Biomaterial Database

The biaxial flexural strength of two pressable ceramic systems. 1999

M J Cattell, and J C Knowles, and R L Clarke, and E Lynch

Department of Conservative Dentistry, St. Bartholomew's, London, UK.

The biaxial flexural strength of Optimal pressable ceramics and IPS Empress pressable ceramics were tested, compared and the micro-structures and compositions explored. The materials evaluated were Optimal shaded (Opcs) and unshaded (Opcus) ceramics and IPS Empress shaded (Ems) and unshaded (Emus) ceramics. Twenty-one disc specimens per material were prepared, heat-treated and tested. The piston on three-ball test ASTM F394-78 (1991) was used to test the specimens in a universal testing machine at a crosshead speed of 0.15 mm/min. Specimens were viewed in a scanning electron microscope and X-ray diffraction used to determine the phases present. Mean strengths (MPa +/- SD) were: Ems 120.1 +/- 20.5, Emus 135.8 +/- 16.0, Opcs 139.1 +/- 14.3 and Opcus 138.0 +/- 11.5. There was no statistically significant difference between Optimal shaded, Optimal unshaded and Empress unshaded strength values (p > 0.05). Empress shaded strength values were significantly lower than the other materials tested (p < 0.05). Weibull analysis provided m values: Ems 6.1, Emus 10.2, Opcs 12.8 and Opcus 13.9 and 1% and 5% probabilities of failure. Secondary electron imaging revealed a dense dispersal of leucite crystals in the glassy matrix of the Optimal ceramics of an average size 5.5 +/- 9.7 micron 2 for the Optimal shaded ceramic and 6.6 +/- 13.3 micron 2 for the Optimal unshaded ceramic. Leucite crystal agglomerates were evident for the Empress shaded material and a uniform distribution of fine leucite crystals (1.9 +/- 1.8 micron 2) for the Empress unshaded ceramic. Crystal and matrix microcracking were present in most of the material microstructures, together with porosity and tabular alumina platelets in the Optimal ceramics. X-ray diffraction revealed the presence of tetragonal leucite and small amounts of cubic leucite. Optimal ceramics and Empress unshaded ceramic provided higher strength and Weibull m values compared with Empress shaded ceramic. Inherent material defects were characterised and cubic leucite was identified.

UI	MeSH Term	Description	Entries
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
D008855	Microscopy, Electron, Scanning	Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.	Scanning Electron Microscopy,Electron Scanning Microscopy,Electron Microscopies, Scanning,Electron Microscopy, Scanning,Electron Scanning Microscopies,Microscopies, Electron Scanning,Microscopies, Scanning Electron,Microscopy, Electron Scanning,Microscopy, Scanning Electron,Scanning Electron Microscopies,Scanning Microscopies, Electron,Scanning Microscopy, Electron
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
D003776	Dental Porcelain	A type of porcelain used in dental restorations, either jacket crowns or inlays, artificial teeth, or metal-ceramic crowns. It is essentially a mixture of particles of feldspar and quartz, the feldspar melting first and providing a glass matrix for the quartz. Dental porcelain is produced by mixing ceramic powder (a mixture of quartz, kaolin, pigments, opacifiers, a suitable flux, and other substances) with distilled water. (From Jablonski's Dictionary of Dentistry, 1992)	Porcelain,Porcelain, Dental,Dental Porcelains,Porcelains,Porcelains, Dental
D003799	Dental Stress Analysis	The description and measurement of the various factors that produce physical stress upon dental restorations, prostheses, or appliances, materials associated with them, or the natural oral structures.	Analyses, Dental Stress,Analysis, Dental Stress,Stress Analyses, Dental,Stress Analysis, Dental,Dental Stress Analyses
D004577	Electron Probe Microanalysis	Identification and measurement of ELEMENTS and their location based on the fact that X-RAYS emitted by an element excited by an electron beam have a wavelength characteristic of that element and an intensity related to its concentration. It is performed with an electron microscope fitted with an x-ray spectrometer, in scanning or transmission mode.	Microscopy, Electron, X-Ray Microanalysis,Spectrometry, X-Ray Emission, Electron Microscopic,Spectrometry, X-Ray Emission, Electron Probe,X-Ray Emission Spectrometry, Electron Microscopic,X-Ray Emission Spectrometry, Electron Probe,X-Ray Microanalysis, Electron Microscopic,X-Ray Microanalysis, Electron Probe,Microanalysis, Electron Probe,Spectrometry, X Ray Emission, Electron Microscopic,Spectrometry, X Ray Emission, Electron Probe,X Ray Emission Spectrometry, Electron Microscopic,X Ray Emission Spectrometry, Electron Probe,X-Ray Microanalysis,Electron Probe Microanalyses,Microanalyses, Electron Probe,Microanalysis, X-Ray,Probe Microanalyses, Electron,Probe Microanalysis, Electron,X Ray Microanalysis,X Ray Microanalysis, Electron Microscopic,X Ray Microanalysis, Electron Probe
D000538	Aluminum Silicates	Any of the numerous types of clay which contain varying proportions of Al2O3 and SiO2. They are made synthetically by heating aluminum fluoride at 1000-2000 degrees C with silica and water vapor. (From Hawley's Condensed Chemical Dictionary, 11th ed)	Aluminum Silicate,Silicate, Aluminum,Silicates, Aluminum
D000704	Analysis of Variance	A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.	ANOVA,Analysis, Variance,Variance Analysis,Analyses, Variance,Variance Analyses
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013499	Surface Properties	Characteristics or attributes of the outer boundaries of objects, including molecules.	Properties, Surface,Property, Surface,Surface Property