Effect of hydrogen peroxide concentration on enamel color and microhardness

Objectives: The aim of this study was to investigate the effect of hydrogen peroxide gels with different concentrations (20%, 25%, 30%, and 35%) on enamel Knoop microhardness (KNIT) as well as on changes in dental color (C).Methods: Cylindrical specimens of enamel/dentin (3-nun diameter and 2-nun thickness) were obtained from bovine incisors and randomly divided into six groups (n=20), according to the concentration of the whitening gel (20%, 25%, 30%, 35%, control, thickener). After polishing, initial values of KNH0 and color measurement, assessed by spectrophotometry using the CIE L*a*b* system, were taken from the enamel surface. The gels were applied on the enamel surface for 30 minutes, and immediate values of KNHi were taken. After seven days of being stored in artificial saliva, new measures of KNH7 and color (L-7* a(7)* b(7)*, for calculating Delta E, Delta L, and Delta b) were made. Data were submitted to statistical analysis of variance, followed by Tukey test (p<0.05).Results: Differences in gel concentration and time did not influence the microhardness (p=0.54 and p=0.29, respectively). In relation to color changes, Delta E data showed that the 35% gel presented a higher color alteration than the 20% gel did (p=0.006).Conclusion: Bleaching with 35% hydrogen peroxide gel was more effective than with the 20% gel, without promoting significant adverse effects on enamel surface microhardness.

Caracterização física e química dos frutos nos diferentes quadrantes da planta e germinação de sementes do portaenxerto cítrico tangerineira ‘sunki’

The tangerine 'Sunki' are highly relevant for the Brazilian citrus industry by presenting important traits for genetic improvement and to be considered a great portaenxento. In this context, the objective of the present work to study the characterization of the fruits of citrus rootstock 'Sunki', depending on the position on the plan and also the germination of their seeds. The physical characteristics evaluated were fruit weight, longitudinal and equatorial diameters of the fruit longitudinal diameter / equatorial diameter, number of buds per fruit, weight of buds and bark and number of viable seeds per fruit. As for the chemical characterization was evaluated titratable, acidity, soluble solid, "Ratio", pH and vitamin C. For the evaluation of these variables, the fruits were obtained from the northeast, southwest, northwest and southeast quadrants. Regarding the evaluation of seed germination, different doses of gibberellic acid and Stimulate were used. The seeds extracted from ripe fruit, washed, dried in the shade and stored in BOD. Immediately after, they were treated for 24 hours with plant growth regulators. After soaking, the seeds were placed in a germinator in germitest paper. After initiation of the germination process, the evaluations were performed daily until the thirty- fourth day. Fruits of 'Sunki'mandarin with uneven as the fruit position within the canopy, the use of gibberellic acid and growth promoter is promising for commercial use on seed germination of this rootstock.

Adubação nitrogenada e potássica em goiabeiras ‘paluma’: I. efeito na produtividade e na qualidade dos frutos para industrialização

The nutrition of the orchards is the major factor of productivity, being necessary to know the proper doses of fertilizers and their influence on fruit quality attributes for industrialization. This study evaluated the effects of different doses of nitrogen and potassium on the productivity of guava trees and also on the values of pH, soluble solids (SS), titratable acidity (TA) and pulp/kernel ratio of guavas. The experiment was conducted at Vista Alegre do Alto, SP in an irrigated 'Paluma'guava orchard, 7 years old, managed with pruning during three consecutive cycles of production. The soil of the area was dystrophic Ultisol. The experimental design was the randomized blocks, in factorial, with four nitrogen doses (0, 0.5, 1 and 2 kg of N plant(-1)) and four of potassium (0, 0.55, 1.1 and 2.2 kg of K2O plant(-1)), with three replications. Nitrogen fertilization increased productivity and the pH of the fruit, being explained by the quadratic polynomial regression models; reduced linearly the pulp/kernel ratio and do not influenced the SS and TA values. On the other hand, potassium fertilization and N x K interaction had no significant effects on productivity and the other characteristics evaluated.

Tropical soils with high aluminum concentrations cause oxidative stress in two tomato genotypes

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

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)

Qualidade de cebola minimamente processada em diferentes tipos de cortes

The high perishability of the onion has limited its conservation period and caused great post-harvest losses. The need of consuming fresh products has led the market of minimally processed products to considerably rise. Cut operations during the minimal processing may not only cause important biochemical reactions in the onion tissues, but also affect its sensorial quality, resulting in a drastic reduction in the post-harvest life of the product. In this study the influence of different cut types was assessed on the quality of minimally processed onions. 'Baia Periforme'onions were transported to the laboratory, where they were selected, cleaned, classified, peeled, minimally processed into slices, grated and chopped, and subsequently sanitized for 10 minutes in sodium hypochlorite at 100 mg L-1. The product was kept on polystyrene trays covered with plastic film (PVC) as 80 g portions and conserved in a cold chamber at 5 +/- 1 degrees C and 85 +/- 5% RH, during 6 days. Physical, chemical and physico-chemical assays were carried out. Statistical design was completely randomized with 3 treatments and 3 replications (plot group) and 5 replicationss for the control group. For sensorial analysis (aspect and smell), 10 replications were used. To compare means, Tukey test at 5% significance was adopted. During the refrigerated conservation, sliced onions kept more stable levels of soluble solids, titratable acidity, total sugars, reducing and non-reducing sugars. The grated onion was superior considering the sensorial characteristics, indicating that the cut types interfered in these features and the grated onion was more accepted by evaluators.

Uso de ácido ascórbico e cloreto de cálcio na qualidade de repolho minimamente processado

The objective of this trial was to evaluate the effect of ascorbic acid (AA) and calcium chloride (CaCl2) applied by immersion at temperatures of 20 and 40 degrees C on the physicochemical and sensory characteristics of minimally processed cabbage, stored under refrigeration. Cabbages were processed in an industrial food processing equipment to be cut in slices with thickness of 3 mm. Slices were immersed in sodium hypochlorite (50 ppm) during 5 minutes for sanitization. After, the following treatments were carried out T1= control (immersion in water during 5 minutes at 20 degrees C); T2= immersion in 1% AA solution, during 5 minutes at 20 degrees C; T3= immersion in 2% AA solution, during 5 minutes at 20 degrees C; T4= immersion in 1% CaCl2 solution during 5 minutes at 20 degrees C; T5= immersion in 2% CaCl2 solution during 5 minutes at 20 degrees C, T6= immersion in 1% CaCl2 solution during 5 minutes at 40 degrees C; and T7= immersion in 2% CaCl2 solution during 5 minutes at 40 degrees C; with four replications each one. After application of treatments, cabbage was centrifuged during one minute, wrapped with polyvinyl chloride, 20 mu m, in trays of expanded polystyrene and maintained in refrigerated environment, at 6 +/- 1 degrees C and 85-90% of relative humidity, during eight days. Little increasing was observed in pH and titratable acidity values and reduction in soluble solids during conservation period on all treatments. Treatment with AA did not differ from control for color and general appearance, while treatment with 2% CaCl2 at 20 degrees C maintained the best quality, with less intensity of browning, best general appearance and purchase intent and least strange odor at the end of evaluation period.

Effect of intermittent drying and storage on parchment coffee quality

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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.