A number of biological and synthetic injectable fillers havebeen developed for and used in soft-tissue augmentation andfacial contouring since the first attempts at fat transplantationin 1893. Cross-linked polyacrylamide hydrogel, a nondegradablefiller, has been approved for facial contouring in Europe,Australia, and Asian countries. The hydrogel itself producesthe filling effect. The foreign-body reaction is minimal andtransient, and fibrosis is seen only as thin strands of a vascularizednetwork of connective tissue fibers, which anchor the gelin place and prevent migration.1 The Food and Drug Administrationin the United States has not approved it, because ofconcerns about its efficacy and safety
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