Ionomer Type Research Articles

Determining the Amount of Microleakage of Two Types of Glass Ionomers in Class V Cavities Prepared By Conventional Method and Laser Er-YAG

Determining the Amount of Microleakage of Two Types of Glass Ionomers in Class V Cavities Prepared By Conventional Method and Laser Er-YAG

Catalyst Layers Prepared By Mixing Ionomer Dispersions with Different Equivalent Weights in Proton Exchange Membrane Fuel Cells

Recently, hydrogen-based energy conversion devices are stand out in the world for decarbonization. Fuel cells are common devices for hydrogen utilization, membrane electrode assembly (MEA) has the most important role in all components for fuel cell performance. MEA is consist of membrane and both side of catalyst layer, the catalyst layers were made of electrocatalyst and ionomer by evaporating all solvents in the catalyst inks. The ionomer increases the catalyst utilization by covering the electrocatalyst in the catalyst layer and increases the gas penetration by forming pore in the catalyst layer. Each ionomer dispersion has a different EW, and there are two types of side chains: Long side chain (LSC) and short side chain (SSC). Each ionomer has advantages and disadvantages. The structure of catalyst layer is formed differently according to type of ionomer, which could be make difference performance of catalyst layer. By mixing the ionomer, the advantages can be optimized to obtain a beneficial effect. Many properties of the components to consist of catalyst layers substantially influence their performance and durability due to the different interaction of electrocatalysts and ionomer. In this study, EW conducted an experiment to find out the difference in the properties of the catalyst layer using the same commercial ionomer and the ionomer made by mixing different dispersions. Three types of ionomers were used: i) long-side chain (LSC) ionomer, ii) short-side chain (SSC) and iii) Mixture of dispersions with different EW ionomer. Use an IEC automatic titrator to verify that ionomer dispersions made by mixing different ionomer dispersions have target EW values. Prepared catalyst layers prepared by the ionomers with different side chains were characterized by electrochemical evaluation such as I-V polarization, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and by physical and microscopic characterization such as porosimetry and water uptake. Acknowledgments This research was supported in part by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning (NRF-2019M3E6A1063677) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Elaboration and Characterization of β-TCP/ZrO2 Cements for Dental Applications

In the present study, four β-TCP/ZrO2 cement compositions were made, in which the zirconia was varied in different amounts at 0.25, 0.5, 0.75 and 1 wt%. The goals of this investigation were: (i) To analyze the effect of the mechanical properties of zirconia on the different samples of cement, (ii) To evaluate in vitro formation of hydroxyapatite in all cements at different times dipping in artificial saliva, and (iii) To analyze the interaction of glass-ionomer type I in all β-TCP/ZrO2 cement compositions. The results found were that the amount of zirconia added to the cement compositions did not significantly affect the mechanical properties’ values compared to the sample without zirconia. Nevertheless, ZrO2 helped to stabilize the demineralization of the types of cement in contact with artificial saliva at different times. On the other hand, the glass ionomer type I used to link the powder cement caused a change in the mechanical behavior, enhancing the plasticity in all the cement compositions. The in vitro test allowed an analysis of the cement samples dipping in artificial saliva, which showed a decrease of pH value from 7 to 3.8 at three days.

Effects of interactions between SPEEK or Nafion ionomers and bilirubin oxidase on O2 enzymatic reduction

Ionomers such as Nafion are used combined to redox enzymes in bioelectrocatalysis in order to prevent enzyme leakage and to enhance proton diffusion. In the search for an alternative to this costly and non-ecofriendly material, sulfonated poly(ether ether ketone) SPEEK, another ionomer free of perfluorinated functions can be envisioned. Here, we investigate the effect of ionomer type and concentration on enzymatic oxygen reduction by the Myrothecium verrucaria bilirubin oxidase (Mv BOD). We show that both SPEEK and Nafion ionomers reduce the catalytic activity of Mv BOD in enzymatic assays in solution as well as in electrochemical experiments once the enzyme is co-adsorbed with the ionomer. A pluridisciplinary approach associating microscopy, UV-Vis spectroscopy, dynamic light scattering, SDS gels and electrochemistry allows to point out a molecular interaction between the polymer particles and the enzyme governed by different principles depending SPEEK or Nafion is considered. The differences in hydrophilicity and conformation of SPEEK compared to Nafion account for a more severe effect on enzyme efficiency.

Ternary NiCoFe nanosheets for oxygen evolution in anion exchange membrane water electrolysis

Tuning nickel-based catalyst activity and understanding electrolyte and ionomer interaction for oxygen evolution reaction (OER) is crucial to improve anion exchange membrane (AEM) water electrolyzers. Herein, an investigation of multimetallic Ni0.6Co0.2Fe0.2 OER activity, coupled with in-situ Raman spectroscopy to track dynamic structure changes, was carried out and compared to other Ni catalysts. The effect of KOH concentration, KOH purity, ionomer type, and electrolyte with organic cations was evaluated. The Ni0.6Co0.2Fe0.2 catalyst achieved 10 mA/cm2 at 260 mV overpotential with stability over 50 h and 5000 cycles in 1 M KOH. In-situ Raman spectroscopy showed that Ni0.6Co0.2Fe0.2 activity originates from promoting Ni(OH)2/NiOOH transformation at low potentials compared to bi- and mono-metallic nickel-based catalysts. Fumion anion ionomer in the catalyst inks led to a lower OER activity than catalysts with inks containing Nafion ionomer. The OER activity of Ni0.6Co0.2Fe0.2 is adversely influenced in the presence of fumion anion ionomer and benzyltrimethylammonium hydroxide (BTMAOH) with possible phenyl oxidation under applied high anodic potentials. The alkaline AEM water electrolyzer circulating 1 M KOH electrolyte, with a Pt/C cathode and a Ni0.6Co0.2Fe0.2 anode, achieved 1.5 A/cm2 at 2 V.

Nickel‐based anodes in anion exchange membrane water electrolysis: a review

AbstractBACKGROUNDAnion exchange membrane water electrolysis (AEMWE) is a promising technology for efficiently producing low‐cost hydrogen (H2). Of the two half‐cell reactions in AEMWE, the oxygen evolution reaction (OER) is kinetically sluggish, requiring an electrocatalyst to promote the reaction. Nickel (Ni) is a promising non‐noble metal catalyst for OER due to its low cost, high stability, and activity in alkaline media. In an AEMWE, Ni particles form a catalytic layer bound together using an anion exchange ionomer (AEI), which also serves to provide hydroxide ion transport throughout the layer.RESULTSIn this review, reports of lab synthesized Ni particle‐based anode catalytic layers with AEIs, used specifically in AEMWE devices, are summarized from 2015 onwards to highlight the recent research and development of active Ni‐based AEMWE anodes. The synthesis and electrode fabrication method for the anodes is analyzed to offer a perspective on the feasibility of industrial scale AEMWE. As ionomeric binders are an important component of AEMWE anodes, the ionomer type and loading used with the Ni‐based particles is also summarized with a focus on how those parameters affect catalytic performance.CONCLUSIONThe literature analysis performed in this work demonstrates the potential of the AEMWE process and provides recommendations for future work on furthering the current understanding of the interactions between the various components of the system. Additionally, it is recommended that future research efforts be focused on further understanding how developed materials perform in a working AEMWE device. © 2022 Society of Chemical Industry (SCI).

Selective Borohydride Oxidation Reaction on Nickel Catalyst with Anion and Cation Exchange Ionomer for High‐Performance Direct Borohydride Fuel Cells

AbstractDirect borohydride fuel cells (DBFCs) operate with liquid H2O2 and a high‐energy‐density NaBH4 solution. A facile, direct synthesis method using a non‐noble nickel catalyst for the DBFC anode is shown. The complex anode reaction with an anion‐exchange ionomer (AEI) and a cation‐exchange ionomer (CEI) is evaluated in half‐cell and single‐cell configurations. The ionomer type produces high (AEI) or low local pH (CEI) at the active site of the catalyst in the single‐cell configuration, generating different catalytic reactions. The performance of the nickel catalyst is compared to that of a palladium catalyst. The selective catalytic activities for the borohydride oxidation reaction and hydrogen oxidation reaction are the key parameters for achieving good performance. Furthermore, fuel utilization and H2 evolution measurement in a single‐cell configuration provide more information on the complex anode reaction in the DBFC. The nickel catalyst with CEI on nickel foam (NiF@CEI‐Ni) shows the highest DBFC peak power density (0.59 W cm−2) with a non‐noble metal anode catalyst.

Probing Anion Exchange Membrane Fuel Cell Cathodes by Varying Electrocatalysts and Electrode Processing

To date, several high-performing anion exchange membrane fuel cells (AEMFCs) have been demonstrated, but most these studies have focused on Pt containing cathodes with high loadings. Here, we explore and compare the performance and perform electrochemical diagnostics on three leading AEMFC cathode electrocatalysts: Pt/C, Ag/C, and Fe–N–C with electrodes that have been processed with either powder or dispersion-based ionomers using perfluorinated anion exchange polymers. Pt/C had the highest performance but also showed a strong dependence on ionomer type, with powder ionomer exhibiting much higher performance. These results were consistent with the observations for Ag/C but did not hold for the Fe–N–C catalyst where almost no change was observed between powder and dispersion-based ionomers. This is the first-time the impact of powder and dispersion ionomer with different classes of cathode electrocatalysts on the fuel cell performance have been compared, and the results have strong implications for the ability to achieve high performance at low loadings and for better understanding catalyst-ionomer interactions within AEMFCs.

3D-printing self-healing composite polymer reinforced with carbon nanotubes

EMAA copolymer neutralized with sodium salt is a type of ionomer with self-healing abilities. This polymer has been used as raw material for the manufacturing of nanocomposite material by the addition of multiwall carbon nanotubes (MWCNTs). The optimization of the extrusion process, as well as the mixing and dispersion of the nano-reinforcement in the polymeric matrix during extrusion, deals with the manufacturing of a homogeneous reinforced filament. The obtained filaments were used afterwards as feeding materials of a 3D polymer printing machine and tensile test samples were manufactured. Mechanical properties of both unreinforced and reinforced samples were tested. The MWCNTs-reinforced samples exhibited higher mechanical properties without affecting its self-healing ability.

Distinguishing Adsorbed and Deposited Ionomers in the Catalyst Layer of Polymer Electrolyte Fuel Cells Using Contrast-Variation Small-Angle Neutron Scattering.

The ionomers distributed on carbon particles in the catalyst layer of polymer electrolyte fuel cells (PEFCs) govern electrical power via proton transport and oxygen permeation to active platinum. Thus, ionomer distribution is a key to PEFC performance. This distribution is characterized by ionomer adsorption and deposition onto carbon during the catalyst-ink coating process; however, the adsorbed and deposited ionomers cannot easily be distinguished in the catalyst layer. Therefore, we identified these two types of ionomers based on the positional correlation between the ionomer and carbon particles. The cross-correlation function for the catalyst layer was obtained by small-angle neutron scattering measurements with varying contrast. From fitting with a model for a fractal aggregate of polydisperse core–shell spheres, we determined the adsorbed-ionomer thickness on the carbon particle to be 51 Å and the deposited-ionomer amount for the total ionomer to be 50%. Our technique for ionomer differentiation can be used to optimally design PEFC catalyst layers.

Cytotoxic Effect of Addition of Different Concentrations of Nanohydroxyapatite to Resin Modified and Conventional Glass Ionomer Cements on L929 Murine Fibroblasts.

Objectives: In this study we assessed the cytotoxic effect of nanohydroxyapatite (NHA) incorporated into resin modified and conventional glass ionomer cements (RMGICs and CGICs) on L929 murine fibroblasts. Materials and Methods: In this in vitro study, 0wt%, 1wt%, 2wt%, 5wt%, 7wt% and 10wt% concentrations of NHA were added to Fuji II LC RMGIC and Fuji IX CGIC powders. Eighteen samples (5×3mm) were fabricated from each type of glass ionomer, in six experimental groups (n=3): CG0, CG1, CG2, CG5, CG7, CG10, RMG0, RMG1, RMG2, RMG5, RMG7, and RMG10. Samples were incubated for 72h. The overlaying solution was removed and added to L929 fibroblasts. The methyl thiazolyl tetrazolium bromide (MTT) assay was performed at 24, 48 and 72h. The wavelength was read by a spectrophotometer. Data were analyzed by ANOVA and Tukey’s test. Results: There was no significant difference in cytotoxicity of the two types of glass ionomers, with and without NHA, except for CG0 and RMG0 groups after 72h. RMG0 group was significantly more cytotoxic than the CG0 group (P<0.05). In CG groups during the first 24h, the cytotoxicity of CG5 and CG7 groups was significantly higher than that of CG1; while, there was no significant difference between the RMG groups. Cytotoxicity significantly decreased in all groups after 24h (P<0.05). Conclusion: Incorporation of NHA into Fuji II LC RMGIC and Fuji IX CGIC did not affect their biocompatibility and therefore its addition to these materials can provide favorable biological properties, especially considering its beneficial effects on the other properties of GICs.

Scanning Electron Microscopic Evaluation of Marginal Adaptation of Three Endodontic Sealers: An Ex-Vivo Study

Introduction: To avoid the entry of micro-organism or their products, sealer should completely adapt to the root canal wall so that no gaps will be present. AH plus is the most routinely used sealer. EndoRez is methacrylate resin-based self as well as light cured sealer. Endosequence BC RCS is the recently introduced bioceramic based sealer.&#x0D; Aim: To evaluate the marginal adaptation of Endosequence BS RCS, EndoRez and AH plus as a root canal sealer to root dentin under electron scanning microscope.&#x0D; Methods: Total 75 freshly extracted permanent maxillary central incisors with single canal were included in this study. All the teeth were decoronated till twelve millimeter and access cavity was prepared. All the teeth were prepared with rotary protaper till# F3 with intermediate copious irrigation with 3% sodium hypochlorite and 17%EDTA.Teeth were randomly divided into three groups according to sealers and were obturated- Endosequence BC RCS, Ah Plus and EndoRez. Access cavity was restored with glass ionomer type II in all the groups. After seven days, teeth were vertically sectioned and evaluated under electron scanning microscope for marginal adaptation.&#x0D; Results: Marginal gaps were present in all groups. Maximum number of gaps were present in Ah plus group. Endosequence BC RCS group showed least number of gaps.&#x0D; Discussion: Marginal adaptation of sealer depends upon the properties like flow, viscosity, presence or absence of smear layer etc. Better adaptation of Endosequence BC RCS to root dentin is due to formation of mineral infiltration zone which results in formation of calcific tags in dentine.&#x0D; Conclusion: Within the limitation of present study, newly introduced Endosequence BC RCS showed better marginal adaptability to root dentine. Further studies are required to evaluate and corelate these findings with other properties of these sealers.

MICROLEAKAGE EVALUATION OF THREE GLASS IONOMER CEMENTS USED IN CHILDREN: IN-VITRO STUDY

Purpose: To assess in-vitro the marginal adaptation of three types of glass ionomer cements in primary molars. Materials and Methods: The sample included thirty sound exfoliated or extracted primary molars for orthodontic purpose. The teeth were divided into 3 equal groups of 10 teeth each according to the type of the restorative material used. Group I were restored with ceramic reinforced glass ionomer, group II were restored with resin modified glass ionomer and group III were restored with conventional glass ionomer. After thermocycling, the teeth were immersed in 2% methylene blue solution for 24 hours, then they were sectioned buccolingually. The extent of dye penetration was detected using a stereomicroscope. Results: Ceramic reinforced glass ionomer showed the lowest mean microleakage value at both occlusal and cervical margins as compared to the other two groups with statistically significant difference. No statistically significant difference in the mean microleakage was recorded between the resin modified and conventional glass ionomers Conclusion: Ceramic reinforced glass ionomer revealed the highest sealing ability in class V primary molars when compared to the resin modified and conventional glass ionomer cements. Keywords: Microleakage, Glass ionomer cements, Class V, Primary molars.

Evaluating the effect of membrane-ionomer combinations and supporting electrolytes on the performance of cobalt nanoparticle anodes in anion exchange membrane electrolyzers

In low temperature polymer electrolyte membrane electrolyzers, component choices and membrane electrode assembly (MEA) fabrication have pivotal roles in determining cell performance. In this work, cobalt anodes were used in combination with different ionomers, membranes, and supporting electrolytes to delineate their effect on MEA performance in anion exchange membrane (AEM) based electrolyzers. Changes to the ionomer type suppress or enhance catalyst redox and were found to alter the resulting exchange current densities and Tafel slopes. Changes in membrane conductivity account for large differences in performance and overpotential losses among the different MEAs, with higher conductivity minimizing ohmic losses. Within supporting electrolytes, lower concentration results in lower conductivity and lower MEA performance; the performance, however, is higher in potassium hydroxide than bicarbonate. These experiments address the influence of individual components and their integration on cell-level performance, to help develop a pathway to an electrolyte free system while providing a foundation for studying electrode composition and component incorporation into MEAs.

An experimental study on the effect of four pediatric drug types on color stability in different tooth-colored restorative materials.

Background:One of the drawbacks of tooth-colored dental restorations is their discoloration over time. The present study aimed to determine the effect of four categories of pediatric medications, including analgesics, antibiotics, anticonvulsants, and multivitamins, on two types of tooth-colored dental materials, namely, composite resins and glass ionomer cements.Materials and Methods:In this in vitro study, a total of 40 specimens with disc shapes (with a diameter of 5 mm and thickness of 2 mm) were prepared from each material and immersed in eight different drugs for 2 min three times a day for 1 week. The values of the baseline color were calculated based on the CIE (International Commission on Illumination) L*a*b* system. After 7 days, ΔE values were calculated. Two-way analysis of variance was employed for statistical analysis. Statistical significance was defined at 0.05.Results:Statistical analysis showed that there were significant differences between ΔE and different restorative materials as well as ΔE and drug types (P < 0.001).Conclusion:According to the results of this in vitro study, all the four types of drugs caused the discoloration in all the restorative materials, and the color change values were affected by the type of used drug and restorative material.

Exploring Anion Exchange Membrane Fuel Cell (AEMFC) Performance with Different Classes of Cathode Electrocatalysts

AEMFCs as an alternative to acidic polymer electrolyte fuel cells have the potential to reduce cost and precious metal requirements of fuel cell systems.1 In the past decade, several highly conductive polymers have been developed and a number of these have demonstrated more than 1W∙cm-2 peak power density with hundreds of hours stability; however, most of these studies have focused on Pt containing cathodes with high loadings.2,3 While the promise of Pt and Pt group metal (PGM) free electrocatalysis has been a major selling point of AEMFCs, more work exploring the potential of PGM-free cathode electrocatalysis is needed. In this study we explore and compare the performance of three leading cathode electrocatalysts: Pt/C, Ag/C, and Fe-N-C. These electrocatalysts are tested in AEMFCs cathodes using both powder- and dispersion-based PF AEM Gen 2 ionomers.4 The ability to test the different catalyst and ionomer combinations leads to additional insight into performance and catalyst-ionomer interactions.The performance trends of the tested MEAs will be presented. Pt/C has been found to be slightly superior to the performance of the non-Pt electrocatalysts. The performance of both metal nanoparticle catalysts, Pt/C and Ag/C, exhibit strong differences in performance depending on whether or not a powder or dispersion-based ionomer is used, with the powder-based approach showing much higher performance. Unlike the metal electrocatalysts, Fe-N-C catalysts show almost no change of performance between powder and dispersion-based ionomers.These performance metrics are also reflected in high frequency resistance measurements (Figure 1) investigated as a function of relative humidity at 300 mA·cm- 2. This data clearly shows the expected trend of increasing HFR with decreasing humidification of reactant gasses. The Fe-N-C data shows the lowest HFR values and very small changes between powder and dispersion-based ionomers. Both, Pt/C and Ag/C show dramatic increases in HFR for the dispersion-based polymer compared to the powder-based ionomer. These large changes in HFR are unexpected and cannot be fully explained just by changes happening within the electrodes. They suggest that not only do the electrodes undergo variable electrochemical properties due to this processing, but water management within the cell is also impacted by the type of catalyst and ionomer used in processing the electrodes. These features and the impact they have on the performance of different AEMFC cathodes will be presented and discussed.

The Effect of pH Cycling on Surface Microhardness and Fluoride Release of Two Modified Nanoclay Glass Ionomer Restorations In Class V Cavities

Purpose: To assess the effect of pH cycling on surface microhardness and fluoride release of two modified nanoclay glass ionomer restorations (in vitro). Materials and Methods: A total of 180 permanent human caries free premolars were used. Class V were prepared on facial surfaces of the teeth. They were classified according to type of glass ionomer used for restoration of the cavities into three groups (60 teeth each); conventional glass ionomer medifill (A1), Dellite 43 modified glass ionomer (A2), and Dellite LVF modified glass ionomer (A3). Each group was moreover subdivided into three subgroups (20 teeth each) relative to the immersion solution used. The First subgroup remained in distilled Water (B1 control), the second subgroup was stored in artificial Saliva (B2) whereas the third subgroup was subjected to PH cycling (B3). Microhardness and fluoride release were measured after 7 and 30 days respectively. Results: There was a significant difference in the mean microhardness and fluoride release between the different materials after pH cycling (p≤0.001). PH cycling reduced the mean microhardness of the materials but induced the highest fluoride release. Conclusion: The proposed pH cycling model affected the microhardness of the tested materials while improved their fluoride release. Although the incorporation of montmorillonite into glass ionomer liquid improved the microhardness of the materials but it had yet, no effect on its fluoride release.

Electrocatalyst Performance at the Gas/Electrolyte Interface under High-Mass-Transport Conditions: Optimization of the "Floating Electrode" Method.

The thin-film rotating disk electrode (TF-RDE) is a well-developed, conventional ex situ electrochemical method that is limited by poor mass transport in the dissolved phase and hence can only measure the kinetic response for Pt-based catalysts in a narrow overpotential range. Thus, the applicability of TF-RDE results in assessing how catalysts perform in fuel cells has been questioned. To address this problem, we use the floating electrode (FE) technique, which can facilitate high-mass transport to a catalyst layer composed of an ultralow loading of catalyst (1-15 μgPt cmgeo-2) at the gas/electrolyte interface. In this paper, the aspects that have critical effects on the performance of the FE system are measured and parametrized. We find that, in order to obtain reproducible results with high performance, the following factors need to be taken into account: system cleanliness, break-in procedure, hydrophobic agent, ionomer type, and the measurements of catalyst surface area and loading. For some of these parameters, we examined a range of different approaches/materials and determined the optimum configuration. We find that the gas permeability of the hydrophobic agent is an important factor for improving the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) performance. We provide evidence that the suppression of the HOR and ORR introduced by the Nafion ionomers is more than a local mass transport barrier but that a mechanism involving the adsorption of the sulfonate on Pt also plays a significant role. The work provides intriguing insights into how to manufacture and optimize electrocatalyst systems that must function at the gas/electrolyte interface.

Influence of Ionomer Composition and Distribution on PEM Fuel Cell Performance of PGM-Free Catalyst

One of the effective ways to reduce the cost of polymer electrolyte membrane fuel cells (PEMFCs) is to reduce the amount of platinum-group metal (PGM) catalysts used for the oxygen reduction reaction (ORR). Recently, highly active platinum group metal-free (PGM-free) catalysts were developed and applied for the ORR reaction [1-3]. Significant developments have been made on the chemistry of PGM-free catalysts and their kinetic performance [4-6]. However, despite all the progress, some challenges remain before they are commercially viable. Mass-transport within the very thick catalyst layer (CL) displays a key challenge for further improvement of the fuel cell performance of PGM-free catalysts. Understanding of the structure of CL including the distribution of active sites and the ionomer inside the CL play an important role in the development of stable PGM-free cathodes capable of high power density. In the present work, our objective has been to demonstrate the effects of the ionomer content, solvents, and equivalent weight (EW) on electrode performance. The structure of the ionomer (i.e., short-side-chain vs long-side chain ionomer) as well as the effect of the relative humidity (RH) have been considered. To increase the proton conductivity of the cathode and improve the catalysts’ effectiveness across its thickness, it is important to optimize the ionomer type and its EW. In this work, we used the nanoscale X-ray computed tomography (nano-CT) method to characterize the morphology and transport properties of PGM-free cathodes. Our results show the sensitivity of the cathode’s performance to the hydrophilicity of the ionomer films. We found that electrodes with a lower ionomer EW have a tendency to retain more water than electrodes with a higher EW. Thus, at high current density conditions where significant water is being generated, the lower EW ionomers showed reduced performances due to electrode flooding when using the same processing and ionomer loading. In general, higher MEA performance at 100% RH was achieved using more hydrophobic ionomers (higher EW) with a greater proportion of hydrophobic fluoropolymer backbone or by using ink formulations that enhanced the hydrophobicity of a particular ionomer.AcknowledgmentThis material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office (FCTO) under Award Number DE-EE0008076.

Effect of different polishing techniques on surface roughness and bacterial adhesion of three glass ionomer-based restorative materials: In vitro study.

BackgroundAlthough many reports concluded that polishing of glass ionomers is crucial for smoother surface and limiting the adhesion of cariogenic bacteria, there is no specific surface treatment protocol recommended. A novel material in the same category was released recently claimed to have surface smoothness comparable to resin composite and bacterial adhesion less than other types of glass ionomers. In this study, different polishing systems were tested with three glass ionomers one of them is the novel material to find the most appropriate polishing protocol. Objectives: To evaluate and compare the surface roughness and bacterial adhesion to resin modified glass ionomer, bioactive ionic resin and conventional glass ionomer restorative materials after different polishing protocols in vitro. Material and MethodsThe materials tested includes resin modified glass ionomer, bioactive ionic resin, and conventional glass ionomer. The polishing protocols were divided into four groups: group 1 = (Mylar matrix strips, Control), group 2 = (one-step, PoGo), group 3 = (two-step, Prisma Gloss) and group 4 = (three-step, Sof-Lex). From each material, eleven cylindrical specimens were prepared for each group according to the manufacturers’ instructions. The surface roughness for all specimens was measured using atomic force microscope in tapping mode. the same specimens were subjected to bacterial adhesion testing after being coated with artificial saliva. Data were analyzed with two-way analysis of variance followed by Post hoc multiple comparisons. ResultsThe highest Ra and S. mutans adhesion values were recorded for all materials in two-step group. The lowest Ra and S. mutans adhesion values were seen in one-step and three step groups. ConclusionsOne-step polishing system was more effective and may be preferable for polishing of the three studied glass ionomer-based materials compared to two-step and three-step systems. Key words:Activa bioactive restorative, glass ionomer, surface roughness, bacterial adhesion, surface treatment.