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Cyclic Fatigue

Catina Prochnow, Gabriel Kalil Rocha Pereira, Andressa Borin Venturini, Maitê Munhoz Scherer, Marília Pivetta Rippe, Marco Cícero Bottino, Cornelis Johannes Kleverlaan, Luiz Felipe Valandro
This study investigated the effect of etching with distinct hydrofluoric (HF) acid concentrations on the cyclic load-to-failure (CLf ) of simplified lithium disilicate glass-ceramic restorations adhesively cemented to a dentin analogue (n = 20): non-etched/control (CTRL), or etched for 20 s with HF acid at 3% (HF3), 5% (HF5), or 10% (HF10). A silane coating was then applied onto the ceramic surfaces. Fatigue tests followed the staircase approach (initial load= 720 N; step-size= 70 N; 500,000 cycles per sample; 20 Hz) using a hemispheric stainless-steel piston (Ø= 40 mm) under water...
July 30, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Farhad Javid, Nastaran Shahmansouri, Jorge Angeles, Rosaire Mongrain
Sudden failure and rupture of the tissue is a rare but serious short-term complication after the mitral valve surgical repair. Excessive cyclic loading on the suture line of the repair can progressively damage the surrounding tissue and finally cause tissue rupture. Moreover, mechanical over-tension, which occurs in a diseased mitral valve, gradually leads to tissue floppiness, mitral annular dilation, and leaflet rupture. In this work, the rupture mechanics of mitral valve is studied by characterizing the fracture toughness exhaustion of healthy tissue...
August 10, 2018: Biomechanics and Modeling in Mechanobiology
Brendan R Vahey, Mariane B Sordi, Kyle Stanley, Ricardo S Magini, Antonio P Novaes de Oliveira, Márcio C Fredel, Bruno Henriques, Júlio C M Souza
STATEMENT OF PROBLEM: The improved esthetics of ceramic dental prostheses has increased their popularity, although their high elastic modulus and low fracture toughness and tensile strength may reduce the long-term performance of dental prostheses. PURPOSE: The purpose of this in vitro study was to assess the mechanical integrity of zirconium-lithium silicate glass-ceramic crowns cement- and screw-retained to a titanium implant-abutment after fatigue. MATERIAL AND METHODS: Forty titanium implants were placed in polyacetal to mimic bone support...
August 7, 2018: Journal of Prosthetic Dentistry
Hui-Min Li, Ren-Jie Zhang, Hai Gao, Chong-Yu Jia, Tao Xing, Jian-Xiang Zhang, Fu-Long Dong, Cai-Liang Shen
OBJECTIVE: Selecting optimal strategies for improving fixation in the osteoporotic lumbar spine remains an important issue in clinical research. Cortical bone trajectory (CBT) screws have been proven to enhance screw pullout strength. However, the biomechanical efficacy of these screws remains understudied. The aim of this study was to evaluate the biomechanical efficacy of CBT screws in the osteoporotic lumbar spine. METHODS: A total of 31 vertebrae from 14 cadaveric lumbar spines were obtained...
August 6, 2018: World Neurosurgery
Mário Tanomaru-Filho, Camila Galletti Espir, Ana Carolina Venção, Nathaly Macedo-Serrano, Jader Camilo-Pinto, JulianeMaria Guerreiro-Tanomaru
Introduction: This study compared the cyclic fatigue resistance (CFR) of new instruments manufactured by heat-treated nickel-titanium wire. Methods and Materials: Ninety-six new instruments from HyFlex CM (HF), Edge File (EF), Pro Design S (PDS/L) and Mtwo (MT) (20/0.06 and 25/0.06) ( n =12) systems were evaluated. A stainless steel device was used and time and number of cycles to fracture (NCF) were observed. Fragments were measured and fracture surface was evaluated using scanning electron microscope (SEM)...
2018: Iranian Endodontic Journal
Pedro Duarte, Paula Barcellos da Silva, Murilo Priori Alcalde, Rodrigo Ricci Vivan, Ricardo Abreu da Rosa, Marco Antonio Húngaro Duarte, Marcus Vinícius Reis Só
INTRODUCTION: This study compared the cyclic fatigue and the canal transportation promoted by Twisted File (TF) Adaptive and Navigator EVO systems when used with 2 different motions. METHODS: Forty mesiobuccal roots of maxillary molars were scanned by using micro-computed tomography imaging before and after root canal preparation with the 2 instrument systems used with 2 motions (adaptive and continuous rotation). Samples were divided into 4 groups: TFA, TF Adaptive instruments under adaptive motion; TFC, TF Adaptive instruments under continuous motion; NA, Navigator instruments under adaptive motion; and NC, Navigator instruments under continuous motion...
August 2, 2018: Journal of Endodontics
Y J Yang, B X Hou, X M Hou
Objective: To compare the phase transformation behavior, bending property and cyclic fatigue resistance of CM-wire, R-phase and M-wire nickel-titanium endodontic files treated by 3 heat treatment techniques. Methods: Hyflex CM (25 mm, 25#/0.06) made from CM wire, TF (25 mm, 25#/0.06) made from R-phase heat treatment, ProTaper Next X2 (25 mm, tip size 25#/0.06) made from M-wire, Mtwo (25 mm, 25#/0.06) and ProTaper F2 (25 mm, tip size 25#/0.08) made from conventional nickel-titanium wire were chosen. Five of each files were chosen for differential scanning calorimetric (DSC) evaluation ( n= 5)...
August 9, 2018: Zhonghua Kou Qiang Yi Xue za Zhi, Zhonghua Kouqiang Yixue Zazhi, Chinese Journal of Stomatology
Yonggang Liu, Shanshan Gao, Yongsheng Han, Qixiang Yang, Dwayne Arola, Dongsheng Zhang
The objective of this study was to compare the resistance to failure of three types of all-ceramic crowns under static and cyclic contact loading. Three types of crown specimens were fabricated (N = 14 per group) including: i) sintered bi-layer crowns (SBC) made of IPS e.max CAD veneers fused on Lava zirconia core ceramics, ii) adhesive bi-layer crowns (ABC) made of IPS e.max CAD veneers bonded onto Lava zirconia core ceramics, and iii) monolith ceramics crown (MCC) made of IPS e.max CAD. All were bonded onto a compliant substrate of resin composite with commercial adhesive...
July 25, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Lanqing Tang, Caifu Qian, Ayhan Ince, Jing Zheng, Huifang Li, Zhichao Han
In this paper, the fatigue crack growth behavior of the base metal (BM), the weld metal (WM) and the heat-affected zone (HAZ) in the metal-inert gas (MIG) welded joints of the 06Cr19Ni10 stainless steel are analyzed and studied. Results of the fatigue crack propagation tests show that a new fatigue crack initiates at the crack tip of a pre-existing crack, then propagates perpendicular to the direction of cyclic fatigue loads. This observation indicates that the original mixed-mode crack transforms into the mode I crack...
August 2, 2018: Materials
Saeed Jerban, Yajun Ma, Amin Nazaran, Erik W Dorthe, Esther Cory, Michael Carl, Darryl D'Lima, Robert L Sah, Eric Y Chang, Jiang Du
Bone stress injury (BSI) incidents have been increasing amongst athletes in recent years as a result of more intense sporting activities. Cortical bone in the tibia and fibula is one of the most common BSI sites. Nowadays, clinical magnetic resonance imaging (MRI) is the recommended technique for BSI diagnosis at an early stage. However, clinical MRI focuses on edema observations in surrounding soft tissues, rather than the injured components of the bone. Specifically, both normal and injured bone are invisible in conventional clinical MRI...
July 30, 2018: NMR in Biomedicine
Mario Scholze, Aqeeda Singh, Pamela F Lozano, Benjamin Ondruschka, Maziar Ramezani, Michael Werner, Niels Hammer
Three-dimensional (3D) printing has become broadly available and can be utilized to customize clamping mechanisms in biomechanical experiments. This report will describe our experience using 3D printed clamps to mount soft tissues from different anatomical regions. The feasibility and potential limitations of the technology will be discussed. Tissues were sourced in a fresh condition, including human skin, ligaments and tendons. Standardized clamps and fixtures were 3D printed and used to mount specimens. In quasi-static tensile tests combined with digital image correlation and fatigue trials we characterized the applicability of the clamping technique...
July 27, 2018: Scientific Reports
Burcu Serefoglu, Mehmet Emin Kaval, Seniha Micoogullari Kurt, Mehmet Kemal Çalişkan
INTRODUCTION: The aim of the present study was to evaluate the cyclic fatigue resistance of the WaveOne Gold Glider (Dentsply Maillefer, Ballaigues, Switzerland), R-Pilot (VDW, Munich, Germany), and ProGlider (Dentsply Maillefer) glide path instruments. METHODS: Ten instruments from each glide path system were included in the study. A stainless steel artificial canal with a 90° angle and a 3-mm radius of curvature was used for the testing process. The working lengths of the instruments were fixed at 19 mm, and the instruments were operated using an endodontic motor (X-Smart Plus, Dentsply Maillefer) at recommended setting for each...
July 23, 2018: Journal of Endodontics
Catina Prochnow, Andressa Borin Venturini, Luís Felipe Guilardi, Gabriel Kalil Rocha Pereira, Thiago Augusto Lima Burgo, Marco Cícero Bottino, Cornelis Johannes Kleverlaan, Luiz Felipe Valandro
OBJECTIVES: To evaluate the effects of the etching with different hydrofluoric acid (HF) concentrations on the cyclic load-to-failure (CLf ) of machined lithium disilicate crowns cemented to dentin analogue material. METHODS: Pairs of dentin analogue prosthetic preparations and lithium disilicate ceramic crowns with simplified and standardized designs were machined (n=18). The preparations were etched with 10% HF (60s), followed by primer application. The intaglio surface of the ceramic crowns was treated as follows: non-etched (control, CTRL); or etched for 20s with different HF concentrations - 3% (HF3), or 5% (HF5), or 10% (HF10)...
July 18, 2018: Dental Materials: Official Publication of the Academy of Dental Materials
Taishi Hirai, Jonathan Rosenberg, Sandeep Nathan, John E A Blair
A 68-year-old female with a history of coronary artery disease and prior bypass surgery presented for staged percutaneous coronary intervention (PCI) to a calcified and angulated ostial left circumflex (LCX) artery lesion after PCI of the anastomosis of the left internal mammary artery - to left anterior descending artery. Orbital atherectomy of the LCX was performed at a speed of 80,000 RPM with multiple passes, and was complicated by device microtip dislodgement and entrapment within the vessel. After advancing a "buddy" wire beyond the microtip, a tapered microcatheter was advanced over the ViperWire and into the edge of the broken microtip and torqued into the microtip with forward pressure using the 0...
July 18, 2018: Catheterization and Cardiovascular Interventions
Hooman Sedghamiz, Matthew Morris, Travis J A Craddock, Darrell Whitley, Gordon Broderick
BACKGROUND: The hypothalamic-pituitary-adrenal (HPA) axis is a central regulator of stress response and its dysfunction has been associated with a broad range of complex illnesses including Gulf War Illness (GWI) and Chronic Fatigue Syndrome (CFS). Though classical mathematical approaches have been used to model HPA function in isolation, its broad regulatory interactions with immune and central nervous function are such that the biological fidelity of simulations is undermined by the limited availability of reliable parameter estimates...
July 17, 2018: BMC Systems Biology
Paul Le Floch, Shi Meixuanzi, Jingda Tang, Junjie Liu, Zhigang Suo
Many stretchable electronic devices require stretchable hermetic seals. However, stretchability and permeability are inextricably linked at the molecular level: stretchable, low-permeability materials do not exist. We collect data for the permeation of water and oxygen in many materials and describe the scaling relations for both flat and wrinkled seals. Whereas flat seals struggle to fulfill the simultaneous requirements of stretchability, low stiffness, and low transmissibility, wrinkled seals can fulfill them readily...
July 31, 2018: ACS Applied Materials & Interfaces
Shuai Han, Dongdong Li, Peixun Zhang, Xiaofeng Yin, Yuhui Kou, Na Han, Zhongguo Fu
Pain and reoperation after fixation using tension band wiring and K-wires is not uncommon. A novel hook plate was designed to improve the treatment of patella fractures. The aim of this study was to compare the stability of the hook plate with that of tension band wiring and K-wires in a simulated patellar transverse fracture model (AO/OTA classification 34-C1.1). The authors tested 16 embalmed cadaver knee joints fixed with the hook plate and tension band wiring and K-wires under cyclic loading. Specimens underwent 100 cycles extending the knee joint from 90° of flexion to full extension at a velocity of 50 mm/min...
July 16, 2018: Orthopedics
Atsushi Hosoi, Hiroyuki Kawada
Carbon fiber reinforced plastic (CFRP) laminates are used as main structural members in many applications. Transverse cracks that form in 90° layers of CFRP laminates are mostly initial damage in the case where tensile loading is vertically applied to the 90° layers of CFRP laminates, and they are the origin of more serious damage of delamination and fiber breakage. It is thus important to predict quantitatively the transverse crack initiation of CFRP laminates subjected to cyclic loading to ensure the long-term reliability of the laminates...
July 10, 2018: Materials
X Gong, X Y Zhao, C B Zhang, S B Li, Y L Wu, B Wu
Objective: To evaluate the effect of sandblasting on bending strength and subcritical crack growth (SCG) under cyclic loading of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics. Methods: After being polished, sixty bar-shaped specimens of Y-TZP (Wieland zirconia ceramics) were assigned to two groups ( n= 30) according to the random number table, the sandblasting group (SG) which was treated with sandblasting and the control group (CG) which remained untouched. In each group, half of the specimens ( n= 15) were subjected to bending strength test, and the results were examined by Weibull statistics and analyzed with ANOVA...
July 9, 2017: Zhonghua Kou Qiang Yi Xue za Zhi, Zhonghua Kouqiang Yixue Zazhi, Chinese Journal of Stomatology
Y L Tan, H Y Voon, N Ngeh
We report the peculiar case of a patient who consumed raw rice daily and had iron-deficiency anaemia secondary to menorrhagia with underlying polycystic ovarian syndrome. A 32-year-old lady of Asian descent presented with symptoms of fatigue, lethargy and prolonged, irregular periods for the last two months. There was noticeable increase in body weight, male pattern alopecia and facial acne. In addition, she experienced sudden, unexplained predilection towards consumption of raw rice (up to 300- 400g/day). The patient was treated with oral iron and cyclical progestin...
June 2018: Medical Journal of Malaysia
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