The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
M Sharifian - One of the best experts on this subject based on the ideXlab platform.
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atmospheric pressure dbd plasma assisted surface modification of Polymethyl Methacrylate a study on cell growth proliferation and antibacterial properties
Applied Surface Science, 2016Co-Authors: Fatemeh Rezaei, B Shokri, M SharifianAbstract:Abstract This paper reports Polymethyl Methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid–base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.
Pekka K Vallittu - One of the best experts on this subject based on the ideXlab platform.
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effect of cellulose nanofiber content on flexural properties of a model thermoplastic injection molded Polymethyl Methacrylate denture base material
Journal of The Mechanical Behavior of Biomedical Materials, 2020Co-Authors: Yutaka Takahashi, Lippo V J Lassila, Tomohiro Kawaguchi, Hirono Baba, Shu Tashiro, Ippei Hamanaka, Pekka K VallittuAbstract:Abstract Cellulose nanofiber (CNF) made from wood-derived fiber is considered as a potential alternative reinforcing material to conventional fibers. The aim of this study was to investigate the effect of CNF on the flexural properties of CNF-reinforced, injection molded, Polymethyl Methacrylate (PMMA) denture base material. Test specimens were fabricated from a model thermoplastic denture base resin using the injection molding technique. The resin pellets were mixed with CNF (to obtain different weight percentages 5, 10, 15, and 23 wt%). PMMA without CNF served as the control (0 wt%). Prior to the testing, the test specimens (n = 12/group) were water-immersed at 37 °C water for 50 h. The flexural strengths and moduli of the specimens were determined using three-point bending tests. Statistical evaluation included a one-way analysis of variance and the Student-Newman-Keuls test (α = 0.05). The mean and standard deviation of flexural strengths with the addition of 0, 5, 10, 15 and 23% CNF were 49.4 (±0.7), 56.4 (±1.3), 63.5 (±2.0), 72.0 (±4.7), and 96.8 (±4.0) MPa, respectively. The mean and standard deviation of flexural modulus with the addition of the same concentrations of CNF were 1.31 (±0.02), 1.56 (±0.05), 1.99 (±0.14), 2.40 (±0.15), and 3.96 (±0.08) GPa, respectively. The flexural strengths and moduli of the CNF-reinforced PMMA were significantly higher than those of pure PMMA (p
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water sorption and solubility of glass fiber reinforced denture Polymethyl Methacrylate resin
Journal of Prosthetic Dentistry, 1997Co-Authors: Varpu M Miettinen, Pekka K VallittuAbstract:Polymethyl Methacrylate (PMMA) absorbs water slowly over a period of time, primarily because of the polar properties of the resin molecules. The aim of this study was to determine the water sorption and solubility of heat-cured and chemical-cured glass fiber (GF) PMMA composite used in dentures. The test specimens (n = 5) were fabricated from experimental, unidirectional, continuous GF reinforcement; the GF concentration of the test specimens was approximately 11% by weight. Water sorption and solubility were tested in accordance with International Standards Organization specification No. 1567. The results revealed that the type of acrylate had more of an effect on water sorption than did the presence of GF reinforcement in the test specimen (p = 0.001 and p = 0.049, respectively). In the GF-reinforced test specimens the type of PMMA also affected the water sorption values (p = 0.006). GF reinforcement affected the solubility values of the test specimen (p = 0.002), but the type of acrylate had no effect on solubility (p = 0.585). The results of this study suggest that the water sorption and solubility of unreinforced PMMA and PMMA reinforced with GF are in accordance with International Standards Organization specification No. 1567.
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Dimensional accuracy and stability of Polymethyl Methacrylate reinforced with metal wire or with continuous glass fiber
The Journal of prosthetic dentistry, 1996Co-Authors: Pekka K VallittuAbstract:The aim of this study was to determine the dimensional accuracy and stability of denture base Polymethyl Methacrylate (PMMA), which was reinforced in various ways. Autopolymerizing PMMA and heat-cured PMMA were reinforced either with semicircular steel wire or with a prefabricated experimental reinforcement made of continuous E-glass fiber. Control specimens had no reinforcement. The width of each U-shaped test specimen was measured with a digital micrometer under a light microscope immediately after the test specimen was cured and when stored in water for 1, 2, 7, and 14 days. The results revealed that both the type of PMMA and the type of reinforcement affected the dimensional accuracy of the test specimens, especially after 7 and 14 days in water storage (p 0.1). The results suggest that the polymerization shrinkage of PMMA causes lower dimensional accuracy of the test specimens reinforced with glass fiber. This should be considered when glass-fiber reinforcement is used clinically.
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bonding of resin teeth to the Polymethyl Methacrylate denture base material
Acta Odontologica Scandinavica, 1995Co-Authors: Pekka K VallittuAbstract:The objective of this study was to compare bonding of acrylic resin teeth treated in various ways to the Polymethyl Methacrylate (PMMA) denture base material. The joint surface of each acrylic tooth cured to heat-cured or autopolymerizing PMMA was either untreated, ground, or adjusted with mechanical retention. The bond to the PMMA was tested with a three-point loading test. To determine whether the bond failure was adhesive or cohesive, the fracture surfaces were analyzed visually and by scanning electron microscopy. The highest bond strength to both the heat-cured and the autopolymerizing PMMA was obtained by grinding grooves on the joint surface of an acrylic resin tooth before it was cured to the PMMA (p 0.05).
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acrylic resin fiber composite part ii the effect of polymerization shrinkage of Polymethyl Methacrylate applied to fiber roving on transverse strength
Journal of Prosthetic Dentistry, 1994Co-Authors: Pekka K VallittuAbstract:Abstract This study determined the effect of polymerization shrinkage of Polymethyl Methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were'studied by SEM. The fracture resistance of the specimens was statistically different (p
Zhaohui Wang - One of the best experts on this subject based on the ideXlab platform.
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fabrication of high flux and fouling resistant membrane a unique hydrophilic blend of polyvinylidene fluoride polyethylene glycol Polymethyl Methacrylate
Polymer, 2019Co-Authors: Hassan Younas, Yue Zhou, Qianyun Sun, Zhaoliang Cui, Zhaohui WangAbstract:Abstract To overcome the fouling issue of membrane, hydrophilic membrane fabrication is a rich research domain. In this study, hydrophilic membrane was fabricated by incorporating the hydrophilic polymer into dope solution. Polymethyl Methacrylate (PMMA) was blended with polyvinylidene fluoride (PVDF) (12%), polyethylene glycol (PEG) (2%), and N,N dimethyl acetamide (DMAc) solution and membranes were prepared by non-solvent induced phase separation process (NIPS). The synthesized membranes were characterized for their surface and cross-sectional morphology, crystallinity, chemical composition, hydrophilicity, pore size, porosity, permeability, pollutant retention, and fouling resistance. The addition of only PEG to PVDF and PMMA to PVDF increased the porosity, pore size and hydrophilicity of the membrane. Whereas, a combination of both PEG (2%) and PMMA (1%) into PVDF further increased the hydrophilicity (contact angle 60°) and porosity (90%) of the membrane. The maximum pure water flux (PWF) (565 LMH) was also recorded with PVDF-PEG-PMMA membrane without compromising the humic acid (HA) retention rate (80%). Moreover, flux recovery ratio of PVDF-PEG-PMMA membrane was more than 80% with hydraulic flushing. The combination of PEG and PMMA proved to be very effective for improving the properties of PVDF membrane resulting in better flux and antifouling potential of the membrane.
K B Jinesh - One of the best experts on this subject based on the ideXlab platform.
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resistive switching in Polymethyl Methacrylate thin films
Organic Electronics, 2016Co-Authors: Jimmy Mangalam, Shivani Agarwal, A N Resmi, M Sundararajan, K B JineshAbstract:Abstract The origin of the resistive switching in Polymethyl Methacrylate (PMMA) films is studied in this work, analysing the switching mechanism of Ag/PMMA/FTO devices. Significant improvement in the performance occurs upon annealing the sample, indicating that the evaporation of the solvent plays a significant role in the memory behaviour of the devices. The shift in the space-charge-limited conduction regime after the set process shows that the electron mobility has been enhanced by two orders of magnitude upon switching. Voltage stress analyses show that the switching from high-resistive phase to low resistive phase occurs only when the silver electrode is positively biased, which confirms that the origin of switching is Ag+ filament formation through PMMA. The performance of the devices at different temperatures shows that the set and reset voltages increase with temperature. This observation is explained based on the vitrification of the PMMA layer as a result of the increased evaporation of the solvent at higher temperatures.
Johanna R Elfenbein - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vaporized hydrogen peroxide sterilization on the in vitro efficacy of meropenem impregnated Polymethyl Methacrylate beads
American Journal of Veterinary Research, 2019Co-Authors: Myra E Durham, Johanna R ElfenbeinAbstract:OBJECTIVE To evaluate the effects of vaporized hydrogen peroxide (VHP) sterilization on the in vitro antimicrobial efficacy of meropenem-impregnated Polymethyl Methacrylate (M-PMMA) beads. SAMPLE 6...
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evaluation of vaporized hydrogen peroxide sterilization on the in vitro efficacy of meropenem impregnated Polymethyl Methacrylate beads
American Journal of Veterinary Research, 2019Co-Authors: Myra E Durham, Johanna R ElfenbeinAbstract:OBJECTIVE To evaluate the effects of vaporized hydrogen peroxide (VHP) sterilization on the in vitro antimicrobial efficacy of meropenem-impregnated Polymethyl Methacrylate (M-PMMA) beads. SAMPLE 6-mm-diameter Polymethyl Methacrylate beads that were or were not impregnated with meropenem. PROCEDURES Meropenem-free Polymethyl Methacrylate and M-PMMA beads were sterilized by use of an autoclave or VHP or remained unsterilized. To determine the antimicrobial efficacy of each bead-sterilization combination (treatment), Mueller-Hinton agar plates were inoculated with 1 of 6 common equine pathogens, and 1 bead from each treatment was applied to a sixth of each plate. The zone of bacterial inhibition for each treatment was measured after 24 hours. To estimate the duration of antimicrobial elution into a solid or liquid medium, 1 bead from each treatment was transferred every 24 hours to a new Staphylococcus aureus-inoculated agar plate or a tube with PBS solution, and an aliquot of the eluent from each tube was then applied to a paper disc on an S aureus-inoculated agar plate. All agar plates were incubated for 24 hours, and the zone of bacterial inhibition was measured for each treatment. RESULTS In vitro antimicrobial efficacy of M-PMMA beads was retained following VHP sterilization. The duration of antimicrobial elution in solid and liquid media did not differ significantly between unsterilized and VHP-sterilized M-PMMA beads. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that M-PMMA beads retained in vitro antimicrobial activity and eluted the drug for up to 2 weeks after VHP sterilization.
