Abstract Expanded polytetrafluoroethylene (e-PTFE) has been used successfully as a membrane barrier for regeneration procedures. However, when exposed to the oral cavity, its high porosity increases ...the risk of early infection, which can affect surgical outcomes. An alternative to e-PTFE is non-expanded and dense polytetrafluoroethylene (n-PFTE), which results in lower levels of early infection following surgical procedures. The aim of this literature review was to analyze and describe the available literature on n-PFTE, report the indications for use, advantages, disadvantages, surgical protocols, and complications. The medical databases Medline–PubMed and Cochrane Library were searched and supplemented with a hand search for reports published between 1980 and May 2012 on n-PTFE membranes. The search strategy was limited to animal, human, and in vitro studies in dental journals published in English. Twenty-four articles that analyzed the use of n-PTFE as a barrier membrane for guided tissue regeneration and guided bone regeneration around teeth and implants were identified: two in vitro studies, seven experimental studies, and 15 clinical studies. There is limited clinical and histological evidence for the use of n-PTFE membranes at present, with some indications in guided tissue regeneration and guided bone regeneration in immediate implants and fresh extraction sockets.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Aim
This study evaluates biofilm formation and barrier function against Streptococcus oralis of nonresorbable polytetrafluoroethylene (PTFE) guided bone regeneration membranes having expanded ...(e‐PTFE) and dense (d‐PTFE) microstructure.
Materials and Methods
Three e‐PTFE membranes of varying openness, one d‐PTFE membrane, and commercially pure titanium discs were evaluated. All e‐PTFE membranes consisted of PTFE nodes interconnected by fibrils. The d‐PTFE membrane was fibril‐free, with large evenly spaced indentations. The surfaces were challenged with S. oralis and incubated statically for 2‐48h. Bacterial colonization, viability, and penetration were evaluated.
Results
S. oralis numbers increased over time on all surfaces, as observed using scanning electron microscopy, while cell viability decreased, as measured by colony forming unit (CFU) counting. At 24h and 48h, biofilms on d‐PTFE were more mature and thicker (tower formations) than on e‐PTFE, where fewer layers of cells were distributed mainly horizontally. Biofilms accumulated preferentially within d‐PTFE membrane indentations. At 48h, greater biofilm biomass and number of viable S. oralis were found on d‐PTFE compared to e‐PTFE membranes. All membranes were impermeable to S. oralis cells.
Conclusions
All PTFE membranes were effective barriers against bacterial passage in vitro. However, d‐PTFE favored S. oralis biofilm formation.
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CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This research explores the mechanical properties and erosion mechanisms of SS316, VC+TiC, and PTFE coatings to study cavitation erosion resistance. Microhardness analysis revealed that VC+TiC showed ...the highest resilience due to its hardness, while PTFE, despite lower hardness, displayed potential with formulation adjustments. Lasso Regression models effectively predicted mass loss under various testing conditions, indicating strong relationships between independent variables and erosion responses. Scanning Electron Microscopy (SEM) analysis uncovered distinct erosion mechanisms for each coating, with SS316 showing plastic deformation, VC+TiC exhibiting crater formation, and PTFE displaying torn splats. The development of superhydrophobic surfaces from VC+TiC and PTFE coatings offers promising applications in mitigating cavitation erosion, providing valuable material-specific insights into this phenomenon.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A novel self-adjusting PTFE/TiO2 hydrophobic double-layer coating is designed.•The coating is prepared by thermal field/pressure field enhanced plasma electrolytic oxidation.•The ...compact double-layer coating endows titanium alloy excellent insulating protection.•The hydrophobic coating shows superior corrosion resistance and long-term chemical stability.
The self-adjusting polytetrafluoroethylene (PTFE)/TiO2 organic-inorganic double-layer coatings are designed on titanium alloy using thermal field and gradient pressure field enhanced plasma electrolytic oxidation (TGEPEO), which leads to the in-situ incorporation of PTFE nano-particles into the bottom TiO2 ceramic coating. The PTFE top layer with adjustable thickness is strongly bonded on a TiO2 bottom porous layer by subsequent deposition, chemical bonding and crosslinking curing of PTFE nanoparticles during TGEPEO process. Simultaneously, the double-layer coating possesses promising self-cleaning function due to a special hydrophobic surface with a water contact angle of ≈138.0 ± 4.4° caused by self-adjusted surface micro-nano structure. Moreover, the PTFE/TiO2 double-layer coating exhibits excellent corrosion resistance and high electrical insulation. More importantly, the microstructure of the double-layer coating underwent self-adjustment in long-term immersion, caused by the accumulation-redeposition of corrosive ions and the closure of the reticular microchannels at the damaged regions, thus enhancing long-term chemical stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to solve the problems of poor dispersibility and wettability, as well as unsatisfactory wear resistance and load capacity of polytetrafluoroethylene (PTFE) as water lubricating additive, a ...new type of PTFE@silica (PTFE@SiO2) core-shell nanoparticles was prepared by encapsulating SiO2 layer on the surface of PTFE via chemical bonding. Electron microscope analysis showed that the synthesized particles had well-defined core-shell morphology. Special double/multi-core structure and a reduced thickness of the intermediate shell were found, and the formation mechanisms were also explored in detail. The water contact angle measurement proved that the wettability of PTFE could be greatly enhanced by coating SiO2 layer. The friction tests were performed to investigate the water lubrication properties of PTFE@SiO2 additive, the results indicated that the core-shell PTFE@SiO2 nanoparticles possessed the superior tribological properties, and the maximum friction coefficient and wear volume were respectively decreased by 75% and 99% when compared with pure water and water with PTFE/SiO2. Based on the analysis of worn surface, it was believed that the existence of core-shell structure and the formation of robust transfer film were the key to its excellent performance, and a possible lubrication mechanism was also proposed.
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•A novel PTFE@SiO2 core-shell nanoparticles with PTFE as the core and silica as the shell is synthesized.•A special double/multi-core structure and a reduced thickness of the intermediate shell are found.•PTFE@SiO2 exhibits excellent friction reduction and wear resistance properties as water lubrication additives.•The existence of transfer film and core-shell structure ensures the superior tribological properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The Electro-Fenton and persulfate were combined to degrade metronidazole.•The CoFe2O4-PTFE electrode was used in parallel with the acetylene black-PTFE electrode.•The removal rate of ...metronidazole reached 90.6% by ABP/CFOP/PS system after 120 min.•The catalyst exhibited good stability and recyclability for five consecutive cycles.•The intermediates and possible degradation pathways of metronidazole were provided.
A composite electrochemical oxidation system combined with Electro-Fenton and persulfate (PS) was proposed to degrade metronidazole. The CoFe2O4-PTFE (CFOP) electrode was used in parallel with the acetylene black-PTFE electrode (ABP) as the dual-cathode of Electro-Fenton. Then the Electro-Fenton was coupled with PS to degrade metronidazole in wastewater synergistically. The self-produce of H2O2, in-situ circulation of Co(II)/Co(III) and Fe(III)/Fe(II), and activation of persulfate were simultaneously conducted. After 120 min, the removal rate of metronidazole reached 90.6% by ABP/CFOP/PS system. The influence of operation parameters (dosage of PS, initial pH, current density, temperature) on the removal of metronidazole was analyzed. The catalyst exhibited good stability and recyclability for five consecutive cycles. The radical quenching and EPR tests reveal that both OH and SO4−· are identified responsible for the degradation of metronidazole. The possible decomposition pathway of metronidazole was proposed by HPLC-MS analysis. The toxicity analysis indicates that heterogeneous Electro-Fenton could reduce the toxicity of metronidazole.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Graphite particles (80 μm) and PTFE particles (40 μm) were coated with Ni (18–50 wt.%) and PTFE fine particles (0.3 μm; 8 wt.%) via electroless Ni–PTFE composite plating. The conductivity of Ni–PTFE ...plated graphite (C/Ni–PTFE) and PTFE (PTFE/Ni–PTFE) particles increased with the Ni content. At 35 wt.% Ni content, the conductivity (300 Sm
−1) of C/Ni–PTFE particles was about 2 times higher than that of PTFE/Ni–PTFE particles. The particles were pressed into plates under a pressure of 10–500 kg cm
−2 and the plates were then subjected to heat treatment at 350 °C. The surface of C/Ni–PTFE plates contained infinitely many gaps of 0.01–20 μm; these gaps are useful as a pathway for reacting gases. The conductivities in a direction perpendicular and parallel to the C/Ni–PTFE plates were respectively about 3.5 times (510 Sm
−1) and 16 times (48 × 10
3 Sm
−1) higher than those of the PTFE/Ni–PTFE plates. Furthermore, the total pore volume (0.145 cm
3 g
−1) of C/Ni–PTFE plates was higher than that of PTFE/Ni–PTFE plates, which improved the gas permeability of the former. The current density (84 mA cm
−2 at 0.3 V) of C/Ni–PTFE electrode was about 2 times higher than that of PTFE/Ni–PTFE electrode. This increase in the current density might be attributed to the improvement in the total conductivity and gas permeability of C/Ni–PTFE electrode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•The performance of the O2 diffusion cathode is evaluated for the first time in a flow-through system.•The electrogeneration of H2O2 is enhanced 16 times by modifying the ...cathode.•Anodic O2 replaces external O2 supply for the production of H2O2.
Efficient electrogeneration of hydrogen peroxide (H2O2) is critical for treatment of refractory pollutants by the electro-Fenton process. An effective strategy is developed by combining a flow-through reactor with a polytetrafluoroethylene (PTFE)-modified graphite felt cathode. In this design, anodic oxygen is directly used for efficient H2O2 generation at the modified cathode. Experimental results show that the modified cathode with the optimum PTFE content can produce 29.6 mg/L of H2O2, which is 16 times higher than the unmodified graphite felt cathode for a flow rate of 3 mL/min. Maximum H2O2 production, up to 30.7 mg/L, was obtained under the following conditions: 120 mA, 3 mL/min, initial pH 13, no external aeration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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