title: Development of casting investment preventing blackening of noble metal alloys. Part 4: effect of Mg(OH)2 and Ca(OH)2 as additives.
abstract: The objective of this study was to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. Experimental investments were prepared using a gypsum-bonded investment in which a hydroxide, namely Mg(OH)2 or Ca(OH)2, was added. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The addition of both hydroxides showed a significant effect on the color of as-cast surfaces, which was improved with increase in additive content. When Mg(OH)2 or Ca(OH)2 was added at more than 4.0 mass% to the investment, it was useful in preventing the blackening of the as-cast surfaces of an Ag-Pd-Cu-Au alloy. As for differences in the effects between Mg(OH)2 and Ca(OH)2, they were not found.
authors.affiliation: Department of Dental Materials Science, School of Life Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Niigata City, Niigata 951-8580, Japan. anakai@ngt.ndu.ac.jp
authors.forename: Akira
authors.initials: A
authors.lastname: Nakai
authors.forename: Hideo
authors.initials: H
authors.lastname: Ogura
mesh_terms: D002126:Calcium Hydroxide / Q000737:chemistry; D003116:Color; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D004055:Differential Thermal Analysis; D008276:Magnesium Hydroxide / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: C120982:Ag-Pd-Cu-Au alloy; D003722:Dental Alloys; D003734:Dental Casting Investment; D012822:Silicon Dioxide; D008276:Magnesium Hydroxide; D002126:Calcium Hydroxide