Push-out Technique Research Articles

The effect of sisal (Agave Sisalana) nanofiber in epoxy resin sealer on root canal obturation’s push-out bond strength

Sisal nanofiber can be used as an additional filler to increase the adhesion strength of the resin epoxy sealer. The aim of this study was to observe the effect of sisal nanofiber addition to epoxy resin sealer on push-out bond strength of root canal obturation material against the root canals. Twenty-five mandibular premolars (n= 25) were prepared until file F3 and obturated using 0%, 0.25%, 0.5%, 0.75%, and 1% sisal nanofiber sealer. After the specimens were stored at incubator, they were horizontally sectioned at apical third. Root sections were tested with push-out technique, and observed under a stereo microscope to determine the failure type. Data were analyzed with one-way ANOVA and LSD pos hoc at 95% confidence level (α=0.05). A one-way ANOVA test revealed that the addition of sisal nanofiber in epoxy resin sealer had a significant effect on the push out bond strength of the obturation material against the root canals. The failure type was observed predominantly in the cohesive type and the lowest in the adhesive type. The addition of sisal nanofiber to the epoxy resin sealer could increase the push-out bond strength of the obturation material against the root canals. Epoxy resin sealers with the addition of sisal nanofiber at a concentration group of 0.75% resulted in the highest push-out strength of root canal obturation materials followed by 0.5% concentration group.

Investigation of interface debonding behaviour in a unidirectional SiC fibre reinforced Ti-17 composite by a single fibre push-out technique

The debonding behaviour at the fibre/matrix interface in a unidirectional continuous carbon-coated SiC fibre reinforced Ti-17 composite was investigated. Single fibre push-out testing on thin slice specimen by micro-indentation was employed to evaluate the interface debonding strength. In order to investigate interface debonding modes, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilised to observe the microstructure at the fibre/matrix interface region after the fibres were pushed out. It is found that the interface debonding strength is evaluated to be 108.2 MPa in the composite. The interface debonding occurs at the interface between the interface reaction zone (RZ) and the carbon coating on the fibre surface. The carbon coating/SiC fibre interface and the RZ/matrix interface remain intact after the fibre was pushed out.

Time-Dependent Effect of Chitosan Nanoparticles as Final Irrigation on the Apical Sealing Ability and Push-Out Bond Strength of Root Canal Obturation.

Materials and Methods Fifty-six premolars were used in this study and divided by two evaluations: 28 teeth for apical sealing ability and 28 others for bond strength. Each study was assigned randomly into two groups of fourteen teeth: Group-1, final irrigation with 17% EDTA; Group-2, with 0.5% chitosan nanoparticles. Each group was further divided into two groups of 7 each: Group-A, final irrigation was applied for 1 minute; Group-B, for 3 minutes. All teeth were obturated with epoxy resin-based sealer and gutta-percha. In the apical sealing ability study, the obturated teeth were immersed in 2% methylene blue and observed under a stereomicroscope (8x magnification). In the bond strength study, the teeth were tested using the push-out technique and observed under a stereomicroscope (40x magnification) to determine the failure type. Data from each evaluation were analysed with two-way ANOVA followed by the LSD test. Results Final irrigation using 0.5% chitosan nanoparticles produced the same apical sealing ability and bond strength as 17% EDTA (p > 0.05). A significant difference occurred between application times (p < 0.05). The failure type was observed predominantly as cohesive, and the least was adhesive. Conclusion Regardless of the final irrigation solution used, 3-minute application time produced greater apical sealing ability and push-out bond strength than 1-minute application time.

Reconstruction of Medial Orbital Wall Fractures without Subperiosteal Dissection: The "Push-Out" Technique.

BackgroundVarious surgical methods for repairing medial orbital wall fractures have been introduced. The conventional technique requires total separation of the displaced orbital bones from the orbital soft tissues. However, subperiosteal dissection around the fracture can cause additional damage. The aim of the present study is to introduce a method of reconstructing medial orbital wall fractures without subperiosteal dissection named the “push-out” technique.MethodsSix patients with post-traumatic enophthalmos resulting from an old medial orbital wall fracture and 10 patients with an acute medial orbital wall fracture were included. All were treated with the push-out technique. Postoperative computed tomography (CT) was performed to assess the correct positioning of the implants. The Hertel scale and a comparison between preoperative and postoperative orbital volume were used to assess the surgical results.ResultsRestoration of the normal orbital cavity shape was confirmed by examining the postoperative CT scans. In the old fracture group, the median orbital volume of the fractured side was 29.22 cm3 preoperatively, and significantly improved postoperatively to a value of 25.13 cm3. In the acute fracture group, the median orbital volume of the fractured side was 28.73 cm3 preoperatively, and significantly improved postoperatively to a value of 24.90 cm3. Differences on the Hertel scale also improved, from 2.13 mm preoperatively to 0.25 mm postoperatively in the old fracture group and from 1.67 mm preoperatively to 0.33 mm postoperatively in the acute fracture group.ConclusionsThe push-out technique can be considered a good alternative choice for old medial orbital wall fractures with posttraumatic enophthalmos, acute medial orbital wall fractures including large fractured bone segments, and single-hinged greenstick fractures.

A technique for extraction of the distal segment of a broken femoral nail using a flexible reamer

IntroductionExtraction of broken femoral nails in peri-implant fractures is becoming an increasingly common problem faced by orthopaedic surgeons. Different closed and open techniques for removal of broken nails have been previously described but due to variations in equipment and fracture configurations these methods are not always easily reproducible. We describe an open surgical technique using simple equipment that can be utilised when other methods of extraction have failed. Case presentation and surgical techniqueWe present a case of a peri-implant fracture secondary to non-union involving a short cephalomedullary nail where the broken distal segment of nail was significantly more distal to the femoral fracture site. After multiple failed attempts at extraction with previously described closed techniques a rectangular cortical window was created 2cm distal to the tip of the broken nail using a saw. An antegrade guide wire was passed through the nail and pulled out of the bony window. A flexible intramedullary reamer was subsequently passed in retrograde fashion over the guide wire and a simple pushout technique was used to push both segments of the broken nail through the original insertion site. An exchange nailing was performed and the cortical window was reattached using a cable. DiscussionThis is a simple technique that does not require any specialist equipment and does not require the fracture site to be disturbed. The use of a flexible reamer as a pushout device is ideal as there are multiple size options allowing the surgeon to match the size of the medullary canal with the reamer. Furthermore, the flexibility of the reamer allows easy access through a lateral bone window. ConclusionBroken femoral nail extraction can be technically challenging and when other closed methods have failed we believe our technique offers a simple alternative that can be added to the armamentarium of solutions.

Atomic \u201cbomb testing\u201d: the Elitzur\u2013Vaidman experiment violates the Leggett\u2013Garg inequality

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the “bomb test” with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett–Garg inequality—a quantitative criterion fulfilled by macro-realistic physical theories. To perform interaction-free measurements, we have implemented a novel measurement method that correlates spin and position of the atom. This method, which quantum mechanically entangles spin and position, finds general application for spin measurements, thereby avoiding the shortcomings inherent in the widely used push-out technique. Allowing decoherence to dominate the evolution of our system causes a transition from quantum to classical behavior in fulfillment of the Leggett–Garg inequality.

Evaluation of Setting Time, Ions Release, Sealing Ability and Adhesion of a Novel Experimental Endodontic Cement

The aim of this work was to evaluate the setting time, adhesion, sealing ability, and ion release of a novel endodontic sealer (CEOE) and of the commercial Sealer 26® cement. The setting time was determined in accordance with ANSI/ADA specifications #57. The adhesion of the materials to the canal walls was evaluated through bond strength using the push-out technique. The sealing ability was assessed by fluid filtration measurements. The released ions of interest to be analyzed are OH1- and Ca2+. The concentration of hydroxyl and calcium ions was evaluated by pH measurements and atomic absorption spectroscopy technique, respectively. The data were analyzed statistically using the analysis of variance and the Tukey’s test. The results obtained showed that the setting time of CEOE cement is 35% shorter than of Sealer 26® and both cements meet the British Standard BS (1988) recommendation. No significant difference was observed in the bonding strength and permeability values for both cements. Statistically, the CEOE released more hydroxyl ions than Sealer 26® in the first 72 h, and more calcium ions in the first 48 h.

New Graft Inserter for Descemet Stripping Automated Endothelial Keratoplasty

The aim of this study was to introduce a newly developed graft inserter for Descemet stripping automated endothelial keratoplasty, which can be readily used with 1 hand, and to examine endothelial cell loss (ECL) after graft insertion using this new inserter in an ex vivo rabbit model. Rabbit corneal grafts (∼150 μm) were prepared by using a femtosecond laser. The grafts were inserted into an artificial anterior chamber by the pull-through technique using a Busin glide or the push-out technique using our new inserter. ECL was evaluated by means of trypan blue and alizarin red S staining. Grafts that were not injected served as a control group. The mean percentages of ECL area in the control, Busin glide, and new inserter groups were 18.7 ± 1.79%, 25.4 ± 2.32%, and 24.7 ± 1.56%, respectively. The mean percentages of the ECL area in both the Busin glide group and new inserter groups were significantly greater than that in the control group (P = 0.001). There was no statistically significant difference between the Busin glide group and the new inserter group. Our new inserter may provide a favorable option for donor tissue insertion in Descemet stripping automated endothelial keratoplasty procedures.

Wettability and bonding of self-etching dental adhesives: Influence of the smear layer

Objectives To evaluate dentin wettability and bonding of self-etching and total-etch adhesives on smear layer-covered and smear layer-free dentin. Methods Three self-etching adhesives (Clearfil SE Bond, AdheSE and Xeno III) and one total-etch adhesive (SingleBond) were evaluated. The substrates were mid coronal smear layer-covered and smear layer-free dentin. Dentin wettability by resins was studied from contact angle measurement using sessile drop method and Axisymmetric Drop Shape Analysis (ADSA). Shear-bond strength was evaluated using a push-out technique (ad hoc design). Data were analysed with two-way ANOVA and Tukey's test. Results Similar values of dentin wettability were obtained for all adhesives tested regardless the presence of smear layer. Even though, Xeno III and AdheSE exhibited slightly lower wettability (higher contact angles values) on smear layer-free dentin. Likewise, the presence of smear layer did not affect the shear-bond strength. Total-etch adhesive obtained higher shear-bond strength than self-etching adhesives, which obtained similar values. Significance Wettability is similar between self-etching and total-etch adhesives. The smear layer affects slightly the wettability of self-etching adhesives. Shear-bond strength is not sensitive to the smear layer presence. Total-etch adhesion is stronger than self-etching adhesion. There is no clear relationship between wettability and bond strength.

Evaluation of interfacial mechanical properties under shear loading in EB-PVD TBCs by the pushout method

A new simple pushout technique for evaluation of interfacial shear mechanical properties in thermal barrier coatings has been developed. The technique is similar to the pushout test of fiber-reinforced ceramics, except for the specimen shape and support method. The technique has been applied to evaluation of interfacial delamination toughness, Γ i , of the electron beam physical vapor deposition (EB-PVD) ZrO 2 thermal barrier coating (TBC) system. The change of Γ i in the EB-PVD system with thermal exposure is measured and discussed in terms of microstructural change and delamination crack path. The measured delamination toughness varied from Γ i = 10 to 115 J/m 2. The delamination path and TGO growth were found to be closely related. The delamination toughness significantly decreases due to the formation and growth of a spinel phase in the TGO layer. The relation between delamination toughness and delamination behavior is discussed.

Determining the shear properties of the PyC/SiC interface for a model TRISO fuel

The fracture behavior of TRISO-coated fuel particles is dependent on the shear strength of the interface between the inner pyrolytic carbon (PyC) and silicon carbide coatings. This study evaluates the interfacial shear properties and the crack extension mechanism for TRISO-coated model tubes using a push-out technique. The interfacial debond shear strength was found to increase with increasing sample thickness and finally approached a constant value. The intrinsic interfacial debond shear strength of ∼280 MPa was estimated. After the layer is debonded, the applied load is primarily transferred by interfacial friction. A non-linear shear-lag model predicts that the residual clamping stress at the interface is ∼350 MPa, and the coefficient of friction is ∼0.23, yielding a frictional stress of ∼80 MPa. These relatively high values are attributed to the interfacial roughness. Of importance in these findings is that this unusually high interfacial strength could allow significant loads to be transferred between the inner PyC and SiC in application, potentially leading to failure of the SiC layer.

Carbon-Coated-Glass-Fiber-Reinforced Cement Composites: I, Fiber Pushout and Interfacial Properties

Interfacial mechanical properties of carbon-coated-S-glass-fiber-reinforced cement were characterized by a fiber pushout technique. The pushout experiments were conducted on model composites, where the S-glass monofilaments with and without carbon coating were unidirectionally embedded in ordinary portland cement. Interfacial properties, including bonding strength, frictional stress, residual stress, and fracture energy, were extracted from the previously developed progressive debonding model. The composite with a carbon interface exhibited a weaker interfacial bonding strength and frictional stress than did the composite without a carbon interface. The interfacial fracture energy of the composite with a carbon interface was 7.9 J/m{sup 2}, as compared to 47.6 J/m{sup 2} for the composite without a carbon interface. The composite with the carbon interface exhibited a smaller residual clamping stress (18 MPa), in comparison to that for the composite without a carbon interface (69 MPa). Scanning electron microscopy observations indicated that the filament without a carbon coating was significantly attacked by the alkaline environment and was strongly bonded onto the matrix, whereas the filament with a carbon coating remained intact under the same curing conditions. These studies suggest that carbon coating provides the glass fiber with significantly improved corrosion resistance to alkali in the cement environment.

INVENTORY PROCESSES: QUASI-REGENERATIVE PROPERTY, PERFORMANCE EVALUATION, AND SENSITIVITY ESTIMATION VIA SIMULATION

We consider a single-commodity, discrete-time, multiperiod (s, S)-policy inventory model with backlog. The cost function may contain holding, shortage, and fixed ordering costs. Holding and shortage costs may be nonlinear. We show that the resulting inventory process is quasi-regenerative, i.e., admits a cycle decomposition and indicates how to estimate the performance by Monte Carlo simulation. By using a conditioning method, the push-out technique, and the change-of-measure method, estimates of the whole response surface (i.e., the steady-state performance in dependence of the parameters s and S) and its derivatives can be found. Estimates for the optimal (s, S) policy can be calculated then by numerical optimization.

Bond strength measurement between glass fibres and epoxy resin at elevated temperatures using the pull-out and push-out techniques

Pull-out and push-out measurements were performed on glass fibres in an epoxy resin to determine the dependence of bond strength on test temperature and on fibre surface treatment. A comparative analysis of the two techniques was carried out to elucidate elementary processes of polymer-fibre debonding and to determine energy values for adhesional bonds. Differences in bond strength values for pull-out and push-out tests were attributed to failure mechanisms that were either interface-controlled or matrix-controlled. Evidence for the different failure mechanisms characteristic of the two test techniques was provided by an estimation of failure parameters, such as the activation energy for debonding. Failure mechanisms also were manifest in AFM images, showing differences in topography and roughness that depended on fibre surface treatment, test geometry, and test temperature.

Characterisation of the Interfacial bond Strength between Glass Fibre and Epoxy Resin using the Pull-Out and Push-Out Techniques

Interfacial bond strength between epoxy resin and glass fibre was studied using the pull-out and push-out techniques. For untreated fibres, these micromechanical tests gave similar values of the local interfacial shear strength and critical energy release rate. In the case of fibres treated by γ-APS, both tests showed considerable increase in the bond strength. However, for the modified fibres, the pull-out test gave greater values of both interfacial parameters than the push-out test, a result attributed to the different modes of interfacial loading. The different loading patterns also cause different failure mechanisms in these two tests.

A technique for the determination of interfacial properties from debond length measurement

Fiber-matrix interfacial debonding is observed and the debond length is directly measured during flexure tests performed on transparent SiC fiber-reinforced borosilicate glass composites. The relationship among the debond length, applied stress, and interfacial properties is investigated both experimentally and theoretically. A new technique based on debond length measurement is introduced for measuring fiber-matrix interfacial properties such as interfacial shear strength, frictional shear stress, and interfacial debond energy. Analytical models are employed for the new technique to interpret the experimental data. Fiber pushout technique is also employed to measure the interfacial properties independently. It is shown that these two different techniques of debond length measurement and fiber pushout test for measuring the interfacial properties can provide comparable results.

Interfacial properties of SiC monofilament reinforced β′-SiAlON composites

Interfacial mechanical properties of SiC monofilament-reinforced β′-SiAlON composites were characterized by a single fiber push-out technique. Interfacial parameters were studied as a function of embedded filament lengths, including comparisons of linear, nonlinear shear-lag, and progressive debonding analysis models. The interfacial debonding peak load ( P p) and maximum frictional sliding load ( P max) were both measured from the apparent load-displacement curves. Linear and shear-lag analyses were fitted to the data as a function of embedded filament lengths, respectively. In comparison, the progressive debonding analysis was conducted by fitting the effective load-displacement curves obtained by subtraction of machine compliance from the apparent load-displacement curves. The nonlinear shear-lag model gave better regression fits to the data than did the linear model, while the progressive debonding model provided much more interfacial information than did the shear-lag model. In addition to the coefficient of friction (μ) and radial residual stress ( σ N), axial residual load ( P r), critical load for interfacial crack initiation or propagation ( P d), interfacial fracture toughness ( G i), as well as the interfacial roughness amplitude ( A) and its contribution to the interfacial normal stress ( σ r) were extracted from the progressive debonding model, using a three-parameter, non-linear least squares fitting method on the effective load-displacement curves.

Combustion-synthesized β′-SiAlON reinforced with SiC monofilaments

Dense composites of combustion-synthesized β′-Si 3Al 3O 3N 5 (β′-SiAlON) reinforced with 20 vol.% SiC monofilaments (AVCO SCS-6) were hot pressed at a temperature of 1600 °C for 2 h under a pressure of 34 MPa. The mechanical properties of as-fabricated composites were investigated in the three-point flexure mode. The composites exhibited significant improvement in the work of fracture as well as in the ultimate strength, in comparison with monolithic β′-SiAlON. Ultimate flexure strength values between 682 and 793 MPa for the composite and between 398 and 528 MPa for the monolithic β′-SiAlON were obtained. A work of fracture of 13–20 kJ m −2 was obtained for the composite, compared with 1.7-3.1 kJ m −2 for the monolithic material. Optical microscopy and scanning electron microscopy (SEM) examinations of the fractured specimens showed the usual composite toughening mechanisms of microcracking. interfacial debonding, filament bridging and pull-out. The interfacial shear strength as well as frictional stress were also investigated with a fiber push-out technique. The push-out load-deflection curves revealed a moderate interfacial bonding strength of 26 MPa and a frictional sliding stress of 24 MPa. Transmission electron microscopy interfacial characterization was correlated with SEM observation of the interfacial debonding site. It revealed the presence of definite but weak physical bonding between the outermost carbon-rich layer of the SiC filament and the matrix. It appeared that the filament and the matrix were compatible with each other both physically and chemically, despite the fact that the matrix contained 20 wt.%Al 2O 3 as a secondary phase.

Temperature dependence of interfacial shear strength inSCS-6 fibre reinforced Ti–24Al–11 Nb metal matrix composites

Experiments were carried out to study the temperature dependence of the interfacial shear strength in SCS-6 fibre reinforced Ti–24Al–11Nb (at.-%) composites. The fibre pushout technique was used with a diamond indenter and a high temperature microhardness tester. The interfacial shear strength was found to decrease with increasing temperature.MST/1893

Effect of Coating Thickness on Interfacial Shear Behavior of Zirconia-Coated Sapphire Fibers in a Polycrystalline Alumina Matrix

ABSTRACTThe effect of zirconia (ZrO2) interfacial coatings on the interfacial shear behavior in sapphire reinforced alumina was examined in this study. Zirconia coatings of thicknesses ranging from 0.15 to 1.45 μm were applied to single crystal sapphire (Saphikon) fibers using a particulate loaded sol dipping technique. After calcining at 1100°C in air, the coated fibers were incorporated into a polycrystalline alumina matrix via hot pressing. Interfacial shear strength and sliding behavior of the coated fibers was examined using thin-slice indentation fiber pushout and pushback techniques. In all cases, debonding and sliding occurred at the interface between the fibers and the coating. The coatings exhibited a dense microstructure and led to a higher interfacial shear strength (&gt; 240 MPa) and interfacial sliding stress (&gt;75 MPa) relative to previous studies on the effect of a porous interphase on interfacial properties [1]. The interfacial shear strength decreased with increasing fiber coating thickness (from 389 ± 59 to 241 ± 43 MPa for 0.15 to 1.45 μm thick coatings, respectively). Sliding behavior exhibited load modulation with increasing displacement during fiber sliding which is characteristic of fiber roughnessinduced “stick-slip”. No effect of fiber coating thickness on the interfacial sliding stress was observed for single pushout or pushback events. Heat treatment at 1550°C in air coarsened the fiber surface roughness, resulting in significantly higher interfacial shear strengths (&gt;30%) and interfacial sliding stresses (&gt;60%) relative to the coated fibers in an as-hot-pressed condition. Interfacial sliding resistance decreased significantly after the first sliding cycle. Evidence of substantial “stick-slip” behavior was eliminated from the load displacement plots after one pushout/pushback cycle; however, the pushback plots exhibited evidence of fiber reseating, followed by a decreasing trend in load with increasing displacement of the fiber back to the original position. These results directly support the interphase fragmentation scenario proposed for interface fatigue in ceramic composites.The high interfacial shear strengths and sliding stresses measured in this study, as well as the potentially strength degrading surface reconstruction observed on the coated fibers after hot pressing and heat treatment, indicate that dense zirconia coatings are not suitable candidates for optimizing composite toughness and strength in the sapphire fiber reinforced alumina system.