scholarly journals Elemental, microstructural, and mechanical characterization of high gold orthodontic brackets after intraoral aging

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Sepp Hersche ◽  
Iosif Sifakakis ◽  
Spiros Zinelis ◽  
Theodore Eliades
Keyword(s):  
Mechanical Properties ◽  
Elemental Composition ◽  
Orthodontic Brackets ◽  
Control Group ◽  
Indentation Modulus ◽  
Backscattered Electron ◽  
Lingual Brackets ◽  
Electron Imaging ◽  
Martens Hardness

AbstractThe purpose of the present study was to investigate the elemental composition, the microstructure, and the selected mechanical properties of high gold orthodontic brackets after intraoral aging. Thirty Incognito™ (3M Unitek, Bad Essen, Germany) lingual brackets were studied, 15 brackets as received (control group) and 15 brackets retrieved from different patients after orthodontic treatment. The surface of the wing area was examined by scanning electron microscopy (SEM). Backscattered electron imaging (BEI) was performed, and the elemental composition was determined by X-ray EDS analysis (EDX). After appropriate metallographic preparation, the mechanical properties tested were Martens hardness (HM), indentation modulus (E

scholarly journals Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

2019 ◽  
Vol 29 (3) ◽  
pp. 1787-1800 ◽  
Author(s):  
Yihuai Zhang ◽  
Maxim Lebedev ◽  
Gregory Smith ◽  
Yu Jing ◽  
Andreas Busch ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Vitrinite Reflectance ◽  
Chemical Properties ◽  
Coal Bed ◽  
Coal Bed Methane ◽  
Indentation Modulus ◽  
Micro Computed Tomography ◽  
Micro Structure ◽  
Nano Indentation

ABSTRACT Characterization of coal micro-structure and the associated rock mechanical properties are of key importance for coal seam exploration, coal bed methane development, enhanced coal bed methane production and CO2 storage in deep coal seams. Considerable knowledge exists about coal chemical properties, but less is known about the nanoscale to the micro-scale structure of coals and how they change with coal strength across coal ranks. Thus, in this study, 3D X-ray micro-computed tomography (with a voxel size of 3.43 µm) and nano-indentation tests were conducted on coal samples of different ranks from peat to anthracite. The micro-structure of peats showed a well-developed pore system with meso- and micro-pores. The meso-pores essentially disappear with increasing rank, whereas the micro-pores persist and then increase past the bituminous rank. The micro-fracture system develops past the peat stage and by sub-bituminous ranks and changes into larger and mature fracture systems at higher ranks. The nano-indentation modulus showed the increasing trend from low- to high-rank coal with a perfect linear relationship with vitrinite reflectance and is highly correlated with carbon content as expected.

Study of the Mechanical Properties and Toughening Mechanism of Nano-NbC Particles Toughened Si3N4-Based Ceramics

2020 ◽  
Vol 20 (3) ◽  
pp. 1709-1714
Author(s):  
Liang Tian ◽  
Qinglin Hou ◽  
Yingxia Wang ◽  
Yihui Hou ◽  
Li Li
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Injection Moulding ◽  
Sintering Temperature ◽  
Toughening Mechanism ◽  
Comprehensive Properties ◽  
Backscattered Electron ◽  
Grain Distribution ◽  
Electron Imaging

In this article, nano-NbC particles toughened Si3N4-based ceramics were prepared by injection moulding and their mechanical properties along with toughening mechanism were studied. An increase of nano-NbC content, gradually homogenizes microstructure of the Si3N4-based ceramics along with increase in its density. However, the fracture toughness and flexural strength first increases and then decreases. The Si3N4-based ceramics demonstrate good comprehensive properties at the 15 wt% nano-NbC content and sintering temperature of 1550 °C (where the density is 85.3%, the flexural strength is 845 MPa, and the fracture toughness is 9.3 MPa·m1/2), Backscattered electron imaging shows that nano-NbC particles can be well dispersed in the Si3N4 ceramic matrix by injection moulding and ceramics are toughened by crack deflection and microcracking effects. It was also found that increasing sintering temperature makes the β-Si3N4 grain distribution more uniform by reducing the porosity.

scholarly journals Changes in Roughness and Mechanical Properties of Invisalign® Appliances after One- and Two-Weeks Use

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2406 ◽  
Author(s):  
Alexandra K. Papadopoulou ◽  
Aurelie Cantele ◽  
Georgios Polychronis ◽  
Spiros Zinelis ◽  
Theodore Eliades
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Detrimental Effect ◽  
Internal Surface ◽  
Acrylic Resin ◽  
Indentation Modulus ◽  
Instrumented Indentation ◽  
Post Hoc ◽  
Relaxation Index ◽  
Martens Hardness

The aim of this study was to estimate the possible changes of surface roughness and the mechanical properties of Invisalign® appliances over one- and two-week of service. Forty appliances with attachments were retrieved after the end of orthodontic treatment from different patients. Half of them had been used for one week (1W), and the rest for two weeks (2W). Ten unused Invisalign® appliances were used as the control (CON). An equal number of teeth possessing attachments were cut of aligners deriving from all groups (1W, 2W, and CON), and the Sa, Sq, Sz, Sc, and Sv roughness parameters of the internal surface of the aligner attachment area and the opposite lingual side (which was in contact to enamel) were determined by optical profilometry. Then, ten first molars originating from all groups were embedded in acrylic resin, and were ground and polished. Instrumented indentation testing (IIT) was performed in order to determine the Martens hardness (HM), indentation modulus (EIT), and relaxation index (RIT), according to ISO 14577-2002. The produced data were statistically processed by one- or two-way analysis of variance (ANOVA) and multiple comparison post-hoc tests (a = 0.05). Both the surface roughness and mechanical properties of the retrieved groups (1W and 2W) showed statistically significant differences compared with CON, but without statistically significant differences between each other. The roughness variables of the as-received material were shown to be reduced after intraoral service demonstrating a wear effect. Ageing has a detrimental effect on the surface roughness and mechanical properties of Invisalign® appliances, although this effect is restricted to the first week of clinical usage.

scholarly journals A Comparison of the Compositional, Microstructural, and Mechanical Characteristics of Ni-Free and Conventional Stainless Steel Orthodontic Wires

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3424
Author(s):  
Daniela Brüngger ◽  
Theodoros Koutsoukis ◽  
Youssef S. Al Jabbari ◽  
Monika Hersberger-Zurfluh ◽  
Spiros Zinelis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Elemental Composition ◽  
Indentation Modulus ◽  
Limited Information ◽  
X Ray Diffraction ◽  
Orthodontic Wires ◽  
Promising Alternative ◽  
X Ray ◽  
Oriented Parallel

Ni-free orthodontic wires were introduced to mitigate concerns associated with the use of Ni-containing alloys in orthodontics. However, limited information is available on their properties and therefore, the aim of this study was to characterize the elemental composition, the microstructure, and the mechanical properties of Ni-free orthodontic wires and compare them with their stainless steel (SS) counterparts. Four Ni-free and four conventional SS wires were included in this study. All the wires were initially imaged with a Scanning Electron Microscopy (SEM) and their elemental compositions were determined by X-ray Energy Dispersive Spectroscopy (EDX). Then, their microstructure was assessed by X-ray Diffraction (XRD) and the indentation modulus, elastic index, Martens Hardness and Vickers Hardness by Instrumented Indentation Testing (IIT). All the wires demonstrated surface cracks and pores oriented parallel to their long axis. The elemental composition of Ni-free alloys showed an increased Mn and Cr content while both SS and Ni-free wires shared the same dominant austenite structure. In conclusion, despite the differences in elemental composition, Ni-free wires demonstrated a similar microstructure and comparable mechanical properties with their conventional SS counterparts and thus may be considered as a promising alternative for patients with Ni supersensitivity.

scholarly journals Mapping of the Micro-Mechanical Properties of Human Root Dentin by Means of Microindentation

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 505
Author(s):  
Michael Kucher ◽  
Martin Dannemann ◽  
Niels Modler ◽  
Martina Romy Bernhard ◽  
Christian Hannig ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Indentation Creep ◽  
Indentation Hardness ◽  
Indentation Modulus ◽  
Microstructural Alterations ◽  
Starting Point ◽  
Human Dentin ◽  
Root Dentin ◽  
Cervical Root ◽  
Martens Hardness

The extensive knowledge of root dentin’s mechanical properties is necessary for the prediction of microstructural alterations and the teeth’s deformations as well as their fracture behavior. Standardized microindentation tests were applied to apical, medial, and cervical root sections of a mandibular human first molar to determine the spatial distribution of the hard tissue’s properties (indentation modulus, indentation hardness, Martens hardness, indentation creep). Using an indentation mapping approach, the inhomogeneity of mechanical properties in longitudinal as well as in transversal directions were measured. As a result, the tooth showed strongly inhomogeneous material properties, which depended on the longitudinal and transversal positions. In the transversal cutting planes of the cervical, medial, apical sections, the properties showed a comparable distribution. A statistical evaluation revealed an indentation modulus between 12.2 GPa and 17.8 GPa, indentation hardness between 0.4 GPa and 0.64 GPa and an indentation creep between 8.6% and 10.7%. The established standardized method is a starting point for further investigations concerning the intensive description of the inhomogeneous mechanical properties of human dentin and other types of dentin.

Relating Local Bone Stiffness and Calcium Content by Combined Nanoindentation and Backscattered Electron Imaging

2005 ◽  
Vol 874 ◽  
Author(s):  
M. Weber ◽  
T. Schoeberl ◽  
P. Roschger ◽  
K. Klaushofer ◽  
P. Fratzl
Keyword(s):  
Mechanical Properties ◽  
Hierarchical Structures ◽  
Calcium Content ◽  
Collagen Matrix ◽  
Bone Diseases ◽  
Backscattered Electron Imaging ◽  
Biomechanical Models ◽  
Local Bone ◽  
Backscattered Electron ◽  
Electron Imaging

AbstractBone is a hierarchically structured mineral-organic composite material that has to bear static and dynamic mechanical loads applied by body weight and locomotion. Bone mechanical properties are influenced by a number of factors, depending on the particular hierarchical levels. The high stiffness of bone material is mainly achieved by reinforcement with calcium phosphate mineral platelets. A model for this elementary structure level consists of an arrangement of staggered mineral bricks, embedded in collagen matrix, which provides both stiffness and toughness. The mechanical properties depend on the amount, shape and arrangement of the mineral particles but also on the properties of the collagen-rich matrix.One of the difficulties in assessing the properties of hierarchical structures is the inherent inhomogeneity of the tissue: Parameters such as stiffness or calcium content vary throughout a bone section. Such type of investigations becomes more meaningful by a combination of two complementary methods e.g. quantitative backscattered electron imaging (qBEI) and nanoindentation. The local Ca-content, representing the degree of the mineralization, is extracted from the qBEI measurements, whereas the local mechanical properties, elastic modulus and hardness, are measured by nanoindentation, a miniaturized hardness testing using a small diamond tip. The measured correlations between local Ca-content and mechanical strength help, for example, to verify biomechanical models based on the nanocomposite structure of bone. They may also shed new light on bone diseases such as osteoporosis or osteogenesis imperfecta.

scholarly journals The Influence of the Third Element on Nano-Mechanical Properties of Iron Borides FeB and Fe2B Formed in Fe-B-X (X = C, Cr, Mn, V, W, Mn + V) Alloys

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4155
Author(s):  
Ivana Kirkovska ◽  
Viera Homolová ◽  
Ivan Petryshynets ◽  
Tamás Csanádi
Keyword(s):  
Mechanical Properties ◽  
Indentation Size Effect ◽  
Microstructural Characterization ◽  
Indentation Hardness ◽  
Indentation Modulus ◽  
Instrumented Indentation ◽  
X Ray Diffraction ◽  
Alloying Element ◽  
X Ray

In this study, the influence of alloying elements on the mechanical properties of iron borides FeB and Fe2B formed in Fe-B-X (X = C, Cr, Mn, V, W, Mn + V) alloys were evaluated using instrumented indentation measurement. The microstructural characterization of the alloys was performed by means of X-ray diffraction and scanning electron microscope equipped with an energy dispersive X-ray analyzer. The fraction of the phases present in the alloys was determined either by the lever rule or by image analysis. The hardest and stiffest FeB formed in Fe-B-X (X = C, Cr, Mn) alloys was observed in the Fe-B-Cr alloys, where indentation hardness of HIT = 26.9 ± 1.4 GPa and indentation modulus of EIT = 486 ± 22 GPa were determined. The highest hardness of Fe2B was determined in the presence of tungsten as an alloying element, HIT = 20.8 ± 0.9 GPa. The lowest indentation hardness is measured in manganese alloyed FeB and Fe2B. In both FeB and Fe2B, an indentation size effect was observed, showing a decrease of hardness with increasing indentation depth.

scholarly journals Mechanical properties of contemporary orthodontic adhesives used for lingual fixed retention

2017 ◽  
Vol 62 (3) ◽  
Author(s):  
Iosif Sifakakis ◽  
Spiros Zinelis ◽  
Raphael Patcas ◽  
Theodore Eliades
Keyword(s):  
Mechanical Properties ◽  
Clinical Performance ◽  
Indentation Modulus ◽  
Orthodontic Adhesives ◽  
Fixed Retainers ◽  
Martens Hardness ◽  
Fixed Retention

AbstractObjective:The aim of the present study was to test the mechanical properties of different adhesives used in orthodontics for fixed retainers and to investigate their possible interrelations.Materials and methods:Specimens of six different adhesive resins were prepared: Transbond XT, Transbond LR and an experimental BPA-free orthodontic adhesive, as well as IPS Empress Direct (IPS-ED), ZNano and Accolade. The mechanical properties tested were Martens hardness (HM), indentation modulus (EResults:Significant differences were identified among all the materials tested for HM, with Transbond LR presenting the highest value. This resin presented the highest EConclusions:The materials tested demonstrated significant differences in their mechanical properties, and thus differences in their clinical performance are anticipated.

Mechanical modulation at the lamellar level in osteonal bone

2006 ◽  
Vol 21 (8) ◽  
pp. 1913-1921 ◽  
Author(s):  
H.S. Gupta ◽  
U. Stachewicz ◽  
W. Wagermaier ◽  
P. Roschger ◽  
H.D. Wagner ◽  
...  
Keyword(s):  
Periodic Variation ◽  
Tissue Level ◽  
Indentation Modulus ◽  
Backscattered Electron Imaging ◽  
Modulated Structure ◽  
Quantitative Backscattered Electron Imaging ◽  
Fundamental Building Block ◽  
Backscattered Electron ◽  
Mechanical Modulation ◽  
Electron Imaging

The secondary osteon is the fundamental building block of compact cortical bone at the tissue level. Light and scanning electron microscopy have shown that the osteon consists of a laminated cylindrical composite of mineralized collagen fibril lamellae ∼5–7 μm thick. Using scanning nanoindentation and quantitative backscattered electron imaging on secondary osteons from the human femoral midshaft, we found that the indentation modulus shows a periodic variation between ∼24 GPa and ∼27 GPa within a single lamella. The average lamellar value remains nearly constant across the osteon and increases abruptly to more than 30 GPa at the interstitial bone interface. The local mineral content, determined from quantitative backscattered electron imaging at the indented locations, shows also a lamellar level modulation and is positively correlated with the indentation modulus at the same tissue position. We propose that such a mechanically and compositionally modulated structure may be an effective crack-stopping mechanism in bone.

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