Search Results (1,239)

Recent breakthroughs in materials science have driven transformative advancements in restorative dentistry. Advanced dental materials, such as bioactive materials, nanocomposites, and fibre-reinforced composites, are attracting attention. Bioactive materials, such as calcium silicate-based cements and bioactive glass, represent a paradigm shift by interacting with biological tissues to stimulate regeneration. They promote hydroxyapatite formation, accelerating mineralisation in hard and soft tissues, and are pivotal tools in minimally invasive procedures due to their functions of structural support and biological interaction. Nanomaterials, especially nanocomposites with embedded nanoparticles, effectively address polymerisation shrinkage and wear in traditional composites. With just 1.5% shrinkage, a flexural strength over 150 MPa, and 44–60% higher wear resistance than conventional composites, they offer significant improvements. Nanocomposites also provide enamel-like translucency and a bond strength of 27–38 MPa to dentin, ensuring excellent aesthetics and durability—making them ideal for direct restorations. Fibre-reinforced composites with glass or polymer fibres balance aesthetics with strength and are increasingly used in restorations. Their high fracture resistance, which closely approaches that of a natural tooth, enables clinicians to preserve more healthy teeth during restoration, in line with the principles of modern conservative dentistry. Overall, bioactive materials enhance tissue repair, nanocomposites optimise form and function, and fibre-reinforced composites deliver strength without compromising aesthetics. As these materials transition from research to clinical practice, they promise longer-lasting treatments, fewer complications, and higher patient satisfaction. This narrative review aims to explore three types of advanced dental materials and their role in improving clinical outcomes. Full article

This paper presents a comprehensive characterization of bottom ash generated during biomass combustion in fluidized boilers, with a focus on its potential use in a circular economy. Two biomass bottom ash samples (BBA 1 and BBA 2) from commercial combined heat and power plants were tested. The scope of this study included the determination of chemical composition, phase composition, and leachability testing of selected impurities. The results showed that the bottom ashes tested are calcium silicate materials with varying proportions of calcium phases (anhydrite, portlandite, and calcite) and silica phases (quartz), depending on the type of biomass and combustion technology. Thermal analysis confirmed the presence of characteristic dehydration, decarbonation, and polymorphic transformations of quartz, with a low organic content. Leachability tests showed low mobility of most trace elements and heavy metals, with increased solubility of sulfates, chlorides, and alkali ions, typical for fluidized ash. The concentrations of As, Cd, Cr, Cu, Pb, Zn, and Hg in the eluates were low or below the limit of quantification, indicating the favorable chemical stability of the tested waste. The results obtained suggest that bottom ashes from biomass combustion in fluidized boilers may be a promising secondary raw material for engineering applications, especially in binding materials and bonded layers, and potentially also in selected agricultural applications, provided that the contents of sulfates, chlorides, and pH are controlled. Full article

Background: Root canal sealers may come into direct contact with periapical tissues, particularly in cases of apical extrusion, potentially influencing periapical healing and treatment outcomes. Cytotoxicity assessment represents a clinically relevant parameter when selecting endodontic sealers. However, evidence derived from in vitro studies remains heterogeneous and challenging to interpret from a clinical perspective. Therefore, the aim of this systematic review was to critically evaluate the in vitro cytotoxicity of all root canal sealers that have been commercially marketed over the years, excluding experimental materials, and to contextualize the findings in relation to clinically relevant experimental conditions. Methods: This systematic review was conducted according to PRISMA guidelines and preregistered on the Open Science Framework. PubMed, Scopus, and the Cochrane Library were searched up to 30 November 2025. In vitro studies evaluating the cytotoxicity of commercially available root canal sealers using validated cell viability or proliferation assays were included. Data extraction focused on sealer composition, setting condition, extraction protocols, exposure parameters, and cytotoxic outcomes. Due to marked methodological heterogeneity, a qualitative synthesis was performed. Results: Ninety-eight in vitro studies were included. All categories of root canal sealers demonstrated some degree of cytotoxicity, particularly when tested in freshly mixed conditions, at higher extract concentrations, or after prolonged exposure. Bioactive and calcium silicate-based sealers generally showed a more favorable cytotoxicity profile compared with conventional materials, especially after complete setting and at diluted concentrations, although cytotoxic effects were reported under specific experimental conditions. Resin-based sealers, including AH Plus, exhibited condition-dependent cytotoxicity, while zinc oxide–eugenol and glass ionomer sealers tended to display higher cytotoxic potential. Conclusions: In vitro cytotoxicity of root canal sealers varies according to material composition and experimental conditions. Bioactive sealers generally exhibit a more favorable biological profile, which may be clinically relevant in situations involving sealer extrusion or prolonged tissue contact. Standardized testing protocols and further translational studies are required to support evidence-based clinical material selection. Full article

Tungsten is a critical metal for advanced industrial applications, yet its supply is challenged by the depletion of high-grade ores. This study presents a comprehensive optimization and mechanistic analysis of the alkaline fusion process for extracting tungsten from wolframite ((Fe,Mn)WO₄) using sodium carbonate (Na₂CO₃). Experimental investigations systematically evaluated the effects of alkali-to-ore ratio, reaction temperature (650–1000 °C), and reaction duration (30–270 min). Optimal conditions were established at a 2:1 Na₂CO₃-to-ore molar ratio, a reaction temperature of 750 °C, and a holding time of 30 min, achieving a tungsten extraction efficiency exceeding 99.9%. This represents a significant improvement in energy and process efficiency over conventional methods. A novel kinetic analysis reveals a two-stage reaction mechanism, transitioning from a slow, diffusion-controlled solid-state reaction (E_a = 243 kJ/mol) to a rapid, autocatalytic liquid-phase reaction (E_a = 212 kJ/mol) upon the formation of a Na₂WO₄–Na₂CO₃ eutectic above approximately 590 °C. The optimal temperature of 750 °C is rationalized as the point that ensures operation within this kinetically favorable liquid-phase regime. Furthermore, a thermochemical analysis of ore impurities indicates that silicon, lead, sulfur, and calcium are effectively sequestered into the slag phase as stable silicates, insoluble lead compounds, and sulfates, highlighting an intrinsic purification benefit. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses confirmed minimal residual tungsten in the processed slag. This streamlined process, supported by a robust mechanistic understanding, reduces alkaline consumption, shortens reaction times, and maintains high yields, offering a sustainable and efficient pathway for leveraging declining wolframite resources. Full article

Background/Objectives: This study evaluates the penetration of a calcium silicate-based sealer (BC Universal) into dentinal tubules after different final irrigation protocols. Methods: Eighty-four single-rooted extracted teeth were instrumented with ProTaper Gold to size F4 and assigned to four groups (n = 21) according to the final irrigation protocol as follows: conventional needle irrigation (CNI), sonic agitation with EndoActivator (EA), ultrasonic activation (UA), and XP-Endo Finisher (XPF). A total of 20 canals from each group were filled with BC Universal sealer mixed with fluorescein and the single-cone obturation technique. The remaining specimen in each group served as a negative control to assess potential imaging bias. Specimens were sectioned 3 mm from the apex and analyzed under confocal laser scanning microscopy. Sealer penetration was assessed by penetration area (PA), maximum depth (MaxD), mean depth (MeanD), and percentage of canal perimeter infiltrated (P). Data were analyzed using Kruskal–Wallis or ANOVA tests (α = 0.05). Results: All activation/agitation techniques showed significantly higher penetration than CNI across all variables (p < 0.001). No significant differences were found among EA, PUI, and XPF for PA, MaxD, and MeanD. However, XPF exhibited the highest perimeter infiltration, which was significantly greater than EA and UA (p < 0.001). Conclusions: Irrigant activation significantly enhanced dentinal tubule penetration of BC Universal sealer compared to CNI. XPF provided superior P, suggesting superior circumferential distribution. These findings suggest a more effective cleaning of the root canal in the apical third achieved by the tested irrigant activation/agitation techniques, which may improve the sealing potential of BC Universal sealer. Full article

Enhanced silicate rock weathering (ESRW) has been proposed as a promising carbon dioxide removal strategy, yet its carbon sequestration pathways, durability, and ecosystem dependence remain incompletely understood. Here, we synthesize evidence from field experiments, observational studies, and modeling to compare ESRW-induced carbon dynamics across forest and cropland ecosystems using a unified SOC–SIC dual-pool framework. Across both systems, ESRW operates through shared geochemical processes, including proton consumption during silicate dissolution and base cation release, which promote atmospheric CO₂ uptake. However, carbon fate diverges markedly among ecosystems. Forest systems, characterized by high biomass production, deep rooting, and strong hydrological connectivity, primarily favor biologically mediated pathways, enhancing net primary productivity and mineral-associated organic carbon (MAOC) formation, while facilitating downstream export of dissolved inorganic carbon (DIC). In contrast, intensively managed croplands more readily accumulate measurable soil inorganic carbon (SIC) and soil DIC over short to medium timescales, particularly under evapotranspiration-dominated or calcium-rich conditions, although SOC responses are often moderate and variable. Importantly, only a subset of ESRW-driven pathways—such as MAOC formation and secondary carbonate precipitation—represent durable carbon storage on decadal to centennial timescales. By explicitly distinguishing carbon storage from carbon transport, this synthesis clarifies the conditions under which ESRW can contribute to climate change mitigation and highlights the need for ecosystem-specific deployment and monitoring strategies. Full article

The valorization of dredged sediments represents a major environmental and logistical challenge, particularly in the context of forthcoming regulations restricting their marine disposal. This study investigates the potential of untreated dredged sediments as sustainable raw materials for geopolymer binder development, with the dual objective of sustainable sediment management and reduction in cement-related environmental impact. Dredged sediments from the Grand Port Maritime de Bordeaux (GPMB) were activated with sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), both alone and in combination, with supplementary aluminosilicate and calcium-rich co-products, to assess their reactivity and effect on binder performance. A multi-scale experimental approach combining mechanical testing, calorimetry, porosity analysis, Scanning Electron Microscopy and Energy-Dispersive Spectroscopy (SEM–EDS), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and solid-state Nuclear Magnetic Resonance (NMR) was employed to challenge the commonly assumed inert behavior of sediments within geopolymer matrices, to elucidate gel formation mechanisms, and to optimize binder formulation. The results show that untreated sediments actively participate in alkali activation, reaching compressive strengths of up to 5.16 MPa at 90 days without thermal pre-treatment. Calcium-poor systems exhibited progressive long-term strength development associated with the formation of homogeneous aluminosilicate gels and refined microporosity, whereas calcium-rich systems showed higher early age strength but more limited long-term performance, linked to heterogeneous gel coexistence and increased total porosity. These findings provide direct evidence of the intrinsic reactivity of untreated dredged sediments and highlight the critical role of gel chemistry and calcium content in controlling long-term performance. The proposed approach offers a viable pathway for low-impact, on-site sediment valorization in civil engineering applications. Full article

Hydraulic calcium silicate cements (HCSCs) are contemporary materials in vital pulp therapy (VPT) and regenerative endodontic therapy (RET) due to their favorable effects on pulpal and periodontal cells, including cell differentiation and hard tissue formation. Recent studies also indicated the involvement of several S100A proteins in inflammatory, differentiation, and mineralization processes of the pulp. The aim of the present study was to investigate the effects of HCSCs on S100A gene expression in human dental pulp stem cells (hDPSCs). Human DPSCs were isolated and characterized by multi-lineage stem-cell markers and differentiation protocols. In stimulation experiments hDPSCs were exposed to ProRoot^®MTA, Biodentine^®, IL-1β, and dexamethasone. Cell viability was determined by XTT assay. IL-6 and IL-8 mRNA expression was measured to analyze proinflammatory response. In addition, odontogenic differentiation and biomineralization assays were conducted (DSPP- and ALP-mRNA expression, ALP activity, and Alizarin Red staining). Differential expression of 13 S100A genes was examined using qPCR. Low concentrations of HCSCs enhanced the proliferation of hDPSCs, whereas higher concentrations exhibited cytotoxic effects. HCSCs induced a pro-inflammatory response and led to odontogenic differentiation and biomineralization. This was accompanied by significant alterations in the expression levels of various S100A genes. ProRoot^®MTA and Biodentine^® significantly affect the expression of several S100A genes in hDPSCs, supporting their role in inflammation, differentiation, and mineralization. These findings indicate a link between the effects of HCSCs on human pulp cells during VPT or RET and S100A proteins. Full article

To evaluate the stability of fiber-reinforced cemented foamed backfill (FCFB) in complex underground mining environments, this study investigates the synergistic effects of fiber content and modified coal gangue (MCG) under acidic and high-temperature conditions. Through a systematic analysis of hydration processes, compressive strength, and deformation characteristics, the research identifies critical mechanisms for optimizing backfill performance. Calcination of MCG at 700 °C enhances gelling activity via amorphous phase formation, while modified aluminum dross (MAD) treated at 950 °C develops dense α-Al₂O₃ and spinel phases, significantly improving chemical stability. In acidic environments, the suppression of calcium silicate hydrate (C-S-H) is offset by the development of Al³⁺-driven C-A-S-H gels. These gels adopt a tobermorite-like structure, substantially increasing acid resistance. Mechanical testing reveals that while 1% fiber reinforcement promotes nucleation and densification, a 2% concentration hinders hydration. Compressive strength at 28 days shows constrained growth due to pore inhibition, and failure modes transition from multi-crack parallel failure (3-day) to single-crack tensile-shear failure. Under acidic conditions, strain concentration in the upper sample highlights a competitive mechanism between Al³⁺ migration and fiber anchorage. Ultimately, the coordinated regulation of MCG/MAD and fiber content provides a robust solution for roof support in challenging thermo-chemical mining environments. Full article

This study investigated the effects of incorporating rice husk ash (RHA) as a partial replacement for cement on the properties of concrete. To determine the optimal replacement level, RHA was used to replace cement in varying proportions, ranging from 0% to 25% in 5% increments. The mix with 0% RHA served as the control. The properties evaluated included setting time, density, and compressive strength. The results revealed that blending RHA with cement increased the initial setting time. This was attributed to the lower calcium oxide (CaO₂) content of RHA, which slows early-age hydration reactions. Conversely, the final setting time was reduced due to the pozzolanic activity of RHA, which enhances later-stage reactions. Additionally, the inclusion of RHA resulted in a decrease in concrete density, owing to its lower specific gravity and bulk density compared to Portland cement. Despite this, RHA-modified specimens exhibited higher compressive strengths than the control specimens. This strength enhancement was linked to the formation of additional calcium–silicate–hydrate (C-S-H) gel due to the pozzolanic reaction between amorphous silica in RHA and calcium hydroxide (CaOH) from hydration reaction. The gel fills concrete voids at the microstructural level, producing a denser and more compact concrete matrix. Based on the balance between strength and durability, the optimal RHA replacement level was identified as 10%. Full article

To improve traditional cement manufacturing, which generates a large amount of greenhouse gases, blending calcareous green algae and fly ash as cement replacement materials is expected to achieve nearly zero carbon emissions. As a calcareous green alga, Halimeda macroloba is a significant producer of biogenic calcium carbonate (CaCO₃), sequestering approximately 440 kg of carbon dioxide (CO₂) per 1000 kg of CaCO₃, with CaCO₃ production reported in relation to algal biomass. To assess the new low-carbon/low-waste cement production process, the proposed scenarios (2 and 3) are validated via Python-based modeling (Python 3.12) and Aspen Plus^® simulation (Aspen V14). The core technology is the pre-calcination of algae-derived CaCO₃ and fly ash from coal combustion, which are added to a rotary kiln to enhance the proportions of tricalcium silicate (C₃S) and dicalcium silicate (C₂S) for forming the desired silicate phases in clinker. Through the lifecycle assessment (LCA) of all scenarios using SimaPro^® (SimaPro 10.2.0.3), the proposed Scenario 2 achieves the GWP at approximately 0.906 kg CO₂-eq/kg clinker, lower than the conventional cement production process (Scenario 1) by 47%. If coal combustion is replaced by natural gas combustion, the fly ash additive is reduced by 74.5% in the cement replacement materials, but the proposed Scenario 3 achieves the GWP at approximately 0.753 kg CO₂-eq/kg clinker, lower than Scenario 2 by 16.9%. Moreover, the LCA indicators show that Scenario 3 has lower environmental impacts on human health, ecosystem, and resources than Scenario 1 by 24.5%, 60.0% and 68.6%, respectively. Full article

To investigate the biosilicification capabilities of Bacillus mucilaginosus and Bacillus polymyxa, silicon concentrations in supernatants from quartz and calcium silicate cultures were monitored over a 12-day period using inductively coupled plasma optical emission spectrometry (ICP-OES). Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to evaluate changes in the absorption intensity of Si–O–Si characteristic peaks, crystalline phase transformations in the reaction products, and the microstructural morphology of quartz and calcium silicate before and after microbial leaching. The results show that after leaching with B. mucilaginosus, the dissolved silicon concentration in the quartz supernatant reached a maximum of 73.868 mg/L on day 8. In contrast, following treatment with B. polymyxa, the silicon concentration in the calcium silicate supernatant peaked earlier, at 149.153 mg/L on day 4. After microbial leaching, both substrates exhibited marked changes in the intensity of the infrared absorption peaks at 1071 cm⁻¹ and 1083 cm⁻¹, suggesting the formation of Si–O–R type organosilicon complexes. Iron tailings (containing inert silica) and fly ash (containing active silica) were selected for experimental validation. Following treatment with B. mucilaginosus for desilication over an 8-day period, the activity index of iron tailings increased from 77.83% to 90.51%, while that of fly ash rose from 66.32% to 85.01%. ICP-OES analysis confirmed that under the action of B. mucilaginosus, the trends in silicon concentration and activity index in the supernatant of silica-containing solid wastes, such as iron tailings and fly ash, were consistent with those observed in quartz, thereby demonstrating effective biological desilication. These findings provide novel insights into the development of environmentally sound disposal methods for a wider range of solid waste types. Full article

Metakaolin (MK) obtained from calcined kaolinitic clay is a highly reactive pozzolanic ingredient for use as an emerging supplementary cementitious material (SCM) in modern sustainable binder productions. It provides elevated alumina to promote formations of Alumina Ferrite Monosulfate (AFm) and Calcium-Aluminium-Silicate-Hydrate (C-A-S-H) phases, enhancing the chloride binding capacity. However, due to inherent material uncertainty and lack of approach in quantifying hydration kinetics and chloride binding capacity across varied mixes, robustly assessing the chloride resistance of metakaolin-blended concrete remains challenging. In light of this, a machine learning-aided framework that encompasses physics-based material characterisation and ageing modelling is developed to bridge the knowledge gap. Through applying to laboratory experiments, the impacts of uncertainty on the phase assemblage of hydrated system and chloride penetration are quantified. Moreover, the novel Extended Support Vector Regression (XSVR) method is incorporated and verified against a crude Monte Carlo Simulation (MCS) to demonstrate the capability of achieving effective and efficient uncertainty-aware chloride resistance analyses. With the surrogate model established using XSVR, quality control of metakaolin towards durable design optimisation against chloride-laden environments is discussed. It is found that the fineness and purity of adopted metakaolin play important roles. Full article

Background: Autologous platelet concentrates, including platelet-rich fibrin (PRF) matrices, have been proposed as biologically active scaffolds for vital pulp therapy. Evidence on the clinical use of different solid PRF matrices for direct pulp capping remains limited. Objective: The aim of this study is to describe and monitor two clinical cases of reversible pulpitis treated with direct pulp capping using two PRF membranes prepared by different centrifugation approaches, namely advanced platelet-rich fibrin plus (A-PRF+) and horizontal platelet-rich fibrin plus (H-PRF). Methods: In Case 1, A-PRF+ was prepared using a fixed-angle centrifugation protocol; in Case 2, H-PRF was prepared using a horizontal centrifugation protocol. In both cases, deep carious lesions with small carious pulp exposures (<1.5 mm) were managed by caries removal, ozone-assisted dentin disinfection, and direct pulp capping with the respective PRF membrane, followed by temporary calcium-silicate cement definitive coronal restoration. Clinical and radiographic follow-up, including cone-beam computed tomography, was performed for up to 12 months. Results: In Case 1 (A-PRF+), reparative dentin bridge formation was confirmed at 90 days, with a thickness of 0.2 mm. In Case 2 (H-PRF), reparative dentin was observed within 46 days, with a thickness of 0.28 mm. In both cases, pulp vitality was maintained, and no clinical symptoms or periapical changes were detected during the 12-month follow-up. Conclusions: These two cases suggest that direct pulp capping using PRF membranes (A-PRF+ or H-PRF), combined with ozone-assisted dentin disinfection and adequate coronal sealing, may be associated with maintained pulp vitality and hard-tissue repair after carious pulp exposure diagnosed as reversible pulpitis. Due to the descriptive two-case design and major confounding factors (including age and lesion characteristics), no comparative conclusions can be drawn. Prospective controlled clinical studies with standardized protocols are warranted. Full article

Rubber particles have been proven to have the advantages of improving the energy absorption effect and enhancing the friction between soil particles when used to modify the soil. The rubber-modified soil technology also provides a new solution for the pollution-free disposal of waste rubber. However, when rubber particles are used to modify collapsible loess, they cannot significantly enhance its strength. Previous studies have not systematically clarified whether combining rubber particles with different cementation mechanisms can overcome this limitation, nor compared their shear mechanical effectiveness under identical conditions. In view of this, a dual synergistic strategy is implemented by combining rubber with lime and rubber with enzyme-induced calcium carbonate precipitation (EICP). Direct shear tests and scanning electron microscopy are used to evaluate four modification approaches: rubber alone, lime alone, rubber with EICP, and rubber with lime. Accordingly, shear strength, cohesion, and internal friction angle are quantified. At a vertical normal stress of 100 kPa and above, samples modified with rubber and lime (7–9% lime and 6–8% rubber) achieve peak shear strength values of 200–203 kPa, representing an 86.4% increase compared to rubber alone. Microscopic analysis reveals that calcium silicate hydrate gel effectively anchored rubber particles, forming a composite structure with a rigid skeleton and elastic buffer. In comparison, the rubber and EICP group (10% rubber) shows a substantial increase in internal friction angle (24.25°) but only a modest improvement in cohesion (16.5%), which is due to limited continuity in the calcium carbonate bonding network. It should be noted that the performance of EICP-based modification is constrained by curing efficiency and reaction continuity, which may affect its scalability in conventional engineering applications. Overall, the combination of rubber and lime provided an optimal balance of strength, ductility, and construction efficiency. Meanwhile, the rubber and EICP method demonstrates notable advantages in environmental compatibility and long-term durability, making it suitable for ecologically sensitive applications. The results offer a framework for loess stabilization based on performance adaptation and resource recycling, supporting sustainable use of waste rubber in geotechnical engineering. Full article