Testing Machine Research Articles

Comparison of Bond Strength of Soft Denture Liner on the Denture Base Materials Produced by Different Methods and Effect of Thermocycling

Aim: This study set out to determine the tensile bond strength between denture bases (produced by 3D printing technology, conventional technique, and computer-aided design and computer-aided manufacturing [CAD/CAM] milled) and silicone-based soft lining material. The consequence of thermocycling on the bonding strength was also investigated. Materials and Methods: The bonding between denture foundation materials produced through three distinct techniques (conventional, CAD/CAM milled, and 3D printed) and silicone-based soft lining material was examined. Before tensile testing, half of the samples underwent thermocycling (5–55°C, 5,000 cycles) in 37°C distilled water for 48 hours. A universal testing apparatus employed a crosshead speed of 5 mm/min. The failure type was identified visually, and the maximum tensile strength was noted. The Shapiro-Wilk test and analysis of variances ( P = .05) were used to assess the statistics. Results: CAD/CAM milled denture base material (1.56 ± 0.62/1.36 ± 0.16 MPa) showed higher bond strength values than the other denture bases in the tensile test conducted before and after thermocycling ( P < .001). The denture base material made conventionally had the lowest bond strength (1.02 ± 0.24/0.77 ± 0.1 MPa) ( P < .001). The tensile bond strength values of the conventional and 3D printing groups showed a statistically significant drop before and after thermocycling ( P = .001). Regardless of thermocycling, adhesive failure was primarily seen in all groups (76.6%). Conclusion: Compared to conventionally produced denture bases, the bond strength of soft relining materials to CAD/CAM milled and 3D printed denture base is different. In denture base materials that are conventionally, CAD/CAM and 3D printed, the thermocycling method reduced bonding strength values.

Comparative analysis of an epoxy resin-based and a premixed calcium silicate-based sealer’s push-out bond strength with and without incorporation of chitosan nanoparticles: An in vitro investigation

Aim and Objectives: The aim of the study was to compare and evaluate the push-out bond strength (POBS) of epoxy resin-based and calcium silicate-based sealers with and without incorporating chitosan nanoparticles (CSNPs). Methodology: Eighty human mandibular premolars with a single canal were taken. A standard root length of 15 mm was established. Canals were instrumented with Neoendo files up to size 30, 4% and were irrigated with 5 ml of 2.5% NaOCl, and 5 ml of ethylenediaminetetraacetic acid 17%. Then, samples were obturated using the size 30, 4% gutta-percha, single-cone technique using respective sealers. For POBS, it was grouped as Group 1 Adseal, Group 2 CeraSeal, Group 3 Adseal + 2% wt/vol CSNP, and Group 4 CeraSeal + 2% wt/vol CSNP. Samples embedded in acrylic resin were sectioned transversely at 11 and 7 mm from the apex. Dislodgment resistance was calculated using a universal testing machine. The data were analyzed using a one-way ANOVA test, followed by Tukey’s post hoc analysis. The level of significance (P value) was set at P < 0.05. Results: At 7 mm from the apex, Group 4 (CeraSeal + 2% wt/vol CSNP) demonstrated significantly higher mean POBS. However, no significant difference was observed between Groups 1 (Adseal), Group 2 (CeraSeal), and Group 3 (Adseal + 2% wt/vol CSNP). At 11 mm from the apex, Group 2 (CeraSeal) and Group 4 (CeraSeal + 2% wt/vol CSNP) demonstrated significantly higher mean POBS. On comparison between POBS at 7 mm and 11 mm from the apex, the mean POBS at the 11 mm region from the apex was significantly higher in all study groups, which was statistically significant. Conclusion: Within the limitations of the study, it has been concluded that Group 4 (CeraSeal + 2% wt/vol CSNP) has better bond strength compared to the other groups.

Fracture Resistance of Space Maintainers Produced Using 3D Printable Materials.

This study aimed to evaluate the fracture resistance of space maintainers (SMs) produced using 3D-printable materials (metal, resin and polyetheretherketone [PEEK]) after thermal aging and compare them with conventional space maintainers. A standardised typodont model for paediatric dentistry was utilised, and band and loop space maintainers were designed digitally using computer-aided design (CAD) technology. Four groups were established: Conventional, 3D printed metal, 3D printed resin, and 3D printed PEEK. Fracture resistance was assessed after 10,000 thermal cycles, simulating oral conditions. Fracture tests were conducted using a universal testing machine, applying vertical force to the band and loop junction until fracture. Statistical analyses were performed using one-way ANOVA and the Tukey HSD test (P<0.05). Although the fracture resistance values showed that metal, resin, and PEEK 3D printed band and loop space maintainers can be acceptable clinically, the permanent resin may be preferable to printable material because of their aesthetic properties.

From quasi-static to dynamic: Experimental study of mechanical and fracture behaviour of epoxy resin

Epoxy polymers are extensively used in various engineering applications such as aerospace, defence, sports, automotive etc. This article focuses on the in-depth mechanical characterisation of EPOFINE®-1564, a Bisphenol-A-based liquid epoxy resin under various loading conditions. To predict the tensile and compressive behaviour of the representative epoxy resin, quasi-static experiments were performed in the range of 10−4 to 10−2s−1 on Universal testing machine (UTM) while the dynamic experiments were conducted using Split Hopkinson Pressure Bar (SHPB) for high strain rates (1136–2833 s−1). In this study, 3D Digital Image Correlation (DIC) was also used to evaluate the specimen's full-field displacement profile over a wide range of strain rates. Analysis of various mechanical properties such as elastic modulus, yield strength, and ultimate strength, revealed that the epoxy polymer is strain rate dependent within the considered strain rate range. For understanding the fracture behaviour, three-point bend (TPB) experiments were also carried out for both quasi-static (1–10 mm/min) as well as dynamic (10–15 m s-1) regimes. Dynamic fracture experiments were performed using the modified Hopkinson Pressure Bar (MHPB). The fracture toughness was determined through load vs crack mouth opening displacement (CMOD). Fracture toughness was found to increase with the displacement rate due to the significant plastic deformation under quasi-static range. Conversely, it was found to decrease under dynamic loading because of absence of plastic deformation resulting in brittle fracture. The fracture surface of the specimen was examined through a high magnification digital microscope.

Comprehensive evaluation of early shear bond strength and antimicrobial activity in orthodontic adhesives enhanced with salvadora persica oil

OBJECTIVES: This study investigates the mechanical properties and antimicrobial efficiency of orthodontic adhesive modified with Salvadora persica (SP) oil, including adhesive remnant index (ARI) and shear bond strength (SBS), specifically antimicrobial efficacy against Streptococcus mutans. METHODS: Forty freshly extracted human premolars were recruited. They were classified into four groups according to the concentration of SP oil added to Heliosit orthodontic adhesive where the control group was with no adhesive modification, alongside three experimental groups, wherein SP oil was integrated into the adhesive at concentrations of 1%, 3%, and 5% weight/weight, respectively. The tooth buccal surface was etched by phosphoric acid gel (37%). The orthodontic brackets utilized were standard stainless steel edgewise 22”. The brackets were bonded with Heliosit by Woodpecker LED light cure for 20 sec. The SBS was assessed using a universal testing machine, and ARI was inspected by a stereomicroscope at 20X magnification power. The antimicrobial activity against Streptococcus mutans was evaluated. The statistical analyses, analysis of variance (ANOVA), and Kruskal-Wallis and Duncan were performed where P ≤ 0.05. RESULTS: The findings indicated that among the experimental groups, the 3% SP oil group exhibited the highest mean SBS value, following closely behind the control group. Conversely, the mean SBS was lowest for the SP group with a 5% concentration. However, ANOVA and Kruskal-Wallis tests revealed no significant differences between groups (P ≥ 0.275, 0.069), respectively. Antimicrobial tests demonstrated a concentration-dependent antibacterial effect, the 5% group exhibiting the highest efficacy. CONCLUSION: Orthodontic adhesive modified with SP oil maintains favorable SBS while demonstrating antimicrobial effects against Streptococcus mutans.

Tensile testing in feline ventral abdominal coeliotomy closure with different sizes of polydioxanone suture material: a biomechanical study.

The aim of this study was to evaluate, in vitro, the load and type of failure of the sutured ventral abdominal fascia of cats with different sizes of suture material made of polydioxanone (PDX) (2-0, 3-0, 4-0, 5-0 USP). A total of 32 samples of the ventral abdominal wall from 16 cadaveric cats were harvested using an hourglass-shaped template. The samples were sectioned longitudinally along the linea alba and then sutured together in a continuous pattern using four different randomly assigned sizes of pdx suture material (2-0, 3-0, 4-0, 5-0 USP). A universal testing machine was used for linear distraction of the samples. The tensile strength and type of failure were recorded and analysed. Three types of failure were defined: suture material failure (S), suture line failure (T1) and failure of the abdominal wall further away from the linea alba (T2). The frequency of suture material failure decreased with increasing suture size. Suture size 5-0 failed due to a S failure in 6/8 samples, PDX 4-0 failed in 2/8 samples and PDX 3-0 failed in only 1/8 samples. However, PDX 2-0 failed due to only T1 or T2 failures, with both failures being almost equally represented. No statistically significant differences in the load to failure between PDX 2-0, 3-0 and 4-0 were noted (P >0.05). The risk of suture failure increased with decreasing suture size diameter. PDX 2-0 and 3-0 can be used without reservation for the closure of ventral midline coeliotomy in cats. Although there was no statistically significant difference between PDX 2-0, 3-0 and 4-0, PDX 4-0 showed a higher probability for suture breakage and should be used only after careful consideration of the patient while clinical evaluation is pending. Pdx 5-0 cannot be recommended as a safe suture size for this type of surgical closure.

Engineering fully quaternized (Dimethylamino)ethyl methacrylate-based photoresins for 3D printing of biodegradable antimicrobial polymers

Nowadays, medical devices or implants are widely used in the medical field to treat different diseases. However, bacterial infections are one of the significant problems associated with medical devices and are recognized as a concern in healthcare worldwide. Addressing this problem has driven the exploration of new materials with potent antibacterial properties. In this regard, quaternary ammonium compounds (QACs), which are organic salts with an alkane chain and a charged part of quaternary ammonium groups, came up with a potent antibacterial activity. Herein, we report for the first-time dimethylamino ethyl methacrylate (DMAEM) derived quaternary ammonium monomer and crosslinker to prepare photoresins for DLP (Digital light processing) 3D printing. The structure of the synthesized monomer and crosslinker was confirmed via FTIR (Fourrier Transform Infrared) and 1H NMR (Hydrogen Nuclear Magnetic Resonance) while the physicochemical properties of the 3D printed polymer were investigated using TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimeter) and UTM (Universal testing machine). By optimizing the printing conditions and monomer to crosslinker ratio, we can print high-resolution 3D-printed objects. Additionally, in vitro biodegradation, cytocompatibility, and hemocompatibility tests revealed that the printed polymers are biodegradable, cytocompatible, and hemocompatible in nature. More importantly, the printed polymers exhibited strong antibacterial activity against both gram-negative and gram-positive bacteria, suggesting their potential utility in personalized antibacterial medical devices.

Fracture resistance of postendodontic restoration using self-adhesive bioactive resin and a bulk-fill composite with or without resin-impregnated glass fibers: An in vitro study

Context: Due to advancements in adhesive technology and the introduction of fiber reinforcement, there has been a paradigm shift towards a more minimally invasive approach in coronal restoration of endodontically treated teeth. Aims: This research aimed to evaluate and compare fracture resistance of postendodontic restoration using a self-adhesive bioactive resin and a bulk-fill composite with or without resin-impregnated glass fibers. Materials and Methods: Mesio-occlusal-distal cavities were prepared on 80 extracted human maxillary premolars. Root canal treatment was completed following standard access cavity preparation. Then, the teeth were divided into two groups based on the composite used for postendodontic restoration. Group I: Bulk-fill composite (Tetric N-Ceram). Group II: Activa BioActive. Group I and Group II were then divided into two subgroups depending on fiber incorporation (n = 20). Subgroup IA: Bulk-fill composite. Subgroup IB: Bulk-fill composite with fiber incorporation. Subgroup IIA: Activa BioActive. Subgroup IIB: Activa BioActive with fiber incorporation. The force required to fracture the teeth was recorded using the universal testing machine. Statistical Analysis Used: Two-way ANOVA and Tukey’s multiple post hoc test. Results: Activa BioActive with fiber incorporation showed the highest mean fracture resistance (988.52N). Bulk-fill composite without fiber incorporation had the least mean fracture resistance (669.87N). Conclusions: Activa BioActive bulk-fill restorative material when used with the incorporation of resin-impregnated glass fibers can be a preferred material of choice for restoring endodontically treated teeth.

Effects of Bi2O3–CuO addition on the dielectric properties of MgO–TiO2(w) ceramics sintered at low temperatures

Herein, MgO–12 % TiO2(w) ceramics with different contents of Bi2O3–CuO sintering aid were prepared using a solid-state method. The effects of the sintering aid content on the sintering temperature and the dielectric and mechanical properties of the ceramics were studied. The material was characterized using scanning electron microscopy and X-ray diffraction and Precision LCR tester and universal testing machine and Archimedes drainage method. When the Bi2O3–CuO content was less than 9 wt%, the ceramic sample has higher dielectric properties. When the Bi2O3–CuO content was greater than 9 wt%, the dielectric properties will deteriorate. This is because Bi2O3 participates in the chemical reaction between MgO and TiO2, forming a high dielectric loss Bi4Ti3O7 phase. At high temperatures, Cu2+ can easily change valence to Cu+, promoting oxygen vacancies and increasing dielectric loss in ceramic samples. The introduction of Bi2O3–CuO produces new MgTiO3, Mg2TiO4, and Bi4Ti3O12 phases in the sample structure, resulting in a structure in which the MgO grains in the sample are surrounded by the new phases that appear around them. This structure fills the pores, increases density, enhances mechanical properties. The dielectric properties of the ceramics were the when the sintering temperature was 1050 °C, and the Bi2O3–CuO content was 3 wt%. The dielectric constant and dielectric loss were 11.19 and 1.17 × 10−4, respectively. The bending strength of the ceramic sample increased from 138.72 MPa to 179.64 MPa when the Bi2O3–CuO content was increased from 3 wt% to 15 wt%. The Bi2O3–CuO sintering aid enables MgO to be better applied in ceramic substrates.

Evaluating the Impact of Oxidation Heat Treatment and Dual Opaquing Techniques on Enhancing Metal-Ceramic Bond Strength.

This research aims to assess the impact of oxidation heat treatment (OHT) and dual opaquing techniques on enhancing the bond strength between metal and ceramic. Eighty rectangular patterns with dimensions of 0.5x3x25 mm (according to ISO 9693-2012) were fabricated in a custom-made silicon mold by using auto-polymerized pattern resin material. These rectangular patterns were cast using base metal alloys. The samples were split into two primary groups: group A, subjected to OHT, and group B, without oxidation treatment. Each primary group was then split up into subgroups according to the application of single layers (group A1, B1)or double layers (group A2, B2) of opaque porcelain.After pre-surface treatment and Ceramco 3 paste opaque application, dentin porcelain (Ceramco 3) wasapplied to the mid-region of the samples, followed by firing to achieve a standardized thickness. Flexural strength determination was conducted via a three-point bend test performed on the universal testing machine (UTM) (Instron Corp., Model 2519-107, USA), adhering to ISO standard 9693. Post-testing failure types were analyzed by morphological assessment of debonding surfaces via a scanning electron microscope (SEM). The statistical analysis was performed with SPSS version 16, incorporating ANOVA for intergroup analysis and independent t-tests for intragroup comparisons. Group A2 exhibited the highest mean flexural bond strength (P<0.05) at 41.85 MPawhen compared to group A1 at 37.60 MPa, group B2 at 35.47 MPa, and group B1 with the least mean flexural bond strength at 30.41 MPa. SEMobservations revealed cohesive bond failure for groups A1, A2, and B2and adhesive bond failure for groupsB1. It is evident that OHT and opaquing technique are important factors in determining the bond strength of ceramo-metal restorations. When combined, these techniques greatly increase the overall success and durability of metal-ceramic restorations, underscoring their significance in contemporary dental prostheses.

Effect of resin cement viscosities and surface roughness on shear bond strength of conditioned polymer infiltrated ceramic network

BackgroundHybrid ceramics bonding with the dentinal substrate is crucial for clinical success and longevity. To enhance adhesion, the surface of ceramic restorations is modified through various conditioning techniques AimEffect of Different Surface Conditioners Erbium-doped yttrium aluminum garnet (ER: YAG) laser and Low-level laser therapy (LLLT) activated Methylene blue (MB) on the surface roughness (Ra) and shear bond strength (SBS) of Polymer infiltrating ceramic network (PICN) discs bonded using different viscosity resin cement before and after thermal aging. Material and MethodsOne hundred and fifty human central incisors and one hundred and fifty-three PICN discs were prepared. PICN discs were randomly allocated into three groups based on the surface conditioning(n = 51) Group 1:10 % HF acid-S, Group 2: LLLT (MB), and Group 3: Er: YAG laser. Following conditioning Ra scores of ten samples were performed. Surface topography of samples was performed using a scanning electron microscope (SEM). Bonding of forty PICN discs from each conditioning group was performed with high (A) or low viscosity (B) dual-curing resin cement (n = 20 each). Each subgroup was divided into two cohorts and subjected to varying storage conditions. The SBS test and failure mode analysis were performed using a universal testing machine and stereomicroscope. Descriptive statistics of SBS and Ra for each group were analyzed using ANOVA and Tukey post hoc tests. HF acid-S attained the highest Ra scores. ResultsGroup 1A (HF-S+HIGH) samples achieved the highest SBS values at baseline. Group 3A, on the other hand, displayed the lowest bond score (Er: YAG laser+HIGH) after thermal aging. Intergroup comparison analysis at baseline unveiled that Group 1A and Group 1B (HF(S) + LOW) displayed no significant difference in their bond strength scores (p>0.05). Following artificial aging, it was observed that Group 2A (LLLT (MB) + HIGH) and Group 3A (Er:YAG laser + HIGH) ) presented comparable SBS(p > 0.05). Thermal aging decreased SBS significantly in all groups. PICN conditioned with HF-S results in high surface roughness. ConclusionPICN conditioned with HF acid with silane and bonded with low-viscosity resin cement to the dentinal substrate is preferable. Aging influences SBS.

Evaluation of compressive and diametral tensile strength of novel bioactive material with conventional glass ionomer cement and silver amalgam: An in vitro study

Aim: The aim of this study was to compare the compressive and tensile strength of two different brands of conventional glass ionomer cement (GIC), with new zirconia-reinforced GIC and silver amalgam. Materials and Methodology: Eighty specimens with 20 samples in each group were prepared (Group 1-Fuji IX GIC, Group 2-FX-II Shofu GIC, Group 3-Amalgam, and Group 4-Zirconia-reinforced glass ionomer [Zirconomer]) for compressive strength (CS) using cylinder molds with dimensions 6.0 mm diameter × 12.0 mm height. Eighty specimens using cylinder molds with dimensions 6.0 mm diameter × 3.0 mm height were prepared for testing diametral tensile strength (DTS). CS test was carried out using Micro Universal Testing Machine (Mecmesin, PPT Group, UK) having a crosshead speed of 1.0 mm/min. DTS was determined using Instron universal testing machine at a crosshead speed of 1.0 mm/min. The data were submitted to two-way analysis of varianceand post hoc Tukey tests (alpha = 0.05). The mean CS value was more for Group III (256.2), followed by Group IV (181.2 Megapascals [MPa]), Group II (129.8 MPa), and the least was Group I (117.9 MPa). Result: The mean DTS value was high in Group III (73.7 MPa), followed by Group IV (58.0 MPa), Group II (36.0 MPa), and the least was seen in Group I (23.2 MPa). Conclusion: It can be concluded that although Zirconomer has mechanical properties greater than that of unmodified GICs, additional studies are essential to evaluate its long-time ability.

Mechanical property and cracking mechanism of Cr-coated Zr alloy under tensile and compressive loading

Cr coatings are considered as the most promising candidate materials for accident-tolerant fuel cladding coatings. In combination with optical microscopy, focus ion beam, energy dispersive spectrum and universal testing machine, the effect of Cr coating on hoop tensile and compressive mechanical properties of Zr alloy was studied and the underlying cracking failure mechanism of Cr coating was revealed. The results indicate that Cr coating slightly increases tensile/compressive yield strength and tensile strength compared with those of uncoated Zr alloy. This is attributed to high hardness/elastic modulus of Cr coating. Interrupted hoop tensile and compressive tests show that Cr coating cracking concentrates in the range of 0-30°. Further, crack initiation of the coating occurs either at the surface or at the interface between Cr coating and the matrix. Compared with the former, the latter is dominant cracking mode, irrespective of tensile and compressive loading. In lights of the advanced microstructural analysis, one possible reason, i.e., the existence of nano-scaled Al-enriched loose layer between the interface, in which nano-cracks and voids exist, is proposed to explain the interfacial cracking. The result indicates that the optimization of the interfaces can improve the resistance of coating failure. In addition, crystallographic study demonstrates that the crack propagation in the Cr coating is along the high-angle grain boundaries with the misorientation of 50°.

Effect of cooling temperature on microstructure and mechanical properties of Nb microalloyed hot-rolled rebar

In this study, the Gleeble-3800 thermal simulation tester was used to simulate various cooling temperature processes for two groups of rebar. Then, the microstructure, precipitation, and mechanical properties of the rebars were characterized using SEM (scanning electron microscopy), EBSD (electron backscatter diffraction), HRTEM (high resolution transmission electron microscopy), and MST810 (universal tensile testing machine). The effect of cooling temperature on the microstructure and mechanical properties was systematically investigated. The results showed that reducing the cooling temperature from 750 °C to 600 °C decreased the ferrite grain size in 0.032 wt % Nb rebar to 7.03 ± 1.5 μm, compared to the 0 wt% Nb rebar. In addition, the pearlite lamellar spacing was refined to 0.103 ± 0.5 μm, and the average particle size of elliptical Nb-rich composite carbides was 9 nm. The tensile strength and yield strength reached 795 ± 9 MPa and 638 ± 8 MPa, respectively, with an elongation after fracture of 17.78 ± 1.0 %. The fracture surface exhibited a dimple morphology.

Prevalence and spectrum of germline pathogenic variants in cancer susceptibility genes among mexican patients with exocrine pancreatic cancer

BackgroundAlthough universal germline genetic testing is recommended for patients with exocrine pancreatic cancer (PC), access to genetic testing remains limited in low- and middle-income countries. This study aims to narrow the gap in our understanding of the spectrum of germline pathogenic and likely pathogenic variants (PVs) in cancer susceptibility genes in the Mexican population. MethodsThe landscape of PVs in cancer susceptibility genes was identified by next-generation sequencing multigene panel assays among patients with PC who were enrolled in the Clinical Cancer Genomics Community Research Network prospective registry in Mexico City. ResultsFrom August 2019 to April 2023, 137 patients underwent genetic testing. The median age at diagnosis was 60 years (range 36–85), 58.4 % were women, and 38.7 % were metastatic at diagnosis. The frequency of germline PVs was 16 % (n = 22): ATM 36.4 % (n = 8), CDKN2A/p16INK4A 27.3 % (n = 6), BRCA2 9.1 % (n = 2), PALB2 9.1 % (n = 2), CHEK2 9.1 % (n = 2), TP53 4.5 % (n = 1), and NF1 4.5 % (n = 1). Additionally, 2 carriers of monoallelic germline variants in MUTYH were identified. No significant differences were observed between carriers and non-carriers in terms of family history of pancreatic cancer. ConclusionsWe identified a significant frequency of actionable germline PVs in Mexicans with PC, wherein the majority were in a broad spectrum of genes associated with the homologous recombination DNA repair mechanism. Most pancreatic cancer associated PVs were detected in non-BRCA genes, so our findings support the recommendation of multigene panel testing for genetic cancer risk assessment of Mexican individuals with PC.

The effect of different clinical recycling methods on load deflection properties of super-elastic and thermal nickel–titanium orthodontic arch wires: A comparative assessment

INTRODUCTION: Repeated clinical use of arch wires requires sterilization and may result in alteration of the properties of the wires as they get subjected to corrosion and cold working. Therefore, the present study aimed to assess the effects of different clinical recycling methods on the load-deflection properties of super-elastic and thermal nickel–titanium orthodontic arch wires. MATERIALS AND METHODS: A total of 50 0.014” round nickel–titanium orthodontic wires [Group I: super-elastic nickel–titanium (n = 25) and Group II: thermal nickel–titanium wires (n = 25)] were tested for changes in their load deflection properties after three different recycling methods, that is, dry heat sterilization, autoclave, and cold sterilization. For each group, five wires as received from the manufacturer were taken as control (T0), and the rest of the 20 wires were placed intra-orally for a duration of one cycle of clinical use (T1). Five wires out of these were subjected to 3-point bending tests, and the rest of the wires were subjected to different recycling methods. Load deflection properties of recycled wires were measured with an Instron universal testing machine. The results were tabulated, and the data were analyzed by analysis of variance (ANOVA) with the Tukey post hoc test. RESULTS: Statistically, no significant difference was found in the super-elastic group between samples recycled by dry heat, autoclave, and cold sterilization when compared with as-received super-elastic NiTi up to 2.5 mm of deflection. A highly significant difference was found between as-received thermal NiTi group (83.51 ± 6.49 N/mm) and samples recycled by dry heat (53.73 ± 4.72 N/mm), autoclave (45.38 ± 4.37 N/mm), and cold sterilization (48.44 ± 3.12 N/mm) at 0.5 mm of deflection. CONCLUSION: Among thermal NiTi, any of the sterilization methods could opt at all deflections. For super-elastic NiTi, at higher deflections or in cases of crowding of more than 2.5 mm, cold sterilization should be the method of choice, whereas any sterilization method can be used at deflections less than 2.5 mm.

Bioremediation of uranium enriched coal fly ash based on microbially induced calcite precipitation

Coal fly ash (CFA) is an essential raw material in brickmaking industry worldwide. There are some coal mines with a relatively high content of uranium (U) in the Xinjiang region of China that are yet understudied. The CFA from these coal mines poses substantial environmental risks due to the concentrated uranium amount after coal burning. In this paper, we demonstrated a calcifying ureolytic bacterium Halomonas sp. SBC20 for its biocementation of U in CFA based on microbially induced calcite precipitation (MICP). Rectangle-shaped CFA bricks were made from CFA using bacterial cells, and an electric testing machine tested their compressive strength. U distribution pattern and immobility against rainfall runoff were carefully examined by a five-stage U sequential extraction method and a leaching column test. The microstructural changes in CFA bricks were characterized by FTIR and SEM-EDS methods. The results showed that the compressive strength of CFA bricks after being cultivated by bacterial cells increased considerably compared to control specimens. U mobility was significantly decreased in the exchangeable fraction, while the U content was markedly increased in the carbonate-bound fraction after biocementation. Much less U was released in the leaching column test after the treatment with bacterial cells. The FTIR and SEM-EDX methods confirmed the formation of carbonate precipitates and the incorporation of U into the calcite surfaces, obstructing the release of U into the surrounding environments. The technology provides an effective and economical treatment of U-contaminated CFA, which comes from coal mines with high uranium content in the Xinjiang region, even globally.

Prediction of flow stresses for a typical Nickel-Based superalloy during hot deformation based on constitutive equation

Abstract Utilizing the Gleeble-3500 thermal simulation testing machine, a series of isothermal constant strain rate thermal compression tests were executed to study the high-temperature rheological properties of the GH4169 alloy. These tests were carried out under deformation temperatures between 900°C and 1100°C, with strain rates from 0.001 to 1 s−1, and involved a deformation of 60%. The results reveal that the peak stress of the GH4169 alloy decreases as the temperature increases, and the strain rate decreases during hot deformation. The activation energy for thermal deformation is calculated to be 806.39 kJ/mol. Through regression analysis and polynomial fitting of true stress-strain curves from thermal compression tests, an Arrhenius constitutive equation integrating strain compensation for high-temperature deformation was established. The model exhibits an average relative error of 8.86% between predicted and experimental values, indicating the model’s good accuracy in predicting the alloy’s rheological behavior during thermal deformation. By adjusting the strain rate and deformation temperature, this model can be utilized to control the stress level in the hot working process.

The flow stress prediction of TiB2/2024 aluminum matrix composites based on modified Arrhenius model and gene expression programming model

The high temperature flow data of TiB2/2024 aluminum matrix composites (referred to as TiB2/2024 alloy) was investigated using a Gleeble-3500 thermal simulation testing machine. The experiments were conducted at various deformation temperatures (573 K, 623 K, 673 K, and 723 K), strain rates (0.01s−1, 0.1s−1, 1s−1, and 10s−1), and a maximum deformation of 60%. By comprehensively accounting for the deformation conditions, the relationships between the material parameters α, n, S, f of TiB2/2024 alloy and the deformation temperature, strain, and strain rate were determined, leading to the modification of the Arrhenius model. A constitutive model for TiB2/2024 alloy was constructed using the Gene expression programming (GEP) approach. The flow stress of TiB2/2024 alloy during the compression process was predicted using both the modified Arrhenius model and the GEP model. The statistical analysis was performed to evaluate the prediction accuracy of the two models, and the extended stress-strain data was implemented in finite element simulations of the hot compression process. The results indicate that the flow stress of TiB2/2024 alloy is significantly affected by the strain rate and temperature during the deformation process. The flow stress decreases with increasing temperature and increases with increasing strain rate. Both the modified Arrhenius model and the GEP model can effectively predict the alloy's flow stress. However, the modified Arrhenius model exhibits greater prediction accuracy than the GEP model.

The deltotrapezial fascia stabilizes the AC-Joint and its reconstruction restores the horizontal stability in AC-joint separations—a biomechanical comparison

BackgroundVarious techniques are available for the reconstruction of acromioclavicular joint (ACJ) dislocations, with the main focus being on restoration of the AC capsule or coracoclavicular (CC) ligaments. Recent research has underlined the significance of the deltotrapezial fascia (DTF) and related muscles as dynamic stabilizers of the ACJ. HypothesisReconstruction of the DTF increases the stability of the ACJ in the horizontal plane more than a complete transection of the fascia, while not restoring the stability of the native state. MethodsFive pairs of human cadaveric shoulders including the torsos were included in the study and underwent cyclic anterior-posterior loading using an electromechanical testing machine. The shoulders were put into three groups: group N (n = 10): native ACJ; group T (n = 10): ACJ with transected DTF; group R (n = 10): ACJ with reconstruction of the DTF after transection. The dislocation was recorded with an 3D optical measuring system. ResultsGroup N showed a mean horizontal displacement of 2.94 mm (± 1.26), group T showed a mean anterior displacement of 3.33 mm (± 1.37) and group R showed a mean anterior displacement of 2.95 mm (± 1.08). The mean anterior displacement for group T was significantly higher after every measured number of cycles compared with groups N and R. There was no significant difference in mean anterior displacement between groups N and R. ConclusionThe transection of the DTF results in significantly reduced stability in the horizontal plane of the ACJ. A reconstruction of the DTF restores the stability of the native ACJ in the horizontal plane. Further clinical and biomechanical investigations should focus on reconstruction techniques of the DTF.