High Concentrations Of Hydrogen Peroxide Research Articles

High-concentration hydrogen peroxide production by solar interfacial catalysis

Solar-driven catalytic synthesis of H2O2 is an ideal alternative to the anthraquinone method, but current photocatalysts still suffer from low activity and inefficient solar energy utilization. Here we presented an economic and efficient solar interfacial catalysis system (SICS) that incorporated photothermal–photocatalytic materials into commercial sponge to simultaneously generate the required heat and carriers for H2O2 production. We demonstrated its superiority over conventional particulate photocatalysis (PC) in photocatalytic H2O2 production. The SICS, located at the air–water interface, remarkably improve the activities of photocatalysts by efficient utilization of solar-converted heat. The produced H2O2 from SICS was reserved in the sponge and resulted in an ultrahigh concentration of 46 mM for per gram catalyst after 1 h solar irradiation. As thus, our application experiments confirmed that the SICS presented great advantages in organic pollutant (e.g. phenol and tetracycline) degradation compared with conventional PC. This work paves a new way for the industrialization of solar-driven catalysis.

In vitro evaluation of the tooth bleaching efficacy and safety of high-concentration hydrogen peroxide with cold atmospheric plasma

Using hydrogen peroxide (HP) for tooth bleaching may induce various side effects. Cold atmospheric plasma (CAP) is a promising solution. We aimed to evaluate and compare the efficacy and safety of tooth bleaching using high-concentration HP with CAP with conventional in-office bleaching. Fifty-one discolored extracted human teeth were assigned to three groups: Group 1 (light-emitting diode with 35% HP), Group 2 (CAP with 35% HP), and Group 3 (only CAP). Bleaching was conducted over three sessions for a total of 20 min. The bleaching effect was evaluated based on the changes in color (ΔE00 and WID) and lightness (ΔL and ΔG). Safety was assessed by examining the dark areas on the enamel and monitoring the pulp chamber temperature. The study analyzed how different bleaching methods and durations affected ΔE00 and ΔWID using repeated-measures analysis of variance (ANOVA). The Kruskal-Wallis and Mann-Whitney tests were used for ΔL and dark areas, and one-way ANOVA for ΔG after 20 min of bleaching. The ΔE00 and WID demonstrated an interaction based on the bleaching method and time, with Group 1 exhibiting the highest ΔE00 and WID at all treatment times (p < 0.001). ΔL* and ΔG did not differ significantly between Groups 1 and 2 (p = 0.056 and 0.062, respectively) and were lowest in Group 3 (p < 0.001). Group 1 exhibited the darkest areas and highest pulp chamber temperatures (p < 0.001). Group 1 exhibited statistically significant color changes. Group 2 demonstrated similar effects, but with enhanced safety profiles. Group 2, although displaying a slightly less pronounced color change compared with Group 1, achieved a color alteration readily discernible to the naked eye. This suggests that CAP with 35% HP could be an interesting area for further investigation as an alternative to traditional in-office bleaching methods.

A Study of Accelerated Corrosion of Stainless Steels under Highly Oxidizing Conditions

The corrosion behavior of certain steels under extremely oxidative conditions, simulating the impact of water radiolysis on stainless steels, has been investigated. Radiolysis generates aggressive species, including radicals, solvated electrons, and hydrogen peroxide, potentially leading to corrosion over time in materials typically considered resistant. To expedite the kinetics of this phenomenon, drastic conditions were employed, involving high concentrations of peroxide in a strongly acidic environment. Under these conditions, corrosion can manifest rapidly. The varied responses of different steels are contingent upon their inherent nature and chemical composition, notably the chromium and nickel content. Steels with higher chromium and nickel concentrations exhibit increased resistance to corrosion, even in such severe environments. Microscopic corrosion mechanisms involve pitting and intergranular corrosion. Pitting results in the formation of craters on surfaces, while intergranular corrosion leads to the detachment of grains.

Effect of whitening toothpastes with different hydrogen peroxide concentrations: Penetration into the pulp chamber and color change

ObjectivesThis study evaluated the efficacy of simulated brushing with toothpastes containing different concentrations of hydrogen peroxide (HP) in pulp chamber penetration and color change. Also, physical-chemical properties (concentration, pH and viscosity) were evaluated. MethodsForty-nine premolars were divided into seven groups (n = 7): untreated (control); whitening gel (White Class 6 %, 6 %BG) with one 90 min application (6 %BG 90 min) and 14 applications of 90 min (6 %BG 14×90 min); toothpastes (Colgate Luminous White Glow 3 %, 3 %TP; Crest 3D White Brilliance 4 %, 4 %TP; Colgate Optic White Pro-Series 5 %, 5 %TP) and 6 %BG toothbrushing for 14 applications of 90 s. HP penetration into the pulp chamber was measured through UV–Vis spectrophotometry and color change with a spectrophotometer (ΔEab, ΔE00, and ΔWID). Initial concentration, pH, and viscosity were measured through Titration, Digital pH-meter, and Rheometer, respectively. Statistical analysis used one-way ANOVA and Tukey's test (α = 0.05). Results6 %BG (14×90 min) and 4 %TP groups showed acidic pH and higher concentrations of HP in the pulp chamber compared to the other groups (p < 0.05). On the other side, 3 %TP and 5 %TP groups showed alkaline pH, higher viscosity between the toothpastes and lower HP penetration (p < 0.05). The 6 %BG AH (14×90 min) group exhibited the most significant color change (ΔEab, ΔE00, and ΔWID) (p < 0.05). ConclusionsBrushing with whitening toothpaste with an acidic pH leads to greater HP penetration into pulp chamber; but, even when a high concentrated HP whitening toothpaste was used, a lower whitening effect was observed when compared to a two-week at-home bleaching. Clinical SignificanceWhitening toothpastes containing up to 5 % HP produced lower whitening effect than two-week at-home bleaching. Additionally, HP was detected within the pulp chamber which can potentially impact in tooth sensitivity.

Understanding the unique mechanism of ferroptosis: a promising therapeutic target.

Ferroptosis is an iron-dependent form of regulated cell death and is characterized by high concentrations of intracellular lipid peroxide and a redox imbalance in the cells. Ferroptosis shows distinct morphological and biological features compared with other prominent mechanisms of programmed cell death. The distinct characteristics of ferroptosis include the dysfunction of the lipid peroxide repair enzyme glutathione peroxidase 4, the presence of ferrous iron overload, and the lipid peroxidation of polyunsaturated fatty acids. Several other metabolic pathways (including iron, lipid, and amino acid metabolism) and ferritinophagy, as well as transcription factors, can modulate ferroptosis. However, to date, the molecular mechanism of ferroptosis has not been elucidated. This review outlines the discovery, characterization, regulatory mechanisms, and crosstalk of ferroptosis. Further, we have noted the controversial elements in the ferroptosis-related mechanisms. Our inferences may provide a partial reference for developing strategies to regulate ferroptosis.

An Investigation on the Effect of N-Hydroxyphthalimde and Supercritical Carbon Dioxide on the Peroxide Degradation of Polypropylene

The peroxide degradation of polypropylene was studied in supercritical carbon dioxide (scCO2) in the presence of a N-hydroxyphthalimide (NHPI). Six levels of NHPI concentration and 6 levels of peroxide concentration were selected and each permutation was tested both with and without scCO2. It was observed that the NHPI would increase degradation at lower peroxide concentrations (&lt;0.1 wt. %), but would suppress degradation at higher peroxide concentrations (&gt;0.2 wt. %). Furthermore, it was discovered that at an NHPI concentration of 3.3 wt. %, the stereo regularity slightly decreased with increasing peroxide concentrations.

Influence of dental bleaching on the pulp tissue: A systematic review of invivo studies.

Although several studies indicate the harmful effects of bleaching on pulp tissue, the demand for this procedure using high concentrations of hydrogen peroxide (HP) is high. To investigate the influence of bleaching on the pulp tissue. Electronic searches were conducted (PubMed/MEDLINE, Scopus, Cochrane Library and grey literature) until February 2021. Only invivo studies that evaluated the effects of HP and/or carbamide peroxide (CP) bleaching gels on the inflammatory response in the pulp tissue compared with a non-bleached group were included. Risk of bias was performed according to a modified Methodological Index for Non-Randomized Studies scale for human studies and the Systematic Review Centre for Laboratory Animal Experimentation's RoB tool for animal studies. Meta-analysis was unfeasible. Of the 1311 studies, 30 were eligible. Of these, 18 studies evaluated the inflammatory response in animal models. All these studies reported a moderate-to-strong inflammatory response in the superficial regions of pulp, characterized by cell disorganization and necrotic areas, particularly during the initial periods following exposure to 35%-38% HP, for 30-40 min. In the evaluation of human teeth across 11 studies, seven investigated inflammatory responses, with five observing significant inflammation in the pulp of bleached teeth. In terms of tertiary dentine deposition, 11 out of 12 studies noted its occurrence after bleaching with 35%-38% HP in long-term assessments. Additionally, three studies reported significant levels of osteocalcin/osteopontin at 2 or 10 days post-treatment. Other studies indicated an increase in pro-inflammatory cytokines ranging from immediately up to 10 days after bleaching. Studies using humans' teeth had a low risk of bias, whereas animal studies had a high risk of bias. Despite the heterogeneity in bleaching protocols among studies, High-concentrations of HP shows the potential to induce significant pulp damage. High-concentrations of bleaching gel increases inflammatory response and necrosis in the pulp tissue at short periods after bleaching, mainly in rat molars and in human incisors, in addition to greater hard tissue deposition over time. However, further well-described histological studies with long-term follow-up are encouraged due to the methodological limitations of these studies. PROSPERO (CRD42021230937).

Nanoengineered M1 macrophages enhance photodynamic therapy of melanoma through oxygen production and subsequent antitumor immunity

Photodynamic therapy (PDT) is an emerging treatment for melanoma stimulating antitumor immune responses. However, oxygen consumption by PDT exacerbates hypoxia and immunosuppression in the tumor microenvironment. This issue could potentially be addressed by M1 macrophages with high hydrogen peroxide concentrations, which can be catalyzed to oxygen, thereby increasing oxygen level and enhancing intrinsic immune response of M1 macrophages and their ability to stimulate adaptive immunity. Herein, biocompatible photosensitizer-containing nanoparticles were designed by combining bovine serum albumin and manganese dioxide (BMB). These nanoparticles were internalized by M1 macrophages in vitro to form nanoengineered macrophages (BMB@M1). BMB@M1 demonstrated various ways to transfer nanoparticles in melanoma with high tumor site accumulation. Within the tumor microenvironment characterized by hydrogen peroxide and acidity, BMB underwent Mn2+ transformation and generated oxygen. The paramagnetic property of Mn2+ was used for magnetic resonance imaging, enabling visualization of the melanoma enrichment process of BMB@M1. Oxygen supplementation enhanced the therapeutic effect of PDT and stimulated the secretion of IL-12 and IFN-γ by macrophages, synergistically promoting the infiltration of T cells and dendritic cells into the tumor. These findings showed that nanoengineered M1 macrophage could be used as a delivery system to enhance immune effects of PDT.

Substantial improvement in photocatalysis performance of N-TiO2 immobilized on PMMA: Exemplified by inactivation of Staphylococcus aureus and Escherichia coli

Photocatalysis is an efficient process for degrading organic pollutants and inactivating pathogenic microorganisms. However, this process constantly suffers from turbidity shading and particle aggregation in a catalyst suspension system, thereby reducing its photocatalytic activity. Immobilizing the photocatalyst on the light-transmissible surface is a viable solution to the obstacles. So far, the photo-inactivation efficacy between the immobilized photocatalyst and suspension systems has yet to be compared and investigated. In this study, N-TiO2 (NT) immobilized on poly-methyl-methacrylate (PMMA) was fabricated via a dip-coating method, which has a high transmittance rate of 92 % - better than all of the previous works (50 %). By immobilizing N-TiO2 on PMMA, up to 60 % and 19 % improvements in inactivation efficiencies against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) are achieved, respectively, relative to a photocatalyst suspension. Notably, reactive oxygen species (ROSs) detection results indicate that 5 g/L NT coated PMMA ((NT-PMMA)5) has higher intensities of singlet oxygen (1O2), hydroxyl radicals (HO•), and higher concentration of hydrogen peroxide (H2O2) than the NT suspension. The as-made NT-PMMA sustains a 99.99 % inactivation efficiency (5-log-inactivation) against S. aureus through five consecutive photocatalysis cycles of reuse. The inactivation kinetics of S. aureus and E. coli fit well with the modified Hom model. Atomic force microscopy observations indicate that the NT-PMMA inactivation causes more severe damage to S. aureus's cell wall than E. coli due to the different susceptibility of cell wall structure to ROSs. This study paves a substantial way for scaling up the immobilizing catalyst on PMMA for the effective photocatalytic inactivation of pathogens under visible light.

Low and high hydrogen peroxide concentrations of in-office dental bleaching associated with violet light: an in vitro study.

This study aims to assess hydrogen peroxide (HP) penetration within the pulp chamber, color change (CC), physical-chemical properties, and temperature using in-office different concentration bleaching gels with or without violet light. Fifty teeth were divided into five groups (n = 10) based on the HP concentration bleaching gels used (6% and 35%) and the used violet light (with or without). HP penetration within the pulp chamber was measured using UV-Vis. The CC was evaluated with a digital spectrophotometer. Initial and final concentration, and pH were measured through titration, and a Digital pHmeter, respectively. Temperature analyses were measured through a thermocouple. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test(α = 0.05). The presence of violet light did not affect the amount of HP within the pulp chamber, or the CC (p > 0.05). Greater penetration of HP was observed within the pulp chamber, as well as CC when using 35% HP (p < 0.05). The final concentration of both gels was lower than the initial concentration, regardless of the use of violet light (p < 0.05). The initial and final pH levels remained neutral and stable (p > 0.05). The pulp temperature increased when the gels were used in conjunction with violet light (p < 0.05). Using violet light in conjunction with 6% or 35% HP does not alter the physical properties of the bleaching agents, the penetration of HP or enhance color change. However, an increase in temperature was observed when violet light was applied associated with bleaching gels. While the simultaneous use of violet light with hydrogen peroxide 6% or 35% does not alter the material's properties, it also does not bring benefits in reducing hydrogen peroxide penetration and improving color change. Furthermore, the use of violet light increases pulp temperature.

Bacterial community shifts induced by high concentration hydrogen peroxide treatment of Microcystis bloom in a mesocosm study

Hydrogen peroxide has gained popularity as an environmentally friendly treatment for cyanobacterial harmful algal blooms (cHABs) that takes advantage of oxidative stress sensitivity in cyanobacteria at controlled concentrations. Higher concentrations of hydrogen peroxide treatments may seem appealing for more severe cHABs but there is currently little understanding of the environmental impacts of this approach. Of specific concern is the associated microbial community, which may play key roles in the succession/recovery process post-treatment. To better understand impacts of a high concentration treatment on non-target microbial communities, we applied a hydrogen peroxide spray equating to a total volume concentration of 14 mM (473 mg/L, 0.04%) to 250 L mesocosms containing Microcystis bloom biomass, monitoring treatment and control mesocosms for 4 days. Cyanobacteria dominated control mesocosms throughout the experiment while treatment mesocosms experienced a 99% reduction, as determined by bacterial amplicon sequencing, and a 92% reduction in bacterial cell density within 1 day post-treatment. Only the bacterial community exhibited signs of regrowth, with a fold change of 9.2 bacterial cell density from day 1 to day 2. Recovery consisted of succession by Planctomycetota (47%) and Gammaproteobacteria (17%), which were likely resilient due to passive cell component compartmentalization and rapid upregulation of dnaK and groEL oxidative stress genes, respectively. The altered microbiome retained beneficial functionality of microcystin degradation through a currently recognized but unidentified pathway in Gammaproteobacteria, resulting in a 70% reduction coinciding with bacterial regrowth. There was also an 81% reduction of both total nitrogen and phosphorus, as compared to 91 and 93% in the control, respectively, due to high expressions of genes related to nitrogen (argH, carB, glts, glnA) and phosphorus (pntAB, phoB, pstSCB) cycling. Overall, we found a portion of the bacterial community was resilient to the high-concentration hydrogen peroxide treatment, resulting in Planctomycetota and Gammaproteobacteria dominance. This high-concentration treatment may be suitable to rapidly end cHABs which have already negatively impacted the aquatic environment rather than allow them to persist.

Metabolic perturbation studies using a Nash Equilibrium model of liver machine perfusion: modeling oxidative stress and effect of glutathione supplementation

The current clinical standard of Static Cold Storage (SCS) which involves preservation on ice (about +4°C) in a hypoxic state limits storage to a few hours for metabolically active tissues such as the liver and the heart. This period of hypoxia during can generate superoxide and other free radicals from purine metabolism, a well-established component of ischemia/reperfusion injury (IRI). Machine perfusion is at the cutting edge of organ preservation, which provides a functional, oxygenated preservation modality that can avoid/attenuate IRI. In clinical application, perfusion usually follows a period of SCS. This presentation of oxygen following hypoxia can lead to superoxide and hydrogen peroxide generation, but machine perfusion also allows manipulation of the temperature profiles and supply of antioxidant treatments, which could be used to minimize such issues. However, metabolomic data is difficult to gather, and there are currently no mathematical models present to allow rational design of experiments or guide clinical practice. In this article, the effects of a gradual warming temperature policy and glutathione supplementation to minimize oxidative stress are studied. An optimal gradual warming temperature policy for mid-thermic machine perfusion of a liver metabolic model is determined using a combination of Nash Equilibrium and Monte Carlo optimization. Using this optimal gradual warming temperature policy, minimum GSH requirements to maintain hydrogen peroxide concentrations in the normal region are calculated using a different Monte Carlo optimization methodology. In addition, the dynamic behavior of key metabolites and cofactors are determined. Results show that the minimum GSH requirement increases and that the ratio of GSH/GSSG decreases with increasing hydrogen peroxide concentration. In addition, at high concentrations of hydrogen peroxide it is shown that cytochrome C undergoes dysfunction leading to a decrease in useful oxygen consumption and ATP synthesis from the electron transport chain and an overall reduction in the energy charge for the liver cells.

Evidence that protein thiols are not primary targets of intracellular reactive oxygen species in growing Escherichia coli.

The oxidizability of cysteine residues is exploited in redox chemistry and as a source of stabilizing disulfide bonds, but it also raises the possibility that these side chains will be oxidized when they should not be. It has often been suggested that intracellular oxidative stress from hydrogen peroxide or superoxide may result in the oxidation of the cysteine residues of cytoplasmic proteins. That view seemed to be supported by the discovery that one cellular response to hydrogen peroxide is the induction of glutaredoxin 1 and thioredoxin 2. In this study we used model compounds as well as alkaline phosphatase to test this idea. Our results indicate that molecular oxygen, superoxide, and hydrogen peroxide are very poor oxidants of N-acetylcysteine and of the protein thiols of alkaline phosphatase in vitro. Copper could accelerate thiol oxidation, but iron did not. When alkaline phosphatase was engineered to remain in the cytoplasm of live cells, unnaturally high concentrations of hydrogen peroxide were required to oxidize it to its active, disulfide-dependent form, and toxic levels of superoxide had no effect. At the same time, far lower concentrations of these oxidants were sufficient to poison key metalloenzymes. The elimination of glutaredoxin 1 and thioredoxin 2 did not change these results, raising the question of why E. coli induces them during peroxide stress. In fact, when catalase/peroxidase mutants were chronically stressed with hydrogen peroxide, the absence of glutaredoxin 1 and thioredoxin 2 did not impair growth at all, even in a minimal medium over many generations. We conclude that physiological levels of reduced oxygen species are not potent oxidants of typical protein thiols. Glutaredoxin and thioredoxin must either have an alternative purpose or else play a role under culture conditions that differ from the ones we tested.

Two-dimensional multifunctional nanosheets as radiosensitizers for chemodynamic/radio-therapy

The hypoxia tumor microenvironment and low radiation attenuation coefficient of tumor tissue usually limit the efficiency of radiotherapy. In this study, a two-dimensional multifunctional nano-sensitizer, CuNS@Pt, was prepared to function as a radiosensitizer, enhancing radiotherapy through multiple mechanisms. Numerous active sites were provided for the deposition of X-ray radiation energy by the in-situ chemical reduction of Pt to create functional hybrids on Cu-based nanosheets. CuNS@Pt catalyzed high concentration of endogenous hydrogen peroxide to generate oxygen in tumor microenvironment, alleviating the physiological environment of hypoxic tumors. Additionally, CuNS could reduce the content of intrinsic glutathione (GSH) and catalyze hydrogen peroxide to form hydroxyl radicals (·OH). The generated ·OH could damage mitochondria and destroy redox homeostasis due to the functional inclusion of Cu species, thereby achieving chemodynamic therapy and further improving the radiation effect. Both in vivo and in vitro experiments showed that the nano sensitizer effectively improved the therapeutic efficiency of radiotherapy and had good biological safety. All in all, this study provides a pragmatic and doable platform for maximizing the efficacy of RT in cancer. This study also highlights the future research value of two-dimensional nanomaterials.

Iron-based resin heterogeneous photo-self-Fenton system for efficient photocatalytic degradation of antibiotic wastewater

The homogeneous Fenton reaction is limited by its pH requirements for the addition of the iron source and by the safety risks of working with high concentrations of hydrogen peroxide (H2O2) - both of which are major obstacles in the path toward utilizing this reaction for practical applications. In this study, we present a novel heterogeneous photo-self-Fenton system of iron-doped resorcinol formaldehyde (FRF) resin. This system is able to generate and utilize H2O2 in-suit, making it highly efficient at degrading and mineralizing various types of antibiotics (macrolides, sulfonamides, tetracyclines, quinolones) at a neutral pH without the need for additional reagents. Remarkably, the degradation rate constant of oxytetracycline (OTC) increased by 34.2 times compared to the resorcinol formaldehyde (RF) photocatalysis. The enhanced degradation performance of this system is attributed to (i) The Iron-anchored RF, which facilitates the rapid transfer of photogenerated electrons, thereby accelerating the recycling of iron ions and improving the migration and separation efficiency of photogenerated carriers. (ii) The heterogeneous photo-self-Fenton reaction using in situ generated H2O2 to produce abundant hydroxyl radicals. Finally, the mechanism of action and the mineralization pathway of OTC were systematically studied. The OTC undergoes demethylation, hydroxylation, and ring-opening and ultimately is completely mineralized to CO2 and H2O. The work provides a new sustainable pathway for extensively constructing heterogeneous photo-self-Fenton systems.

Fracture strength and hybrid layer formation of endodontically-treated teeth after dental bleaching photoactivated with violet LED

ObjectiveTo evaluate in vitro the effect of dental bleaching using high concentration hydrogen peroxide (HP) photoactivated with violet LED on fracture strength and hybrid layer formation. Methodsforty endodontically-treated bovine teeth were randomized into four groups (n = 10): C - Control, HP – 35% hydrogen peroxide, HP-BL - 35% hydrogen peroxide photoactivated with blue LED, HP-VL - 35% hydrogen peroxide photoactivated with violet LED. Three bleaching sessions with an interval of 7 days between them were performed. After 10 days of the last bleaching session, the dental crowns were restored and submitted to the fracture strength test. Five specimens from each group were used to evaluate the hybrid layer formation by scanning electron microscope (SEM) images. One-way ANOVA and Kruskal-Wallis test were used for parametric and non-parametric data, respectively. Significance level of 5% was adopted to all the tests. ResultsNo differences on fracture strength among the groups were observed (p > 0.05). HP and HP-BL showed alterations on hybrid layer formation compared to C group (p < 0.05), but not for HP-VL (p > 0.05). No differences on hybrid layer formation were observed among HP, HP-VL and HP-BL groups (p > 0.05). ConclusionDental bleaching, photoactivated or not, did not affect the fracture strength of endodontically-treated teeth. Regardless of the protocol used, hydrogen peroxide altered the hybrid layer formation at some level when the restoration was placed after 10 days of the last bleaching session.

Improving Surface Properties of PEEK for Dental Applications by Using Piranha Solution.

"Polyetheretherketone (PEEK)" is a biocompatible, high-strength polymer that is well-suited for use in dental applications due to its unique properties. However, achieving good adhesion between PEEK and hydrophilic materials such as dental adhesives or cement can be challenging. Also, this hydrophobicity may affect the use of PEEK as an implant material. Surface treatment or conditioning is often necessary to improve surface properties. The piranha solution is the treatment of choice to be explored for this purpose. PEEK disks of 10 mm diameter and 2 mm thickness were used in this study. Those samples were divided into five groups (each group has five samples). The first is the control group, in which no acid treatment was used; the second group undergoes sulfuric acid treatment. The remaining three groups were treated with Piranha solution; each group used a different concentration (1 : 3, 1 : 5, and 1 : 7 hydrogen peroxide to sulfuric acid, respectively). The period of treatment was 60 s for all groups. Wettability and surface roughness tests were done for the five groups. In statistical analysis, Shapiro-Wilk test was used to check the assumption of normality and to determine the statistical significance among groups; a one-way analysis of variance was employed. Subsequently, for multiple comparisons, Tukey's honestly significant difference post hoc test was performed. The Piranha solution treatment groups showed a higher wettability compared to the control group and the group treated with sulfuric acid. Additionally, the Piranha solution treatment with a higher concentration of hydrogen peroxide (1 : 3) resulted in greater improvement in surface roughness compared to the control group and the lower concentration groups (1 : 5 and 1 : 7), while the sulfuric acid treated group showed the highest surface roughness. The results of this study suggest that the piranha solution can be an effective method for improving the surface characteristics of PEEK to be used in different dental applications, especially as a dental implant material, due to the increase in wettability and surface roughness.

Evaluation of hydrogen peroxide permeability, color change, and physical-chemical properties on the in-office dental bleaching with different mixing tip.

This study aims to assess hydrogen peroxide (HP) penetration into the pulp chamber, color change (CC), physical-chemical properties, and material wastage (MW) and material used (MU) in mixing tips when using in-office bleaching gels with two different mixing tips. Forty teeth were divided into five groups (n = 8) based on the bleaching gels used (Pola Office +37.5% [PO+] and Whiteness HP Automixx Plus 35% [AM+]) and the mixing tip types (T-Mixer and Helical). A negative control group was treated with ultra-purified water. HP concentration was measured using UV-Vis, and CC was evaluated with a digital spectrophotometer. Initial concentration, pH, and viscosity were measured through Titration, a Digital pH meter, and Rheometer, respectively. MW and MU were measured using a precise analytical balance. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test (α = 0.05). A higher HP concentration was observed with PO+ with the Helical mixing tip in comparison with AM+ (p = 0.01). No significant differences in CC or MU were found for different mixing tips (p = 0.001). The T-mixer mixing tip resulted in significantly less MW (p < 0.00001) and improved mixture homogeneity and viscosity. Utilizing a T-mixer with self-mixing bleaching gels achieves comparable CC while reducing MW. Moreover, it decreases HP penetration when using PO+. For the application of a self-mixing in-office bleaching gel, a T-mixer mixing tip should be recommended, as it reduces the penetration of hydrogen peroxide into the pulp chamber when using PO+, while also minimizing gel wastage.

Oxidation characteristic and thermal runaway of isoprene

In this study, the oxidation characteristics of isoprene were investigated using a custom-designed mini closed pressure vessel test (MCPVT). The results show that isoprene is unstable and polymerization occurs under a nitrogen atmosphere. Under an oxygen atmosphere, the oxidation process of isoprene was divided into three stages: (1) isoprene reacts with oxygen to produce peroxide; (2) Peroxides produce free radicals through thermal decomposition; (3) Free radicals cause complex oxidation and thermal runaway reactions. The oxidation of isoprene conforms to the second-order reaction kinetics, and the activation energy was 86.88 kJ·mol−1. The thermal decomposition characteristics of the total oxidation product and purified peroxide mixture were determined by differential scanning calorimetry (DSC). The initial exothermic temperatures Ton were 371.17 K and 365.84 K, respectively. And the decomposition heat QDSC were 816.66 J·g−1 and 991.08 J·g−1, respectively. It indicates that high concentration of isoprene peroxide has a high risk of thermal runaway. The results of thermal runaway experiment showed that the temperature and pressure of isoprene oxidation were prone to rise rapidly, which indicates that the oxidation reaction was dangerous. The reaction products of isoprene were analyzed by gas chromatography-mass spectrometry (GC–MS). The main oxidation products were methyl vinyl ketone, methacrolein, 3-methylfuran, etc. The main thermal runaway products were dimethoxymethane, 2,3-pentanedione, naphthalene, etc. Based on the reaction products, the possible reaction pathway of isoprene was proposed.

Maintenance of enamel properties after bleaching with high-concentrated hydrogen-peroxide gel containing calcium polyphosphate sub-microparticles.

To assessed the physical and chemical properties of human-enamel after treatment with an experimental bleaching gel containing 35%-hydrogen peroxide (HP) and calcium polyphosphate sub-microparticles (CaPP). Enamel/dentin specimens (4 × 4 × 3mm) were obtained (n = 120) and allocated to different groups: control (saliva only); experimental (HP35%); commercial (whiteness-HP-Maxx); CaPP0.5% (HP35% + CaPP0.5wt%); CaPP1.5% (HP35% + CaPP1.5wt%). Three sessions were performed. The specimens' color was assessed using a spectrophotometer and the color (ΔE/ΔE00) and bleaching index (ΔWID) determined. The surface roughness and microhardness were assessed with a roughness tester and Knoop indenter. Raman spectroscopy was performed to obtain the ratios between the areas under the 431, 580, and 1070cm-1 and the 960cm-1 bands (430:960, 580:960, 1070:960). Kruskal-Wallis and Dunn compared the color, Ra, and SMH data. The Raman data was analyzed with Kruskal-Wallis and Dunn (α = 5%). The ΔE, ΔE00, and ΔWID were similar among the bleached groups (p > 0.05). The roughness was not different between the groups (p > 0.05). After the 3rd session, CaPP0.5% had higher microhardness than the experimental (p < 0.05). The 1070:960 was higher in the experimental than in the CaPP1.5% and control (p < 0.05). In human enamel, CaPP did not alter the bleaching effectiveness or roughness, and additionally, CaPP-containing gels increased the microhardness and preserved the mineral content when compared to the experimental without CaPP. Experimental bleaching gels containing calcium polyphosphate sub-microparticles as a mineral source reduce the mineral content alteration and superficial microhardness reduction, known potential side effects of the in-office bleaching treatments.