Carbon-supported TiO2-Au hybrids as catalysts for the electrogeneration of hydrogen peroxide: Investigating the effect of TiO2 shape

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

Penetration of 35% hydrogen peroxide into the pulp chamber in bovine teeth after LED or Nd:YAG laser activation

This aim of the present study was to evaluate the pulp chamber penetration of 35% hydrogen peroxide activated by LED (light-emitting diode) or Nd:YAG laser in bovine teeth, after an in-office bleaching technique. Forty-eight bovine lateral incisors were divided into four groups, acetate buffer was placed into the pulp chamber and bleaching agent was applied as follows: for group A (n = 12), activation was performed by LED; for group B (n = 12), activation was performed by Nd:YAG laser (60 mJ, 20 Hz); group C (n = 12) received no light or laser activation; and the control group (n = 12) received no bleaching gel application or light or laser activation. The acetate buffer solution was transferred to a glass tube and Leuco Crystal Violet and horseradish peroxidase were added, producing a blue solution. The optical density of this solution was determined spectrophotometrically and converted into microgram equivalents of hydrogen peroxide. The results were analysed using ANOVA and Tukey's test (5%). It was verified that the effect of activation was significant, as groups activated by LED or laser presented greater hydrogen peroxide penetration into the pulp chamber (0.499 +/- 0.622 microg) compared with groups that were not (0.198 +/- 0.218 microg). There was no statistically significant difference in the penetration of hydrogen peroxide into the pulp chamber between the two types of activation (LED or laser). The results suggest that activation by laser or LED caused an increase in hydrogen peroxide penetration into the pulp chamber.

Effect of chemical activation of 10% carbamide peroxide gel in tooth bleaching

This study aimed to evaluate the efficacy of chemical agents to increase the bleaching effectiveness of 10% carbamide peroxide. Two hundred and ninety enamel-dentin discs were prepared from bovine incisors. The color measurement was performed by a spectrophotometer using the CIE L*a*b*system. The groups were divided according to the bleaching treatment: negative control group (NC): without bleaching; positive control group (PC): bleached with 10% carbamide peroxide gel without any chemical activator; Manganese gluconate (MG); Manganese chloride (MC); Ferrous gluconate (FG); Ferric chloride (FC); and Ferrous sulphate (FS). Three different concentrations (MG, MC, FG, FC: 0.01, 0.02 and 0.03% w/w; FS: 0.001, 0.002 and 0.003% w/w) for each agent were tested. The bleaching gel was applied on the specimens for 8 h, after which they were immersed in artificial saliva for 16 h, during 14 days. Color assessments were made after 7 and 14 days. The data were analyzed by repeated measures analysis of variance and Tukey's test (5%). Generally, the test groups were unable to increase the bleaching effect (ΔE) significantly compared to the PC group. Only for ΔL, significant higher values compared to the PC group could be seen after 7 days in groups MG (0.02%), and FS (0.002 and 0.003%). The NC group showed significantly lower values than all tested groups. It was concluded that for home bleaching procedures, the addition of chemical activators did not produce a bleaching result significantly higher than the use of 10% carbamide peroxide without activation, and that the concentration of chemical activators used did not significantly influence the effectiveness of treatment.

Demineralization and hydrogen peroxide penetration in teeth with incipient lesions

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

Effectiveness of 6% hydrogen peroxide concentration for tooth bleaching-A double-blind, randomized clinical trial

The aim of this clinical randomized double-blind split-mouth study was to assess the effectiveness of a 6% hydrogen peroxide with nitrogen-doped titanium dioxide light activated bleaching agent. 31 patients were treated with: one upper hemiarcade with a 35% hydrogen peroxide bleaching agent and the other hemiarcade with a 6% hydrogen peroxide. Two applications were completed each treatment session and three sessions were appointed, with one week interval between them. Tooth colour was registered each session and 1 week and 1 months after completing the treatment by spectrophotometer, registering parameters L*, a* and b*, and subjectively using VITA Classic guide. Tooth sensitivity was registered by VAS and patient satisfaction and self-perception result was determined using OHIP-14. Tooth colour variation and sensitivity were compared between both bleaching agents. Both treatment showed a change between baseline colour and all check-points with a ΔE=5.57 for 6% and of ΔE=7.98 for the 35% one month after completing the (p<0.05). No statistical differences were seen when subjective evaluations were compared. Also, no differences were seen in tooth sensitivity between bleaching agents. OHIP-14 questionnaire demonstrated a significant change for all patients after bleaching. A 6% hydrogen peroxide with nitrogen-doped titanium dioxide light activated agent is effective for tooth bleaching, reaching a ΔE of 5.57 one month after completing the treatment, with no clinical differences to a 35% agent neither in colour change or in tooth sensitivity. A low concentration hydrogen peroxide bleaching agent may reach good clinical results with less adverse effects.

Hydrogen peroxide centrally attenuates hyperosmolarity-induced thirst and natriuresis

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

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

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

Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inhibitory effect of gallic acid and its esters on 2,2'-azobis(2-amidinopropane)hodrpchloride (AAPH)-induced hemolysis and depletion of intracellular glutathione in erythrocytes

The protective effect of gallic acid and its esters, methyl, propyl, and lauryl gallate, against 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH)-induced hemolysis and depletion of intracellular glutathione (GSH) in erythrocytes was studied. The inhibition of hemolysis was dose-dependent, and the esters were significantly more effective than gallic acid. Gallic acid and its esters were compared with regard to their reactivity to free radicals, using the DPPH and AAPH/pyranine free-cell assays, and no significant difference was obtained. Gallic acid and its esters not only failed to inhibit the depletion of intracellular GSH in erythrocytes induced by AAPH but exacerbated it. Similarly, the oxidation of GSH by AAPH or horseradish peroxidase/H(2)O(2) in cell-free systems was exacerbated by gallic acid or gallates. This property could be involved in the recent findings on pro-apoptotic and pro-oxidant activities of gallates in tumor cells. We provide evidence that lipophilicity and not only radical scavenger potency is an important factor regarding the efficiency of antihemolytic substances.

Thermoanalytical study of cassava starch native and treated with hydrogen peroxide

Starch is one of the most important sources of reserve of carbohydrate in plants and the main source in the human diet due to its abundance in the nature. There no other food ingredient that can be compared with starch in terms of sheer versatility of application in the food industry. Unprocessed native starches are structurally too weak and functionally too restricted for application in today’s advanced food and industrial technologies. The main objective of this study was to compare the thermal behavior of native cassava starch and those treated with hydrogen peroxide, as well as those treated with hydrogen peroxide and ferrous sulfate. The cassava starch was extracted from cassava roots (Manihot esculenta, Crantz) and treated by standardized hydrogen peroxide (H2 O2 ) solutions at 1, 2 and 3% (with or without FeSO4 ). Investigated by using they are thermoanalytical techniques: thermogravimetry - TG, differential thermal analysis – DTA and differential scanning calorimetry - DSC, as well as optical microscopy and X-ray powder diffractometry. The results showed the steps of thermal decomposition, changes in temperatures and in gelatinization enthalpy and small changes in crystallinity of the granules.

Can hydrogen peroxide and quercetin improve production of Eucalyptus grandis x Eucalyptus urophylla?

Vegetative propagation is considered the best choice for the rapid multiplication of plant species, however, rooting may still present difficulties. Substances, such as auxins, phenolic compounds and hydrogen peroxide, are recognized as able to improve this process. The aim of the present work was to determine if hydrogen peroxide in combination with quercetin or indole butyric acid, can modify some characteristics related to rooting and development in cuttings of Eucalyptus grandis x Eucalyptus urophylla. Cuttings were periodically evaluated at 30, 60 and 90 days according to the following criteria: height, diameter and survival percentage. After planting (90 days), a destructive evaluation was performed to determine rooting percentage, average size and number of roots. Polyamines content and polyamine oxidase activity, as biochemical markers of plant development, were determined. No statistically significant differences in height, diameter, survival and rooting percentage, root length and number of roots per cuttings were found. Treatments induced a decrease in putrescine levels and polyamine oxidase activity in roots. For absence of positive responses, the use of these substances as a treatment to improve cutting production is economically unviable.