44 results match your criteria loads vickers

Biomechanical and morphological changes produced by ionizing radiation on bone tissue surrounding dental implant.

J Appl Oral Sci 2020 28;28:e20200191. Epub 2020 Sep 28.

Federal University of Uberlândia, School of Dentistry, Department of Oral and Maxillofacial Surgery, Uberlândia, MG, Brasil.

Objective: This study analyzed the effect of ionizing radiation on bone microarchitecture and biomechanical properties in the bone tissue surrounding a dental implant.

Methodology: Twenty rabbits received three dental morse taper junction implants: one in the left tibia and two in the right tibia. The animals were randomized into two groups: the nonirradiated group (control group) and the irradiated group, which received 30 Gy in a single dose 2 weeks after the implant procedure. Read More

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December 2020

Associations of Later-Life Education, the BDNF Val66Met Polymorphism and Cognitive Change in Older Adults.

J Prev Alzheimers Dis 2020 ;7(1):37-42

David D. Ward, Wicking Dementia Research and Education Centre, Private Bag 143, Hobart, Tasmania 7001, Australia.

In 358 participants of the Tasmanian Healthy Brain Project, we quantified the cognitive consequences of engaging in varying loads of university-level education in later life, and investigated whether or not BDNF Val66Met affected outcomes. Assessment of neuropsychological, health, and psychosocial function was undertaken at baseline, 12-month, and 24-month follow-up. Education load was positively associated with change in language processing performance, but this effect did not reach statistical significance (P = 0. Read More

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January 2020

The Effect of Thermocycling on Surface Layer Properties of Light Cured Polymer Matrix Ceramic Composites (PMCCs) Used in Sliding Friction Pair.

Materials (Basel) 2019 Aug 29;12(17). Epub 2019 Aug 29.

Department of Automation, Lublin University of Technology, Nadbystrzycka 36, 20-618 Lublin, Poland.

This paper discusses the problem of thermocycling effect of light-curing polymer-ceramic composites. Cyclic thermal shocks were simulated in laboratory conditions. As a rule, these loads were supposed to reproduce the actual conditions of biomaterials exploitation. Read More

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Effects of Curing Modes on the Microhardness of Resin-modified Glass Ionomer Cements.

Acta Stomatol Croat 2019 Mar;53(1):37-46

Department of Endodontics and Restorative Dental Medicine School of Dental Medicine University of Zagreb, Gundulićeva 5, Zagreb.

Objective: This study evaluated the effects of curing modes on surface microhardness of visible light-cured resin-modified glass ionomer cements (VLC RMGIC) and a giomer after different storage periods in comparison to auto-cured resin-modified glass ionomer cements (AC RMGIC).

Materials And Methods: The following materials were used: VLC RMIC: Fuji II LC Improved, Photac Fil Quick Aplicap, AC RMGIC: Fuji Plus, Fuji VIII and Giomer: Beautifil II. The measurements of microhardness were performed using a Vickers test (100 g loads were applied for 10 s) in the following time intervals: immediately after the recommended cure and after 1, 7 and 14 days of immersion in distilled water. Read More

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Influence of residual thermal stresses on the edge chipping resistance of PFM and veneered zirconia structures: Experimental and FEA study.

Dent Mater 2019 02 20;35(2):344-355. Epub 2018 Dec 20.

Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, Brazil.

Objective: Chipping fractures of the veneering porcelain are frequently reported for veneered all-ceramic crowns. In the present study, the edge chipping test is used to measure the toughness and the edge chipping resistance of veneered zirconia and porcelain-fused-to-metal (PFM). The aim is to describe an edge chipping method developed with the use of a universal testing machine and to verify the accuracy of this method to determine the influence of residual thermal stresses on the chipping fracture resistance of veneering porcelain. Read More

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February 2019

Machine Learning Directed Search for Ultraincompressible, Superhard Materials.

J Am Chem Soc 2018 08 30;140(31):9844-9853. Epub 2018 Jul 30.

Department of Chemistry , University of Houston , Houston , Texas 77204 , United States.

In the pursuit of materials with exceptional mechanical properties, a machine-learning model is developed to direct the synthetic efforts toward compounds with high hardness by predicting the elastic moduli as a proxy. This approach screens 118 287 compounds compiled in crystal structure databases for the materials with the highest bulk and shear moduli determined by support vector machine regression. Following these models, a ternary rhenium tungsten carbide and a quaternary molybdenum tungsten borocarbide are selected and synthesized at ambient pressure. Read More

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Tribo-Mechanical Properties of HVOF Deposited Fe₃Al Coatings Reinforced with TiB₂ Particles for Wear-Resistant Applications.

Materials (Basel) 2016 Feb 19;9(2). Epub 2016 Feb 19.

Département de génie des mines, de la métallurgie et des matériaux, Université Laval, Québec, QC G1V 0A6, Canada.

This study reveals the effect of TiB₂ particles on the mechanical and tribological properties of Fe₃Al-TiB₂ composite coatings against an alumina counterpart. The feedstock was produced by milling Fe₃Al and TiB₂ powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. Read More

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February 2016

Surface toughness of silicon nitride bioceramics: II, Comparison with commercial oxide materials.

J Mech Behav Biomed Mater 2016 Feb 12;54:346-59. Epub 2015 Sep 12.

Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8126 Kyoto, Japan. Electronic address:

Raman microprobe-assisted indentation, a micromechanics method validated in a companion paper, was used to compare the surface toughening behaviors of silicon nitride (Si3N4) and alumina-based bioceramics employed in joint arthroplasty (i.e., monolithic alumina, Al2O3, and yttria-stabilized zirconia (ZrO2)-toughened alumina, ZTA). Read More

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February 2016

Grinding efficiency of abutment tooth with both dentin and core composite resin on axial plane.

Bull Tokyo Dent Coll 2015 ;56(1):9-23

Department of Crown and Bridge Prosthodontics, Tokyo Dental College.

The purpose of this study was to evaluate grinding efficiency in abutment teeth comprising both dentin and core composite resin in the axial plane. Grinding was performed over 5 runs at two loads (0.5 or 0. Read More

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January 2017

Indentation size effect of Y-TZP dental ceramics.

Dent Mater 2014 Dec 31;30(12):e371-6. Epub 2014 Aug 31.

Department of materials, Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia.

Objective: The purpose of this study was to investigate and analyze the indentation size effect (ISE) in Vickers hardness of monolithic yttria partially stabilized zirconia (Y-TZP) dental ceramics without and with the addition of dental dye A3. The ISE is analyzed using the Mayer law, a proportional specimen resistance (PSR) model and a modified proportional specimen resistance (MPSR) model.

Methods: Two samples of Y-TZP dental ceramics, trade names BruxZir (provided by Glidewell Laboratories, CA, USA), were investigated. Read More

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December 2014

Effect of a common diet and regular beverage on enamel erosion in various temperatures: an in-vitro study.

J Dent (Tehran) 2013 Sep 30;10(5):411-6. Epub 2013 Sep 30.

Dentist, Private practice.

Objective: This study compared diet and regular Coca-Cola on enamel erosion in cold and room temperatures.

Materials And Methods: Seventy five enamel specimens were prepared and divided into 5 equal groups (N=15) as follows: Group 1: regular beverage at room temperature, Group 2: regular beverage at refri-gerator temperature, Group 3: diet beverage at room and Group 4: diet beverage at refrige-rator temperature. The specimens were immersed in the regular or diet beverage (Coca-Cola, trade mark regd. Read More

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September 2013

Chipping fracture resistance of denture tooth materials.

Dent Mater 2014 May 25;30(5):545-53. Epub 2014 Mar 25.

Paffenbarger Research Center, American Dental Association Foundation, Stop 854-6, NIST, Gaithersburg, MD 29899, USA.

Objective: The applicability of the edge chipping method to denture tooth materials was assessed. These are softer materials than those usually tested by edge chipping. The edge chipping fracture resistances of polymethylmethacrylate (PMMA) based and two filled resin composite denture tooth materials were compared. Read More

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Growth, optical, luminescence, thermal and mechanical behavior of an organic single crystal: 3-Acetyl-2-methyl-4-phenylquinolin-1-ium chloride.

Spectrochim Acta A Mol Biomol Spectrosc 2014 Apr 17;123:78-84. Epub 2013 Dec 17.

Centre for Organic and Medicinal Chemistry, VIT University, Vellore 632 014, India.

A single crystal of 3-acetyl-2-methyl-4-phenylquinolin-1-ium chloride has grown by slow evaporation solution growth technique using ethanol as solvent. The structural, thermal, optical and mechanical property has studied for the grown crystal. Single crystal XRD revealed that the crystal belongs to monoclinic system with space group P21/c. Read More

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An in vitro investigation of wear resistance and hardness of composite resins.

Int J Clin Exp Med 2013 26;6(6):423-30. Epub 2013 Jun 26.

School of Stomatology, Tongji University Shanghai 200072, China.

Purpose: The aim of the present study was to investigate the wear resistance and hardness of five kinds of composite resins.

Materials And Methods: Sixty-five specimens were fabricated with one nano-hybrid (Charisma Diamond), two micro-hybrid (3MZ250, Clearfil AP-X) and two packable (3MP60, Surefil) composite resins, according to a randomized complete block design (n=13, 8 for wear test; 5 for hardness test). The composites were filled in a rectangular mold, and light polymerization. Read More

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In-vitro strength degradation of dental ceramics and novel PICN material by sharp indentation.

J Mech Behav Biomed Mater 2013 Oct 15;26:34-42. Epub 2013 May 15.

Department of Oral Sciences, School of Dentistry, P.O. Box 647, Dunedin 9001, New Zealand.

Objectives: To determine the flexural strength and subsequent strength degradation of a range of dental CAD/CAM ceramic materials and novel PICN (Polymer-Infiltrated-Ceramic-Network) materials by means of pre-damaging with Vickers indentations at various loads.

Methods: The materials tested included (Mark II, PICN test material 1 and 2, In-Ceram Alumina, VM 9, In-Ceram YZ; Vita Zahnfabrik, Bad Saeckingen, Germany) and (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). Read More

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October 2013

Effect of loading conditions on the fracture toughness of zirconia.

J Prosthodont Res 2013 Apr 14;57(2):82-7. Epub 2013 Mar 14.

Department of Crown and Bridge, The Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan.

Purpose: A Vickers hardness indenter was pressed into yttria-stabilized zirconia (Y-TZP) by the indentation fracture method (IF method).

Methods: The effect on the calculated Vickers hardness, fracture toughness values, and indentation fracture load (9.8, 49, 98, 196, and 294 N) was examined to deduce the optimum conditions of the IF method. Read More

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Toward inexpensive superhard materials: tungsten tetraboride-based solid solutions.

J Am Chem Soc 2012 Dec 13;134(51):20660-8. Epub 2012 Dec 13.

Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, USA.

To enhance the hardness of tungsten tetraboride (WB(4)), a notable lower cost member of the late transition-metal borides, we have synthesized and characterized solid solutions of this material with tantalum (Ta), manganese (Mn), and chromium (Cr). Various concentrations of these transition-metal elements, ranging from 0.0 to 50. Read More

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December 2012

Reduced stiffness of alveolar bone in the colobine mandible.

Am J Phys Anthropol 2011 Mar 10;144(3):421-31. Epub 2010 Nov 10.

Department of Anthropology, University of Florida, Gainesville, FL 32611-7305, USA.

Alveolar bone has several mechanical functions, including tooth support and accommodation of occlusal and other masticatory forces. Its unique functional-mechanical environment is reflected by its structural characteristics, but whether alveolar bone is materially distinct from bone elsewhere in the primate facial skeleton is uncertain. This uncertainty is attributable not only to a limited amount of data but also to conflicting findings among these data. Read More

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Evaluation of microhardness, surface roughness, and wear behavior of different types of resin composites polymerized with two different light sources.

J Biomed Mater Res B Appl Biomater 2010 Feb;92(2):470-8

Department of Endodontics and Conservative Dentistry, Gulhane Military Medical Academy, Ankara, Turkey.

The microhardness, surface roughness and wear resistance of different types of resin composites, polymerized by a Quartz Tungsten Halogen (QTH) or Light Emitting Diode (LED) light curing units (LCU) were evaluated in this in vitro study. Cylindrical blocks were prepared from composites (8 mm in diameter, and 2 mm in thickness) and polymerized by a LED or a QTH LCU. Vickers hardness was measured on the top and bottom surfaces of the specimens. Read More

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February 2010

Micro-indentation fracture behavior of human enamel.

Dent Mater 2010 Jan;26(1):100-4

Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302735, Republic of Korea.

Objective: The purpose of this study was to determine the crack resistance behavior (K(R)) of human enamel in relation to its microstructure.

Methods: Human molar teeth were precision cut, polished and tested using Vickers micro-indentation at different loads ranging from 0.98 to 9. Read More

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January 2010

Carbon/silica composite fabricated from rice husk by means of binderless hot-pressing.

Bioresour Technol 2009 Jul 5;100(13):3308-15. Epub 2009 Mar 5.

Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, Yurihonjo, Akita, Japan.

A carbon/silica composite designed for use under compressive loads was fabricated from rice husk (RH), an agricultural waste material. RH was pulverized by using a planetary ball mill, then carbonized and molded into the precursor by means of hot-pressing without using any binders. A compression of 100 MPa was intermittently applied to the RH powder heated from room temperature to 150 degrees C, and then to 280 degrees C. Read More

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Cytoskeletal alterations differentiate presenilin-1 and sporadic Alzheimer's disease.

Acta Neuropathol 2009 Jan 18;117(1):19-29. Epub 2008 Nov 18.

Wicking Dementia Research and Education Centre and NeuroRepair Group, Menzies Research Institute, Private Bag 29, Hobart, TAS, 7001, Australia.

Most cases of Alzheimer's disease (AD) are sporadic in nature, although rarer familial AD (FAD) cases have provided important insights into major pathological disease mechanisms. Mutations in the presenilin 1 gene (PS1) are responsible for the majority of FAD cases, causing an earlier age of onset and more rapid progression to end-stage disease than seen in sporadic AD. We have investigated the cytoskeletal alterations in neuritic AD pathology in a cohort of FAD cases in comparison to sporadic AD and pathologically aged cases. Read More

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January 2009

Evolution of residual stress and crack morphologies during 3D FIB tomographic analysis of alumina.

J Microsc 2008 May;230(Pt 2):240-51

Department of Engineering Materials, The University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom.

Three-dimensional focused ion beam (FIB) tomography is increasingly being used for 3D characterization of microstructures in the 50 nm-20 microm range. FIB tomography is a destructive, invasive process, and microstructural changes may potentially occur during the analysis process. Here residual stress and crack morphologies in single-crystal sapphire samples have been concurrently analyzed using Cr3+ fluorescence spectroscopy and FIB tomography. Read More

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Flexural strength, fatigue life, and stress-induced phase transformation study of Y-TZP dental ceramic.

J Biomed Mater Res B Appl Biomater 2009 Feb;88(2):366-77

Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, London, United Kingdom.

Objectives: Yttria partially-stabilized zirconia polycrystalline (Y-TZP) has been the subject of extensive research because of its high strength and toughness. The aim of this study was to evaluate the biaxial flexural strength, fatigue life, and to investigate in more detail on single cycle specimens, the pressure-induced phase transformation of a Y-TZP dental ceramic using Raman microspectroscopy.

Materials And Methods: Thirty standardized discs (15 x 1. Read More

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February 2009

A unified framework of immunological and epidemiological dynamics for the spread of viral infections in a simple network-based population.

Theor Biol Med Model 2007 Dec 20;4:49. Epub 2007 Dec 20.

Interdisciplinary Studies, College of Graduate Studies and Research, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

Background: The desire to better understand the immuno-biology of infectious diseases as a broader ecological system has motivated the explicit representation of epidemiological processes as a function of immune system dynamics. While several recent and innovative contributions have explored unified models across cellular and organismal domains, and appear well-suited to describing particular aspects of intracellular pathogen infections, these existing immuno-epidemiological models lack representation of certain cellular components and immunological processes needed to adequately characterize the dynamics of some important epidemiological contexts. Here, we complement existing models by presenting an alternate framework of anti-viral immune responses within individual hosts and infection spread across a simple network-based population. Read More

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December 2007

Reduced levels of Ago2 expression result in increased siRNA competition in mammalian cells.

Nucleic Acids Res 2007 28;35(19):6598-610. Epub 2007 Sep 28.

Isis Pharmaceuticals. 1896 Rutherford Road, Carlsbad, CA 92008, USA.

Administration of small interfering RNAs (siRNAs) leads to degradation of specific mRNAs utilizing the cellular RNA interference (RNAi) machinery. It has been demonstrated that co-administration of siRNAs may lead to attenuation of activity of one of the siRNAs. Utilizing antisense and siRNA-mediated RNA-induced silencing complex (RISC) gene reduction we show that siRNA competition is correlated with differences in the cellular expression levels of Ago2, while levels of other RISC proteins have no effect on competition. Read More

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December 2007

The effect of tissue condition and applied load on Vickers hardness of human trabecular bone.

J Biomech 2007 27;40(14):3267-70. Epub 2007 Jun 27.

Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Via di Barbiano, 1/10, 40136 Bologna, Italy.

Hardness of trabecular human bone, evaluated by microindentation testing, has generally been measured on embedded tissues. It was known that this was not ideal but it had been preferred to other conditions (e.g. Read More

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December 2007

Annealing study of palladium-silver dental alloys: Vickers hardness measurements and SEM microstructural observations.

J Mater Sci Mater Med 2007 Jan;18(1):111-8

Section of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, PO Box 182357, Columbus, OH 43218-2357, USA.

Three Pd-Ag dental alloys for metal-ceramic restorations, W-1 (Ivoclar Vivadent), Rx 91 (Pentron) and Super Star (Heraeus Kulzer), were subjected to isothermal annealing for 0.5 hr periods in a nitrogen atmosphere at temperatures from approximately 400 degrees to 950 degrees C. The annealing behavior was investigated by Vickers hardness measurements (1 kg load) and SEM microstructural observations. Read More

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January 2007

Hardness measured with traditional Vickers and Martens hardness methods.

Dent Mater 2007 Sep 4;23(9):1079-85. Epub 2006 Dec 4.

Department of Restorative Dentistry, School of Dental Sciences, University of Newcastle upon Tyne, UK.

Objective: To determine the differences, if any, between hardness measured with traditional Vickers and Martens hardness test methods on denture teeth under 2, 10 and 50 N loads.

Method: Hardness of acrylic resin (VIV), composite resin (ORT) and porcelain (POR) denture tooth materials was measured using a traditional Vickers hardness (HV) method and Martens hardness (HM) method at 2, 10 and 50N test loads. Vickers hardness was also calculated from the force-indentation depth curves (HVfid) that were recorded during Martens hardness. Read More

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September 2007

High-temperature tribological characterization of commercial TiAlN coatings.

J Phys Condens Matter 2006 Aug 25;18(32):S1727-36. Epub 2006 Jul 25.

School of Metallurgy and Materials Science, Central University of Venezuela, Caracas, Venezuela.

This study was performed with the aim of evaluating the relative tribological behaviour at high temperature of (Ti(1-x)Al(x))N coatings commercially deposited on WC inserts. The (Ti(1-x)Al(x))N multilayered, nanostructured and single-layer coatings, which contained different Ti/Al atomic ratios varying from 7/3 to 2/3 respectively, were deposited by employing a commercial PVD cathodic arc process. The absolute hardness value for each coating is also reported and has been calculated from the Vickers microhardness measurements by using one of the models published in the literature. Read More

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