Effect Of Fabrication Techniques Research Articles

Effect of Fabrication Technique and Margin Design on the Marginal Fit of Interim Fixed Dental Prosthesis (An In-Vitro Study)

Effect of Fabrication Technique and Margin Design on the Marginal Fit of Interim Fixed Dental Prosthesis (An In-Vitro Study)

Effect of fabrication techniques on mechanical and microstructural behavior of AA7075/SiC/ZrC hybrid composite

Aluminum composites are highly sought-after in the industrial sector due to their improved mechanical properties compared to their parent metals. The choice of fabrication technique has a significant impact on the mechanical behavior of the composite. This study investigated the mechanical behavior of an optimized weight-fractioned AA7075/SiC/ZrC hybrid composite using different fabrication techniques. Stir casting, conventional sintering, and microwave sintering methods were employed to produce the composites. By optimizing the ball milling parameters, a uniform distribution of reinforcement particles was achieved throughout the matrix material. XRD, porosity, microstructural, and mechanical tests were conducted on all three composites to analyze the major changes during fabrication. Remarkably, the composites fabricated through microwave sintering exhibited significantly higher strength than the other fabrication methods. Specifically, the microwave-sintered composites displayed a compressive strength of 389 MPa, a tensile strength of 321 MPa, and a strain-to-fracture value of 26%. In contrast, the stir-cast composites showed a larger scale of secondary phases, poor mechanical performance, and elevated porosity. Moreover, when considering the overall production cost associated with the different fabrication techniques investigated in this study, microwave sintering was the most cost-effective method for large-scale production. This suggests that microwave sintering offers superior mechanical properties and economic advantages regarding manufacturing expenses.

Effect of fabrication technique on membrane distillation performance of photothermal membrane: Electrospinning vs electrospraying

Membrane distillation (MD) is widely applied to desalination and wastewater treatment processes owing to its low operating pressure, superior rejection efficiency, and low membrane fouling. However, in addition to membrane fouling, MD suffers from temperature polarization (TP). In this study, gold nanoparticles (GNPs) were embedded in MD membranes to improve MD performance through the photothermal effect. Two different techniques (electrospinning and electrospraying) were used to fabricate the photothermal layer and systemically compared. Surface layers with different structures were formed. When irradiated with a continuous 808 nm laser (2 W), the TP coefficient ratios of the two different GNP/PVDF membranes obtained using electrospinning (5.7–8.0 %) and electrospraying (8.2–9.9 %) were higher than that of the virgin PVDF membrane (1.1–3.1 %). Furthermore, with laser irradiation, the organic fouling factors of the GNP-PVDF membranes fabricated via electrospinning and electrospraying decreased from 12.1 ± 3.4 to 9.2 ± 1.4 % and from 48.8 ± 0.5 to 18.3 ± 3.4 %, respectively. Therefore, this study provides a guideline for selecting the appropriate technique for fabricating the photothermal layer on electrospun photothermal MD membranes.

Effects of Fabrication Techniques and Durability Performance on Resistance of Fibre-based PEDOT:PSS/GO pH Sweat Sensor

Most wearable electronics widely incorporate metal electrodes for parameter detection but these electrodes possess drawbacks due to corrosion and performance degradation. Therefore, in this work, pH sweat sensor is fabricated by using highly conductive, stable and non-toxic PEDOT:PSS/GO nanocomposite on flexible cotton fibre substrate. This work is aimed to determine the effects of fabrication techniques and durability performance on pH sensitivity of fibre-based PEDOT:PSS/GO sensor via resistance measurements. In this work, a wearable fibre-based sensor is developed by using Poly (3,4 ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), and Graphene Oxide (GO) nanocomposite. Sample characterisations are completed by analysing absorbance spectrums, FESEM images and XRD spectra. One layer PEDOT:PSS/GO of 4:2 ratio is fabricated on cotton fabric by using dip coating and screen-printing techniques. Lower resistance of 105 Ω and higher conductivity are achieved by using dip coating technique compared to screen printing, as better absorption of nanocomposite into fiber strands via this method, leads to excellent charge distribution on coated fabric. Resistance increases proportionally with pH values. Resistance of 1.547 kΩ, 3.791 kΩ and 9.18 kΩ are measured for pH 4.00, 6.86 and 9.18 respectively. Nanocomposite layer fabricated with dip coating is also stable, durable and remained intact on the coated fabric after soaking test in distilled (DI) water for 45 minutes. On the other hand, resistance values are 3.11 Ω, 4.81 Ω and 6.54 Ω when the sensor bends at 30°, 60° and 90° respectively. This is due to additional introduced strain and redistribution of charges on the fabric after repeated movements. Based on excellent chemiresistive response towards sweat pH detection, several health conditions such as hyperhidrosis, normal state and cystic fibrosis associated with sweat pH of 4.00, 6.86 and 9.18 respectively, could be possibly identified. These promising results open up possibilities for future studies in the development of nanocomposite-based health monitoring wearable devices.

Effect of Fabrication Technique on Membrane Distillation Performance of Photothermal Membrane: Electrospinning vs Electrospraying

Effect of Fabrication Technique on Membrane Distillation Performance of Photothermal Membrane: Electrospinning vs Electrospraying

In-vitro Comparative Evaluation for the Surface Properties and Impact Strength of CAD/CAM Milled, 3D Printed, and Polyamide Denture Base Resins.

ABSTRACTObjective:There is a paucity of data regarding the effect of fabrication techniques and compositions of CAD/CAM milled, 3D-printed, and polyamide flexible denture base resin materials (DBRMs) on the surface roughness (SR), surface hardness (SH), and impact strength (IS). Therefore, this study aimed to evaluate the SR, SH, and IS of CAD/CAM milled, 3D-printed, and polyamide flexible DBRMs.Materials and Methods:Ninety specimens were constructed from different DBRMs and divided into three groups (CAD/CAM, 3D-printed, and polyamide DBRMs; n = 30) with specific measurements: 15 × 10 × 2.5 mm for SR and H tests and 80 × 10 × 4 mm notched specimen for IS test. SR meter and Vickers micro SH tester were used to measure SR and SH, respectively, whereas the IS was evaluated using Charpy’s impact testing machine. Data were collected and statistically analyzed using one-way analysis of variance and post hoc Tukey’s tests (α=0.05).Results:There were significant differences between the tested materials (P< 0.05). The CAD/CAM milled showed lowest SR when compared with 3D-printed resin and polyamide flexible resin (P< 0.05); however, there was a significant increase in SH of CAD/CAM milled and 3D-printed DBRMs when compared with polyamide materials (P< 0.05). There was a significant increase in IS of polyamide and CAD/CAM milled resins when compared with 3D-printed DBRMs (P < 0.05).Conclusion:CAD/CAM milled resins showed high IS and SH with lower SR.

Effect of Fabrication Technique on the Microgap of CAD/CAM Cobalt-Chrome and Zirconia Abutments on a Conical Connection Implant: An In Vitro Study.

The aim of this in vitro study was to investigate the microgaps at the implant–abutment interface when zirconia (Zr) and CAD/CAM or cast Co–Cr abutments were used. Methods: Sixty-four conical connection implants and their abutments were divided into four groups (Co–Cr (milled, laser-sintered and castable) and Zirconia (milled)). After chewing simulation (300,000 cycles, under 200 N loads at 2 Hz at a 30° angle) and thermocycling (10,000 cycles, 5 to 50 °C, dwelling time 55 s), the implant–abutment microgap was measured 14 times at each of the four anatomical aspects on each specimen by using a scanning electron microscope (SEM). Kruskal–Wallis and pair-wise comparison were used to analyze the data (α = 0.05). Results: The SEM analysis revealed smaller microgaps with Co–Cr milled abutments (0.69–8.39 μm) followed by Zr abutments (0.12–6.57 μm), Co–Cr sintered (7.31–25.7 μm) and cast Co–Cr (1.68–85.97 μm). Statistically significant differences were found between milled and cast Co–Cr, milled and laser-sintered Co–Cr, and between Zr and cast and laser-sintered Co–Cr (p < 0.05). Conclusions: The material and the abutment fabrication technique affected the implant–abutment microgap magnitude. The Zr and the milled Co–Cr presented smaller microgaps. Although the CAD/CAM abutments presented the most favorable values, all tested groups had microgaps within a range of 10 to 150 μm.

Mode of bond failure between 3D-printed denture teeth and printed resin base material: effect of fabrication technique and dynamic loading. An in-vitro study.

To evaluate the failure load of 3D-printed denture resin material and teeth before and after dynamic loading. A total of 40 specimens were fabricated following ISO/TS 19736 and were divided into two equal groups. In the test group, the cylindrical base and denture teeth were 3D printed separately and then luted together. In the control group, the specimens were fabricated from conventional heat-cured polymethyl methacrylate (PMMA) and commercially available denture teeth using the compression-molding technique. Ten specimens from each group were subjected to dynamic load of 50 N for 250,000 cycles in a chewing simulator. All specimens were subjected to static load of 50 N using Instron machine with a crosshead speed of 1 mm/minute until fracture. The fractured surfaces were analyzed using field emission scanning electron microscopy. The failure loads were calculated and compared using analysis of variance (P < .05). All specimens survived the loading, undergoing 250,000 cycles without fracture. The mean failure load was influenced by fabrication technique and was significantly higher for the 3D-printed test group (P = .028). 3D-printed teeth showed a mixed mode of fracture, whereas in the control group, the specimens showed cohesive fracture within the teeth. The fabrication technique has an influence on the mode of failure between acrylic teeth and resin base material. Cohesive failure in teeth was predominant in the conventional group, suggesting possibly higher bond strength between the teeth and resin base in this group. The observed failure modes reveal that both fabrication techniques exhibited satisfactory bond strength. Chewing simulation did not significantly influence the bond strength of any of the tested groups.

Effect of sequential electrospinning and co-electrospinning on morphological and fluid mechanical wall properties of polycaprolactone and bovine gelatin scaffolds, for potential use in small diameter vascular grafts

BackgroundNowadays, the engineering vascular grafts with a diameter less than 6 mm by means of electrospinning, is an attracted alternative technique to create different three-dimensional microenvironments with appropriate physicochemical properties to promote the nutrient transport and to enable the bioactivity, dynamic growth and differentiation of cells. Although the performance of a well-designed porous wall is key for these functional requirements maintaining the mechanical function, yet predicting the flow rate and cellular transport are still not widely understood and many questions remain open about new configurations of wall can be used for modifying the conventional electrospun samples. The aim of the present study was to evaluate the effect of fabrication techniques on scaffolds composed of bovine gelatin and polycaprolactone (PCL) developed by sequential electrospinning and co-electrospinning, on the morphology and fluid-mechanical properties of the porous wall.MethodologyFor this purpose, small diameter tubular structures were manufactured and experimental tests were performed to characterize the crystallinity, morphology, wettability, permeability, degradability, and mechanical properties. Some samples were cross-linked with Glutaraldehyde (GA) to improve the stability of the gelatin fiber. In addition, it was analyzed how the characteristics of the scaffold favored the levels of cell adhesion and proliferation in an in vitro model of 3T3 fibroblasts in incubation periods of 24, 48 and 72 h.ResultsIt was found that in terms of the morphology of tubular scaffolds, the co-electrospun samples had a better alignment with higher values of fiber diameters and apparent pore area than the sequential samples. The static permeability was more significant in the sequential scaffolds and the hydrophilic was higher in the co-electrospun samples. Therefore, the gelatin mass losses were less in the co-electrospun samples, which promote cellular functions. In terms of mechanical properties, no significant differences were observed for different types of samples.ConclusionThis research concluded that the tubular scaffolds generated by sequential and co-electrospinning with modification in the microarchitecture could be used as a vascular graft, as they have better permeability and wettability, interconnected pores, and a circumferential tensile strength similar to native vessel compared to the commercial graft analyzed.

Effect of fabrication techniques on the optical properties of zirconia-based systems

Statement of problemHow the optical properties of zirconia restorations are affected by their differing processing techniques is unclear. PurposeThe purpose of this in vitro study was to evaluate the effects of 5 different fabrication techniques on the optical properties of zirconia-based systems, including the color difference between the corresponding shades (ΔE∗ab, ΔE00), translucency parameter, opalescence parameter, and fluorescence (ΔE∗ab-FL). Material and methodsSixty zirconia disks (IPS e.max ZirCAD) were prepared (0.5 ±0.01mm thick) and veneered by using different techniques (n=15): Group L – layering with fluorapatite ceramic; Group P – pressing with fluorapatite ceramic; Group CB – veneered with pressing followed by layering technique; Group CO – digitally veneered with lithium disilicate glass-ceramic; and Group FZ – prepared from monolithic zirconia (inCoris TZI) (n=15). All the specimens were set to 1.5 ±0.02 mm in thickness. Color measurements were made with a spectrophotometer. Data were statistically analyzed with 1-way ANOVA and the Tukey honestly significant difference, Kruskal-Wallis, Bonferroni (α=.05), Pearson, and Spearman correlation tests (α=.01). ResultsSignificant differences were found among the groups for all the optical parameters (P<.05). All the groups showed color differences higher than the perceptibility and acceptability thresholds for ΔE∗ab and ΔE00, except the P and FZ groups that showed values lower than the acceptability threshold (ΔE∗ab<2.7). Translucency parameter, opalescence parameter, and ΔE∗ab-FL values ranged between 5.77 and 9.95, between 4.72 and 7.07, and between 1.93 and 3.14, respectively. Strong positive correlations were found between ΔE∗ab and ΔE00, as well as between translucency parameter and opalescence parameter (P<.001). ConclusionsThe optical properties of the zirconia-based systems were significantly affected by the fabrication techniques even when the same nominal shade was used. Therefore, the color reproduction, translucence, opalescence, and fluorescence of the selected materials should be considered for acceptable color matching.

Effect of Fabrication Techniques, Resin Types and Fiber Combinations on Mechanical Properties and Morphology of Glass Fiber Composites

Glass fiber composites were fabricated from two different manufacturing techniques, vacuum infusion and vacuum bag, two resin types (epoxy, vinyl ester), as well as and two fiber combinations (S-glass and E-glass). The analyzed properties were tensile modulus, strength as well as compression strength, with relation to sample morphology and fracture surface due to compression. The results showed that all variables and their interaction did not significantly influence tensile modulus, while manufacturing methods was the only significant variable influenced tensile strength. The results showed that vacuum infusion samples had better tensile strength than those produced by vacuum bag due to less resin and bubbles. In term of compression, the change on strength was highly contributed by resin type and fiber used on layer A. Composites samples with epoxy resin showed better strength than those of vinyl ester may be due to better initial resin property. While, imbalance transfer load and fiber density inhibiting resin penetration and causing resin rich samples produced lower compression strength for samples with S-glass applied to layer A than E-glass. Further analysis on fracture surface showed that most samples failed on compression test due to shear, kink and resin break

Effect of Fabrication Technique and Thermal Cycling on the Bond Strength of CAD/CAM Milled Custom Fit Anatomical Post and Cores: An In Vitro Study.

This study is to investigate the effect of milling custom fit anatomical post and cores from fiber reinforced composite and high-density polymer blocks using CAD/CAM technology on the bond strength to root canal dentin compared with prefabricated fiber posts, and to evaluate the influence of thermal cycling on the push out bond strength of the tested materials. Eighty extracted single-rooted premolars, endodontically treated and prepared to receive the posts, were randomly divided into four groups (n = 20): BLC: Custom-milled fiber-reinforced composite posts and cores (Trilor, Bioloren), AMC: Custom-milled high-density polymer posts and cores (Ambarino, Creamed), BLP: Prefabricated fiber-reinforced composite posts and composite core buildups (Bioloren; Filtek Bulk Fill Posterior, 3M). The posts used have the same matrix and fiber composition as BLC, RXP: Prefabricated posts and composite core buildups (RelyX fiber post, 3M; Filtek Bulk Fill Posterior); used as a control group. All of the posts were cemented using a self-adhesive resin cement (RelyX U200, 3M). Half of the sample was randomly assigned to thermal cycling in distilled water for 6,000 cycles to simulate aging, while the other half was tested for bond strength without thermal cycling. A push-out test was conducted using a universal testing machine until failure. Bond strength values were calculated in megapascals (MPa). The mode of failure was observed using a stereo microscope. Results were analyzed by two-way ANOVA followed by a Bonferroni post hoc test for comparison. The level of significance was set at p < 0.05. Push-out bond strength was significantly higher (p<0.001) in the CAD/CAM post groups than in the groups with prefabricated posts regardless of the post material, while aging of the teeth did not significantly affect the push-out strength (p = 0.536). Failures were adhesive between cement and dentin for all groups except for AMC, where adhesive failure between the cement and the post was also observed. The CAD/CAM manufacturing technique was proved to ameliorate the retention of the post and cores in the root canal. Thermal cycling did not affect the bond strength of the tested groups.

Effect of Fabrication Technique on the Marginal Discrepancy and Resistance of Lithium Disilicate Crowns: An In Vitro Study.

To evaluate the impact of fabrication technique on the marginal fit and resistance of lithium disilicate crowns. Twelve ivorine molars were prepared to receive lithium disilicate crowns. The preparations were digitally recorded using an intraoral scanner, and the crowns were designed following the anatomy of an unprepared tooth using a design software. The designed crowns were fabricated using 3 techniques: (1) milling from lithium disilicate blocks using a 3-axis milling machine (3XM), (2) milling from lithium disilicate blocks using a 5-axis milling machine (5XM), and (3) milling from resin-wax billet using a 5-axis milling machine, followed by heat-pressing the pattern into lithium disilicate (5XWP). For the control group, the wax patterns were fabricated by one lab technician, and the crowns were fabricated by heat-pressing the pattern into lithium disilicate (CWP). After sintering, the crowns were secured on their associated preparations using an elastomeric material. The marginal gap of each crown was then measured at 14 defined locations through analyses of 20× images captured with a stereomicroscope. The marginal integrity and resistance to rotation of each crown were assessed by 2 calibrated practitioners. Differences in outcomes by fabrication technique were assessed using Wilcoxon, Kruskal Wallis, and Fisher's exact tests, as appropriate (α = 0.05). Crowns fabricated using digital workflows (3XM, 5XM, 5XWP) had significantly smaller mean marginal gaps compared to the CWP group (p = 0.0001, p = 0.0002, p = 0.0001, respectively); however, 3XM group was the only group to exhibit significantly better marginal integrity than the CWP group (p = 0.0004). No significant difference (p = 0.6004) in the resistance to rotation of crowns was observed between groups. Choice of fabrication technique and instrument may impact the marginal discrepancy of lithium disilicate crowns; however, all fabrication techniques analyzed produced crowns with acceptable marginal discrepancies.

Preparation, characterization, and in vitro release studies of insulin-loaded double-walled poly(lactide-co-glycolide) microspheres

The purpose of this study was to fabricate insulin-loaded double-walled and single-polymer poly(lactide-co-glycolide) (PLGA) microspheres using a fast degrading glucose core, hydroxyl-terminated poly(lactide-co-glycolide) (Glu-PLGA), and a moderate degrading carboxyl-terminated PLGA polymers. A modified water-in-oil-in-oil-in-water (w/o/o/w) emulsion solvent evaporation technique was employed to prepare double-walled microspheres, whereas single-polymer microspheres were fabricated by a conventional water-in-oil-in-water (w/o/w) emulsion solvent evaporation method. The effect of fabrication techniques and polymer characteristics on microspheres size, morphology, encapsulation efficiency, in vitro release, and insulin stability was evaluated. The prepared double-walled microspheres were essentially non-porous, smooth surfaced, and spherical in shape, whereas single-polymer microspheres were highly porous. Double-walled microspheres exhibited a significantly reduced initial burst followed by sustained and almost complete release of insulin compared to single-polymer microspheres. Initial burst release was further suppressed from double-walled microspheres when the mass ratio of the component polymers was increased. In conclusion, double-walled microspheres made of Glu-PLGA and PLGA can be a potential delivery system of therapeutic insulin.

Effect of fabrication technique on the crystalline phase and electrical properties of PVDF films

Abstract The effect of different fabrication techniques on the formation of electroactive β-phase polyvinylidene fluoride (PVDF) has been investigated. Films with varying concentration of PVDF and solvent - dimethyl formamide (DMF) were synthesized by tape casting and solvent casting techniques. The piezoelectric β-phase as well as non polar β-phase were observed for both the tape cast and solvent cast films from X-ray diffraction (XRD) micrographs and Fourier transform infra-red spectroscopy (FT-IR) spectra. A maximum percentage (80 %) of β-phase was obtained from FT-IR analysis for a solvent cast PVDF film. The surface morphology of the PVDF films was analyzed by FESEM imaging. The dielectric properties as a function of temperature and frequency and the ferroelectric hysteresis loop as a function of voltage were measured. An enhancement in the value of the dielectric constant and polarization was obtained in solvent cast films.

Effect of fabrication technique on microstructure and electrical conductivity of polyaniline-TiO2-PVA composite material

The aim of this workis to study the microstructure and D.C electrical conductivity of polyaniline-TiO2-poly-vinyl alcohol polymeric composite material synthesized by two methods. The first method of synthesis involved mixing of 40 wt% blendedpowders of polyaniline and TiO2 micro particles in aqueous solution of PVA and the second method used ‘in situ’ deposition technique in which nano particle sized fine grade anatase TiO2 powder (approximately 50nm average particle size) was placed in the polymerization reaction mixture of aniline, which resulted in polyaniline being deposited on the surface of nano-TiO2 particles forming a core-shell structure. 40 wt% of this composite polymer was then directly blendedwith aqueous solution of poly vinyl-alcohol, resulting in composite polymer of polyaniline-TiO2-poly-vinyl alcohol. The microstructural studies and electrical conductivity results shows that the second method of fabrication not only gives continuous fibrous structure to the conducting polymer without any agglomeration of TiO2, whereas in first method agglomeration of TiO2 results in conducting and non-conducting zone. It gives films with higher D.C electrical conductivity, in comparison to first method, which increases with increasing voltage.

Supercritical CO2 processing of a chitosan-based scaffold: Can implantation of osteoblastic cells be enhanced?

The effects of fabrication techniques were investigated for preparation of a chitosan based scaffold. A two-step process was used: fabrication of hydrogel which was subsequently processed either with supercritical CO2 (SC-CO2) or lyophilization. Various pressures from subcritical to supercritical (70, 160, 250bar), temperatures (35, 45, 55°C) and durations (2–3h) were applied in order to elicit the optimum process parameters yielding the highest porosity which were determined as 250bar, 45°C, 2h of processing at 5g/min CO2 flow rate yielding a porosity of 87.03% which was similar to lyophilization (88.68%) achieved at 55°C for 48h. When osteosarcoma cells possessing cellular features of osteoblasts were seeded, SC-CO2 dried scaffold proved to be a more ideal support for cell attachment owing to the presence of both nano and micropores, thereby providing a more efficient and rapid alternative for tissue engineering applications.

The Impact of Wire Stent Fabrication Technique on the Performance of Stent Placement

Braided wire stents demonstrate distinct characteristics compared to welded ones. In this study, both braided and welded wire stents with the same nominal dimensions were crimped inside a sheath and then deployed into a stenosed artery using finite element analysis. The braided wire stent was generated by overlapping wires to form crisscross shape. A welded wire stent was created by welding the intersection points of wires to avoid sliding between wires. The effect of fabrication technique on mechanical behavior of Nitinol wire stents was evaluated. The results showed that relative sliding between wires reduced the deformation of the braided stent, which led to less radial strength than the welded one; therefore, the deployed braided stent was more conformed to the anatomic shape of the lesion and much less efficient for restoring the patency of the stenotic artery. Post balloon-dilation was commonly used to improve its performance in terms of lumen gain and deployed shape of the stent. On the contrary, the welded wire stent exhibited a high capacity for pushing the occlusion outward. It reached an approximately uniform shape after deployment. The welded joints caused larger deformation and high strain on the stent struts, which indicate a potential earlier failure for the welded stent. In addition, higher contact pressure at the stent-lesion interface and higher arterial stresses were observed in the artery supported by the welded stent. The peak stress concentration may increase the occurrence of neointimal hyperplasia.

Marginal Fit of Implant-supported All-Ceramic Zirconia Frameworks

Abstract Objective: This study evaluated the effect of fabrication techniques and cyclic loading on the vertical marginal fit of implant-supported FPD frameworks. Methods: Thirty implant supported 3-unit FPD frameworks were fabricated on a model system, divided into three equal groups (n=10). The first group (control) was constructed from base metal alloy and the other two test groups were constructed from All-ceramic Zirconia using CAD/CAM Cerec III system and copy milling (Zirconzahn) system. A cyclic load of 200 N was applied to each framework for up to 50,000 cycles. Linear measurements were made in micrometers (µm) of the vertical gap between the framework and implant-supported abutment at 16 predetermined points before and after cyclic loading. The frameworks were viewed using SEM to inspect any fractographic features. One way analysis of variance (ANOVA) was performed to compare the marginal discrepancy values of the control and the two test groups and for each group; T-test was applied to determine whether significant changes in the fit were observed after cyclic loading. (α=0.05). Results: CAD/CAM group showed significantly higher marginal gap mean values (80.58 µm) than Zirkonzahn and control groups (50.33 µm and 42.27 µm respectively) with no significant difference while, after cyclic loading, CAD/CAM group recorded the highest marginal gap mean value (91.50 ± 4.260 µm) followed by control group (72.00 ± 2.795 µm) while Zirconzahn group recorded the lowest marginal gap (65.37 ± 6.138 µm). Cyclic loading significantly increased the marginal gap mean values in the control group only. Marginal chip was observed in one of the CAD/CAM ceramic frameworks. Conclusions: Within the limitations of this study, the fabrication technique influenced the marginal fit of the implant supported 3-unit FPD frameworks. Cyclic loading failed to change the fit of all-ceramic Zirconia frameworks while; significant changes were found in the metal frameworks.

Effects of fabrication technique upon material properties and permeation characteristics of palladium-gold alloy membranes for hydrogen separations

This work highlights new research into the fundamental properties of palladium-gold alloy membranes. Two types of self-supported palladium-gold foils were studied; membranes produced by magnetron sputtering and membranes produced by cold-working. The cold-worked membranes had thicknesses of 25 microns and gold contents from 0-40 wt% Au, while the sputtered films ranged from 10-31 microns in thickness and 5-10 wt% Au. These films were characterized by single-gas permeation testing in the temperature range of 473-773K and at pressures of up to 772 kPa. Membranes were studied before and after testing by XRD, XPS, XRF, and SEM/EDS. Hydrogen permeability in the 0-20 wt Au% range was found to be a function of synthesis technique as much as alloy content, with no single alloy having superior permeability at all temperatures. Sputtered materials had generally higher permeability than cold-worked materials of equivalent composition, although the thicker sputtered membrane had reduced hydrogen permeability compared to its thinner counterparts.