Hexafluorosilicate Research Articles

Demineralization Inhibitory Effects of Highly Concentrated Fluoride Dentifrice and Fluoride Gels/Solutions on Sound Dentin and Artificial Dentin Caries Lesions in vitro

Objectives: The aim of this in vitro study was to compare the demineralization inhibitory effect of gels/solutions used in combination with either standard or highly fluoridated dentifrices on sound dentin as well as on artificial dentin caries-like lesions. Methods: Bovine dentin specimens (n = 240) with two different surfaces each (sound [ST] and artificial caries lesion [DT]) were prepared and randomly allocated to twelve groups. Weekly interventions during pH-cycling (28 days, 6 × 120 min demineralization/day) were: the application of gels/solutions containing amine fluoride/sodium fluoride (12,500 ppm F [ppm]; pH = 4.4; AmF); NaF (12,500 ppm; pH = 6.6; NaF1); NaF (12,500 ppm; pH = 6.3; NaF2); silver diamine fluoride (14,200 ppm; pH = 8.7; SDF); acidulated phosphate fluoride (12,500 ppm; pH = 3.8; APF), and no intervention (standard control; S). Furthermore, half of the specimens in each group were brushed (10 s; twice per day) with dentifrice slurries containing either 1,450 ppm (e.g., AmF₁₄₅₀) or 5,000 ppm (e.g., AmF₅₀₀₀). Differences in integrated mineral loss (ΔΔZ) and lesion depth (ΔLD) were calculated between values before and after pH-cycling using transversal microradiography. Results: After pH-cycling Ss showed significantly increased ΔZ_DT and LD_DT values, indicating further demineralization. In contrast, except for one, all groups including fluoride gels/solutions showed significantly decreased ΔZ_DT values. Additional use of most fluoride gels/solutions significantly enhanced mineral gain, mainly in the surface area; however, acidic gels/solutions seemed to have negative effects on lesion depths. Significance: Under the present pH-cycling conditions the highly fluoridated dentifrice significantly reduced caries progression and additional application of nearly all of the fluoride gels/solutions resulted in remineralization. However, there was no difference in the remineralizing capacity of fluoride gels/solutions when used in combination with either standard or highly fluoridated dentifrices.

Fluoride bioactive glass paste improves bond durability and remineralizes tooth structure prior to adhesive restoration

ObjectiveThe current study aimed at examining a fluoride containing bioactive glass (BiominF®) paste as a temporary filling material capable of remineralizing the demineralized enamel or dentin, and its ability to decrease a simulated dentinal fluids pressure on the resin/dentin interface, without affecting the shear bond strength of a universal bonding agent to enamel and dentin. Methods60 premolars were utilized for the acid resistance, trans-microradiography (TMR) and shear bond strength (SBS) experiments. Enamel and dentin discs were demineralized for 4 days to create a subsurface demineralized zone followed by applying BiominF® paste, 1.23% acidulated phosphate fluoride, or a temporary filling material for 24 h.30 extracted human non-carious third molars were utilized for the pulpal pressure experiment in which direct communication to the pulp chamber was created by cutting at a level approximately 1 mm below the cemento-enamel junction while the coronal enamel was ground to expose mid coronal dentin. The dentin surface was exposed to a simulated pulpal pressure. The dentin surfaces had BiominF® paste, an oxalate desensitizing agent, or temporary filling material followed by application of a universal adhesive system. ResultsOne way ANOVA showed that BiominF® paste remineralized effectively the demineralized enamel or dentin, did not affect the bond strength of the enamel and dentin surfaces to the tested adhesive system p < 0.05, and improved the acid resistance of the demineralized enamel and dentin against a secondary erosive challenge. Moreover, BiominF® paste decreased the nanoleakage expression in the dentin/adhesive interface exposed to a simulated pulpal pressure. SignificanceBiominF® paste may serve as a temporary filling material that may improve the longevity of adhesive restorations and help to conserve tooth structures by preserving the demineralized enamel and dentin form cutting during cavity preparation.

Fluorosilicic acid induces DNA damage and oxidative stress in bone marrow mesenchymal stem cells

Excess fluoride in water can produce changes in tooth enamel mineralization and lead to diseases such as dental or skeletal fluorosis. The present study aimed to assess the genotoxic effects, oxidative stress, and osteoblastic mineralization induced by fluorosilicic acid (FA) in murine bone marrow-derived mesenchymal stem cells (BM-MSCs). BM-MSCs were isolated from the femurs and tibias of rats and cultured under standard conditions. Cells exposure occurred for 3, 7, 14, and 21 days to different concentrations of FA (0.6–9.6 mg/L). Cytotoxicity was observed in 14 and 21 days of exposure for all concentrations of FA (cell proliferation below 60%), and for 3 and 7 days, in which the proliferation was above 80%. Alkaline comet assay results demonstrated significant increased damage at concentrations of 0.3–2.4 mg/L, and the micronucleus test showed increased rates for micronucleus (1.2–2.4 mg/L) and nuclear buds (NBUDs) (0.3–2.4 mg/L) (P < 0.05/Dunnett’s test). An alkaline comet assay modified by repair endonuclease (FPG) was used to detect oxidized nucleobases, which occurred at 0.6 mg/L. The oxidative stress was evaluated by lipid peroxidation (TBARS) and antioxidant activity (TAC). Only lipid peroxidation was increased at concentrations of 0.6 mg/L and 1.2 mg/L (P < 0.001/Tukey’s test). The osteogenesis process determined the level of extracellular matrix mineralization. The mean concentration of Alizarin red increased significantly in 14 days at the 0.6 mg/L concentration group (P < 0.05/Tukey’s test) compared to the control group, and a significant difference between the groups regarding the activity of alkaline phosphatase (ALP) was observed. Unlike other studies, our results indicated that FA in BM-MSCs at concentrations used in drinking water induced genotoxicity, oxidative stress, and acceleration of bone mineralization.

Effectiveness of remineralizing agents in the prevention and reversal of orthodontically induced white spot lesions: a systematic review and network meta-analysis.

To compare the effectiveness of remineralizing agents in the prevention and reversal of white spot lesions (WSLs), which occur during fixed orthodontic treatment, through a systematic review and network meta-analysis. We reviewed controlled randomized clinical trial (RCT) data querying nine databases combined with a manual search (last search date: March 10, 2020). Of 2273 identified studies, 36 RCTs were finally included. After study selection and data extraction, pair-wise and network meta-analyses were performed to analyze the effectiveness of remineralizing agents in the prevention and reversal of WSLs in the short term (≤ 3months) and long term (> 3months). The risk of bias was assessed based on the Cochrane guidelines. Statistical heterogeneity, inconsistencies, and cumulative ranking were also evaluated. In terms of WSL prevention, sodium fluoride (NaF) varnish had the highest cumulative ranking for the short-term decalcification index (99.3%); acidulated phosphate fluoride (APF) foam ranked first for long-term incidence (96.9%), followed by difluorosilane (Dfs) varnish and high-concentration fluoride toothpaste (HFT) (79.4% and 77.4%, respectively). In the reversal of WSLs, no significant difference was found among different agents or their combinations for the two available outcomes (short-term integrated fluorescence loss and short-term percentage of fluorescence loss). In the prevention of WSLs, APF foam showed the best remineralizing effectiveness in the long term (after debonding), followed by Dfs varnish and HFT. It is unclear whether remineralizing agents can effectively reverse WSLs based on the existing evidence. APF foam may be recommended as a remineralizing agent for preventing orthodontically induced WSLs. CRD42019116852.

Microshear Bond Strength of Composite Resin to Enamel Treated With Titanium Tetrafluoride and the Carbon Dioxide Laser (10.6 µm): An In Vitro Study.

Introduction: The present study aims to assess the microshear bond strength (µSBS) of composite to enamel treated with titanium tetrafluoride (TiF4 ) and CO2 laser irradiation. Methods: Fifteen human molars were sectioned and their enamel surfaces were abraded. The sections were randomly assigned to 5 groups (n=15): (CO); control group, (AP); treated with 1.23% acidulated phosphate fluoride (APF) for 4 minutes, (Ti); 4% TiF4 for 1 minute, (L+AP); CO2 laser irradiation (10.6 µm wavelength, 1 W peak power, 10 ms pulse duration, 500 ms repetition time, 0.2 mm beam spot size at the tissue level, 2 cm distance of handpiece tip to tissue surface (DSE, South Cores) followed by 1.23% APF, and (L+ Ti); 10.6μm CO2 laser irradiation followed by 4% TiF4 for one minute. Using Tygon tubes, Z250 (3M/ESPE) composite was bonded to the surface of the samples. The µSBS of composite to enamel was measured using a microtensile testing machine after 500 thermal cycles. The data were analyzed by one-way ANOVA and the Tukey HSD test (P <0.05). Results: The mean µSBS was 20.66, 20.21, 13.44, 23.01, and 10.16 MPa in CO, AP, Ti, L+AP, and L+Ti groups respectively. Significant differences were observed between CO and Ti (P =0.026) and also CO and L+ Ti (P <0.0001). Conclusion: The application of TiF4 per se and after CO2 laser irradiation on enamel decreased the µSBS of composite to enamel; on the other hand, APF alone and after laser irradiation did not have any adverse effect on the µSBS of composite to enamel.

Study of Demineralized Dental Enamel Treated with Different Fluorinated Compounds by Raman Spectroscopy.

Background: Current diagnostic methods for enamel caries detection are unable to detect caries lesions (incipient caries lesion) at a very early stage.Objective: This study aims to determine the remineralizing effect of three fluorinated compounds on demineralized subsurface tooth enamel using Raman spectroscopy characterization.Material and Methods: In this experimental study, sixty impacted 3rd molars, with intact anatomical crowns recently extracted and without structural defects, were sectioned longitudinally in a mesio-distal direction using a diamond disc, obtaining two working surfaces (buccal and lingual). The 120 working surfaces obtained were immersed for 96 h in a demineralization solution at 37°C in order to demineralize the enamel surface. All samples were randomly divided into three groups (n=30 each) and their surfaces were treated with silver diamine fluoride (SDF), Difluoride silane (DSF), and acidulated phosphate fluoride (APF), and with no treatment undertaken in the control group (CG). The samples were immersed in alternating solutions for demineralization and remineralization at pH 4.4 and pH 7.0, respectively. The results were analyzed with Principal Component Analysis (PCA) in order to determine the variance.Results: The most important difference (91.7%) is observed in APF group between PCA1 respect to PCA2, followed by DSF (91.5%) and SDF (76.3%) respectively. Therefore, a greater remineralization in the dental enamel can be observed by the three experimental groups. Conclusion: The APF and DSF have the effect of recovering the mineralization of dental enamel, except for the SDF. Functional groups OH- and PO43- were identified in all subsurface.

Evaluation of shear bond strength of brackets bonded to fluoride-treated enamel surfaces: An in vitro study

Enamel decalcification is a well-recognized problem associated with orthodontic treatment with fixed multibanded appliances. Several methods have been proposed to minimize the incidence and severity of white spot decalcification around brackets. The present study is concerned with the evaluation of the effect of different topical fluoride gels, applied before and after etching on the shear bond strength of directly bonded orthodontic brackets. The sample consisted of (70) human upper first premolars distributed to (7) groups: group A served as a control; groups B1, C1, andDl received, for (4) minutes prior to etching, a topical application of neutral sodium fluoride gel (1.1%), sodium monofluorophosphate gel (1.2%), and acidulated phosphate fluoride gel (1.23%) respectively. Groups B2, C2, and D2, on the other hand, were treated, for (4) minutes after etching, with topical application of neutral sodium fluoride gel (1.1%), sodium monofluorophosphate fluoride gel (1.2%), and acidulated phosphate fluoride gel (1.23%) respectively. The brackets were loaded under shear to failure using Universal Compression Machine Apparatus. The shear strengths were recorded in Megapascals. The results of the present study showed that the application of fluoride gels for (4) minutes before and after etching did not alter the shear bond strengths of directly bonded orthodontic brackets, when compared with the control group, for all groups except for group D2 in which the topical application of acidulated phosphate fluoride gel for (4) minutes after etching has resulted in a significant reduction in shear bond strength and severity of white spot decalcification around brackets.

Caries-preventive effect of topical APF gel with three different frequencies of application in 9-11 years old school children in Ninevah

This is the first study carried out in Iraq that aimed at evaluating the effect on dental caries of Acidulated Phosphate Fluoride (APF) gel applied topically with different frequencies (once per year vs. twice per year vs. four times a year). A sample of (235) school children [116 (49.36%) males and 119 (50.64%) females) initially in the fourth grade (aged 9-11 years) were collected from (4) primary schools in Mosul city Centre. The children were allocated randomly to (3) experimental groups and one control group. The first group received (0.49%) APF gel four times a year for (4) minutes. The second group received (0.4%) APF gel once per year for (4) minutes; whereas the third group received (0.4%) APF gel twice per year for (4) minutes. Two examinations were done using DMFT and DMIFS indices: one before fluoride application and the other after one year. The results showed a reduction in dental caries (with respect to DMFT index, and in comparison with the control group) of (112.8%) for the first group,(35.9%) for the second group, and (80.4%) regarding the third group. With respect to DMFS index, and in comparison with the control group, the reduction in dental caries was (97.3%),(32.8%), and (72.6%), respectively. The best benefit from using topically applied APF gel was, therefore, achieved from applying (0.4%) gel four times a year for (4) minutes.

Morphological, Structural, and Optical Properties of Silicon Nanostructures Formed in a Solution Containing Hydrogen Hexafluorosilicate H2(SiF6)

Photoluminescent boron-doped (100)-oriented porous silicon fabricated on a p-type silicon substrate by electrochemical etching in a solution containing fluorosilicic acid and ethanol is studied. The morphological, structural, and optical properties of silicon nanostructures obtained in solutions containing H2(SiF6) and ethanol are analyzed in comparison with the corresponding characteristics of samples formed in solutions of HF and ethanol. The morphological, structural, and optical properties were studied using scanning probe microscopy and spectrophotometry. It is shown that the porous silicon samples formed in solutions containing H2(SiF6) and ethanol have better optical properties, in particular, they exhibit more intense photoluminescence than the samples obtained in HF–ethanol solutions.

Hexafluorosilicic Acid (FSA): from Hazardous Waste to Precious Resource in Obtaining High Value-Added Mesostructured Silica

In this work, industrial waste hexafluorosilicic acid (H2SiF6 or FSA) has been proven to be a low-cost alternative to silicate esters for the synthesis of high-quality MCM-41 (high surface area, hi...

Does fluoride reduce the mineral loss of gamma‐irradiated primary teeth?—In vitro study

AbstractBackgroundGamma radiation turns the primary enamel more susceptible to demineralization.AimTo investigate if the fluoride dentifrice combined with acidulated phosphate fluoride gel (APF‐gel) inhibits the progression of mineral loss of gamma‐irradiated primary enamel.DesignSpecimens of demineralized primary enamel were randomized into eight groups (n = 13): Non‐irradiated + Non‐fluoride dentifrice (G1); Non‐irradiated + Fluoridated dentifrice (G2); Non‐irradiated + APF‐gel + Non‐fluoridated dentifrice (G3); Non‐irradiated + APF‐gel + Fluoridated dentifrice (G4); Irradiated + Non‐fluoridated dentifrice (G5); Irradiated + Fluoridated dentifrice (G6); Irradiated + APF‐gel + Non‐fluoridated dentifrice (G7); and Irradiated + APF‐gel + Fluoridated dentifrice (G8). Specimens of irradiated groups were submitted to 3060 cGy radiation dose. After APF‐gel treatment, specimens were submitted to a pH cycling, with the respective dentifrice exposure, twice daily. The microhardness and polarized light microscopy analyses were performed to quantitatively and qualitatively assess the enamel mineral loss, respectively. Quantitative data of mineral loss were compared using the two‐way ANOVA, followed by the Tukey test.ResultsFluoride dentifrice alone, APF‐gel application alone, and their combination were not effective in inhibiting mineral loss of irradiated primary enamel.ConclusionThe combination of fluoride dentifrice and APF‐gel was not effective in inhibiting the progression of mineral loss of gamma‐irradiated primary teeth.

DIFFERENCES IN SURFACE HARDNESS OF BOVINE ENAMEL AFTER EXPOSURE OF THEOBROMINE, ALKALOID COCOA POD EXTRACT AND ACIDULATED PHOSPHATE FLUORIDE

Background: Acid diet could process demineralization on enamel surface. Process remineralization needed to prevent caries occurrence. The excessive fluorine usage could induce adverse side effects, therefore the development of natural resources such as theobromine and alkaloid cocoa extract as a remineralization is needed. Purpose: To discover the differences of bovine teeth enamel surface hardness after exposure to theobromine, alkaloid cocoa pod extract and acidulated phosphate fluoride. Method: Twenty-eight tooth crowns of bovine insisivus cut into the shape of the square then planted on the resin mold round shape and divided into four groups. The control group without treatment, the group I was exposed APF, the group II was exposed 1000 mg/L alkaloid cocoa pod extract, group III was exposed 200 mg/L Theobromine 200 mg/L. Surface hardness measured using Wolpert Wilson Vickers Microhardness Tool. Results: The group of theobromine produces the highest enamel surface hardness. The enamel surface hardness in alkaloid group of cocoa pod extract was higher compared to the APF group and the control group. Conclusion: The hardness surface of bovine tooth enamel after exposure to theobromine and alkaloid cocoa pod extract is harder than exposure to acidulated phosphate fluoride.

Time-dependent effects after enamel fluoride application on an acid etching system in orthodontic bracket bonding.

This study investigated the effectiveness of acid etching and bond strength in an orthodontic bonding system in accordance with various time periods after 1.23% acidulated phosphate fluoride (APF) gel applications. APF gel was applied on the enamel surface of bovine teeth, which were assigned to group F0. The tooth specimens were then immersed in distilled water for 1 (F1), 7 (F7), 14 (F14), 21 (F21) and 28 (F28) days. A group without fluoride pretreatment was a control group. All groups were etched with 35% phosphoric acid and evaluated using a surface hardness tester and scanning electron microscope (SEM). A shear bond strength (SBS) test was performed using a universal testing machine, and the bond failure modes were also examined. After the 1.23% APF gel treatment, the hardness of the acid-etched enamel surface decreased as the immersion period increased. SEM images of the test groups showed etched patterns similar to control group as the immersion period increased. The SBS increased with increasing immersion period, whereas group F21 was not significantly different from the control group. Relatively high adhesive remnant index scores were identified as the ageing period increased. The present study indicated that in order to obtain suitable bond strength, it is recommended to use an acid etching-based bonding system for the fixation of orthodontic appliances on the enamel surface 21days after the use of APF gel. Fluoride pre-treatment interferes with the acid etching effects on enamel, causing a reduction in the bond strength with orthodontic brackets.

Synthesis of mesoporous silica nanoparticles from waste hexafluorosilicic acid of fertilizer industry

Hexafluorosilicic acid (H2SiF6) is one of the most harmful by-products of the agricultural industry and because of the enormous scale of the industry, disposal of the acid on such a large scale is a huge concern. H2SiF6 has adverse effects on both human physiology and the environment. Moreover, the acid is also corrosive to many common materials such as glass and metals. The method outlined in this paper aims to dispose of this corrosive and harmful by-product of the agricultural industry while also producing a very valuable product in the form of mesoporous silica nanoparticles (MSN's). Previous efforts to produce MSN's in bulk fell short as they were not sustainable, cyclic and/or required complex equipment. The current method aims at ammoniation of H2SiF6 with certain controllable parameters in order to obtain pure MSN's. The parameters used were rate of addition of ammonia and the rate of agitation post ammoniation. EDX and XRD confirmed that the synthesized particles were MSN's. Dynamic light scattering (DLS) of the various samples showed a good size distribution and confirmed that, by changing process parameters, we were able to control the particle size. BET confirmed a high surface area and an average pore size was also obtained. MSN's can be used for a variety of purposes, including formation of aerogels, bio-sensing, and particularly in targeted drug delivery where the properties of MSN's make it a very viable candidate. The process presented in this paper can be extended to make it a cyclic and sustainable process capable of producing two nanomaterials.

Fluoride Release and Recharge Properties of Several Fluoride-Containing Restorative Materials

The aim of the study is to compare the fluoride release and recharge properties of glass ionomer cements and ‘alkasite’.&lt;br/&gt;Specimens of two glass ionomer cements (Fuji Ⅸ GP and Riva Self Cure), ‘alkasite’ restorative material (Cention N) and composite resin (Filtek&lt;sup&gt;TM&lt;/sup&gt; Z350XT) were prepared. The fluoride release of each specimen was measured for 28 days. Thereafter, 1.23% acidulated phosphate fluoride (APF) gel was applied to experimental groups. No treatment was performed on control groups. The fluoride release was measured for additional 7 days to evaluate the fluoride recharge properties of each materials.&lt;br/&gt;The fluoride release was highest in Riva Self Cure, followed by Fuji Ⅸ GP, Cention N (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). Fluoride release of Cention N was measured to be approximately 49% of Fuji Ⅸ GP’s. After the application of 1.23% APF gel, increases in fluoride release were observed in Riva Self Cure, Fuji Ⅸ GP and Cention N (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). Fluoride recharge was observed in Cention N as well as in glass ionomer cements. Further studies are required to evaluate the anti-cariogenic properties of Cention N at clinical conditions.

Bis(3-hydroxymethylpyridynium) hexafluorosilicate monohydrate as a new potential anticaries agent: Synthesis, crystal structure and pharmacological properties

The hexafluorosilicate with the composition (LH)2SiF6·H2O (I, L = 3-hydroxymethylpyridine) was obtained by reaction of 45 % hexafluorosilicic acid with a methanol solution of L (H2SiF6 : L = 3: 1). The crystal structure I is stabilized by OH···O, NH···F, and OH···F H-bonds, and CH···F contacts. The symmetry of the SiF62– anion is close to D4h. The solubility of I in water was 1.63 mol. % and the degree of hydrolysis of the salt in a 1·10–4 M aqueous solution was 91.6 %. A PASS-analysis of the spectrum of biological activity L highlighted a low probability of toxic effects.

Silicon determination by microwave-induced plasma optical emission spectrometry: Considerations and strategies for the use of tetrafluorboric acid and sodium hydroxide in sample preparation procedures

The use of tetrafluoroboric acid and sodium hydroxide were investigated for the total decomposition of plant tissues and fertilizers for Si determination by microwave-induced plasma optical emission spectrometry (MIP OES). The accuracy was estimated by comparing the results of the proposed method with those of energy dispersive X-ray fluorescence (ED-XRF). The optimized HBF4 volume required to decompose 100 mg of sample was estimated to be 0.2 mL (48% w v−1). The Si recovery obtained was 99%, and the limit of detection was 0.03 g kg−1. Concerning the reactions and the possible products formed, after digestion 70% of the Si was found as fluorosilicic acid. Besides this, hydrofluoric acid was formed. High dilution factors, the addition of excess boric acid, or the use of a sample introduction system manufactured from inert components can be adopted to avoid damage to the MIP OES components and contamination of the analytical blank. The introduction of air in the N2 plasma was assessed to reduce the matrix effect noted due to high sodium concentration in the alkaline digestion, and improved accuracy was achieved. The Si recoveries obtained by applying this method varied from 100 to 102%, and the limit of detection was 0.4 g kg−1.

Evaluation of diode laser along with 1.23% acidulated phosphate fluoride gel on dentinal tubule occlusion: An in vitro study.

Context:Several studies have recommended the use of lasers in treatment of dentinal hypersensitivity. These materials have been used alone or in combination with an active desensitizing agent.Aims:The present study aimed to evaluate the use of 1.23% acidulated phosphate fluoride (APF) gel and 810 nm diode laser when used alone and when used together on exposed dentinal tubules.Settings and Design:Sixty-one extracted teeth were sectioned with a diamond saw and dentin slices were prepared. They were then treated with 37% orthophosphoric acid to remove the smear layer.Materials and Methods:One of the 61 sections was left as an untreated control, whereas the remaining sixty sections were divided into three groups of twenty sections each. The first set of sections (Group 1) was treated with laser alone, whereas the second set (Group 2) was treated with APF alone. A third set of sections (Group 3) was treated with a combination of laser and APF. The sectioned teeth were then evaluated using field emission scanning electron microscopy, and the percentage of dentinal tubule occlusion was observed.Statistical Analysis:The Shapiro–Wilk normality test was performed to check for the normal distribution of data, whereas the Kruskal–Wallis test was used to compare the mean percentage of dentinal tubule occlusion between the three groups. The Chi-square test was used to compare the number of images with complete tubular occlusion between the three groups.Results:A total of 96 images were processed from the sixty sectioned samples. It was seen that the sections in Group 3 showed the highest percentage of dentinal tubule occlusion. Group 3 also showed the highest number of samples with complete dentinal tubule occlusion. Significantly lesser levels of dentinal tubule occlusion were seen in Groups 1 and 2.Conclusions:Diode lasers were effective in occluding dentinal tubules. The addition of 1.23% APF significantly increased the efficacy and thoroughness of dentinal tubule occlusion. Significantly lesser levels of dentinal tubule occlusion were seen in the sections treated with laser alone and APF alone.

The kinetics of Indonesian galena concentrate leaching in fluorosilicic acid and hydrogen peroxide as its oxidants

Lead smelting is known as a lead extraction technique which has negative impact to environment because it produces emissions of dust, SO 2 gas and lead. The leaching is conducted to reduce the smelting’s weaknesses by extracting the lead without damaging the environment. This technique, often called hydrometallurgical lead extraction, uses liquid media to extract the lead and separate it from the elemental sulphur (S 0 ) by filtration. Particle size, slurry density (solid percentage) and acid concentration affect the dissolution of Indonesian galena concentrate with fluorosilicic acid and hydrogen peroxide as oxidants. By means of these reagents, it is expected that the Pb extraction process from galena concentrate resulted from flotation of sulfide ore can be carried out at low temperatures and lead recovery can be accomplished from the leach solution by electrowining. Studying galena leaching kinetics is required to perform galena leaching with high Pb extraction percentages. Two kinetics models are commonly used to study leaching kinetics, namely shrinking core model (SCM) and shrinking particle model (SPM). These models are used to determine the mechanism which controls leach reaction and reaction rate constant or diffusion constant of the reacting species. Total plotting of sulfide fraction dissolves with time adjusted to the existing mathematical model, and fitting the curve from the dummy model to the experimental data, are two techniques that are utilized to obtain the best kinetics model which important in controlling the leaching reaction rate. Applying the Arrhenius equation, the relation of the reaction rate constant or the diffusion constant and the temperature is determined to calculate the leaching activation energy. The result from kinetics analysis showed that the leaching of Indonesian galena concentrate in fluorosilicic acid with hydrogen peroxide as oxidants followed the shrinking core model with diffusion through porous solid product layer as the reaction controller with activation energy of 45.81 kJ/mol or 10.91 kcal/mol.

Comparative Evaluation of Chitosan Nanoparticles, Silver Diamine Fluoride and Acidulated Phosphate Fluoride Gel on Microhardness of Artificial Carious Lesions Created on Extracted Teeth

Introduction: Dental caries is a multifactorial microbial infectious disease characterised by demineralisation of the inorganic and destruction of the organic substance of the tooth. To combat dental caries the application of nanotechnology includes the inhibition of formation of biofilm and regulating the balance of demineralisation-remineralisation processes, ensuring a possible mechanism that can aid in prevention and treatment of tooth decay. Initial caries progression may be prevented by suitable surface treatment, by applying surface remineralising agents. Aim: To evaluate and compare the efficacy of remineralising potential of Acidulated Phosphate Fluoride (APF) gel, Chitosan nanoparticles and Silver Diamine Fluoride (SDF) on microhardness of artificial carious lesions created on extracted teeth. Materials and Methods: This was an in-vitro experimental study associated with Krishna Institute of Medical Sciences, Karad conducted during a period of two months (October and November 2019) at Mechanical Department of Rajarambapu Institute of Technology, Islampur, Maharashtra. The total sample size was 30 premolar teeth. In this in-vitro study, test materials Chitosan nanoparticles, Silver Diamine Fluoride (SDF) and Acidulated Phosphate Fluoride gel (APF) varnishes were manipulated and applied (10 in each group) in accordance with manufacturer’s instructions. Artificial carious lesions were created in the enamel. This was achieved by suspending the teeth in an artificial caries system. Baseline microhardness was then recorded using Vickers Hardness Test and varnish application was carried out. Samples were then placed separately in a demineralisation solution for three hours. Thereafter, samples were placed in a remineralisation solution. Any change in microhardness was determined by evaluating the Vickers Hardness Test at the end of 28 days. The data was then recorded, tabulated and statistically analysed using Kruskal-Wallis Test and Wilcoxon Signed Test for inter and intra groups comparisons to find out if there was a significant difference. Results: All the three varnishes i.e., Chitosan nanoparticle, silver diamine fluoride and APF gel in intragroup comparison after intervention showed significant differences with Chitosan nanoparticle showing the highest increase in microhardness with p-value of 0.001 followed by SDF with p-value of 0.005 and APF gel with p-value of 0.005. Conclusion: All the three varnishes increased enamel microhardness significantly. Chitosan nanoparticle showed highest increase in remineralisation followed by SDF and APF gel. Hence, varnish application is a good method in remineralising the tooth.