Neutral Fluoride Research Articles

The effect of fluoride therapies on the morphology of bleached human dental enamel

The aim of this in vitro study was to evaluate qualitatively the surface morphology of enamel bleached with 35% hydrogen peroxide (HP) followed by application of fluoridated agents. Forty intact pre molars were randomly distributed into four groups (n = 10), treated as follows: Group I (control group) remained stored in artificial saliva at 37 °C, Group II - 35% HP; Group III - 35% HP + acidulated fluoride (1.23%) and Group IV - 35% HP + neutral fluoride (2%). The experimental groups received three applications of bleaching gel and after the last application all specimens were polished. This procedure was repeated after 7 and 14 days, and during the intervals of applications, the specimens were stored in artificial saliva at 37°C. Scanning electron microscopy (SEM) analysis showed superficial irregularities and porosities to varying degrees in bleached enamel compared to control group. Sample evaluation was made by attributing scores, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). SEM qualitative investigation demonstrated that 35% hydrogen peroxide affected human dental enamel morphology, producing porosities, depressions, and superficial irregularities at various degrees. These morphological changes were higher after the application of 1.23% acidulated fluoride gel.

Effect of rinsing with water immediately after neutral gel and foam fluoride topical application on enamel remineralization: An in situ study

Objective The aim of this study was to evaluate, in situ, the effect of rinsing with water immediately after neutral fluoride foam application (Foam) or fluoride gel application (Gel). Design Ten volunteers wore acrylic palatal appliances containing 4 enamel blocks selected by surface hardness with artificial caries. Five experimental regimes of 3 days each were set according to treatment: placebo; Gel and Foam followed by no rinsing or consuming of liquids or solids for the next 30 min; Gel and Foam followed by immediately washing with water jet. After each phase, surface hardness was again measured for analysis of mineral gain, evaluated through percentage of surface hardness recovery (%SHR) and integrated loss of subsurface hardness (ΔKHN). The concentration of loosely bound fluoride (CaF2) and firmly bound fluoride (FA-like) formed and retained were also determined. Results Fluoride treatments produced greater remineralization (%SHR and ΔKHN) compared to placebo group ( p < 0.05). There was no difference in the ability to promote remineralization and in the concentration of fluoride formed and retained, in each analysis, between Gel and Foam ( p > 0.05). Conclusion The data suggest that rinsing with water immediately after topical application does not seem to have an influence on the ability of fluoride to promote remineralization.

Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF 2(py) 4] +, mer-[CrF 3(terpy)], and fac-[CrF 3(Me 3tacn)]. Crystalline products isolated from solution exhibit μ 2-bridging by the fluoride ligands in a linear fashion between Na +-ions and chromium centres in catena-[Na(H 2O) 4(μ-F)- trans-{CrF(py) 4}](HCO 3) 2 and in the dimers [Li(H 2O) n (μ-F)- trans-{CrF(py) 4}] 2+ ( n = 3, 4). The uncharged chromium complexes fac-[CrF 3(Me 3tacn)] and mer-[CrF 3(terpy)] have been synthesized from mer-[CrF 3(py) 3] and shown to precipitate sodium salts from solution, of which 3[CrF 3(Me 3tacn)]·2Na(Bph 4)·solv and 6[CrF 3(terpy)]·4Na(Bph 4)·solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring the Na + cation separation down to 3.610 Å and 3.369 Å, respectively, which is much closer than the inter-cation distance in NaCl and comparable to that of NaF. DFT calculations support the notion of a strong interaction between Na + ions and neutral chromium(III) fluoride complexes. The calculations reproduce the magnitude and the counter-intuitive sign of the spectral shifts induced by second sphere complexation in solution, which originates in a breakdown of the assumption of parameter transferability in ligand-field descriptions.

Electrochemical Etching of NiTi Alloy in a Neutral Fluoride Solution

Electrochemical etching of NiTi alloy in a pH 6 fluoride solution is proposed as a convenient alternative to chemical etching in oxidizing HF media. Anodization produces protons at the electrode surface, and local acidification increases the concentration of HF that efficiently dissolves the surface oxides, promoting a sustained dissolution current that decreases with increasing mass-transfer rate. The voltammetric pattern includes a "pseudoplateau" at low potentials, in which only a metal dissolution takes place, and a steady current increase at higher potentials due to the onset of oxygen evolution. The treatment produces a semilustrous rough surface, showing a structure of shallow microscopic cavities in SEM images. EIS spectra recorded in the pseudoplateau region are similar to those observed during anodic polarization of Ti in HF and their analysis indicates formation of a thin barrier film of thickness increasing linearly with potential.

Relationships between Fluoride Intake, Urinary Fluoride Excretion and Fluoride Retention in Children and Adults: An Analysis of Available Data

The aim of this study was to examine the relationship between total daily fluoride intake (TDFI), daily urinary fluoride excretion (DUFE) and fractional fluoride retention (FFR) using available data, in order to clarify the ability of DUFE to predict TDFI and, therefore, the risk of fluorosis development. Examination of published reports of simultaneous measurement of TDFI and DUFE, together with data from two unpublished Chilean studies, yielded data for 212 children aged less than 7 years and for 283 adults aged 18–75 years, providing a total of 212 and 269 data points, respectively. The relationship between DUFE and TDFI was studied for children and adults, separately. Daily fluoride retention (DFR) was estimated as a function of TDFI in children and adults assuming an average 90% fluoride absorption, and the numerical relationships between the estimated FFR and the TDFI were explored. Limiting FFR values of 0.55 and 0.36 were found for children and adults, respectively, above a threshold of TDFI of 0.5 and 2 mg, respectively. Neutral fluoride balances were predicted when the TDFI was equal to approximately 0.07 mg F/day for children and 0.8 mg F/day for adults. For children and adults, it is possible to obtain reasonably good estimations of community-based TDFI and DFR, using DUFE data. The advantages and limitations of these relationships, together with the need for future studies, are discussed.

Electrochemical Etching of NiTi Alloy in a Neutral Fluoride Solution

Electrochemical etching of NiTi alloy in a pH 6 fluoride solution is proposed as a convenient, less dangerous procedure than traditional chemical etching in oxidizing HF media. Anodic polarization produces protons at the electrode surface, and local acidification increases the concentration of HF that efficiently dissolves the surface oxides, promoting a sustained dissolution current that decreases with increasing mass-transfer rate. The voltammetric pattern includes a “pseudoplateau” at low potentials, in which only a metal dissolution takes place, and a steady current increase at higher potentials due to the onset of oxygen evolution. The treatment produces a semilustrous rough surface, showing a structure of shallow microscopic cavities in scanning electron microscopy images. Impedance spectra recorded in the pseudoplateau region are similar to those observed during anodic polarization of Ti in HF, and their analysis indicates a formation of a thin barrier film whose thickness increases linearly with potential.

Electrochemical Etching of NiTi Alloy in a Neutral Fluoride Solution

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Stratified structure of anodically formed mesoporous silica

AbstractFilms of mesoporous silica are formed on silicon single crystal by high‐potential anodisation in neutral fluoride electrolyte. The films formed at 7–15 V potential exhibit a bright coloured aspect, characteristic of thin films of submicrometer thickness with flat parallel surfaces. SEM examination of cleaved profiles and X‐ray reflectivity curves point to a stratified structure of these films on the nanometric scale. The stacking period, on the order of 10 nm, is an increasing function of the preparation potential. This structure is clearly related to the well‐known oscillatory electrochemical behaviour observed above 3 V potential in the silicon/acidic‐fluoride‐electrolyte system. These observations confirm the idea that this oscillatory behaviour is accompanied by significant changes in the oxide morphology, namely a modulation of the porosity. The surviving of this oscillatory behaviour even though the interface is buried below a stack of several tens of oxide layers is a challenging observation for the theoretical modelling of the oscillation mechanism. We propose that periodic cracking of the inner oxide film may originate from a tensile stress due to electrochemically‐induced desiccation near the silicon/oxide interface. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Electrochemical behaviour of microcrystalline aluminium in neutral fluoride containing solutions

The electrochemical behaviour of microcrystalline pure aluminium coating (mc-Al), fabricated by a magnetron sputtering technique, has been investigated in NaF as well as NaF + NaCl aqueous solutions. Results indicate that the anodic polarization characteristic changes with NaF concentration. F − anions promote the formation of a passive film, whose semiconducting properties were investigated. When the F − concentration is high ([F −] ⩾ 0.03 mol/L) the passive film is mainly composed of aluminium fluoride, which is an n-type semiconductor on mc-Al and a p-type semiconductor on polycrystalline Al (pc-Al). In NaF + NaCl aqueous solutions, Cl − and F − ions compete in affecting the type of semiconducting passive films formed on mc-Al.

Enamel microabrasion in an individual with Cohen syndrome

This case report describes the esthetic dental treatment of a patient with Cohen syndrome where microabrasion was used to treat dental fluorosis. The patient's teeth had white and light yellow spots, which were diagnosed as moderate dental fluorosis. These spots were treated with microabrasion using pumice paste and 37% phosphoric acid. The paste was applied with a rubber cup on a low-speed handpiece and manually using a wooden stick. It took four appointments to treat all of the patient's teeth. Topical neutral fluoride was applied after each appointment to decrease any dental sensitivity. The esthetic result was satisfactory. Esthetic dental treatment may result in positive emotional and behavioral changes in patients with special needs.

Susceptibility to Hydrogen Absorption and Hydrogen Thermal Desorption of Titanium Alloys Immersed in Neutral Fluoride Solution under Applied Potential

The susceptibility to hydrogen absorption and hydrogen thermal desorption of titanium alloys has been investigated in a neutral 2.0% NaF solution at 37°C under various applied cathodic potentials. Ti-0.2Pd, Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys absorb hydrogen under less noble potentials than −1.5 V, −1.9 V and −1.4 V versus a saturated calomel electrode, respectively. The amounts of absorbed hydrogen of Ti-0.2Pd, Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys under an applied potential of −2.0 V for 24 h are approximately 1200, 100 and 1100 mass ppm, respectively. Upon immersion in the 2.0% NaF solution under an applied potential, the hydrogen thermal desorption behavior of Ti-0.2Pd alloy differs from those immersed in acid fluoride solutions, whereas the hydrogen thermal desorption behaviors of Ti-6Al-4V and Ti-11.3Mo-6.6Zr-4.3Sn alloys are similar to those immersed in acid fluoride solutions. The present results indicate that in a neutral fluoride solution, the effects of an applied potential on the hydrogen absorption and desorption behaviors of Ti-6Al-4V alloy are considerably smaller than those of commercial pure titanium reported previously, Ti-0.2Pd and Ti-11.3Mo-6.6Zr-4.3Sn alloys.

Electrochemical formation of porous silica: toward an understanding of the mechanisms

AbstractPorous silica may be formed by anodization of silicon in a neutral fluoride electrolyte. Applying a high potential leads to initiation of porous layer growth, which may be pursued at lower potentials. We have tried to improve our understanding of the growth process. Initiation of the growth appears to be caused by oxygen evolution, which leads to local acidification of the medium. In the steady state, ion depletion in the electrolyte may lead to the presence of a strong space charge. Experiments indicate that such a charged layer may represent at most a small fraction of the porous layer thickness. Theoretical estimates suggest that this effect may be neglected. A model, making use of the diffusion equations of the various species (H+, F–, HF, SiF62–), accounts for the current/potential curves and oxide layer thickness in a semiquantitative manner. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Mechanical Properties and Surface Characterization of Beta Titanium and Stainless Steel Orthodontic Wire Following Topical Fluoride Treatment

To study the effect of fluoride prophylactic agents on the loading and unloading mechanical properties and surface quality of beta titanium and stainless steel orthodontic wires. Rectangular beta titanium and stainless steel wires were immersed in either an acidulated fluoride agent, a neutral fluoride agent, or distilled water (control) for 1.5 hours at 37 degrees C. After immersion, the loading and unloading elastic modulus and yield strength of the wires were measured using a 3-point bend test in a water bath at 37 degrees C. A one-way analysis of variance and Dunnett's post hoc, alpha = .05, were used to analyze the mechanical testing data. Scanning electron microscopy was also used to qualitatively evaluate the wire topography as a function of the fluoride treatments. Unloading mechanical properties of beta titanium and stainless steel wires were significantly decreased (P <or= .05) after exposure to both fluoride agents. Corrosive changes in surface topography were also observed after exposure to both the neutral and the acidulated phosphate fluoride agents. The results suggest that using topical fluoride agents with beta titanium and stainless steel wire could decrease the functional unloading mechanical properties of the wires and potentially contribute to prolonged orthodontic treatment.

A new route for the formation of self-organized anodic porous alumina in neutral electrolytes

The present work reports the formation of regular porous aluminum oxide layers in neutral fluoride containing (NH 4) 2SO 4 electrolytes. For a fluoride free (NH 4) 2SO 4 electrolyte only irregular and thin porous alumina layers can be grown under these conditions. Upon addition of small amounts of fluorides highly regular, smooth high aspect ratio pore arrays can be produced. Pores with a typical diameter of approximately 50 nm and a length of several micrometers are formed. This finding significantly widens the spectrum of synthesis routes for ordered porous alumina structures and templates.

Effects of potential on hydrogen absorption and desorption behaviors of titanium in neutral fluoride solutions

The effects of potential on the hydrogen absorption and desorption of commercial pure titanium immersed in neutral 2.0% and 0.2% NaF solutions for 24 h have been investigated by hydrogen thermal desorption analysis. Hydrogen absorption occurs in both solutions under less noble potentials than −1.2 V versus a saturated calomel electrode. The amount of absorbed hydrogen increases with decreasing applied potential. Under the same applied potential, the amount of hydrogen absorbed in the 2.0% NaF solution is larger than that in the 0.2% NaF solution. Hydrogen thermal desorption is observed in the temperature range from 250–300 to 700 °C. For the 2.0% NaF solution, compared with the 0.2% NaF solution, the amount of hydrogen desorbed in the high temperature range is large. The hydrogen desorption behavior for neutral NaF solutions under the applied potential is not necessarily consistent with that for acidulated phosphate fluoride solutions without the applied potential reported previously.

Fracture of sustained tensile-loaded Ti–0.2% Pd alloy in acid and neutral fluoride solutions

The fracturing of Ti–0.2 mass% Pd (Ti–0.2Pd) alloy in acid and neutral fluoride solutions has been investigated by a sustained tensile-loading test. In 2.0% acidulated phosphate fluoride (APF) and neutral 2.0% NaF solution, the time to fracture of the Ti–0.2Pd alloy is shorter than that of commercial pure titanium for the same applied stress. In 2.0 and 0.2% APF solutions, fractures are characterized by a cup-cone mode irrespective of applied stress. In 2.0 and 0.2% NaF solutions, transitions from cup-cone to shear modes of the fractures are observed with decreasing applied stress. The results of the present study suggest that the susceptibility to fracturing of the Ti–0.2Pd alloy is higher than that of commercial pure titanium.

Hydrogen absorption of titanium and nickel‐titanium alloys during long‐term immersion in neutral fluoride solution

Hydrogen absorption of biomedical titanium and Ni-Ti alloys in a neutral fluoride (2.0% NaF) solution for up to 10,000 h at 37 degrees C has been evaluated by means of hydrogen thermal desorption analysis. For alpha titanium (commercial pure titanium), the amount of absorbed hydrogen was, at most, 10-30 mass ppm, and the corrosion product and hydride formation were revealed on the surface of the specimen by X-ray diffraction analysis. Ni-Ti superelastic alloy absorbed approximately 150 mass ppm of hydrogen, which was probably sufficient to result in the pronounced degradation of the mechanical properties, although corrosion was hardly observed. In contrast, hydrogen absorption of alpha-beta titanium (Ti-6Al-4V) and beta titanium (Ti-11.3Mo-6.6Zr-4.3Sn) alloys was negligible, although general corrosion was observed. The results of the present study indicate that the susceptibility of titanium and Ni-Ti alloys to hydrogen absorption in the neutral fluoride solution is different from that in the acidic fluoride solution reported previously.

Effect of APF gel on micromorphology of resin modified glass–ionomer cements and flowable compomers

The purpose of this study was to evaluate the surface micromorphology of resin modified glass-ionomer cements and flowable compomers. In the study two resin modified glass-ionomers and two flowable compomers were used to prepare standardized 20 cylinderic samples. Samples were divided into four groups. Surface treatments with APF gel for experimental groups (group B,C,D) or distilled water as a control (group A) were performed four times. In group B, only APF gel was applied. In group C, after the APF gel application, the samples were immersed into the demineralizing and remineralizing solutions. In group D, before the APF gel application, the buffer solution was applied. The examinations of the surface micromorphology of the materials were made by using scanning electron microscope (SEM). Results showed that in group B all of the materials except Compoglass Flow, and in group C all of the materials showed erratic behaviours. In group D, severe erratic effect (score 2) was obtained on the surfaces of Vivaglassliner and Dyract Flow, and for the others score 1 signals were found. The moderate degradation was obtained by applying of only APF gel on the surfaces of both material groups. The addition of pH circulation caused increasing of micromorphologic changes on the surfaces of all materials. The effect of application of buffer solution on the surfaces before APF gel changed according to the materials. If acidulated fluoride gel is preferred for prophylactic therapy in patients' mouth, for the success, either buffer or neutral fluoride have to be applied on the restored teeth by resin based materials before acidulated fluoride application.

Effect of fluoride prophylactic agents on the mechanical properties of nickel-titanium-based orthodontic wires

Titanium-based alloys have high corrosion resistance because they form a thin, stable oxide layer. Nevertheless, fluoride prophylactic agents can cause corrosion and associated discoloration of titanium-based orthodontic wires. The purpose of this investigation was to study the effects of fluoride prophylactic agents on the mechanical properties of nickel-titanium (Ni-Ti) and copper-nickel-titanium (Cu-Ni-Ti) orthodontic archwires. Preformed rectangular Ni-Ti and Cu-Ni-Ti wires were immersed in either an acidulated fluoride agent, a neutral fluoride agent, or distilled water (control) for 1.5 hours at 37 degrees C. After immersion, the loading and unloading elastic modulus and yield strength of the wires were measured with a 3-point bend test in a water bath at 37 degrees C, in accordance with the criteria in the current American National Standard/American Dental Association Specification No. 32 for Orthodontic Wires (2000). Scanning electron microscopy was also used to characterize the effects of the fluoride treatment on the wire topography. Unloading mechanical properties of Ni-Ti orthodontic wires were significantly decreased after exposure to both fluoride agents (1-way analysis of variance [ANOVA] and Dunnett's post hoc, alpha =.05); however, Cu-Ni-Ti wire mechanical properties were not significantly affected by either fluoride agent (1-way ANOVA, alpha =.05). Corrosive changes in surface topography were observed for both wires, with Cu-Ni-Ti appearing to be more severely affected. The results suggest that using topical fluoride agents with Ni-Ti wire could decrease the functional unloading mechanical properties of the wire and contribute to prolonged orthodontic treatment.

Formation of self-ordered nano-tubular structure of anodic oxide layer on titanium

Room temperature anodization of titanium foil specimens was carried out in 0.5 M phosphoric acid solution with addition of various halide ions. Addition of 0.138 M HF or NaF resulted in self-ordered nano-tubular oxide structure. Addition of bromide and chloride ions initiated only pitting and nano-pores were not observed during anodization. Acidified fluoride solution is found to be necessary to obtain ordered nano-structure as neutral fluoride solution did not form nano-pores. Instability of the oxide layer during anodization and formation of the self-ordered structure can be explained by the perturbation theory. Separation of individual nano-tubes of titanium oxide layer from the inter-connected nano-pores could be attributed to the possible repulsion forces of the cation vacancies.