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Cyclic Fatigue

Shriya S Srinivasan, Benjamin E Maimon, Maurizio Diaz, Hyungeun Song, Hugh M Herr
Optogenetics has been used to orchestrate temporal- and tissue-specific control of neural tissues and offers a wealth of unique advantages for neuromuscular control. Here, we establish a closed-loop functional optogenetic stimulation (CL-FOS) system to control ankle joint position in murine models. Using the measurement of either joint angle or fascicle length as a feedback signal, we compare the controllability of CL-FOS to closed-loop functional electrical stimulation (CL-FES) and demonstrate significantly greater accuracy, lower rise times and lower overshoot percentages...
December 13, 2018: Nature Communications
Paulo Jorge Palma, Ana Messias, António Rosa Cerqueira, Luís Diogo Tavares, Francisco Caramelo, Luís Roseiro, João Miguel Santos
To evaluate the effect of immersion in 3% sodium hypochlorite solution in the resistance to cyclic fatigue of three nickel-titanium (NiTi) rotary file systems, ProTaper Next (PTN), Hyflex CM (CM), and Hyflex EDM (EDM), in a mechanical model featuring axial movement. Ninety instruments of three different NiTi rotary file systems, PTN (size 25, 0.06 taper), CM (25, 0.06), and EDM (25/~, variable taper), were randomly divided according to a 3 × 3 factorial design and tested under dynamic immersion in a 3% NaOCl solution (1 or 5 min) or without immersion, making a total of 9 groups (n = 10)...
December 12, 2018: Odontology
T Y Qiu, L G Zhao, M Song
PURPOSE: The study compared the mechanical behavior of bioresorbable polymeric stents with various designs during deployment, and investigated their fatigue performance under pulsatile blood pressure loading. METHODS: Finite element simulations have been carried out to compare the mechanical performance of four bioresorbable polymeric stents, i.e., Absorb, Elixir, Igaki-Tamai and RevaMedical, during deployment in diseased artery. Tri-folded balloon was modelled to expand the crimped stent onto the three-layered arterial wall with plaque...
December 10, 2018: Cardiovascular Engineering and Technology
Camila Pauleski Zucuni, Andressa Borin Venturini, Catina Prochnow, Gabriel Kalil Rocha Pereira, Luiz Felipe Valandro
This study evaluated the fatigue failure load, number of cycles for failure and survival probability of 2nd and 3rd generation yttrium-stabilized zirconia (YSZ) adhesively cemented to a dentin analogue substrate. Disc-shaped specimens (n = 10; Ø = 10 mm; thickness = 1.0 mm) were produced from four 2nd generation YSZs (Lava Plus, 3M ESPE; Vita In-Ceram YZ-HT, VITA Zahnfabrik; Zirlux FC, Ivoclar Vivadent; Katana ML-HT, Kuraray) and two 3rd generation YSZs (Katana UTML and Katana STML, Kuraray)...
November 12, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Danny Omar Mendoza Marin, Andressa Rosa Perin Leite, Norberto Martins de Oliveira Junior, André Gustavo Paleari, Ana Carolina Pero, Marco Antonio Compagnoni
Several attachment systems for mandibular implant-supported overdentures are currently available and studies are required to understand their mechanical properties. The objective of this study was to evaluate the retention force and wear characteristics of three attachment systems in a simulation of the cyclic dislodging of implant-supported overdentures. Thirty samples were fabricated and divided into 3 groups: 1-O-ring; 2-Mini Ball; and 3-Equator. A mechanical fatigue test was applied to the specimens using a servo-hydraulic universal testing machine performing 5500 insertion/removal cycles (f=0...
November 2018: Brazilian Dental Journal
F E Figueiredo, R C Santos, A S Silva, A D Valdívia, L A Oliveira-Neto, S Griza, C J Soares, A L Faria-E-Silva
OBJECTIVES: To investigate the survival and failure mode of fiber-post resin restorations over preparations with different ferrule designs when submitted to a fatigue load test. METHODS AND MATERIALS: Fifty bovine incisors were selected and divided into five groups (n=10) according to ferrule design: a no-ferrule group, a 2-mm circumferential ferrule group, a 2-mm buccal ferrule group, a 2-mm lingual ferrule group, and a 2-mm buccal and lingual ferrule group. The fiberglass post was cemented and the composite core was built up and prepared, followed by cementation of a full composite crown...
October 10, 2018: Operative Dentistry
Chao He, Yujuan Wu, Liming Peng, Ning Su, Xue Li, Kun Yang, Yongjie Liu, Shucheng Yuan, Renhui Tian
Cyclic deformation at low-stress amplitudes of a rare earth-containing magnesium alloy (Mg⁻Gd⁻Y⁻Zr) was investigated with emphasis on the responsible microstructural relationship between deformation mechanism and fatigue crack initiation. The results show that the microstructural deformation is extremely inhomogeneous at the low-stress amplitudes. Both deformation twinning and non-basal slip are barely observed, and basal slip is the predominant deformation to accommodate micro-plasticity. Fatigue crack initiation occurred at the basal slip bands, causing the morphology of facet on the fracture surface...
November 30, 2018: Materials
Baris Kumru, Valerio Molinari, Reinhild Dünnebacke, Kerstin G Blank, Bernhard V K J Schmidt
Extremely compressible hydrogels are fabricated in one pot via sulfonic-acid-modified graphitic carbon nitride (g-CN-AHPA) as a visible light photoinitiator and reinforcer. The hydrogels show unusual compressibility upon applied stress up to 12 MPa, presenting temporary physical deformation, and remain undamaged after stress removal despite their high water content (90 wt%). Cyclic compressibility proves the fatigue resistance of the covalently and electrostatically reinforced system that possesses tissue adhesive properties, shock resistance, cut resistance, and little to no toxicity...
November 30, 2018: Macromolecular Rapid Communications
Yidong Gan, Hongzhi Zhang, Branko Šavija, Erik Schlangen, Klaas van Breugel
Cement paste is the main binding component in concrete and thus its fundamental properties are of great significance for understanding the fracture behaviour as well as the ageing process of concrete. One major aim of this paper is to characterize the micromechanical properties of cement paste with the aid of a nanoindenter. Besides, this paper also presents a preliminary study on the fatigue behaviour of cement paste at the micrometer level. Miniaturized cantilever beams made of cement paste with different water/cement ratios were statically and cyclically loaded...
November 28, 2018: Micromachines
Eugenio Pedullà, Giusy Rita Maria La Rosa, Simona Boninelli, Oriana Gaetana Rinaldi, Ernestro Rapisarda, Hyeon-Cheol Kim
INTRODUCTION: The purpose of this study was to compare the cyclic fatigue of Reciproc (REC; VDW, Munich, Germany) and Reciproc blue (REB, VDW) with different angles of file access. METHODS: The cyclic fatigue resistance of 120 new REC R25 and REB R25 (REB) files was tested. Instruments were divided into 8 groups on the basis of the access angle inside the artificial canal tested (n = 15): groups 1, 2, 3, and 4 included REC tested at 0°, 10°, 20°, and 30°, respectively, and groups 5, 6, 7, and 8 consisted of REB tested at 0°, 10°, 20°, and 30°, respectively...
December 2018: Journal of Endodontics
Simone Staffoli, Nicola Maria Grande, Gianluca Plotino, Taha Özyürek, Mustafa Gündoğar, Leonzio Fortunato, Antonella Polimeni
The aim of the present study was to evaluate the effect of environmental temperature, heat-treatment*** and design on the cyclic fatigue resistance of OneShape (OS), OneShape new generation (OSNG) and One Curve (OC) NiTi rotary single-file instruments. Cyclic fatigue testing of NiTi instruments was performed in an artificial canal with a 5-mm radius of curvature and a 60° angle of curvature located 5 mm from the tip of the instrument. During the experiment 3 different temperatures were used in a thermostatic bath with electronic and infrared controls: 0°, 20° and 35 °C...
November 27, 2018: Odontology
Adham A Azim, Mohamed Tarrosh, Katharina A Azim, Lucila Piasecki
INTRODUCTION: The aim of this study was to compare the cyclic fatigue resistance of XP Shaper (XP), HyFlex EDM One File (EDM), and WaveOne Gold Primary (WOG) when operated according to their manufacturers' recommendations at different lengths and to investigate the cyclic fatigue limit of XP Shaper when operated at 3000 rpm. METHODS: One hundred fifty instruments from 4 different rotary systems (F2 Protaper Universal [PTU], WOG, EDM, and XP) were tested for their cyclic fatigue resistance in a simulated 90° curved canal at a 37°C water bath temperature at 3 different working lengths (15 mm, 17 mm, and 19 mm)...
December 2018: Journal of Endodontics
Noah Bonnheim, Farzana Ansari, Marco Regis, Pierangiola Bracco, Lisa Pruitt
Carbon-fiber reinforced (CFR) PEEK implants are used in orthopedic applications ranging from fracture fixation plates to spinal fusion cages. Documented implant failures and increasing volume and variety of CFR PEEK implants warrant a clearer understanding of material behavior under monotonic and cyclic loading. To address this issue, we conducted monotonic and fatigue crack propagation (FCP) experiments on orthopedic grade unfilled PEEK and two formulations of CFR PEEK (PAN- and pitch-based carbon fibers)...
November 3, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Tianyong Jiang, Yaowen Zhang, Lei Wang, Liang Zhang, Gangbing Song
Modular bridge expansion joints (MBEJs) are commonly used in bridges and are often subjected to fatigue damages, which necessitate fatigue monitoring of MBEJs to ensure the reliable operation of the bridges. In this paper, a stress wave based active sensing approach using piezoceramic transducers is developed to monitor the fatigue damage of MBEJ. A MBEJ involves mainly center beam, edge beam, support bar, support box, sliding bearing, sliding spring, elastomeric strip seal, full-penetration weld and reinforcing plate...
November 15, 2018: Sensors
Kuang-Ta Yao, Hung-Chan Kao, Cheng-Kung Cheng, Hsu-Wei Fang, Chang-Hung Huang, Ming-Lun Hsu
OBJECTIVES: Conical implant-abutment connections are popular for its anti-bending performance; on the other hand, the torsional and axial forces also play important roles in occlusion. However, so far there were scarce studies on their effects on connection stability. Therefore, this study seeks to investigate the mechanical performance of conical connections under different cyclic loading conditions. METHODS: 15 conical implant-abutment assembles (Cowell Medi, Busan, South Korea) were divided into 3 groups according to different cyclic loadings...
November 1, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Mateusz Radwański, Michał Łęski, Halina Pawlicka
BACKGROUND: The nickel-titanium alloy used in the production of nickel-titanium files contains approx. 56% nickel and 44% titanium by weight. To improve the properties of nickel-titanium files, the manufacturers introduce some innovations in the production process. Their purpose is primarily to decrease the stiffness of the instruments while increasing the resistance to cyclic fatigue, which reduces the risk of file separation. One of the most popular processes is the heat treatment of the nickel-titanium alloy...
November 13, 2018: Dental and medical problems
Mehmet Adiguzel, Ipek Isken, Ismail Ilker Pamukcu
Background. The aim of this study was to compare the cyclic fatigue resistance of XP-endo Shaper, HyFlex CM, FlexMaster and Race rotary instruments at body temperature (37±1°C). Methods. Twenty XP-endo Shaper (#30/.01), 20 HyFlex CM (#30/.04), 20 FlexMaster (#30/.04) and 20 Race (#30/.04) instruments were tested at body temperature (n=20). The instruments were evaluated in artificial canals with a 3-mm radius of curvature and 60° angle of curvature to the center of the 1.5-mm-wide canal. Each instrument was rotated until fracture occurred and the number of cycles to failure (NCF) recorded...
2018: Journal of Dental Research, Dental Clinics, Dental Prospects
Lilan Gao, Dongdong Liu, Hong Gao, Linwei Lv, Chunqiu Zhang
Since the accumulations of ratcheting strain combined with creep deformation, which are produced in normal activities, can accelerate the fatigue damage of cartilage in joint, the creep-ratcheting and creep-recovery-ratcheting behaviors of articular cartilage are experimentally investigated under creep-fatigue loads. The effect of pre-creep on ratcheting behavior of cartilage was probed firstly and it is found that the initial ratcheting strain of cartilage presents the larger value (30% and 35%) due to its pre-creep deformation in spite of the short pre-creep time applied...
January 1, 2019: Materials Science & Engineering. C, Materials for Biological Applications
Eli K Cehelyk, Denise Y Harvey, Meghan L Grubb, Rasha Jalel, Mohammad S El-Sibai, Clyde E Markowitz, Joseph R Berger, Roy H Hamilton, Salim Chahin
BACKGROUND: Fatigue and cognitive dysfunction are two common symptoms experienced by patients with multiple sclerosis (MS). The relationship between subjective and objective fatigue (fatigability) in MS is poorly understood. Cognitive control tasks might be more conducive to fatigability and more likely to show associations between subjective and objective cognitive fatigue in MS. OBJECTIVE: To study the association between objective fatigability, as induced by a cognitive control task called the Blocked Cyclic Naming Task (BCNT), subjective fatigue and baseline cognitive functioning in patients with MS...
October 27, 2018: Multiple Sclerosis and related Disorders
S Y Yang, Y X Zeng, H Cai, M Zhang, Y J Chen, J Wang
Objective: To evaluate the influence of fracture resistance of endodontically treated teeth with different thickness of ferrule by mechanical fatigue test and static loading test, and so as to provide a reference for the clinical treatment planning. Methods: Fifty bovine incisors were divided into 5 groups by random number table method ( n =10). Group A was the control group in which the incisors were prepared without a ferrule design (0 mm). The other four groups (B, C, D, E) were experimental groups, and the thickness of the dentin ferrule prepared for specimens in each group was 0...
November 9, 2018: Zhonghua Kou Qiang Yi Xue za Zhi, Zhonghua Kouqiang Yixue Zazhi, Chinese Journal of Stomatology
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