The effect of potential investment expansion and hot strength on the fit of full crown castings made with phosphate-bonded investment. 1997

R Earnshaw, and E F Morey, and D C Edelman
School of Dental Studies, University of Sydney, NSW, Australia.

In an earlier investigation, it was shown that when full crowns are cast in gypsum-bonded investments, their relative inaccuracy is affected by both the investment's potential expansion and its hot strength. This study repeated the earlier one, but used a high-melting gold alloy and two phosphate-bonded investments. The investments were used under conditions which gave a range of potential expansions and hot strengths. Casting inaccuracies were determined both diametrally and axially. All castings showed distortion, which varied under the different conditions. All were oversized axially, by amounts varying from + 0.8% to +2.3%. Diametral inaccuracies ranged from -0.2% to +0.7%. Investment expansion had a strong effect on axial inaccuracy, but a negligible effect on diametral inaccuracy. Conversely, hot strength had a strong effect on diametral inaccuracy, but only a very weak effect on axial inaccuracy. With phosphate-bonded investments, both potential expansion and hot strength are important parameters of relative casting inaccuracy. In combination, these properties showed very strong correlations with both diametral and axial inaccuracies. The observed distortions were the result of anisotropic mould expansion and anisotropic alloy shrinkage. The best fit, and least distortion, occurred with an investment setting under dry conditions.

UI MeSH Term Description Entries
D007283 Inlay Casting Wax A mixture of several dental waxes, usually containing paraffin wax, ceresin, beeswax, resins, and other natural and synthetic waxes. It is used for making patterns to determine the shape of the metallic framework and other parts of removable partial dentures. (From Jablonski's Dictionary of Dentistry, 1992, p868) Casting Wax, Inlay,Wax, Inlay Casting
D008422 Materials Testing The testing of materials and devices, especially those used for PROSTHESES AND IMPLANTS; SUTURES; TISSUE ADHESIVES; etc., for hardness, strength, durability, safety, efficacy, and biocompatibility. Biocompatibility Testing,Biocompatible Materials Testing,Hemocompatibility Testing,Testing, Biocompatible Materials,Testing, Hemocompatible Materials,Hemocompatibility Testings,Hemocompatible Materials Testing,Materials Testing, Biocompatible,Materials Testing, Hemocompatible,Testing, Biocompatibility,Testing, Hemocompatibility,Testing, Materials,Testings, Biocompatibility
D010710 Phosphates Inorganic salts of phosphoric acid. Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D011312 Pressure A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Pressures
D012044 Regression Analysis Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable. Regression Diagnostics,Statistical Regression,Analysis, Regression,Analyses, Regression,Diagnostics, Regression,Regression Analyses,Regression, Statistical,Regressions, Statistical,Statistical Regressions
D002133 Calcium Sulfate A calcium salt that is used for a variety of purposes including: building materials, as a desiccant, in dentistry as an impression material, cast, or die, and in medicine for immobilizing casts and as a tablet excipient. It exists in various forms and states of hydration. Plaster of Paris is a mixture of powdered and heat-treated gypsum. Dental Gypsum,Dental Stone, Artificial,Gypsum,Plaster of Paris,Alabaster,Anhydrous Sulfate of Lime,Artificial Dental Stone,Calcium Sulfate (1:1), Dihydrate,Calcium Sulfate (1:1), Hemihydrate,Calcium Sulfate (2:1),Calcium Sulfate Dihydrate,Calcium Sulfate, Anhydrous,Calcium Sulfate, Dihydrate,Calcium Sulfate, Hemihydrate,Calcium Sulphate,Drierite,Gypsite,Gypsum, Dental,Karstenite,Stone, Artificial Dental
D002627 Chemistry, Physical The study of CHEMICAL PHENOMENA and processes in terms of the underlying PHYSICAL PHENOMENA and processes. Physical Chemistry,Chemistries, Physical,Physical Chemistries
D003442 Crowns A prosthetic restoration that reproduces the entire surface anatomy of the visible natural crown of a tooth. It may be partial (covering three or more surfaces of a tooth) or complete (covering all surfaces). It is made of gold or other metal, porcelain, or resin. Dental Crowns,Crown, Dental,Crowns, Dental,Dental Crown,Crown
D003734 Dental Casting Investment Material from which the casting mold is made in the fabrication of gold or cobalt-chromium castings. (Boucher's Clinical Dental Terminology, 4th ed, p168) Casting Investment, Dental,Casting Investments, Dental,Dental Casting Investments,Investment, Dental Casting,Investments, Dental Casting
D003735 Dental Casting Technique The process of producing a form or impression made of metal or plaster using a mold. Casting Technic, Dental,Casting Technics, Dental,Casting Technique, Dental,Casting Techniques, Dental,Dental Casting Technic,Dental Casting Technics,Dental Casting Techniques,Technic, Dental Casting,Technics, Dental Casting,Technique, Dental Casting,Techniques, Dental Casting

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