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https://www.readbyqxmd.com/read/28927925/optical-properties-of-zirconia-ceramics-for-esthetic-dental-restorations-a-systematic-review
#1
REVIEW
Reza Shahmiri, Owen Christopher Standard, Judy N Hart, Charles Christopher Sorrell
STATEMENT OF PROBLEM: Yttria-stabilized tetragonal zirconia polycrystal has been used as a dental biomaterial for several decades because the fracture toughness and bend strength are increased by a stress-induced transformation-toughening mechanism. However, its esthetics are compromised by its poor translucency and grayish-white appearance. PURPOSE: The purpose of the present systematic review was to assess information on the mechanical, chemical, and optical requirements of monolithic zirconia dental restorations...
September 16, 2017: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/28923547/how-oral-environment-simulation-affects-ceramic-failure-behavior
#2
Ediléia Lodi, Kátia R Weber, Paula Benetti, Pedro H Corazza, Álvaro Della Bona, Márcia Borba
STATEMENT OF PROBLEM: Investigating the mechanical behavior of ceramics in a clinically simulated scenario contributes to the development of new and tougher materials, improving the clinical performance of restorations. The optimal in vitro environment for testing is unclear. PURPOSE: The purpose of this in vitro study was to investigate the failure behavior of a leucite-reinforced glass-ceramic under compression loading and fatigue in different simulated oral environment conditions...
September 16, 2017: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/28921994/anisotropic-cracking-of-nanocrystal-superlattices
#3
Benjamin T Diroll, Xuedan Ma, Yaoting Wu, Christopher B Murray
The synthesis colloidal nanocrystals in non-polar organic solvents has led to exceptional size- and shape-control, enabling the formation of nanocrystal superlattices isostructural to atomic lattices built with nanocrystals rather than atoms. The long aliphatic ligands (e.g. oleic acid) used to achieve this control separate nanocrystals too far in the solid-state for most charge-transporting devices. Solid-state ligand exchange, which brings particles closer together and enhances conductivity, necessitates large changes in the total volume of the solid (compressive stress), which leads to film cracking...
September 18, 2017: Nano Letters
https://www.readbyqxmd.com/read/28921481/negative-magnetic-resonance-imaging-in-three-cases-of-anterior-tibial-cortex-stress-fractures
#4
Ralph Smith, M Moghal, J L Newton, N Jones, J Teh
Anterior mid-tibial cortex stress fractures (ATCSF) are uncommon and notoriously challenging to treat. They are termed high risk due to their predilection to prolonged recovery, nonunion and complete fracture. Early diagnosis is essential to avoid progression and reduce fracture complications. Imaging plays a key role in confirming the diagnosis. Magnetic resonance imaging (MRI) is accepted as the gold standard modality due to its high accuracy and nonionizing properties. This report describes three cases of ATCSFs in recreational athletes who had positive radiographic findings with no significant MRI changes...
September 18, 2017: Skeletal Radiology
https://www.readbyqxmd.com/read/28918227/bone-remodeling-of-the-distal-femur-after-uncemented-total-knee-arthroplasty-a-2-year-prospective-dxa-study
#5
Mikkel Rathsach Andersen, Nikolaj S Winther, Thomas Lind, Henrik M Schrøder, Michael Mørk Petersen
Loss of bone stock as a response to the bone trauma, immobilization, and stress shielding related to joint replacement surgery increases the risk of fracture of the distal femur after total knee arthroplasty. Previous studies of uncemented femoral components have reported very high levels of bone loss in the distal femur. This study investigates the adaptive bone remodeling of the distal femur after uncemented total knee arthroplasty. We performed a 2-year follow-up of 53 patients (mean age 61.5 [38-70] years, F/M = 27/26, body mass index 29...
September 13, 2017: Journal of Clinical Densitometry
https://www.readbyqxmd.com/read/28915360/risk-factors-for-reoperation-and-performance-based-outcomes-after-operative-fixation-of-foot-fractures-in-the-professional-athlete-a-cross-sport-analysis
#6
Sameer Singh, Kevin Larkin, Anish Kadakia, Wellington Hsu
BACKGROUND: Professional athletes are predisposed to fractures of the foot due to large stresses placed on the lower extremity. These players are concerned with efficiently returning to play at a high level. Return-to-play rates after operative treatment have been previously reported, yet performance outcomes after such treatment are generally unknown in this population. HYPOTHESIS: Overall, professional athletes sustaining a foot fracture would return to play at high rates with little impact on post-operative performance or league participation...
September 1, 2017: Sports Health
https://www.readbyqxmd.com/read/28902430/reduced-serum-igf-1-associated-with-hepatic-osteodystrophy-is-a-main-determinant-of-low-cortical-but-not-trabecular-bone-mass
#7
Zhongbo Liu, Tianzhen Han, Haim Werner, Clifford J Rosen, Mitchell B Schaffler, Shoshana Yakar
Hepatic osteodystrophy is multifactorial in its pathogenesis. Numerous studies have shown that impairments of the hepatic growth hormone/insulin-like growth factor-1 axis (GH/IGF-1) are common in patients with non-alcoholic fatty liver disease, chronic viral hepatitis, liver cirrhosis, and chronic cholestatic liver disease. Moreover these conditions are also associated with low bone mineral density (BMD) and greater fracture risk, particularly in cortical bone sites. Hence, we addressed whether disruptions in the GH/IGF-1 axis were causally related to the low bone mass in states of chronic liver disease using a mouse model of liver-specific GH-receptor (GHR) gene deletion (Li-GHRKO)...
September 13, 2017: Journal of Bone and Mineral Research: the Official Journal of the American Society for Bone and Mineral Research
https://www.readbyqxmd.com/read/28902242/polymerization-shrinkage-stress-of-composite-resins-and-resin-cements-what-do-we-need-to-know
#8
Carlos José Soares, André Luis Faria-E-Silva, Monise de Paula Rodrigues, Andomar Bruno Fernandes Vilela, Carmem Silvia Pfeifer, Daranee Tantbirojn, Antheunis Versluis
Polymerization shrinkage stress of resin-based materials have been related to several unwanted clinical consequences, such as enamel crack propagation, cusp deflection, marginal and internal gaps, and decreased bond strength. Despite the absence of strong evidence relating polymerization shrinkage to secondary caries or fracture of posterior teeth, shrinkage stress has been associated with post-operative sensitivity and marginal stain. The latter is often erroneously used as a criterion for replacement of composite restorations...
August 28, 2017: Brazilian Oral Research
https://www.readbyqxmd.com/read/28902236/should-my-composite-restorations-last-forever-why-are-they-failing
#9
Flávio Fernando Demarco, Kauê Collares, Marcos Britto Correa, Maximiliano Sergio Cenci, Rafael Ratto de Moraes, Niek Johannes Opdam
Composites resins have become the first choice for direct anterior and posterior restorations. The great popularity is related to their esthetic appearance and reduced need of sound tissue removal as compared with former treatments. Several studies have demonstrated that composite restorations may last long in clinical service. In this review we discuss the factors playing a role on the long-term longevity. Composite restorations have demonstrated a good clinical performance with annual failure rates varying from 1% to 3% in posterior teeth and 1% to 5% in anterior teeth...
August 28, 2017: Brazilian Oral Research
https://www.readbyqxmd.com/read/28899823/a-predictive-radiological-analysis-of-short-stems-versus-both-shortened-and-long-stems-in-primary-hip-replacement-a-case-control-study-of-100-cases-of-metha-versus-abg-ii-and-omnifit-ha-at-2-8-years-follow-up
#10
Jean-Alain Epinette, Michel Brax, Yves Chammaï
INTRODUCTION: Short hip stems, intended to conserve bone stock and ensure a more physiological distribution of stress in the femur under loading, are meeting with renewed interest. Radiologic semiology is not known exactly, particularly in relation to conventional implants; we therefore conducted a case-control study of 3 types of implant differing only in stem length: short, shortened or long. The aim was 1) to compare radiographic aspects, 2) to attempt to systematize medium-term radiologic status for the 3 types, and 3) to assess the impact of radiographic aspect on loosening and revision rates...
September 9, 2017: Orthopaedics & Traumatology, Surgery & Research: OTSR
https://www.readbyqxmd.com/read/28894221/temperature-controlled-direct-imprinting-of-ag-ionic-ink-flexible-metal-grid-transparent-conductors-with-enhanced-electromechanical-durability
#11
Yong Suk Oh, Hyesun Choi, Jaeho Lee, Hyunwoo Lee, Dong Yun Choi, Sung-Uk Lee, Kyeong-Soo Yun, Seunghyup Yoo, Taek-Soo Kim, Inkyu Park, Hyung Jin Sung
Next-generation transparent conductors (TCs) require excellent electromechanical durability under mechanical deformations as well as high electrical conductivity and transparency. Here we introduce a method for the fabrication of highly conductive, low-porosity, flexible metal grid TCs via temperature-controlled direct imprinting (TCDI) of Ag ionic ink. The TCDI technique based on two-step heating is capable of not only stably capturing the Ag ionic ink, but also reducing the porosity of thermally decomposed Ag nanoparticle structures by eliminating large amounts of organic complexes...
September 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28893491/micro-finite-element-method-to-assess-elastic-properties-of-trabecular-bone-at-micro-and-macroscopic-level
#12
R Rieger, J C Auregan, T Hoc
OBJECTIVE OF THE STUDY: The objective of the present study is to assess the mechanical behavior of trabecular bone based on microCT imaging and micro-finite-element analysis. In this way two methods are detailed: (i) direct determination of macroscopic elastic property of trabecular bone; (ii) inverse approach to assess mechanical properties of trabecular bone tissue. PATIENTS: Thirty-five females and seven males (forty-two subjects) mean aged (±SD) 80±11.7 years from hospitals of Assistance publique-Hôpitaux de Paris (AP-HP) diagnosed with osteoporosis following a femoral neck fracture due to a fall from standing were included in this study...
September 8, 2017: Morphologie: Bulletin de L'Association des Anatomistes
https://www.readbyqxmd.com/read/28891934/fatigue-properties-of-the-ultra-high-strength-steel-tm210a
#13
Guang-Qiang Yin, Xia Kang, Gui-Ping Zhao
This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = -1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 10⁷ cycles...
September 9, 2017: Materials
https://www.readbyqxmd.com/read/28890727/popliteal-artery-entrapment-or-chronic-exertional-compartment-syndrome
#14
Christopher Gaunder, Brandon McKinney, Jessica Rivera
Diagnosis of lower limb pain in an athlete can be a challenging task due to the variety of potential etiologies and ambiguity of presenting symptoms. Five of the most commonly encountered causes of limb pain in athletes are chronic exertional compartment syndrome (CECS), medial tibial stress syndrome (MTSS), tibial stress fractures, soleal sling syndrome, and popliteal artery entrapment syndrome (PAES). Of these, the least frequent but potentially most serious of the pathologies is PAES. With an incidence of less than 1% seen in living subject studies, the condition is rare...
2017: Case Reports in Medicine
https://www.readbyqxmd.com/read/28888935/viscoplastic-crack-initiation-and-propagation-in-crosslinked-uhmwpe-from-clinically-relevant-notches-up-to-0-5mm-radius
#15
P Abhiram Sirimamilla, Clare M Rimnac, Jevan Furmanski
Highly crosslinked UHMWPE is now the material of choice for hard-on-soft bearing couples in total joint replacements. However, the fracture resistance of the polymer remains a design concern for increased longevity of the components in vivo. Fracture research utilizing the traditional linear elastic fracture mechanics (LEFM) or elastic plastic fracture mechanics (EPFM) approach has not yielded a definite failure criterion for UHMWPE. Therefore, an advanced viscous fracture model has been applied to various notched compact tension specimen geometries to estimate the fracture resistance of the polymer...
September 1, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28886951/strength-comparison-of-anterior-teeth-restored-with-ceramic-endocrowns-vs-custom-made-post-and-cores
#16
Beata Dejak, Andrzej Młotkowski
PURPOSE: The aim of the study was to compare strength of the anterior teeth restored with ceramic endocrowns versus custom-made post and core. METHODS: The investigation used the finite element analysis. Three 3-D models of maxillary central incisor were created: model A-tooth restored with metal post and core with ceramic crown; model B-tooth with leucite ceramic endocrown; model C-tooth with lithium disilicate ceramic endocrown. Each model was subjected to a 100N force applied at a distance of 5mm from the incisal edge, at the angle of 130° to the long axis of the tooth...
September 5, 2017: Journal of Prosthodontic Research
https://www.readbyqxmd.com/read/28886822/osteopenia-and-osteoporosis-in-female-athletes
#17
REVIEW
John M MacKnight
Disorders of bone density are especially prevalent among athletic women. The severity of bone loss ranges from osteopenia to frank osteoporosis. In female athletes, a higher incidence of osteoporosis is due to a decreased rate of bone accretion in youth, often as a result of hormonal deficiency and/or excessive exercise. Low bone mass poses a particular challenge for athletes because it predisposes to stress-related bone injuries and increases the risk of osteoporosis and insufficiency fractures with aging...
October 2017: Clinics in Sports Medicine
https://www.readbyqxmd.com/read/28885738/wearable-large-scale-perovskite-solar-power-source-via-nanocellular-scaffold
#18
Xiaotian Hu, Zengqi Huang, Xue Zhou, Pengwei Li, Yang Wang, Zhandong Huang, Meng Su, Wanjie Ren, Fengyu Li, Mingzhu Li, Yiwang Chen, Yanlin Song
Dramatic advances in perovskite solar cells (PSCs) and the blossoming of wearable electronics have triggered tremendous demands for flexible solar-power sources. However, the fracturing of functional crystalline films and transmittance wastage from flexible substrates are critical challenges to approaching the high-performance PSCs with flexural endurance. In this work, a nanocellular scaffold is introduced to architect a mechanics buffer layer and optics resonant cavity. The nanocellular scaffold releases mechanical stresses during flexural experiences and significantly improves the crystalline quality of the perovskite films...
September 8, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28884096/finite-element-analysis-of-the-equivalent-stress-distribution-in-schanz-screws-during-the-use-of-a-femoral-fracture-distractor
#19
Vincenzo Giordano, Alexandre Leme Godoy-Santos, William Dias Belangero, Robinson Esteves Santos Pires, Pedro José Labronici, Hilton Augusto Koch
To evaluate the mechanical stress and elastic deformation exercised in the thread/shaft transition of Schanz screws in assemblies with different screw anchorage distances in the entrance to the bone cortex, through the distribution and location of tension in the samples. An analysis of 3D finite elements was performed to evaluate the distribution of the equivalent stress (triple stress state) in a Schanz screw fixed bicortically and orthogonally to a tubular bone, using two mounting patterns: (1) thread/shaft transition located 20 mm from the anchorage of the Schanz screws in the entrance to the bone cortex and (2) thread/shaft transition located 3 mm from the anchorage of the Schanz screws in entrance to the bone cortex...
June 2017: Revista Brasileira de Ortopedia
https://www.readbyqxmd.com/read/28883012/fibular-insufficiency-fracture-an-under-reported-complication-of-advanced-tibialis-posterior-dysfunction
#20
Suresh Srinivasan, Harish Kurup
We present a case of fibular insufficiency (stress) fracture in a patient with pre-existing asymptomatic advanced tibialis posterior dysfunction. The patient had severe planovalgus (flat foot) deformity but no pain before the injury; hence had never sought any treatment. She was first treated conservatively for the fracture which failed to control the deformity and had ongoing symptoms. She eventually required tibio-talo-calcaneal fusion. To the best of our knowledge, this is the first case report of this condition in the English literature...
September 7, 2017: BMJ Case Reports
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