The effect of surface conditioning techniques on the shear bond strength of zirconia-reinforced lithium silicate ceramic following adhesive cementation - An in vitro study.

Aim: The aim of this study was to determine the effect of different surface conditioning techniques on the bond strength between zirconia-reinforced lithium silicate (ZLS) ceramics and resin cement. Materials and Methods: Fifty samples of ZLS ceramic were used and allotted into five groups with 10 samples per group based on the type of surface conditioning technique. The ceramic specimens were crystallized and embedded into acrylic resin. The five groups were group 1 (negative control-without surface treatment); group 2 (10% hydrofluoric [HF] acid + silanization); group 3 (10% HF acid only); group 4 (self-etching ceramic primer [SECP]); and group 5 (experimental laboratory sealing of the conditioned surface). Resin cylinders were bonded using self-adhesive resin cement and were subjected to thermocycling after 24 h storage. The shear bond strength was tested with a universal testing machine. Statistical Analysis Used: One-way ANOVA was used for comparing five groups (P < 0.05 was considered significant). Results: Group 4 showed the highest mean bond strength value (23.4 MPa ± 2.21 MPa). A statistically significant difference was noted between group 4 and all the other groups tested in the study (P < 0.05). Conclusion: It can be concluded that the SECP can be considered an alternative to the conventional protocol of HF acid and silane application for the surface conditioning of ZLS ceramic.

Unmasking Fluorinated Moieties on the Surface of Hydride-Terminated Silicon Nanoparticles.

Despite the widespread use of hydrofluoric acid (HF) in the preparation of silicon surfaces, the true nature of fluorinated surface species remains unclear. Here, we employ an array of characterization techniques led by solid-state nuclear magnetic resonance spectroscopy to uncover the nature of fluorinated moieties on the surface of hydride-terminated silicon nanoparticles (H-SiNPs). A structural model that explains the observed trends in 19F and 29Si magnetic shielding is proposed and further supported by quantum chemical computations. Fluorine is incorporated into local oxidation domains on the surface and clustered at the interface of the oxide and surrounding hydride-terminated surface. Silicon sites capped by a single fluorine are also identified by their distinct 19F and 29Si chemical shifts, providing insight into how fluorine termination influences the electronic structure. The extent of fluorine passivation and the effects of fluorine on the optical properties of SiNPs are also discussed. Finally, challenges associated with Teflon contamination are highlighted that future explorations of nanomaterials may have to contend with.

Eliminating Hydrogen Fluoride through Piperidine-Doped Separators for Stable Li Metal Batteries with Nickel-Rich Cathodes.

Hydrofluoric acid (HF)-induced electrode and interfacial structure degeneration poses a significant challenge for high-voltage lithium metal batteries (LMBs). To address this issue, we propose a separator strategy that involves decorating a regular polyethylene (PE) separator with molecular sieves (TW) impregnated with piperidine (PI). The porous structure of the TW serves as a reaction chamber for PI and HF. As a result, the HF content in the controlled electrolyte with 500 ppm H2O (ELE-500) is notably reduced when using TW@PI-PE separators, thereby shielding nickel-rich cathodes from HF etching. Simultaneously, due to the hydrolysis of Li salts, and the inertness of PI towards H2O, a uniform lithium fluoride (LiF)-rich solid electrolyte interphase can form on the Li metal anode, further mitigating dendrite formation. The lifespan of the symmetric Li cell using the TW@PI-PE separator is doubled in ELE-500, exhibiting stable 500-hour cycles at 3 mA cm-2 and 3 mAh cm-2. Additionally, with the effective limitation of transition metal (TM) dissolution, the 4.6-V LMBs employing a LiNi0.8Co0.1Mn0.1O2 cathode maintain an 81% capacity retention over 100 cycles, even in ELE-1000. The innovative TW@PI system presented here offers a fresh perspective for future research aimed at eliminating HF in LMBs.

Hydrofluoric Acid-Free Broadband Near-Infrared Phosphors K2LiMF6:Cr3+ with Zero-Thermal Quenching: Structure, Luminescence, and Application.

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are considered promising light sources for night vision, food analysis, biomedicine, and plant growth. Yet, the application potential of this technology is vulnerable to the function degradation of the phosphors used, such as thermal quenching, which needs to be addressed urgently. Herein, the NIR phosphors K2LiMF6:Cr3+ (M = Al, Ga, In) with a cubic double-perovskite structure synthesized by a green hydrofluoric acid-free hydrothermal method exhibit outstanding thermal stability. Under 450 nm excitation, the as-synthesized K2LiMF6:Cr3+ phosphors all exhibited broadband NIR emission covering 650-1000 nm peaking at 755-780 nm. The prepared K2LiAlF6:Cr3+ phosphor shows a unique zero-thermal quenching performance (I423 K/I298 K = 102%). The comprehensive effects of a wide band gap, large thermal energy barrier, weak electron-phonon coupling effect, and high structural rigidity are responsible for the suppression of thermal quenching in this material. The output power of the NIR pc-LED device reached 285 mW at 100 mA. This series of phosphors has promise in night vision and bioimaging applications.

Synthesis of Hydrofluoric (HF) Acid Free, Two-Dimensional (2D) Tantalum Carbide MXene Nanosheets and Quantum Dots.

MXenes are two-dimensional (2D) transition metal-based carbides, nitrides, and carbonitrides that are synthesized from its precursor MAX phase. The selective etching of the "A" from the MAX phase yields multi-functional MXenes that hold promise in a wide range of energy-based applications and biomedical applications. Based on its intended application, MXenes are prepared as multilayered sheets, monolayer flakes, and quantum dots. Conventionally, MXenes are prepared using hydrofluoric (HF) acid etching; however, the use of HF impedes its effective use in biomedical applications. This calls for the use of nontoxic HF-free synthesis protocols to prepare MXenes safe for biological use. Therefore, we have discussed a facile process to synthesize biocompatible, HF-free MXene nanosheets and quantum dots.

Effect of hydrofluoric acid and self-etch ceramic primers on the flexural strength and fatigue resistance of glass ceramics: A systematic review and meta-analysis of in vitro studies.

This systematic review evaluated the effect of different hydrofluoric acid (HF) etching regimens and a self-etch ceramic primer (SECP) on the flexural strength (FS) and fatigue failure load (FFL) of glass-ceramic materials.The identification of relevant studies was conducted by two authors in five databases: PubMED, Scopus, Web Of Science, LILACS and Virtual Health Library (BVS) until July 2022 with no year limit. The analysis was conducted in RevMan 5.4.1 Software (Cochrane Collaboration) using Random effect model at 5 %. The risk of bias of the included studies were assessed. From the 5349 articles identified, 34 were included for quantitative analysis. Meta-analysis showed that for predominantly glassy ceramics, etching with HF 5 % had no significant impact on FS, however, HF acid etching with concentrations greater than 5 % negatively impacted FS. For lithium disilicate glass-ceramics (LDGC) HF acid etching, negatively influenced FS, while increasing the FFL. HF etching negatively affected FS of hybrid ceramics. The self-etch ceramic primer and HF acid etching showed a similar impact on FFL and FS. This meta-analysis indicates that the impact of SECP and HF acid etching on the mechanical behavior of glass ceramics is material-dependent.

Effect of different design and surface treatment on the load-to-failure of ceramic repaired with composite.

Glass ceramics are widely used to manufacture esthetic veneers, inlays, onlays, and crowns. Although the clinical survival rates ofglass-ceramic restorations arefavorable,fractures or chips are common. Certain cases can be repaired with direct composite. AIM: The aim of this study was to investigate the interaction effect of different designs and surface treatments on the load-to-failure of lithium disilicate glass-ceramic repaired with nanofilled composite. MATERIALS AND METHOD: Lithium-disilicate glass-ceramic slabs (IPS e.max Press, Ivoclar Vivadent) with three different designs of the top surface (flat, single plateau, or doubleplateau) (n=U) received 'no treatment', '5% HF etching', or "AI2O3 sandblasting". HF-etched and sandblasted slabs also received silane and universal one-step adhesive application. All slabs were incrementally repaired with nanofilled composite (Filtek Z350, 3M ESPE) up to6 mm above the highest ceramic top plateau. Specimens were stored in artificial saliva at 37 °C for 21 days and then subjected to 1,000 thermocycles between 5 and 55 °C. The interface composite-ceramic of each specimen was tensile tested until failure in a universal testing machine and the mode of failure was determined under a stereomicroscope. The ceramic surface morphology of one representative tested specimen from each subgroup (design/surface treatment) was observed through scanning electron microscopy (SEM). RESULTS: Regardless of ceramic design, the absence of surface treatment resulted in significantly lower load-to-failure values. No significant differences in load-to-failure values were observed between HF-etched and sandblasted specimens for the flat design; however, HF etching resulted in significantly higher load-to-failure values than sandblasting for both single plateau and double plateau designs. The majority (60%) of HF-etched specimens with single plateau or double plateau presented mixed failures. SEM photomicrographs showed that HF-etched specimens had smoother surfaces than sandblasted specimens. CONCLUSION: The surface treatment of a defective lithium disilicate glass-ceramic restoration has more influence than its macroscopic design on the retention of the composite repair. HF etching seems to provide higher bond strength to the composite repair.

Embora fraturas e lascamento de restauragoes vitrocerámicas sejam comuns, alguns casos podem ser reparados com compósito direto. OBJETIVO: investigar o efeito da interagao de diferentes formas e tratamentos de superficie na carga de ruptura de uma vitrocerámica reforgada com dissilicato de litio reparada com compósito nanoparticulado. MATERIAIS E MÉTODOS: A superficie superior de espécimes de vitroceramica (IPS e.max Press, Ivoclar Vivadent) foi preparada com tres formas (plana, plato único, ou duplo) e recebeu (n=11): 'nenhum tratamento', 'condicionamento com ácido hidrofluoridrico 5%', ou 'jateamento com AfOf. Ambos espécimes condicionados e jateados receberam silano e adesivo universal. Todos os espécimes foram reparados incrementalmente com compósito (Filtek Z350, 3M ESPE) até6 mm acima do plato cerámico mais alto, armazenados em saliva artificial á 37 °C por 21 dias, e submetidos á 1.000 termociclos (5 e 55 °C). A interface compósito-cerámica de cada amostra foi testada á tragao até sua falha em máquina universal e o modo de falha foi determinado com estereomicroscópio. A morfologia da superficie de uma amostra representativa de forma/tratamento de superficie foi observada através de microscopia eletronica de varredura (MEV). RESULTADOS: Independentemente da forma ceramica, a ausencia de tratamento superficial resultou em valores de carga de ruptura significativamente menores. Nao foi observada differenga significativa entre os espécimes planos condicionados ou jateados; no entanto, o condicionamento resultou em valores significativamente maiores que o jateamento para espécimes com plato único e duplo. A maioria (60%) dos espécimes condicionados e com plato único ou duplo apresentou falhas mistas. Imagens SEM demonstraram rugosidade superficial mais regular dos espécimes condicionados que os jateados. CONCLUSÕES: O tratamento superficial de uma restauragao defeituosa de vitrocerámica reforgada por dissilicato de litio tem maior influencia na retengao do reparo de compósito do que sua forma macroscópica; ainda, o condicionamento com ácido hidrofluoridrico parece proporcionar maior resistencia de uniao ao reparo com compósito.

A Rare Case of Extensive Hydrofluoric Acid Burn.

Hydrofluoric acid (HF) is a strongly corrosive, highly toxic, and highly dangerous mineral acid. Burns with over 1% TBSA caused by anhydrous HF can lead to deep tissue damage, hypocalcemia, poisoning, and even death. In recent years, HF has become one of the most common substances causing chemical burns and ranks as the leading cause of death from chemical burns. Herein, we report a rare case with 91% TBSA burns caused by 35% HF. The patient developed complications such as shock, severe hypocalcemia, metabolic acidosis, and respiratory failure. Multidisciplinary team consultation (burns, respiratory medicine, nephrology, infectious disease, and pharmacy) was performed immediately after admission. An individualized diagnosis and treatment plan were developed for the patient. The patient was given intensive care, blood volume monitoring, tracheotomy, fluid resuscitation, continuous blood purification, anti-infective and analgesic treatments, intravenous and percutaneous calcium supplementation, early rehabilitation training, psychological rehabilitation, and other treatments. To prevent the wound from deepening, large-area debridement and skin grafting were performed early after the injury. A large dose of 10% calcium gluconate was injected into the patient in divided doses, and the wound was continuously treated with wet dressings. Multiple surgical debridements, negative pressure wound treatment, biological dressings, and Meek skin grafting were performed. After most of the wounds (approximately 85% TBSA) healed, the patient was discharged from the hospital and continued to undergo dressing changes at a local hospital. The patient was followed up 3 months after discharge. All the wounds healed well, and the patient basically regained functional independence in daily life.

A dilute sodium hydroxide technique for radiolarian extraction from cherts.

Radiolarians have been used to determine geological ages and have contributed markedly to our understanding of Earth's history. Hydrofluoric acid (HF) has traditionally been used to extract radiolarian fossils from siliceous deposits (i.e., radiolarian cherts), but this acid is strictly regulated because of environmental and human health concerns. Here we report on the successful extraction of radiolarians from cherts using a low-concentration NaOH solution (1 mol/L NaOH) as an alternative to HF. The degree of chert dissolution in NaOH is strongly temperature-dependent and is limited at < 80 °C. However, even a 1 mol/L NaOH solution is sufficient to dissolve chert at 100 °C. Our new NaOH method yields better-preserved radiolarian fossils compared with the conventional HF method. The 1 mol/L NaOH solution is less hazardous, easier to handle, and has fewer effects on the environment and human health than HF. Therefore, this method can be widely used for research and teaching purposes in studies of radiolarian fossils, even in institutions where HF cannot be used owing to chemical restrictions.

Effectiveness of Different Etching Agents on Enamel Surface and Shear Bond Strength: An In Vitro Evaluation.

Background Enamel etching is of utmost importance during the orthodontic bonding procedure. Phosphoric acid, hydrofluoric acid, and citric acid are used in specific concentrations to create surface irregularities on enamel surfaces, enhancing the bond strength of the orthodontic attachment. Therefore, it is essential to evaluate the type of etchant for reliable orthodontic bracket bonding with minimal damage to the enamel surface. Aims and objectives This study aimed to investigate the morphological changes on the enamel surface after treatment with different surface etchants, assess the depth of penetration, and evaluate the shear bond strength (SBS) of orthodontic brackets. Materials and methods One hundred and one extracted premolar teeth were used to investigate morphological changes on the enamel surface treated with 37% phosphoric acid, 11% hydrofluoric acid, and 20% citric acid. It was evaluated on a scanning electron microscope (Jeol Scientific Equipment, Jeol Limited, Akishima, Japan), and the SBS of brackets on enamel treated with different etching agents was evaluated using an Instron Universal Testing Machine (UTM; Instron Model: 5982, Universal Testing Systems, Norwood, MA). Group A had 60 test samples. Group B had 40 test samples. One control without any acid etching was used in both groups. Subgroup A1 (n = 30) was evaluated for surface characteristics of acid-etched enamel. Subgroup A2 was assessed for the penetration depth of various etchants. Group B (n = 40) was tested for SBS. The results were tabulated and analyzed using IBM SPSS Statistics, version 20.0 (IBM Corp., Armonk, NY). Post hoc Tukey HSD test and one-way analysis of variance were used to assess SBS and penetration depth of etchants (P ≤ 0.05). Pearson's correlation test was used to correlate SBS, etching pattern, and penetration depth. The chi-square test was used to test the frequency of types of etching patterns.  Results Intergroup correlations between etching depth, etching pattern evaluated on SEM, and SBS evaluated on the UTM showed a high statistical correlation between etching depth & SBS, etching depth & etching pattern, and SBS & etching pattern between A1, A2, and group B (P ≤ 0.001). A highly significant negative correlation between SBS & etching pattern (P = 0.42) was observed among intra-group correlation. Non-significant correlations were found between etching depth & SBS and etching depth & etching pattern within the 20% citric acid etch group (P = 0.370 and 0.141, respectively). Conclusion Penetration depth obtained was highest with 11% hydrofluoric acid, followed by 37% phosphoric acid and 20% citric acid. In addition, 11% hydrofluoric acid showed the highest bond strength. Acid etching showed better penetration depth and bond strength than control.

Effect of Combined Application of Hydrofluoric and Phosphoric Acids and Active Irrigation with a Microbrush on Shear Bond Strength of Lithium Disilicate Ceramics to Enamel.

Background: This study assessed the effect of combined application of hydrofluoric (HF) acid and phosphoric acid (PA) and active irrigation (AI) with a microbrush on shear bond strength (SBS) of lithium disilicate (LDS) ceramics to enamel. Materials and Methods: This in vitro study was conducted on 40 extracted teeth that received enamel preparation with a #12 cylindrical bur. Forty IPS e.max LT rods (3mm diameter, 6mm height) were fabricated and randomly assigned to four groups (n = 10) for surface treatment with 5% HF (group 1), 5% HF and AI with a microbrush for 20 seconds (group 2), 5% HF and 32% PA (group 3), and 5% HF and 32% PA plus AI with a microbrush for 20 seconds (group 4). Silane and Choice 2 cement were used for bonding rods to enamel. The SBS was measured by a universal testing machine. Data were analyzed by two-way analysis of variance (ANOVA), Bonferroni, and Chi-square tests (alpha = 0.05). Results: Group 4 had the highest SBS, and group 1 had the lowest SBS (P < 0.05). Group 2 had a significantly higher SBS than group 1, and group 4 had a significantly higher SBS than group 3. AI with a microbrush significantly increased the SBS (P < 0.05), but the application of PA caused no significant change in SBS (P > 0.05). The interaction effect of PA and AI on SBS was not significant (P > 0.05). Conclusion: The application of PA in addition to 5% HF acid caused no significant change in the SBS of LDS ceramic to enamel. However, AI with a microbrush significantly increased the SBS.

Bond Strength to Lithium-Disilicate Ceramic after Different Surface Cleaning Approaches.

PURPOSE: To evaluate the effect of different lithium-disilicate (LiSi) glass-ceramic surface decontamination procedures on the shear bond strength (SBS) to resin cement. MATERIALS AND METHODS: Seventy CAD/CAM LiSi ceramic specimens (IPS e.max CAD, Ivoclar) were cut and sintered. Fifty specimens were treated with 5% hydrofluoric acid (HF) for 20 s, while 20 were left untreated. All 70 specimens were then contaminated with human saliva and try-in silicone paste. The following surface cleaning methods were investigated (n = 10): C: water rinsing (control); PA: 37% H3PO4 etching for 20 s; E: 70% ethanol applied for 20 s; CP: cleaning paste (Ivoclean, Ivoclar) brushed for 20 s; HFSEP: self-etching ceramic primer (Monobond Etch&Prime, Ivoclar) rubbed for 20 s; HF: 5% HF applied for 20 s or no HF etching prior to contamination; SEP: self-etching ceramic primer rubbed for 20 s and no HF etching prior to contamination. Composite cylinders were created and luted with an adhesive resin cement to the decontaminated surfaces. After storage for 24 h at 37°C, the SBS test was conducted. Two fractured specimens per group were observed under SEM to perform fractographic analysis. The data were statistically analyzed with p set at <0.05. RESULTS: The type of surface cleaning approach influenced bond strength (p < 0.001). HFSEP, SEP, and HF attained higher SBS (p < 0.001) compared to other groups. None of the approaches were able to completely remove contaminants from the ceramic surfaces. SEM images showed residual traces of contaminants on CP-treated surfaces. CONCLUSIONS: The self-etching ceramic primer enhanced bond strength to contaminated LiSi ceramic surfaces, irrespective of previous treatment with hydrofluoric acid.

Effect of different design and surface treatment on the load-to-failure of ceramic repaired with composite / Efeito de diferentes tratamentos de superficie e formas do preparo de cerámicas na resistencia de uniao de reparos em resina composta

ABSTRACT Glass ceramics are widely used to manufacture esthetic veneers, inlays, onlays, and crowns. Although the clinical survival rates ofglass-ceramic restorations arefavorable,fractures or chips are common. Certain cases can be repaired with direct composite. Aim The aim of this study was to investigate the interaction effect of different designs and surface treatments on the load-to-failure of lithium disilicate glass-ceramic repaired with nanofilled composite. Materials and Method Lithium-disilicate glass-ceramic slabs (IPS e.max Press, Ivoclar Vivadent) with three different designs of the top surface (flat, single plateau, or doubleplateau) (n=U) received 'no treatment', '5% HF etching', or "AI2O3 sandblasting". HF-etched and sandblasted slabs also received silane and universal one-step adhesive application. All slabs were incrementally repaired with nanofilled composite (Filtek Z350, 3M ESPE) up to6 mm above the highest ceramic top plateau. Specimens were stored in artificial saliva at 37 °C for 21 days and then subjected to 1,000 thermocycles between 5 and 55 °C. The interface composite-ceramic of each specimen was tensile tested until failure in a universal testing machine and the mode of failure was determined under a stereomicroscope. The ceramic surface morphology of one representative tested specimen from each subgroup (design/surface treatment) was observed through scanning electron microscopy (SEM). Results Regardless of ceramic design, the absence of surface treatment resulted in significantly lower load-to-failure values. No significant differences in load-to-failure values were observed between HF-etched and sandblasted specimens for the flat design; however, HF etching resulted in significantly higher load-to-failure values than sandblasting for both single plateau and double plateau designs. The majority (60%) of HF-etched specimens with single plateau or double plateau presented mixed failures. SEM photomicrographs showed that HF-etched specimens had smoother surfaces than sandblasted specimens. Conclusion The surface treatment of a defective lithium disilicate glass-ceramic restoration has more influence than its macroscopic design on the retention of the composite repair. HF etching seems to provide higher bond strength to the composite repair.

RESUMO Embora fraturas e lascamento de restauragoes vitrocerámicas sejam comuns, alguns casos podem ser reparados com compósito direto. Objetivo investigar o efeito da interagao de diferentes formas e tratamentos de superficie na carga de ruptura de uma vitrocerámica reforgada com dissilicato de litio reparada com compósito nanoparticulado. Materials e Método A superficie superior de espécimes de vitroceramica (IPS e.max Press, Ivoclar Vivadent) foi preparada com tres formas (plana, plato único, ou duplo) e recebeu (n=11): 'nenhum tratamento', 'condicionamento com ácido hidrofluoridrico 5%', ou 'jateamento com AfOf. Ambos espécimes condicionados e jateados receberam silano e adesivo universal. Todos os espécimes foram reparados incrementalmente com compósito (Filtek Z350, 3M ESPE) até6 mm acima do plato cerámico mais alto, armazenados em saliva artificial á 37 °C por 21 dias, e submetidos á 1.000 termociclos (5 e 55 °C). A interface compósito-cerámica de cada amostra foi testada á tragao até sua falha em máquina universal e o modo de falha foi determinado com estereomicroscópio. A morfologia da superficie de uma amostra representativa de forma/tratamento de superficie foi observada através de microscopia eletronica de varredura (MEV). Resultados Independentemente da forma ceramica, a ausencia de tratamento superficial resultou em valores de carga de ruptura significativamente menores. Nao foi observada differenga significativa entre os espécimes planos condicionados ou jateados; no entanto, o condicionamento resultou em valores significativamente maiores que o jateamento para espécimes com plato único e duplo. A maioria (60%) dos espécimes condicionados e com plato único ou duplo apresentou falhas mistas. Imagens SEM demonstraram rugosidade superficial mais regular dos espécimes condicionados que os jateados. Conclusoes O tratamento superficial de uma restauragao defeituosa de vitrocerámica reforgada por dissilicato de litio tem maior influencia na retengao do reparo de compósito do que sua forma macroscópica; ainda, o condicionamento com ácido hidrofluoridrico parece proporcionar maior resistencia de uniao ao reparo com compósito.

Surface property changes observed in zirconia during etching with high-concentration hydrofluoric acid over various immersion times.

This study investigated the degree of phase transformation, surface roughness, and bond strength of zirconia immersed for various times in a 40% hydrofluoric acid (HF) solution. Non-etched sintered zirconia specimens were used as the control, while experimental groups were etched with a 40% HF solution for 5, 10, 20, 40, 80, 160 and 320 min. In each of the control and experimental groups, five specimens for X-ray diffraction analysis, four for surface morphology and surface roughness analysis, and ten for bonding strength measurement were used. As a result, the surface roughness of zirconia increased as the application time increased during the 40% HF etching, but the bond strength between zirconia and resin cement did not increase proportionally. The phase transformation from tetragonal to monoclinic also gradually increased with application time.

Application of MXene-Based Materials for Cathode in Lithium-Sulfur Batteries.

The lithium-sulfur (Li-S) batteries have a high theoretical specific capacity of 1675 mAh ⋅ g-1 and have become the most promising high-energy storage system for the next generation batteries technology. However, their applications are hindered by insulated feature and volume expansion of sulfur, as well as the "shuttle effect" of polysulfides. MXenes own metallic conductivity and strong ability of polysulfides adsorption. Besides, their unique two-dimensional (2D) structure, large specific surface area, abundant functional groups, and adjustability are beneficial to overcome the drawbacks of the sulfur cathode. In this review, different mainstream preparation methods and excellent properties of MXenes are summarized. Significant achievements and recent progress of MXene-based cathodes and interlayers applied to Li-S cathodes are concluded later. Finally, the challenges, possible solutions and potential applications of MXenes for Li-S batteries are also presented.

Hydrofluoric acid concentration and etching time affect differently the microstructure and surface properties of pressed lithium disilicate glass ceramics.

OBJECTIVE: To evaluate the effect of different hydrofluoric acid concentrations and etching times on the surface, chemical composition and microstructure of lithium disilicate. MATERIAL AND METHODS: Ninety specimens of pressed lithium disilicate (LDS) were obtained (IPS e.max Press, Rosetta SP and LiSi Press). The specimens of each material were divided in two groups according to the hydrofluoric acid concentration: 5% and 10% (n = 15/group), and subdivided according to the etching time: 20, 40 and 60 s (n = 5/group). Crystalline evaluations and chemical composition were performed through x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), respectively. Microstructural analyses were performed by scanning electron microscope (SEM), surface roughness (Ra), and material thickness removal evaluation. Thickness removal and Ra data were analyzed by ANOVA and Tukey test (p < 0.05). RESULTS: XRD demonstrated characteristic peaks of lithium disilicate crystals, lithium phosphate and of a vitreous phase for all materials. EDS identified different compositions and SEM confirmed different surface responses to acid etching protocols. Material and etching time influenced Ra and material thickness removal (p < 0.05). CONCLUSION: Hydrofluoric acid concentration and etching time affect the surface characteristics of LDS differently. LiSi Press presented higher resistance to hydrofluoric acid etching compared to e.max Press and Rosetta SP. CLINICAL SIGNIFICANCE: Applying the appropriate etching protocol is pivotal to avoid excessive material removal and to prevent jeopardize the mechanical and optical properties of the material.

Diphoterine, an amphoteric rinsing solution, reduces hydrofluoric acid injuries in an ex vivo pigskin model.

Hydrofluoric acid (HF) is a ubiquitous industrial chemical that is particularly hazardous because of the potential for systemic effects and the induction of severe cutaneous necrosis after contact with the skin. Minimizing skin injury requires decontaminating the affected area promptly with an emergency rinsing solution. Few experimental studies have objectively characterized rinsing solutions such as Diphoterine (DP). Here we develop an ex vivo pigskin model to study and compare the efficacy of rinsing solutions as initial decontaminating agents to stop the progression of skin lesions after HF splashing. The pigskin model shows an immediate local response to HF at varying concentrations and exposure times. We then exposed the pigskin biopsies to 3.75% HF for 1 min and rinsed them with different solutions, including water, 0.9% NaCl solution (saline), 10% calcium gluconate (CaG), Hexafluorine (HXF), and DP. We found DP to be a more effective agent for decontaminating HF lesions than water, saline, and CaG. DP had a similar efficacy as HXF, an emergency rinsing solution used specifically for decontaminating HF-exposed skin. This study shows that skin exposed to HF must be treated quickly from the first minute of exposure.

Ophthalmic manifestations and management considerations for emerging chemical threats.

Chemical agents have been utilized for centuries in warfare and pose a health threat to civilians and military personnel during armed conflict. Despite treaties and regulations against their use, chemical agent exposure remains a threat and measures to understand their effects and countermeasures for systemic and organ-specific health are needed. Many of these agents have ocular complications, both acute and chronic. This mini-review focuses on key chemical agents including vesicants (mustards, lewisite), nerve agents (sarin, VX), knockdown gasses (hydrogen cyanide), and caustics (hydrofluoric acid). Their ophthalmic manifestations and appropriate treatment are emphasized. Acute interventions include removal of the source and meticulous decontamination, as well as normalization of pH to 7.2-7.4 if alteration of the ocular pH is observed. Besides vigorous lavage, acute therapies may include topical corticosteroids and non-steroid anti-inflammatory therapies. Appropriate personal protective equipment (PPE) and strict donning and doffing protocols to avoid healthcare provider exposure are also paramount in the acute setting. For more severe disease, corneal transplantation, amniotic membrane graft, and limbal stem cell transplantation may be needed. Orbital surgery may be required in patients in whom cicatricial changes of the ocular surface have developed, leading to eyelid malposition. Multidisciplinary care teams are often required to handle the full spectrum of findings and consequences associated with emerging chemical threats.

The effect of hydrofluoric acid treatment on the repair strength of polyamide denture base materials: An in vitro study.

PURPOSE: Although polymethylmethacrylate (PMMA) dentures can be repaired using autopolymerizing acrylic resin, achieving it using polyamides is difficult. This study aimed to achieve acceptable bond strength using autopolymerizing acrylic resin by applying surface treatments to the polyamide denture base material. MATERIALS AND METHODS: Thirty-six disc-shaped samples (27 polyamide, 9 PMMA) were prepared. Based on the surface treatment applied, the polyamide samples were divided into three groups: No surface treatment (n = 9), tribochemical silica coating + silane coupling agent (n = 9), and 9% hydrofluoric acid + tribochemical silica coating +silane coupling agent (n = 9). PMMA specimens received no surface treatment. Polyamide and PMMA surfaces had auto-polymerizing acrylic resin bonded on them, and then a shear bond strength test was performed between them after aging. The Kruskal-Wallis test was used, and statistical significance was set at p < 0.05. RESULTS: PMMA had the highest shear bond strength, the untreated polyamide group had the lowest shear bond strength, and the difference was significant (p < 0.05). The group treated with 9% hydrofluoric acid, tribochemical silica coating, and silane coupling agent exhibited the highest shear bond strength of the polyamide groups, and the bond strength in this group was comparable to the PMMA specimens (p > 0.05). CONCLUSIONS: The polyamide denture repair strength can be improved by 9% hydrofluoric acid, tribochemical silica coating, and silane coupling agent application to the polyamide surface.

Comparative Evaluation of Fluoride Release and Compressive Strength of Biodentine Modified Using Sodium Fluorosilicate and Hydrofluoric Acid: An In-Vitro Study.

Introduction Calcium trisilicate derivatives have widely been used as dentin and enamel substitutes recently. These cements have excellent biological properties, but they do not show fluoride release. The release of fluoride from dental materials is a very important property of a material in restorative applications as fluoride confers antibacterial and anti-cariogenic properties. This study thus attempts to incorporate fluoride in the form of sodium fluorosilicate and hydrofluoric acid into Biodentine to assess its fluoride-releasing properties. Methods Biodentine was modified by adding 7% sodium fluorosilicate in the powder and 10% hydrofluoric acid to the liquid. Fluoride release was measured using a sodium 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalenedisulfonate (SPADNS) spectrophotometer after 1, 3, 7, 14, 21, and 28 days. The compressive strength of the modified material was measured using a universal testing machine. Results Fluoride release was found to be higher in the group that had both powder and liquid modified than in groups in which either of the components were modified. The difference was found to be statistically significant (p<0.001). Conclusion Incorporation of fluoride in Biodentine is feasible with acceptable release of fluoride without adversely affecting the compressive strength of the Biodentine.