NiTi or Stainless Steel wires are coated with Teflon/5META/Tooth colored epoxy resins. 4 Coating resources are synthetic resin or plastic resins which include epoxy resins.3 Coating enhances esthetics and decreases friction but There are many cons far too. Difficult or crunchy foods: Biting into foods like corn about the cob, apples, and popcorn