Efficacy of in-office bleaching techniques combined with the application of a casein phosphopeptide-amorphous calcium phosphate paste at different moments and its influence on enamel surface properties

OBJECTIVES: The aim of this in vitro study was to investigate the efficacy of in‐office bleaching technique combined with the application of a casein phosphopeptide‐amorphous calcium phosphate (CPP‐ACP) paste (MI Paste–MI) at different moments and its influence on enamel surface properties. METHODS: Eighty bovine dental crowns were randomly allocated into eight groups (n = 10), and bleached with either 35% hydrogen peroxide (HP) or 37% carbamide peroxide (CP). Four different protocols of application of MI were considered: without MI, MI applied before bleaching, MI applied after bleaching, and MI applied both before and after bleaching. Bleaching effectiveness was measured by the VITA EasyShade spectrophotometer utilizing the CIEL*a*b* system (ΔE, ΔL*, Δa*, and Δb*). Color readings were measured at baseline, 7, 14, and 21 days. Hardness and roughness were measured at baseline (T0) and immediately after bleaching (T14). Data were subjected to the two‐way ANOVA for repeated measurements and Tukey's test at 5%. RESULTS: HP groups achieved the greatest color change. The application of a CPP‐ACP paste did not reduce the efficacy of bleaching peroxides. Samples bleached with CP showed decreased hardness at T14. Samples bleached with HP that received the application of MI before and before/after bleaching did not present hardness decrease at T14. Samples bleached with peroxides only and received MI after bleaching showed increased roughness at T14. CONCLUSIONS: The use of CPP‐ACP was able to prevent negative changes in roughness and hardness of bovine enamel when associated to hydrogen peroxide, and might be applied before/after the bleaching protocol. Microsc. Res. Tech. 75:1019–1025, 2012. © 2012 Wiley Periodicals, Inc.     

催化动力学光度法测定痕量普卢利沙星

经研究发现,在缓冲溶液NaOH-KH2PO4介质中,普卢利沙星对H2O2氧化罗丹明B褪色反应有明显的抑制作用,同时又研究该阻抑催化褪色反应的动力学条件,包括酸度、试剂的用量、温度、时间对反应的影响,以及共存离子的干扰,从而建立一种新的快速测定痕量普卢利沙星的阻抑动力学光度法。测定的线性范围为2.0～30μg/mL检出限为0.5μg/mL,回归方程为A=0.0078C+0.064。相关系数r=0996。该方法简便灵敏,准确,选择性好,用于药物中普卢利沙星的测定,获得满意的效果。     

Ultrastructural evaluation of enamel after dental bleaching associated with fluoride

This study evaluated the effects on human enamel after two bleaching procedures: with a fluoridated bleaching agent and with topical fluoride application postbleaching. It used 43 enamel blocks (3 mm(2) ) that were ground flat (600-2,000 grit) and polished with polishing paste (one and one-fourth). Specimens were randomly divided into three groups according to the bleaching procedure: (1) control group, (2) hydrogen peroxide 35% (HPF) and topical application of fluoride 1.23%, and (3) HP 38% (OP) with fluoride in its composition. Bleaching agents were used according to the manufacturer's instructions. Three methodologies were used: nanoindentation, to observe surface hardness and elastic modulus; atomic force microscopy, to observe surface roughness (R(a) - R(z)); and scanning electron microscopy, to observe the enamel surface effects. Group OP had a decrease in the elastic modulus after bleaching, which was recovered at 14 days. An increased roughness (R(a); 32%) was observed on group HPF and had an increased erosion on enamel surface (67%). It was concluded that topical application of fluoride, after using the nonfluoridated whitening agent, increased the roughness values and erosion of enamel.     

多参数食品安全现场快速分析仪的应用研究--保健品中过氧化氢快速测定

要提出了一种用于保健钙片中过氧化氢快速测定的新方法。采用乙酸锌、亚铁氰化钾和草酸氢钾作为前处理试剂，在弱酸性介质和60℃条件下提取过氧化氢。考查了提取温度和提取时间对过氧化氩检测性能的影响。采用本方法在30 分钟内即可完成对保健钙片中过氧化氢的快速定量测定。     

橙皮甙的电化学行为研究

用单扫示波极谱法,橙皮甙在0.1mol/LKH_2PO_4缓冲溶液中(pH4.60)有一灵敏的二阶导数峰,25℃时峰电位为-1.43V(vs、SCE),峰电流与橙皮甙浓度在2.5×10~(-7)～4.0×1O~(-5)mol/L范围内有良好的线性关系,检测限为1.2×10~(-7)mol/L。用本法测定了中药陈皮中总黄酮的含量,其结果令人满意。实验证明橙皮甙的电极反应机理为双电子的不可逆过程。此外,还证明了H_2O_2和·OH自由基可催化该还原电流,并讨论了橙皮甙对超氧阴离子自由基的清除作用。     

Atomic force microscopic analysis of hydrogen peroxide bleached kraft northern black spruce fibres

Hydrogen peroxide is a potent, relatively inexpensive oxidant that chemically degrades chromophoric components in pulps and textiles. Oxidation of cellulose is a byproduct of this process step that decreases the tensile strength of individual fibres. The residence time of pulp in the bleaching reactor must be optimized to achieve the desired brightness and minimizing fibre degradation. To evaluate the impact of peroxide bleaching at the microfibrillar level, a single black spruce tree was chosen and kraft pulped. Peroxide bleaching was conducted via benchtop polyethylene bag bleaching in a temperature-controlled waterbath. Atomic force microscopy (AFM) topographical images acquired before and after the bleaching step show dramatic changes in fibre structure consistent with delignification and defects in the surface topography. This was further verified by X-ray work at Brookhaven National Laboratory, NY, U.S.A.     

Shear bond strength and ultrastructural interface analysis of different adhesive systems to bleached dentin

Background: It remains unclear as to whether or not dental bleaching affects the bond strength of dentin/resin restoration. Purpose: To evaluated the bond strength of adhesive systems to dentin submitted to bleaching with 38% hydrogen peroxide (HP) activated by LED‐laser and to assess the adhesive/dentin interfaces by means of SEM. Study design: Sixty fragments of dentin (25 mm²) were included and divided into two groups: bleached and unbleached. HP was applied for 20 s and photoactivated for 45 s. Groups were subdivided according to the adhesive systems (n = 10): (1) two‐steps conventional system (Adper Single Bond), (2) two‐steps self‐etching system (Clearfil standard error (SE) Bond), and (3) one‐step self‐etching system (Prompt L‐Pop). The specimens received the Z250 resin and, after 24 h, were submitted to the bond strength test. Additional 30 dentin fragments (n = 5) received the same surface treatments and were prepared for SEM. Data were analyzed by ANOVA and Tukey's test (α = 0.05). Results: There was significant strength reduction in bleached group when compared to unbleached group (P < 0.05). Higher bond strength was observed for Prompt. Single Bond and Clearfil presented the smallest values when used in bleached dentin. SEM analysis of the unbleached specimens revealed long tags and uniform hybrid layer for all adhesives. In bleached dentin, Single Bond provided open tubules and with few tags, Clearfil determined the absence of tags and hybrid layer, and Prompt promoted a regular hybrid layer with some tags. Conclusions: Prompt promoted higher shear bond strength, regardless of the bleaching treatment and allowed the formation of a regular and fine hybrid layer with less deep tags, when compared to Single Bond and Clearfil. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

A HYDROGEN PEROXIDE SENSOR BASED ON PRUSSIAN BLUE AND DNA-MODIFIED ELECTRODE

The polyvinylpyrrolidone (PVP) protected Prussian blue (PB) nanoparticles were prepared for use as a sensor for the catalytic reduction of hydrogen peroxide. The nanoparticles were used to modify a gold electrode, which was applied to detect hydrogen peroxide. Impedance spectra and differential pulse voltammetry were applied to detect the performance of the novel electrode and its response to H₂O₂ and Ramos cell smash fluid. Under the optimized experimental conditions, hydrogen peroxide was detected in a linear range of 6.25 × 10^?7 to 1.0 × 10^?5 mol · L^?1, and the detection limit was 7.12 × 10^?8 mol · L^?1 according to 3σ rule. Under the same conditions, hydrogen peroxide was determined in Ramos cell smash fluid with a linear range from 400–80000 mol mL^?1, with a detection limit of 114 mL^?1 according to 3σ rule. The modified electrode with Prussian blue nanoparticles displayed high sensitivity, good reproducibility, and long-term stability to hydrogen peroxide.     

Effects of prolonged use of over-the-counter bleaching agents on enamel: An in vitro study

This study evaluated the effects of four over-the-counter (OTC) bleaching products on the properties of enamel. Extracted human molars were randomly assigned into four groups (n = 5): PD: Poladay (SDI), WG: White Teeth Global (White Teeth Global), CW: Crest3DWhite (Procter & Gamble), and HS: HiSmile (HiSmile). The hydrogen peroxide (H₂O₂) content in each product was analyzed via titration. Twenty teeth were sectioned into quarters, embedded in epoxy resin, and polished. Each quarter-tooth surface was treated with one of the four beaching times: T0: control/no-bleaching, T14: 14 days, T28: 28 days, and T56: 56 days. Materials were applied to enamel surfaces as recommended. Enamel surfaces were examined for ultramicrohardness (UMH), elastic modulus (EM), superficial roughness (Sa), and scanning electron microscopy (SEM). Ten additional teeth were used to evaluate color and degree of demineralization (DD) (n = 5). Data were statistically tested by two-way ANOVA and Tukey's tests (α = 5%). Enamel surfaces treated with PD and WG presented UMH values significantly lower than the controls (p < .05). Elastic modulus (E) was significantly reduced at T14 and T28 for PD, and at T14 for HS (p < .05). A significant increase in Sa was observed for CW at T14 (p < .05). Color changes were observed in the PD and WG groups. Additionally, DD analysis showed significant demineralization at T56 for CW. Overall, more evident morphological alterations were observed for bleaching products with higher concentrations of H₂O₂ (p < .05), PD, and WG. Over-the-counter bleaching products containing H₂O₂ can significantly alter enamel properties, especially when application time is extended.     

H2O2/H2SO4法溶解不锈钢铜包套的新方法

介绍了一种用Ｈ２Ｏ２／Ｈ２ＳＯ４溶解不锈钢铜包套的新方法，对温度、稳定剂以及各种原料的浓度等影响因素进行了讨论。传统方法大多以硝酸为主要成颁溶解过程中放出有毒的ＮＯＸ，严重污染环境。本方法无此弊端，对保护环境具有重要意义。     

Study on tribological and electrochemistry properties of metal materials in H2O2 solutions

Hydrogen peroxide (H₂O₂) is a kind of ideal green propellant. It is crucial to study the wear behavior and failure modes of the metal materials under the strong oxidizing environment of H₂O₂. This study aims to investigate the wear of rubbing pairs of 2Cr13 stainless steel against 1045 metal in H₂O₂ solutions, which has a great effect on wear, the decomposition and damage mechanism of materials. The comparison analysis of the friction coefficients, wear mass loss, worn surface topographies and current densities was conducted under different concentrations of H₂O₂ solutions. There were significant differences in the tribological and electrochemistry properties of the rubbing pairs in different H₂O₂ solutions.     

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 in‐office bleaching with 35% hydrogen peroxide with and without addition of calcium on the enamel surface

This study aimed to evaluate effectiveness and effects of bleaching with 35% hydrogen peroxide with and without calcium on color, micromorphology, and the replacement of calcium and phosphate on the enamel surface. Thirty bovine enamel blocks (5.0 × 5.0 mm) were placed into the following groups: G1: artificial saliva (control); G2: 35% hydrogen peroxide gel without calcium (Whiteness HP Maxx–FGM); and G3: 35% hydrogen peroxide gel with calcium (Whiteness HP Blue–FGM). Three color measurements were performed with a spectrophotometer: untreated (baseline), after performing staining, and after application of bleaching agents. Calcium deposition on the enamel was evaluated before and after the application of bleaching agents using energy‐dispersive X‐ray spectrometry. The enamel surface micromorphology was observed under scanning electron microscopy. The pH of each product was measured. The data were subjected to one‐factor analysis of variance (ANOVA), and any differences were analyzed using Tukey's test (P < 0.05). G3 showed greater variation in total color after the experiment than G2 and G1; there was no significant difference in calcium or phosphorus concentration before and after the experimental procedures; morphological changes were observed only in G2 and G3; and the pH values of the Whiteness HP Maxx and Whiteness HP Blue bleaching agents were 5.77 and 7.79, respectively. The 35% hydrogen peroxide with calcium showed greater bleaching potential, but the addition of calcium had no effect in terms of reducing morphological changes or increasing the calcium concentration on the enamel surface. Microsc. Res. Tech. 78:975–981, 2015. © 2015 Wiley Periodicals, Inc.     

Hydrogen peroxide staining to visualize intracellular bacterial infections of seedling root cells

Visualization of bacteria in living plant cells and tissues is often problematic due to lack of stains that pass through living plant cell membranes and selectively stain bacterial cells. In this article, we report the use of 3,3′‐diaminobenzidine tetrachloride (DAB) to stain hydrogen peroxide associated with bacterial invasion of eukaryotic cells. Tissues were counterstained with aniline blue/lactophenol to stain protein in bacterial cells. Using this staining method to visualize intracellular bacterial (Burkholderia gladioli) colonization of seedling roots of switch grass (Panicum virgatum), we compared bacterial free seedling roots and those inoculated with the bacterium. To further assess application of the technique in multiple species of vascular plants, we examined vascular plants for seedling root colonization by naturally occurring seed‐transmitted bacteria. Colonization by bacteria was only observed to occur within epidermal (including root hairs) and cortical cells of root tissues, suggesting that bacteria may not be penetrating deeply into root tissues. DAB/peroxidase with counter stain aniline blue/lactophenol was effective in penetration of root cells to selectively stain bacteria. Furthermore, this stain combination permitted the visualization of the bacterial lysis process. Before any evidence of H₂O₂ staining, intracellular bacteria were seen to stain blue for protein content with aniline blue/lactophenol. After H₂O₂ staining became evident, bacteria were often swollen, without internal staining by aniline blue/lactophenol; this suggests loss of protein content. This staining method was effective for seedling root tissues; however, it was not effective at staining bacteria in shoot tissues due to poor penetration. Microsc. Res. Tech. 77:566–573, 2014. © 2014 Wiley Periodicals, Inc.     

毛细管气相色谱法检测面粉中的过氧化苯甲酰和山梨酸

过氧化苯甲酰和山梨酸是在面粉中常用的添加剂。本文采用毛细管气相色谱法检测面粉中的过氧化本甲酰,方法准确、快速。     

Kinetic Spectrophotometric Determination of Traces of Iron by its Catalytic Effect on the Oxidation of m-Acetylchlorophosphonazo by Hydrogen Peroxide

Abstract

In the buffer medium of KHC₈H₄O₄–HCl at pH 3.2, a catalytic kinetic spectrophotometric method for the determination of iron was developed by use of the catalytic effect of iron(III) on the oxidation of m-acetylchlorophosphonazo by hydrogen peroxide. At the wavelength of 544 nm, the difference of absorbance(?A) is well linearly related with the concentration of iron(III) in the range of 0–2.5 µg/25 mL and fitted the equation: ?A = 0.1469 C(µg/25 mL) + 0.0037, with a regression coefficient of 0.9979.The detection limit of the method is 1.34 ng/mL. The present method was successfully applied to determine iron in rice samples.     

过氧化苯甲酰对偶氮二甲酰胺在硅橡胶中发泡行为的影响

以偶氮二甲酰胺(AC)为发泡剂、尿素为发泡助剂、过氧化苯甲酰(BPO)为硫化剂,通过化学发泡方法制备了硅橡胶泡沫材料;使用发泡流变仪研究了发泡剂AC在硅橡胶中的发泡性能,使用SEM、电子万能材料试验机分析了泡沫材料的泡孔结构和拉伸性能。结果表明:在一定温度下,发泡速率与硫化速率可较好地匹配,得到不同泡孔结构的硅橡胶泡沫材料;增加发泡剂AC用量,可提高胶料的发泡率,当其用量为8份时(100份硅橡胶),泡沫材料具有较好的拉伸性能。     

MRT letter: Localization of endogenous hydrogen peroxide by modified processes of sample preparation for transmissionelectron microscope in Escherichia coli

The bacterial endogenous hydrogen peroxide (H₂O₂) was detected cytochemically by its reaction with cerium chloride (CeCl₃) to produce electron‐dense deposits of cerium perhydroxides. The sequence of fixation and CeCl₃ staining of H₂O₂ in the processing of transmission electron microscope (TEM) sample preparation is crucial to the localization of endogenous H₂O₂ in Escherichia coli. In this study, results confirmed that the process that fixation simultaneously with CeCl₃ staining provided optimum effects for H₂O₂ localization in E. coli. The modified process of TEM provides very efficient protection for H₂O₂ localization and more accurate quantization for the H₂O₂ accumulation in bacterial cells. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.     

Effect of in‐office bleaching agents on the surface roughness and morphology of different dental composites: An AFM study

The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modification will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek? Z350 composites were used. Atomic force microscopy was used for analyses of the same place of the sample before and after treatment. A total of 12 analyses were performed per group (n = 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were analyzed statistically using Kruskal–Wallis, Mann–Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the surface of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them. Microsc. Res. Tech. 76:481–485, 2013. © 2013 Wiley Periodicals, Inc.