Search Results (345)

This paper presents the activities carried out to improve the quality of certain composite structures by manufacturing them with the assistance of an ultrasonic field. As many composite materials use epoxy resins as base materials, an important problem was noted, namely their high curing time, as well as the problems of lack of adhesion and delamination, which are also known and experienced in the case of composite structures made with metallic materials as a support. The application of an ultrasonic field can successfully solve both problems. To demonstrate this improvement, the manufacturing of cylinders used in braking stands in the automotive industry was considered the main application. The proposed technology will be then extended to conveyor belts or to the manufacturing of other high-adhesion surfaces. This article presents the traditional method and the new ultrasonic field deposition technology. The design of the ultrasonic system is presented based on an analytical calculation, FEM modal analysis, followed by the construction of the ultrasonic system, as well as by bending tests and infrared thermography to demonstrate the advantages of presented method. Full article

Conventional non-intumescent fire-resistive coatings often require excessive thickness and exhibit poor adhesion. To address these limitations, this study developed a novel geopolymer-based aerogel composite (GBAC) coating. The effects of aerogel content, water-to-binder (W/B) ratio, curing age, latex powder, basalt fibers, and an expansive agent on the physical and mechanical properties of GBAC were systematically investigated. The results have indicated that increasing the aerogel content and W/B ratio reduces the dry density, thermal conductivity, and compressive strength. Both basalt fibers and expansive agent significantly inhibit drying shrinkage while enhancing tensile and tensile bonding strength. Although latex powder shows a negligible effect on shrinkage reduction, it effectively improves tensile and bonding strength. The incorporation of 2.5% of latex powder, 1.0% of basalt fibers, and 4.0% of expansive agent results in a remarkable reduction in shrinkage strain by 85.23%, an increase in tensile strength by 90.93%, and an enhancement in tensile bonding strength by 64.89%. GBAC coatings with thicknesses of 20 and 25 mm can extend thermal insulating efficiency of steel plates by 84 and 108 min and make steel beams satisfy the requirements of Classes II and I fire resistance, respectively. Full article

Background/Objectives: The clinical application of CAD/CAM restorative materials continues to evolve due to increasing demand for aesthetic, durable, and minimally invasive indirect restorations. Hybrid nanoceramics, such as Grandio disc (VOCO GmbH, Cuxhaven, Germany), are increasingly used in indirect restorative dentistry due to their favourable combination of mechanical strength, polishability, wear resistance, and bonding potential. One challenge associated with adhesive protocols for CAD/CAM materials lies in achieving durable bonds with resin cements. Extensive post-polymerization during fabrication reduces the number of unreacted monomers available for chemical interaction, thereby limiting the effectiveness of traditional adhesive strategies and necessitating specific surface conditioning approaches. This study aimed to evaluate, in a preliminary, non-inferential manner, the influence of several combined conditioning protocols on surface micromorphology, elemental composition, and descriptive SBS trends of a CAD/CAM hybrid nanoceramic. This work was designed as a preliminary pilot feasibility study. Due to the limited number of specimens (two discs per protocol, each providing two independent enamel bonding measurements), all bond strength outcomes were interpreted descriptively, without inferential statistical testing. This in vitro study investigated the effects of various surface conditioning protocols on the adhesive performance of CAD/CAM hybrid nanoceramics (Grandio disc, VOCO GmbH, Cuxhaven, Germany) to dental enamel. Hydrofluoric acid (HF) etching was performed to improve adhesion to indirect resin-based materials using two commercially available gels: 9.5% Porcelain Etchant (Bisco, Inc., Schaumburg, IL, USA) and 4.5% IPS Ceramic Etching Gel (Ivoclar Vivadent, Schaan, Liechtenstein), in combination with airborne-particle abrasion (APA), silanization, and universal adhesive application. HF may selectively dissolve the inorganic phase, while APA increases surface texture and micromechanical retention. However, existing literature reports inconsistent results regarding the optimal conditioning method for hybrid composites and nanoceramics, and the relationship between micromorphology, elemental surface changes, and adhesion remains insufficiently clarified. Methods: A total of ten composite specimens were subjected to five conditioning protocols combining airborne-particle abrasion with varying hydrofluoric acid (HF) concentrations and etching times. Bonding was performed using a dual-cure resin cement (BiFix QM) and evaluated by shear bond strength (SBS) testing. Surface morphology was examined through environmental scanning electron microscopy (ESEM), and elemental composition was analyzed via energy-dispersive X-ray spectroscopy (EDS). Results: indicated that dual treatment with HF and sandblasting showed descriptively higher SBS, with values ranging from 5.01 to 6.14 MPa, compared to 1.85 MPa in the sandblasting-only group. ESEM revealed that higher HF concentrations (10%) created more porous and irregular surfaces, while EDS indicated an increased fluorine presence trend and silicon reduction, indicating deeper chemical activation. However, extending HF exposure beyond 20 s did not further improve bonding, suggesting the importance of protocol optimization. Conclusions: The preliminary observations suggest a synergistic effect of mechanical and chemical conditioning on hybrid ceramic adhesion, but values should be interpreted qualitatively due to the pilot nature of the study. Manufacturer-recommended air abrasion alone may provide limited adhesion under high-stress conditions, although this requires confirmation in studies with larger sample sizes and ageing simulations. Future studies should address long-term durability and extend the comparison to other hybrid CAD/CAM materials and to other etching protocols. Full article

The invention concerns a screw-driven shredder for solid photopolymer resin, designed for both terrestrial use and prospective deployment in microgravity environments. The system addresses the need for efficient recycling of cured photopolymer waste generated by stereolithography (SLA) 3D printing—a process not yet implemented in orbit, but envisioned as part of future closed-loop additive manufacturing systems aboard space stations or lunar habitats. The proposed device is a compact, hermetically sealed mechanical unit composed of ten subassemblies, featuring two counter-rotating screw shafts equipped with carbide milling inserts arranged helically to achieve uniform and controlled fragmentation of solid SLA residues. The shredding process is supported by a pressurized inert fluid circuit, utilizing carbon dioxide (CO₂) as a cryogenic working medium to enhance cutting efficiency, reduce heat accumulation, and ensure particle evacuation under microgravity conditions. Studies indicate that CO₂-assisted cooling can reduce tool-tip temperature by 10–30 °C, cutting forces by 5–15%, and electrical power consumption by 5–12% while extending tool life by up to 50%. This invention thus provides a key component for a future in situ photopolymer recycling loop in space while also offering a high-efficiency shredding solution for Earth-based photopolymer waste management in additive manufacturing. Full article

An alternative conductive ink based on carbon nanotubes (CNTs) was developed using a platinum-catalyzed silicone elastomer and isopropyl alcohol (IPA). The inclusion of IPA in the conductive CNT ink facilitated the optimization of its mechanical strength, electrical conductivity, and viscosity. Compared to conventional silicone rubber-based conductive polymers that often solidify in a few hours at room temperature or with heating, this liquid composite of CNT particles and IPA exhibited a prolonged duration of up to several months in a hermetic environment, maintaining chemical stability even with the elastomer and its curing agent. The gradual evaporation of IPA initiates a well-known cross-linking process, leading to stretchability and electrical conductivity derived from the silicone elastomer and CNT particles, respectively. The relationship between the mechanical strength and electrical conductivity of the hardened conductive CNT ink was studied, which helped determine the optimized concentration of CNT particles in the conductive CNT ink. Subsequently, a piezoresistive sensor was designed, fabricated, and evaluated. The conductive CNT ink-based piezoresistive sensor showed high sensitivity and good repeatability with respect to a wide range of external forces. The effect of the concentration of CNT particles on the viscosity of the conductive CNT ink was also investigated, providing a better understanding of the entanglement of CNT particles within the silicone elastomer. A coating test using the conductive CNT ink with a paper cutting machine demonstrated its potential for adaptation to various printing techniques, including screen printing. The proposed conductive CNT ink, characterized by a simple chemical composition, facile fabrication process, use of non-toxic elements, high electrical conductivity, and stretchability, combined with an extended duration, has the potential to be applied for multiple purposes, such as various types of flexible and wearable electronics. Full article

Monitoring the curing process of concrete remains a challenging and critical aspect of modern construction, often hindered by labour-intensive, invasive, and inflexible methods. The primary aim of this study is to develop an integrated IoT-enabled platform for automated, real-time monitoring of concrete curing, using a combination of LoRa-based sensor networks and an LTE-M backhaul. The resulting ConMonity system employs embedded multi-sensor nodes—capable of measuring strain, temperature, and humidity–connected via an energy-efficient, TDMA-based LoRa wireless protocol to an LTE-M gateway with cloud-based management and analytics. By employing a robust architecture with battery-powered embedded nodes and adaptive firmware, ConMonity enables multi-modal, multi-site assessments and demonstrates stable, autonomous operation over multi-modal, multi-site assessment and demonstrates stable, autonomous operation over multi-month field deployments. Measured data are transmitted in a compact binary MQTT format, optimising cellular bandwidth and allowing secure, remote access via a dedicated mobile application. Operation in laboratory construction environments indicates that ConMonity outperforms conventional and earlier wireless monitoring systems in scalability and automation, delivering actionable real-time data and proactive alerts. The platform establishes a foundation for intelligent, scalable, and cost-effective monitoring of concrete curing, with future work focused on extending sensor modalities and enhancing resilience under diverse site conditions. Full article

Geopolymers, as sustainable alternatives to traditional cementitious materials, offer superior mechanical and durability properties; however, they face challenges with rapid setting, particularly in fly ash–slag systems. Retarders play a crucial role in tailoring the setting behavior and workability of geopolymers, especially in applications where extended setting time or placement under challenging conditions is required. Geopolymers, unlike traditional Portland cement, undergo a rapid alkali-activation process involving dissolution, polymerization, and hardening of aluminosilicate materials. This can lead to very short setting times, particularly at elevated temperatures. In this scenario, the present study investigates the effect of different retarders-including cellulose, starch, borax, and their different combinations the setting time. The effectiveness of a retarder depends on the geopolymer formulation, including the type of precursor, activator, and curing conditions. The initial and final setting times improved by the addition of retarders, whereas most of the retarders had a negative effect on compressive strength. The optimum retarder combination was starch and borax, with a remarkable improvement in setting time and a positive result on the compressive strength, while maintaining reasonable workability. The retarder was equally effective under both ambient and oven-cured conditions and for different mix proportions of fly ash (FA) and slag, indicating that its effectiveness depends only on the type of precursors used. The study reveals the use of borax along with cellulose- or sugar-based compounds, which balances the reaction kinetics, resulting in balanced mechanical characteristics. Full article

The study presented an analysis of the behaviour of cellular structures under bending, produced using the PolyJet Matrix (PJM) additive manufacturing method with photopolymer resin. Structures with regular cell geometry were designed to achieve a balance between stiffness, weight reduction, and energy absorption capacity. The aim of this study was to investigate the influence of unit-cell topology (quasi-similar, spiral, hexagonal honeycomb, and their core–skin hybrid combinations) on the flexural properties and deformation mechanisms of PolyJet-printed photopolymer beams under three-point bending. Additionally, all cellular configurations were fully infiltrated with a low-modulus platinum-cure silicone to evaluate the effect of complete polymer–elastomer interpenetration on load-bearing capacity, stiffness, ductility, and energy absorption. All tests were performed according to bending standard on specimens fabricated using a Stratasys Objet Connex350 printer with RGD720 photopolymer at 16 µm layer thickness. The results showed that the dominant failure mechanism was local buckling and gradual collapse of the cell walls. Among the silicone-filled cellular beams, the QS-Silicone configuration exhibited the best overall flexural performance, achieving a mean peak load of 37.7 ± 4.2 N, mid-span deflection at peak load of 11.4 ± 1.1 mm, and absorbed energy to peak load of 0.43 ± 0.06 J. This hybrid core–skin design (quasi-similar core + spiral skin) provided the optimum compromise between load-bearing capacity and deformation capacity within the infiltrated series. In contrast, the fully dense solid reference reached a significantly higher peak load of 136.6 ± 10.2 N, but failed in a brittle manner at only ~3 mm deflection, characteristic of UV-cured rigid photopolymers. All open-cell silicone-filled lattices displayed pseudo-ductile behaviour with extended post-peak softening, enabled by large-scale elastic buckling and silicone deformation and progressive buckling of the thin photopolymer struts. The results provided a foundation for optimising the geometry and material composition of photopolymer–silicone hybrid structures for lightweight applications with controlled stiffness-to-weight ratios. Full article

Advances in systemic therapy for gastrointestinal malignancies have opened the door for surgical resection of tumors previously deemed unresectable. Of these tumors, gallbladder cancer has a particularly poor prognosis due to the aggressive nature of the disease. The preferred systemic therapy regimen for gallbladder cancer has progressed from single-agent chemotherapy to multi-agent therapy including immune checkpoint inhibitors, with additional targeted therapies currently under investigation. These advancements have provided patients with historically unresectable tumors with a bridge to surgical resection and a hope of extended survival or cure. Surgical options for locally advanced tumors have expanded, and experienced centers perform a variety of operations to achieve resection with negative margins, including extended liver resection, bile duct resection, vascular reconstruction, and adjacent organ resection. There is also growing evidence that patients with Stage IV disease may benefit from resection of their primary tumors and metastases. This review outlines the current treatment practices for patients with locally invasive and metastatic gallbladder cancer as well as emerging treatment options. Full article

Bone cements based on polymethyl methacrylate (PMMA) remain the clinical standard for joint replacement and vertebral augmentation but suffer from several major challenges. These include excessive stiffness compared with cancellous bone, lack of resorption and osteoconductivity, and thermal necrosis during curing. Calcium phosphate cements (CPCs) are bioactive and resorbable but tend to exhibit low mechanical strength, poor injectability and brittle fracture. The work reported herein developed an injectable composite bone cement by combining spherical, porous, sintered β-tricalcium phosphate (β-TCP) particles with a cyanoacrylate adhesive. The β-TCP granules provided bioactivity and a favorable microarchitecture while the cyanoacrylate ensured strong adhesion and rapid setting. Ion substitution with Mg, Na and Si was found to modify the surface acidity of the material while also inhibiting cyanoacrylate polymerization, thereby extending the setting time and lowering the exotherm temperature. This composite exhibited high chemical stability, smooth injectability and early surface reactivity indicative of osteoconductivity. The compressive strength of the material stabilized at approximately 40 MPa and so exceeded that of cancellous bone. This new material also showed ductility, energy absorption and superior impact resistance, although its tensile and fatigue resistance remained limited. Importantly, the composite provided strength comparable to that of PMMA in cemented models during fixation tests and significantly outperformed CPCs in cementless tibial tray fixation experiments. These findings demonstrate that the present β-TCP/cyanoacrylate cement bridges the gap between PMMA and CPCs by combining injectability and mechanical reliability with bioactivity. This cement is therefore a promising next-generation option for minimally invasive osteoporotic fracture treatment and revision arthroplasty. Full article

Additive manufacturing (AM) offers precision and efficiency in occlusal splint fabrication; however, the combined influence of build orientation and post-curing duration on the mechanical performance of splint resins remains insufficiently explored. This in vitro experimental study evaluated the effects of three build orientations (0°, 45°, and 90°) and three post-curing protocols (uncured, standard, and extended) on the flexural strength (FS), flexural modulus (FM) and Vickers hardness number (VHN) of a Class IIa biocompatible occlusal splint resin (NextDent Ortho Rigid). A total of 180 specimens were fabricated using a vat polymerization-type 3D printing system. Statistical analyses were conducted using one-way analyses of variance and Tukey’s tests at a significance level of α = 0.05. Both build orientation and post-curing duration significantly affected FS and VHN (p < 0.001). The combination of 45° build orientations and extended post-curing produced the highest FS (169.76 MPa) and FM (7502.17 MPa), exceeding values typically reported for 3D-printed splints, while the 90° orientation with extended curing achieved the highest VHN (21.88). Hardness gains, however, plateaued beyond standard curing, indicating a trade-off between strength and surface hardness. These results demonstrate that print orientation and post-curing time are decisive parameters in optimizing the mechanical performance of 3D-printed occlusal splints. For high-load clinical applications such as bruxism, prioritizing flexural strength over surface hardness may improve appliance longevity, supporting 45° orientation with extended curing as an evidence-based manufacturing approach. Full article

Fine-grained tailings pose significant challenges for direct resource utilization applications such as tailings dam construction and backfill preparation due to their fine particle size, high specific surface area, and extended natural consolidation period. This investigation examined the mechanical properties of cemented fine-grained tailings under varying mix proportions and conditions. The cemented tailings were prepared using raw tailings material containing approximately 95% particles sized 0–74 μm. A comprehensive experimental program comprising 36 flexural tests and uniaxial compressive tests was conducted, with cement–sand ratio (A), curing age (B), and specimen immersion time (C) as controlled variables. The strength development mechanism was characterized through XRD and SEM, while mechanical performance data were systematically analyzed using range analysis, ANOVA, and regression analysis. Key findings demonstrate that ① the flexural strength of cemented tailings ranged from 0.43 to 2.07 MPa, with compressive strength varying between 3.02 and 12.52 MPa; ② both compressive and flexural strengths exhibited positive correlations with factors A and B, while showing negative correlation with factor C; ③ hydration products consisted primarily of C-S-H gels and zeolite-like phases, whose interwoven microstructure collectively ensured specimen integrity; ④ all three factors significantly influenced mechanical strengths with identical hierarchical impact: A > B > C; and ⑤ a comprehensive predictive model based on ternary quadratic polynomial regression was developed and validated. These results provide a scientific foundation for sustainable resource utilization of fine-grained tailings as solid waste materials. Full article

Background: Clear aligners have become a common alternative to fixed appliances for tooth movement, and thermoplastic retainers hold the outcome. The prolonged intraoral contact of these devices has made the materials a focus of biocompatibility research. Objectives: This paper aims to summarize laboratory evidence on the biocompatibility of clear aligners and thermoplastic retainers. Materials included thermoformed polyethylene terephthalate glycol-modified (PETG), multilayer polyurethane, and directly printed resins. Primary outcomes were cytotoxicity, endocrine activity, and chemical or particle release. Methods: We systematically searched PubMed, the Cochrane Library, and Google Scholar through 31 May 2025, and we followed the PRISMA 2020 statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We applied predefined eligibility criteria. Two reviewers screened records and extracted data in duplicate, including study design, extraction conditions, surface-area-to-volume ratio (SA/V), cell models, endpoints, and analytical sensitivity as the limit of detection (LOD) and limit of quantification (LOQ). We assessed the risk of bias across seven domains and graded certainty by outcome. We did not register a protocol prospectively. Results: Seventeen studies met the inclusion criteria. Materials spanned multilayer polyurethanes (SmartTrack, Clarity), PETG sheets (Essix ACE, Duran), and directly printed resins (Graphy TC-85DAC); a subset tested zinc-oxide (ZnO) nanoparticle coatings. Typical extractions immersed 0.1–1 g of material in cell-culture medium or artificial saliva at 37 °C for 24 h to 30 days. Cell viability usually remained ≥80%. Mild cytotoxicity (about 60–70% viability) appeared with harsher extractions, extended soaks, or an inadequate post-curing of printed parts. The estrogen-sensitive proliferation assay (E-Screen) returned negative results. In saliva-like media, bisphenol A (BPA) and related leachables were undetectable or in the low ng/mL range. In printed resins, urethane dimethacrylate (UDMA) sometimes appeared in water extracts, and amounts varied with curing quality. Evidence for chemical leaching and endocrine outcomes is sparse. We found no eligible in vitro study that quantified particle or microplastic release while also measuring a biological endpoint; we discuss particle findings from mechanical wear simulations only as the external context. Limitations: The evidence base is limited to in vitro studies. Many reports incompletely described extraction ratios and processing parameters. Risk of bias and certainty: Most studies used appropriate cell models and controls, but the reporting of surface-area-to-volume ratios, LOD/LOQ, and detailed post-processing parameters was often incomplete. Sample sizes were small, and dynamic wear or enzymatic conditions were uncommon. The overall risk of bias was moderate, and the certainty of evidence was low to moderate due to heterogeneity and in vitro indirectness. Conclusions: Under standard laboratory conditions, clear aligners and thermoplastic retainers show a favorable biocompatibility profile. For printed resins, outcomes depend mainly on processing quality, especially thorough washing and appropriate light-curing parameters. To improve comparability and support clinical translation, we recommend harmonized test protocols, transparent reporting, interlaboratory ring trials, and targeted clinical biomonitoring. Full article

Introduction: Suppressive antibiotic therapy (SAT) is a therapeutic alternative for complex infections where a cure is considered unlikely or impossible. SAT involves the prolonged, often indefinite, administration of antibiotics, typically given orally, to control symptoms. However, the increasing incidence of multidrug-resistant microorganisms limits the availability of oral options. Dalbavancin is a parenteral antibiotic with broad coverage against Gram-positive bacteria that offers the advantage of an extended dosing interval. The aim of this study was to describe the characteristics and clinical outcomes of patients with implant-associated osteoarticular infections receiving dalbavancin as SAT. A secondary objective was to identify factors associated with SAT failure with dalbavancin. Materials and Methods: We conducted a multicentre, observational study with retrospective recruitment of patients treated with dalbavancin as (SAT) for complex implant-associated osteoarticular infections, in which curative surgery was either not feasible or insufficient. Cohort characteristics were described, and variables associated with SAT failure under dalbavancin treatment were analysed. Results: A total of 43 patients received dalbavancin as SAT. The most frequent indication was prosthetic joint infection (38 [88.4%]). A total of 28 patients (65.1%) had chronic infections; the remaining cases were acute infections that had failed conservative management. Nine different dosing regimens of dalbavancin were used. Dalbavancin provided adequate symptomatic control in 32 patients (74.4%) over a follow-up period of 836.5 days (IQR 402–1288.5). The antibiotic was well tolerated; only one adverse effect was reported in a patient. Three patients developed resistance during treatment, which accounted for SAT failure. Conclusions: Dalbavancin is shown to be a safe and convenient alternative for SAT for orthopaedic implant infection. Although the development of resistance was infrequent, it can occur and should be monitored. Full article

The broader adoption of crumb rubber asphalt mixtures (CRAM) as sustainable pavement materials is currently limited by two key technical barriers. Firstly, there is a lack of standardized methods to evaluate mixing uniformity. Secondly, the material’s tendency for elastic recovery after compaction remains problematic. These barriers ultimately hinder the realization of CRAM’s full potential in vibration reduction, noise abatement, and resource recycling. To improve the performance evaluation system of CRAM and promote its development in engineering applications. Based on the distribution characteristics of crumb rubber in asphalt mixtures, this study established a crumb rubber distribution area moment model. It proposed a coefficient of area–distance variation to evaluate the mixing uniformity of CRAM. Through compaction tests and orthogonal tests, the effects of mixing process, mixing time, mixing temperature, compaction temperature, compaction times, and compaction method on the mixing uniformity and performance of CRAM are systematically investigated. The results show that, compared with specimens prepared by single compaction and compaction after high-temperature curing, CRAM specimens prepared by secondary compaction exhibit superior mechanical performance. The 24 h elastic recovery rate of these specimens is reduced to 24% of that in single-compacted specimens. The mixing process and mixing time have a significant impact on the mixing uniformity of CRAM. Pre-mixing crumb rubber with aggregates or extending the mixing time can improve the CRAM mixing uniformity by 45% and 18%, respectively. The mixing and compaction temperatures primarily affect the bulk density and Marshall stability of the specimens. When the mixing and compaction temperatures are 180 °C and 170 °C, respectively, the bulk density and Marshall stability of the molded specimens reach their maximum values. Through orthogonal analysis, the optimal mixing method for CRAM is determined as follows: mix aggregates and crumb rubber at 180 °C for 40 s, then add asphalt and continue mixing for another 80 s. The optimal process for secondary compaction is as follows: the first compaction at 170 °C, compacting each side 47 times, and the second compaction at 80 °C, compacting each side 23 times. Full article