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https://www.readbyqxmd.com/read/28543925/comparative-effect-of-different-polymerization-techniques-on-the-flexural-and-surface-properties-of-acrylic-denture-bases
#1
Mohammed M Gad, Shaimaa M Fouda, Aws S ArRejaie, Ahmad M Al-Thobity
PURPOSE: Polymerization techniques have been modified to improve physical and mechanical properties of polymethylmethacrylate (PMMA) denture base, as have the laboratory procedures that facilitate denture construction techniques. The purpose of the present study was to investigate the effect of autoclave polymerization on flexural strength, elastic modulus, surface roughness, and the hardness of PMMA denture base resins. MATERIALS AND METHODS: Major Base and Vertex Implacryl heat-polymerized acrylic resins were used to fabricate 180 specimens...
May 22, 2017: Journal of Prosthodontics: Official Journal of the American College of Prosthodontists
https://www.readbyqxmd.com/read/28543707/viable-bacteria-persist-on-antibiotic-spacers-following-two-stage-revision-for-periprosthetic-joint-infection
#2
Dongzhu Ma, Robert M Q Shanks, Charles M Davis, David W Craft, Thomas K Wood, Brian R Hamlin, Kenneth L Urish
Treatment in periprosthetic joint infection (PJI) remains challenging. The failure rate of two-stage revision and irrigation and debridement with component retention in PJI suggests that biofilm cells have a high tolerance to antibiotic chemotherapy. Previous work has demonstrated that biofilm cells have high antibiotic tolerance in vitro, but there is little clinical evidence to support these observations. The aim of this study was to determine if retrieved antibiotic spacers from two-stage revision total knee arthroplasty for PJI have evidence of remaining viable bacteria...
May 19, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28543702/microencapsulation-of-rifampicin-a-technique-to-preserve-the-mechanical-properties-of-bone-cement
#3
P Sanz-Ruiz, E Carbó-Laso, J C Del Real-Romero, F Arán-Ais, Y Ballesteros-Iglesias, E Paz-Jiménez, M Sánchez-Navarro, M A Pérez-Limiñana, J Vaquero-Martín
Two-stage exchange with antibiotic-loaded bone cement spacers remains the gold standard for chronic periprosthetic joint infection(PJI). Rifampicin is highly efficient on stationary-phase staphylococci in biofilm; however, its addition to PMMA to manufacture spacers prevents polymerization and reduces mechanical properties. Isolation of rifampicin during polymerization by microencapsulation could allow manufacturing rifampicin-loaded bone cement maintaining elution and mechanical properties. Microcapsules of rifampicin with alginate, polyhydroxybutyratehydroxyvalerate (PHBV), ethylcellulose and stearic acid (SA) were synthesized...
May 23, 2017: Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society
https://www.readbyqxmd.com/read/28543304/biomechanical-comparison-between-pins-and-polymethylmethacrylate-and-the-sop-locking-plate-system-to-stabilize-canine-lumbosacral-fracture-luxation-in-flexion-and-extension
#4
Johannes J Nel, Cor-Jacques Kat, Gert L Coetzee, Paul J van Staden
OBJECTIVE: To determine the stability of a simulated complete L7-S1 fracture-luxation immobilized with SOP locking plate system, compared to pins and polymethylmethacrylate (PMMA). STUDY DESIGN: In vitro biomechanical study. ANIMALS: Cadaver specimens of 18 skeletally mature large-breed dogs. MATERIALS AND METHODS: Specimens were randomly stabilized with one of the two fixation techniques. Lumbosacral spine specimens (L5-S3) were subjected to a bending moment applied to the caudal and cranial ends of the specimen...
May 24, 2017: Veterinary Surgery: VS
https://www.readbyqxmd.com/read/28541658/characterizing-patterned-block-copolymer-thin-films-with-soft-x-rays
#5
Daniel F Sunday, Jiaxing Ren, Christopher D Liman, Lance D Williamson, Roel Gronheid, Paul F Nealey, R Joseph Kline
The directed self-assembly (DSA) of block copolymers (BCPs) is a potential solution for patterning critical features for integrated circuits at future technology nodes. In order for this process to be implemented there needs to be a better understanding of how the template guides the assembly and induces subsurface changes in the lamellar structure. Using a rotational transmission X-ray scattering measurement coupled with soft X-rays to improve contrast between polymer components, the impact of the ratio of the guiding stripe width (W) to the BCP pitch (Lo) was investigated...
May 25, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28540008/predictors-of-successful-laser-capsulotomy-for-significant-posterior-capsule-opacification-after-phacoemulsification
#6
Brijesh Takkar, Parijat Chandra, Shreyas Temkar, Ashutosh Kumar Singh, Indrish Bhatia
PURPOSE: This study aimed to determine the reasons behind the failure of laser capsulotomy (LC) performed for significant posterior capsular opacification (PCO). METHODS: Eighty-eight eyes of 88 patients referred for LC at a tertiary care center were retrospectively analyzed. The data recorded included the cause of cataract, visual acuity, duration of PCO, location of PCO, intraocular lens (IOL) position, IOL type, and lens capsule status. These data were later analyzed for determining the requirement of high pulse energy during LC and the success rate of primary LC...
April 2017: Journal of Ophthalmic & Vision Research
https://www.readbyqxmd.com/read/28537751/using-neutron-reflectometry-to-characterize-antimicrobial-protein-surface-coatings
#7
Peter W Akers, Andrew J Dingley, Simon Swift, Andrew R J Nelson, Julie Martin, Duncan James McGillivray
Understanding the interaction of adsorbed or covalently immobilized proteins with solid substrates at the molecular level guides the successful design of functionalized surfaces used in biomedical applications. In this report, neutron reflectometry (NR) was used to characterize the structure of surface-attached antimicrobial protein films, with antimicrobial activity assessed using an adaption of the Japanese Industrial Standard Test JIS Z 2801. NR allowed parameters influencing bioactivity to be measured at nanometer resolution and for conclusions about structural characteristics relating to bioactivity to be drawn...
May 24, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28535540/development-of-a-synthetic-substrate-for-the-in-vitro-performance-testing-of-sunscreens
#8
Myriam Sohn, Camille Malburet, Laure Baptiste, Yvonne Prigl
PURPOSE: Polymethylmethacrylate (PMMA) plates generally used for the in vitro testing of sunscreens have failed to yield a satisfactory correlation between the sun protection factor (SPF) in vitro and that in vivo. In the present study, various polymers were investigated as alternative substrates to PMMA plates. PROCEDURES: In total, 14 polymers were tested in terms of ultraviolet (UV) transparency by transmission spectroscopy, and surface properties by contact angle measurement...
May 24, 2017: Skin Pharmacology and Physiology
https://www.readbyqxmd.com/read/28534289/exposure-of-articular-chondrocytes-to-wear-particles-induces-phagocytosis-differential-inflammatory-gene-expression-and-reduced-proliferation
#9
Michael D Kurdziel, Meagan Salisbury, Lige Kaplan, Tristan Maerz, Kevin C Baker
The production of wear debris particulate remains a concern due to its association with implant failure through complex biologic interactions. In the setting of unicompartmental knee arthroplasty (UKA), damage and wear of the components may introduce debris particulate into the adjacent, otherwise, healthy compartment. The purpose of this study was to investigate the in vitro effect of polymeric and metallic wear debris particles on cell proliferation, extracellular matrix regulation, and phagocytosis index of normal human articular chondrocytes (nHACs)...
July 2017: Journal of Materials Science. Materials in Medicine
https://www.readbyqxmd.com/read/28534055/experimental-determination-of-surface-heat-transfer-coefficient-in-a-dry-ice-ethanol-cooling-bath-using-a-numerical-approach
#10
M V Santos, M Sansinena, N Zaritzky, J Chirife
  BACKGROUND: Dry ice-ethanol bath (-78 degree C) have been widely used in low temperature biological research to attain rapid cooling of samples below freezing temperature. The prediction of cooling rates of biological samples immersed in dry ice-ethanol bath is of practical interest in cryopreservation. The cooling rate can be obtained using mathematical models representing the heat conduction equation in transient state. Additionally, at the solid cryogenic-fluid interface, the knowledge of the surface heat transfer coefficient (h) is necessary for the convective boundary condition in order to correctly establish the mathematical problem...
March 2017: Cryo Letters
https://www.readbyqxmd.com/read/28531971/graphene-oxide-versus-graphene-for-optimisation-of-pmma-bone-cement-for-orthopaedic-applications
#11
E Paz, F Forriol, J C Del Real, N Dunne
Graphene (G) and graphene oxide (GO) nano-sized powders with loadings ranging from 0.1 to 1.0wt% were investigated as reinforced agents for polymethyl methacrylate (PMMA) bone cements. The mechanical properties (i.e. bend strength, bend modulus, compression strength, fracture toughness and fatigue performance) and the thermal properties (i.e. maximum temperature, setting time, curing heat and residual monomer) of the resultant nanocomposites were characterised. The mechanical performance of G-PMMA and GO-PMMA bone cements has been improved at low loadings (≤0...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28526447/toxicity-screening-of-a-novel-poly-methylmethacrylate-eudragit-nanocarrier-on-l929-fibroblasts
#12
Diogo Graça, Henriqueta Louro, Joana Santos, Kamila Dias, Lídia Gonçalves, António Almeida, Maria João Silva, Ana Bettencourt
Toxicity screening of a novel poly(methylmethacrylate)-Eudragit nanocarrier on L929 fibroblasts Translation of innovative drug delivery nanosystems into the market involves an early toxicity screening in the development phase. Previously, we showed that inclusion of the polymer (Eudragit, EUD) into poly(methylmethacrylate) (PMMA) nanoparticles (NP) resulted in a novel nanocarrier (PMMA-EUD) with an improved biomedical performance. The safety of this novel nanoparticulate system (PMMA-EUDNPs) was assessed in this work and compared to that of the original PMMANPs by using an integrated approach, comprising in vitro toxicity assessment and NPs physicochemical characterization in water and cell medium...
May 16, 2017: Toxicology Letters
https://www.readbyqxmd.com/read/28524873/mesoporous-metallic-rhodium-nanoparticles
#13
Bo Jiang, Cuiling Li, Ömer Dag, Hideki Abe, Toshiaki Takei, Tsubasa Imai, Md Shahriar A Hossain, Md Tofazzal Islam, Kathleen Wood, Joel Henzie, Yusuke Yamauchi
Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]...
May 19, 2017: Nature Communications
https://www.readbyqxmd.com/read/28522402/prophylactic-vertebral-cement-augmentation-at-the-uppermost-instrumented-vertebra-and-rostral-adjacent-vertebra-for-the-prevention-of-proximal-junctional-kyphosis-and-failure-following-long-segment-fusion-for-adult-spinal-deformity
#14
George M Ghobrial, Daniel G Eichberg, John Paul G Kolcun, Karthik Madhavan, Nathan H Lebwohl, Barth A Green, Joseph P Gjolaj
BACKGROUND CONTEXT: Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are common problems after long segment (>5 levels) thoracolumbar instrumented fusions in the treatment of adult spinal deformity (ASD). No specific surgical strategy has definitively been shown to lower the risk of PJK as the result of a multifactorial etiology. PURPOSE: To assess the incidence of PJK and PJF in patients treated with prophylactic polymethylmethacrylate(PMMA) cement augmentation at the uppermost instrumented vertebrae(UIV) and rostral adjacent vertebrae(UIV+1)...
May 15, 2017: Spine Journal: Official Journal of the North American Spine Society
https://www.readbyqxmd.com/read/28521981/self-assembly-of-maltoheptaose-b-pmma-block-copolymer-systems-10nm-resolution-in-thin-film-and-bulk-states
#15
C M Noronha, I Otsuka, C Bouilhac, C Rochas, P L M Barreto, R Borsali
This paper describes the self-assembly of oligosaccharide-based hybrid block copolymers (BCPs) consisting of maltoheptaose (MH) and poly(methyl methacrylate) (PMMA) into 10nm scale lamellar and cylindrical phases depending on the volume fractions of MH (ϕMH) and the annealing process. Time resolved SAXS study of the BCP bulk samples during thermal annealing indicated that the BCPs phase separate into 10nm scale periodical structures. The solvent vapor annealing induced self-organizations of the BCP into different phases depending on ϕMH and the weight fraction of THF/H2O...
August 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28514349/-elastic-properties-and-porosity-of-dental-blocks-made-from-non-metal-materials-used-for-chairside-cad-cam-crowns
#16
K E Goryainova, E S Morokov, M V Retinskaya, I J Lebedenko
Elastic properties and internal structure of glass-ceramic, feldspatic ceramic, PMMA and hybrid blocks for chairside CAD/CAM dental crowns were assessed by pulsed acoustic microscopy. Elastic modulus of hybrid ceramic was 1.5 times inferior to feldspatic ceramic and glass-ceramic but almost 10 times higher than those of polymer samples. We found the presence of pores from a few to hundreds of microns in the bulk of inorganic materials samples, isolated point defects were revealed in polymer materials while in hybrid material defects were not found...
2017: Stomatologii︠a︡
https://www.readbyqxmd.com/read/28512783/effect-of-silver-loaded-pmma-on-streptococcus-mutans-in-a-drip-flow-reactor
#17
Dustin L Williams, R Tyler Epperson, Jeffery P DeGrauw, Mattias B Nielsen, Nicholas B Taylor, Ryan D Jolley
Orthodontic retention has been proposed as a life-long commitment for patients who desire to maintain straight teeth. However, the presence of foreign material increases risk of bacterial colonization and caries formation, of which Streptococcus mutans is a key contributor. Multiple studies have assessed the ability of silver to be added to base plate material and resist attachment of S. mutans. However, it does not appear that long term washout in connection with biofilm growth under physiologically relevant conditions has been taken into consideration...
May 16, 2017: Journal of Biomedical Materials Research. Part A
https://www.readbyqxmd.com/read/28512613/comparison-of-complications-following-cranioplasty-using-a-sterilized-autologous-bone-flap-or-polymethyl-methacrylate
#18
Sung Hoon Kim, Dong Soo Kang, Jin Hwan Cheong, Jung Hee Kim, Kwan Young Song, Min Ho Kong
OBJECTIVE: The aims of current study are to compare complications following cranioplasty (CP) using either sterilized autologous bone or polymethyl methacrylate (PMMA), and to identify the risk factors for two of the most common complications: bone flap resorption (BFR) and surgical site infection (SSI). METHODS: Between January 2004 and December 2013, 127 patients underwent CP and were followed at least 12 months. Variables, including sex, age, initial diagnosis, time interval between decompressive craniectomy (DC) and CP, operation time, size of bone flap, and presence of ventriculo-peritoneal shunt, were analyzed to identify the risk factors for BFR and SSI...
April 2017: Korean Journal of Neurotrauma
https://www.readbyqxmd.com/read/28510373/acrylic-reinforcement-with-off-the-shelf-perforated-metal-plates
#19
Nader Abdulhameed, Jean-Francois Roulet, Chiayi Shen
To evaluate the effect of Dentaurum Grid Strengthener on flexural strength and modulus of two types of PMMA, 24 beams (75 mm x 10 mm x 2.5 mm) containing bonded and flattened Grid Strengthener and 24 beams without Grid Strengthener were subjected to a 3-point bending test at 5 mm/min. Flexural strength and modulus were calculated. Data were analyzed with a 2-way ANOVA. The highest mean strength and flexural modulus was measured for reinforced high impact resin (96.2±14.3 MPa and 3425±779 MPa, respectively)...
December 2016: European Journal of Prosthodontics and Restorative Dentistry
https://www.readbyqxmd.com/read/28507457/evaluating-the-performance-of-tg-43-protocol-in-esophageal-hdr-brachytherapy-viewpoint-to-trachea-inhomogeneity
#20
Seyed Mohsen Hosseini Daghigh, Hamid Reza Baghani, Seyed Mahmoud Reza Aghamiri, Seyed Rabi Mahdavi
AIM: The aim of this study is to evaluate the effect of air within trachea on dose calculations of esophageal HDR brachytherapy treatment planning. BACKGROUND: Dose calculations in esophageal HDR brachytherapy treatment planning systems are greatly based on TG-43 protocol which in all materials are considered to be water equivalent. MATERIALS AND METHODS: A cylindrical PMMA phantom with a tube in the center (neck equivalent phantom) accompanied by Flexitron HDR brachytherapy system was used in this study...
July 2017: Reports of Practical Oncology and Radiotherapy
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