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This study developed experimental gels containing titanium tetrafluoride (TiF4) combined with commercial 35% hydrogen peroxide (HP), and evaluated bleaching efficacy and pH of the gels, and mineral content and morphology of enamel...
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This study developed experimental gels containing titanium tetrafluoride (TiF4) combined with commercial 35% hydrogen peroxide (HP), and evaluated bleaching efficacy and pH of the gels, and mineral content and morphology of enamel submitted to these treatments. In phase-1, different stock gels mixed with TiF4 were combined with HP. In phase-2, the selected gels were tested on enamel/dentin specimens (n=8): HP; HP and Natrosol+TiF4 (HPnT); HP and Natrosol+Chemygel+TiF4 (HPncT); HP and Aristoflex+TiF4 (HPaT). Bleaching was performed in four sessions (3x15min-application/session). Color (CIEL*a*b*) and whiteness index (WID) were measured after each session, whereas whiteness index differences (ΔWID), color alteration (CIELab-ΔE, CIEDE2000-ΔE00), enamel morphology and pH, at end of bleaching therapy. The change in Knoop microhardness (ΔKHN) was compared before and after bleaching. Data were analyzed by two-way repeated measures ANOVA and Bonferroni (CIEL*, a*, b*), one-way ANOVA and Tukey (ΔWID, ΔE, ΔE00), and LSD (ΔKHN) tests (α=5%). SEM and pH measurements were submitted to descriptive analysis. No differences were observed in lightness (L*) or WID among the groups (p > 0.05), but HP exhibited lower b* values (p<0.05), higher ΔWID than HPnT, and the highest ΔE among the groups (p < 0.05). No differences in ΔE00 were observed between HP and HPncT (p > 0.05), and HPncT showed higher ΔKHN than HP (p < 0.05). HP presented pH values closer to neutral (6.9), whereas experimental agents showed acidic pH values (2.3-3.9). No morphological changes were observed in HP or HPncT groups. HPncT was able to bleach the enamel and maintain enamel microhardness and surface integrity, even at low pH.
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Understanding the variation in coral bleaching response is necessary for making accurate predictions of population changes and the future state of reefs in a climate of increasing thermal stress events. Individual coral colonies, ...
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Understanding the variation in coral bleaching response is necessary for making accurate predictions of population changes and the future state of reefs in a climate of increasing thermal stress events. Individual coral colonies, belonging to inshore patch reef communities of the Florida Keys, were followed through the 2005 mass bleaching event. Overall, coral bleaching patterns followed an index of accumulated thermal stress more closely than in situ temperature measurements. Eight coral species (Colpophyllia natans, Diploria strigosa, Montastraea cavernosa, M. faveolata, Porites astreoides, P. porites, Siderastrea siderea, and Stephanocoenia intersepta), representing >90% of the coral colonies studied, experienced intense levels of bleaching, but responses varied. Bleaching differed significantly among species: Colpophyllia natans and Diploria strigosa were most susceptible to thermal stress, while Stephanocoenia intersepta was the most tolerant. For colonies of C. natans, M. faveolata, and S. siderea, larger colonies experienced more extensive bleaching than smaller colonies. The inshore patch reef communities of the Florida Keys have historically been dominated by large colonies of Montastraea sp. and Colpophyllia natans. These results provide evidence that colony-level differences can affect bleaching susceptibility in this habitat and suggest that the impact of future thermal stress events may be biased toward larger colonies of dominant reef-building species. Predicted increases in the frequency of mass bleaching and subsequent mortality may therefore result in significant structural shifts of these ecologically important communities.
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The techniques of bleaching process of wool fibers are bleaching with reducing agents bleaching with oxidizing agents bleaching with oxidizing-reducing agents combination. In this study, different chemical bleaching methods have b...
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The techniques of bleaching process of wool fibers are bleaching with reducing agents bleaching with oxidizing agents bleaching with oxidizing-reducing agents combination. In this study, different chemical bleaching methods have been developed as an alternative to the conventional bleaching method. For this purpose, peracetic acid (CH3COOOH, 30%), sodium borohydride (NaBH4), hydrogen peroxide (H2O2, 30%), potassium monopersulfate (KHSO5), sodium dichloroisocyanurate (C3Cl2N3NaO3), oxalic acid (H2C2O4), sodium perborate (NaBO3) calcium hypochlorite (Ca(ClO)(2)) and combination of these chemicals were performed under acidic and basic conditions. Also the environmental impacts were evaluated with measuring wastewaters COD values and surface deformations were analyzed with SEM method.
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Spent Bleaching Earth (SBE) is a by-product of the refining of Crude Palm Oil (CPO) into cooking oil which is classified as hazardous and toxic materials waste. SBE has the potential to be used as a filler in the production of NPK...
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Spent Bleaching Earth (SBE) is a by-product of the refining of Crude Palm Oil (CPO) into cooking oil which is classified as hazardous and toxic materials waste. SBE has the potential to be used as a filler in the production of NPK fertilizer. This study aims to compare the effect of SBE and Deoiled Bleaching Earth (DBE) as the replacement of clay mineral, which is expected to have the same effect as the control treatment in terms of the leaf area, total dry weight, plant height and yield of plant. This experiment used a one-factor Randomized Complete Block Design (RCBD) with three replicates. The treatments of filler in NPK fertilizer were 10% clay minerals, NPK with 5% clay mineral + 5% SBE filler and NPK with 5% clay mineral + 5% DBE filler. Fertilizer was given twice, ie when the plant was 14 days after planting (DAP) as much as 2 g polybag -1 and age 35 DAP as much as 3 g polybag -1 at each treatment. The results showed that the application of NPK fertilization with 5% clay mineral + 5% SBE filler and NPK fertilization with 5% clay mineral + 5% DBE filler had the same effect as NPK fertilization with 10% clay mineral filler on leaf area, total dry weight, plant height and yield of plant. SBE and DBE can be used as substituties for clay mineral in NPK fertilizer production.
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Aim: This in vitro study assessed the efficacy and adverse effects of violet LED bleaching with or without bleaching agents. Material and Methods: Dental blocks (n=40) were randomly distributed in 4 groups: violet LED (VL), 35% hy...
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Aim: This in vitro study assessed the efficacy and adverse effects of violet LED bleaching with or without bleaching agents. Material and Methods: Dental blocks (n=40) were randomly distributed in 4 groups: violet LED (VL), 35% hydrogen peroxide (HP35), the association of hydrogen peroxide 35% with violet LED (VHP35) and the association of hydrogen peroxide 35% with blue LED (BHP35). Specimens were analyzed for Vickers microhardness initially, immediately after and seven days after ending bleaching protocol. The color analysis of the specimens was evaluated for bleaching effectiveness (ΔE2000, AE1976) and whiteness index (ΔWID) with EasyShade spectrophotometer, before bleaching protocol and seven days after ending bleaching protocol. The mineral composition of the enamel was evaluated by percentage of phosphorus and calcium on the enamel surface with energy dispersive spectroscopy (EDS). The color and the microhardness data were analyzed using one-way ANOVA with post-hoc Tukey (α=0.05). Results: The microhardness test showed a difference among the groups only immediately after the completion of the protocol, in which there was a reduction in the value for the groups HP35 from 277,36 ± 21,56 to 198,76 ±32,2 (p＜0.01); and BHP35 from 261,14 ± 36,01 to 212,66 ± 25,99 (p＜0,01), but the microhardness was reestablished after seven days. Regarding EDS analysis, a reduction in the mineral percentage immediately after bleaching with the use of VL was observed, however, after seven days it was reestablished. Regarding the color analysis, there was no difference among the groups evaluated. Conclusions: The use of VL was effective as a dental bleaching tool and did not adversely affect the enamel surface after seven days of the ending of the bleaching protocol.
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Several studies have investigated the effect of bleaching on dental tissues. The evaluation of the effect of home bleaching with 10% carbamide peroxide is important for assessing alterations in enamel microhardness that may affect...
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Several studies have investigated the effect of bleaching on dental tissues. The evaluation of the effect of home bleaching with 10% carbamide peroxide is important for assessing alterations in enamel microhardness that may affect dental health in terms of resistance to masticatory forces. This meta-analysis was performed in order to determine scientific evidence regarding the effects of home vital bleaching with 10% carbamide peroxide gel on the microhardness of human dental enamel. A systematic electronic literature search was conducted in the PubMed and Web of Science databases using search terms. Two independent researchers evaluated the information and methodological quality of the studies. Inclusion and exclusion criteria were established for article selection; further, only studies published in English were selected. Thirteen studies that met all of the inclusion and exclusion criteria were selected and underwent statistical analysis. The results of this meta-analysis showed no significant changes in enamel microhardness when using the 10% carbamide peroxide bleaching gel over periods of 7, 14 and 21 days.
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The bleaching process at the crude palm oil (CPO) refinery stage is one of the processes sufficient to determine the quality of the cooking oil produced. CPO is refined to eliminate the unacceptable substances before consumption. ...
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The bleaching process at the crude palm oil (CPO) refinery stage is one of the processes sufficient to determine the quality of the cooking oil produced. CPO is refined to eliminate the unacceptable substances before consumption. The process produces spent bleaching earth (SBE) and deoiled bleaching earth (DBE) classified as hazardous and toxic material waste. However, according to several studies, SBE and DBE have the potential as filler materials in NPK fertilizers. This study aimed to study the effect of SBE and DBE filler-based NPK fertilization on the soil nutrient status and growth characteristics of soybean, thereby determining if the SBE and DBE materials can be used to replace some of the filler components in the NPK fertilizers. The study was a single factor experiment arranged in?a Randomized Complete Block Design (RCBD) consisting of four blocks as replications. The treatments tested were fertilization of 10% bentonite clay mineral filler-based NPK (control), 5% bentonite clay mineral + 5% SBE filler-based NPK and 5% bentonite clay mineral + 5% DBE filler-based NPK. The data were analyzed using ANOVA and tested using LSD test at a 95% confidence level. The results showed that the SBE and DBE materials could partially replace the filler components in bentonite clay filler-based NPK fertilizers, which were shown to have the same effect on soil chemical properties and levels of heavy metals after treatment, levels and uptake of N, P, K, Ca and Mg in plants tissues and growth characteristic in the form of total dry weight.
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Introduction: Internal bleaching of discolored teeth uses sodium perborate reacting with water to form the active agent, hydrogen peroxide (H2O2). Sodium perborate is replaced at varying time intervals depending on clinician prefe...
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Introduction: Internal bleaching of discolored teeth uses sodium perborate reacting with water to form the active agent, hydrogen peroxide (H2O2). Sodium perborate is replaced at varying time intervals depending on clinician preference and until esthetically acceptable results are achieved, but this is done without scientific basis. This study measured the depletion rate of hydrogen peroxide from sodium perborate as a bleaching agent. Methods: Two sodium perborate bleaching products (Odontobleach (Australian Dental Manufacturing, Kenmore Hills, Queensland, Australia] and Endo sure Perborate Micro [Dentalife, Ringwood, Victoria, Australia]) and distilled deionized water mixtures at ratios of 25 mu g/mL, 50 mu g/mL, and 100 mu g/mL were placed into sealed microtubes and incubated at 37 degrees C. H2O2 concentrations were measured at 23 time points over 4 weeks. Quantification of H2O2 concentrations was obtained using a ferrothiocyanate oxidation reduction reaction followed by spectrophotometry readings. Results: The H2O2 concentration rapidly peaked within 27 hours and reached a plateau by about 3 days (75 hours). Low levels of H2O2 were evident beyond 3 days and for at least 28 days. No significant differences were found between the 2 sodium perborate products. There was also no significant difference in the depletion rate between the different ratios. Conclusions: Based on the chemistry of H2O2 depletion, the minimum replacement interval for the bleaching agent is 3 days. Frequent replacements of the perborate clinically may be unnecessary because of the continued presence of low H2O2 levels for at least 28 days. Although these data cannot be extrapolated to the clinical situation, they set a baseline for further studies to address the many clinical variables influencing internal bleaching.
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The bleach pulp mills have strong social and environmental pressures to eliminate elemental chlorine from the bleach plant. In this capital-intensive industry, mills look for alternatives to chlorine bleaching that are low in capi...
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The bleach pulp mills have strong social and environmental pressures to eliminate elemental chlorine from the bleach plant. In this capital-intensive industry, mills look for alternatives to chlorine bleaching that are low in capital. Some mills have partially replaced chlorine with chlorine dioxide. Many of these mills are considering moving to 100% substitution or D_(100). Depending on the mill, the addition of ClO_2-generation capacity can represent a large investment between $10 million to $25 million. Another alternative to minimize chlorine-dioxide requirements is ozone bleaching. Ozone can be combined with chlorine dioxide in a single stage, commonly referred to as D/Z or Z/D. Many of the North American mills perform the first stage (C/D or D/C or D100) at low pulp consistency. In order to effectively combine ozone with chlorine dioxide in the first stage, application of ozone at low consistency becomes important. Currently there are no such industrial processes. This paper discusses using a simple mixing device already applied in medium consistency mills but at low consistency. It can be easily installed in existing bleach plant and the investment is relatively low at $3 million to $5 million.
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A multi-functional bleaching equipment for laboratory use was developed. The setup allowed the bleaching of four pulp samples at the same time. The bleaching setup works for traditional oxygen and ozone bleaching, using caustic so...
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A multi-functional bleaching equipment for laboratory use was developed. The setup allowed the bleaching of four pulp samples at the same time. The bleaching setup works for traditional oxygen and ozone bleaching, using caustic soda and calcium hydroxides as bleaching additive. This newly developed setup allows creating the tests as flexible as possible, for multiple wood fiber-based pulps. The installation work to change from chemical to gas bleaching can be done in a couple of minutes. The new trial setup showed improvements for the second and third bleaching stage using oxygen and ozone gas. For Kraft pulp using caustic soda as bleaching agent the Kappa number could be reduced by over 97.8%. Calcium hydroxide as bleaching agent resulted in a reduction of 90.0%. Both bleaching agents allowed an increase in L* brightness and tensile index of up to 74.1% and 80.1%% respectively for caustic soda and 17.6% and 80.1% respectively for calcium hydroxide as bleaching agent. For straw and coffee filter pulp an increase in L* brightness of up to 58.6% and an increase of the tensile index of up to 67.0% could be achieved without using bleaching agents. Recycled pulp showed an increase in tensile index of up to 71.5% but a decrease of 1% for the L* brightness.
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