Purification of Chitin from Pupal Exuviae of the Black Soldier Fly

Purpose Chitin purification from remains (pupal exuviae after metamorphosis to adult flies) of Hermetia illucens farming was optimized performing demineralization, deproteinization and bleaching under different conditions. The optimal parameters to obtain high-purity chitin were determined. Methods Dried and ground pupal exuviae, whose composition was initially determined, were demineralized using six different acids. Proteins were removed with a NaOH treatment in which temperature, molarity and duration were varied in a randomized experiment. Bleaching was carried out testing ten different chemicals, including NaOCl, H2O2, solvent mixtures and enzymes. The efficiency of each step was determined to assess the optimal conditions for each of them. The resulting chitin was subjected to spectroscopic characterization. Results The highest demineralization efficiency (90%) was achieved using 0.5 M formic acid for 2 h at 40 °C, confirming the validity of organic acids as a more sustainable alternative to inorganic acids. The treatment with 1.25 M NaOH at 90 °C for 4 h showed the highest deproteinization efficiency, removing 96% of the proteins. Temperature and NaOH concentration were the significant parameters for deproteinization efficiency. The most efficient bleaching treatment was with 6% NaOCl at 60 °C for 1 h (67% efficiency). H2O2 could also be a valid alternative to avoid environmental risk related to chlorine-containing compounds. At the end of the purification process 17% of the original biomass was retained with a chitin content of 85%, corresponding to a chitin yield of 14% related to the initial biomass. Solid-state nuclear magnetic resonance showed that the purified chitin had a degree of acetylation of 96% and X-ray powder diffraction gave a crystallinity index of 74%. Conclusion This investigation shows an optimized method for extraction of high-purity chitin from H. illucens pupal exuviae, supporting the validity of insect-farming remains as source of this versatile biopolymer. Graphical Abstract

Colorimetric Comparison of Internal Bleaching with and without Removing Mineral Trioxide Aggregate (MTA) on Induced Coronal Tooth Discoloration by MTA

Objective. This study aimed to colorimetric comparison of internal bleaching with and without removing mineral trioxide aggregate (MTA) on induced coronal tooth discoloration by MTA cement. In this experimental study, twenty human teeth were prepared. An OrthoMTA barrier was placed 1 mm below the CEJ. The teeth were restored with composite resin and were placed in the aging accelerator machine. Then, the specimens were divided into two groups (n = 10); in group A, part of the OrthoMTA was removed and the glass ionomer was placed on the OrthoMTA, and in group B, the OrthoMTA remained intact. Internal bleaching was performed 5 times in 6-day intervals using 37% carbamide peroxide gel. Color determination was performed in 5 stages: baseline, after OrthoMTA discoloration, before OrthoMTA removal, after OrthoMTA removal, and after bleaching treatment sessions. In group A, 8 specimens reached to ∆E < 3.3 after 2 times internal bleaching treatment, and in group B, 5 specimens reached to ∆E < 3.3 with almost 3 bleaching sessions p > 0.05 . Additionally, 5 specimens reached to the initial color (baseline) after bleaching treatment, 4 specimens in group A and 1 specimen in group B. After OrthoMTA removal, 2 specimens in group A reached to ∆E < 3.3. There was no significant difference between groups with or without OrthoMTA removal p = 0.06 . Although, the specimens with OrthoMTA removal required fewer bleaching treatment sessions, and the mean value of ∆E was lower in this group.

Scalable Preparation of Cellulose Nanofibers from Office Waste Paper by an Environment-Friendly Method

Waste paper is often underutilized as a low-value recyclable resource and can be a potential source of cellulose nanofibers (CNFs) due to its rich cellulose content. Three different processes, low acid treatment, alkali treatment and bleaching treatment, were used to pretreat the waste paper in order to investigate the effect of different pretreatments on the prepared CNFs, and CNFs obtained from bleached pulp boards were used as control. All sample fibers were successfully prepared into CNFs by 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) oxidation. It was quite obvious that the bleached CNFs samples showed dense fibrous structures on a scanning electron microscopy (SEM), while needle-like fibers with width less than 20 nm were observed on a transmission electron microscopy (TEM). Meanwhile, the bleaching treatment resulted in a 13.5% increase in crystallinity and a higher TEMPO yield (e.g., BCNF, 60.88%), but a decrease in thermal stability. All pretreated CNFs samples showed narrow particle size distribution, good dispersion stability (zeta potential less than −29.58 mV), good light transmission (higher than 86.5%) and low haze parameters (lower than 3.92%). This provides a good process option and pathway for scalable production of CNFs from waste papers.

Direct Radiotherapy-Induced Effects on Dental Hard Tissue in Combination With Bleaching Procedure

Introduction: The aim of this study was to evaluate the effects of radiation and tooth bleaching on the physical and morphological properties of enamel and dentin on permanent teeth.Materials and Methods: Eighty fresh, non-carious third molars were used in this study. Before cutting the crown in half, the teeth samples were randomly allocated to treatment and control groups by using a lottery method. The first group (n = 20) underwent standard radiation protocol (2 Gy/fraction/day, 5 days/week) with bleaching treatment afterward using 16% carbamide peroxide gel, the second group (n = 20) underwent standard radiation protocol with afterward bleaching treatment using 38% hydrogen peroxide, the third group (n = 20) underwent a short, one strong, experimental dose of 70 Gy with afterward bleaching treatment using 16% carbamide peroxide gel, and the fourth group (n = 20) underwent one strong, experimental dose of 70 Gy with afterward bleaching treatment using 38% hydrogen peroxide gel. Groups 5–8 (n = 20) served as control as they underwent only bleaching treatment. Vickers microhardness and surface roughness were performed before (initial) and after irradiation and before bleaching or after only bleaching. The effects of irradiation and bleaching on microhardness (or roughness) of enamel and dentin were analyzed in the repeated-measures ANOVA model.Results: Enamel microhardness after experimental single 70-Gy irradiation or after standard radiation protocol and bleaching with 16 or 38% gel was not statistically significant from microhardness in the control group (p &gt; 0.05). There was a statistically significantly greater reduction in the average microhardness of enamel and dentin during bleaching with 38% gel compared to 16% for both radiation protocols (p &lt; 0.001). After experimental 70-Gy irradiation and bleaching, a 16% statistically significant increase in surface roughness was found for enamel (p = 0.006) and dentin (p = 0.018), while this was not recorded for 38% gel. There was a statistically significantly greater increase in the average roughness of enamel and dentin during bleaching with 38% gel compared to 16% (p &lt; 0.001) for both radiation protocols.Conclusions: Directly induced radiation leads to potential damage of hard dental tissues, which can be further damaged by additional bleaching. If teeth whitening is necessary after irradiation, it is suggested to use lower concentrations of whitening gels.

Color Stability and Staining Susceptibility of Direct Resin-Based Composites after Light-Activated In-Office Bleaching

This study evaluated color stability and staining susceptibility of five direct resin-based composites (RBCs) subjected to light-activated in-office bleaching with 40% hydrogen peroxide (HP). The test materials included 5 RBCs, which consisted of one nano-filled, one sub-micron, one bulk-filled, and two nano-hybrid RBC types. Ten disc-shaped specimens of each RBC were fabricated and divided into bleaching (BLE) and non-bleaching (CON) groups (n = 5 for each group). Specimens were then immersed in red wine solution over 4 h. A spectrophotometer was used to obtain Commission Internationale de l’Eclairage (CIE) L*a*b* parameters for each of the following periods tested: before bleaching (TBA), after bleaching (TBL), and after staining (TST). Color stability and staining susceptibility were evaluated using two metrics, CIEDE2000 color differences (ΔE00) and whiteness variations using the whiteness index (ΔWID). Data were analyzed using repeated measures two-way analysis of variance (ANOVA) (α = 0.05). Statistically significant and clinically unaccepted ΔE00 and ΔWID were observed for all tested specimens between TBA and TBL. The nano-hybrid type RBCs showed the highest discoloration among materials after bleaching treatment. The BLE group exhibited significantly higher ΔE00 and ΔWID than the CON group for all the tested RBCs between TBA and TST. The sub-micron type RBC showed the highest discoloration among materials after immersion in the red wine. Conclusion. The light-activated in-office bleaching with 40% HP’s influences on color and whiteness index were material-dependent. The use of bleaching treatment also increased the susceptibility to red wine for all RBCs.

Application of Fiber Made from Bark of Salak (Salacca Zalacca) Tree as Reinforcement in Polymer Matrix Composites

<p class="02abstracttext">Although Indonesia is abundant supply of salak (Salacca zalacca) fruit, bark of salak is not yet advanced utilized. This work therefore chracterized its fiber and process it into polymer matrix composites. The study was conducted using varied chemical treatments. Delignification using NaOH solution with concentration of 1%, 5%, 10% with 3 hours immersion time. Bleaching treatment was using H₂O₂ media with varied immersion time at 30, 60 and 90 minutes. Tensile tests, impact tests, microscopic image test using scanning electron microscopy (SEM) and chemical composition test using fourier-transform infra-red (FTIR) spectroscopy were carried out in this work. This work showed that optimal delignification treatment can be found when 5% NaOH concentration was used. The corresponding ultimate tensile strength and impact strength were 25.47 MPa and 11.95 kJ/m², respectively. The optimal bleaching treatment was 90 minutes immersion. The results of SEM image analysis showed that the salak midrib fiber composite without treatment has a lousy interface. Meanwhile, fiber with delignification treatment only has reasonable good interface and fiber with delignation treatment followed by bleaching treatment has excellent interface. FTIR test results showed that the salak midrib fiber composite without treatment had a cellulose component although hemicellulose and lignin levels still dominated. The delignification treatment had succesfully broken the lignin-specific C = O bond but still could not eliminated hemicellulose and lignin bond. In comparison, bleaching treatment reduced intensity of OH intensity, CH and CO which are typical hemicellulose and lignin functional groups. Based on the results of the study, salak midrib fiber with delignification chemical treatment using 5% NaOH for 3 hours followed by bleaching treatment using 2% H₂O₂ for 90 minutes was the best treatment.</p>

Effect of sodium hypochlorite concentration during pre-treatment on isolation of nanocrystalline cellulose from Leucaena leucocephala (Lam.) mature pods

Mature pods of Leucaena leucocephala (Lam.) de Wit were utilized as raw material for nanocrystalline cellulose (NCC) production. NCC’s isolation begins with L. leucocephala fiber’s alkaline treatment with sodium hydroxide, followed by bleaching treatment at three different percentages (3%, 5%, and 7%) of sodium hypochlorite. Acid hydrolysis was then conducted to obtain NCC, which was comprehensively characterized in terms of morphology, chemical functional groups, whiteness index, and crystallinity. Fourier-transform infrared spectroscopy (FTIR) and chemical composition results showed that alkali treatment (NaOH) and bleaching (3%, 5%, and 7% of sodium hypochlorite, NaClO) were effective in the removal of lignin and hemicellulose. The variation of sodium hypochlorite concentration affected physical and structural characteristics of the NCC produced, which exhibited a rod-shaped structure with diameters ranging from 17 to 49 nm. These observations provide insight into the potential utilization of L. leucocephala as raw material for preparing nanocellulose, which may address problems of the underutilized mature pods.