Low Concentrations Of Hydrogen Peroxide Research Articles

Non-Isocyanate Polyurethane (NIPU) based on Rubber Seed Oil Synthesized via Low-Pressured Carbonization Reaction

Epoxidised rubber seed oil (ERSO) was successfully synthesized into non-isocyanate polyurethane via carboxylation method whereas peroxoformic acid was formed by in-situ reaction for epoxidation. The effects of temperature and ratio of hydrogen peroxide and formic acid to rubber seed oil carboxylation were studied. The optimum temperature for the epoxidation reaction was found at 50 °C to avoid ring opening reaction of epoxy whilst the optimum ratio of hydrogen peroxide and formic acid is equal molar of double bond: formic acid at 1:2 and 1:1, respectively. At a lower concentration of hydrogen peroxide and formic acid, the oxirane ring was stable due to the lower hydrolysis (oxirane cleavage) of an epoxide. The effect of using low content of formic acid tends to minimize unwanted epoxide ring opening to occur and make the epoxidation rate increased with increasing of oxirane number. Fourier transform infrared (FTIR) spectral displayed the presence of an epoxy functional group at 822 cm-1 and the disappearance of double bond peak at 3011 cm-1 corresponding to epoxidised oil and carbonyl group confirmed the epoxidation reaction had taken place. 1H-NMR was used to confirm the formation of carboxylate functionality after the reaction of epoxy at δ 4.83 and 4.61 ppm. In conclusion, ERSO has great potential to be used as a precursor in producing environmentally friendly non-isocyanate polyurethane.

LED/laser photoactivation enhances the whitening efficacy of low concentration hydrogen peroxide without microstructural enamel changes

Background: The association of low concentration hydrogen peroxide (HP) and a light source has been widely used to achieve efficient bleaching. We investigated the colorimetric and microstructural changes of bovine enamel bleached with 6% HP associated or not with a hybrid light source system of violet light and laser (LED/laser). Methods: Twenty bovine crowns were used to obtain specimens of 7 × 7 × 2 mm. Then, they were randomized in two groups (n=10): 6% HP and 6% HP + LED/laser. After staining with dark tea solution, three bleaching sessions were performed. Colorimetric evaluation (∆L*, ∆a*, ∆b*, ∆E00 [CIEDE2000] and WID) after 24 hours of each session and 7 days after the final bleaching session was performed. Enamel Vickers microhardness at baseline, 24 hours and 7 days after the last bleaching session were also evaluated. Two-way repeated measures ANOVA and Bonferroni post-test was used at a significance level of 5%. Results: 6% HP and 6% + HP LED/laser showed satisfactory bleaching results. The group photoactivated showed higher WID values (p<0.05). Differences between groups were observed for ∆E00, ∆L* and ∆a* (p<0.05), except for ∆b* (p>0.05). Intra-group differences were also found (p<0.05). Regarding microhardness, no inter or intra-group differences were observed (p>0.05). Conclusions: The photoactivation with LED/laser enhanced the whitening efficacy of 6% HP compared to the group without photoactivation. Thus, the LED/laser activation appears to be a good option when using low concentration HP-based agents. In addition, both bleaching protocols did not cause changes on enamel microhardness.

Scalable production of hydroxyl radicals (.OH) via homogeneous photolysis of hydrogen peroxide using a continuous-flow photoreactor

We establish the fact that in a continuous-flow scalable photoreactor system employed for the homogeneous photolysis of H2O2 into .OH radicals, the quantum yield of photolytic conversion in aqueous solution cannot be regarded as a linear function of H2O2 initial concentration. We were successful in repeatedly producing high concentrations of .OH radical (between 40 and 90 mM) from relatively low concentrations of hydrogen peroxide (between 0.1 M − 5 M) in aqueous solution in a scalable manner using our serially connected photoreactor system. Our investigation demonstrates that merely selecting a very high initial concentration of H2O2 will not necessarily result in the highest conversion into .OH radical. We also developed a simple and in-situ acid-base titrimetric method for quantitation of .OH radicals and demonstrated an accuracy of our method within ~±6.6% of a 31P NMR method. Hence, our proposed scalable .OH radical production method via continuous-flow photoreactors can be regarded as a safe, simple, accurate and cost-effective technique for various industrial processes, particularly in aquaculture and swimming pool disinfection, as a replacement of high concentrations of hazardous oxidisers.

Resilience of Microbial Communities after Hydrogen Peroxide Treatment of a Eutrophic Lake to Suppress Harmful Cyanobacterial Blooms.

Applying low concentrations of hydrogen peroxide (H2O2) to lakes is an emerging method to mitigate harmful cyanobacterial blooms. While cyanobacteria are very sensitive to H2O2, little is known about the impacts of these H2O2 treatments on other members of the microbial community. In this study, we investigated changes in microbial community composition during two lake treatments with low H2O2 concentrations (target: 2.5 mg L−1) and in two series of controlled lake incubations. The results show that the H2O2 treatments effectively suppressed the dominant cyanobacteria Aphanizomenon klebahnii, Dolichospermum sp. and, to a lesser extent, Planktothrix agardhii. Microbial community analysis revealed that several Proteobacteria (e.g., Alteromonadales, Pseudomonadales, Rhodobacterales) profited from the treatments, whereas some bacterial taxa declined (e.g., Verrucomicrobia). In particular, the taxa known to be resistant to oxidative stress (e.g., Rheinheimera) strongly increased in relative abundance during the first 24 h after H2O2 addition, but subsequently declined again. Alpha and beta diversity showed a temporary decline but recovered within a few days, demonstrating resilience of the microbial community. The predicted functionality of the microbial community revealed a temporary increase of anti-ROS defenses and glycoside hydrolases but otherwise remained stable throughout the treatments. We conclude that the use of low concentrations of H2O2 to suppress cyanobacterial blooms provides a short-term pulse disturbance but is not detrimental to lake microbial communities and their ecosystem functioning.

Bleaching and microstructural effects of low concentration hydrogen peroxide photoactivated with LED/laser system on bovine enamel

BackgroundTooth whitening protocols with low concentration hydrogen peroxide (HP) appear to minimize the microstructural effect on teeth. In addition, light sources have been used to enhance bleaching efficiency. This study evaluated the color change and microhardness of a protocol with 6% HP photoactivated by LED/laser in comparison with 35% HP. MethodsTwenty bovine incisors were randomized in two groups: 6% HP + LED/laser and 35% HP (n=10). Teeth were submitted to staining using dark tea. Three whitening sessions were carried out according to the manufacturer's instructions. Enamel microhardness (VHN) and color change evaluation (∆L*, ∆a*, ∆b*, ∆E00 [CIEDE2000], and WID) before 24 hours and 7 days after the last whitening session were performed. Two-way repeated ANOVA and Bonferroni post-test was used (α = 0.05). ResultsBoth groups showed perceptible color changes, being more pronounce for 35% HP. Differences were observed for ∆a*, ∆b* and ∆E00 (p≤0.027), except for ∆L* (p>0.05). Differences were also found in the comparison among the evaluation times within the same group (p≤0.027), except for ∆a* results (p>0.05). WID showed that 35% HP exhibited high whiteness values. Regarding microhardness, the groups did not show significant differences (p>0.05). However, 35% HP showed decreased values after 7 days of the last whitening session compared to the baseline (p≤0.027). Conclusions6% HP + LED/laser promoted perceptible color change, but not comparable with 35% HP. No differences on enamel microhardness were observed between the whitening protocols. However, 35% HP showed decreased hardness after 7 days of whitening compared to baseline.

Mechanisms of Sporicidal Activity Induced by Ionized Hydrogen Peroxide in the Spores of Bacillus atrophaeus.

Introduction: Ionized hydrogen peroxide (iHP) is a new technology used for the decontamination of surfaces or laboratory areas. It utilizes a low concentration of hydrogen peroxide (H2O2) mixed with air and ionized through a cold plasma arc. This technology generates reactive oxygen species as a means of decontamination. Objectives: The purpose of this study is to review the effects of iHP on the structure of the spores of Bacillus atrophaeus by observing its effects using transmission electron microscopy (TEM) and also by evaluating the existence of DNA damage by fluorescence-based quantitative polymerase chain reaction (qPCR). Methods: Spore samples of B. atrophaeus decontaminated using iHP at different exposure times (Control, 1, 2, 6, and 12 h) were fixed for TEM. In addition, DNA was extracted for evaluation of DNA damages using fluorescence-based qPCR assays. Results: Damages to the spore structures of B. atrophaeus caused by the decontamination process with iHP at different exposure times (Control, 1, 2, 6, and 12 h) can be observed in micrographs. The effects of the decontamination to short DNA segment (132 base pairs [bp]) of the yaaH gene using qPCR present a linear degradation, and for the long DNA segment (680 bp), it presents a biphasic mode. Conclusion: The results of the qPCR analysis show two initial stages of damage to DNA with very noticeable damage at 12 h contact time, which confirms the observations of the TEM micrographs for the B. atrophaeus spores. The study demonstrates damage to the spore core DNA.

Molecular weight distribution and corrosion inhibitor activity of 4-vinylpyridine oligomer synthesized using low concentration hydrogen peroxide as the initiator

Low molecular weight 4-vinylpyridine oligomer or O(4-VP) has been synthesized using 0.25 M hydrogen peroxide as the initiator. The resulting O(4-VP) was characterized by Fourier transform infrared (FTIR) spectroscopy for identification of functional groups, and mass spectroscopy (MS) for determination of molecular weights. O(4-VP) was tested as a corrosion inhibitor of mild steel in a corrosive solution saturated with carbon dioxide using wheel test and electrochemical methods, i.e., electrochemical impedance spectroscopy (EIS) and Tafel plots. Mild steel surface analysis was performed by scanning electron microscopy (SEM). The product of the synthesis is a viscous orange compound. The mass spectrum showed that O(4-VP) had a mass (m/z) of 100–900, which is in accordance with the chain length of 1–9 monomer units, where the chain length of 4 (tetramer) is the most abundant fraction. The FTIR results show no significant difference between the monomer and O(4-VP). The wheel test as a screening test showed that O(4-VP) exhibited corrosion inhibitor activity. This activity was confirmed by the results of EIS and Tafel analyses, which also demonstrated that protection increased with increasing concentration of O(4-VP) and temperature. At temperature 70°C and a concentration of 150 mg L –1 , the protection by O(4-VP) reached 81.9% (based on EIS) and 87.8% (based on Tafel plots). Protection of mild steel was also confirmed by the surface morphology of the sample obtained by SEM characterization.

Evaluation of the compounds commonly known as superoxide dismutase and catalase mimics in cellular models

Oxidative stress that results from an imbalance between the concentrations of reactive species (RS) and antioxidant defenses is associated with many pathologies. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase are among the key enzymes that maintain the low nanomolar physiological concentrations of superoxide and hydrogen peroxide. The increase in the levels of these species and their progeny could have deleterious effects. In this context, chemists have developed SOD and CAT mimics to supplement them when cells are overwhelmed with oxidative stress. However, the beneficial activity of such molecules in cells depends not only on their intrinsic catalytic activities but also on their stability in biological context, their cell penetration and their cellular localization. We have employed cellular assays to characterize several compounds that possess SOD and CAT activities and have been frequently used in cellular and animal models. We used cellular assays that address SOD and CAT activities of the compounds. Finally, we determined the effect of compounds on the suppression of the inflammation in HT29-MD2 cells challenged by lipopolysaccharide. When the assay requires penetration inside cells, the SOD mimics Mn(III) meso-tetrakis(N-(2′-n-butoxyethyl)pyridinium-2-yl)porphyrin (MnTnBuOE-2-PyP5+) and Mn(II) dichloro[(4aR,13aR,17aR,21aR)-1,2,3,4,4a,5,6,12,13,13a,14,15,16,17,17a,18,19,20,21,21a-eicosahydro-11,7-nitrilo-7Hdibenzo[b,h] [1,4, 7,10] tetraazacycloheptadecine-κN5,κN13,κN18,κN21,κN22] (Imisopasem manganese, M40403, CG4419) were found efficacious at 10 μM, while Mn(II) chloro N-(phenolato)-N,N′-bis[2-(N-methyl-imidazolyl)methyl]-ethane-1,2-diamine (Mn1) requires an incubation at 100 μM. This study thus demonstrates that MnTnBuOE-2-PyP5+, M40403 and Mn1 were efficacious in suppressing inflammatory response in HT29-MD2 cells and such action appears to be related to their ability to enter the cells and modulate reactive oxygen species (ROS) levels.

Ultrafast Directional Janus Pt-Mesoporous Silica Nanomotors for Smart Drug Delivery.

Development of bioinspired nanomachines with an efficient propulsion and cargo-towing has attracted much attention in the last years due to their potential biosensing, diagnostics, and therapeutics applications. In this context, self-propelled synthetic nanomotors are promising carriers for intelligent and controlled release of therapeutic payloads. However, the implementation of this technology in real biomedical applications is still facing several challenges. Herein, we report the design, synthesis, and characterization of innovative multifunctional gated platinum–mesoporous silica nanomotors constituted of a propelling element (platinum nanodendrite face), a drug-loaded nanocontainer (mesoporous silica nanoparticle face), and a disulfide-containing oligo(ethylene glycol) chain (S–S–PEG) as a gating system. These Janus-type nanomotors present an ultrafast self-propelled motion due to the catalytic decomposition of low concentrations of hydrogen peroxide. Likewise, nanomotors exhibit a directional movement, which drives the engines toward biological targets, THP-1 cancer cells, as demonstrated using a microchip device that mimics penetration from capillary to postcapillary vessels. This fast and directional displacement facilitates the rapid cellular internalization and the on-demand specific release of a cytotoxic drug into the cytosol, due to the reduction of the disulfide bonds of the capping ensemble by intracellular glutathione levels. In the microchip device and in the absence of fuel, nanomotors are neither able to move directionally nor reach cancer cells and deliver their cargo, revealing that the fuel is required to get into inaccessible areas and to enhance nanoparticle internalization and drug release. Our proposed nanosystem shows many of the suitable characteristics for ideal biomedical destined nanomotors, such as rapid autonomous motion, versatility, and stimuli-responsive controlled drug release.

A low power flexible dielectric barrier discharge disinfects surfaces and improves the action of hydrogen peroxide

There is an urgent need for disinfection and sterilization devices accessible to the public that can be fulfilled by innovative strategies for using cold atmospheric pressure plasmas. Here, we demonstrate a successful novel combination of a flexible printed circuit design of a dielectric barrier discharge (flex-DBD) with an environmentally safe chemical reagent for surface decontamination from bacterial contaminants. Flex-DBD operates in ambient air, atmospheric pressure, and room temperature without any additional gas flow at a power density not exceeding 0.5 W/cm2. The flex-DBD activation of a 3% hydrogen peroxide solution results in the reduction in the bacterial load of a surface contaminant of > 6log10 in 90 s, about 3log10 and 2log10 better than hydrogen peroxide alone or the flex-DBD alone, respectively, for the same treatment time. We propose that the synergy between plasma and hydrogen peroxide is based on the combined action of plasma-generated OH· radicals in the hydrogen peroxide solution and the reactive nitrogen species supplied by the plasma effluent. A scavenger method verified a significant increase in OH· concentration due to plasma treatment. Novel in-situ FTIR absorption spectra show the presence of O3, NO2, N2O, and other nitrogen species. Ozone dissolving in the H2O2 solution can effectively generate OH· through a peroxone process. The addition of the reactive nitrogen species increases the disinfection efficiency of the hydroxyl radicals and other oxygen species. Hence, plasma activation of a low concentration hydrogen peroxide solution, using a hand-held flexible DBD device results in a dramatic improvement in disinfection.

Research about Organic Matter Removal and Biofilms Development of Pilot-Scale UV/H2O2-BAC Process

As a green advanced process for drinking water treatment, the UV/hydrogen peroxide (UV/H2O2) process has been gradually applied in China. To study the effect and mechanism of organic matter removal and the development of microbial communities in the UV/H2O2-biological activated carbon (UV/H2O2-BAC) process, a pilot-scale UV/H2O2-BAC system was built and operated over one year. Low water temperature affects the UV/H2O2 process efficiency, the biofilms in the BAC system were mature and stable after 240 days, and the contribution rate of BAC adsorption to dissolved organic carbon (DOC) removal was approximately 14.2% after one year of operation. The liquid chromatography-organic carbon detection (LC-OCD) analysis shows that UV/H2O2 process can increase the amounts of Low Molecular Weight (LMW) neutrals, and the specific UV absorbance (SUVA254) value is not suitable for predicting Trihalomethanes (THMs) precursor contents in water after UV/H2O2 treatment. High-throughput sequencing results prove that microbial species in the middle section are the most abundant compared to those in the influent and effluent sections, hydrogen peroxide has lower inhibition on the development of microbial community than ozone and the low concentration of hydrogen peroxide (&lt;0.25 mg/L) promotes the development of the microbial communities, hydrogen peroxide can reduce Proteobacteria abundance by inhibiting the growth of anaerobes. Acidobacteria may have a certain contribution to the degradation of soil organic matter (SOM), and the effluent section of BAC with low DOC concentration cannot form the dominant species of Rhodobacter.

Reaction kinetics formulation with explicit radiation absorption effects of the photo-Fenton degradation of paracetamol under natural pH conditions.

The degradation of paracetamol (PCT) in an aqueous medium using the Fenton and photo-Fenton reactions was investigated. The aim of this research was the development of a kinetic model based on a reaction mechanism, which includes two main intermediates of PCT degradation and the local volumetric rate of photon absorption (LVRPA). Ferrioxalate was used as a catalyst and the working pH was adjusted to 5.5 (natural pH). Experimental work was planned through a D-optimal experimental design and performed in a flat plate reactor irradiated by a solar simulator. Hydrogen peroxide (HP) concentration, reaction temperature, and radiation level were the operating parameters. The photo-Fenton reaction allowed to reach a minimum relative PCT concentration of 2.01% compared to 5.04% achieved with Fenton reaction. Moreover, the photo-Fenton system required a 50% shorter reaction time and lower HP concentration than in dark conditions (90 min and 189 mg L-1 vs. 180 min and 334 mg L-1, respectively). The experimental results were used to estimate the kinetic parameters of the proposed kinetic model employing a nonlinear, multi-parameter regression method. The values obtained from the normalized root-mean-square error (14.52, 1.96, 4.36, 13.16, and 8.72 % for PCT, benzoquinone, hydroquinone, HP, and oxalate, respectively) showed a good agreement between the predicted and experimental data.

Biodegradation of graphene materials catalyzed by human eosinophil peroxidase.

Understanding the biodegradability of graphene materials by the action of oxidative enzymes secreted by immune cells is essential for developing applicable biomedical products based on these materials. Herein, we demonstrate the biodegradation of graphene oxide (GO) by recombinant eosinophil peroxidase (EPO) enzyme extracted from human eosinophils in the presence of a low concentration of hydrogen peroxide and NaBr. We compared the degradation capability of the enzyme on three different GO samples containing different degrees of oxygen functional groups on their graphenic lattices. EPO succeeded in degrading the three tested GO samples within 90 h treatment. Raman spectroscopy and transmission electron microscopy analyses provided clear-cut evidence for the biodegradation of GO by EPO catalysis. Our results provide more insight into a better understanding of the biodegradation of graphene materials, helping the design of future biomedical products based on these carbon nanomaterials.

A Case of Hepatic Portal Venous Gas Due to Accidental Ingestion of Low-concentration Hydrogen Peroxide

A Case of Hepatic Portal Venous Gas Due to Accidental Ingestion of Low-concentration Hydrogen Peroxide

Constitutive expression of Arabidopsis bZIP transcription factor AREB1 activates cross-signaling responses in soybean under drought and flooding stresses

Abiotic stress, such as drought and flooding, are responsible for considerable losses in grain production worldwide. Soybean, the main cultivated oilseed in the world, is sensitive to both stresses. Plant molecular mechanisms answer via crosstalk of several signaling pathways, in which particular genes can respond to different stresses. Previous studies confirmed that overexpression of transcription factor AtAREB1 confers drought tolerance in soybean. However, plants containing this gene have not yet been tested under flooding. Thus, the objective of this study was to characterize genetically modified (GM) soybean plants overexpressing AtAREB1 under drought and flooding conditions in comparison to its genetic background. Physiological and biochemical measurements were performed. In addition, the expression level of genes commonly activated under both stresses was evaluated. The results supported the role of the AtAREB1 gene in conferring tolerance to water deficit in soybeans. Furthermore, under flooding, the GM line was efficient in maintaining a higher photosynthetic rate, intrinsic efficiency in water use, and instantaneous carboxylation efficiency, resulting in higher grain yield under stress. The GM line also presented higher protein content, lower concentration of hydrogen peroxide, and lower expression levels of genes related to fermentative metabolism and alanine biosynthesis. These results indicate that in addition to drought stress, plants overexpressing AtAREB1 exhibited better performance under flooding when compared to the non-GM line, suggesting a cross-signaling response to both abiotic factors.

Study of highly furfural-containing refinery wastewater streams using a conventional homogeneous Fenton process

The conventional Fenton process has been evaluated to treat highly furfural-containing wastewater of 76 g/L at an initial pH of 3. Streams of these features can be accidentally generated after solvent extraction operations in petrol refineries, which leads to significant concern for downstream wastewater treatment facilities. The influence of temperature, initial hydrogen peroxide, and iron catalyst concentrations was investigated. Intensive oxidizing conditions (64 g/L of hydrogen peroxide initial concentration, temperatures higher than 50 °C, or catalyst concentration -FeSO4- higher than 1.26 g/L) produce a higher concentration of carbonyl intermediate compounds, that promote the subsequent generation of complex molecules hardly biodegradable (humins). In contrast, treating a diluted furfural stream (ca. 3 g/L) from a refinery using a temperature of 60 °C and a hydrogen peroxide concentration of 5.7 g/L did not evidence the formation of humins. In these conditions, the oxidation of furfural preferentially proceeds by oxidation of furfural to furoic acid and 2(5H)-furanone, further opening of the furan ring and subsequent oxidation until readily biodegradable acetic and formic acids. When working with highly concentrated wastewater streams, milder oxidizing conditions are required, such as low temperature (20–40 °C), low hydrogen peroxide (< 38 g/L) and a H2O2/Fe2+ mass ratio lower than 109 to prevent the formation of non-biodegradable humins. A remarkable furfural removal (> 99%) and low depletion of total carbon were achieved with highly furfural concentrated effluents (76 g/L of furfural) at 40 °C and a low concentration of hydrogen peroxide (38 g/L).

Color stability of dental enamel bleached with violet LED associated with or without Low concentration peroxide gels.

This study aimed to evaluate the in vitro color of dental enamel bleached with the violet LED, associated with or without low-concentration of peroxide; analyzed in two time intervals: 24 h later and 6 months after the treatment. Ninety fragments of bovine teeth (6 × 6 mm and 3 mm thick) were randomly divided into 6 groups according to bleaching treatment: NB - no bleaching, VL - Violet LED, HP- 7.5 % hydrogen peroxide, HP + VL - 7.5 % hydrogen peroxide + violet LED, CP - 22 % carbamide peroxide, CP + VL - 22 % carbamide peroxide + violet LED. The color change was analyzed by using a spectrophotometer, at time intervals of 24 h and 6 months after performing the bleaching techniques (n = 12). Scanning electron microscopy (SEM) was performed to verify the enamel surface morphology after treatment (n = 3). The color change data were analyzed using ANOVA and a post-hoc Tukey tests (α = 0.05). The VL group showed chromatic changes after 24 h of treatment, however the groups submitted to bleaching gel treatments associated with or without violet LED (CP + VL, CP, HP, HP + VL) showed the highest color change values at all time intervals analyzed, with color stability after 6 months of treatment for the CP + VL group. Scanning electron microscopy analysis showed the greatest change in enamel surface for Groups CP and HP. It could be concluded that violet LED had immediate bleaching effect without promoting significant changes in enamel morphology, however the association with carbamide peroxide 22 % showed color stability and greater bleaching efficacy than the use of violet LED alone, after 6 months.

Effect of violet led associated with low-concentration hydrogen peroxide on enamel surface roughness

Aim: The present study aimed to assess in vitro the effect ofviolet LED in tooth bleaching techniques associated or not withlow-concentration hydrogen peroxide gel on enamel surfaceroughness. Methods: Fifty-two enamel fragments of bovineteeth were flattened and polished (4x4x3 mm) and dividedinto four groups according to bleaching treatment: VL- VioletLED; HP- 7.5% hydrogen peroxide; HP+VL- 7.5% hydrogenperoxide + violet LED; C- No bleaching (control). Before thetreatments, all specimens were immersed in 20 mL of blacktea for six days, changing solutions every 24 h to simulatethe staining of specimens. Forty fragments were used toanalyze surface roughness (n=10) and 12 fragments wereused for the morphological analysis (SEM) (n=3). Results:The data were submitted to one-way ANOVA and a post-hocTukey test. The lower roughness values was observed for thegroup that did not receive bleaching treatment (C), differingsignificantly only from the group bleached with 7.5% hydrogenperoxide + violet LED (HP+VL) (p=0.0077). The remaininggroups did not show significant differences in roughnessvalues (p&gt;0.05). The scanning electron microscopy analysisshowed irregularities on the enamel surface regardless ofthe treatment received. Conclusion: The results showedthat bleaching treatments with violet LED associated withlow-concentration hydrogen peroxide gels (7.5%) increasethe surface roughness of tooth enamel.

Effectiveness of Whitening Strips Use Compared With Supervised Dental Bleaching: A Systematic Review and Meta-analysis.

Bleaching performed at home while under the supervision of a dentist provides greater color alteration compared with whitening strips when evaluated with a spectrophotometer, although the color alteration was undetectable by unaided human eyes. Objective: A systematic review and meta-analysis were performed to answer the following research question: Does the use of whitening strips (WS) lead to an equivalent color change compared with supervised dental bleaching in patients with permanent dentition?Methods: A search was performed on August 10, 2017 (updated on March 22, 2019), in PubMed, the Brazilian Library in Dentistry, Latin American and Caribbean Health Sciences Literature database, Cochrane Library, Scopus, Web of Science, and SIGLE, without restrictions regarding date or language. Abstracts from the International Association for Dental Research, unpublished and ongoing trial registries, dissertations, and theses were also searched. Only randomized clinical trials (parallel or split mouth) in patients with permanent dentition that compared WS with dentist-supervised dental bleaching performed at home (AH) or in office (IO) were included. The risk of bias (RoB) was evaluated using the Cochrane Collaboration tool. A meta-analysis with subgroup analysis (low and high peroxide concentration) was conducted for color change ΔE* (spectrophotometer) and ΔSGU (shade guide units), risk and intensity of tooth sensitivity (TS), gingival irritation (GI), and patient satisfaction using a random effects model. Heterogeneity was assessed with the Cochrane Q test and I2 statistics. GRADE (Grading of Recommendations, Assessment, Development and Evaluation) was used to assess the quality of the evidence.Results: After the removal of duplicates, followed by title and abstract screening, 20 studies remained. Only two studies were considered to have a low RoB; 11 had a high RoB, and seven had an unclear RoB. For WS versus IO, data were not available for the meta-analysis. For WS versus AH bleaching, a significant difference in ΔE* favoring the AH group was observed (standardized mean difference [SMD] = -0.50, 95% confidence interval [CI] -0.79 to 0.21), but the risk (risk ratio = 0.78, 95% CI 0.65 to 0.93) and intensity of TS (SMD = -0.30, 95% CI -0.56 to -0.04) were lower in the WS group. Color change in ΔSGU, risk and intensity of GI, and patient satisfaction were not significantly different between groups (p>0.20). The quality of evidence for ΔE*, risk and intensity of TS, and intensity of GI were graded as moderate.Conclusion: Although the risk and intensity of TS were lower in the WS group, dentist-supervised at-home bleaching led to a better color change when measured with a spectrophotometer, although the color alteration was undetectable by unaided human eyes.

Treatment with Nd:YAG Laser Irradiation Combined with Sodium Hypochlorite or Hydrogen Peroxide Irrigation on Periodontal Pathogens: An In Vitro Study.

Objective: The purpose of this study was to evaluate the effect of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with low concentrations of hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl) on viability of oral bacteria. Materials and methods: Bacterial species Streptococcus gordonii, Porphyromonas gingivalis, and Fusobacterium nucleatum were grown in an anaerobic chamber at 37°C. Samples were irradiated with the Nd:YAG laser (1064 nm, 300 μm Varian tip) using parameters: 150 mJ, 20 Hz, 3 W, 50 sec, and 100 μs short pulse duration in contact mode. Treatment groups included (1) control, (2) Nd:YAG, (3) 0.5% H2O2, (4) Nd:YAG and 0.5% H2O2, (5) 0.5% NaOCl, and (6) Nd:YAG with 0.5% NaOCl. Viable colonies were counted, calculated into colony forming unit/mL, and converted into log form for statistical analysis using a two-tailed paired t-test. Results: The combined treatment with the Nd:YAG and H2O2 showed the greatest reduction in all bacterial viability compared with other treatment groups (p < 0.001). Antiseptic solutions and laser were most effective against P. gingivalis, least effective against S. gordonii but improved significantly in combination with laser irradiation (p < 0.001). Laser alone was effective against all of three bacterial species, however, it was not significant. Conclusions: Combination treatment with Nd:YAG laser and an oxidative disinfectant (0.5% NaOCl or H2O2) resulted in more effective reduction of bacterial viability than monotherapies.