Polytetrafluoroethylene Tape Research Articles

Sealing the Screw Access Channel with Polytetrafluoroethylene Tape: Advantages of the Technique.

The aim of this article is to describe the procedure for sealing the screw access channel using plastic tape, polytetrafluoroethylene, in screw- or cement-retained implant-supported prostheses. This technique is viable and easily performed, and the functional and esthetic results are satisfactory.

Clinical applications of polytetrafluoroethylene (PTFE) tape in restorative dentistry.

Restorative dental procedures are ever developing; one reason for this can be attributed to newer materials with better handling properties and our ability to manipulate them more effectively. As a result various techniques have been described to aid clinicians in obtaining predictable results in restorative dental procedures. This article aims to review the use of plumber's tape to assist in adhesive, endodontic and implant related dental procedures, when compared to other available materials.

A prototype DC triboelectric generator for harvesting energy from natural environment

A prototype direct current Triboelectric Generator (DC-TEG) has been demonstrated to generate dc voltages by converting rotational mechanical energy into electrical energy. The generator primarily consists of four rotating wheels (two copper electrodes and two triboelectric wheels) utilizing polytetrafluoroethylene (PTFE) tape and nylon fabric as the triboelectric materials in its design. Once subjected to mechanical rotation, the interaction between the two triboelectric materials generates equal, but opposite charges and deposits them on the copper electrodes resulting in a dc voltage across an external load resistor. The power performance of the generator, with changes in angular frequency, has been measured. The DC-TEG can generate a dc voltage of about 1.5 mV across an external load of 15.14 kΩ at a rotational speed of 10 rev/sec. The dependences of current and power on the angular frequency have also been measured. Preliminary results suggest that the relationship between the dc voltage and angular frequency of rotation is quadratic, however further measurements at relatively higher angular frequencies are needed before a proper mathematical model may be established. The work here presents a new, cost-effective DC-TEG design for power scavenging from any naturally or artificially occurring rotational mechanical motion facilitated by either wind or flowing water for self-powered systems.

A modified implant for upper eyelid ptosis correction in frontalis suspension surgery

to develop a modified implant to correct ptosis through brow suspension and to evaluate its effectiveness. The clinical group consisted of 20 patients (29 eyes) aged 23 to 69 years (45±5.3 years on the average) and the comparison group - of 20 patients (33 eyes) aged 19 to 77 years (47±9.5 years on the average). All patients were operated on for severe ptosis of the upper eyelid, which implied stitching their eyelids to the eyebrows. In the main group, an original implant was introduced as suspensory material - a 200 µm thick porous polytetrafluoroethylene tape, length 13 cm, width 6 mm, round staggered perforation pattern, 1.5 mm holes, 3.5 mm pitch. In the comparison group, Mersilene mesh strips were used. The article contains a detailed description of the surgical technique. Checkups were performed at 1, 6, and 12 months. Follow-up periods were up to 4 years (1.7 years on the average) in the main group and up to 7 years (5.1 years on the average) - in the controls. Were evaluated by the width of the palpebral fissure at raised eyebrows, marginal reflex distance (MRD, which is the distance between the center of the pupil and the upper eyelid margin), presence and depth of the upper eyelid crease, and residual lagophthalmos. Examinations held at months 1, 6, and 12 after surgery showed that the results were positive and stable in all cases. Neither signs of recurrence, nor statistically significant differences between the groups were found. The use of the original modified implant during frontalis suspension surgery provides high and stable cosmetic result and expands the possibilities of ophthalmic plastic surgery.

Characterization of Adsorbed Molecular Water on the Surface of a Stretched Polytetrafluoroethylene Tape Analyzed by (1)H NMR.

A single molecule often exhibits a largely different material character from a bulk matter. Although a perfluoroalkyl (Rf) compound is a representative one, many interests have mostly been devoted to the bulk character only thus far, leaving the single molecular character unclear. Recently, a new theoretical framework, stratified dipole-arrays (SDA) theory, has appeared for comprehensive understanding of Rf compounds in terms of both single and bulk systems. On this theory, a mechanically stretched polytetrafluoroethylene (PTFE) is expected to exhibit a single-molecular character having dipole-driven properties, which should attract molecular water. In the present study, a stretched PTFE tape is revealed to attract molecular water (not water droplet) in fact, and the adsorbed water molecules are highly restricted in motion by the dipole-dipole interaction studied by using (1)H NMR, which agrees with the prediction by the SDA theory.

Different sealing materials preventing the microbial leakage into the screw-retained implant restorations: an invitro analysis by DNA checkerboard hybridization.

The aim of this controlled invitro study was to identify and quantify up to 38 microbial species penetrating through the screw-retained implant prostheses with different sealing materials. Sixty morse cone implants were restored with single-unit screw-retained prostheses. All the components were randomly divided into five groups (n=12) according to the proposed materials: (1) polytetrafluoroethylene tape+composite resin; (2) polytetrafluoroethylene tape+gutta-percha; (3) polytetrafluoroethylene tape+light-polymerized provisional composite; (4) cotton pellet+gutta-percha; and (5) cotton pellet+light-polymerized provisional composite. Human saliva was used as contaminant media, and DNA checkerboard hybridization was used to identify and quantify microbial species. Microbial leakage was observed in all groups: M.salivarium, S.pasteuri, P.nigrescens, and P.melaninogenica were the species presenting the highest values of genome count, prevalence, and proportion within the groups. The total microbial mean counts (×105 , ±SD) were as follows: Group 1 (2.81±0.38), Group 2 (3.41±0.38), Group 3 (6.02±1.48), Group 4 (6.40±1.42), and Group 5 (17.45±1.67). Group 5 showed the higher microbial counts (P<0.001). Moderate to high counts of pathogenic/nonpathogenic species were detected in the inner parts of implants from all groups. The lowest values of microbial counts were recorded for polytetrafluoroethylene tape associated with composite resin or gutta-percha; cotton pellet associated with light-polymerized provisional composite presented the highest microbial counts.

Efficacy of Gutta-Percha and Polytetrafluoroethylene Tape to Microbiologically Seal the Screw Access Channel of Different Prosthetic Implant Abutments.

To evaluate in vitro, the efficacy of gutta-percha (GP) and polytetrafluoroethylene (PTFE) tape to act as a seal against the penetration of Escherichia coli through prosthetic implant abutments (PIA) with external hexagon (EH) and morse taper (MT) connections. 120 sets of implant analogs with their respective PIA were used. 60 sets from each system were divided into four groups (n = 15): I - GP sealing; II - PTFE tape sealing; III - no sealing (NS) and IV - negative control. Microbiological challenge was performed by placing bacterial colonies inside the titanium PIA before screwing them into their respective analogs. Each set was immersed in 5 mL of BHI and incubated for 14 days with daily checks for contamination, according to the nutrient medium turbidity. The type of seal used influenced microbial penetration at all evaluation times (p < 0.05). Compared to GP, PTFE led to an increase in turbidity and its effectiveness against microbial penetration was equivalent to group NS. When the sealing efficacy of each group was compared in terms of time, Cochran's Q test revealed that in the two groups sealed with PTFE, there was a progressive increase in the number of turbid nutrient media (p < 0.0001), while in the group sealed with GP, this was only observed in the MT system (p = 0.0310). Sealing the PIA channel with GP was a significantly superior approach to sealing it with PTFE tape. PTFE tape or NS led to a progressive increase in microbiological leakage over time in PIA channels, however, this only occurred with GP in the MT system.

A Comparative Evaluation of Chemically Activated, Lightactivated and Laser-activated Tooth Bleaching Systems on Whitening Efficacy and Effect on Enamel Surface Texture: An in vitro Study

ABSTRACTBackgroundTooth bleaching systems can be classified as chemically activated, light-activated and laser-activated depending on activation mechanism. There is no unanimity of opinion with respect to the whitening efficacy and effect on enamel surface texture of these three types of systems. So, the present study was carried out to comparatively evaluate their whitening efficacy and effect on enamel surface texture.Materials and MethodsThirty-three extracted human anterior teeth were stained using coffee decoction for 7 days. Pre-bleaching color was evaluated with VITAPAN classical shade guide and a spectrophotometer. Samples were divided in three groups of 11 each namely: group I—chemically activated, group II— light activated, group III—laser activated. Post-bleaching color was evaluated with the same previous methods and difference in color pre- and postbleaching, dE, was calculated. Three samples, one per group, were subjected to scanning electron microscopic (SEM) evaluation both pre- and post-bleaching to study effect on enamel surface texture. Half the labial surface of these samples was covered using polytetrafluoroethylene tape so that half the surface was bleached and remaining half was unbleached acted at control. Photomicrographs were obtained pre- and post-bleaching.ResultsClinically, improvement of color was observed in all three groups. On statistical analysis, there was significant difference in dE between group II and III. On SEM evaluation, laser activation produced minimal effects on enamel surface texture.ConclusionsIt was found that laser activated system was more effective in terms of whitening efficacy and it produced least effect on enamel surface texture.How to cite this articleSabnis AC, Ram SM. A Comparative Evaluation of Chemically Activated, Light-activated and Laseractivated Tooth Bleaching Systems on Whitening Efficacy and Effect on Enamel Surface Texture: An in vitro Study. J Contemp Dent 2015;5(2):69-75.

Manufacturing of REBCO coils strongly bonded to cooling members with epoxy resin aimed at its application to Maglev

The REBCO coated conductor has been attracted attention because of its high current density in the presence of high magnetic field. If the coated conductor is applied to Maglev, the operational temperature of the on-board magnets will be over 40K and energy consumption of cryocoolers will be reduced. That high operational temperature also means the absence of liquid helium. Therefore, reliable thermal coupling is desirable for cooling the coils. We propose an epoxy impregnated REBCO coil co-wound with PTFE tape. While the PTFE tape prevents the performance degradation of the coil, the epoxy resin bonds the coil to cooling members.We carried out three experiments to confirm that the coil structure which we propose has robust thermal coupling without the degradation. First, thermal resistances of paraffin and epoxy were measured varying the temperature from room temperature to 10K. The measurement result indicates that paraffin has a risk of losing thermal coupling during cooling down. In another experiment, PTFE (polytetrafluoroethylene) tape insulator prevented performance degradation of a small epoxy impregnated REBCO coil, while another REBCO coil with polyimide tape showed clear performance degradation. Finally, we produced a racetrack REBCO coil with the same outer dimension as a Maglev on-board magnet coil. Although the racetrack coil was installed in a GFRP coil case and tightly bonded to the case by epoxy impregnation, any performance degradation was not observed.

A technique to eliminate subgingival cement adhesion to implant abutments by using polytetrafluoroethylene tape

Residual excess cement adhered subgingivally to an implant abutment has the potential to cause periimplant mucositis or periimplant disease. This article describes a procedure in which polytetrafluoroethylene (PTFE) tape is used to protect dental cements from adhering to the implant abutment. This technique ensures complete removal of cement from the implant abutment after seating of the crown.

Effect of screw access channel filling materials on uniaxial retentive force of cement‐retained implant restorations

This study aimed to investigate the effect of various abutment screw access channel filling materials on the uniaxial retention of castings cemented onto the abutment using temporary cement. Ten straight, regular platform Esthetic Abutments were used. Fifty castings were divided into five groups and the abutment screw access channels were filled with composite resin (Filtek Z 250), light-cured temporary filling (Clip), temporary filling (Coltosol), polyvinyl siloxane impression material (Elite H-D), or polytetrafluoroethylene (PTFE) tape. Castings were cemented and thermal cycled. A uniaxial tensile force with a cross-head speed of 5 mm/min, was applied to the castings until cement failure occurred. One-way analysis of variance was used to perform intergroup comparisons of the mean uniaxial retentive force (URF) values and Tukey's HSD test was used to determine the group causing the difference. There were statistically significant differences between the mean URF values for the groups (p < 0.01). The mean URF value for the composite resin group was statistically higher than those for the other filling material groups respectively (p < 0.05). The retention of castings cemented to straight implant abutments using non-eugenol temporary cement may be influenced by the screw access channel filling material.

Ammonia Volatilization from Soil, Dry-Matter Yield, and Nitrogen Levels of Italian Ryegrass

Nitrogen (N) loss by ammonia (NH3) volatilization is the main factor for poor efficiency of urea fertilizer applied to the soil surface. Losses can be suppressed by addition of zeolite minerals to urea fertilizer. The objective of this study was to evaluate ammonia volatilization from soil and dry-matter yield and nitrogen levels of Italian ryegrass. A greenhouse experiment was carried out with the treatments of urea, urea incorporated into soil, urea + urease inhibitor, urea + zeolite, ammonium nitrate, and unfertilized treatment. Ammonia was captured by a foam absorber with a polytetrafluoroethylene tape. There were few differences between zeolite and urease inhibitor amendments concerning NH3 volatilization from urea. Results indicate that zeolite minerals have the potential to improve the N-use efficiency and contributed to increasing N uptake. Zeolite and urea mixture reduced 50% the losses by volatilization observed with urea.

NiCo2O4 nanowire arrays supported on Ni foam for high-performance flexible all-solid-state supercapacitors

Portable electronic devices which are ultrathin, lightweight and even able to roll-up have attracted much attention. Herein, we report the design of flexible all-solid-state symmetric supercapacitors by using two NiCo2O4 nanowire arrays supported on Ni foams as the electrodes. The as-fabricated symmetric supercapacitors have excellent electrochemical performance with a high cell areal capacitance of 161 mF cm−2 at 1 mA cm−2. Good electrochemical performance stability over 3000 cycles was obtained even when the device was under harsh mechanical conditions including both twisted and bent states. As-fabricated all-solid-state supercapacitors could be charged and power a commercial light-emitting-diode, demonstrating their feasibility as an efficient energy storage component and self-powered micro/nano-system. In addition, we were able to grow NiCo2O4 nanowire arrays on many kinds of flexible substrates, including nickel foam, carbon cloth, Ti foil and polytetrafluoroethylene tape. Our work here opens up opportunities for the device configuration for energy-storage devices in the future wearable electronic area and many other flexible, lightweight and high performance functional nanoscale devices.

Effects of thermal aging on morphology, resistivity, and thermal properties of extruded high‐density polyethylene/carbon black heating elements

AbstractVarious output heating elements were extruded with carbon black (CB)‐filled high‐density polyethylene (HDPE) composites. After thermal aging near melting point of HDPE, the effects of thermal aging on the morphology, resistivity, and thermal properties of the extruded and electron beam (EB)‐irradiated heating elements were examined using scanning electron microscopy (SEM) megohmmeter and differential scanning calorimetry, respectively. The heating element was insulated with a polytetrafluoroethylene tape wrap. The SEM image of HDPE is covered with microvoids that leave a dimple‐like structure on the surface. As the percolation threshold is achieved, CB aggregates are usually located in oval cavities larger than the particles themselves. During the resistivity–temperature cycling test, significant change in resistivity was observed for extruded and EB‐irradiated heaters. In case of thermal‐aged samples at 140°C for 120 h, both heaters showed good stability without pronounced changes in resistivity after resistivity–temperature cycling test. After thermal aged at 140°C for 120 h, the Heater02‐EB composite recovered the oval cavity structure, whereas for Heater02, the amorphous region became narrower and formed a more electroconductive pathway. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Linearity of the instrumental intensity scale in TOF‐SIMS—a VAMAS interlaboratory study

AbstractA VAMAS interlaboratory study involving 21 time‐of‐flight SIMS instruments from nine countries has been conducted to evaluate the linearity of the instrumental intensity scale and procedures for intensity correction. Analysts were supplied, by National Physical Laboratory (NPL), with a protocol for analysis (closely aligned with ISO 23830) together with a reference material of polytetrafluoroethylene (PTFE) tape. The primary ion beam current is varied to provide secondary ion intensities that span the linear to nonlinear regime. The natural carbon isotope ratios 12CxFy+/13C12Cx−1Fy+ for five peaks are used to evaluate the linearity, without a need to measure the ion beam current. A method is given for determining the linearity as a function of secondary ion intensity, with and without dead time correction. It is found that single ion counting statistics is closely obeyed, and the linearity achievable is generally excellent with careful application of dead time correction. Three quarters of instruments in the study achieved better than 95% linearity at a count rate of 0.8 measured counts per pulse, equivalent to 1.6 secondary ions impinging the detector per primary ion pulse. We discuss factors affecting linearity and the precise application of dead time correction and give guidance for practical analysis. This includes suboptimal detector efficiency, inhomogeneous intensities across the rastered area, inadequate charge compensation, and the choice of peak integration limits. The interlaboratory study shows that the method to determine linearity is generally applicable, robust and provides an excellent basis for the development of an ISO standard. © Crown copyright 2011. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley &amp; Sons, Ltd.

The use of polytetrafluoroethylene tape for the management of screw access channels in implant-supported prostheses

This article describes a procedure in which polytetrafluoroethylene (PTFE) tape is used to seal the screw access channel to protect the screw head of the abutment and crown screw in implant-supported restorations. The material can be sterilized, is easy to manipulate, radiopaque, and less associated with malodor when retrieved. Malodor is primarily associated with the implant-abutment interface configuration and the suprastructure component design of a given implant system. This technique enables fast removal of the filling material in a single piece, preventing unpredictable and time-consuming manipulations when removal of the screw-retained crown or abutment is required.

Optical Reflectance Measurements for Commonly Used Reflectors

When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> , and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> :1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

Price and the efficacy of the polytetrafluoroethylene (PTFE) tape for the removal of the proximal dental biofilm compared to the common nylon dental floss in adolescents and young adults.

Objective: To identify the price and the efficacy of the polytetrafluoroethylene PTFE tape as an oral hygiene method for the removal of the proximal dental biofilm, compared to the common nylon dental floss in adolescents and young adults. Methods: The polytetrafluoroethylene tape was used as a method for the removal of the proximal dental biofilm. By a randomized procedure the sample size was of 87 (31 men and 56 women) between 16 and 28 years old. The oral hygiene of the participants was suspended during a period of 12 hours. A suitable disclosing solution was used to paint the dental surfaces. The removal of the biofilm was made by the same operator who used the same technique with the two materials (polytetrafluoroethylene tape and nylon dental floss). The information was collected using the coronal division (in thirds) of the Greene and Vermillion Oral Hygiene Index. This index was modified to evaluate proximal surfaces only. Results: In the group of dental floss the presence of the proximal biofilm was 72.6% before and 11.2% after its removal. In the group of PTFE was 72.9% before and 11% after. After the comparison of the two methods the differences are not significant. PTFE price is 2.7 times lower than common nylon dental floss. Conclusions: The similarity in the removal of the proximal biofilm of the PTFE tape when compared to the nylon floss was significant. Thanks to its biocompatibility, tolerance and its low price, the PTFE tape is an alternative method for the removal of the biofilm in these proximal areas. Results of this study open a way for the investigation on non orthodox techniques, but effective, for the maintenance of the oral health with the only purpose of improving life quality of poor populations.

Superdrawing of polytetrafluoroethylene nascent powder by solid-state coextrusion

A film of nascent powder of polytetrafluoroethylene (PTFE), compacted below the ambient melting temperature (Tm, 335 °C), was drawn by two-stage draw techniques consisting of a first-stage solid-state coextrusion followed by a second-stage solid-state coextrusion or tensile draw. Although the ductility of extrudates was lost for the second-stage tensile draw at temperatures above 150 °C due to the rapid decrease in strength, as previously reported, the ductility of extrudates increased with temperature even above 150 °C when the second-stage draw was made by solid-state coextrusion, reflecting the different deformation flow fields in a free space for the former and in an extrusion die for the latter. Thus, a powder film initially coextruded to a low extrusion draw ratio (EDR) of 6–20 at 325 °C was further drawn by coextrusion to EDRs up to ∼︁400 at 325–340 °C, near the Tm. Extremely high chain orientation (fc = 0.998 ± 0.001), crystallinity (96.5 ± 0.5)%, and tensile modulus (115 ± 5 GPa at 24 °C, corresponding to 73% of the X-ray crystal modulus) were achieved at high EDRs. Despite such a morphological perfection and a high modulus, the tensile strength of a superdrawn tape, 0.48 ± 0.03 GPa, was significantly low when compared with those (1.4–2.3 GPa) previously reported by tensile drawing above the Tm. Such a low strength of a superdrawn, high-modulus PTFE tape was ascribed to the low intermolecular interaction of PTFE and the lack of intercrystalline links along the fiber axis, reflecting the initial chain-extended morphology of the nascent powder combined with the fairly high chain mobility associated with the crystal/crystal transitions at around room temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3369–3377, 2006

Lutetium oxyorthosilicate block detector readout by avalanche photodiode arrays for high resolution animal PET

Avalanche photodiodes (APDs) have proven to be useful as light detectors for high resolution positron emission tomography (PET). Their compactness makes these devices excellent candidates for replacing bulky photomultiplier tubes (PMTs) in PET systems where space limitations are an issue. The readout of densely packed, 10 × 10 lutetium oxyorthosilicate (LSO) block detectors (crystal size 2.0 × 2.0 × 12 mm3) with custom-built monolithic 3 × 3 APD arrays was investigated. The APDs had a 5 × 5 mm2 active surface and were arranged on a 6.25 mm pitch. The dead space on the edges of the array was 1.25 mm. The APDs were operated at a bias voltage of approximately 380 V for a gain of 100 and a dark current of 10 nA per APD. The standard deviation in gain between the APDs in the array ranged from 1.8 to 6.5% as the gain was varied from 50 to 108. A fast, low-noise, multi-channel charge sensitive preamplifier application-specific integrated circuit (ASIC) was developed for the APD readout. The amplifier had a rise time of 8 ns, a noise floor of 515 e− rms and a 9 e− pF−1 noise slope. An acquired flood image showed that all 100 crystals from the block detector could be resolved. Timing measurements with single-channel LSO-APD detectors, as well as with the array, against a plastic scintillator and PMT assembly showed a time resolution of 1.2 ns and 2.5 ns, respectively. The energy resolution measured with a single 4.0 × 4.0 × 10 mm3 LSO crystal, wrapped in four-layer polytetrafluoroethylene (PTFE) tape and coupled with optical grease on a single APD of the array, yielded 15% (full width at half maximum, FWHM) at 511 keV. Stability tests over 9 months of operation showed that the APD arrays do not degrade appreciably. These results demonstrate the ability to decode densely packed LSO scintillation blocks with compact APD arrays. The good timing and energy resolution makes these detectors suitable for high resolution PET.