Peroxide Bleaching Research Articles

Bleaching efficacy, decomposition rate and pH of experimental bleaching gels incorporating bioactive materials

Aim: To evaluate the bleaching efficacy, decomposition rate, and pH of experimental gels containing 35% hydrogen peroxide (HP) and different concentrations of 45S5-bioglass (BG) or Biosilicate® (BS). Methods: Bovine enamel/dentin blocks (n=10) were allocated into the groups HP_BG or HP_BS (2.5, 5, 7.5 and 10 wt%) and HP (35% HP – positive control). The blocks were submitted to three sessions of 40 min and 7-day intervals. During the interval, the blocks were kept in artificial saliva at 37ºC. Color change (ΔE00) and whiteness index change (ΔWID) were determined after staining with black tea (T1) and 24 h after the 3rd bleaching session (T2). HP decomposition rate (%) and pH were evaluated for 40 min. Two-way ANOVA and Tukey analyzed ΔE00 and ΔWID data, while the Kruskal-Wallis test determined the decomposition rate and pH of the gels. Results: There were no differences in ΔE00 and ΔWID among the experimental bleaching gels containing BG or BS and 35% HP (p > 0.05), but BG and BS gels displayed lower HP concentration than 35% HP, regardless of the bioactive material concentration (p < 0.05). The experimental BG and BS gels exhibited alkaline pH (ranging from 9.28 to 9.82), which was higher than that of 35% HP (p < 0.05). But regardless of the gel, all kept the pH values stable for 40 min. Conclusion: The experimental gels containing BG and BS did not hamper the 35% HP bleaching efficacy. Moreover, BG or BS gels decreased the hydrogen peroxide concentration and exhibited alkaline pH values.

Photocatalytic Bleaching Process of Cotton Fabric with H2O2 and H2O2 /n-TiO2

This study delves into the exploration of an alternative bleaching method as a substitute for hydrogen peroxide, addressing concerns related to its excessive chemical usage, high waste load, and elevated energy and water consumption. Photocatalytic bleaching was implemented on 100% cotton fabrics. Initially, hydrogen peroxide served as a catalyst, and the photocatalytic effect was meticulously examined. Subsequently, nano-sized TiO2 was introduced into the photocatalytic recipe, and operational conditions were fine-tuned to determine the optimal bleaching process for cotton fabrics. All photocatalytic experiments were systematically compared with conventional hydrojen peroxide bleaching method. A comprehensive analysis, encompassing color spectrum values, SEM, SEM-EDX, XRD, and FTIR-ATR tests, was conducted. The results revealed a notable 13.36% enhancement in whiteness performance during bleaching when subjected to photocatalytic treatment with nano TiO2 and H2O2 in tandem. This study posits itself as an environmentally conscious alternative to the long-standing conventional bleaching processes prevalent in the textile industry.

Ecofriendly bleaching method for cotton fabric: Development of titanium dioxide doped single wall carbon nanocomposites by photocatalytic treatment for sustainable textile pre-finishing applications

This study aimed to find an eco-friendly substitute method and chemical for conventional hydrogen peroxide (H2O2) bleaching of cotton fabric. We developed diverse functional groups containing titanium dioxide-doped single-wall carbon nanotubes (TiO2-SWCNTs) particles, designed a photocatalytic system, and examined the effects of working conditions and functional group variations on the degree of fabric whitening. Throughout the many phases of the chemical development process, X-ray diffraction (XRD), Fourier transform infrared spectroscopy −Attenuated total reflectance (FTIR-ATR) and the scanning electron microscopy (SEM) tests were conducted. In addition, the color spectrum values, the whiteness indexes, the results of the tearing test, SEM and FTIR-ATR findings of 100% cotton textiles were presented that were treated with TiO2-SWCNTs particles using the photocatalytic technique. The test results demonstrated the successful synthesis of various types of TiO2-SWCNTs, leading to a significant enhancement in the whiteness of the cotton fabrics. This increase reached 21.79% using a small amount of nano-chemicals, surpassing the whiteness index value created by the conventional H2O2 bleaching process. Optimal results were achieved by using minimum quantities of substance and working at moderate temperatures. According to this information, it can be concluded that this approach may serve as a substitute for the conventional H2O2 whitening procedure in terms of both the substance utilized and the application method, specifically for treating cotton fabric. Moreover, the statistical analysis revealed that the fabric’s self-cleaning capacity is significantly influenced by the square of temperature and pH.

Effect of a novel low-concentration hydrogen peroxide bleaching gel containing nano-sized sodium trimetaphosphate and fluoride

ObjectivesTo evaluate in vitro the effects of nano-sized sodium trimetaphosphate (TMPnano) and sodium fluoride (F) added to a 17.5 % hydrogen peroxide (H2O2) bleaching gel on the color change, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and MethodsBovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 17.5 % H2O2 (17.5 % HP); 17.5 % H2O2 + 0.1 % F (HP/F); 17.5 % H2O2 + 1 % TMPnano (HP/TMPnano); 17.5 % H2O2 + 0.1 % F + 1 % TMPnano (HP/F/TMPnano) and 35 % H2O2 (35 % HP). The gels were applied for 40 min on three sessions, each session spaced 7 days apart. The total color change (ΔE*ab) according to the Commission Internationale de l'Eclairage (CIE) L*a*b* color change measured by CIEDE2000 (ΔE00), whitening index (ΔWID), surface hardness (SH), surface roughness (Ra), cross-sectional hardness (ΔKHN), and transamelodentinal diffusion were assessed. Enamel surfaces were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDS) analysis. The data were analyzed using ANOVA, followed by the Student-Newman-Keuls test (p < 0.05). ResultsΔE*ab, ΔE00, and ΔWID values were comparable among the gels that produced a bleaching effect post-treatment (p < 0.001). The HP/F/TMPnano group exhibited lower mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion compared to the 17.5 % HP and 35 % HP groups, which had the highest values (p < 0.001). SEM/EDS analysis revealed surface changes in all bleached groups, though these changes were less pronounced with F/TMPnano. ConclusionsThe 17.5 % HP gel containing F/TMPnano maintains the bleaching effect while reducing enamel demineralization, roughness, H2O2 diffusion, and enamel morphological changes. Clinical RelevanceLow-Concentration H2O2 bleaching gel containing F/TMPnano can be used as a novel approach to enhance safety and maintain the performance of aesthetic effects.

Photocatalytic Activity of Zinc Oxide Nano Particules and Boric Acid for Bleaching Process on Cotton Fabric

In this study, a photocatalytic process was applied as an alternative to conventional hydrogen peroxide bleaching on 100% cotton fabric. The effects of ZnO nanoparticles and boric acid as catalysts were investigated. Additionally, the synergistic impact of boric acid on the well-known bleaching effect of titanium dioxide nanoparticles was explored. Unlike existing literature, the study uniquely addressed whether the photocatalytic process, without the use of any catalyst, has a specific effect, particularly in whitening, on the color spectrum. All conducted photocatalytic processes on cotton fabrics were compared with conventional hydrogen peroxide bleaching in terms of color spectra (CIE L*, a*, b*, whiteness indexes) besides the SEM, SEM-EDX, and FTIR-ATR characterization tests. Moreover, XRD, SEM, and FTIR-ATR analysis results of ZnO nanoparticles were also shared in this study. This research is believed to shed light on future studies by evaluating more environmentally friendly pre-treatment processes in textile industry.

Effectiveness of desensitizing toothpastes in reducing tooth sensitivity after tooth bleaching: a systematic review.

To evaluate the effectiveness of desensitizing toothpastes in reducing post-bleaching tooth sensitivity. A systematic review of randomized clinical trials was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. Electronic searches were conducted in the PubMed/MEDLINE, Scopus, Web of Science, The Cochrane Library and Embase databases, using the following terms: (dentifrices OR toothpaste) AND (sensitive OR sensitivity OR dental sensitivity) AND (dental bleaching OR tooth bleaching OR dental whitening OR tooth whitening). Five studies involving 387 individuals undergoing in-office or at-home teeth bleaching were reviewed. Desensitizing toothpastes reduced sensitivity effectively after home bleaching with 22% carbamide peroxide and single-session in-office bleaching with 35% hydrogen peroxide. However, they were ineffective for home bleaching with 16% carbamide peroxide and in-office bleaching across two sessions with 35% or 38% hydrogen peroxide. Desensitizing toothpastes are effective for home bleaching with high concentration carbamide peroxide and single-session in-office bleaching with highly concentrated hydrogen peroxide, but ineffective for home bleaching with low concentration carbamide peroxide and two-session in-office bleaching with concentrated hydrogen peroxide.

Assessment of the effect of experimental gel of pregabalin associated with 35% hydrogen peroxide bleaching on bovine dental enamel: an in vitro study.

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.

Extraction of micro fibrous cellulose from coconut husk by using chlorine free process: Potential utilization application as a filter aid

Cellulose is one of the most important linear, hydrophobic biopolymers built-up of several units of d-glucopyranose unite through beta-1,4-Glycosidic linkage. Due to these structural features, porous nature, swelling property and strength, cellulose has many industrial and biomedical applications. In this work, we have effectively isolated micro fibrous cellulose from waste coconut husk after removing lignin, hemicellulose, and other impurities by repeated water washings, mechanical, alkali (NaOH) and chlorine free green hydrogen peroxide bleaching. This process provides about 42% w/w white to off white soft micro fibrous long and individual cylindrical rod-like microfibril having fiber size of ∼ 14 µm. The extracted micro fibrous cellulose was evaluated for structural, morphological, crystalline, and thermal properties by using FTIR, SEM, HR-TEM, XRD, and DSC. The swelling capacity of extracted micro fibrous cellulose was investigated at different pH for different contact hours. The maximum percentage swelling capacity (PSC) (991.7%) was observed in 6 h at pH 9.4 which is comparable to PSC obtained (975%) at pH 7.4 in 24 h. The property of porous nature, and high surface area, enable it to use as an eco-friendly filter aid for effective removal of colored impurities from different chemicals and pharmaceutical substances, ensuring high quality purified material.

Nano Photo Bleaching Method of Cotton Fabrics for a Sustainable Finishing

In modern textile-bleaching methods, H2O2 is commonly preferred due to its less harmful effects on the environment. The use of hydrogen peroxide in bleaching processes, although biodegradable on its own, increases the waste load due to the high amount of auxiliary chemicals used. The long processing times and high-temperature requirements of hydrogen peroxide bleaching led to increased energy consumption. Moreover, the high-water consumption required for post-treatment is also a disadvantageous factor. In other words, while the use of a high amount of auxiliary chemicals in hydrogen peroxide bleaching increases the waste load, long time and high-temperature requirements also increase energy consumption, and the high-water consumption required for post-treatment has a disadvantageous effect. In this study, raw cotton fabric is subjected to chemical finishing treatments that either oxidize or reduce it as part of the bleaching process. The results of photo bleaching were compared with conventional hydrogen peroxide finishing applications. Our findings showed that nano-TiO2-treated cotton had a better whiteness value than treated with H2O2 cotton according to the color spectrum whiteness indexes. It is strongly considered that this method could be a new alternative way for bleaching textile materials in the finishing departments.

Effect of Various Vital Bleaching Systems on Clinical Outcomes and Patient Satisfaction.

Objective To evaluate the clinical behavior of different bleaching products - the hydrogen peroxide (H2O2), carbamide peroxide (CP), and titanium dioxide bleaching systems. Methods Three bleaching systems with different concentrations (H2O2 15%, 38%, CP 15%, 35%, and titanium dioxide 20% H2O2) were used. Sixty participants with discolored teeth were enrolled and equally divided into six groups. Each group was rendered the assigned bleaching protocol against the control group, which received plain dentifrice polishing.Each case was evaluated immediately, two weeks, three months, six months, and one year after the bleaching treatment. The clinical evaluation was made for color change by (shade guide and digital images with L*a*b* parameters), tooth sensitivity, gingival irritation, and participants' satisfaction. Results All bleaching systems showed color improvement after bleaching regimens with significant effect showed by in-office titanium dioxide 20% H2O2 followed by 38% H2O2 with Δ=10.26 and Δ=6.52, respectively, when compared to other bleaching techniques. Higher sensitivity was recorded in group III with 50% of the participants reporting postoperative sensitivity. Higher gingival irritation was recorded in group IV (15% CP) where 60% of the patients reported gingival irritation. Thirty-five of the 60 participants (58.5%) recorded that the treatment whitened their teeth "moderately" and "a lot" while seven participants recorded "a slight" difference. There was a highly significant difference in participants' satisfaction between all bleaching groups (p < 0.05). Conclusion It is evident that there is a development of dental sensitivity and gingival irritation irrespective of the bleaching system used. The color assessment showed that the desired result can be achieved with variable levels of patientsatisfaction with excellent overall results with the titanium dioxide system.

The Effect of Carbamide Peroxide Bleaching Gel with and without Remineralizing Agents on Microtensile Bond Strength of Resin Composites to Enamel

Introduction: Carbamide peroxide bleaching gel, along with remineralizing agents, can induce changes in the structure and mineral content of enamel, potentially leading to a decrease in the bond strength of resin composite to the enamel. Therefore, this laboratory study aimed to determine the effect of carbamide peroxide bleaching gel with and without remineralizing agents on the microtensile bond strength (µTBS) of resin composites with microhybrid and nanofill structures to enamel. Materials and Methods: Thirty extracted third molar teeth were randomly divided into five groups, each group subdivided into two equal subgroups: Group 1: Control group, Group 2: Bleaching gel without fluoride, Group 3: Bleaching gel containing fluoride, Group 4: Bleaching gel containing CPP-ACP, and Group 5: Bleaching gel containing fluoride and CPP-ACP. In the first subgroups, nanofilled resin composite Filtek Z350, while in the second subgroups, microhybrid resin composite Filtek Z250 were bonded to enamel surface. After specimen preparation, µTBS was measured using a universal testing machine. Data were analyzed using parametric tests (P value&lt;0.05). Results: The highest µTBS of resin composite to enamel was observed in the control group, while the lowest bond strength was seen in the fluoride-containing bleaching group. Comparisons of µTBS between the study groups pairwise, except for the comparison between the control group and the bleaching group, the bleaching group with (CPP-ACP+Fluoride), and the (CPP-ACP) group with the fluoride group, showed significant differences in bond strength. Although, the mean µTBS of the Filtek Z250 composite was higher than the Filtek Z350 composite in all groups, but this difference was not statistically significant. Conclusion: The use of carbamide peroxide bleaching gel with remineralizing agents leads to a decrease in µTBS of the resin composite to the enamel.

Comparative Evaluation of the Effect of Different Types of Bleaching Dentifrices on Shear Bond Strength of Orthodontic Metal Brackets Bonded by Conventional Composite to Human Teeth: An In Vitro Study.

This study aims to evaluate and compare the effect of different types of bleaching dentifrices on the shear bond strength of orthodontic metal brackets bonded by light-cured composite adhesive to human teeth. Forty-five human premolar teeth were randomly divided into three groups, receiving the following treatments: Group 1 (control group; teeth in this group were not bleached), Group 2 (teeth in this group were treated with active oxygen bleaching dentifrice), and Group 3 (teeth in this group were treated with peroxide bleaching dentifrice). Orthodontic brackets were bonded using a light-cured composite adhesive. A universal measuring device was used to assess the shear bond strength with a crosshead speed of 0.5 mm/min. One-way ANOVA, post hoc Tukey tests, and an independent t-test were used to analyse the data. There was a highly significant difference (p≤0.001) in the mean shear bond strength of orthodontic brackets bonded to untreated teeth as compared to teeth treated with bleaching dentifrice. There was no significant difference in the mean shear bond strength of orthodontic brackets bonded to teeth treated with peroxide bleaching dentifrice or active oxygen bleaching dentifrice. There was a significant reduction in the mean shear bond strength of orthodontic metal brackets when bonded to human teeth treated with bleaching dentifrices.

Reduction of surface treatment time by combination of citric acid and ascorbic acid while restoring shear bond strength of metal brackets bonded to bleached enamel: a pilot study

BackgroundTo investigate the effect of a 50% ascorbic acid with 50% citric acid solution on the immediate shear bond strength (SBS) of metallic brackets after tooth bleaching. The enamel etching pattern and the required quantity of these combined acids as antioxidants following 35% hydrogen peroxide (HP) bleaching were also determined.MethodsThe stability of the solution at room temperature was assessed at various time intervals. Fifty teeth were randomly divided into five groups: non-bleached (G1), bleached then acid etched (G2), bleached followed by a 10-minute treatment with 10% sodium ascorbate and acid etched (G3), 5-minute treatment with 50% ascorbic acid (G4), and 5-minute treatment with a combination of 50% ascorbic acid and 50% citric acid (G5). Groups G2, G3, G4 and G5 were bleached by 35% HP gel for a total of 32 min. Acid etching in groups G1, G2, and G3 was performed using 37% phosphoric acid (Ormco®, Orange, CA, USA) for 15 s. In all groups, metal brackets were immediately bonded using Transbond™ XT primer and Transbond™ PLUS adhesive, with light curing for 40 s. The SBS was tested with a universal testing machine, and statistical analysis was conducted using one-way ANOVA followed by Tukey’s HSD test. The level of significance was set at p < 0.05 for all statistical tests.ResultsStability tests demonstrated that the combined acids remained effective for up to 21 days. Group G5 significantly increased the SBS of bleached teeth to the level of G1 (p < 0.05), while G3 did not achieve the same increase in SBS (p > 0.05). SEM analysis revealed enamel etching patterns similar to those of both control groups (G1 and G2). Kinetic studies at 6 min indicated that the antioxidation in G5 reacted 0.2 mmole lower than in G3 and G4.Conclusion5-minute application of the combined acids enhanced the SBS of bleached teeth comparable to unbleached teeth. The combined acids remain stable over two weeks, presenting a time-efficient, single-step solution for antioxidant application and enamel etching in orthodontic bracket bonding.

Response of partial substitution of MgO for NaOH as the alkali source in hydrogen peroxide bleaching to properties of triploid poplar chemi-thermomechanical pulp

Given the current scarcity of wood fiber resources, it is imperative to investigate the potential of employing weak alkaline hydrogen peroxide for bleaching high-yield pulp (HYP) to meet the increasing demands for paper and paperboard. This work presents an investigation into the characteristics of triploid poplar chemi-thermomechanical pulp (CTMP) hydrogen peroxide bleaching, including the brightness, bleaching yield, bulk, physical strength, and contents of carbohydrates and lignin. The findings show that partial substitution of MgO for NaOH as an alkali source could improve the yield and bulk of the bleached CTMP. When the substitution ratio of MgO for NaOH reached 75 %, the brightness of 74.62 % ISO for the bleached pulp dropped by only 0.47 percent points but the bulk of 2.21 cm3/g increased by 5.74 % compared to those of the control, respectively. Meanwhile, the yield of the bleached CTMP could reach 93.45 %, 5.07 percent points higher than that of the control. The results would be of benefit to the HYP enterprises concerned.

Effect of Bleaching Agents on Healthy Enamel, White Spots, and Carious Lesions: A Systematic Review and Meta-Analysis.

This systematic review examines studies focusing on tooth bleaching and its effects on healthy enamel or incipient caries and bacterial adhesion. The aim is to explore the impact of different bleaching agents on incipient caries lesions and healthy enamel. Clinical studies, in vitro studies, and observational studies that compared at least two groups were included. A search strategy was used to select studies from the MEDLINE via Pubmed and Scopus databases. Two evaluators performed data extraction, screening, and quality assessment independently. Only studies written in English were included. From 968 initial records, 28 studies were selected for a full-text evaluation. Of these, 7 studies were classified as cluster 1 (bacterial adherence on teeth), 12 studies as cluster 2 (no bacteria involved), 4 studies as cluster 3 (no teeth deployment), and 5 clinical studies were cluster 4. Of the selected studies, 6 (21.4%) supported increased bacterial attachment capacity and cariogenic dynamics, 4 (14.3%) decreased adhesion and cariogenic activity, 7 (25%) showed no difference, and 11 (39.3%) followed a different methodological approach and could not be categorized. The risk of bias appeared to be high, mainly because of the different methodologies in the studies, so we cannot reach a confident conclusion. Nevertheless, as far as carbamide peroxide bleaching is concerned, there does not seem to be a clinically significant alteration, neither in microorganism counts nor in enamel microstructure.

Insight into Low-Temperature One-Step Biopreparation and Natural Dyeing of Cotton as an Environmentally Benign Route

The goal of this study is to present an environmentally benign route for cotton fabric and investigate the effect of different pretreatments in natural dyeing. In this context, conventional alkaline scouring, conventional hydrogen peroxide bleaching, low-temperature one-step biopreparation processes, namely enzymatic scouring (alkaline pectinase and alkaline pectinase-neutral cellulase combination) at 55 °C and enzyme-bleaching agent (hydrogen peroxide/sodium percarbonate/sodium perborate)-activator agent (TAED) combinations at 65 °C were applied to 100% cotton knitted fabric. The use of agricultural waste and eco-friendly mordants was preferred in natural dyeing. For this purpose, pretreated fabrics were dyed with the outer green shell of almond fruit extracts and a low amount of 0.4 g/L metal mordants (alum and iron(II) sulfate) in accordance with the simultaneous mordanting method. The dyeing properties of bio- and conventionally prepared cotton fabrics were examined in terms of colorimetric data (K/S, CIELa*b*C*h°) and wash fastness compared with water absorbency, whiteness, weight loss, pectin removal, and type of mordant. Excellent wash fastness values were achieved regardless of the type of pretreatment. Low-temperature one-step biopreparation can be a good substitute for conventional scouring and bleaching processes. Since different results can be achieved, it is essential to determine and evaluate all bioprocess conditions depending on the end-use characteristics of the textile (e.g. whether it will be white or dyed/printed, its color and lightness/darkness) at the laboratory and industrial scale applications.

The Effect of Home Bleaching on Color Match with Anterior Single Shade Composite Restoration

Background: Aim of this study is to assess the color matching in class III restorations made with single-shade resin composite after bleaching with different carbamide peroxide concentrations. Methods: In this study, 20 human incisors that were free of caries or enamel abnormalities and freshly extracted for periodontal or orthodontic reasons were cleaned of blood, debris, and calculus. Mesial and distal surfaces were restored with single-shade composite (Omnichroma, Tokuyama, Japan). All samples were randomly divided into two groups, all of the mesial surfaces were isolated, and distal surfaces were coated with %10 and %15 carbamide peroxide (Opalescence PF; Ultradent Products, Inc, USA). Polishing discs (Zenit Flex, President Dental, Germany) were used the composite restoration. Color matching was evaluated on photographs with a digital colorimeter. SPSS software program was used to perform statistical analysis (IBM Corp., Armonk, NY, USA). Results: Statistically significant difference was found between the color matching of the restorations after the 5th treatment with 15% carbamide peroxide (p = 0.004), and at the end of 10th treatment with 10% carbamide peroxide (p = 0.028). Depending on the carbamide peroxide concentration, after the 5th treatment a statistically significant difference was found between 15% and 10% carbamide peroxide (p = 0.000), but no statistically significant difference after the 10th treatment (p &amp;gt; 0.05). Conclusions: After carbamide peroxide bleaching, hard tissue color became lighter. Since there is no color pigment in single-shade composites, color might be lighter after bleaching. Therefore, these composites may be considered safer in bleaching. Keywords: Bleaching, Color Match, Composite

Chemical Hydrolysis-Gamma Irradiation Processes for Cellulose Nanofibers Isolation from Rice Straw

Utilization of agriculture biomass waste into high value product is still potential to develop. In this study, cellulose nanofibers (CNF) as valuable materials were isolated from rice straw. Sodium hydroxide pulping and hydrogen peroxide bleaching were conducted as cellulose pretreatment. The CNF was prepared using 1 M hydrochloric acid hydrolysis followed gamma irradiation with various radiation doses, i.e. 40, 60, 80, 100 and 120 kGy. Compositions of α–cellulose and water retention of each stage processes increased inversely with hemicellulose, lignin and degrees of polymerization which had been strengthened by Fourier transform infrared spectroscopy (FTIR) spectra. X-ray Diffraction (XRD) analysis revealed that crystallinity index was more intense than rice straw, i.e. 80.85 %. Particle Size Analyzer (PSA) studies described the isolation process of CNF succeed with the smallest size 77.8 nm. The CNF functional groups of hydrophilic both hydroxyl and carboxylate slightly diminished with increasing of radiation doses followed water retention reducing, however the crystallinity had not changed significantly. Increasing radiation doses also could improve the thermal stability with the highest Tg 153.1 0C therefore the obtained CNF could be used as suitable nanocomposite.

Microleakage effect of in-office bleaching on two types of nanohybrid composites with or without surface sealer.

Bleaching is a highly common method used nowadays to treat tooth discolouration because it is a significant cosmetic issue, particularly with anterior teeth, however bleaching itself results in microleakage. This study aims to evaluate the impact of in-office bleaching on class V restoration microleakage with type 1 and type 2 composite restorations. Three hundred and twenty healthy, caries-free removed human anterior teeth were used in this in-vitro study. All extracted teeth had their buccal and lingual surfaces uniformly prepped for class V cavities. The 120 removed teeth were divided into two groups, with Group 1 receiving Tetric N-Ceram nanohybrid composite restorations and Group 2 receiving 3 M Filtek Z350 XT nanohybrid composite restorations. Groups 1 and 2 were further broken into four more subgroups of four each. The restorations were sealed with a G-Coat Plus resin. The p-value was kept at 0.005 for the data analysis using the Chi-square and Fisher exact tests. Allocating microleakage among 320 study models revealed that 141 (44.1%) study samples had no microleakage, whereas 20 (6.3%), 54 (16.9%), and 105 (32.8%) study samples had microleakage up to, between, and greater than two-thirds of cavity depth. With a statistically significant p-value of 0.001, no microleakage was discovered in 85 (53.1%) lingual surfaces with Tetric N-Ceram nanohybrid composite restoration and 56 (35%) buccal surfaces with 3M Filtek Z350 XT nanohybrid composite restoration. 19.1% of samples of N-Ceram that were sealed and not bleached had no microleakage, according to analysis of microleakage across several groups. With a p-value of 0.001, the distribution of microleakage among various clusters was statistically notable. According to the findings of the study, hydrogen peroxide bleaching has an enhanced impact on micro escape during dye dispersion. Both with and without bleaching, resin coating can be utilised to minimise marginal microleakage.

Extraction and characterization of cellulose microfibers from cornhusk for application as reinforcing agent in biocomposite

This study aims to extract and characterize cellulose microfibers from cornhusk, an agricultural by-product. The extracted fibers will then be used as a reinforcing agent in a biocomposite made of thermoplastic corn starch. The process of extracting cellulose microfibers involved two treatments: sequential alkali treatment (using sodium hydroxide at 120 °C for 120 min) and peroxide bleach treatment (using hydrogen peroxide at 90 °C for 60 min). Various techniques such as Fourier transform infrared (FTIR), X-Ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the extracted fibers. The properties of the composite were examined through tensile strength tests, contact angle measurements, and UV–Vis spectrophotometry. The study found that cellulose microfibers were successfully extracted from cornhusks, with a diameter of 7 to 30 μm and a crystallinity of 65 %. The treated fibers showed gradual degradation between 150 °C and 350 °C, indicating a lower amount of non-cellulosic substances compared to untreated cornhusks. Adding 10 % of the microfibers to the thermoplastic starch composite increased the tensile stress at breaking and the Young's modulus, but decreased the contact angle of water droplets and the film's transparency.