Hexafluorosilicate Research Articles

Laser and remineralising agents in dental erosion: a systematic review and meta-analysis.

This systematic review aimed to evaluate, by means of statistical comparison between selected studies, the effectiveness of laser irradiation on dental erosion applied alone or in combination with anti-erosive agents (fluoride, Acidulated phosphate fluoride APF and CPP-amorphous calcium fluoride phosphate CPP-ACFP), through optical profilometry and microhardness measurement. The searching strategy was conducted according to the International PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, to answer research ques-tions regarding the effectiveness of lasers used in the context of dental erosion (such as Nd:YAG, CO2, Er:YAG, Er,Cr:YSGG, Diode, and Argon Ion lasers). A comprehensive and unrestricted sys-tematic searching was performed using the electronic databases of PubMed and Cochrane Library, for all articles published up to the end of January 2023. The review record was registered by the International prospective register of systematic reviews (PROSPERO) under the identification number CRD408639. Change in microhardness for the lasers group, irrespective of the type of laser used in the sample, was significantly greater compared with the one in the control group. Regards microhardness, the combination of Laser and APF gel showed promising results compared to APF gel agent.

Application of Response Surface Methodology for concentration of fluorosilicic acid by extraction technique with benzyl alcohol as extractant

As a kind of alternative of natural fluorinated minerals and raw material for producing anhydrous hydrogen fluoride, fluorosilicic acid has attracted more and more attention. In order to raise its utilization rate, dilute fluorosilicic acid solution coming from chemical enterprises needs to be concentrated. The extraction technology with benzyl alcohol as extraction agent was used to concentrating fluorosilicic acid aqueous solution. In order to determine the optimizing operation conditions of the extracting process, single - factor experiments were carried out to confirm the significant affecting factors and their operating range. Then the Response Surface Methodology (RSM) was conducted to accomplish regression of a nonlinear quadratic polynomial model to the experimental data and statistical analysis. Based on these studies, the optimal technical parameters of extracting process are acquired by optimization of the model using the Design-Expert 13 software. The statistical analysis for the fitting response surface quadratic equation model indicated that the model was reliable and accurate with very low p-values (<0.0001), the predicted values with the model equation had remarkable consistency in experimental data. By a great number of optimizations carried out with the Design Expert 13 software based on the fitting model equation, the optimal extractive processing conditions for concentrating fluorosilicic acid aqueous solution were obtained: the phase ratio 7, the extraction time 120.11 min and the extraction temperature 39.70 °C. The optimal concentration of fluorosilicic acid is 26.68 %. In order to increase the concentration of fluorosilicic acid, three-stage cross-current extraction for dilute fluorosilicic acid solution was carried out at the optimizing extracting conditions, 17.43 wt% fluorosilicic acid solution can be concentrated up to 37.46 wt%. The extractant-benzyl alcohol can be recovered with vacuum distillation and recovery rate reached up to 98 %.

Effect of Fluoride in Alkali-Free Liquid Accelerator on Corrosion of Reinforced Shotcrete by Chloride Ion.

Shotcrete is a crucial component of tunnel engineering. To investigate the impact of fluoride-containing alkali-free liquid accelerators on the structural safety of shotcrete, this study prepared shotcrete using three different fluoride-based alkali-free liquid accelerators: magnesium fluosilicate, fluosilicic acid, and hydrofluoric acid. The corrosion of steel rebar within the shotcrete was examined and compared with that of shotcrete prepared using a fluoride-free alkali-free liquid accelerator. Analysis of the hydration products and pore structure of the shotcrete revealed that fluoride-containing accelerators inhibited the hydration of C3S, increased the content of harmful pores, reduced the pH value, and decreased the chloride ion binding capacity of the shotcrete. As a result, steel reinforcement within the fluoride-containing shotcrete was not effectively protected during the early stages. Detection of corrosion products indicated that shotcrete containing fluosilicic acid and hydrofluoric acid accelerators led to the rapid formation of loose corrosion products, primarily Fe2O3, thereby accelerating the corrosion rate of the steel reinforcement. Among the accelerators studied, hydrofluoric acid posed the most severe threat to the reinforcement, with the open circuit potential reaching -520.2 mV after 24 days of accelerated corrosion testing. Additionally, the mechanisms by which fluorides influence the corrosion of steel reinforcement in shotcrete were explored through the analysis of concrete hydration products and corrosion products on the steel rebar.

Effect of Acidulated Phosphate Fluoride Gel on Zirconia Intaglio Surface: An In-Vitro Study

Abstract Aim: To evaluate the micro-shear bond strength (µ-SBS) of resin-modified glass ionomer cement and to assess the chemical and topographical changes in the zirconia fitting surface induced by acidulated phosphate fluoride (APF) gel using scanning electron microscope (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy. Materials and Methods: Thirty-two samples were prepared from two zirconia materials, UPCERA HT White and BruxZir® Solid Zirconia, milled by a computer-aided design/computer-aided manufacturing system. From each zirconia sample, six plates were prepared for FTIR and SEM testing. Following sintering, the samples were divided into control and test groups for each material. The APF gel (1.23%) was applied to the intaglio surface of each test group. To measure the µ-SBS between the zirconia materials and luting cement, 20 rectangular samples of zirconia material were prepared. Ten samples were obtained from Upcera and ten from Bruxzir, with five assigned to the control and five to APF groups. Statistical Analysis: For the µ-SBS test, independent samples t test was conducted to determine the level of significance between the tested groups. Results: FTIR spectroscopy revealed new bands for Upcera and Bruxzir zirconia owing to ion exchange between the formed sodium phosphate and the zirconia surface and the formation of zirconium phosphate by an ester reaction. SEM assessment identified lines, scratches, or surface dissociation that appeared on the intaglio–zirconia surface after conditioning. The µ-SBS test, as indicated by the independent samples t test, showed a significant increase in bond strength of 1.266 and 1.566 MPa for Upcera and Bruxzir zirconia, respectively. Conclusion: This study offers new practical, cost-effective, and accurate tests to enhance the µ-SBS of luting cement to yttria-stabilized tetragonal zirconia polycrystal ceramics.

The Surface Deterioration of Prefabricated Zirconia Crowns on Exposure to Acidulated Phosphate Fluoride Gel: An In Vitro Study.

Introduction Zirconia is a widely used restorative material in dentistry due to its superior aesthetic and mechanical properties. The oral cavity is a complex ecosystem with various components, which affect the teeth, as well as artificial restorative materials. Various personal and professional interventions carried out can severely affect the properties of restorative materials, thus altering the longevity of the prosthesis; 1.23% acidulated phosphate fluoride (APF) gel is one such professionally applied topical fluoride agent used to prevent caries. The interaction of this APF gel with highly aesthetic restorative material such as zirconia crowns is unknown. Objective The objective of this study is the evaluation of the surface deterioration of prefabricated zirconia crowns on exposure to deionised water and 1.23% acidulated phosphate fluoride (APF) gel with field emission scanning electron microscope (FE-SEM) and mass loss analysis. Material and method Sixty prefabricated paediatric zirconia crowns were taken, 10 samples were immersed in deionised water, 40 samples were immersed in 1.23% APF gel and 10 samples were used ascontrol. Surface morphology and mass loss analysis were carried out at time intervals of four minutes, 24 hours, 48 hours and 72 hours using FE-SEM and digital weighing machine. Results No visual change was observed in the samples immersed in deionised water at the time interval of 72 hours. There was a marked visual change in samples immersed in 1.23% APF gel at the time interval of four minutes to 72 hours; this change involved a loss of gloss to the appearance of chalkiness. FE-SEM analysis for the control group and samples immersed in deionised water showed a smooth, continuous, undisrupted top layer, while samples immersed in 1.23% APF gel showed changes ranging from surface etching, to pinhole porosities, to crack formation and disruption of the surface depending upon the exposure time. Conclusions On the immersion of zirconia crowns in an aqueous acidic medium of 1.23% APF gel, the crowns showed flaws, imperfectionsand uneven superficial layers. It has been observed that surface grains are disrupted and micropores have been formed. This degraded superficial surface when undergoes cyclic mechanical loading can accelerate the ageing phenomenon of zirconia. Mechanical forces along with a dynamic electrochemical environment can degrade the material properties of zirconia.

EVALUATING THE EFFICACY OF 38% SDF VS 5% NAF VS APF GEL IN ARRESTING DENTAL CARIES AND REDUCING BACTERIAL ACTIVITY: AN IN-VIVO STUDY

Background: The study was formulated to compare the efficacy of 38% SDF as a caries arresting agent as well as antibacterial and antiplaque agent in vivo with 5% sodium fluoride varnish (NaF) and 1.23% acidulated phosphate fluoride (APF) gel. Study Design: Total of 74 children aged 6-9 years (boys = 34, girls = 40) who had active caries with dmfs/DMFS score equal to or more than 1 were included in the study for a period of 12 months. Children were divided into three different groups-Group 1: 38%SDF Group 2: 5% fluoride varnish and Group 3: 1.23% APF gel. Fluoride application was done at baseline, 6th month and 12th month. Saliva collection was done at baseline, after 72 hrs, 6th month and12thmonth.Tryptone-yeastcysteine-sucrose-bacitracin agar (TYCSB) was used inoculate salivary Streptococcus mutans and incubated at 37°C for 72 hrs.The colony characteristics were studied and number of colony forming units of Streptococcus mutans (CFU/ml) of saliva were counted using digital colony counter.All subjects were evaluated for caries arrest status and plaque score (Silness&amp;Loe index)at 6th and 12thmonthas well as Streptococcus mutans counts in saliva at 72 h, 6th and 12thmonth. Results: Significant reduction was found in caries arrest status plaque score as well as S. mutans counts in Group 1 as compared with Groups 2 and 3. Conclusion: In vivo application of SDF is effective in controlling progression of caries, decreases plaque score and S. mutans counts in saliva as compared to fluoride varnish and APF gel.

Preparation and properties of hexafluorosilicic acid series accelerators

Shotcrete technology has been widely used in tunnel engineering, road repair, underground engineering, and other scenarios due to its advantages of simple construction and fast progress. Liquid alkali-free accelerator is a necessary additive used in sprayed concrete, which can quickly set the concrete in a short period of time. Therefore, the development of alkali-free liquid accelerator is of great significance. The purpose of this research is to obtain low-cost and high-performance accelerator products and explore the influence of aluminum sulfate, hexafluorosilicic acid, and other raw materials on performance and stability. The main research results are as follows: (1) The accelerator product with low cost and high performance has been prepared. Its aluminum sulfate content is about 43%, hexafluorosilicic acid content is about 17%, sodium aluminate content is about 21%, the initial setting time is 1′ 15″, the final setting time is 2′ 05″, and the 1-day compressive strength is 9.5 MPa. (2) F ion plays a solubilizing role in the solution, and the appropriate ratio of aluminum sulfate and fluorine ion can greatly enhance the stability of accelerator solution. (3) Under the same cost condition, the influence of aluminum sulfate on the condensation performance is far greater than that of hexafluorosilicic acid and sodium metaaluminate. Subsequent research and development should focus on how to effectively increase the solubility of aluminum sulfate.

Bridging the gap to practicality: A green methanesulfonic acid system enhanced with synergistic additives for efficient and high-quality lead electro-refining

Green methanesulfonic acid (MSA) system offers a promising alternative to the traditional fluosilicic acid (H2SiF6) method for lead electro-refining. However, the MSA system has yet to produce efficient electro-refining process, high-quality cathodic lead and stable anodic dissolved layer concurrently, which is crucial for its practical application. Herein, we propose an MSA-based system — enhanced with Lugalvan NES (NES) and calcium lignosulfonate (CL) — for efficient and high-quality lead electro-refining. In both proof-of-concept and separate high-flux flow operations, we achieve a low energy consumption of 73.06 kWhe/t Pb and a high Faradaic efficiency of 99.11 %. Dense deposits with ultra-low grain sizes under 20 nm and high purities of over 99.99 %, and uniform dissolved layers with moderately adhesive anode mud are obtained. Theoretical simulations reveal the HOMO and LUMO energy levels of the additives and their adsorption energy on the Pb interface. Electrochemical analysis indicates a cathodic three-dimensional nucleation process and an anodic mechanism of uniform dissolution. A modular micro-kinetics model is developed to elucidate energy performance. These advances represent a significant step forward for lead electro-refining, achieving efficient operation and high-quality output while reducing energy use and surpassing the efficacy of the traditional method.

Professionally applied fluorides for preventing and arresting dental caries in low- and middle-income countries: Systematic review.

This systematic review aimed to review the safety and effectiveness of professionally applied fluorides for preventing and arresting dental caries in low- and middle-income countries (LMICs). Randomized controlled trials conducted in LMICs, in which professionally applied fluorides were compared with placebo/no treatment/health education only or usual care with a minimum one-year follow-up period, were included. Any topically applied fluoride agents such as sodium fluoride (NaF), acidulated phosphate fluoride, silver diamine fluoride (SDF), and nano silver fluoride (NSF) were included. Five databases (PubMed, Embase, Scopus, Web of Science, and Cochrane Library) were searched in May 2022. Meta-analysis was conducted using a random effect model. This review included 33 studies for qualitative synthesis, encompassing 16,375 children aged between 1.5 and 14 years. Nevertheless, the meta-analysis focused on only 17 studies, involving 4067 children. Fourteen papers assessed potential adverse events, none of which was reported as major adverse events. SDF and NSF were identified as effective in arresting caries on primary teeth (p < 0.05) compared with a placebo or no treatment. Fluoride varnish and gel were identified as effective in reducing new caries development on primary teeth (p < 0.05) but not on permanent teeth (p > 0.05). The certainty of the generated evidence obtained is low. The review provides valuable insights into the use of professionally applied fluorides in LMICs and contributes to recommendations for their use. However, the limited rigorous evidence suggests the need for further research to strengthen these findings and draw more robust conclusions.

Influence of fluoride characteristics on tooth surface protection in an erosive condition: A multifaceted characterization approach.

To evaluate the effect of fluoride consistency and composition to protect enamel and dentin against the dental erosion. Bovine enamel and dentin specimens were treated with artificial saliva, neutral fluoride gel (NFG), acidulated phosphate fluoride gel (AFG), neutral fluoride foam (NFF), and acidulated phosphate fluoride foam. The samples were subjected to cycling. Micro energy-dispersive X-ray fluorescence spectrometry, surface roughness (Ra), contact angle (CA), and scanning electron microscopy (SEM) were performed. Composition, CA and Ra data were analyzed by ANOVA and multiple comparison test (p < 0.05). The dentin protected had a significantly higher mineral content than in the control. Eroded unprotected enamel had higher Ra values than normal surfaces. Fluoride treatments increased the Ra in dentin samples. AFG increased the CA in enamel. Fluoride foams increased CA in dentin with reduced mineral loss. SEM analysis found a deposited layer on enamel treated with AFG and remnants of deposits on dentin treated with NFG and NFF. Regardless of the form of application, fluoride provided protection against erosion, however with different levels. Applying the adequate fluoride form is relevant since the formulations have different effects on both enamel and dentin.

Trace Silicon Determination in Biological Samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS): Insight into the Volatility of Silicon Species in Hydrofluoric Acid Digests for Optimal Sample Preparation and Introduction to ICP-MS

A method for the determination of trace levels of silicon from biological materials by inductively coupled plasma mass spectrometry (ICP-MS) has been developed. The volatility of water-soluble silicon species, hexafluorosilicic acid (H2SiF6), and sodium metasilicate (Na2SiO3) was investigated by evaporating respective solutions (50 µg/mL silicon) in HNO3), nitric acid + hydrochloric acid (HNO3 + HCl), and nitric acid + hydrochloric acid + hydrofluoric acid (HNO3 + HCl + HF) at 120 °C on a hot-block to near dryness. The loss of silicon from H2SiF6 solutions was substantial (&gt;99%) regardless of the digestion medium. Losses were also substantial (&gt;98%) for metasilicate solutions heated in HNO3 + HCl + HF, while no significant loss occurred in HNO3 or HNO3 + HCl. These results show that H2SiF6 species were highly volatile and potential losses could confound accuracy at trace level determinations by ICP-MS if digestates prepared in HF are heated to eliminate HF. Among the various matrices comprising major elements, sodium appeared to be effective in reducing silicon loss from H2SiF6 solutions. Excess sodium chloride (NaCl) matrix provided better stability, improving silicon recoveries by up to about 80% in evaporated HF digestates of soil and mine waste samples, but losses could not be fully prevented. To safely remove excess acids and circumvent the adverse effects of excess HF (e.g., risk of high Si background signals), a two-step digestion scheme was adopted for the preparation of biological samples containing trace silicon levels. A closed-vessel digestion was performed either in 4 mL of concentrated HNO3 and 1 mL of concentrated HCl or 4 mL of concentrated HNO3, 1 mL of concentrated HCl and 1 mL of concentrated HClO4 on a hot plate at 140 °C. Digestates were then evaporated to incipient dryness at 120 °C to remove the acids. A second closed-vessel digestion was carried out to dissolve silicates in 0.5 mL of concentrated HNO3 and 0.5 mL of concentrated HF at 130 °C. After digestion, digestates were diluted to 10 mL. The solution containing about 5% HNO3 and 5% HF was directly analyzed by ICP-MS equipped with an HF-inert sample introduction system. The limit of detection was about 110 µg/L for 28Si when using the Kinetic Energy Discrimination (KED) mode. The method was used to determine silicon in various plant and tissue certified reference materials. Data were acquired for 28Si using KED and standard (STD) modes, and 74Ge and 103Rh as internal standard elements. There was not any significant difference between the accuracy and precision of the results obtained with 74Ge and 103Rh within the same measurement mode. Precision, calculated as relative standard deviation for four replicate analyses, varied from 5.3 (tomato leaves) to 21% (peach leaves) for plant and from 2.2 (oyster tissue) to 33% (bovine liver) for tissue SRM/CRMs. Poor precision was attributed to material heterogeneity and the large particle size distribution. An analysis of lung tissue samples from those with occupational exposure to silica dust revealed that tissues possessed substantial levels of water-soluble silicates, but the most silicon was present in the particulate matter fraction.

Comparative Evaluation of Antibacterial Efficacy and Remineralization Potential of Acidulated Phosphate Fluoride Gel with Herbal Dental Gel Containing Zingiber officinale, Salvadora persica, and Cinnamomum zeylanicum: An In Vitro Study.

The aim of the study is to evaluate and compare the antibacterial efficacy and remineralization potential of acidulated phosphate fluoride (APF) gel with herbal dental gel containing Zingiber officinale, Salvadora persica, and Cinnamomum zeylanicum. Ethanolic extracts of Z. officinale, S. persica, and C. zeylanicum were prepared. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of these extracts were determined against Streptococcus mutans and Lactobacillus acidophilus using the resazurin method and agar plate streaking method, respectively. The herbal dental gel was formulated, and its cytotoxicity was evaluated using an 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The antibacterial susceptibility of APF gel and the herbal dental gel was assessed using the agar well diffusion method and time-kill assay. The remineralizing potential was evaluated using a stereomicroscope. Herbal dental gel showed better antibacterial efficacy as depicted by the zone of inhibition of 20 and 21 mm obtained against S. mutans and L. acidophilus, respectively, compared to 11.50 and 16.50 mm zone of inhibition obtained by APF gel. The herbal dental gel also showed better remineralization potential than APF gel after a time interval of 24 and 48 hours, as depicted with a statistically significant p-value of 0.0061 and 0.0219, respectively. In the cytotoxicity test, the fibroblasts showed 100% viability in the presence of both study groups. The results of our study concluded that herbal dental gel is safe and nontoxic, having anticariogenic potential due to its good antibacterial action and remineralization potential as compared to conventional APF gel. Kohli N, Hugar SM, Hallikerimath S, et al. Comparative Evaluation of Antibacterial Efficacy and Remineralization Potential of Acidulated Phosphate Fluoride Gel with Herbal Dental Gel Containing Zingiber officinale, Salvadora persica, and Cinnamomum zeylanicum: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(3):307-315.

Silver diamine fluoride – ‘The silver bullet’ in pediatric dentistry: An overview of past, present and prospects

Various fluoride-containing topical agents like sodium fluoride, acidulated phosphate fluoride, Silver fluoride, and Silver diamine fluoride (SDF) have also been developed to prevent and intercept dental caries, particularly in children. SDF in 38% concentration for preventing and arresting dental caries in children. SDF is applied exclusively to carious lesions, both cavitated and non-cavitated, forming a protective layer on demineralized enamel and dentin. This layer enhances resistance to acid dissolution and enzymatic digestion of collagen, promoting mineralization and the formation of hydroxyapatite and fluorapatite SDF is a versatile treatment option for caries management, offering benefits in various clinical scenarios, including difficult access cases, high caries risk patients, and prevention of pit and fissure caries. The present article discusses the utility of SDF in dentistry, with an emphasis on pediatric dentistry

Electrochemistry of Tin Deposition from Methanesulfonic Acid

The electrolytic refining of crude tin is generally carried out in the fluorosilicic acid (H2SiF6) system with the assistance of bone glue and β-naphthol. However, the high saturated vapor pressure and low stability of H2SiF6 present environmental concerns and do not align with sustainable development goals. In this paper, the electrochemical behavior of tin on a glassy carbon (GC) electrode was studied in a relatively green and environmentally friendly methanesulfonic acid (MSA) system. Bone glue, sodium lignosulfonate, and β-naphthol were used as additives to make the deposit morphology smooth and to ensure grain refinement. The electrochemical reduction process of Sn2+ in an MSA system is a quasi-reversible process controlled by diffusion. The apparent activation energy Ea = 14.189 kJ/mol for the ion diffusion of Sn2+ was further calculated. The results of chronoamperometry showed that the electrocrystallization of Sn2+ on the GC electrode gradually tended to three-dimensional instantaneous nucleation with the increase in applied potential. The morphology and phase of the deposits were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the deposits were uniform and dense pure tin. This work elucidates the electrochemical behavior of tin in a methanesulfonic acid system.

Production of anhydrous hydrogen fluoride from fluorosilicic acid: a review.

Anhydrous hydrogen fluoride (AHF), a critical raw material for industries such as aluminum, pharmaceuticals, and petroleum, has traditionally been sourced from fluorite-a non-renewable mineral. The unsustainable reliance on fluorite has catalyzed the search for alternative AHF production methods. A promising substitute is fluorosilicic acid (FSA), a byproduct of the phosphate fertilizer industry previously deemed waste. Transforming fluorosilicic acid into AHF not only yields a valuable resource but also addresses the environmental and economic challenges associated with waste management. The innovative practice of producing AHF from fluorosilicic acid signals a shift towards sustainable chemical production by capitalizing on waste, potentially diminishing reliance on fluorite and reducing the industry's environmental impact. This review thoroughly dissects the AHF synthesis process from fluorosilicic acid. Despite the acknowledged importance of fluorinated compounds in numerous industrial applications, research on their synthesis from fluorosilicic acid is limited and fragmented. This review seeks to amalgamate this scattered information by closely scrutinizing diverse industrial processing methods. Additionally, it explores the current and future landscape, economic feasibility, and strategies to navigate the obstacles inherent in synthesizing AHF from fluorosilicic acid. It also assesses the environmental impact of these methods, thereby contributing to the dialogue in this emerging field. The primary aim of this manuscript is to foster further research and promote the industrial uptake of this sustainable process. Highlighting the challenges and proposing potential improvements, the review supports the responsible reuse of waste and advocates for advancements in industrial practices.

Changes in the surface texture of pre-polymerized acrylic resin pediatric crowns following acidulated phosphate fluoride application.

This study aimed to investigate the effect of acidulated phosphate fluoride (APF) application on filler-free polymethyl methacrylate (PMMA)-based resin blocks for computer-aided design/computer-aided manufacturing (CAD-CAM), focusing on their use in pediatric crowns. Three types of PMMA-based blocks for CAD-CAM were evaluated, and a composite resin block for CAD-CAM was used as a control. Statistical analysis (p<0.05) of the data revealed that all PMMA-based blocks showed significantly higher gloss levels than the composite resin blocks. Two PMMA-based blocks also demonstrated significantly lower Ra and Sa values. SEM images showed no irregular changes in the surface properties of the PMMA-based blocks compared to those of the composite resin block. These results are significant in meeting the increasing demand for esthetic restorative treatments in pediatrics, where APF is commonly used for caries prevention. PMMA-based resin blocks for CAD-CAM are an effective alternative to prevent esthetic degradation from gloss reduction and plaque accumulation.

Remineralization effect of Er;Cr:YSGG laser irradiation with or without acidulated phosphate fluoride application on deciduous teeth enamel surface with induced white spot lesion. An in vitro study.

This study aims to assess the efficacy of Er; Cr: YSGG laser operating under sub-ablative settings for the remineralization of artificially induced white spot lesions on the enamel of primary teeth, both as a standalone treatment and in conjunction with 1.23% acidulated phosphate fluoride (APF) gel. Eighty primary posterior teeth were used to induce white spot lesions and were randomly divided into eight groups. The groups consisted of a negative control group (G1), a 0.75W laser irradiation group (G2), a 0.5W laser irradiation group (G3), a 0.25W laser irradiation group (G4), a positive control group with APF gel application (G5), and three groups that received laser irradiation of 0.75W, 0.5W, and 0.25W followed by APF gel application (G6, G7, and G8) respectively. Surface microhardness, SEM, and X-RD were used to evaluate the remineralization effect. There was a notable enhancement in surface microhardness post-treatment with the laser, APF gel, and their combination compared to the negative control group. The most pronounced increase in surface microhardness was observed in the combination treatment groups (G6, G7, and G8). SEM analysis showed increased surface roughness in groups treated with 0.75W and 0.5W laser power. X-RD assessments indicated an augmentation in crystal intensity within groups G6 and G8. The combined application of Er; Cr: YSGG laser under sub-ablative parameters and APF gel demonstrated a superior potential for remineralizing primary teeth enamel affected by white spot lesions. Key words:Er;Cr:YSGG laser. Sub-ablative irradiation. Remineralization. White spot lesion. APF gel. SEM. X-RD.

Influence of Er:YAG and ND:YAG laser irradiation and fluoride application on surface roughness and dentin surface wear after erosive challenge - An in vitro study.

To evaluate the effectiveness of Er:YAG and Nd:YAG laser on dentin hypersensitivity prevention, associated or not to acidulated phosphate fluoride (APF) after erosive challenge. 104 specimens were obtained from bovine dentine and divided into groups (n=13): G1: Er:YAG; G2: Er:YAG followed by application of APF; G3: application of APF followed by Er:YAG, simultaneously; G4: Nd:YAG; G5: Nd:YAG followed by application of APF; G6: application of APF followed by Nd:YAG, simultaneously; G7:application of APF; G8: untreated. The parameters for Er:YAG were:10s, distance of 4mm, water cooling flow of 2mL/min, 2Hz, 3.92J/cm2. For the Nd:YAG: 10s, distance of 1mm, without cooling, 10Hz, 70.7J/cm2. The erosive drink was a cola at 4°C, 3×/day for 1 minute, for 5 days. Roughness and wear analysis were done in confocal laser microscope. Data were statistically analyzed (α=0.05). As regards roughness, there was no statistically difference among the groups. The groups irradiated with Er:YAG had a volume loss lower. G6 showed higher values than the groups irradiated with Er:YAG and lower than the other groups. The other groups irradiated with Nd:YAG showed similar wear results to the control. The Er:YAG laser showed the lowest volume loss from wear analysis, suggesting the increased the acid resistance of dentin. Key words:Dentine sensitivity, Lasers, Sodium fluoride.

Dual regulation platform in C3N4/C3N5.4 molecular heterojunctions for simultaneous photocatalytic oxidative and adsorption of arsenic

The conversion of extremely hazardous As(III) to less toxic As(V) and subsequent adsorption onto the catalyst surface holds an advisable process for arsenic contaminants treatment. However, the conflictual mechanism of oxidation and adsorptive remains a huge challenge and unexplored for arsenic removal. In this work, a dual regulation platform of C3N4/C3N5.4 molecular heterojunction was well designed and constructed. The optimized C3N4/C3N5.4 exhibited excellent photocatalytic As(III) oxidation rate and As(V) adsorption efficiency under water, fluorosilicic acid and phosphoric acid solutions. The excellent performance benefits from the molecular heterojunctions induced internal electronic interactions and a local polarization, which contributes to the formation of built-in electric field (BEF) for enhancing exciton dissociation and charge transfer. Furthermore, the optimized electronic structure serves as the adsorption and oxidation site for simultaneously promoting charge interaction with arsenic elements, which greatly reinforces the absorption of arsenic. Our work may pave the way to optimize the electronic structure of bifunctional material for arsenic remediation.

Coordination Structure of Si(II) Ions in Binary Melts (LiF-KF, LiF-NaF, and NaF-KF) and Ternary Melt (LiF-NaF-KF).

The formation of Si(II) by the comproportionation reaction between electrodeposited silicon and Si(IV) ions [Si(IV) + Si0 ⇄ 2Si(II)] in fluoride melts has been discussed in many previous reports on the electrochemical processing of silicon. In this study, the coordination structure of Si(II) ions in LiF-KF, LiF-NaF, NaF-KF, and LiF-NaF-KF melts was investigated by high-temperature Raman spectroscopy and quantum chemical calculation based on density functional theory. The formation of Si(II) ions was induced by mixing metallic silicon powder as the source of Si0, with the melts containing hexafluoro silicate or silicon dioxide as the source of Si(IV) ions. The simulated vibrational modes of the Si(II) species and the experimental Raman bands showed good agreement. It was found that both Si(II) and Si(IV) species were detected in either fluoride melt, demonstrating that the proposed comproportionation reaction between Si0 and Si(IV) occurred. In addition, the interaction between Si(II) and F-, O2-, Li+, Na+, and K+ ions significantly changed depending on the composition of fluoride melts. The coordination structure of the Si(II) ions reported in this study will provide clues for controlling the electrodeposition process of silicon in fluoride melts.