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Introdução:A sensibilidade dentária é o efeito adverso mais comum relacionado ao clareamento dentário. Na técnica de consultório, o peróxido de carbamida a 37%, surgiu como possibilidade de clarear e não causar sensibilidade.Objetivo:trata-se deum relato de caso, que avaliou a eficácia (mudança de cor) e a presença ou não de sensibilidade dentária quando se fezo uso de um produto àbase de peróxido de hidrogênio a35% e outro de peróxido de carbamida a 37%, na técnica de clareamento dentário de consultório.Relato de caso:Paciente de25 anos, sexo masculino, submetido a estudo de boca dividida, onde no hemiarco esquerdo foi aplicado peróxido de hidrogênio a 35% e no hemiarco direito, peróxido de carbamida a 37%. Foram feitas 3 sessões, sendo Peróxido de Carbamidacom aplicação única de 45 minutos, e Peróxido de Hidrogêniocom 3 aplicações de 15 minutos, em seu respectivo lado de aplicação e intervalo de sete dias entre cada sessão. Os valores de sensibilidade foram analisados antes e depois de cada sessão por meio da escala visual analógica de dor, e a alteração de cor foi avaliada através da Escala Vita, analisando incisivos e caninos superiores, antes de cada sessão.Conclusões:O clareamento dental com o Peróxido de Hidrogênio apresentou melhor eficácia clareadora e o Peróxido de Carbamida apresentou ausência de sensibilidade durante o procedimento clareador. Sugerem-se mais estudos do tipo ensaio clínico, com o Peróxido de Carbamida, para que se possa, com uma amostra maior de pacientes, verificar suas vantagens no quesito sensibilidade, bem como sua efetividade clareadora (AU).

Introduction:Tooth sensitivity is the most common adverse effect related to tooth bleaching. In the in-office technique, 37% carbamide peroxide has emerged as a way of tooth bleaching which does not cause sensitivity.Objective:This paper consists of a case report that evaluated the efficacy (color change) and the presence or absence of tooth sensitivity when using a product based on 35% hydrogen peroxide and another product based on 37% carbamide peroxide in the in-office tooth bleaching technique.Case report:A 25-year-old male patient underwent a split-mouth study in which 35% hydrogen peroxide was applied to the left hemi-arch and 37% carbamide peroxide to the right hemi-arch. Three sessions were carried out, carbamide peroxide with a single 45-minute application, and hydrogen peroxide with three 15-minute applications, on their respective application side and with a seven-day interval between each session. Sensitivity values were analyzed before and after each session using the visual analogue pain scale, and color change was assessed using the Vita Scale, analyzing upper incisors andcanines before each session. Conclusions:Teeth bleaching with hydrogen peroxide showed better bleaching efficacy and carbamide peroxide showed no sensitivity during the bleaching procedure. Further clinical trials with carbamide peroxide are suggested inorder to verify, with a larger sample of patients, its advantages in terms of sensitivity, as well asits bleaching effectiveness (AU).

Introducción: La sensibilidad de la dentina es el efecto adverso más común relacionado con el blanqueamiento dental. En la técnica en clínica, el peróxido de carbamida al 37% ha surgido como una posibilidad de blanqueamiento sin causar sensibilidad.Objetivo: Se tratade un informe de caso que evaluó la eficacia (cambio de color) y la presencia o ausencia de sensibilidad de la denina al utilizar un producto a base de peróxido de hidrógeno al 35% y otro a base de peróxido de carbamida al 37% en la técnica de blanqueamiento dental en clínica.Informe de caso:Un paciente del sexo maculino de 25 años fue sometido a un estudio de boca dividida en el que se aplicó peróxido de hidrógeno al 35% en la hemiarcada izquierda y peróxido de carbamida al 37% en la hemiarcada derecha.Se realizaron tres sesiones, la peróxido de carbamida con una única aplicación de 45 minutos, y la peróxido de hidrógeno con tres aplicaciones de 15 minutos, en sus respectivos lados de aplicación y con un intervalo de siete días entre cada sesión. Se analizaron los valores de sensibilidad antes y después de cada sesión mediante la escala analógica visual del dolor, y se evaluó el cambio de color mediante la Escala Vita, analizando los incisivos superiores y los caninos antes de cada sesión. Conclusiones: El blanqueamiento dental con peróxido de hidrógeno demostró una mayor eficacia blanqueadora y el peróxido de carbamida no manifestó sensibilidad durante el procedimiento de blanqueamiento. Se sugiere realizar más ensayos clínicos con peróxido de carbamidaparapoder utilizar una muestra mayor de pacientes y verificar sus ventajas en términos de sensibilidad, así como su eficacia blanqueadora (AU).

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OBJECTIVE: To compare the color change, the risk and intensity of tooth sensitivity (TS), and gingival irritation (GI) of at-home bleaching applied on the buccal surface only or the buccal and lingual surfaces. MATERIALS AND METHODS: Sixty patients with canines A2 or darker were selected and their superior arches were randomized in two groups: at-home bleaching on the buccal-only or on the buccal and lingual surfaces, with 7.5% hydrogen peroxide, for 1 h daily/2 weeks. The color change was evaluated at baseline, 7, 14 days, and 1 month after bleaching using shade guides scales (ΔSGU) and a spectrophotometer (ΔEAB, ΔE00, and ΔWID). Risk and intensity of TS and GI were recorded daily using visual analogic scale (0-10). Patient satisfaction was evaluated with the orofacial esthetics. Paired t-test, McNemar's, and Wilcoxon signed-rank test were used for data analysis (α = 5%). RESULTS: Neither the color change nor the risk/intensity of TS was statistically different between groups (p > 0.05). Patient satisfaction increased after bleaching for both groups (p < 0.05). CONCLUSION: The addition of one contact surface does not result in an increased whitening degree compared to bleaching applied solely on the buccal surface. CLINICAL SIGNIFICANCE: Understanding the influence of surfaces interacting with the bleaching agent is crucial for comprehending the bleaching mechanism and avoiding unnecessary material expenses. Notably, employing the buccal-only technique is sufficient to achieve the desired efficacy.

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Monoxenous trypanosomatid Strigomonas culicis harbors an endosymbiotic bacterium, which enables the protozoa to survive without heme supplementation. The impact of H2O2 resistance and symbiont elimination on intracellular heme and Fe2+ availability was analyzed through a comparison of WT strain with both WT H2O2-resistant (WTR) and aposymbiotic (Apo) protozoa. The relative quantification of the heme biosynthetic pathway through label-free parallel reaction monitoring targeted mass spectrometry revealed that H2O2 resistance does not influence the abundance of tryptic peptides. However, the Apo strain showed increased coproporphyrinogen III oxidase and ferrochelatase levels. A putative ferrous iron transporter, homologous to LIT1 and TcIT from Leishmania major and Trypanosoma cruzi, was identified for the first time. Label-free parallel reaction monitoring targeted mass spectrometry also showed that S. culicis Iron Transporter (ScIT) increased 1.6- and 16.4-fold in WTR and Apo strains compared to WT. Accordingly, antibody-mediated blockage of ScIT decreased by 28.0% and 40.0% intracellular Fe2+concentration in both WTR and Apo strains, whereas no effect was detected in WT. In a heme-depleted medium, adding 10 µM hemin decreased ScIT transcript levels in Apo, whereas 10 µM PPIX, the substrate of ferrochelatase, increased intracellular Fe2+ concentration and ferric iron reduction. Overall, the data suggest mechanisms dependent on de novo heme synthesis (and its substrates) in the Apo strain to overcome reduced heme availability. Given the importance of heme and Fe2+ as cofactors in metabolic pathways, including oxidative phosphorylation and antioxidant systems, this study provides novel mechanistic insights associated with H2O2 resistance in S. culicis.

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Hydrogen peroxide (H2O2) transport by aquaporins is a critical feature for cellular redox signaling. However, the H2O2 permeation mechanism through these channels remains poorly understood. Through functional assays, two Plasma membrane Intrinsic Protein (PIP) aquaporins from Medicago truncatula, MtPIP2;2 and MtPIP2;3 have been identified as pH-gated channels capable of facilitating the permeation of both water (H2O) and H2O2. Employing a combination of unbiased and enhanced sampling molecular dynamics simulations, we investigated the key barriers and translocation mechanisms governing H2O2 permeation through these aquaporins in both open and closed conformational states. Our findings reveal that both H2Oand H2O2 encounter their primary permeation barrier within the selectivity filter (SF) region of MtPIP2;3. In addition to the SF barrier, a second energetic barrier at the NPA (asparagine-proline-alanine) region that is more restrictive for the passage of H2O2 than for H2O, was found. This behavior can be attributed to a dissimilar geometric arrangement and hydrogen bonding profile between both molecules in this area. Collectively, these findings suggest mechanistic heterogeneity in H2Oand H2O2 permeation through PIPs.

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This study evaluated the photoactivation of hydrogen peroxide gels at different concentrations using blue or violet LED in terms of whitening efficacy and tooth sensitivity. Forty patients were randomly divided into 4 groups: HP6V (violet LED and 6% hydrogen peroxide), HP6B (blue LED and 6% hydrogen peroxide), HP35V (violet LED and 35% hydrogen peroxide), and HP35B (blue LED and 35% hydrogen peroxide). The L*, a* and b* values were measured before, 1 week and 3 months after treatment, and the ΔE and ΔWID values were calculated. Tooth sensitivity was measured using a visual analogue scale (VAS) before, immediately after, and 24 h after bleaching. The ΔE, ΔWID and bleaching sensitivity values were subjected to the ANOVA test and Bonferroni post-test. HP35V and HP35B showed higher whitening efficacy than HP6VL, while HP6V did not show statistical differences compared to the other groups. Regarding bleaching-related sensitivity, the HP6V and HP6B groups presented the lowest values when compared to HP35V and HP35B. HP6V showed whitening efficacy comparable to HP35V and HP35B but with reduced tooth sensitivity. TRIAL REGISTRATION NUMBER: NCT06165458; registration date: 12/09/2023.

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OBJECTIVE: Evaluate the penetration of hydrogen peroxide (HP) into the pulp chamber, bleaching efficacy (BE) and amount of gel expended during in-office bleaching using an applicator brush tip and conventional tip from different commercial brands. MATERIALS AND METHODS: 104 human premolars were randomly distributed into thirteen groups (n = 8) according to the commercial brand: DSP White Clinic 35 % Calcium (DW), Nano White 35 % (NW), Total Blanc One-Step 35 % (TS), Whiteness HP Blue 35 % (WB), Potenza Bianco Pro SS 38 % (PB), Opalescence XTra Boost 40 % (OB), no bleaching (negative control), and application method: applicator brush tip and conventional tip for all groups. Initial HP concentration (%) was determined via titration and pH was measured with digital pH meter. Concentration (µg/mL) of HP into the pulp chamber was measured using UV-Vis spectrophotometry, the BE (ΔE*ab, ΔE00 and ΔWID) was evaluated with a digital spectrophotometer, and the amount of gel expended was evaluated using a precision analytical digital balance. Statistical analysis included two-way ANOVA, Tukey's, and Dunnett's test. Comparison between HP into the pulp chamber vs BE was performed with Person's correlation (α = 0.05). RESULTS: Brush tip demonstrated a low amount of HP in the pulp chamber compared to the conventional method for all bleaching gels (p < 0.0003), as well as lower amount of gel expended (p < 0.002). The brush tip did not result in a significant difference in BE compared to the conventional (p > 0.05). No correlations were found between both factors (p > 0.05). CONCLUSION: Brush tip showed lower penetration of HP in the pulp chamber and a reduced volume of spent gel when compared to the conventional tip, for all commercial brands. CLINICAL RELEVANCE: Brush tip is recommended for bleaching gels in an attachable syringe due to its ability to reduce the penetration of HP into the pulp chamber and minimize the amount of bleaching gel used.

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OBJECTIVES: To evaluate the effect of whitening toothpastes with different hydrogen peroxide (HP) concentrations on HP permeability, color change, and physicochemical properties, compared to at-home bleaching treatment. MATERIALS AND METHODS: Forty-nine premolars were randomized into seven groups (n = 7): untreated (control); at-home bleaching with 10% carbamide peroxide gel (AH; 10% CP) with 14 and 28 applications of 180 min each (AH [14 × 180 min] and AH [28 × 180 min]); three whitening toothpastes (3% HP; 4% HP and 5% HP) and 10% CP brushed 28 times for 90 s each (TB [28 × 90 s]). HP permeability was measured using a UV-VIS spectrophotometer and color change by a digital spectrophotometer (ΔEab, ΔE00, and ΔWID). Initial concentration, pH, and viscosity were measured through titration, digital pH meter, and rheometer, respectively. Statistical analysis included one-way ANOVA, Tukey's test, and Dunnett's test (α = 0.05). RESULTS: 4% HP group showed acidic pH, the lowest viscosity and the highest HP concentration into the pulp chamber (p < 0.05). The 10% CP groups had lower HP in the pulp chamber and greater color change than other groups (p < 0.05), except the 5% HP group in ΔEab and ΔE00. For ΔWID, the 10% CP AH groups showed greater whitening than other groups (p < 0.05). CONCLUSIONS: Whitening toothpaste with up to 5% HP resulted in higher HP permeability and less color change compared to 10% CP. Higher HP commercial concentrations in toothpaste increased whitening effect; however, acidic pH toothpastes exhibited greater HP permeability. CLINICAL RELEVANCE: Whitening toothpastes with high hydrogen peroxide concentrations were less effective than at-home bleaching, resulting in less color change and greater permeability of hydrogen peroxide, potentially increasing the risk of tooth sensitivity.

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BACKGROUND: To evaluate the decomposition rate of active hydrogen peroxide (HP) and bleaching efficacy during in-office bleaching using high-concentration HP gels with different pHs. METHOD: A randomized, parallel, double-blind controlled trial was conducted with 40 volunteers randomized into four groups (pH 5.4; pH 7.0; pH 7.7, and pH 8.0). During the first session in-office bleaching, approximately 0.01 g of the gel was collected and titrated with potassium permanganate to obtain the concentration of active HP and pH values were measured using an electrode. Bleaching efficacy was assessed using a spectrophotometer [∆Eab, ∆E00, and WID], Vita Classical and Vita Bleachedguide scales [∆SGU]. The decomposition rate of HP concentration and pH values change were calculated using ANOVA one-way. The bleaching efficacy was assessed using two-way repeated measures ANOVA. Tukey's test was applied as a post-hoc test (p < 0.05). RESULTS: All gels experienced decreasing HP concentration over time. pH 5.4 gel showed greatest reduction after 50 min (p < 0.001). pH 8.0 and 7.7 gels remained stable; pH 5.4 remained acidic, while pH 7.0 turned acidic (p < 0.001). No significant difference in bleaching degree was observed among gels. They all showed a similar and clinically important color change after two clinical sessions, remained stable 1-month post-treatment (p > 0.05). CONCLUSIONS: All bleaching gels kept at least 70% of their HP content after 50 min, suggesting that there is a surplus of HP. They provided similar whitening efficacy 1-month after bleaching. PRACTICAL IMPLICATIONS: It is possible that lower HP concentrations may be equally effective in achieving desired results while reducing the potential for side effects. CLINICAL TRIAL REGISTRY NAME: RBR-35q7s3v.

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To assess the effect of bleaching with gel of pregabalin associated with 35% hydrogen peroxide on the mechanical and chemical properties and ultramorphology of dental enamel. Thirty-six (36) specimens of bovine dental incisors were obtained and divided into three groups (n = 12), namely: CG = bleaching with 35% hydrogen peroxide; KFG = bleaching with 5% potassium nitrate and 2% sodium fluoride gel + 35% hydrogen peroxide; and PGG = bleaching with experimental gel of pregabalin + 35% hydrogen peroxide. The specimens were assessed with respect to Knoop microhardness, surface roughness, and colour change, before and after bleaching. They were also assessed using scanning electron microscopy and energy-dispersive spectroscopy after treatments. All groups exhibited an increase in surface roughness and a reduction in Knoop microhardness after the protocols. There was colour change in all groups, with no difference between them. In addition, there were changes in enamel morphology and non-significant loss of calcium and phosphorus. The experimental gel of pregabalin did not influence the action of 35% hydrogen peroxide, yielding results similar to those of the other groups assessed in all the parameters. Therefore, the gel of pregabalin can be an alternative for topical application on the surfaces of the teeth in association with bleaching treatments.

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Catalases are essential enzymes for removal of hydrogen peroxide, enabling aerobic and anaerobic metabolism in an oxygenated atmosphere. Monofunctional heme catalases, catalase-peroxidases, and manganese catalases, evolved independently more than two billion years ago, constituting a classic example of convergent evolution. Herein, the diversity of catalase sequences is analyzed through sequence similarity networks, providing the context for sequence distribution of major catalase families, and showing that many divergent catalase families remain to be experimentally studied.

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