Diffusion Of Hydroxyl Ions Research Articles

Simulation of chloride diffusion tests in cement paste and mortar made with CEM II and CEM VI cements

We developed a simplified coupled model to simulate the chloride ingress of cement paste and mortar fabricated with CEM II/C-M (S-LL) and CEM VI (S-V) cements. Diffusion of chloride, calcium, sodium, potassium, sulphate and hydroxyl ions is considered, resulting in a set of coupled mass balance equations. Source and sink terms are introduced to represent the dissolution/precipitation processes due to leaching, and interactions between free chloride and hydrated phases are considered through binding isotherm curves. Electrodiffusion phenomenon is introduced through a modified Poisson equation to enforce local electroneutrality. The model is applied to simulate bulk diffusion tests with exposure solutions containing NaCl, and NaCl + KOH to reduce leaching. The main features observed experimentally are correctly reproduced: a higher chloride content is predicted for the materials made with CEM II binder, and a much clearer peaking behavior near the exposed surface is predicted in the case of NaCl exposure.

Evolution and Prediction of Tensile Properties for Ductile Hybrid FRP Bars in a Simulated Concrete Environment

Hybrid fiber–reinforced polymer (HFRP) bars possessing high tensile ductility and excellent corrosion resistance are an attractive alternative to steel bars. However, the effect of long-term embedment of HFRP bars in concrete on the tensile ductility of bars must be investigated. This study exposes a series of ductile carbon/glass-HFRP bars to a simulated ordinary concrete environment for 3 and 6 months. The accelerated aging method was conducted at 60°C to accelerate the diffusion of moisture and hydroxyl ions into the carbon/glass-HFRP bars, which could rapidly aggravate the degradation of the HFRP bars. Moisture absorption tests, scanning electron microscopy, and Fourier-transform infrared spectroscopy were performed to reveal the degradation mechanisms of the fiber, matrix, and fiber/matrix interfaces in the exposed samples. The tensile ductility of the samples after exposure was lower than that of the samples before exposure. The tensile strength retention of the exposed samples depended on the volume fraction of carbon fibers and the total volume fraction of the fibers, which could be considered in the prediction model of tensile strength retention of the exposed carbon/glass-HFRP bars.

Study on durability of transverse shear properties for novel carbon/glass hybrid fiber‐reinforced polymer bars in simulated concrete environments

AbstractDurability on the transverse shear properties of hybrid fiber‐reinforced polymer (HFRP) bar may control the cross‐sectional load‐bearing capacity and failure mode of the HFRP bar reinforced concrete members due to its strength degradation with time. Herein, the degradation of novel carbon/glass (C/G)‐HFRP bars were accelerated in simulated concrete environments at 60°C to investigate the effects of fiber volume fraction and distribution pattern, matrix resin volume fraction, exposure environment, and period on their transverse shear properties. The results displayed that the transverse shear strength of the samples reduced by 15%, 20%, and 8% after exposure to the simulated ordinary concrete, seawater sea‐sand concrete environments, and tap water for 6 months, respectively. The inward diffusion of water molecules and free hydroxyl ions caused the hydrolysis of matrix resin, etching of glass fiber and debonding of fiber/matrix interface, which were the incentives of the degradation of C/G‐HFRP bars. The increase of matrix resin volume fraction and the application of a waterproof coating were recommended to alleviate the degradation of fibrous composites in concrete environments. Finally, two prediction models were proposed to determine the transverse shear strength of HFRP bar before and after exposure to different harsh environments, respectively. The comparisons indicated that the predicted values were coincided with the experimental results.

Surface Hydroxyl-Ion Diffusion and Hierarchical Structure of Adsorbed Water on Hydrated Layered Double Hydroxides

Surface Hydroxyl-Ion Diffusion and Hierarchical Structure of Adsorbed Water on Hydrated Layered Double Hydroxides

Evaluation of pH and Calcium Ion Diffusion from Intracanal MTA and Bioaggregate to Simulated External Resorption Cavities Through Dentinal Tubules

Purpose: This in vitro study compared the effects of mineral trioxide aggregate (MTA), BioAggregate and calcium hydroxide on calcium and hydroxyl ion diffusion through dentinal tubules to the root surfaces without cementum in various root levels. Materials & Methods: The study consisted of 120 mature single-rooted mandibular premolar teeth. The teeth were decoronated and instrumented using Protaper Universal rotary files. To simulate external root resorption, artificial defects were created in cervical-middle-apical thirds of root surfaces. The teeth were divided into four main groups: Control (1), calcium hydroxide (2), MTA (3) and BioAggregate (4). In control group, root canals of specimens left empty. Other root canals of specimens filled with calcium hydroxide, MTA or BioAggregate. Each specimen was immersed in a vial containing 10 mL distilled water. Calcium concentrations and pH of the immersion media was measured at 1, 3, 7, 14, 21 and 28 days. Statistical analysis was accomplished by Kruskal–Wallis H and Mann–Whitney-U tests. Results: This study indicated that intracanal placement of both calcium hydroxide, MTA and BioAggregate resulted in the diffusion of calcium and hydroxyl ions across dentine. The results showed greater calcium and hydroxyl ions released by calcium hydroxide groups than MTA and BioAggregate groups (p<0.05). MTA and BioAggregate groups showed similar properties and there were no differences between these groups in whole study period (p>0.05). Conclusion: MTA and BioAggregate may be preferable for external root resorption cases because of their stimulation of hard tissue formation and ion releasing ability.

Influence of Filling Material Remnants on the Diffusion of Hydroxyl Ions in Endodontically Retreated Teeth: An Ex Vivo Study.

To assess the influence of remnants of filling material on hydroxyl ion diffusion from calcium hydroxide (CH) paste, measured by the pH value, in retreated teeth. A total of 120 single-rooted extracted teeth were prepared up to a size 35 hand file and filled. For retreatment, the specimens were divided into four groups (n = 20): ProTaper Universal Retreatment (PUR), PUR with additional instrumentation (PURA), Mtwo Retreatment (MTWR), and MTWR with additional instrumentation (MTWRA). Negative (NEG) and positive (POS) control groups were composed by 20 specimens each one. The specimens, except NEG, were filled with CH paste. The retreated groups were scanned using cone-beam computed tomography (CBCT) for analysis of filling remnants. The pH assessment was performed at the baseline, after seven, 21, 45, and 60 days of immersion in saline. Data were analyzed using Shapiro-Wilk and Levene's test, followed by a two-way analysis of variance (ANOVA) and Tukey's test. Additional instrumentation (PURA and MTWRA) were superior regarding removal of the filling material (p <0.05); however, without significant difference (p >0.05). The mean pH value in all groups increased (p <0.05). After 60 days, no statistical difference was observed among POS and PURA; and MTWR and MTWRA. There was less diffusion of hydroxyl ions when the amount of remnants was greater than 59%. Additional instrumentation improved the ability to remove filling material in both systems. All groups presented increasing pH; however, the higher the amount of remnants, the lower the diffusion of hydroxyl ions. The amount of remnants allows less diffusion of calcium hydroxyl ions. Thus, additional instrumentation improves the ability to remove these materials.

Improvement of acid resistance of Zn-doped dentin by newly generated chemical bonds

Dental caries, the world’s most prevalent infectious disease, is caused by the diffusion of hydroxyl ions into tooth structures. To prevent dental caries, the application of fluoride (F) and zinc (Zn) ions to teeth surfaces are potential effective measures. In this study, The ionic influence, especially the chemical bond of F and Zn, on the acid resistance of dentin were investigated by particle induced X-ray / gamma-ray emission, X-ray diffraction, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The results showed Zn was distributed in the limited surface layer of dentin without altering its crystal structure. From the Zn K edge extended X-ray absorption fine structure, Zn incorporated into dentin was surrounded by oxygen and demonstrated four-fold coordination. The bond length and chemical state of Zn–O in Zn doped dentin suggested newly generated Zn–O covalent bond, which may improve acid resistance of dentin. This study showed that the atomic and molecular structures, such as the molecular distances and chemical state, influenced acid resistance of teeth, emphasizing the validity of chemical state analysis for understanding properties in biomaterials.

Comparative evaluation of diffused calcium and hydroxyl ion release from three different Indirect pulp capping agents in permanent teeth – An in vitro study

BackgroundIndirect pulp capping therapy has gained increased popularity in paediatric dentistry since it is less invasive, and is of low cost. The aim of the present study was to evaluate and to compare the diffusion of calcium (Ca2+) and hydroxyl (OH–) ions through coronal dentin into pulp after indirect pulp capping in vitro using TheraCal LC, ProRoot MTA and Calcimol LC. Materials and methodsTotal of 60 human caries-free maxillary first premolars were selected for the study. Samples were divided into 4 groups with 15 in each group: Group 1 TheraCal LC; Group 2 ProRoot MTA; Group 3 Calcimol LC; Group 4 Control Group. Indirect pulpcapping on the coronal RDT (remaining dentine thickness) system was performed using pulp-capping materials, such as TheraCal LC, ProRoot MTA and Calcimol LC, on the respective samples. The control group was completely filled with composite. Ca2+ ions (ppm) and OH– ions (pH) were analysed in deionized water using a multimeter connected to a calcium probe (calcium ion electrode) and pH metre connected to a temperature-compensated pH probe after 3 h, 24 h, 7 days, 14 days, 28 days and 60 days. ResultsCalcium release was significantly higher (P < 0.05) in the TheraCal LC group than in the other groups. Slightly alkaline pH values were observed in all the groups except for the control. ConclusionTheraCal is a new light-curable pulp capping material that initially releases high Ca2+ ions and creates an environmental pH close to physiological pH after 60 days.

Evaluation of the diffusion of calcium hydroxide-based medicaments through the dentinal tubules and apical foramen: A mass spectrometry study.

Aims:This mass spectrometry study investigated the diffusion of hydroxyl and calcium ions from a calcium hydroxide intracanal medicament (Pulpdent®) when used alone or mixed in equal parts with a steroid–antibiotic paste (Ledermix®).Materials and Methods:The pH (using pH meter) and calcium ion concentration (using inductively coupled plasma-mass spectrometry) of the diffused medicaments were assessed using endodontically prepared human extracted teeth with either a sealed or a patent apex, at time intervals of 1, 3, 8, 24, and 168 h.Statistical Analysis:A one-way ANOVA was used to explore differences between and within groups, with Tukey–Kramer/Games–Howell posttests.Results:In both situations tested, Pulpdent® showed greater release of both calcium and hydroxyl ions than when mixed in equal parts with Ledermix®. Greater initial release of both ions occurred in roots with a patent apex, but by 1 week there was no significant difference between the two. If a 50:50 combination of Pulpdent® paste and Ledermix® paste is used, there is a lower release of calcium ions and hydroxyl ions than using Pulpdent® paste alone.Conclusion:With both Pulpdent® paste alone and Pulpdent® paste mixed equally with Ledermix® paste, the major pathway for movement of hydroxyl ions and calcium ions is diffusion through the dentine of the root, with the apex playing only a minor role.

Comparative properties characteristics of the various pastes based on calcium hydroxide

Calcium hydroxide is widely used as a interappointment root canal filling material due to its favorable alkaline effect. It is assumed that the action occurs from the diffusion of hydroxyl ions through the apical foramen. The aim of this article was to review studies of the various properties of pure calcium hydroxide, as well as its commercial analogues.

Fabrication and electrical double-layer capacitance performance of interconnected and independent titania nanotube array

ABSTRACT The interconnected and independent titania nanotube array (TiO2 NTA) grown on titanium metal foil with tunable nanotube diameter and length is fabricated by ultrasonic bath-assisted anodisation process. The electrical double-layer capacitance is highly dependent on the nanotube microstructure, crystal phase and working electrolyte. Anatase TiO2 NTA shows cyclic voltammetry-based current response and capacitance in H2SO4 rather than NaOH electrolyte, which is due to higher electrical conductivity and more effective proton diffusion rather than hydroxyl ion diffusion. Interconnected and independent TiO2 NTA with a diameter of 60, 120, 200nm and a length of 0.62, 1.69, 1.28μm exhibits galvanostatic charge-discharge based capacitance of 0.76, 1.88 and 2.63 mF cm−2 at 0.1mA cm−2 in 1.0M H2SO4 electrolyte. The superior capacitance performance of independent TiO2 NTA is ascribed to more effective ion diffusion in the enlarged independent nanotube channels. TiO2 NTA with a tunable microstructure is accordingly suitable for supercapacitor electrode substrate application.

A flexible paper-based hydrogen fuel cell for small power applications

In this work, a paper-based hydrogen fuel cell is developed without the need for hydrogen storage. Instead, an embedded aluminum foil inside the paper is utilized for in-situ hydrogen generation. The electrodes and current collectors are also deposited on the paper, leading to a lightweight, compact and flexible hydrogen fuel cell with an OCV reaching 0.93 V and a peak power density of 4 mW cm−2. Benefited from the impeded hydroxyl ion diffusion, the hydrogen generation rate is well controlled, leading to a high faradaic efficiency of 72%. In addition, the cell can be operated under different bending angles with negligible power loss. Furthermore, it can be conveniently stacked in the same piece of paper for higher voltage and power outputs. Such a novel fuel cell design is especially suitable for powering various flexible devices with small rated power.

Diffusion of hydroxyl ion on external root surface using different irrigating solutions: An In vitro study

The aim of this study was to evaluate the diffusion of hydroxyl ion to the external root surface using different irrigating solutions and intracanal medication with calcium hydroxide. Sixty bovine tooth roots were randomly divided into six experimental groups (n = 10), according to the irrigating substance used during biomechanical preparation: 12% glycolic propolis extract (PROP); 20% glycolic ginger extract (GENG); 2% sodium hypochlorite with surfactant (NaOClS); 2% chlorhexidine gel (CLX); 2.5% sodium hypochlorite (NaOCl); and physiological saline solution. After filling the root canals with calcium hydroxide paste, pH measurements were taken directly at the external cavities over time intervals of up to 30 days. Data were submitted to two-way ANOVA and Tukey's test (P < 0.05). The pH of the external root surface was increased when the surfactant associated with NaOCl was used. However, the pH values were very close for the different groups. Hydroxyl ion diffusion up to the external root surface did not exceed the pH value of 8.5, and in the hollow passage of the canal, the pH was higher than 12. Hydroxyl ion diffusion of calcium hydroxide paste through the dentinal tubules up to the external root surface allows minimal alkalinization of this surface, and it is greater when using NaOCl with surfactant during biomechanical preparation.

High temperature oxidation behaviour of Fe–15.7 wt.% Cr–8.5 wt.% Mn in oxygen without and with water vapour at 700 ºC

Fe–15.7 wt.% Cr–8.5 wt.% Mn was oxidised in O2 and O2–9 vol.% H2O at 700 °C. Oxide scales in both atmospheres consisted of M2O3 and M3O4 where M could be Mn, Cr and Fe. The graphical representation of the water vapour effect on the concentrations and dominant regimes of defects in the Brouwer diagram was proposed. The enhanced oxidation rate due to water vapour was found possibly as a result of the increased metal vacancy concentration and its dominant regime and the inwards diffusion of hydroxyl ions supported by the scale adhesion results.

A comparison of hydroxyl ion diffusion through root dentine from various calcium hydroxide preparations.

Different calcium hydroxide [Ca(OH)2 ] formulations are available. The aim was to assess differences in hydroxyl ion release with different formulations. Sixty-six teeth were divided one control (n = 6) and four experimental (n = 15) groups: (i) Pulpdent Paste; (ii): DT Temporary Dressing; (iii): Ca(OH)2 powder/saline; (iv): Ca(OH)2 points; (v): no medicament. pH was measured in inner dentine and outer dentine cavities over 12 weeks. Inner dentine pH rose rapidly for all groups except the points and controls. Peak pH was reached by day 2 before dropping and stabilising (8.0-9.2). Outer dentine pH rose steadily until day 21 for aqueous solutions and then stabilised (8.0-8.5). The points had minimal pH increase for the entire period. There were no significant differences in hydroxyl ion release between the aqueous solutions. Type of paste base did not affect release and diffusion of hydroxyl ions which continued for 84 days.

PH changes in radicular dentine associated with calcium hydroxide and corticosteroid/antibiotic pastes.

The aim was to compare hydroxyl ion diffusion through dentine following placement of calcium hydroxide and Ledermix paste. Thirty-six teeth were divided into one control (n = 6) and three experimental (n = 10) groups - (i) Pulpdent paste; (ii) Pulpdent/Ledermix pastes; (iii) Ledermix paste and (iv) Saline. pH was measured in inner and outer dentine cavities over 12 months. Inner dentine time to maximum pH (Tmax ) was 1 week for Pulpdent and 2 weeks for Pulpdent/Ledermix. Pulpdent's outer dentine Tmax was 4 weeks and Pulpdent/Ledermix was 10 weeks. After day 1, Pulpdent pH was higher and this continued for 12 months. Pulpdent's outer dentine pH was higher than Ledermix and controls, but not significantly different from Pulpdent/Ledermix. Pulpdent/Ledermix had significantly higher pH than controls and Ledermix from day 5 until 10 months when Pulpdent/Ledermix outer dentine pH decreased and became similar. In all groups, pH reduced after 3 months.

Comparison of Commercial Calcium Hydroxide Pastes for Prolonged Antibacterial Effect using a Colourimetric Assessment.

The anti-microbial activity of calcium hydroxide pastes used in endodontics is dependent on establishing high levels of hydroxyl ions in dentine. This study investigated hydroxyl ion diffusion from different commercial calcium hydroxide pastes using a novel colourimetric method. In this method, human tooth roots were stained with anthocyanin dye, which changed their colour according to the local pH conditions. Prepared root canals were filled with pastes formulated with the vehicle of water (Pulpdent™, Calasept Plus™), polyethylene glycol (PEG) (Calmix™) or a mixture of water, PEG and ibuprofen (Odontocide™). The changes in dye colour at fixed distances from the canal wall were monitored using standardised digital photography over a period of 3 weeks. A repeated measures analysis tracked changes in each root from baseline. Release of hydroxyl ions varied between the different commercial compositions containing water or PEG as solvents. The colour changes in the dentine, due to released hydroxyl ions, were greatest and more prolonged for completely non-aqueous compositions, when using PEG 400 as the vehicle. When water was present in the product, the duration of the pH changes was shorter. This was attributed to the presence of hydroxyl ions in the water (the common-ion effect) and a more vigorous buffering of hydroxyl ions by dentine proteins.

Hydroxyl Ion Diffusion through Radicular Dentine When Calcium Hydroxide Is Used under Different Conditions.

Calcium hydroxide’s anti-bacterial action relies on high pH. The aim here was to investigate hydroxyl ion diffusion through dentine under different conditions. Teeth were divided into control (n = 4) and four experimental groups (n = 10): Group 1—no medicament; Group 2—Calmix; Group 3—Calmix/Ledermix; Group 4—Calasept Plus/Ledermix; Group 5—Pulpdent/smear layer. Deep (inner dentine) and shallow (outer dentine) cavities were cut into each root. pH was measured in these cavities for 12 weeks. The inner and outer dentine pH in Group 2 was significantly higher than all groups. Inner dentine pH in Group 3 was slightly higher than that in Group 4 initially but subsequently comparable. After Day 2, Group 5 had significantly lower pH than Groups 3 and 4. The outer dentine pH in Group 3 started higher than that in Groups 4 and 5, but by Day 28 the difference was insignificant. The time for the inner dentine to reach maximum pH was one week for Group 2 and four weeks for Groups 3 and 4. The time for the outer dentine to reach maximum pH was eight weeks for all experimental groups. Mixing different Ca(OH)2 formulations with Ledermix gave similar hydroxyl ion release but pH and total diffusion was lower than Ca(OH)2 alone. The smear layer inhibited diffusion.

Application of scanning electrode techniques for the evaluation of iron–zinc corrosion in nearly neutral chloride solutions

A model cut edge consisting of a zinc anode and a split iron cathode was used for studying corrosion mechanisms and assessing the suitability of scanning electrochemical techniques for corrosion studies at the microscale. Scanning electrochemical microscope (SECM), localized electrochemical impedance spectroscopy (LEIS) and scanning vibrating electrode technique coupled with the scanning ion-selective electrode technique (SVET/SIET) were applied. The corrosion products precipitated on the cathode once the critical pH and solubility limits were reached, which resulted from the diffusion of hydroxyl and zinc ions across the cathode. There was no evidence of self-healing by the corrosion products.

Effect of passive ultrasonic irrigation on diffusion of hydroxyl ion through radicular dentine.

This study investigated the effect of passive ultrasonic irrigation (PUI) on diffusion of hydroxyl ions through radicular dentine. After chemomechanical preparation of root canals in 60 human teeth, the cementoenamel junction and the apical 3 mm of each root were covered with fast-setting adhesive. Four final irrigation protocols were applied (n = 10): group (G)1: irrigation with EDTA + NaOCl; G2: EDTA + PUI + NaOCl; G3: EDTA+(NaOCl + PUI); G4: (EDTA + PUI) + (NaOCl + PUI). Ten teeth irrigated with distilled water followed by PUI (G5) served as the negative control. After drying, the canals were filled with calcium hydroxide paste (CH), sealed and kept in individual vials containing 10 mL of distilled water with known pH values. At 7, 14, and 21 days, the pH of the water in the vials was measured. The pH values in various groups were analyzed with two-way ANOVA (irrigation protocol and time period as factors) and Holm-Sidak multiple comparison test (α = 0.05). Changes in pH was not significantly different among groups (P = 0.651) but was significant different among different time periods (P < 0.0001). For all groups, ion diffusion was higher at 14 and 21 days than at 7 days. PUI has no effect on diffusion of hydroxyl ions through radicular dentine. When CH is used as temporary filling material, a waiting period of at least 14 days is required to create an alkaline environment within the radicular dentine. The use of PUI during final irrigation phase does not improve the action of CH when it is used as temporary filling material.