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CAD/CAM international magazine of digital dentistry No. 3, 2016

| review thermoplastic materials 16 CAD/CAM 3 2016 Thermoplastic materials in dental technology Author: Claudia Herrmann, Germany Thermoplastic materials have been used in aviation andspaceengineeringforalongtime.Owingtotheir high mechanical strength and low modulus of elas- ticity, they have begun to increasingly replace metal in many manufacturing industries too, particularly in those where metal has been the dominant choice until now. Implants for intervertebral discs, as well as hipandkneejoints,aremadeofPEEK,athermoplastic polymer. Four million implants have been fitted during the last 15 years with outstanding success. In recent years, thermoplastic materials have also been used in dental technology. This article discusses a number of common plastic materials that have become alternatives for use in the manufacture of non-metal telescopic dentures. About15yearsago,thefirstattemptsweremade,not without initial problems, to produce non-metal tele- scopic dentures. These dentures were made by injec- tion moulding using a polyamide (PA) in the dental laboratory. A wax mould of the framework, bar and secondarycrownsismadeasanintegralpart,embed- ded in plaster in a flask and the wax boiled out. The plasticmaterial,whichisavailableinthelaboratoryas granularmaterial,isheatedintheinjectionmoulding device and injected into the mould. After a period of cooling, which should not be shorter than specified, the prosthesis is removed from the mould and fin- ished. Special milling cutters are needed because the material tends to become viscid when cut. Very importantly, absolutely no metal must be en- trained.Ifthedentureweretocutbyatoolpreviously used for cutting metal, minute metal particles would be incorporated into the thermoplastic material by the milling cutter. Friction would easily be controlled by expansion plaster. 32016

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