Search Results (56)

The present study demonstrates that the corrosion behavior of dental cobalt–chromium (Co–Cr) alloys is strongly influenced by the interaction between microstructure, manufacturing technique, and oral chemical environment. A comparative investigation was conducted on Co–Cr specimens fabricated using four technological routes: conventional casting, CAD/CAM machining, Selective Laser Melting (SLM), and Direct Metal Laser Sintering (DMLS). The study included microstructural characterization, evaluation of generalized corrosion behavior using the rotating electrode technique, assessment of localized crevice corrosion, and quantitative analysis of the release of twenty metallic cations. Extraction tests were performed for 168 h in two media simulating aggressive oral environments: 0.07 N HCl (acidic medium) and a fluoride-containing electrolyte (0.1% NaF + 0.1% KF). Electrochemical measurements were recorded in the current density range of 10⁻¹⁰ to 10⁻⁷ A/cm², while released cation concentrations were quantified at the µg/L level. All alloys exhibited very low corrosion current densities (icorr in the 10⁻⁸ to 10⁻⁹ A·cm⁻² range), confirming overall good corrosion resistance. Among all manufacturing routes, CAD/CAM specimens demonstrated the highest electrochemical performance, with a wide passivity domain extending up to approximately 740 mV/SCE. A statistical interaction analysis between extraction media and manufacturing techniques was performed using the non-parametric Mann–Whitney (MW) U test. Among the analyzed elements, only chromium showed a statistically significant difference between media (p < 0.05), with an approximately 25-fold-higher release in acidic conditions compared with the fluoride medium, confirming the predominant role of proton-induced destabilization of the protective Cr₂O₃ passive film. In contrast, fluoride-containing media induced selective release of elements such as Cu (3× higher), W (2.5× higher), and Mo (1.4× higher), associated with complexation phenomena. The manufacturing route significantly influences corrosion behavior. Although additive manufacturing technologies (SLM/DMLS) enable highly accurate and customized prosthetic designs, rapid solidification and microstructural heterogeneities may increase susceptibility to localized corrosion compared with more homogeneous CAD/CAM materials. Clinically, these findings suggest that future restorative strategies should incorporate corrosion-aware material selection within digital workflows. As digital dentistry evolves, predictive models integrating patient-specific oral conditions may assist clinicians in selecting the most appropriate material system for long-term performance. In conclusion, the long-term success of dental Co–Cr prosthetic devices depends not only on mechanical strength and precision of fit, but also on sustained electrochemical stability in the complex oral environment. Full article

We report a versatile, CMOS-compatible fabrication module for sub-100 nm TiN and TaN pillar electrodes, a key building block for sandwich-type test structures. As a demonstration, the electrodes were integrated into carbon nanotube-based nonvolatile random-access memory (CRAM) test structures. High-resolution hydrogen silsesquioxane (HSQ) masks defined by electron beam lithography were transferred into TiN films using optimized Ar/Cl₂ inductively coupled plasma reactive ion etching. Optical emission spectroscopy was used for real-time endpoint detection, ensuring precise etch control. The process achieved a TiN-to-HSQ selectivity of ~1.6 and reproducible nanoscale features with smooth sidewalls and an average taper angle of ~77°. Buffered hydrogen fluoride treatment effectively removed residual HSQ, revealing sharp TiN features and preserving pillar geometry. Atomic force microscopy (AFM) confirmed pillar height and profile fidelity, while conductive AFM verified electrical conductivity after planarization. The module was further demonstrated through the fabrication of TiN pillar arrays, TaN pillars, and sub-100 nm TiN line arrays. A CRAM test structure incorporating TiN pillars exhibited preliminary switching, indicating that both the test structure and fabrication process are feasible. This fabrication module provides a reproducible platform for nanoscale TiN and TaN electrodes, supporting laboratory-scale research and providing a pathway toward future integration of emerging memory and nanoelectronic technologies. Full article

Thick (900–1500 µm), crack-free lithium manganese oxide (LMO) electrodes with a polyvinylidene fluoride (PVDF)-based polymer electrolyte were prepared using an innovated slurry casting method. The selectivity and intercalation capacity of the thick electrodes of 900–1500 μm were evaluated in aqueous chloride solutions containing main cations in synthetic Salar de Atacama brine using cyclic voltammetry (CV) measurements. The CV data indicated that a high Li⁺ selectivity of Li/Na = 152.7 could be achieved under potentiostatic conditions. With the thickest electrode, while the mass specific intercalation capacity was 6.234 mg per gram of LMO, the area specific capacity was increased by 3–11 folds compared to that for conventional thin electrodes to 0.282 mg per square centimeter. In addition, 82% of capacity was retained over 30 intercalation/dis-intercalation cycles. XRD and electrochemical analyses revealed that both Faradaic diffusion-controlled or battery-like intercalation and Faradaic non-diffusion controlled or pseudocapacitive intercalation contributed to the capacity and selectivity. This work demonstrates a practical technology for thick electrode fabrication that promises to result in a significant reduction in manufacturing and operational costs for lithium extraction from brines. Full article

Continuous use of clear aligners modifies the oral environment and may favor bacterial colonization. Integration of topical fluoride-based agents could strengthen enamel and reduce biofilm formation. This study evaluated the effects of a galenic fluoride-mint spray (225–250 ppm fluoride and 1–2% peppermint essential oil) on salivary fluoride concentration and bacterial biofilm during orthodontic treatment. Ten patients using 3D-printed nighttime aligners were enrolled. Saliva samples were analyzed with an ion-selective electrode (ISE) at baseline, immediately after inserting the sprayed aligners and after 15, 30, 45 min post application. Biofilm morphology was qualitatively assessed by scanning electron microscope (SEM) in three aligners: unused, worn 14 nights without spray, worn 14 nights with spray. Salivary fluoride increased from 0.7–0.8 mg/L at baseline to 5.96 mg/L when the spray was applied on a new aligner and 8.42 mg/L on a used aligner, then progressively decreased, returning close to baseline at 45 min with the new aligner and remaining higher with the used aligner. SEM images showed mature and heterogeneous biofilm on used aligners without the spray, while aligners with nightly spray application exhibited qualitatively reduced and less organized surface deposits. The fluoride- and mint-based spray rapidly increases salivary fluoride and reduces biofilm formation on nighttime clear aligners, improving preventive oral health during orthodontic treatment. Full article

Graphite anodes are widely used as consumable electrodes in the high-temperature electrolytic production of rare earth metals within fluoride molten salts. However, their rapid and complex corrosion presents significant economic and operational challenges, including high consumption costs, process instability, greenhouse gas emissions, and product contamination. While the corrosion morphology of specific graphite types has been studied, a systematic investigation linking the intrinsic properties of diverse graphite materials to their microstructural and chemical evolution during corrosion is lacking. This study elucidates the corrosion mechanisms of three distinct graphite anodes—fine-grained, isostatically pressed graphite anodes (#1), medium-coarse-grained, extruded graphite anodes (#2), and recycled, extruded graphite anodes (#3) in industrial PrNdF₃–LiF molten salt electrolytes at 1050 °C. Through a multifaceted analytical approach encompassing SEM, EDS, XRD, Raman, and FT-IR, we investigated the macro- and microscale corrosion behaviors across multiple scales. The results revealed markedly different degradation patterns: the #1 anode exhibited intergranular corrosion with granular exfoliation; the #2 anode developed a protective but cracked resolidified salt layer; and the #3 anode suffered the most severe uniform and pitting corrosion. Postcorrosion analysis confirmed surface enrichment with fluorine, praseodymium, and neodymium, the formation of PrF₃ and NdF₃ phases, and substantial degradation of the graphitic structure. Raman spectroscopy specifically revealed a reduction in the crystallite size, introduction of in-plane point defects, and disruption of the interlayer stacking order. On the base of infrared spectroscopy analysis, all key characteristic absorption peaks of the graphite anodes undergo consistent attenuation after corrosion. This work provides critical insights for the informed selection and optimization of graphite anodes to increase the efficiency and sustainability of rare earth electrolysis. Full article

Lithium-ion batteries (LIBs) are vital for modern energy storage applications. Lithium iron phosphate (LFP) is a promising cathode material due to its safety, low cost, and environmental friendliness compared to the widely used nickel manganese cobalt oxide (NMC), which contains hazardous nickel and cobalt compounds. However, challenges remain in enhancing the performance of LFP cathodes due to their low electronic and ionic conductivity. To improve both the safety and sustainability of the battery, this work presents a water-based LFP cathode utilizing the bio-based binder carboxymethyl cellulose (CMC), eliminating the need for polyvinylidene fluoride (PVDF) and the toxic solvent N-methyl-2-pyrrolidone (NMP). This study investigates the impact of different dispersing methods—dissolver mixing and wet jet milling—on slurry properties, electrode morphology, and battery performance. Slurries were characterized by rheology, particle size distribution, and sedimentation behavior, while coated and calendered electrodes were examined via thickness measurements and scanning electron microscopy (SEM). Electrochemical performance of the electrodes was evaluated by means of C-Rate testing. The results reveal that dispersing methods significantly influence slurry characteristics but marginally affect electrochemical performance. Compared to dissolver mixing, wet jet milling reduced the median particle size by 39% (ΔD50 = 3.1 µm) and lowered viscosity by 96% at 1 s⁻¹, 80% at 105 s⁻¹, and 64% at 1000 s⁻¹. In contrast, the electrochemical performance of the resulting electrodes differed only slightly, with discharge capacity varying by approximately 12.8% at 1.0 C (Δcapacity = 10.7 mAh g⁻¹). This research highlights the importance of optimizing not only material selection but also processing techniques to advance safer and more sustainable energy storage solutions. Full article

Breastfeeding based on the use of follow-on milk may contain traces of xenobiotic elements that could pose a risk to the health of the vulnerable population for which it is intended. Fluorine is a non-essential element that, at high concentrations, can produce adverse health effects such as dental fluorosis, decreased IQ (intelligence quotient), thyroid alterations, and kidney damage. Given the vulnerability of infants and the possible presence of fluoride in this type of product, the content of this anion was determined in a total of 46 samples of follow-on milk from different brands and types (starter, follow-on, and hydrolysate formulas) using a fluoride ion-selective electrode (EWI). The highest mean concentration of fluoride was recorded in the hydrolysate formulas (3.38 ± 2.78 mg/L). The dietary intake assessment indicated that some brands of hydrolyzed formulas could pose a health risk, providing up to 94.1% of the UL (upper level) with only one 90 mL serving in the 0–6-month age group. It is recommended that consumers be aware of the fluoride content in the water used to prepare bottles, as it can further increase total fluoride intake and therefore pose a risk to the health of infants. Full article

Background/Objectives: Fluorides play a well-established role in preventing dental caries, primarily by enhancing enamel resistance and inhibiting demineralization. Drinking water is among the most important sources of systemic fluoride intake. In 1993 and 2007, national analyses of Austrian drinking water revealed fluoride levels below 0.5 mg/L in almost all regions, which is insufficient for effective caries prevention. The present study aimed to re-examine the fluoride concentration in Austrian drinking water. Methods: Drinking water was collected in a total of 1985 Austrian municipalities. Fluoride concentration was measured by a fluoride-selective electrode. Results: The average fluoride concentration in the measured water samples ranged between 0.1 and 0.27 mg/L, depending on the region. The analysis revealed that 98% of the municipal drinking water samples contained fluoride at concentrations below 0.5 mg/L. In almost one quarter of Austrian municipalities, the fluoride levels amounted to less than 0.1 mg/L. The fluoride concentration in the drinking water of one Tyrolean municipality exceeded the recommended threshold. Conclusions: The results of the study reveal that the fluoride concentration in Austrian drinking water is generally too low to provide effective prevention against dental caries, affecting nearly all municipalities. Notably, the drinking water of one municipality reached potentially harmful fluoride levels. These findings could be used as a basis for targeted and individual fluoride supplementation, as well as for national or area-specific guidelines. Full article

The objective of this study was to assess the content of selected elements—fluorine, calcium and inorganic phosphorus—in infusions prepared from selected commercial leaf teas available on the Polish market. A comprehensive analysis was conducted based on tea type and geographical origin. In addition, the Target Hazard Quotient (THQ) was calculated to estimate the non-carcinogenic health risk associated with fluoride intake from tea consumption. Methods: A total of 98 leaf tea samples were analyzed, including 55 black, 27 green, 9 oolong, and 7 white teas. Standardized brewing protocols were applied. Measured parameters included pH, calcium and inorganic phosphorus content, buffer capacity, and titratable acidity. Fluoride concentrations were determined using an ion-selective electrode. Statistical analysis was performed using non-parametric methods (Kruskal–Wallis ANOVA with DSCF post hoc test), and heatmaps were generated to illustrate the distribution of THQ across different models. Results: Black teas exhibited significantly lower pH values and higher titratable acidity, buffer capacity, and inorganic phosphorus levels compared to other tea types, indicating distinct physicochemical properties. Although all THQ values for fluoride remained well below the safety threshold (THQ < 1), the highest values were observed in elderly individuals with low body weight, particularly women consuming green tea, suggesting increased vulnerability in this subgroup. Conclusions: Among the analyzed samples, black teas demonstrated the most distinct chemical profile, characterized by the lowest pH and the highest acidity, buffer capacity, and fluoride and phosphorus content—especially in teas originating from Africa and Central Asia. While fluoride exposure from leaf tea infusions does not appear to pose a direct health risk, older adults, particularly low-weight women, may be more susceptible to potential non-carcinogenic effects and should moderate their intake of high-fluoride teas. Full article

This study aimed to evaluate the fluoride content and other key physicochemical properties in commercially available black tea infusions, with a focus on tea form and geographic origin, in order to assess their contribution to total dietary fluoride intake. Methods: A total of 121 black tea samples were analyzed, including 66 loose-leaf, 42 bags, and 13 pyramid-bag teas. Infusions were prepared using standardized brewing protocols. Fluoride concentrations were determined with an ion-selective electrode, while the pH, buffer capacity, titratable acidity, calcium, and inorganic phosphorus were also measured. Statistical analysis included ANOVA, Tukey post hoc tests, and Pearson correlation analysis. Results: Fluoride content varied significantly by tea form and origin. Infusion of tea bags exhibited the highest fluoride, calcium, and acidity levels, while loose-leaf teas had the lowest. Teas from Africa contained approximately twice as much fluoride as those from Central or East Asia. Significant correlations between fluoride, calcium, and phosphorus were observed, particularly in tea-bag infusions, suggesting processing influences mineral release. Conclusions: Black tea, particularly in bag form and sourced from African regions, may significantly contribute to daily fluoride intake. Given the potential to exceed recommended fluoride thresholds, especially in individuals consuming multiple cups daily or living in fluoridated areas, these findings underscore the importance of consumer awareness and possible product labeling to guide safe consumption. Full article

This study evaluated the pH, fluoride (F), and calcium (Ca) concentrations in saliva-derived microcosm biofilms following treatments with dentifrices applied at different amounts and F concentration. Human saliva was inoculated into McBain culture medium, and treatments were applied at 72/78/96 h (1 min). Fluoridated dentifrices containing 550 or 1100 ppm F (550F and 1100F, respectively) were used at the following combinations (intensities): (i-1) 550F/0.08 g or 1100F/0.04 g; (i-2) 550F/0.16 g or 1100F/0.08 g; (i-3) 550F/0.32 g or 1100F/0.16 g. A negative control (fluoride-free dentifrice—PLA) was also included. Biofilm F and Ca were measured with an ion-selective electrode and colorimetrically, respectively, while pH in the culture medium was measured with a pH electrode. Data were subjected to ANOVA and Student–Newman–Keuls’ test (p < 0.05). F-dentifrices did not significantly alter pH compared to PLA, except for 1100F at i-3. Biofilm F levels at i-1 and i-2 were comparable, for both 550F and 1100F, while 1100F at i-3 led to the highest biofilm F concentration. All F-groups showed significantly higher Ca levels than PLA, especially at i-2 and i-3. In conclusion, the interplay between dentifrice amount and F concentration was more influential on the biofilm’s inorganic composition and pH than either variable alone. Full article

This study aimed to evaluate the influence of different fluoride-containing toothpastes on fluoride uptake, surface roughness, and microhardness of six ion-releasing restorative dental materials, including glass hybrids (EQUIA Forte HT with and without coating), glass ionomer cements (Fuji IX), resin-modified GICs (Fuji II LC), alkasites (Cention Forte), and ion-releasing composites (Luminos UN and Activa). Specimens were prepared and subjected to a four-day brushing protocol using six toothpastes with varying fluoride formulations (NaF, SnF2, SMFP) and concentrations. Fluoride uptake was assessed by measuring fluoride release using an ion-selective electrode, while surface roughness and microhardness were assessed before and after brushing. Results revealed significant variations in fluoride uptake, with Fuji IX and EQUIA Forte HT showing the highest release, particularly when brushed with NaF-based toothpastes (Duraphat 5000 and 2800). Surface roughness increased post-brushing, with the greatest changes observed in Activa, while microhardness decreased across most materials, except for coated EQUIA Forte HT, which exhibited improved compactness. Resin-based composites, such as Luminos UN and Activa, demonstrated lower fluoride uptake and minimal changes in microhardness compared to GICs. The findings underscore the importance of material composition and toothpaste formulation in influencing fluoride dynamics, surface properties, and mechanical performance of restorative materials. Full article

Objectives: The fluoride-releasing properties of restorative materials are crucial for the prevention of secondary caries as these can act as fluoride reservoirs. Hence, the present study aimed to investigate, assess, and compare the impact of time, temperature, and storage conditions on the fluoride release of silorane-based composites (SBCs) and methacrylate-based composites (MBCs), and also evaluate the variation in their reuptake of fluoride (after recharge). Methods: SBC and MBC test samples of 10 mm × 2 mm dimensions were prepared and tested for fluoride release and recharge in distilled water and artificial saliva at temperatures of 4 °C, 37 °C, and 55 °C. The amount of fluoride released (at 1, 7, 14, and 28 days) and re-released after recharge (with 5000 ppm neutral sodium fluoride (NaF) solution for 5 min at 1, 3, and 7 days for 3 weeks) were studied with the help of a fluoride-selective ion electrode. Results: SBCs had a greater release of fluoride at low temperature in artificial saliva (0.07 ± 0.03) when compared to MBCs (0.04 ± 0.005). Fluoride release increased on day 7 but decreased over time (p < 0.05). Fluoride re-release was greater in MBCs than SBCs and it increased with time (p < 0.05). Conclusion: The amount of fluoride release and recharge depends on the time interval, temperature, and storage condition. These restorative materials can serve as fluoride reservoirs and contribute to sustained fluoride release in oral fluids, thereby preventing the initiation of secondary caries and the failure of restorations. In addition, it may assist in developing measures to improve fluoride delivery for topical applications. Full article

The electrochemical carbon dioxide reduction reaction (CO₂RR) represents a promising approach for achieving CO₂ resource utilization. Carbon-based materials featuring single-atom transition metal-nitrogen coordination (M-N_x) have attracted considerable research attention due to their ability to maximize catalytic efficiency while minimizing metal atom usage. However, conventional synthesis methods often encounter challenges with metal particle agglomeration. In this study, we developed a Ni-doped polyvinylidene fluoride (PVDF) fiber membrane via electrospinning, subsequently transformed into a nitrogen-doped three-dimensional self-supporting single-atom Ni catalyst (Ni-N-CF) through controlled carbonization. PVDF was partially defluorinated and crosslinked, and the single carbon chain is changed into a reticulated structure, which ensured that the structure did not collapse during carbonization and effectively solved the problem of runaway M-Nx composite in the high-temperature pyrolysis process. Grounded in X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS), nitrogen coordinates with nickel atoms to form a Ni-N structure, which keeps nickel in a low oxidation state, thereby facilitating CO₂RR. When applied to CO₂RR, the Ni-N-CF catalyst demonstrated exceptional CO selectivity with a Faradaic efficiency (FE) of 92%. The unique self-supporting architecture effectively addressed traditional electrode instability issues caused by catalyst detachment. These results indicate that by tuning the local coordination structure of atomically dispersed Ni, the original inert reaction sites can be activated into efficient catalytic centers. This work can provide a new strategy for designing high-performance single-atom catalysts and structurally stable electrodes. Full article

Cortisol, a steroid hormone, is closely associated with human mental stress. The rapid, real-time, and continuous detection of cortisol using wearable devices offers a promising approach for individual mental health. These devices must exhibit high sensitivity and long-term stability to ensure reliable performance. This study developed a wearable electrochemical sensor based on molecularly imprinted polymer (MIP) technology for real-time and dynamic monitoring of cortisol in sweat. A flexible gold (Au) electrode with interfacial hydrophilic treatment was employed to construct a highly stable electrode. The integration of a silk fibroin/polyvinylidene fluoride (SF/PVDF) composite membrane facilitates directional sweat transport, while liquid metal bonding enhances electrode flexibility and mechanical anti-delamination capability. The sensor exhibits an ultrawide detection range (0.1 pM to 5 μM), high selectivity (over 100-fold against interferents such as glucose and lactic acid), and long-term stability (less than 3.76% signal attenuation over 120 cycles). Additionally, a gradient modulus design was implemented to mitigate mechanical deformation interference under wearable conditions. As a flexible wearable device for cortisol monitoring in human sweat, the sensor’s response closely aligns with the diurnal cortisol rhythm, offering a highly sensitive and interference-resistant wearable solution for mental health monitoring and advancing personalized dynamic assessment of stress-related disorders. Full article