Can an LED-laser hybrid light help to decrease hydrogen peroxide concentration while maintaining effectiveness in teeth bleaching?

The aim of this study was to compare the bleaching efficacy of 35% hydrogen peroxide and 15% hydrogen peroxide with nitrogen-doped titanium dioxide catalysed by an LED-laser hybrid light. We studied 70 patients randomized to two groups. Tooth shade and pulpal sensitivity were registered. Group 1: 15% hydrogen peroxide with nitrogen-doped titanium dioxide. Group 2: 35% hydrogen peroxide. Both groups were activated by an LED-laser light. No significant differences were seen in shade change immediately, one week or one month after treatment (p > 0.05). Differences were seen in pulpal sensitivity (p < 0.05). The use of an LED-laser hybrid light to activate 15% hydrogen peroxide gel with N_TiO2 permits decreasing the peroxide concentration with similar aesthetic results and less pulpal sensitivity than using 35% hydrogen peroxide for bleaching teeth.

Demineralization and hydrogen peroxide penetration in teeth with incipient lesions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hydrogen peroxide centrally attenuates hyperosmolarity-induced thirst and natriuresis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dental bleaching with a 10% hydrogen peroxide product: a six-month clinical observation

Context: The possibility of bleaching vital teeth with peroxide-based products considerably revolutionized esthetic dentistry. Aim: The aim of this clinical study was to evaluate tooth color change and dental sensitivity after exposure to preloaded film containing a 10% hydrogen peroxide whitening system (Opalescence Trθswhite Supreme). Materials and Methods: A total of 13 volunteers, aged 18 to 25 years, participated in this study. The patients used the whitening system once a day for 60 minutes during the 8-day study. For maxillary incisors and canines, the color change was visually evaluated with the Vita color scale before, immediately, and six months after the treatment. Tooth sensitivity was evaluated during the daily gel applications. All whitening applications were done in office and under the supervision of a dental professional. Statistical Analysis Used: The results were analyzed using the Friedman Test (nonparametric repeated measures ANOVA) at a level of 5%, and Dunn's Multiple Comparison Test at the level of 5%. Results: It was verified that the original mean color values observed at the baseline analysis differed significantly from those observed immediately after bleaching, as well as from those seen in the analysis at six months ( P = 0.001). There was no significant difference between the mean color values observed in the immediate time and in the analysis at six months ( P = 0.474). No tooth sensitivity was observed in any patients. Conclusion: It was concluded that the bleaching technique using the 10% hydrogen peroxide system was effective in a short period of time without tooth sensitivity during applications.

Baccharin Prevents Genotoxic Effects Induced by Methyl Methanesulfonate and Hydrogen Peroxide in V79 Cells

Baccharin is one of the major chemical compounds isolated from the aerial parts of Baccharis dracunculifolia DC (Asteraceae), a native plant of South America and the most important botanical source of the Brazilian green propolis that has been used in alternative medicine to treat inflammation, liver disorders, and stomach ulcers. The present study was carried out in V79 cells to determine the possible genotoxic and antigenotoxic activities of baccharin utilizing comet and micronucleus assays, where 2 known mutagenic agents with different mechanisms of DNA damage were used as positive controls. The V79 cells were treated with concentrations of baccharin (0.25, 0.5, 1.0, and 2.0 mu g/mL) and for to investigate the antigenotoxicity these concentrations were associated with methyl methanesulfonate (MMS; 200 mu M-comet assay and 400 mu M-micronucleus assay) or hydrogen peroxide (H2O2; 50 mu M-comet assay and 100 mu M-micronucleus assay). Statistically significant differences in the rate of DNA damage were observed in cultures treated with the highest concentration of baccharin when compared to the control group, but this difference was not found in the micronucleus assay. The results also showed that the frequencies of DNA damage and micronuclei induced by MMS and H2O2 were significantly reduced after treatment with baccharin. The baccharin showed a chemoprevention effect and can be the chemical compound responsible for the antigenotoxicity also demonstrated by the B. dracunculifolia. The antioxidant potential of baccharin may be related to its chemoprevention activity induced against both genomic and chromosomal damages.

Enamel Surface Changes After Exposure to Bleaching Gels Containing Carbamide Peroxide or Hydrogen Peroxide.

OBJECTIVE This study evaluated the differences in enamel color change, surface hardness, elastic modulus, and surface roughness between treatments with four bleaching gels containing carbamide peroxide (two at 10% and one each at 35%, and 45%) and two bleaching gels containing hydrogen peroxide (two at 40%). METHODS Enamel specimens were bleached and color changes were measured. Color change was calculated using either ΔE or the Bleaching Index (BI). Then, surface hardness, elastic modulus, and surface roughness of the enamel specimens were evaluated. All measurements were performed at baseline and directly after the first bleaching treatment for all carbamide peroxide- and hydrogen peroxide-containing bleaching gels. In addition, final measurements were made 24 hours after each of a total of 10 bleaching treatments for carbamide peroxide bleaching gels, and 1 week after each of a total of three bleaching treatments for hydrogen peroxide bleaching gels. RESULTS After the last bleaching treatment, respective ΔE scores were 17.6 and 8.2 for the two 10% carbamide peroxide gels, 12.9 and 5.6 for the 45% and 35% carbamide peroxide gels, and 9.6 and 13.9 for the two 40% hydrogen peroxide gels. The respective BI scores were -2.0 and -2.0 for the two 10% carbamide peroxide gels, -3.5 and -1.5 for the 45% and 35% carbamide peroxide gels, and -2.0 and -3.0 for the two 40% hydrogen peroxide gels. Each bleaching gel treatment resulted in significant whitening; however, no significant difference was found among the gels after the last bleaching. Whitening occurred within the first bleaching treatments and did not increase significantly during the remaining treatments. Surface hardness significantly decreased after the last bleaching treatment, when 10% carbamide peroxide was used. Furthermore, significant changes in the elastic modulus or surface roughness occurred only after treatment with 10% carbamide peroxide. CONCLUSION All six bleaching gels effectively bleached the enamel specimens independent of their concentration of peroxide. Gels with low peroxide concentration and longer contact time negatively affected the enamel surface.

Iron and aluminium and hydrogen peroxide measured on water bottle samples during Marion Dufresne cruise ANTARES-II

Total dissolvable iron (TDFe), particulate iron (PFe) and hydrogen peroxide (H2O2 measurements were performed along a N-S transect in the upper 250 m in the Southern Ocean (62°00E/66°42S - 49°00S, ANTARES II cruise, February 1994). TDFe was organically extracted (APDC/DDDC-chloroform) and analysed by Graphite Furnace Atomic Absorption Spectrometry (GFAAS), PFe was analysed by GFAAS following a strong mixed-acid leach, and H2O2 was analysed on board by fluorometry. The respective detection limits are equal to 0.13 nmol/kg, 0.02 nmol/kg, and 3.0 nmol/kg. TDFe concentrations vary from 0.4 to 6.2 nmol/kg and profiles are not completely depleted in the surface. PFe concentrations vary from 0.02 to 0.2 nmol/kg. Iron/carbon (Fe/C) uptake ratios for phytoplankton were calculated either from seawater or particle measurements. They are variable along the transect but are consistent when they could be compared. All the observed ratios are within the range of values proposed for the Fe/C uptake ratios by phytoplankton. Using our uptake ratio calculated in the Permanent Open Ocean Zone (4 x 10**?6 mol/mol), we estimate that the primary production which can be supported by the iron input flux into the surface waters is two times higher than the measured primary production in the same area. In the surface waters, H2O2 concentrations vary from 5.0 to 19.7 nmol/kg. Such low concentrations are due to strong vertical mixing, low dissolved organic matter concentrations and the latitude of the site.

NADPH-oxidase and a hydrogen peroxide-sensitive K+ channel may function as an oxygen sensor complex in airway chemoreceptors and small cell lung carcinoma cell lines

Pulmonary neuroepithelial bodies (NEB) are widely distributed throughout the airway mucosa of human and animal lungs. Based on the observation that NEB cells have a candidate oxygen sensor enzyme complex (NADPH oxidase) and an oxygen-sensitive K+ current, it has been suggested that NEB may function as airway chemoreceptors. Here we report that mRNAs for both the hydrogen peroxide sensitive voltage gated potassium channel subunit (KH2O2) KV3.3a and membrane components of NADPH oxidase (gp91phox and p22phox) are coexpressed in the NEB cells of fetal rabbit and neonatal human lungs. Using a microfluorometry and dihydrorhodamine 123 as a probe to assess H2O2 generation, NEB cells exhibited oxidase activity under basal conditions. The oxidase in NEB cells was significantly stimulated by exposure to phorbol esther (0.1 μM) and inhibited by diphenyliodonium (5 μM). Studies using whole-cell voltage clamp showed that the K+ current of cultured fetal rabbit NEB cells exhibited inactivating properties similar to KV3.3a transcripts expressed in Xenopus oocyte model. Exposure of NEB cells to hydrogen peroxide (H2O2, the dismuted by-product of the oxidase) under normoxia resulted in an increase of the outward K+ current indicating that H2O2 could be the transmitter modulating the O2-sensitive K+ channel. Expressed mRNAs or orresponding protein products for the NADPH oxidase membrane cytochrome b as well as mRNA encoding KV3.3a were identified in small cell lung carcinoma cell lines. The studies presented here provide strong evidence for an oxidase-O2 sensitive potassium channel molecular complex operating as an O2 sensor in NEB cells, which function as chemoreceptors in airways and in NEB related tumors. Such a complex may represent an evolutionary conserved biochemical link for a membrane bound O2-signaling mechanism proposed for other cells and life forms.

Hydrogen peroxide is generated systemically in plant leaves by wounding and systemin via the octadecanoid pathway

Hydrogen peroxide (H2O2) generated in response to wounding can be detected at wound sites and in distal leaf veins within 1 hr after wounding. The response is systemic and maximizes at about 4–6 hr in both wounded and unwounded leaves, and then declines. The timing of the response corresponds with an increase in wound-inducible polygalacturonase (PG) mRNA and enzyme activity previously reported, suggesting that oligogalacturonic acid (OGA) fragments produced by PG are triggering the H2O2 response. Systemin, OGA, chitosan, and methyl jasmonate (MJ) all induce the accumulation of H2O2 in leaves. Tomato plants transformed with an antisense prosystemin gene produce neither PG activity or H2O2 in leaves in response to wounding, implicating systemin as a primary wound signal. The antisense plants do produce both PG activity and H2O2 when supplied with systemin, OGA, chitosan, or MJ. A mutant tomato line compromised in the octadecanoid pathway does not exhibit PG activity or H2O2 in response to wounding, systemin, OGA, or chitosan, but does respond to MJ, indicating that the generation of H2O2 requires a functional octadecanoid signaling pathway. Among 18 plant species from six families that were assayed for wound-inducible PG activity and H2O2 generation, 14 species exhibited both wound-inducible PG activity and the generation of H2O2. Four species, all from the Fabaceae family, exhibited little or no wound-inducible PG activity and did not generate H2O2. The time course of wound-inducible PG activity and H2O2 in Arabidopsis thaliana leaves was similar to that found in tomato. The cumulative data suggest that systemic wound signals that induce PG activity and H2O2 are widespread in the plant kingdom and that the response may be associated with the defense of plants against both herbivores and pathogens.

Hypersensitive Cell Death and Papilla Formation in Barley Attacked by the Powdery Mildew Fungus Are Associated with Hydrogen Peroxide but Not with Salicylic Acid Accumulation1

We analyzed the pathogenesis-related generation of H2O2 using the microscopic detection of 3,3-diaminobenzidine polymerization in near-isogenic barley (Hordeum vulgare L.) lines carrying different powdery mildew (Blumeria graminis f.sp. hordei) resistance genes, and in a line expressing chemically activated resistance after treatment with 2,6-dichloroisonicotinic acid (DCINA). Hypersensitive cell death in Mla12 and Mlg genotypes or after chemical activation by DCINA was associated with H2O2 accumulation throughout attacked cells. Formation of cell wall appositions (papillae) mediated in Mlg and mlo5 genotypes and in DCINA-activated plants was paralleled by H2O2 accumulation in effective papillae and in cytosolic vesicles of up to 2 μm in diameter near the papillae. H2O2 was not detected in ineffective papillae of cells that had been successfully penetrated by the fungus. These findings support the hypothesis that H2O2 may play a substantial role in plant defense against the powdery mildew fungus. We did not detect any accumulation of salicylic acid in primary leaves after inoculation of the different barley genotypes, indicating that these defense responses neither relied on nor provoked salicylic acid accumulation in barley.

Hydrogen peroxide mediates the cell growth and transformation caused by the mitogenic oxidase Nox1

Nox1, a homologue of gp91phox, the catalytic moiety of the superoxide (O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document})-generating NADPH oxidase of phagocytes, causes increased O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document} generation, increased mitotic rate, cell transformation, and tumorigenicity when expressed in NIH 3T3 fibroblasts. This study explores the role of reactive oxygen species (ROS) in regulating cell growth and transformation by Nox1. H2O2 concentration increased ≈10-fold in Nox1-expressing cells, compared with <2-fold increase in O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document}. When human catalase was expressed in Nox1-expressing cells, H2O2 concentration decreased, and the cells reverted to a normal appearance, the growth rate normalized, and cells no longer produced tumors in athymic mice. A large number of genes, including many related to cell cycle, growth, and cancer (but unrelated to oxidative stress), were expressed in Nox1-expressing cells, and more than 60% of these returned to normal levels on coexpression of catalase. Thus, H2O2 in low concentrations functions as an intracellular signal that triggers a genetic program related to cell growth.

Endogenous intracellular glutathionyl radicals are generated in neuroblastoma cells under hydrogen peroxide oxidative stress.

We report the detection of endogenous intracellular glutathionyl (GS.) radicals in the intact neuroblastoma cell line NCB-20 under oxidative stress. Spin-trapping and electron paramagnetic resonance (EPR) spectroscopic methods were used for monitoring the radicals. The cells incubated with the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) were challenged with H2O2 generated by the enzymic reaction of glucose/glucose oxidase. These cells exhibit the EPR spectrum of the GS. radical adduct of DMPO (DMPO-.SG) without exogenous reduced glutathione (GSH). The identity of this radical adduct was confirmed by observing hyperfine coupling constants identical to previously reported values in in vitro studies, which utilized known enzymic reactions, such as horseradish peroxidase and Cu/Zn superoxide dismutase, with GSH and H2O2 as substrates. The formation of the GS. radicals required viable cells and continuous biosynthesis of GSH. No significant effect on the resonance amplitude by the addition of a membrane-impermeable paramagnetic broadening agent indicated that these radicals were located inside the intact cell. N-Acetyl-L-cysteine (NAC)-treated cells produced NAC-derived free radicals (NAC.) in place of GS. radicals. The time course studies showed that DMPO-.SG formation exhibited a large increase in its concentration after a lag period, whereas DMPO-NAC. formation from NAC-treated cells did not show this sudden increase. These results were discussed in terms of the limit of antioxidant enzyme defenses in cells and the potential role of the GS. radical burst in activation of the transcription nuclear factor NF-kappa B in response to oxidative stress.

Gas turbines and jet propulsion, including rocket, hydrogen peroxide, and nuclear power plants: theory and application.

"Portions of this book first published [by the Dept. of Marine Engineering, U. S. Naval Academy] as a part of Combustion engines manual and...of Internal combustion engines."

A copper-hydrogen peroxide redox system induces dityrosine cross-links and chemokine oligomerisation

The activity of the chemoattractant cytokines, the chemokines, in vivo is enhanced by oligomerisation and aggregation on glycosaminoglycan (GAG), particularly heparan sulphate, side chains of proteoglycans. The chemokine RANTES (CCL5) is a T-lymphocyte and monocyte chemoattractant, which has a minimum tetrameric structure for in vivo activity and a propensity to form higher order oligomers. RANTES is unusual among the chemokines in having five tyrosine residues, an amino acid susceptible to oxidative cross-linking. Using fluorescence emission spectroscopy, Western blot analysis and LCMS-MS, we show that a copper/H2O2 redox system induces the formation of covalent dityrosine cross-links and RANTES oligomerisation with the formation of tetramers, as well as higher order oligomers. Amongst the transition metals tested, namely copper, nickel, mercury, iron and zinc, copper appeared unique in this respect. At high (400 µM) concentrations of H2O2, RANTES monomers, dimers and oligomers are destroyed, but heparan sulphate protects the chemokine from oxidative damage, promoting dityrosine cross-links and multimer formation under oxidative conditions. Low levels of dityrosine cross-links were detected in copper/H2O2-treated IL-8 (CXCL8), which has one tyrosine residue, and none were detected in ENA-78 (CXCL5), which has none. Redox-treated RANTES was fully functional in Boyden chamber assays of T-cell migration and receptor usage on activated T-cells following RANTES oligomerisation was not altered. Our results point to a protective, anti-oxidant, role for heparan sulphate and a previously unrecognised role for copper in chemokine oligomerisation that may offer an explanation for the known anti-inflammatory effect of copper-chelators such as penicillamine and tobramycin.