] https://my.clevelandclinic.org/health/treatments/22667-dermal-fillers · https://dermnetnz.org/topics/hyaluronic-acid-implant