Low Concentrations Of Hydrogen Peroxide Research Articles

24-Epibrassinolide Mechanisms Regulating Blossom-End Rot Development in Tomato Fruit

Blossom-end rot (BER) is a physiological disorder believed to be triggered by low Ca2+ content in the distal fruit tissue. However, many other factors can also determine fruit susceptibility to BER. It is possible that during fruit growth, Ca2+ imbalance can increase membrane leakiness, which may trigger the accumulation of reactive oxygen species, leading to cell death. Brassinosteroids are a class of plant hormones involved in stress defenses, specially increasing the activity of antioxidant enzymes and the accumulation of antioxidant compounds, such as ascorbic acid. The objective of this study was to understand the mechanisms by which 24-epibrassinolide (EBL) reduces fruit susceptibility to BER. Tomato plants ‘BRS Montese’ were cultivated in a greenhouse and were weekly sprayed with water (control) or EBL (0.01 µM) after full bloom. Plants and fruits were evaluated at 15 days after pollination (DAP). According to the results, EBL treatment inhibited BER development, increased fruit diameter, length, and fresh weight. EBL-treated fruit showed higher concentrations of soluble Ca2+ and lower concentrations of cell wall-bound Ca2+. EBL-treated fruit also had higher concentrations of ascorbic acid and lower concentrations of hydrogen peroxide, compared to water-treated fruit. EBL treatment increased the activity of the three main antioxidant enzymes known as ascorbate peroxidase, catalase, and superoxide dismutase. According to the results, EBL treatment maintained higher soluble Ca2+ and antioxidant capacity, reducing fruit susceptibility to BER.

Galactomannan-carnauba wax coating improves the antioxidant status and reduces chilling injury of ‘Paluma’ guava

Physiologically mature ‘Paluma’ guava were treated with galactomannan (0.75%) and carnauba wax (0.9%) coating, stored at ambient (25 °C) and refrigerated (11 °C), and evaluated every 3rd day for postharvest quality and physiology. Ambient uncoated fruit were apt for consumption for only nine days; meanwhile, coated guavas were acceptable for 15 d with climacteric respiratory peak of 168.6 mg kg−1 h-1 at day 12, and firmness of 14.3 N attributed to lower lipid peroxidation and cell wall hydrolysis. Coating increased antioxidant enzymes SOD and CAT activities that led to 35% lower hydrogen peroxide content, when compared to uncoated control. Coating prevented guava degreening by inhibiting chlorophyll degradation with content of 45.05 mg kg-1, lower carotenoid content with 27.8 mg kg-1 and PPO activity, under refrigeration for 15 d. Refrigerated uncoated fruit exhibited as symptoms of chilling injury inhibition of softening and respiratory peak. Principal component analysis showed that coating and refrigeration treatment maintains guava quality for 15 d of storage similar to observed for control, at day zero. In conclusion, galactomannan-carnauba wax coating improved guava postharvest quality through maintenance of firmness and color, besides preventing chilling symptoms under refrigeration.

Deletion of GLX3 in Candida albicans affects temperature tolerance, biofilm formation and virulence.

Candida albicans is a predominant cause of fungal infections in mucosal tissues as well as life-threatening bloodstream infections in immunocompromised patients. Within the human body, C. albicans is mostly embedded in biofilms, which provides increased resistance to antifungal drugs. The glyoxalase Glx3 is an abundant proteomic component of the biofilm extracellular matrix. Here, we document phenotypic studies of a glx3Δ null mutant concerning its role in biofilm formation, filamentation, antifungal drug resistance, cell wall integrity and virulence. First, consistent with its function as glyoxalase, the glx3 null mutant showed impaired growth on media containing glycerol as the carbon source and in the presence of low concentrations of hydrogen peroxide. Importantly, the glx3Δ mutant showed decreased fitness at 37°C and formed less biofilm as compared to wild type and a reintegrant strain. At the permissive temperature of 28°C, the glx3Δ mutant showed impaired filamentation as well as increased sensitivity to Calcofluor white, Congo red, sodium dodecyl sulfate and zymolyase, indicating subtle alterations in wall architecture even though gross quantitative compositional changes were not detected. Interestingly, and consistent with its impaired filamentation, biofilm formation and growth at 37°C, the glx3Δ mutant is avirulent. Our results underline the role of Glx3 in fungal pathogenesis and the involvement of the fungal wall in this process.

DksA–DnaJ redox interactions provide a signal for the activation of bacterial RNA polymerase

RNA polymerase is the only known protein partner of the transcriptional regulator DksA. Herein, we demonstrate that the chaperone DnaJ establishes direct, redox-based interactions with oxidized DksA. Cysteine residues in the zinc finger of DksA become oxidized in Salmonella exposed to low concentrations of hydrogen peroxide (H2O2). The resulting disulfide bonds unfold the globular domain of DksA, signaling high-affinity interaction of the C-terminal α-helix to DnaJ. Oxidoreductase and chaperone activities of DnaJ reduce the disulfide bonds of its client and promote productive interactions between DksA and RNA polymerase. Simultaneously, guanosine tetraphosphate (ppGpp), which is synthesized by RelA in response to low concentrations of H2O2, binds at site 2 formed at the interface of DksA and RNA polymerase and synergizes with the DksA/DnaJ redox couple, thus activating the transcription of genes involved in amino acid biosynthesis and transport. However, the high concentrations of ppGpp produced by Salmonella experiencing oxidative stress oppose DksA/DnaJ-dependent transcription. Cumulatively, the interplay of DksA, DnaJ, and ppGpp on RNA polymerase protects Salmonella from the antimicrobial activity of the NADPH phagocyte oxidase. Our research has identified redox-based signaling that activates the transcriptional activity of the RNA polymerase regulator DksA.

Impedimetric mechanism study of horseradish peroxidase at low and high concentrations of hydrogen peroxide based on graphene/sol-gel/horseradish peroxidase

A novel electrochemical modified electrode for the impedimetric mechanism study of horseradish peroxidase and hydrogen peroxide was proposed based on immobilizing horseradish peroxidase/3‑(trimethoxysilyl) propylamine/graphene on glassy carbon electrode (HRP/TMSPA/Gr/GCE). Cyclic voltammetry and SEM were utilized to corroborate the successful stepwise assemblage procedure of the electrode. The electrochemical impedance spectroscopy measurements revealed that the charge transfer resistance increases at low concentrations and significantly decreases at high concentrations after enzymatic reaction with hydrogen peroxide. The mechanism study of the horseradish peroxidase and hydrogen peroxide were also investigated by electrochemical impedance spectroscopy.

Oxidants-Antioxidants Profile in the Breast Cancer Cell Line MCF-7

Reactive oxygen species (ROS) have various biological effects and they are non-linear in characteristic. In high oxidative stress, they may cause cytotoxicity, inhibit cell proliferation, and induce cell death in the form of apoptosis/necrosis; while in low or medium oxidative stress, ROS may cause DNA damage, cell mutation, inflammation, cell proliferation, and eventually they may induce carcinogenesis. Antioxidants are compounds with the ability to reduce ROS. Cell line MCF-7 is one of the breast cancer cell lines that is known to have small amount of antioxidant MnSOD compared to the other cell lines. Low antioxidant MnSOD level in breast cancer cell line MCF-7 leads to low concentration of hydrogen peroxide, because antioxidant MnSOD will convert radical superoxide to hydrogen peroxide. The aim of this research was to analyze oxidants and antioxidants profile in breast cancer cell line MCF-7 and their relationship with cell number. Observations were conducted for 5 days. The cell number was counted with tryphan blue method and haematometer. The concentration of radical superoxide was measured with DHE staining using LSCM tipe Olympus Fluoview FV 1000-Ver 1.7. MnSOD activity, hydrogen peroxide concentration, and catalase activity were measured with ELISA. The results showed that the longer of observation, the greater concentration of oxidants and MnSOD activity, but there was no change in catalase activity. Conclusion the increase in cancer cells number is influenced by radical superoxide.

An injectable platelet lysate-hyaluronic acid hydrogel supports cellular activities and induces chondrogenesis of encapsulated mesenchymal stem cells

Developing scaffolds that can provide cells and biological cues simultaneously in the defect site is of interest in tissue engineering field. In this study, platelet lysate (PL) as an autologous and inexpensive source of growth factors was incorporated into a cell-laden injectable hyaluronic acid-tyramine (HA-TA) hydrogel. Subsequently, the effect of platelet lysate on cell attachment, viability and differentiation of human mesenchymal stem cell (hMSCs) toward chondrocytes was investigated. HA-TA conjugates having a degree of substitution of 20 TA moieties per 100 disaccharide units were prepared and crosslinked in the presence of horseradish peroxidase and low concentrations of hydrogen peroxide. The storage moduli of the gels ranged from 500 to 2000 Pa and increased with increasing polymer concentration. In contrast to a retained round shape of the cells when using pure HA-TA hydrogel, the hMSCs attached and spread out in PL enriched matrix. The enrichment of hMSCs laden HA-TA hydrogels with PL induced a cartilage like extra cellular matrix deposition in vitro. The hMSCs increasingly deposited collagen type II and proteoglycans over time. The deposition of the new extracellular matrix (ECM) is simultaneous with gel degradation and resulted ultimately in the formation of a tough dense matrix. These findings demonstrate the potential of injectable HA-TA-PL hydrogel as a cell delivery system for cartilage regeneration. Statement of SignificanceCartilage tissue has limited ability to self-repair because of its avascular nature. To have an efficient cartilage tissue regeneration, we combined platelet lysate (PL), as an autologous and inexpensive source of growth factors, with an injectable hyaluronic acid tyramine (HA-TA) hydrogel scaffold. Platelet lysate had a vital role in supporting human mesenchymal stem cells (hMSCs) activities, like cell attachment, viability and proliferation in the 3D hydrogel structure. Also, the hMSCs encapsulated HA-TA induced hyaline cartilage generation when placed in chondrogenic differentiation medium. This study introduces a new system for cartilage tissue engineering, which can be injected in a minimally invasive manner and is rich with patient’s own growth factors and biological cues.

Intentional Ingestion of Hydrogen Peroxide

Introduction: Hydrogen peroxide poisoning can cause death. The chemical reactions in the body will produce complications, such as stroke, perforation of the gut, and embolism. These complications are most likely seen with high concentrations. Case Presentation: The patient was a 55-year-old female, who tried to commit suicide by ingestion of approximately 150 cc of hydrogen peroxide. She was brought to the emergency room for medical treatment. During the physical examination, the patient had air in the neck and mediastinum, which is a strong indication of acute mediastinitis. The patient was treated with esophagectomy and feeding jejunostomy. The pathology reported first degree burns of the esophagus without perforation. The patient underwent reconstructive surgery and treatment for eight weeks, yet she died during surgery as a result of low ejection fraction (EF). Conclusions: In this case, the patient intentionally ingested a low concentration (15%) of hydrogen peroxide and as a result experienced first degree burns in the esophagus. The patient did not require surgery for treatment. The presence of white mucus and air around the esophagus and stomach was thought to be indicative of acute mediastinitis and mistakenly exposed the patient to major surgery.

Oxidation of Dibenzothiophene in Diesel with In Situ Produced Hydrogen Peroxide

A new in situ oxidation technology is studied for desulfurization of diesel fuel in a divided-cell trickle bed electrochemical reactor (TBER). In this process, a strong and green oxidizing agent, hydrogen peroxide, is electrogenerated by cathodic oxygen reduction and employed in situ for the oxidation of dibenzothiophene (DBT) in diesel. The cathode in the TBER is made of carbon black and polytetrafluoroethylene particles, giving rise to a highly porous electrode. A maximum concentration of hydrogen peroxide after 2 h electrolysis was obtained at 31.8 mM using potassium hydroxide as electrolyte at constant voltages. A much lower hydrogen peroxide concentration at 18.0 mM was observed under the same conditions but with 10% diesel by volume in the electrolytes. This was attributed to less available electrode areas as well as active sites for oxygen reduction reactions as a result of the presence of the oil diesel phase. Despite this reduction in hydrogen peroxide generation, the DBT in diesel was successful...

SIRT1 reverses senescence via enhancing autophagy and attenuates oxidative stress-induced apoptosis through promoting p53 degradation

Stem cell senescence and exhaustion are considered important drivers of organismal aging, and human adipose-derived stem cells (ADSCs) have emerged as a promising cell source for cell-based therapy. However, aging and low survival rate compromise the optimal outcome of cell-based therapy due to oxidative stress in the graft areas. Oxidative stress has long been considered to be harmful to cells, nevertheless, in this study, we found that lower concentration of hydrogen peroxide (H2O2) decreased the number of SA-βgal-immunopositive cells, which was ameliorated by inhibition of SIRT1. Autophagy, a degradation mechanism that plays a major role in maintaining cellular homeostasis and, is involved in this effect. SIRT1 protein level in ADSCs was increased by the treatment with H2O2, meanwhile, H2O2 activated p53-depended apoptosis in high concentration. Incubation of ADSCs with H2O2 dose dependently induced ADSCs apoptosis. SIRT1 overexpression reduced the rate of ADSCs apoptosis, whereas SIRT1 downregulation and EX527 displayed the opposite effect. SIRT1 overexpression decreased the total p53 protein, whereas SIRT1 downregulation and EX527 increased the amount of p53 protein. Co-immunoprecipitation assay showed that SIRT1 could bind to p53, reduce its acetylation level, and treatment with nutlin-3A reversed the effect of SIRT1 on the level of p53 in ADSCs. These results suggest that SIRT1 had a pivotally protective role in the regulation of ADSCs aging and apoptosis induced by H2O2.

P-90 - Oxidative stress caused by accumulation of misfolded Z-type alpha1-antitrypsin

Accumulation of misfolded human Z-type alpha1-antitrypsin protein in the endoplasmic reticulum (ER) leads to persistent ER stress and subsequent cell death, leading to liver cirrhosis. When a Saccharomyces cerevisiae ORF-deletion library was screened for the response elements to accumulation of misfolded Z-type alpha1-antitrypsin protein, several deletion mutants of redox regulator genes aggravated Z-type alpha1-antitrypsin-induced cytotoxicity. Overexpression of Z-type alpha1-antitrypsin in yeasts caused cellular oxidative stress, when assessed by dichlorofluorescein assays. Z-type alpha1-antitrypsin-producing cells became vulnerable to further oxidative challenges with low concentrations of hydrogen peroxide. Protective effects from Z-type alpha1-antitrypsin-induced cytotoxicity of antioxidant chemicals, such as ascorbic acid, N-acetylcysteine, or butylated hydroxyanisole, were also evaluated. Our data add further example of oxidative stress caused by misfolded proteins, as in several human degenerative protein-misfolding diseases, including Alzheimer's, Huntington's, and Parkinson's diseases. The results also provide insight on cellular defense mechanism against protein folding problems and suggest future therapeutic applications.

P-71 - Influx of calcium ions accelerates neurite degeneration via induction of microtubule destabilization

Reactive oxygen species (ROS) attack several living organs and induce neuronal cell death. Previously, we found that treatment with a low concentration of hydrogen peroxide induced neurite degeneration prior to the cell death. The neurites showed abnormal morphologies including beads formation, shrinkage and fragmentation. This phenomenon also observed in hippocampus of the normal-aged and vitamin E-deficient mice. In order to clarify the mechanism of neurite degeneration, we measured lipid peroxidative products in hydrogen peroxide-treated cells. The LOOH levels were significantly increased compared to the untreated group. If cell membranes are oxidized by ROS, large parts of receptors and ion channels may be also damaged. Here, we show the elucidation of the relationship between calcium influx and neurite degeneration in cultured neurons. Treatment with an ionomycin (calcium ionophore) induced neuronal cell death in a concentration- and a time-dependent manner. Treatment with a low concentration of ionomycin induced neurite degeneration via influx of calcium ions, mitochondrial-dependent superoxide production and mitochondrial membrane oxidations. These phenomena were recorded by a time-lapse live imaging system. Finally, these neurite degeneration prevented by antioxidant vita.

Barrier, Mechanical, Morphological and Thermal Properties of Compatibilized High Density Polyethylene and Polyamide 6 Blends

Effectiveness of the content of maleic anhydride (MAH) and polyamide 6 (PA6) on mechanical, thermal, barrier (moisture and oxygen) properties of HDPE/PA6 blends was investigated. Blends of HDPE with PA6 were prepared by in situ method. Molau test and FTIR spectroscopy results confirmed the reactive compatibilization through grafting of MAH on HDPE and PA6 chains in PA6/HDPE blends. Low concentration of benzoyl peroxide (BPO) and MAH reduced the particle size, improved phase morphology and mechanical properties of PA6/HDPE blends. Decrease in mechanical properties of PA6/HDPE blends was observed at high concentration of BPO and MAH.

Effects of maternal subclinical hypothyroidism on amniotic fluid cells oxidative status

In this study, we researched the effects of maternal subclinical hypothyroidism on the amniotic fluid cells oxidative metabolism during the first trimester of pregnancy. Oxidative stress and damage biomarkers were assayed in the amniotic fluid cells of healthy and pregnant women with subclinical hypothyroidism. Obtained results show that amniotic fluid cells of pregnant women with subclinical hypothyroidism have significantly higher concentrations of oxidative stress biomarkers (superoxide anion, nitric oxide, peroxynitrite) and oxidative damage (lipid peroxide and micronuclei frequency), but lower concentrations of hydrogen peroxide and oxidized glutathione in comparison to healthy pregnant women. We also showed that oxidative stress biomarkers were positively correlated with micronuclei frequency and lipid peroxide concentration in amniotic fluid cells of pregnant women with subclinical hypothyroidism. The present study provides the first evidence for prooxidative effects of maternal subclinical hypothyroidism on the fetus obtained by the estimating oxidative metabolism in the amniotic fluid cells.

Assessment of a colorimetric method for the measurement of low concentrations of peracetic acid and hydrogen peroxide in water

The recent growing interest in peracetic acid (PAA) as disinfectant for wastewater treatment demands reliable and readily-available methods for its measurement. In detail, the monitoring of PAA in wastewater treatment plants requires a simple, accurate, rapid and inexpensive measurement procedure. In the present work, a method for analyzing low concentrations of PAA, adapted from the US EPA colorimetric method for total chlorine, is assessed. This method employs N,N-diethyl-p-phenylelnediamine (DPD) in the presence of an excess of iodide in a phosphate buffer system. Pink colored species are produced proportionally to the concentration of PAA in the sample. Considering that PAA is available commercially as an equilibrium solution of PAA and hydrogen peroxide (H2O2), a measurement method for H2O2 is also investigated. This method, as the one for the determination of PAA, is also based on the oxidation of iodide to iodine, with the difference that ammonium molybdate Mo(VI) is added to catalyze the oxidation reaction between H2O2 and iodide, quantifying the total peroxides (PAA+ H2O2). The two methods are suitable for concentration ranges from about 0.1–1.65 mg L−1 and from about 0.3–3.3 mg L−1, respectively for PAA and H2O2. Moreover, the work elucidates some relevant aspects related to the operational conditions, kinetics and the possible interference of H2O2 on PAA measurement.

Improved cryosurvival of stallion spermatozoa after colloid centrifugation is independent of the addition of seminal plasma

Addition of seminal plasma (SP) prior to cryopreservation may influence stallion sperm cryosurvival. The objective of this study was to investigate the addition of pooled SP from “good” or “bad” freezer stallions to spermatozoa selected by single layer centrifugation (SLC) prior to cryopreservation on post-thaw sperm quality. Semen from 12 stallions was collected; 5 mL was frozen as control (C) and the remainder was processed by SLC to remove SP and was divided into three aliquots: i) SLC sample without SP (SLC); ii) SLC plus pooled SP from “good freezer” stallions (SLC-GF); iii) SLC plus pooled SP from “bad freezer” stallions (SLC-BF). After thawing, the following parameters were evaluated: chromatin integrity (DNA fragmentation index; %DFI), mitochondrial membrane potential (MMP), membrane integrity (MI), reactive oxygen species (ROS) and sperm kinematics. The %DFI was reduced (P < 0.0001) in SLC samples compared to controls. The SLC group showed a lower proportion of spermatozoa with low MMP and a higher proportion of spermatozoa with high MMP than other groups (P < 0.0001), and had lower hydrogen peroxide content than control. Sperm kinematics were not different. In conclusion, selection by SLC prior to cryopreservation improved post-thaw sperm quality; inclusion of SP from “good” and “bad” freezer stallions did not have an additional beneficial effect.

Synthesis of temperature, pH, light and dual-redox quintuple-stimuli-responsive shell-crosslinked polymeric nanoparticles for controlled release

Herein, we prepared a novel quintuple-stimuli-responsive shell-crosslinked (SCL) nanocontainer in respond to temperature, pH, light, and oxidation or reduction species. The well-defined amphiphilic diblock copolymer poly(2-methacryloyloxyethyl ferrocenecarboxylate)-(5-propargylether-2-nitrobenzyl bromoisobutyrate)-poly(dimethylaminoethyl methacrylate) (PMAEFc-ONB-PDMAEMA) was synthesized via atom transfer radical polymerization (ATRP) and click chemistry. The diblock copolymer self-assembled into spherical micelles with a uniform size in aqueous media as non-crosslinked (NCL) micelles, and then the micelles were crosslinked by N,N′-bis(bromoacetyl) cystamine (BBAC) through quaternization reaction between the nitrogen of DMAEMA and the bromine of BBAC to receive the SCL micelles which shrunk at higher temperature, swelled at acidic pH or a low concentration of hydrogen peroxide (H2O2), decrosslinked by a small amount of DL-dithiothreitol (DTT), and were disrupted with DTT and UV light. The multi-stimuli-sensitive properties of the SCL micelles were characterized in detail by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence spectra, and UV–Vis spectra. Owing to the protective effect of the crosslinked network, light response behaviors of the NCL and SCL micelles were different. In contrast to the single stimulus, the combined stimuli could trigger and regulate the release of hydrophobic drug model more effectively and precisely from the SCL micelles. The obtained multi-stimuli-responsive nanocontainers may lead to a new generation of controlled release in the fields of nanotechnology and biotechnology.

Green synthesized PLA/silver nanoparticle probe for sensing of hydrogen peroxide in biological samples

In this paper, the physio-chemical characteristics of green synthesised PLA/silver nanoparticles (PLA-AgNPs) system was investigated for H2O2 sensing. The precursor, silver nitrate (AgNO3) was reduced to nanosilver (n-Ag) by Piper nigrum leaves extract in dual phase medium containing PLA (Capping agent). X-ray photo electron spectroscopy (XPS) analysis was carried out to evaluate the interaction of PLA with silver nanoparticles. The morphological analysis by Transmission electron microscopy (TEM) obtained images of spherical silver particles with average size of about 10–20 nm. The H2O2 sensing was confirmed from the colour fading of the solution and vanishing of the characteristic surface plasmon resonance (SPR) absorbance peak of PLA-AgNPs on adding H2O2. The proposed sensor can detect even very low concentrations (5 μM) of hydrogen peroxide and finds applicability in biological and environmental analysis.

Effects of different peracetic acid formulations on post space radicular dentin

Statement of problemThe optimal irrigating solution with antimicrobial and dentin cleansing properties for post space preparation for fiber posts is unclear. Peracetic acid is one option but is available in various chemical formulations that require evaluation. PurposeThe purpose of this in vitro study was to evaluate dentin surface cleanliness based on the presence of a smear layer and the number of open dentin tubules. It also investigates the chemical composition of residues after canal irrigation with a 1% peracetic acid solution (PA) at low or high concentration of hydrogen peroxide during the preparation of intracanal fiber posts. Material and methodsAfter filling the root canals of 40 mandibular incisors, a rotary instrument was used for intracanal preparation to place fiber posts. The teeth were divided into 4 groups (n=10) according to the post space irrigation protocol as follows: CG (control): distilled water; NA (NaOCl): 2.5% sodium hypochlorite; LH: PA with low concentration of hydrogen peroxide; and HH: PA with high concentrations of hydrogen peroxide. After irrigation, the teeth were sectioned, and the intracanal dentin surface was subjected to analysis using energy dispersive spectroscopy to evaluate chemical composition and to scanning electron microscopy (×500) to evaluate the presence of the smear layer. The number of open dentin tubules was measured by scanning electron microscopy analysis (×2000) using photo-editing software. ANOVA and the Tukey test (α=.05) were used to evaluate the data, except for the presence of a smear layer, for which the Kruskal-Wallis and Dunn tests were used (α=.05). ResultsThe highest concentrations of oxygen in the dentin residues were detected in LH and HH (P<.05); CG and NA showed similar oxygen concentrations (P>.05). NA had a higher concentration of chlorine (P<.05), whereas LH had a lower amount of smear layer and a larger number of open dentin tubules than the other groups (P<.05). These were equivalent to each other (P>.05), except for HH, which also had a larger number of open dentin tubules than CG and NA (P<.05). ConclusionsPA 1% with a low concentration of hydrogen peroxide yielded a lower amount of smear layer and a larger number of open dentin tubules in the dentin of the post space when compared with PA 1% with a high concentration of hydrogen peroxide, despite maintaining a similar oxygen concentration in these dentin residues.

Color stability, psychosocial impact, and effect on self-perception of esthetics of tooth whitening using low-concentration (6%) hydrogen peroxide.

The aim of this study was to assess the bleaching efficacy and impact on psychosocial and esthetics self-perception of a low-concentration (6%) hydrogen peroxide (H2O2) gel compared with a conventional (37.5%) H2O2 gel when used as an in-office treatment. In total, 35 participants received two sessions of three 12-minute applications of treatment with 37.5% H2O2 on one side of the mouth and 6% H2O2 on the other. Color changes were measured objectively using total variation in color (ΔE) and subjectively using Vita Classical scale (ΔSGU). The Psychosocial Impact of Dental Aesthetic Questionnaire (PIDAQ) and Oral Health Impact Profile (OHIP-14) esthetic questionnaires were administered to measure self-perception and the psychosocial impact of the whitening procedure. Both gels produced significant changes in tooth color at 1 and 3 months post-whitening. The objective efficacy (ΔE) of 37.5% H2O2 (9.06 ± 2.96) was significantly higher than that of 6% H2O2 (5.69 ± 3.06). The results of the subjective assessment were not statistically different. There was a positive impact on esthetic auto perception (OHIP-14, P < .05) and psychosocial impact (PIDAQ, P < .05) at the 3-month time point. Low concentration of H2O2 (6%) achieved effective bleaching (ΔE > 5 units) with good stability at 3 months accompanied by a positive psychosocial impact and enhanced self-perception. However, the traditional 35% concentration was objectively more effective.