Fracture Strength Of Samples Research Articles

Üç Farklı CEREC Omnicam Endokronun Kırılma Dayanıklılığı ve Kırılma Modlarının Karşılaştırılması: İn Vitro Bir Çalışma

Objective: The aim of this in vitro study was to evaluate fracture strength of porcelain endocrown produced by a computer aided design/computer aided manufacturing (CAD/CAM) system using different types of ceramic blocks. Material and Methods: Forty-five extracted human mandibular molars were divided randomly into 3 groups (n=15). Standardized endodontic treatment was applied the forty-five molars in 3 groups, received endocrown preparations. Experimental groups were; Group 1 (VS); Lithium silicate reinforced with zirconia (Vita Suprinity, Vita Zahnfabrick, Bad Säckingen, Germany), Group 2 (EM); Lithium silicate (IPS e.max CAD, Ivoclar Vivadent, Schaan, Lichtenstein) and Group 3 (CS); Resin nanoceramic (Cerasmart, GC, Tokyo, Japan). Restorations were cemented with dual-cure resin cement Variolink N (Ivoclar Vivadent, Schaan, Liechtenstein) and samples were stored in distilled water at 37°C for 24 hours. All samples were subjected to thermocycling for 5,000 cycles in water baths between 5°C and 55°C. The fracture strength of samples was determined under compressive loads at a 0.5 mm/min crosshead speed until fracture. The maximum fracture strength (Newton) values of the restorations were recorded. Fracture strength data were evaluated with one-way ANOVA (p=0.05). Results: The highest fracture strength values were observed in CS (2,379.6±483.07 N), which was significantly higher than the other groups (p0.05). Conclusion: Resin nanoceramic endocrowns produced using CEREC Omnicam system demonstrated significantly higher fracture strength values than the other groups.

Electrical and Mechanical Properties of Zirconia Based Cubic/Tetragonal Composite Electrolytes Prepared by Solution Coating Method

AbstractIn this study, cubic/tetragonal zirconia based composite electrolytes were prepared by coating of 8YSZ powders with zirconia. At first zirconia solution was prepared and coated over the surface of 8YSZ(8 mol.% yttria stabilized zirconia) powders. The resulting powders then were formed into cylindrical specimens and sintered at various temperatures. Microstructure and phase content of samples were characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques, respectively. The electrical conductivity of composite samples was studied by electrochemical impedance spectroscopy. In addition, hardness, toughness and fracture strength of samples were measured by Vickers microhardness indentation and ring on ring test, respectively. It was found that the homogeneous tetragonal/cubic composite electrolytes with improved electrical and mechanical properties at low temperatures can be obtained by this method.

Analytical stress characterization after different chip separation methods

Synchrotron white beam X-ray topography (SXRT) and photoelastic stress measurements were used to characterize resulting strain fields after mechanical dicing and laser grooving of bare silicon wafers. The distribution and propagation of the strain fields can be characterized by both methods. In contrast to mechanical dicing, the laser grooving process creates an inhomogeneous strain field. The influenced area is three times larger compared to mechanical dicing. The effect of the dicing procedure on the resulting mechanical fracture strength of the silicon chips was investigated by 3-point bending tests. The fracture strength of samples with an additional laser grooving process was significantly reduced under tensile load. The fracture pattern of the samples indicated that the strain field generated by the separation process causes initial points for μ-cracks propagation under mechanical load. This analysis can help to optimize dicing processes in order to attain a better reliability of chips with regard to process yields.

Pressureless sintering of internally synthesized SiC-TiB 2 composites with improved fracture strength

SiC-TiB 2 particulate composites were fabricated by converting TiO 2 to TiB 2 through the reaction between TiO 2, B 4C and C. The presence of initially very fine, in-situ created, TiB 2 particles increased driving force for sintering and enabled fabrication of a dense composite utilizing pressureless sintering and the liquid phase created between Al 2O 3 and Y 2O 3 additives. The effect of volume fraction of the in-situ formed TiB 2 on density, microstructure and flexural strength was discussed. It was found that the presence of TiB 2 particles suppressed the growth of SiC grains and enhanced fracture strength. The fracture strength of samples containing 12 vol% TiB 2 was more than 30% higher than that of the monolithic SiC. The effect of SiC grain size on fracture strength was also analyzed.