Effect of phytate and hexadecylamine on the permeability of bovine dental enamel

The effect of hexadecylamine on the permeability of bovine dental enamel was investigated using a radiochemical diffusion technique. Treatment with an aqueous solution of hexadecylamine reduced the permeability of the enamel by about 20 per cent. Pre-treatment of the enamel with an aqueous solution of phytate followed by hexadecylamine yielded a reduction in permeability of ~ 70 per cent. The observed effects were similar for ionic (⁸⁶Rb⁺ and ³⁶Cl^?) and nondashionic ([³H]-sorbitol and [¹⁴C]-glycerol) compounds. The strong permeability-reducing effect of the combined phytate-amine treatment may also be anticariogenic.     

Preparation,characterization, and electrocatalytic properties of copper hexacyanoferrate film and bilayer film modified electrodes

Copper(II)hexacyanoferrate films have been prepared from various electrolyte aqueous solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of copper(II)hexacyanoferrate films from the mixing of Cu²⁺ and Fe(CN)₆^3? ions from solutions of ten cations: Li⁺, Na⁺, K⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, H⁺ and Al³⁺. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the copper(II)hexacyanoferrate films. The copper(II)hexacyanoferrate film showed a single redox couple that exhibited a cation effect (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) and an anion effect (F^?, Cl^? and Br^?) in the cyclic voltammograms and formal potential of the redox couple. The electrochemical and EQCM properties of the film indicate that the redox process was confined to the immobilized copper(II)hexacyanoferrate, and the interaction between the copper(II)hexacyanoferrate film with K⁺ (monovalent cation) and Ca²⁺ (divalent cation). The electrocatalytic oxidation properties of NADH, NH₂OH, N₂H₄, SO₃^2? and S₂O₃^2? were also determined. The electrocatalytic reduction properties of SO₅^2? and S₂O₈^2? by monolayered iron, nickel, and cobalt hexacyanoferrate films, and by bilayered metal–copper hexacyanoferrate films were determined. Two-layered modified electrodes and hybrid films composed of a copper(II)hexacyanoferrate film with iron(II)hexacyanoferrate, cobalt(II)hexacyanoferrate, or nickel(II)hexacyanoferrate film were prepared, and these films caused the electrocatalytic reduction of SO₅^2? and S₂O₈^2?.     

EMF measurements across hydroxyapatite membranes

An attempt was made to develop models applicable to the study of ionic transport in dental enamel. Membranes of hydroxyapatite, made by compression of the powdered salt, were mounted on the septum of concentration cells. Electrical potential differences, PD, were measured across the membranes using solutions of CaCl₂, NaCl, KCl, and potassium and sodium phosphates. With CaCl₂, the membrane acquired a net positive charge and the PD values were close to those expected for an ideal permselective membrane. High permselectivity and a net negative charge on the membrane were observed with solutions of Na₂HPO₄ and K₂HPO₄. The PD values obtained with NaCl and KCl solutions were close to those calculated for the junction potentials of the electrolytes; thus, for these uni-univalent salts the membrane behaved as an inert porous barrier. The permselective behaviour was interpreted in terms of sorption of Ca²⁺ and phosphate ions probably related to defects in the hydroxyapatite crystals. The lack of interaction with K⁺, Na⁺, and Cl^? was ascribed to the reduced ionic charge and the relatively large pore sizes of the membrane.When the membranes were mounted on an intraoral device and exposed to the oral environment prior to the PD measurements, the electrochemical behaviour of the membrane changed drastically. The PD values obtained were consistent with the acquisition of a net negative charge on the membrane surface. This negative charge decreased during the initial time (several hours) of measurements but persisted if saliva was added to the electrolyte solutions. A rapid adsorption of salivary proteins is thought to be responsible for the change of the membrane properties after intraoral exposure.It was concluded that any model developed to study ionic transport in dental enamel should include the interactions with the salivary constituents and the presence of the tooth pellicle.     

Characterization and electrocatalytic properties of cobalt hexacyanoferrate films immobilized on Au-colloid modified gold electrodes

An electroactive cobalt hexacyanoferrate (CoHCF) film was electrodeposited from a solution containing Co²⁺ and Fe(CN)₆^3? ions on the bare gold or the Au-colloid modified electrode. The cation (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺) and the anion (F^?, Cl^? and Br^?) effects on the redox peak of the CoHCF film were investigated in detail. On the other hand, the electrocatalytic oxidations of thiosulfate at the CoHCF/gold and CoHCF/Au-colloid/gold electrodes were compared. At the CoHCF/Au-colloid/gold electrode, we obtained a response current larger by a factor of 2 and a three times lower detection limit than those at a CoHCF/gold electrode. The linear ranges were 1.0 × 10^?4 to 2.8 × 10^?3 M for the CoHCF/gold electrode and 7.5 × 10^?5 to 4.8 × 10^?3 M for the CoHCF/Au-colloid/gold electrode. These results showed that the immobilized CoHCF at the Au-colloid modified electrode exhibited a higher catalytic activity and a wider linear range toward thiosulfate. Additionally, the effects of the applied potential and the solution pH were studied.     

Diffusion through bovine tooth enamel as related to the water structure in its pores

Diffusion coefficients of ⁸⁶Rb⁺, ³⁶Cl^?, [³H]-sorbitol and [¹⁴C]-glycerol through enamel were determined both in the absence and the presence of urea or t-butanol which are known for their structure-breaking and structure-promoting properties respectively in aqueous solutions. Their effect on the diffusion coefficients could be explained solely on the basis of the respective shifts in the relative viscosities of the aqueous solutions, indicating that the water of the transport phase is probably free water, in accord with explanation for the extra increase of diffusion coefficients with temperature (Burke and Moreno, Archs oral Biol.17, 433–437 (1975)) by the hypothesis that the amount of free water increases with temperature at the expense of bound water.     

Calcium-stimulated ATPase of dog submandibular gland

A Ca^2?-stimulated ATPase present in a microsomal fraction prepared from canine submandibular glands was investigated. The Ca²⁺ concentration for half maximal activation of the enzyme was about 0.3 mM. Addition of Mg²⁺ to incubation media containing Ca²⁺ decreased the ATPase activity. The presence of neither Na⁺ nor K⁺ is required for Ca²⁺-activation of the enzyme. Also, Ca²⁺ will not substitute for Mg²⁺ in the Mg²⁺-dependent (Na⁺ + K⁺)-ATPase reaction. The Ca²⁺-activation was not appreciably affected by ouabain (10^?4M), but was inhibited by about 50 per cent by 5 × 10^?3M ethacrynic acid. These studies provide a possible enzymatic basis for the calcium uptake by salivary gland microsomes that has been reported by other workers.     

Alkaline phosphatase activity in the enamel organs of normal and rachitogenic rats.

A number of characteristics of alkaline phosphatase (AP) in the enamel organ were investigated in normal and D-deficient rats. From the tests of the substrate dependence it appeared that AP in the enamel organ from D-deficient rats had twice the activity compared with AP from normal rats. The apparent K_m value of AP from D-deficient rats was 4.6 × 10^?4M, significantly higher than the value in normal rats (3.3 × 10^?4M), pH optimum was 10.4 in both groups. Results from activation and/or inhibition with Mg²⁺, Ca²⁺, F^?, PO₄^3? and l-phenylalanine showed that the AP from the enamel organ has the same characteristics as AP from various other tissues.     

Sialochemistry and cortisol levels in patients with Sjogren's syndrome

Oral Diseases (2012) 18 , 255–259 Objectives: (i) To determine whether salivary cortisol and electrolyte levels differ between patients with Sjogren’s syndrome (SjS) and healthy individuals. (ii) To assess correlations between whole‐saliva cortisol and some clinical manifestations in patients with SjS. Methods: A total of 24 healthy women (mean age 49.3 ± 9.8) served as controls (C) vis‐à‐vis 17 patients with SjS (mean age 55.5 ± 15.7). Salivary cortisol concentration was determined, and sialochemistry analysis was performed. Results: Significantly lower saliva flow rates and higher salivary chloride (Cl^?), potassium (K⁺), and Ca²⁺ levels were found in the SjS group. No significant differences or correlations were found in other parameters, including sodium (Na⁺), magnesium (Mg²⁺), phosphate (^?), urea (U), and salivary cortisol levels. Conclusion: Increased whole‐salivary output of Cl^? and K⁺ in SjS may reflect release from apoptotic rests of acinar cells after secondary necrosis. Normal levels of salivary Na⁺, Mg²⁺, and ^? argue against concentration effect, deranged tubular function or cortisol (mineralocorticosteroid) effect as the cause for these findings. Increased salivary Ca²⁺ levels probably reflect leakage of plasma Ca²⁺ through the injured oral mucosa in SjS. In spite of disease‐associated stress, salivary cortisol, a stress biomarker, was not increased, suggesting insufficient hypothalamus–pituitary–adrenal (HPA) axis response and/or local consumption of cortisol by lymphocyte infiltrates.     

Ion release and enamel remineralizing potential of miswak,propolis and chitosan nano-particles based dental varnishes

Purpose

Natural products can have an important role in caries control through their inherent biological abilities.

DFT calculations of the interaction of alkali ions with copper and silver

The interaction of alkali ions with the Cu(100) and Ag(100) surfaces is studied using the DFT method. The results of the B3LYP calculations performed for five cations, Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺, adsorbed on the surface of the M₁₂(6,6) cluster (M=Cu, Ag) are presented. On both metals the interaction is found to be strongest for the Li⁺ ion and weakest for the Cs⁺ ion. Three sites were tested for the adsorption of ions on the (100) surface: top, bridge and hollow. For the two smaller ions, Li⁺ and Na⁺, the hollow site is found to be the most stable. For the three larger ions the top position is more attractive. Nevertheless, the energy value at the different sites for a given ion in most cases, differs by less than 5 kJ mol^?1. For all ions the interaction with silver is stronger than the interaction with copper.     

The Electrolyte and Water Secretion Mechanism

The currently accepted salivary gland secretion model describes the process of fluid secretion as the coordinated action of water and ion channels and transporters. The secretion of electrolytes and water by salivary glands is thought to be activated by an agonist-induced increase in the intracellular free [Ca²⁺] and to be driven by transepithelial chloride movement. The Cl^- transport is supported by upregulation of several ion transporters, K⁺ and Cl^- channels, and the Na⁺/K⁺-ATPase. This review will focus on the details of the transport mechanisms as well as recent developments in confirming the molecular identities of the involved transporter and channel proteins.     

ATP-ase activity in the odontoblastic layer of rat incisor Determination with a radiochemical and a colorimetric method

The ATP-splitting enzyme activity in odontoblasts isolated from rat incisors has been studied by means of a radiochemical and a colorimetric micromethod. The results with the two methods were virtually identical. The reaction was linear with time for at least 45 min. The pH optimum was found to be 9.8 independently of the ATP concentration. Maximal substrate saturation occurred at a total ATP concentration of 3 mM. Ca²⁺ and Mg²⁺ ions activated ATP degradation. F- ions did not affect the activity at low concentrations, whereas higher concentrations were inhibitory. Na⁺ and K⁺ ions had no influence on ATP splitting enzyme activity, while PO4^3- ions were slightly inhibitory. Urea inhibited the enzyme activity at concentrations above 1.5 M, while EDTA and EGTA were strong inhibitors at very low concentrations. When incubating in the presence of low concentrations of specific inhibitors for nonspecific alkaline phosphatase, levamisole and R 8231, about 20% ATP degrading enzyme activity remained. In conclusion it is suggested that there are at least two ATP degrading phosphatases active at alkaline pH.     

Ca2+ Channels in Odontoblasts

Odontoblasts, well-polarized columnar cells at the periphery of the dental pulp, originate from neural crest cells. They are primarily involved in dentin formation (dentinogenesis) as sites of the synthesis and secretion of collagenous and non-collagenous matrix proteins, and also participate in the directional transport of Ca²⁺ from the circulation to the dentin/mineralizing front. Dentinogenesis is activated by : 1) pulpal patho-physiological events, such as intra-pulpal inflammatory responses, physiological or developmental processes, and 2) events at the dentin surface, such as variousimechanical/heat/coldjstimuli applied to the tooth surface. Therefore, the aim of this communication is to give an overview of the Ca²⁺-signaling system, which may have a major role in dentin formation in both physiological and pathological settings. Special attention will be given to discussion of the following : 1) sequential Ca²⁺ signaling pathways from internal inositol 1,4,5-trisphosphate (IP₃) production via the activation of phospholipase C-coupled receptors to the release of Ca²⁺ from IP₃-sensitive Ca²⁺ stores, 2) subsequent Ca²⁺ influx via store-operated Ca²⁺ channels, and 3) the expression of transient receptor potential channels coupled with Na⁺-Ca²⁺ exchangers in odontoblasts.     

Studies on ion transport during potential cycling of a Prussian blue (inner) | polyaniline (outer) bilayer electrode by quartz crystal microbalance and Fourier transform infrared reflection spectroscopy

Ion transport during the redox switching of a Prussian blue (PB) | polyaniline (PAn) bilayer electrode has been investigated by means of an electrochemical quartz crystal microbalance (EQCM) and in situ Fourier transform infrared (FTIR) reflection spectroscopy. The movement of ions in the potential cycling of the bilayer electrode is affected considerably by the thickness ratio of PB to PAn and the electrode potential. It is at the bilayer electrode with the medium thickness ratio (2.5–3.25) of PB (165 nm) to PAn that cation (K⁺) and anion (Cl^?) move simultaneously in opposite directions. On the positive scan of such an electrode, K⁺ ions are first ejected from PB to the PAn layer into which Cl^? ions are concurrently taken from solution to maintain the charge balance. The oxidation of PAn at more positive potential leads to the expulsion of K⁺ ions to solution and the simultaneous incorporation of Cl^? ions.     

Ion-channel-mimetic sensor for trivalent cations based on self-assembled monolayers of thiol-derivatized 4-acyl-5-pyrazolones on gold

Self-assembled monolayers (SAMs) of thiol-derivatized 4-acyl-5-pyrazolone on gold electrodes were used for ion-channel-mimetic sensing of inorganic cations. The SAMs on gold electrodes were characterized with reductive-desorption and capacitance measurements. The pH dependence of the cyclic voltammograms (CVs) of [Fe(CN)₆]^3? and [Ru(NH₃)₆]³⁺ as electroactive markers suggested the protonation not only of the β-diketone part but also of the nitrogen moiety in the pyrazolone. With regard to the voltammetric responses to metal cations, an increase and a decrease in redox current of [Fe(CN)₆]^3?/4? and [Ru(NH₃)₆]^3+/2+, respectively, were observed with increasing concentrations of the trivalent cations examined (La³⁺, Gd³⁺, Yb³⁺ or Al³⁺) from 10^?6–10^?4 up to 10^?2 M at pH 5.5, at which the chelating group is present as its deprotonated form. In contrast, such responses were negligible in the presence of up to 10^?2 M divalent cation (Mg²⁺, Ca²⁺, Sr²⁺ or Ba²⁺), Li⁺ or Na⁺. The order of the magnitudes of the responses was Al³⁺>Yb³⁺≈Gd³⁺>La³⁺?divalent cations, which is quite similar to that of the stability of 1:1 and 1:2 complexes between a β-diketonate-type chelate and the metal ions. The highly selective responses to trivalent cations seem to reflect the selectivity of the chelating group as well as the large change in the surface charge induced by the complexation.     

Preparation,characterization and electrocatalytic properties of polynuclear mixed-valent ruthenium oxide/hexacyanoruthenate film modified electrodes

Polynuclear mixed-valent ruthenium oxide/ruthenocyanide (ruthenium oxide/hexacyanoruthenate or mvRuO/RuCN) films were prepared using consecutive cyclic voltammetry directly from the mixing of Ru³⁺ and Ru(CN)₆^4? ions from solutions of two divalent cations (Ba²⁺ and Ca²⁺), and seven monovalent cations (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Ga⁺). The films exhibited three redox couples with Ba(NO₃)₂ or BaCl₂ aqueous solutions, and the formal potentials of the redox couples showed a cation and pH effect. An electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, UV–visible spectroscopy, and the stopped-flow method (SFM) were used to study the growth mechanism of the mvRuO/RuCN films. The results indicated that the redox process was confined to the immobilized ruthenium oxide/ruthenocyanide. The EQCM results showed a Ba²⁺ ion exchange reaction for the two most negative redox couples. The electrocatalytic reduction properties of SO₅^2?, and S₂O₈^2? by the ruthenium oxide/ruthenocyanide films were determined. The electrocatalytic oxidation of NADH and dopamine were also determined, and revealed two different types of properties. The electrocatalytic oxidations of SO₃^2?, S₂O₃^2?, and N₂H₄ were also investigated. The electrocatalytic reactions of the ruthenium oxide/ruthenocyanide films were investigated using the rotating ring-disk electrode method.     

New EQCM,voltammetric and radiotracer evidences proving the role of Cu+ ions in the behavior of the Cu2+–Cu system

Combined EQCM and voltammetric studies in conjunction with radiotracer adsorption investigations were carried out in order to obtain direct information on the interfacial behavior of the Cu²⁺–Cu system under equilibrium and dynamic conditions with the aim of clarifying the role and participation of Cu⁺ ions formed by the interaction of cupric ions and copper metal. The appearance and accumulation of Cu⁺ ions in the solution phase is clearly demonstrated through radiotracer experiments using labeled Cl^? ions. The formation of bulk CuCl phase is preceded by the formation of a CuCl surface layer. Data obtained from combined voltammetric and EQCM studies allow us to separate the potential regimes where the electrosorption, the formation of Cu⁺ or Cu²⁺ ions, and dissolution of CuCl are the predominant processes.     

Effect of calcitonin on ca-stimulated adenosine triphosphatase activity in a plasma membrane-rich fraction of rabbit dental pulp in vitro

The effect of calcitonin, a polypeptide hormone, on Ca²⁺-ATPase activity was studied using a plasma membrane-rich fraction isolated from rabbit dental pulp in vitro. Stimulation of Ca²⁺-ATPase activity occurred at low concentrations of Ca²⁺. There may be a relationship between Ca²⁺-ATPase and Ca²⁺ transport in plasma membrane of dental pulp.     

Supplementation of soft drinks with metallic ions reduces dissolution of bovine enamel

Objective

The aim of this study was to evaluate the effect of the addition of metallic ions to carbonated drinks on their erosive potential.

Material and Methods

Powdered enamel was added to carbonated beverages (Coca-Cola^TM or Sprite Zero^TM and shaken for 30 s. The samples were then immediately centrifuged and the supernatant removed. This procedure was repeated 5 times with the beverages containing Cu²⁺, Mg²⁺, Mn²⁺ or Zn²⁺ (1.25-60 mmol/L). For Coca-Cola^TM, the concentration of each ion that exhibited the highest protection was also evaluated in combination with Fe²⁺. The phosphate or calcium released were analyzed spectrophotometrically. Data were analyzed using ANOVA and Tukey''s test (p<0.05).

Results

For Coca-Cola^TM, the best protective effect was observed for Zn²⁺ alone (10 mmol/L) or in combination (1 mmol/L) with other ions (12% and 27%, respectively, when compared with the control). Regarding Sprite Zero^TM, the best protective effect was observed for Cu²⁺ at 15 and 30 mmol/L, which decreased the dissolution by 22-23%. Zn²⁺ at 2.5 mmol/L also reduced the dissolution of powdered enamel by 8%.

Conclusions

The results suggest that the combination of metallic ions can be an alternative to reduce the erosive potential of Coca-Cola^TM. Regarding Sprite Zero^TM, the addition of Cu²⁺ seems to be the best alternative.     

The CaATPase activity of rat-incisor odontoblast vesicles

An homogenate of rat incisor odontoblasts had Ca²⁺ and Mg²⁺ ATPase activity and suitable storage conditions kept it stable for several days. Over 90 per cent of the activity was retained in a vesicle-rich microsomal fraction that removed about 85 per cent of the total material from the homogenate. This fraction was further characterized: the resolved Ca²⁺-activated ATPase activity, above the basal MgATPase activity, was 0.30 μmol P₁/min-mg total protein, and 50 per cent activated at free [Ca²⁺] equal 0.8 μM. This calcium dependency is consistent with an intracellular Ca²⁺-regulated enzymatic activity. The calcium ionophore, A23187, had no measurable effect on the CaATPase activity, which suggests that the odontoblast vesicles do not concentrate Ca²⁺ in a lipid bilayer compartment. Direct measurement of the uptake of ⁴⁵Ca²⁺ by the filtration method and parallel measurements of CaATPase activity on the same preparations under identical conditions indicated that the odontoblastderived vesicles have a coupling ratio of 0.024 Ca²⁺/ATP. This low coupling ratio and the lack of detectable compartmentalization of calcium indicate that the CaATPase activity of the odontoblast microsomes is not associated with a calcium pump. The [Ca²⁺] dependence of the activity suggests the CaATPase is under intracellular Ca²⁺ control, but its function is unknown.