Repair or maintenance of cutting machines, polishing machines and grinding machines for dentistry and dental technicians; repair or maintenance of dental CAD/ CAM equipment and dental technician equipment; repair or maintenance of metal engraving machines and apparatus, glass engraving machinery and equipment, ceramics engraving machines and apparatus, resin engraving machines and apparatus, synthetic resin engraving machines and apparatus, stone engraving machines and apparatus, wood engraving machines and apparatus, metalworking machines and apparatus, glass processing machines and apparatus, ceramics processing machines and apparatus, resin processing machines and apparatus, synthetic resin processing machines and apparatus, stone working machines and apparatus, wood processing machines and apparatus; repair or maintenance of metal, glass, ceramics, resin, synthetic resin, stone, wood cutting machines and apparatus; repair or maintenance of 3D printers and their fittings; repair or maintenance of computers and computer peripherals that store computer software that supports the cleaning of surgical instruments by reading the barcodes marked on the surgical instruments used and showing the processes and procedures for cleaning the surgical instruments; repair or maintenance of computers that store computer software for surgical instrument management to check whether surgical instruments are all available and to manage the usage history, cleaning history, sterilization history of the surgical instruments used; repair or maintenance of barcode readers for reading barcodes on medical machines and apparatus; repair or maintenance of electronic machines, apparatus and their parts; repair or maintenance of medical machines and apparatus