Your Invisalign aligners are fabricated from medical grade polyurethane resin, containing methylene diphenyl diisocyanate and 1.6-hexanediol, that is not only exceptionally strong and durable but is also virtually invisible when worn. Invisalign does not contain any hazardous or harmful materials, such as phthalate plasticizers or Bisphenol-A (BPA), and is thus approved by the U.S. Food and Drug Administration (FDA) and United States Pharmacopeia (USP) for oral use.