Effect Of Bleaching Treatment Research Articles

Bleached rice straw lignin: Thermal-chemical properties and its application in polyurethane-based paper coatings

Rice straw lignin (LRS) tends to be dark in color, which makes it less appealing for material applications. Therefore, a bleaching process involving lignin oxidation is of interest. This study aimed to investigate the mechanical and chemical properties of bleached LRS and explore its potential application in PU-based paper coatings. LRS and commercial lignin (LC) were subjected to bleaching using 29% H2O2 through oxidation treatment. The bleached lignin was then used to prepare PU-based paper coatings. The effects of bleaching treatment on the functional groups, structural, and thermal properties of lignin, as well as the water resistance of the PU composites were assessed. The oxidation treatment resulted in a reduction in the phenolic hydroxyl content, methoxy content, antioxidant activity, and equivalent weight of lignin. However, LRS exhibited greater thermal resistance than did LC. The bleached LRS was successfully integrated with toluene di-isocyanate (TDI) to produce transparent polyurethane. This polyurethane was then applied as a coating for paper containers, which successfully held cold water for over 4 h without leaking, indicating its outstanding water repellency.

Effect of Bleaching Treatments on the Mechanical Properties of the Dentin Matrix and on Collagen Biodegradation by Endogenous Protease.

This study evaluated the mechanical properties of demineralized dentin matrix submitted to different bleaching treatments, as well as the changes in mass and collagen biodegradation brought about by endogenous protease. Dentin collagen matrices were prepared to receive the following treatments (n=12): no bleaching treatment (C-control), 10% carbamide peroxide (CP-Opalescence PF, Ultradent, South Jordan, UT, USA) 10%/8 hours/ day/14 days, and 40% hydrogen peroxide (HP-Opalescence Boost, Ultradent), 40 minutes per session/3 sessions. The dentin matrices were evaluated for elastic modulus and mass before and after treatments and ultimate tensile strength after treatments. The solution collected during storage was evaluated for hydroxyproline release. There was no statistically significant difference between CP and C in terms of the elastic modulus (p=0.3697) or mass variation (p=0.1333). Dentin beams treated with HP and C presented significant mass loss after the first session (p=0.0003). HP treatment led to complete degradation of collagen matrices after the second bleaching session. After the second session, CP showed higher hydroxyproline concentration than C (p<0.0001). Ultimate tensile strength was lower for CP than C (p=0.0097). CP did not affect the elastic modulus or the dentin collagen matrix mass but did promote hydroxyproline release by endogenous protease and reduce the ultimate tensile strength. HP significantly affected the mechanical properties of dentin and promoted complete degradation of the demineralized dentin collagen matrix.

Effects of bleaching treatment on the properties of bio-polyurethane films from liquefied bamboo

Malaysian bamboo residues were subjected to a liquefaction process. Bleaching of the liquefied product was carried out to reduce its coloration. Polyurethane (PU) films were then manufactured as a coating material by reacting the -OH groups in the bamboo material with isocyanate (-NCO). The study’s objective was to investigate the effects of bleaching on the properties of resulting polyurethane films and to elucidate its behavior as affected by the NCO/OH ratios. Bamboo residues, in powder form, were liquefied with polyethylene glycol (PEG 400) and glycerol (Gly) as reactive co-solvent, and sulphuric acid as catalyst. The obtained liquefied bamboo was then bleached with hydrogen peroxide. Bleached and unbleached liquefied bamboo were used to produce PU film by reacting isocyanate at NCO/OH ratios of 1.6, 1.8, 2.0, and 2.2. The results revealed that the NCO/OH ratios improved the mechanical performance of the PU films. Bleaching treatment slightly reduced the thermal stability and mechanical strength of the PU films. However, bleached PU films displayed lower water absorption and lower biodegradation than unbleached PU films. Nevertheless, the performance of the bleached PU films was still acceptable, indicating that the bleaching treatment using hydrogen peroxide is feasible to obtain semi-transparent film.

Preliminary Study on the Effect of Bleaching Treatment on Cellulose Extracts from Oil Palm Empty Fruit Bunch

Oil palm empty fruit bunch fibre (OPEFB) is a waste from palm oil mill. It is rich in useful compound residues such as cellulose and carboxymethylcellulose. The increasing interest in OPEFB as a source of cellulose is due to its low cost, renewable and abundantly available, particularly in the Southeast Asia region. Cellulose extraction is affected by pre-treatment, especially during the bleaching process. Thus, this study aims to analyse the effect of bleaching period and treatment using NaClO2 on cellulose recovery from OPEFB. Batch process of bleaching was carried out in the ratio of 1:50 of fibres to sodium chlorite (NaClO2) solution of 0.7%. This was followed by analysis of cellulose morphological using FTIR and SEM analysis. The study found that bleaching duration affects cellulose recovery, with the highest yield of 54% found to be at 3 hours of bleaching duration. The bleaching duration was increased up to 6 hours, but found to yield less cellulose, which indicated that certain duration is suitable to provide a condition for higher cellulose yield.

Effect of bleaching treatment on element content of enamel

The aim of study was to evaluate the mineral changes caused by enamel bleaching treatments at different application times by scanning electron microscope- energy dispersive X-Ray (SEM-EDX). In this study, 36 teeth were divided into 3 groups after mineral measurements (Flour, Silicon, Aluminum, Strontium) with SEM-EDX (n ₌ 12). 40% hydrogen peroxide gel was used for bleaching in all groups. Bleaching was performed 20 min for Group 1, 40 min for Group 2, 60 min for Group 3. Mineral measurements were performed with SEM-EDX after treatment. In the intra-group comparison, although there was no significant difference between Flour (F) and Silicon (Si) values (p ˃ 0.05), there was statistically significant difference in Aluminum (Al) and Strontium (Sr) values (p &amp;lt; 0.05). After the bleaching process for different application times, mineral change was observed in time-depending comparison. The best results were obtained for Group 2, appling according to manufacturer's instructions.

Effect of ammonium acryloyldimethyltaurate copolymer on the physical and chemical properties of bleached dental enamel.

To analyze the effect of bioadhesive polymer, Aristoflex® AVC, on enamel physical and chemical properties. Bovine enamel blocks were divided into CP 10% with carbopol-Whiteness Perfect® (WP-FGM), CP 10% with Aristoflex (A + CP 10%), CP 10% with carbopol (C + CP 10%), Aristoflex (A), carbopol (C), carbamide peroxide 10% (CP 10%) and control (no treatment). The treatment was performed for 4h during 14days. The colour (ΔE, ΔL*, Δa* and Δb*), profilometry (Ra) and surface microhardness (KHN) were performed before and after the bleaching treatment. The concentrations of Ca and P were performed on the 1st, 3rd, 7th and 14th days by inductively coupled plasma optical emission spectrometry for the groups WP, A + CP 10%, C + CP 10%, A, C and CP 10% (control without thickener) and the morphology by scanning electron microscopy. All groups with CP 10%, regardless of polymer, differing statistically to ΔE, ΔL*, Δa* and Δb* compared to control group. The group A + CP 10% maintained low values of roughness and microhardness after bleaching. Higher concentration of Ca and P was found in the 1st day of treatment for the WP group compared to the groups A + CP 10% and C + CP 10%. The 10% CP associated with the bioadhesive polymer Aristoflex® AVC was effective on the bleaching treatment without changing the physical properties of the dental enamel. Also, this experimental gel caused less mineral loss than the group CP 10% with carbopol (WP-FGM). Because the change of Carbopol by Aristoflex, a bioadhesive polymer, does not interfere with the effectiveness of bleaching treatment, it is a promising agent associated to carbamide to maintain the physical properties of enamel after bleaching.

Influência da moldeira contendo dentifrício na redução da sensibilidade causada por clareamento dental de consultório

Objetivo: avaliar clinicamente a utilização de dentifrício dessensibilizante, aplicado através de moldeira plástica, na redução da dor e variação de cor causadas pela técnica de clareamento dental de consultório. Material e Métodos: Para o estudo foram selecionados 24 voluntários que foram submetidos ao clareamento dental de consultório em 3 sessões clínicas com intervalo de uma semana, com a utilização de gel clareador (peróxido de hidrogênio - 35%). Na noite referente a cada sessão de clareamento, os voluntários utilizaram uma moldeira plástica por 4 horas contendo um dos dentifrícios relativos aos grupos experimentais: (1) Sucralose (S); (2) Fosfato de sódio (FS) e Silicato de cálcio (SC) (Tecnologia NR-5). A dor foi avaliada antes do uso da moldeira plástica com dentifrício (S1, S3, S5) e após (S2, S4, S6) durante 4 semanas, utilizando a escala numérica analógica com escores de 0 a 10. Para a variação de cor (?E) utilizou-se espectrofotômetro (Easyshade). Resultados: O grupo FS e SC apresentaram redução da dor em relação aos demais grupos (p&amp;lt;0,05). Houve uma redução da dor após o uso da moldeira com dentifrício (S2, S4, S6) por 4h e não houve diferença para ?E entre os grupos experimentais após o tratamento clareador (p=0,91). Conclusão: Conclui-se que a utilização de dentifrício dessensibilizante com FS e SC (Tecnologia NR-5) em moldeira plástica foi eficiente para a redução da dor causada por clareamento dental de consultório e o uso de dentifrício dessensibilizante não influenciou a eficácia do tratamento clareador.

Oil Palm Fiber Vinylester Composite; Effect of Bleaching Treatment

The aim of this paper is to investigate the effect of chemical treatment on the flexural properties of the composite. Oil Palm Empty Fruit Bunch Fibers (OPEFB) reinforced Vinylester composite were prepared in this study. Soxhlet extraction together with sodium hypochlorite bleaching methods was used for chemical treatment. The diameter of fibers was reduced from a range of 250-350 μm to 10-15 μm by treatment. Shape and texture of the fibers transformed from solid brown colored strings into a white gel. Thermogravimetric Analysis (TGA) test was carried to investigate the effect of treatment on the thermal properties of natural fibers. Vinylester composites were fabricated using untreated and bleached OPEFB fibers. The bending test results showed the bleached fibers displayed greater flexural properties compared to untreated fibers, where the time of bleaching was an important factor in the treatment process.

Effect of Bleaching Treatment on Fatigue Resistance and Flexural Strength of Bovine Dentin.

To determine the effects of bleach on dentin fatigue resistance and flexural strength. Eighty bovine dentin specimens (2 × 2 × 17 mm) were treated with: placebo or 10% carbamide peroxide bleach. Treatment was applied for 6 hours/day for 2 or 8 weeks. After treatment, 10 specimens per group were subjected to fatigue testing (10(6) cycles) whereas the other 10 were stored in artificial saliva as fatigue controls. The specimens undergoing fatigue were checked daily for visible signs of fracture and excluded from subsequent flexural strength tests if fractured. Fatigue control and surviving fatigued specimens were subjected to flexural strength testing. Chi-square, Kruskal-Wallis, factorial analysis of variance (p < 0.05) and Mann-Whitney (p < 0.002) tests were performed. There were significant differences in fatigue resistance (p = 0.003) and flexural strength rank scores (p < 0.0001) among the groups. None of the specimens in the "8-week bleach" group survived the fatigue testing. Fatigue (p = 0.005) and interaction of time and treatment (p = 0.039) were significant factors in the flexural strength results. Fatigued specimens had lower flexural strength than nonfatigued and "8-week bleach" had lower flexural strength than placebo and "2-week bleach" groups. Prolonged direct bleaching of bovine dentin reduces its fatigue resistance and flexural strength in vitro. Further research is needed in this area. It remains prudent to advise patients to limit their exposure to tooth bleaching materials by avoiding direct application of bleach to exposed dentin and by minimizing the duration of bleach treatment.

Surface roughness evaluation of in vitro refinished dental ceramics followed by bleaching treatment

Objective: The objective of this study was to evaluate the effect of refinishing process on dental ceramics roughness and the effect of bleaching treatment with 16% carbamide peroxide. Materials and methods: Specimens of 5x3x1mm were produced in two groups (n=14 per group) of dental ceramics following manufacturers' instructions: IPS d.Sign (Ivoclar-Vivadent); and VMK-95 (Vita). A profilometer was used to evaluate the surface roughness (Ra values) of all ceramics acquiring 3 profiles with five 0.25 mm cut-off (?c) at 0.1 mm/s, in four times. The first time was baseline as a negative control, followed by bur roughening (91-126 µm-grit) to simulate an oclusal adjustment in the second time (positive control). After that, the specimens were submitted to refinishing treatments with diamond burs with fine (2135F – 37-44 µm-grit) and extra fine (2135FF – 20-40 µm-grit) diamond burs (third time); and polishing with abrasive cups and paste (fourth time). After refinishing, the two ceramics were divided into a bleached (BL) and non-bleached (NB), with 4 subgroups (n=7 per group). Bleaching was performed daily for 6-hours with 16% carbamide peroxide for 21 days, while NB groups were stored in artificial saliva. The effect of refinishing treatment on ceramics were evaluated by to 2-way ANOVA and Tukey’s test; bleaching effect on refinished ceramics were evaluated by T test. Results: There were no statistical significant differences on surface roughness between ceramics on each refinishing treatments times. The adjustment of dental ceramics with diamond burs drastically increases the surface roughness. The solely treatment with fine and extra fine diamond bur reduced but did not reverse the ceramic surface roughness. The sequential refinishing with abrasive cups and paste reverted the surface roughness to values similar to baseline. Bleaching treatment did not affect the surface roughness of refinished ceramics. Conclusion: Acceptable surface roughness was obtained after refinishing with polishing abrasive cups and paste. The 16% carbamide peroxide treatment was not able to alter the refinished ceramic surface roughness.

Effect of Bleaching Treatment and Reduced Application Time of an Antioxidant on Bond Strength to Bleached Enamel and Subjacent Dentin

To evaluate the influence of bleaching on bond strength to enamel and subjacent dentin, and to determine whether a reduced application time (1 min) of the antioxidizing agent can obviate the compromised bond strength after bleaching. One hundred twelve bovine incisors were obtained, and the enamel and dentin surfaces were standardized to a thickness of 1 mm. The specimens were divided into two control groups (enamel and dentin without treatment) and 12 experimental groups (n = 10), based on the concentration of bleaching agents (carbamide peroxide 16% and hydrogen peroxide 35%), time interval between bleaching and restorative procedures (24 h; 24 h + sodium ascorbate (SA) 10%/1 min; 14 days), and substrate (enamel or dentin). All samples were submitted to the bleaching treatment on enamel. After the stipulated interval, a microshear test was performed. The bleaching treatment compromised the bond strength to the enamel when the restoration was performed 24 h after the end of bleaching. The bond strength to dentin was not affected by bleaching. The SA 10% application for 1 min obviates the detrimental effect of bleaching on bond strength. The bleaching performed on enamel does not affect the bond strength to the subjacent dentin.