Testing Machine Research Articles

Hot deformation behavior and dynamic recrystallization mechanism of GH2132 superalloy

In order to study the hot deformation and dynamic recrystallization behavior of annealed GH2132 superalloy, this paper conducted hot compression tests of GH2132 superalloy at different temperatures (950°C–1150°C) and different strain rates (0.01/s–10/s) using Thermocmaster Z thermal simulation testing machine, and made an in-depth analysis of recrystallization behavior via electron backscattered diffraction (EBSD). The results indicate that the flow stresses of GH2132 alloy first increase and then decrease at high temperature, among which the curves present a more obvious flow softening at 10/s. Continuous dynamic recrystallization (CDRX) is dominant at high temperature and low strain rate, while discontinuous dynamic recrystallization (DDRX) plays the major role at low temperature and high strain rate. The type of recrystallization has a significant impact on the formation and volume fraction of twinning. In addition, high-temperature constitutive model, hot processing map, and an unified dynamic recrystallization kinetic model of GH2132 superalloy were established. Thus, the optimal range of hot working parameters was obtained. The research results provide guidance for determining the hot working process window of GH2132 superalloy.

Impact of applied and preceding pressure on performance and reversible swelling of lithium-ion pouch cells with varying microporous separators

During the compression of battery cells in battery pack production, high forces occur temporarily due to the viscoelastic behavior of the cell components. The magnitude of these forces depends on the compression speed. Shortening the production time and, thus, increasing the compression speed is desirable for cost reduction. However, it must be ensured that the cells are not negatively affected by increased forces during production. The impact of these preceding forces, acting on the cell before operation, and the applied force during operation on the performance and the reversible swelling of 5Ah NMC811/graphite lithium-ion pouch cells are investigated in this study. To this end, a universal compression testing machine was adapted to enable high-precision thickness measurements under defined constant pressure and temperature conditions. In addition, the effects of different microporous separators manufactured via dry process and wet process in an otherwise identical cell configuration were investigated. In the test procedure, the pressure was incrementally increased from 0.01MPa to 2.5MPa. Each measurement was performed at the distinct constant pressure levels, followed by a subsequent measurement at a reference pressure of 0.2MPa to evaluate the impact of the preceding step. The results revealed that elevated preceding pressures on the cell can reduce the discharge rate capability on higher C-rates by up to 11%. The discharge rate capability of the cells with the wet-processed separator was more significantly influenced by increasing applied and preceding pressure than for those with the dry-processed separator. It was found that the reversible swelling of the cell was reduced by applying higher pressures, whereas elevated preceding pressure increased the reversible swelling. The results of this study suggest that cells should not be subjected to excessive forces before operation, for instance, during battery pack production, as this can negatively affect performance and swelling behavior. Furthermore, the mechanical stability of the separator during the pack production process should also be considered when designing a cell.

A novel method for identifying rock interfaces and fragmentation zones based on drilling response characteristics

The rapid measurement and acquisition of the fracture characteristics and strength of the surrounding rock are crucial for evaluating the stability of underground engineering. In this study, a laboratory/coal mine universal drilling test platform was developed to enable real-time measurement of drilling parameters. The testing results demonstrate that under identical rotation speed conditions, both thrust force and torque increase exponentially with increasing drilling speed, while under identical drilling speed conditions, both thrust force and torque decrease linearly with increasing rotation speed. In intact rock layers, variations in torque, thrust force, and drilling speed with depth remain relatively stable, in rock layer interfaces and fragmentation zones, sudden changes occur within a drill displacement range of approximately 3–7 mm, which become more pronounced as strength differences between adjacent rock layers increase.Based on the cutting mechanics model of drill bit, the evaluation index of drilling energy consumption of unit rock mass (Eη) is derived. Subsequently, based on drilling speed, rotation speed, thrust force, torque and energy index, a machine learning model for predicting rock strength is established using the LS-SVM nonlinear regression approach. Field practice has shown that drilling platform can effectively identify both the rock interface and range of fragmentation areas. The experimental results are of great value to the selection of supporting types in the process of coal mine roadway excavation.

Study on fracture behaviour of pipeline girth welds based on curved wide plate specimens: Experimental and numerical analysis

Understanding the fracture characteristics and strain capacity of pipelines with girth welds under external loads is crucial for evaluating pipeline safety. The use of curved wide plate (CWP) specimens closely resembling full-scale (FS) pipelines in geometry provides a more realistic representation of crack tip constraint states compared to small-size fracture toughness test specimens in laboratory settings. This study aims to investigate the ductile fracture characteristics of center cracks on the outer surface of girth welds in high-grade steel pipelines under external loads through large-scale CWP tensile tests and advanced numerical simulations. Tensile tests were conducted on CWP specimens using a kiloton tensile testing machine, with double crack opening displacement (COD) gauge monitoring crack mouth opening displacement (CMOD), and high-precision displacement sensors and strain gauges tracking deformation and strains at various positions. The study yielded significant experimental results, and a finite element (FE) model of the CWP was developed using the nonlinear finite element method (FEM) to validate the experimental data against simulation results. The FE model was then used to investigate the influence of material properties on crack propagation resistance and driving force curves. A method for determining the ultimate tensile strain capacity (UTSC) of pipelines based on actual material fracture toughness was proposed. This research contributes valuable experimental data for further exploration of fracture behaviour in large-scale pipeline girth welds and offers insights for safety evaluations of such welds.

A realistic approach for evaluating antimicrobial surfaces for dry surface exposure scenarios.

The severe acute respiratory syndrome coronavirus 2 pandemic has raised public awareness about the importance of hygiene, leading to an increased demand for antimicrobial surfaces to minimize microbial contamination on high-touch surfaces. This is particularly relevant in public and private transportation settings, where surfaces frequently touched by individuals pose a significant, yet preventable, risk of infection transmission. Typically, the antimicrobial activity of surfaces is tested using test methods of the International Standards Organization, American Society for Testing and Materials, or Japanese Industrial Standards, which involve complete submersion in liquid, elevated temperature (37°C), and prolonged (24 h) contact periods. However, these conditions do not accurately represent real-world scenarios where surfaces are exposed to air. In this study, we propose a modified test method designed to better reflect real-life conditions in the intended end-use setting. The modifications included using deionized water instead of nutrient broth while preparing bacterial inoculum, applying a small test inoculum to the surface and allowing it to dry, maintaining ambient temperature and relative humidity throughout the contact period, and reducing the contact period to 4 h. With this modified approach, the antimicrobial activity of 20 samples was reassessed. This screening revealed that out of 20 samples, only 2 samples were effective against all species, while 8 samples demonstrated partial effectiveness against selected species, and 10 samples showed no significant effect. These findings highlight the inadequacy of the current test standard and emphasize the urgent necessity for revised and adapted testing method to ensure a reliable and accurate evaluation.IMPORTANCEThe recent severe acute respiratory syndrome coronavirus 2 pandemic has sparked increased demand for antimicrobial surfaces to mitigate the risk of fomites-transmitted infection in both indoors and confined spaces. Commonly, the antimicrobial activity of these surfaces is assessed using test standards established by national standards bodies, which do not distinguish between different application scenarios. While these test standards are suitable for surfaces intended for submerged application, they are inappropriate for antimicrobial surfaces designed for dry surface exposure. The usage of these standards can lead to an overestimation of antimicrobial efficacy. Thus, this study introduces a modified dry exposure test method aimed at better reflecting real-life conditions in the intended end-use setting. Our results revealed the subpar antimicrobial performance of numerous samples, highlighting the necessity to revise and tailor the universal test standard to real-world scenarios in order to ensure a reliable and accurate evaluation.

The Comparison of Performance of Root Vetiver Grass Between Coconut Fiber and Eggshell Toward Slope Stabilization

Slope stability using vegetation has emerged as a more environmentally friendly and sustainable solution for slope stabilization, replacing traditional structural engineering methods and shotcrete cover. However, despite the application of Vetiver grass, failures in the form of deformation, cracks, and slope collapse still occur. The main objectives of this study are to identify the root properties and analyze the mechanical properties of Vetiver grass with coconut fiber and eggshell fertilizers. Laboratory testing was conducted to determine the mechanical properties of Vetiver grass roots using shear box and universal testing machine. As a result, the root diameter and root length with egg shell exhibit larger values than coconut fiber for 21 days (0.40 – 1.27 cm) and 35 days (11.5 – 61.4 cm). The direct shear test results for Vetiver root with eggshell showed highest shear strength which is 43.67 kN/m2 (21 days) and 168.17 kN/m2 (35 days) compared to Vetiver root with coconut fiber which is 42.94 kN/m2 (21 days) and 61.13 kN/m2 (35 days). For tensile strength, the Vetiver root with egg shell consist higher value which is 0.066 N/mm² (group 1) and 0.068 N/mm² (group 2) compared to Vetiver root with coconut fiber which is 0.059 N/mm² (group 1) and 0.060 N/mm² (group 2). Additionally, in group 1 and 2 of 35 days, eggshell fertilizer showed higher maximum tensile strength, measuring 0.071 N/mm² and 0.094 N/mm², respectively. While, coconut fiber fertilizer 1 and 2 recorded lower tensile strengths of 0.063 N/mm² and 0.062 N/mm², respectively. The significance of this study indicates that the eggshell fertilizers have greater impact towards Vetiver root than coconut fiber fertilizers and without fertilizer.

Synergistic effects of graphene nanoparticles on the thermomechanical properties of PEEK-HNTs nanocomposites

In our previous study, we selected a 3% concentration (PH3) from various prepared PEEK-HNTs nanocomposites. Poly (ether ether ketone) (PEEK) is characterized by non-perfluorinated aromatic compounds with 1,4-disubstituted phenyl groups linked by carbonyl (––CO––) and ether (––O––) groups, offering exceptional thermal stability, mechanical strength, tribological properties, and chemical resistance at high temperatures. Halloysite nanotubes (HNTs) are known for their non-toxic, environmentally friendly, cost-effective properties, with tunable release and rapid adsorption rates. In this study, we prepared graphene nanoparticle (GNP) composites at three different concentrations while maintaining constant PH3 levels. The composites underwent comprehensive characterization using FTIR, TGA, DSC, SEM, and DMA techniques. Thermomechanical properties were evaluated using a universal testing machine. Results demonstrate significant enhancements in hardness, impact strength, elongation at break, tensile modulus, and flexural modulus, with the highest performance observed in the GNP-loaded 0.3% (PHG3) concentration. The synergistic effects of GNP fillers in PH3 are attributed to enhanced interfacial adhesion and favorable interactions with the polymer matrix.

Flexural strength and viscosity of dental luting composite reinforced with zirconia and alumina

Objectives Optimum flexural strength and viscosity are essential for longevity while efficiently handling dental luting composite. This study aims to investigate the effects of zirconia and alumina on the flexural strength (FS)and viscosity of dental cement made of silica rice husk. Materials and Methods Study groups with different percentages of weight (wt.): Group 1 (3 wt.% zirconia), Group 2 (3 wt.% alumina), and Group 3 (3 wt.% zirconia and 2 wt.% alumina), negative control specimen (0 wt.% zirconia/ alumina) and Rely-X U200 (3M ESPE). A universal testing machine and a rheometer were used to test FS and viscosity, respectively. One-way ANOVA and post-hoc Bonferonni test were used for data analyses. Results and Discussion FS and viscosity for Group 3 (3 wt.% zirconia and 2 wt.% alumina) were significantly higher compared to the negative control (p<0.05). Conclusion: Adding zirconia and alumina improved flexural strength without compromising the viscosity of dental luting composite. This experimental dental luting cement using hybrid fillers could be an alternative to resin luting cement. Bangladesh Journal of Medical Science Vol. 23 No. 04 October’24 Page : 1048-1053

Test of universality at first order phase transitions: The Lebwohl-Lasher model.

Finite size scaling for a first order phase transition, where a continuous symmetry is broken, is tested using an approximation of Gaussian probability distributions with a phenomenological "degeneracy" factor. Predictions are compared to the data from Monte Carlo simulations of the Lebwohl-Lasher model on L × L × L simple cubic lattices. The data show that the intersection of the fourth-order cumulant of the order parameter for different lattice sizes can be expressed in terms of the relative degeneracy q = 4π of the ordered and disordered phases. This result further supports the concept of universality at first order transitions developed recently.

Effect of symmetrical biaxial tension on the magnetic properties of the composite specimen of two steel plates with different mechanical and magnetic properties

The results of studying the behavior of the magnetic characteristics of two-layer material containing layers of annealed sheet low-carbon Steel 15 and sheet metastable austenitic 12Kh18N9Т steel, subjected to cold rolling with a compression of 50 %, under biaxial symmetric tension have been presented. Experiments on biaxial deformation were carried out on the original biaxial testing machine, allowed to determine the physical properties of materials during elastic-plastic deformation independently along two axes. It has been shown that the coercive force of the studied two-layer material vary monotonically over the entire range of elastic-plastic biaxial deformation and can be used as an informative parameter for assessing the it’s stresses and deformations.

Experimental and analytical study on the compressive behavior of PMI foam with different densities and cell sizes under intermediate strain rates

Polymethacrylimide (PMI) foam materials have great potential for applications in the field of protective energy absorption owing to their superior compressive properties. Existing studies on the mechanical behavior of PMI foams are limited, particularly for loading at intermediate strain rates. This paper presents a comprehensive experimental study of PMI foam with four different densities under quasi-static and intermediate strain rate compression (0.001 s−1 to 100 s−1). Each density included three different cell sizes to determine their effects on the compressive performance. Loads parallel and perpendicular to the foam rise direction were considered to investigate the anisotropic behavior. Intermediate strain rate tests were conducted using a high-speed hydraulic servo testing machine, which achieved a stable strain rate while ensuring consistent specimen sizes in both quasi-static and dynamic tests. In all the experiments, the compression process was captured using a high-speed camera and the macroscopic deformation mode and microscopic deformation mechanism were analyzed by combining Digital Image Correlation (DIC) and Scanning Electron Microscopy (SEM). The PMI foam with finer cell sizes exhibited an enhanced compression performance. As the strain rate increased, the strain rate effect became more evident in the high-density specimens and an increase in cell size diminished this effect. A modified analytical model incorporating the cell-size correction term was developed based on Gibson and Ashby's model. The modified model exhibited an average error of 4.9 % in the predicted plateau stress of PMI foam with different cell sizes at the same density.

B-259 Cannabinoid Prevalence in Umbilical Cord Tissue Toxicity Testing

Abstract Background Cannabis is rapidly becoming legalized in the United States. While its effects on the developing fetus are not fully understood, current recommendations advise against cannabis use and exposure during pregnancy due to its association with negative outcomes, such as preterm birth, fetal growth restriction, low birth weight, and developmental deficits. If drug exposure is suspected, umbilical cord tissue (UCT) testing is growing in frequency as a tissue of choice when testing infants. Neonatal testing protocols vary between hospitals, including both targeted or universal collection and targeted or universal testing of neonatal specimens. Based on the current environment of legalization, we were curious to see what the changes in cannabis use were over the previous five years, from 2019-2023. Methods We queried our laboratory information system for reported findings from screening and confirmatory umbilical cord testing, both of which were analyzed via liquid chromatography tandem-mass spectrometry (LC-MS/MS). Results were analyzed using R coding software. Results Overall, annually, 2019-2023 positivity rates for testing in general ranged from 41% - 44% positivity and maintained at 44% from 2020 onwards (n=90384 total workorders 2019-2023, n=40551 total positive workorders). Cannabinoids were starkly the most common drug found, accounting for 59-63% of all positive workorders annually from 2019-2023. There were no statistically significant differences in the cannabinoid positivity rates between 2019-2023. Of note, cannabinoid-only (delta-9-carboxy THC) workorders accounted for 28% of all positive workorders (n=25962) during that time frame. This was followed by methamphetamine-only (n=2485 workorders) and buprenorphine-only (n=1765 workorders). The combination of cannabinoids and methamphetamine, the most common drug combination found in UCT testing, had a range of positive results from 2019 - 2023 of 2.9 - 3.6% (n=1327 workorders). Cannabinoids and cocaine, the second most prevalent drug combination, ranged in positivity from 1.3 - 1.6% from 2019-2023 (n=616 workorders). Conclusions Cannabinoid exposure is prevalent in pregnant individuals undergoing UCT testing. Physicians should take care to keep informed on the impacts of cannabis exposure on the developing fetus and educating clients on the effects of cannabis exposure during pregnancy.

Structural Characterization and Grading of Timber Species for Engineering Applicability in Kenya

An investigation was carried out in Kakamega County to determine the characteristic grade of eucalyptus and cypress timber species that are commonly used in construction. The physical and mechanical properties of two timber species for structural use; eucalyptus and cypress were determined. Six logs of each species were obtained from different areas of Kakamega County, sliced into 2” by 12” size before seasoning under a shade and their structural strength properties were determined at a moisture content of 12%. These logs were cut into test samples for the determination of their strength properties. A total of 800 samples (100 samples for each test) free from visible defects were used for each species. Basic physical properties of the samples like moisture content and density were determined. Tensile strength, compressive strength parallel the grain, compressive strength perpendicular to the grain, and bending strength were the mechanical strength tests carried out according to Eurocode 5 (1995) and BS 5268 (2002) specifications on Universal Testing Machine (UTM). Results were analyzed statistically using Statistical Package for Social Sciences (SPSS) while grading was done according to Eurocode 5 (EC5). Cypress was graded into strength class C20 while eucalyptus was graded into strength class D24. Strength class C20 is used in load-bearing structures that require high strength, such as roof trusses and floor systems. D24 is a common structural grade for a variety of structures exposed to high environmental conditions.

Effect of Inter-Implant Distance on Fracture Resistance of Implant-Supported Provisional Fixed Dental Prosthesis.

This study aimed to identify the ideal interimplant distance for optimum outcome on immediately loaded implant supported prosthesis. Hence this study was taken up to analyze the effect of varying interimplant distance on fracture resistance of implant supported provisional fixed dental prosthesis (FDP). A total of 24 bis-acrylate composite resin samples were prepared. Interimplant distance was present in the metal die for placement of dummy implants at distances of 14 mm, 21 mm, and 30 mm respectively. Wax-up for 3-unit, 4-unit, and 5-unit implant-supported provisional restoration was made. Silicone molds were used for making multiple interim prostheses using bis-acrylate composite material. All samples were subjected to fracture test in the universal testing machine with a crosshead speed of 1 mm/min. All samples were loaded with gradual force starting from 100 N until it fractured. The load was applied at the center of prosthesis. Data was analyzed by one-way analysis of variance and Bonferroni post hoc test. Mean fracture resistance of 3-unit provisional FDP at 14 mm of interimplant distance showed 1342.61 ± 179.15 N. Mean fracture resistance of 4-unit provisional FDP at 21 mm of interimplant distance showed 1420.44 ± 170.37 N. Mean fracture resistance of 5-unit provisional FDP at 30 mm of interimplant distance showed 791.61 ± 203.59 N. Both 14 mm and 21 mm of interimplant distance are suitable span lengths to be considered for the optimum outcome during immediately loading with implant-supported provisional restorations. Limitations of the study were that force application was static in nature and not dynamic and the arch form was not "U" shaped but longitudinal using Bis-Acryl material only with no cantilever. Future studies can be done to evaluate the fracture resistance of bis-acrylate material considering biomechanics and arch form of natural dentition. Distal cantilever should be considered along with different material for fabricating provisional restoration.

Recombinant Keratin-Chitosan Cryogel Decorated with Gallic Acid-Reduced Silver Nanoparticles for Wound Healing.

Wound healing is a complex physiological process that can be roughly divided into four stages: hemostasis, inflammation, proliferation, and remodeling. Conventional wound dressings often fail to meet the diverse needs of these healing stages due to their limited functionality. Cryogels, however, possess several attractive properties, such as large, interconnected pores, good mechanical strength, and ease of modification, making them suitable for developing advanced dressings with multiple functions. In this study, we developed a multifunctional cryogel dressing, with biocompatible polysaccharides as the main component, designed to provide a breathable, moist, and antibacterial microenvironment for chronic infected wounds, thereby promoting wound healing. Recombinant keratin 31 (RK31) was combined with chitosan (CS) to produce a CS/RK31 cryogel, referred to as CK. Gallic acid-reduced silver nanoparticles (GA/Ag NPs) were incorporated as the active antibacterial component to create the CS/K31@GA/Ag cryogel, known as CKGA. The cryogel was characterized using scanning electron microscopy (SEM) and a universal testing machine, and its biocompatibility was assessed in vitro. The dynamic hemostatic performance of the cryogel was evaluated with a rat tail amputation bleeding model. Additionally, the antibacterial effects of the cryogel against Staphylococcus aureus and Escherichia coli were tested using agar diffusion assays and turbidimetry. The antioxidant capacity of the CKGA cryogel was also measured in vitro. Finally, the cryogel's ability to promote wound healing was tested in an SD rat model of infected wounds. Characterization results showed that the CKGA cryogel features an interpenetrating porous network structure and exhibits excellent mechanical properties, with a swelling rate of up to 1800%. Both in vitro and in vivo experiments confirmed that the cryogel has good biocompatibility, effectively absorbs exudates, and rapidly stops bleeding. The addition of GA/Ag NPs provided significant antibacterial effects, achieving an inhibition rate of over 99.9% against both S. aureus and E. coli. Furthermore, CKGA cryogels demonstrated a strong scavenging capacity for ROS in a dose-dependent manner. Studies using the SD rat infected wound model showed that the cryogel effectively inhibited bacterial proliferation on wound surfaces, reduced local tissue inflammation, and promoted the healing of infected wounds. The multifunctional cryogel, with its rapid hemostatic, antibacterial, and antioxidant properties, as well as its ability to promote cell proliferation, could be widely used as a wound dressing for the healing of bacterial infections.

Facile development of flexible cellulose acetate-lead dioxide membrane electrodes for supercapacitor applications

Current work focuses on the development of flexible membranes of cellulose acetate containing lead dioxide for supercapacitor applications. The functionality of cellulose acetate and lead dioxide are analyzed by Fourier transform infrared spectroscopy. The degree of crystallinity is studied using X-ray Diffraction. The degree of hydrophilicity is discussed by water contact angle measurements. A Universal Testing Machine is used to examine the mechanical properties. The electrochemical performances are illustrated using Cyclic voltammetry, Electrochemical impedance Spectroscopy and Galvanostatic charge-discharge techniques. The highest recorded specific capacitance is 148 F g−1 at a current density of 40 mA g−1 for a membrane of 1 wt% lead dioxide in cellulose acetate. Capacitance retention of 89% after 5000 cycles is attained. The power density of 56 W kg−1 and energy density of 10 Wh kg−1 is achieved. The cellulose acetate doped with lead dioxide membranes can provide a better electrode material matrix for flexible energy storage.

3D-Printed One-piece Versus Two-piece Orthodontic Clear Aligner Attachments Bonded with Provisional Crowns: A Proof of Concept

ObjectivesThis study aimed to introduce a novel technique for fabricating provisional crowns integrated as a single unit with aligner attachments. MethodsA total of 60 crowns with attachments were prepared: 20 conventional (Protemp) and 40 3D-printed (20 bonded with attachments; 20 integrated with composite attachments as a single unit) using NextDent resin. Two central incisors were scanned (once without attachments and once with attachments) to create STL files for specimen printing. Half of the specimens (30, n=10 per group) underwent thermal cycling (5000 cycles). Shear bond strengths (MPa) were evaluated using a universal testing machine. The debonded areas and attachment failures were analyzed to determine the fracture type. Data analyses were performed using ANOVA and post hoc Tukey tests (α = .05). ResultsThe 3D-printed specimens showed higher strength values than the bonded attachments per group (P <0.001). The 3D-printed crowns with attachments demonstrated the highest strength (12.39±1.92 MPa). Thermal cycling significantly decreased the bond strength of the attachments (P <0.001), except in the 3D-printed crowns with composite attachments as a single unit, which showed no significant change after thermal cycling (P=0.643). In the bonded attachment groups, the adhesive type was the predominant failure mode, while in the 3D-printed groups, attachment fractures were the primary cause of failure. ConclusionThe 3D-printed provisional crowns with attachments have high strength and is clinically appropriate for orthodontic treatment when temporization of teeth is indicated. Clinical SignificanceThe developed technique for fabricating 3D-printed provisional restorations with orthodontics attachments as a single unit is a promising approach. The technique may be incorporated into the digital orthodontic treatment workflow when temporization is indicated.

Effect of preparation design on fracture resistance of molars restored with occlusal veneers of different CAD-CAM materials: an in vitro study

BackgroundOcclusal veneer had been evaluated for mechanical properties using lithium disillicate. However, studies evaluating the mechanical properties of occlusal veneer with different preparation designs and ceramic materials are lacking. So, this in vitro study aimed to evaluate the fracture resistance of occlusal veneers with two designs fabricated from two different ceramic materials.Material and methodsFourty mandibular third molars were distributed to 2 groups (n = 20) according to preparation design: group (O) anatomical occlusal reduction and group (OA) anatomical occlusal and 1 mm axial reduction. Each group was additionally subdivided into two subgroups (n = 10) according to ceramic materials; in subgroup X, lithium disilicate (e.max CAD, Ivoclar AG, Schaan, Liechtenstein) was used, and in subgroup S, zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VitaZahnfabrik, Bad Säckingen, Germany) was used. All specimens were cemented with a light-cure resin cement (Choice 2, Bisco, Schaumburg, USA). 5000 thermocycles were applied to all specimens with both temperatures of 5 °C and 55 °C in two water baths; the dwell time was 30s at each bath, and the transfer time was 10s. Then all specimens were subjected to a fatigue simulation under dynamic loading of 200 N for 250,000 cycles. A universal testing machine (5500R/1123, Instron, Norwood, USA) was used to evaluate the fracture strength with a crosshead speed of 1 mm/min. All data were analyzed statistically by using a two-way ANOVA, and for some violations of assumptions, these results were compared with those obtained by the nonparametric test (Scheirer Ray Hare) (α = 0.05).ResultsA statistically significantly higher fracture resistance in the ‘OA’ (3389 N) compared to the ‘O’ (2787 N) group regardless of the ceramic material (P < .001) and a statistically significantly higher fracture resistance in the ‘X’ (3295 N) compared to the ‘S’ (2881 N) regardless of the preparation design (P = .015).ConclusionsFor occlusal veneers, all preparation designs and materials (such as Vita Suprinity and e.max CAD) had clinically acceptable fracture resistance values that were greater than the maximal biting forces. On the other hand, the e.max CAD with occlusal veneer, including axial reduction design, demonstrated the maximum fracture resistance value. Finally, no relationship between fracture strength and mode of failure was found.

Development and characterization of nitazoxanide-loaded poly(ε-caprolactone) membrane for GTR/GBR applications

ObjectiveGuided tissue/guided bone regeneration (GTR/GBR) membranes are widely used for periodontal bone regeneration, but their success depends on a bacteria-free environment. Systemic antibiotic treatment often proves inadequate, moreover, the increasing prevalence of antibiotic resistance in oral infections exacerbates this challenge. This study aimed to fabricate antibacterial membranes using a new class of antibiotics for local drug delivery, to eradicate infections and promote tissue regeneration. MethodsMembranes loaded with nitazoxanide (NTZ) were fabricated via electrospinning using poly(ε-caprolactone) (PCL) with varying concentrations of NTZ (0 %, 2.5 %, and 5 % w/w) relative to the polymer weight. Morphochemical of NTZ-loaded membranes were assessed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier Transform Infrared spectroscopy (FTIR). Mechanical properties were evaluated using universal testing machine and NTZ release profile from membranes was determined by spectrophotometer (λmax = 444) for 14 days. Antimicrobial efficacy against periodontal pathogens, cell compatibility and mineralization were evaluated using periodontal ligament stem cells (PDLSCs). ResultsOptimized spinning parameter maintained a uniform fiber diameter and successful loading of NTZ was confirmed by SEM-EDS and FTIR. NTZ incorporation did not significantly affect mechanical properties, whereas the drug release kinetics showed an initial burst, followed by sustained release over 14 days. NTZ-loaded membranes demonstrated antibacterial activity against Aggregatibacter actinomycetemcomitans (Aa) and Fusobacterium nucleatum (Fn). Importantly, the presence of NTZ showed minimal cell toxicity; however, it reduced the mineralization potential compared with that of the pure PCL membrane, which increased over time. SignificanceTaken together, these findings established that NTZ-loaded membranes could be promising barrier membrane to counteract microbial environment and aid periodontal bone regeneration.

Evaluation of tensile bond strength of two different cements used for luting zirconia coping to one-piece zirconia implant - An in vitro study

Aim: The purpose of this in vitro study was the evaluation of the tensile bond strength of two different cements used for luting zirconia coping to one-piece zirconia implant. Settings and Design: The study was designed in an in vitro study setting. Materials and Methods: A one-piece zirconia implant was scanned on laboratory scanner, and thirty zirconia implants were milled by computer aided manufacturing (CAM). Subsequently, the abutment surface of each zirconia implants were scanned in laboratory scanner and coping with a hole was designed by computer-aided designing software, which was used for milling by computer-aided manufacturing (CAM). After various surface treatments of abutment and intaglio surface of coping, fifteen sets were cemented by glass ionomer cement (Group I) and the other fifteen sets by adhesive resin cement (Group II). All thirty samples after thermocycling were dried and pulled out in a universal testing machine, and tensile retention force is noted in pounds per square inch (psi). Statistical Analysis Used: Values for tensile retention force were tabulated for both the groups. Mean and standard deviation are calculated. Independent t-value and P value were calculated. Results: The least tensile retention force was reported in Group I (165.86 ± 25.74 psi). Maximum tensile retention force was received for Group II (396.81 ± 78.32 psi). Independent t-test was applied from which t-value calculated was 10.85 and P value obtained was 0.001, which means that there exists a very high difference in tensile bond strength of cement in Group I and Group II. Conclusions: Better tensile retention forces were observed in samples cemented with adhesive resin cement when compared to samples cemented with glass ionomer cement.