Search Results (2,044)

Objective. The aim of this in vitro study was to compare the physical and mechanical properties of two resins used for provisional prostheses: a direct self-curing dimethacrylate resin and a 3D-printed resin, in order to assess their potential for different clinical applications. Methods. Flexural strength, microhardness, wear resistance, and water absorption were evaluated in accordance with ISO 4049 and ISO 10477. Samples were analyzed using scanning electron microscopy, X-ray spectroscopy, and mechanical testing, including flexural, wear, and scratch assays. Results. The 3D-printed resin demonstrated superior flexural strength (128 ± 2 MPa vs. 127 ± 16 MPa), microhardness (19.45 HV vs. 8.10 HV, p < 0.05), and wear resistance (mean wear area: 0.030 mm² vs. 0.047 mm²) compared to the self-curing dimethacrylate composite. However, it exhibited significantly higher water absorption (55.98 µg/mm³ vs. 15.0 µg/mm³), which may compromise its long-term durability in humid environments. Conclusions. Overall, the 3D-printed resin shows promising mechanical performance, but its high-water absorption remains a limitation for extended use. Further studies are required to evaluate its degradation and behavior under intraoral conditions. Clinical relevance. For the time being, self-curing resins remain the preferred choice for long-term provisional prostheses. Full article

Sediment erosion under turbulent wave action is a highly dynamic process shaped by the interaction between wave properties and sediment characteristics. Despite extensive empirical research, the underlying mechanisms of wave-induced erosion remain insufficiently understood, particularly regarding the threshold energy required for particle mobilization and the factors governing displacement patterns. This study employed a custom-built wave flume and a 3D-printed sampler to examine sediment behavior under controlled wave conditions. Rounded glass beads, chosen to eliminate the influence of particle shape, were used as sediment analogs with a similar specific gravity to natural sand. Ten experiments were conducted to systematically assess the effects of particle size, particle number, input voltage (wave power), and water depth on sediment response. The results revealed that (1) only a fraction of particles were mobilized, with the remainder forming stable interlocking structures; (2) the number of displaced particles increased with particle size, particle count, and water depth; (3) a threshold wave power is required to initiate erosion, though buoyancy under shallow conditions reduces this threshold; and (4) wave steepness, rather than voltage or wave height alone, provided the strongest predictor of sediment displacement. These findings highlight the central role of wave steepness in erosion modeling and call for its integration into predictive frameworks. The study concludes with methodological limitations and proposes future research directions, including expanded soil types, large-scale flume testing, and advanced flow field measurements. Full article

Electrogenerated chemiluminescence (ECL) is a powerful analytical technique that combines the best features of both electrochemical and photoluminescence methods. In this work, we present a direct ECL-based method for the detection of fentanyl using unmodified screen-printed electrodes. The analysed system consists of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) as the luminophore and fentanyl as the co-reactant. A comprehensive optimization of the experimental parameters, such as buffer pH, luminophore concentration and working electrode material, was performed in order to maximize the ECL response. The optimal conditions are identified as PBS buffer pH 6, 2.5 × 10⁻³ M Ru(bpy)₃²⁺ and bare gold screen-printed electrodes. Under these conditions, the system exhibited a strong and reproducible ECL signal, with a linear response to fentanyl concentration from 1 × 10⁻⁷ to 1 × 10⁻⁵ M and a limit of detection of 6.7 × 10⁻⁸ M. Notably, the proposed method does not require electrode surface modification, sample pretreatment or complex instrumentation, offering a rapid, sensitive, and cost-effective alternative for fentanyl detection. Furthermore, the storage of bare SPEs at room temperature in a dry place ensures their stability over months or even years, overcoming the limitations offered by ECL systems based on modifications of the working electrode with different nanomaterials. These findings highlight the potential of the proposed ECL approach as a robust and sensitive tool for the detection of synthetic opioids. Its simplicity, portability, and analytical performance make it particularly attractive for forensic and clinical applications where rapid and accurate opioid screening is essential. Full article

Monitoring the time-dependent rheological properties of 3D printed MgO-SiO₂-K₂HPO₄ is critical for optimizing the dynamic structural reconstruction ability. The collaborative analysis for the contribution of colloidal force based on EDLVO theory and the volume fraction of K-struvite (MgKPO₄·6H₂O) was conducted. Results showed that 20% silica fume (SF) was identified as the optimal content to achieve balanced rheo-mechanical performance (28 d compressive strength = 113.63 MPa, dynamic yield stress = 359.98 Pa, thixotropic area = 2.14 × 10⁴ Pa/s). The static yield stress development within 50 min exhibited two distinct stages: the initial rapid linear growth stage (Stage I, 5–30 min) dominated by colloidal forces (R² = 0.81 at 20% SF), followed by the slow increased plateau (Stage II, 30–50 min) correlated with K-struvite volume fraction. Also, dual crystallization pathways of K-struvite included direct precipitation from supersaturated Mg²⁺, K⁺, PO₄³⁻ ionic species and transformation from potassium-deficient phosphate phase. Quantitative results establish a predictive framework for microstructural construction, enabling precise control of structural build-up and 3D printability in MgO-SiO₂-K₂HPO₄ cementitious composites. Full article

The Na₂O-SrO-SiO₂ system shows promise in the development of glasses that can be transformed into electrically conductive glass ceramics. The conventional processing of such materials usually involves the synthesis of a parent glass, followed by a complex devitrification treatment. This study proposes a simplified approach based on the use of preceramic polymers, namely silicone resins combined with oxide fillers. These systems yield silicate-based ceramics through direct heat treatment, replicating the phase assembly of traditional glass ceramics with no need for prior glass melting. A printable formulation was developed by mixing a silicone resin with an acrylate-based photocurable resin, sodium nitrate and strontium carbonate. The resulting ‘suspension-emulsion’ was later shaped into monolithic components using digital light processing. After pyrolysis in nitrogen atmosphere, the components transformed into SrSiO₃ crystals embedded in a composite matrix, in turn composed of glass and turbostratic carbon (the latter specifically offered by the silicone polymer). This combination of crystalline silicates and carbon resulted in measurable electrical conductivity. This study confirms that silicone-derived systems can serve as effective precursors for conductive glass-ceramic analogues, providing an alternative to conventional methods with single-step processing. This approach enables structural shaping through 3D printing and the development of functional properties suitable for electronic or electrochemical applications. Full article

The design and production of goods have been completely transformed by additive manufacturing (AM), which makes it possible to create components with intricate and complex geometries that were previously impossible or impractical to produce. However, current technologies continue to produce coarse-surfaced metal components that typically exhibit fatigue properties, resulting in component failure and unfavorable friction coefficients on the printed part. Therefore, to improve the surface quality of the fabricated parts, post-processing of AM-created components is required. With emphasis on electroless nickel plating, ChemPolishing (CP), and ElectroPolishing (EP), this study investigates post-processing methods for stainless steel that is additively manufactured (AM). The rough surfaces created by additive manufacturing (AM) restrict direct use. While ElectroPolishing (EP) achieves high material removal rates but may not be consistent, ChemPolishing (CP) offers uniform smoothening. Nickel plating enhances additive manufacturing (AM) products’ resistance to wear and scratches and corrosion protection. To optimize nickel deposition, medium (6%–9%) and high (10%–13%) phosphorus nickel was tested using the L9 Taguchi design of experiments (DOE). Mechanical properties, including scratch resistance and adhesion, were evaluated using the TABER 5900 reciprocating (Taber Industries, North Tonawanda, NY, USA) abraser apparatus, a 5 N scratch test, and ASTM B-733 thermal shock method. Surface analysis was performed with the KEYENCE VHX-7000 microscope (Keyence Corporation, Itasca, IL, USA), and chemical composition before and after nickel deposition was assessed via the ThermoFisher Phenom XL scanning electron microscope (SEM, Thermo Fisher Scientific, Waltham, MA, USA) Optimal processing conditions, determined using Qualitek-4 software, Version 20.1.0 revealed improvements in both surface finish and mechanical robustness. This comprehensive analysis underscores the potential of nickel-coated additive manufacturing (AM) parts for enhanced performance, offering a pathway to more durable and efficient additive manufacturing (AM) applications. Full article

Companies are increasingly turning to additive manufacturing as the demand for one-off 3D-printed metal parts rises. The differences in available additive manufacturing technologies necessitate considering both cost and externalities to select the most suitable alternative. This study compares some of the most prevalent metal additive manufacturing technologies through a shop floor-level operational analysis. A steel robotic gripper is considered as a case study, based on which of the complex, interconnected operational factors that influence costs over time are analyzed. The developed cost model facilitates the estimation of costs, identification of cost drivers, and analysis of the impact of various operations management decisions on overall costs. We found that cost performance across Powder-Bed Fusion (PBF), Wire Arc Additive Manufacturing (WAAM), and CNC machining is determined by part design, quantity, and machine utilization. Although producing parts with complex internal features favors additive manufacturing, CNC outperforms in terms of economy of scale. While PBF offers excellent design freedom and parallel production, it incurs high fixed costs per build in under-utilized situations. A rough but fast method, such as Directed-Energy Deposition (DED)-based additive manufacturing, is believed to be more cost-efficient for large, simple shapes, but is not suitable when fine details are required. Laser-based DED approaches address this limitation of WAAM. Full article

Suture anchors are widely used for tendon and ligament repair, but their fixation strength is compromised in osteoporotic bone and limited bone volume such as the coracoid process. Existing designs are prone to penetration and insufficient cortical engagement under such conditions. In this study, we developed a novel short expandable-wing (SEW) suture anchor (Ti6Al4V) designed to enhance pull-out resistance through a deployable wing mechanism that locks directly against the cortical bone. Finite element analysis based on CT-derived bone material properties demonstrated reduced intra-bone displacement and improved load transfer with the SEW compared to conventional anchors. Mechanical testing using matched artificial bone surrogates (N = 3 per group) demonstrated significantly higher static pull-out strength in both normal (581 N) and osteoporotic bone (377 N) relative to controls (p < 0.05). Although the sample size was limited, results were consistent and statistically significant. After cyclic loading, SEW anchor fixation strength increased by 25–56%. In a 3D-printed anatomical coracoclavicular ligament reconstruction model, the SEW anchor provided nearly double the fixation strength of the hook plate, underscoring its superior stability under high-demand clinical conditions. This straightforward implantation protocol—requiring only a 5 mm drill hole without tapping, followed by direct insertion and knob-driven wing deployment—facilitates seamless integration into existing surgical workflows. Overall, the SEW anchor addresses key limitations of existing anchor designs in small bone volume and osteoporotic environments, demonstrating strong potential for clinical translation. Full article

This in vitro study aimed to quantitatively evaluate the accuracy of reproducing attachments for clear aligner therapy (CAT) using a standardized in-house fabrication protocol and to analyze discrepancies across maxillary tooth types. A custom attachment was designed on a symmetrical master model, and 30 experimental models were fabricated by three-dimensional (3D) printing, template construction, and bonding. Following scanning and superimposition, dimensional, angular, and positional deviations were quantified and statistically analyzed (p < 0.05). Results showed minor mean discrepancies but a consistent pattern of under-reproduction, most evident in the mesial and distal wall angles, as well as in the gingival bevel angle and attachment height. A significant trend was observed in the occlusal bevel, demonstrating marked extrusion in the anterior region that decreased posteriorly. Positional errors were minimal mesiodistally but substantial in the lingual and occlusal directions, with magnitudes varying by tooth type. In conclusion, this study identified consistent, predictable inaccuracies in a simulated in-house attachment reproduction protocol. These findings indicate that similar deviations may occur clinically, potentially affecting the predictability of CAT. Full article

This in vitro study evaluated the fracture resistance of metal–ceramic crowns repaired with milled hybrid resin, printed hybrid resin, lithium disilicate, and direct composite resin. One hundred crowns were fabricated, fractured under controlled loading, and 80 with standardized defects were randomly assigned to four groups (n = 20). Repairs were performed using CAD/CAM onlays or direct composite, followed by compressive testing until fracture. Mean fracture resistance values ranged from 1858.95 N to 1997 N across all groups, exceeding typical posterior occlusal forces (700–900 N). No statistically significant differences were found among groups (p = 0.200). Most failures were cohesive. These results indicate that both digital (milled and printed) and direct techniques offer sufficient strength to serve as minimally invasive and cost-effective alternatives to full crown replacement. Although limited by the in vitro design, this study supports the applicability of modern repair approaches in daily practice. Full article

People with disabilities often face challenges like moving around independently and depending on personal caregivers for daily life activities. Traditional assistive devices are universally accepted by these communities, but they are designed with one-size-fits-all approaches that cannot adjust to individual human sizes, are not easily customized, and are made from rigid materials that do not adapt as a person’s condition changes over time. This systematic review examines the integration of smart materials, sensors, actuators, and 3D/4D printing technologies in advancing assistive devices, with a particular emphasis on mobility aids. In this work, the authors conducted a comparative analysis of traditional devices with commercially available innovative prototypes and research stage assistive devices by focusing on smart adaptable materials and sustainable additive manufacturing techniques. The results demonstrate how artificial intelligence drives smart assistive devices in hospital decentralized additive manufacturing, and policy frameworks agree with the Sustainable Development Goals, representing the future direction for adaptive assistive technology. Also, by combining 3D/4D printing and AI, it is possible to produce adaptive, affordable, and patient centered rehabilitation with feedback and can also provide predictive and preventive healthcare strategies. The successful commercialization of adaptive assistive devices relies on cost effective manufacturing techniques clinically aligned development supported by cross disciplinary collaboration to ensure scalable, sustainable, and universally accessible smart solutions. Ultimately, it paves the way for smart, sustainable, and clinically viable assistive devices that outperform conventional solutions and promote equitable access for all users. Full article

Three-dimensional concrete printing (3DCP), an innovative fabrication technique, has emerged as an environmentally friendly digital manufacturing process for using recycled waste materials in the construction industry. The aim of this review paper is to critically evaluate the current state of research on the use of recycled materials such as aggregates and powders in 3DCP, correlating the environmental, economic, and performance parameter effects. This review comprehensively evaluates the potential benefits of incorporating recycled waste materials in 3D printing by critically reviewing the existing peer-reviewed articles through a scientometric review. The resulting bibliometric analysis identified 73 relevant papers published between 2018 and 2024. Through the critical review, five main research categories were identified: recycled materials in 3DCP arising mainly from construction demolition in powder and aggregate forms, which investigates the types of recycled materials used, their extraction methods, morphology and physical and chemical properties. The morphology properties of the materials used displayed high irregularities in terms of shape and percentage of adhered mortar. In the second category, printability and performance, the buildability, rheological properties and the mechanical performance of 3DCP with recycled materials were investigated. Category 3 assessed the latest developments in terms of 3D-printed techniques, including Neural Networks, in predicting performance. Category 4 analysed the environmental and economic impact of 3DCP. The results indicated anisotropic behaviour for the printed samples influencing mechanical performance, with the parallel printing direction showing improved performance. The environmental performance findings indicated higher global warming potential when comparing 3DCP to cast-in situ methods. This impact was reduced by 2.47% when recycled aggregates and binder replacements other than cement were used (fly ash, ground slag, etc.). The photochemical pollution impact of 3DPC was found to be less than that of cast-in situ, 0.16 to 0.18 C2H4-eq. This environmental impact category was further reduced up to 0.10 C2H4-eq following 100% replacement. Lastly, category 5 explored some of the challenges and barriers for the implementation of 3DCP with recycled materials. The findings highlighted the main issues, namely inconsistency in material properties, which can lead to a lack of regulation in the industry. Full article

Aluminum alloys under long-term service or repetitive stress are prone to small fatigue cracks (FCs) with arbitrary orientations, necessitating eddy current probes with focused magnetic fields and directional selectivity for reliable detection. This study presents a flexible printed circuit board (FPCB) probe with a double-layer planar excitation coil and a double-layer differential receiving coil. The excitation coil employs a reverse-wound design to enhance magnetic field directionality and focusing, while the differential receiving coil improves sensitivity and suppresses common-mode noise. The probe is optimized by adjusting the excitation coil overlap and the excitation–receiving coil angles to maximize eddy current concentration and detection signals. Finite element simulations and experiments confirm the system’s effectiveness in detecting surface cracks of varying sizes and orientations. To further characterize these defects, two time-domain features are extracted: the peak-to-peak value ($\Delta$P), reflecting amplitude variations associated with defect size and orientation, and the signal width ($\Delta$W), primarily correlated with defect angle. However, substantial overlap in their value ranges for defects with different parameters means that these features alone cannot identify which specific parameter has changed, making prior defect classification using a Transformer-based approach necessary for accurate quantitative analysis. The proposed method demonstrates reliable performance and clear interpretability for defect evaluation in aluminum components. Full article

Yield stress and thixotropy are critical rheological properties for enabling successful 3D printing of magnetic colloidal systems. However, conventional magnetic colloids, typically composed of a single dispersed phase, exhibit insufficient rheological tunability for reliable 3D printing. In this study, we developed a novel magnetic colloidal system comprising a carrier liquid, magnetic nanoparticles, and organic modified bentonite. A direct-ink-writing 3D-printing platform was specifically designed and optimized for thixotropic materials, incorporating three distinct extruder head configurations. Through an in-depth rheological investigation and printing trials, quantitative analysis revealed that the printability of magnetic colloids is significantly affected by multiple factors, including magnetic field strength, pre-shear conditions, and printing speed. Furthermore, we successfully fabricated 3D architectures through the precise coordination of deposition paths and magnetic field modulation. This work offers initial support for the material’s future applications in soft robotics, in vivo therapeutic systems, and targeted drug delivery platforms. Full article

This exploratory study investigates preliminary trends in the optimization of mechanical properties in 3D-printed components produced via Fused Deposition Modeling (FDM) using polycarbonate (PC) and polylactic acid (PLA). Through a systematic full factorial experimental design, three critical parameters were examined: material types (PC and PLA), layer thickness (0.2 mm and 0.4 mm), and build orientation (horizontal and vertical). Preliminary trends suggest that vertically oriented specimens showed up to 64.7% higher tensile strength compared to horizontal builds, though with significantly reduced ductility. Contributing to growing evidence regarding layer thickness effects, thicker layers (0.4 mm) showed improved ultimate strength by up to 36.2% while simultaneously reducing production time by 50%. However, statistical power analysis revealed insufficient sample size (n = 1 per condition) to establish significance for orientation effects, despite large practical differences observed. PC specimens demonstrated superior strength (maximum 67.5 MPa) and fracture energy, while PLA offered better ductility (up to 22.4% strain). These exploratory findings provide promising directions for future adequately powered investigations for tailored parameter selection according to specific application requirements. Full article