title: [Cast fractures of dental Ni-Cr alloys (author's transl)].
abstract: Cast fractures of Ni-Cr alloys were investigated by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron-probe microanalysis, density measurements, setting and thermal expansion measurements and compressive tests. Three-Ni-Cr alloys for crowns and bridges were cast in spiral configurations by an argon-arc pressured type or an induction argon-pressured type-casting machine. The amount of cast fracture increase with an increase in cast temperature, but not with an increase of holding time at cast temperature. Ni-Cr alloys have more cast fractures in a phosphate-bonded investment than in a gypsum-bonded cristobalite investment. Fracture surfaces have an exposed dendrite structure, indicating the presence of cast porosity. The trigger of cast crack can be a cast porosity and the propagation of crack to fracture may be mainly due to the strength of investments.
mesh_terms: D002858:Chromium Alloys; D003442:Crowns; D003735:Dental Casting Technique; D003799:Dental Stress Analysis; D009532:Nickel; D013718:Tensile Strength
chemical_list: D002858:Chromium Alloys; D009532:Nickel