Spontaneous and induced degradation of dermal fillers: A review

Dermal fillers are among the most versatile tools in esthetic medicine. A broad range of temporary, semipermanent, and permanent filler products is on the market. We performed a narrative review on spontaneous and induced degradation of dermal fillers in vitro and in vivo. Hyaluronic acid-based fillers are the most frequently used temporary fillers. The products differ in their hyaluronic acid content, cross-linking, and rheological parameters. Endogenous hyaluronidase and reactive oxygen species are responsible for the spontaneous degradation of these fillers. Hyaluronidase digests the filler material by cleavage of the β-1,4 glycosidic linkage between N-acetyl-glucosamine and d-glucuronic acid. The enzyme can be used for treatment of medical and cosmetic adverse events due to hyaluronic acid-based filler. Higher hyaluronidase content and higher degree of cross-linking are major factors contributing to filler persistence over time. Semipermanent fillers are poly-(d),l-lactic acid and calcium hydroxylapatite. These filler types are decomposed by hydrolysis and osteoclastic enzymes. They usually persist up to 2 years, in single patients even more than 5 years. Sodium thiosulfate can stimulate degradation of calcium hydroxylapatite, but it is slow acting and not effective in case of emergency. Permanent fillers may show some kind of modification in situ, but spontaneous or induced degradation has not been documented. Once implanted the permanent fillers remain lifelong. Intralesional laser treatment supports the removal of permanent filler material as an alternative to surgery. Besides biocompatibility and toxicity, filler materials should also be assessed for degradation to improve patient safety.