Materials for dental prosthesis, included in this class, namely, materials for crowns and bridges for dental use and for oral prophylaxis, in particular discs made from ceramics, from metals or metal alloys or from plastics as blanks for the fabrication of dental restorations; materials for facing artificial teeth and teeth prosthesis, in particular metal ceramics, dental ceramics and dental restoration compounds of plastic; dental restoration compounds of metal, precious metals and dental al...