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Flexural Strength Values (flexural + strength_value)
Selected AbstractsChanges in the mechanical properties of tooth-colored direct restorative materials in relation to timePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2003Gülbin Sayg Abstract The objective of this study was to determine the flexural strength, flexural modulus, Vickers hardness of a packable composite (Surefil), and an ormocer (Definite) in comparison with a microhybrid composite (Z-100), a microfil composite (Silux Plus) and a polyacid-modified composite resin (Dyract). Flexural strength and flexural modulus were determined using a three-point bending device. Microhardness was measured with a Vickers indentor. The specimens of each material were prepared according to manufacturer's instructions. The specimens were stored in artificial saliva at pH 6, all at 37°C. The groups were tested at the beginning of the test, at 3 months and at 6 months. Flexural strength values of Surefil and Definite showed a progressive increase. The highest MPa values were determined for Surefil (134.4,MPa) and the lowest MPa values were obtained for Dyract (59.6,MPa). The highest flexural modulus values were revealed for Surefil (10.000 GPa). Z-100, Silux Plus and Definite showed a tendency to decline in relation to time for their flexural modulus. GPa values of Silux Plus were stable at 3 and 6 months. Vickers hardness numbers showed that Surefil was the hardest and Dyract was the weakest material. Copyright © 2003 John Wiley & Sons, Ltd. [source] Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentinDENTAL TRAUMATOLOGY, Issue 1 2009Monika Marending These materials have a disinfecting capacity similar to Ca(OH)2, but bear the advantage of bioactivity. However, because bioactive glasses initially act as alkaline biocides just as Ca(OH)2 does, they may also negatively affect mechanical dentin properties over time. This was assessed in the current study using standardized human root dentin bars. Specimens were immersed in 1:20 (wt vol,1) suspensions of nanometric bioactive glass 45S5 or calcium hydroxide for 1, 10, or 30 days. Control specimens were immersed in pure saline for 30 days (n = 20 per group). Subsequently, modulus of elasticity (E) and flexural strength (FS) of the specimens were determined. Results were compared between groups using one-way anova and Scheffé's post-hoc test. Ca(OH)2 caused a significant (P < 0.001) 35% drop in mean flexural strength values compared to the control treatment after 10 days. No further change was observed between 10 days and 30 days. Bioactive glass caused a 20% drop in mean flexural strength as compared to the control after 10 days. However, this difference did not reach statistical significance (P > 0.05). No effects of either material on dentin modulus of elasticity values were observed. It was concluded that the calcium hydroxide suspension affected the dentin more than the bioactive glass counterpart; however, the effect was self-limiting and probably restricted to superficial dentin layers, as suggested by the mere decrease in flexural strength but not in modulus of elasticity values. [source] Manufacturing, mechanical characterization, and in vitro performance of bioactive glass 13,93 fibersJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006E. Pirhonen Abstract Fibers were manufactured from the bioactive glass 13,93 by melt spinning. The fibers were further characterized by measuring their tensile and flexural strength, and their in vitro performance was characterized by immersing them in simulated body fluid, which analyzed changes in their mass, their flexural strength, and surface reactions. The strength of glass fibers is highly dependent on fiber diameter, test method, and possible surface flaws, for example, cracks due to abrasion. In this study, the thinnest fibers (diameter between 24 and 33 ,m) possessed the highest average tensile strength of 861 MPa. The flexural strength was initially 1353.5 MPa and it remained at that level for 2 weeks. The Weibull modulus for both tensile and flexural strength values was initially about 2.1. The flexural strength started to decrease and was only ,20% of the initial strength after 5 weeks. During the weeks 5,40, only a slight decrease was detected. The flexural modulus decreased steadily from 68 to 40 GPa during this period. The weight of the samples initially decreased due to leaching of ions and further started to increase due to precipitation of calcium phosphate on the fiber surfaces. The mass change of the bioactive glass fibers was dependent on the surface area rather than initial weight of the sample. The compositional analysis of the fiber surface after 24 h and 5 weeks immersion did confirm the initial leaching of ions and later the precipitation of a calcium phosphate layer on the bioactive glass 13,93 fiber surface in vitro. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Fracture Strength of Plate and Tubular Forms of Monolithic Silicon Carbide Produced by Chemical Vapor DepositionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2002Brian Vern Cockeram The fracture strength of silicon carbide (SiC) plate deposits produced by chemical vapor deposition (CVD) was determined from room temperature to 1500°C using a standard 4-point flexural test method (ASTM C1161). CVD SiC materials produced by two different manufacturers are shown to have only slightly different flexural strength values, which appear to result from differences in microstructure. Although CVD deposition of SiC results in a textured grain structure, the flexural strength was shown to be independent of the CVD growth direction. The orientation of machining marks was shown to have the most significant influence on flexural strength, as expected. The fracture strength of tubular forms of SiC produced by CVD deposition directly onto a mandrel was comparable to flexural bars machined from a plate deposit. The tubular (O-ring) specimens were much smaller in volume than the flexural bars, and higher strength values are predicted based on Weibull statistical theory for the O-ring specimens. Differences in microstructure between the plate deposits and deposits made on a mandrel result in different flaw distributions and comparable strength values for the flexural bar and O-ring specimens. These results indicate that compression testing of O-rings provides a more accurate strength measurement for tubular product forms of SiC due to more representative flaw distributions. 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