Articles for orthodontics and prosthetics, especially retainers, welding parts, bands for use in repositioning teeth, bars, brackets, buccal tubes, expansion screws, wires and preformed wire parts, casting alloys for orthodontic and dental prosthetic purposes, appliances, articulations, attachments, accessories made of precious metals, springs, crowns, clamps, tubes, rings, root and crown posts, instruments as scissors, mirrors and pliers, instruments for surface treatment of teeth