Bleaching Treatment Research Articles

Bleaching Gels and Light-Emitting Diodes: Comparison of Tooth Color Change.

To measure difference in tooth shade and color achieved via two different over-the-counter bleaching agents with and without their associated light-emitting diodes (LEDs). A total of 84 extracted human anterior teeth were randomly divided into seven groups. Gypsum models were made with 6 extracted teeth in an arch form (n = 12; 2 arches/group). Samples were kept hydrated throughout treatment (25°C). Bleaching treatment followed manufacturers' instructions with at least 1-h of rehydration between treatments. Control tooth arches were left untreated. L*a*b* values were measured with a Vita Easyshade (VITA North America, Yorba Linda, CA) three times per tooth using white and black backgrounds. ∆E (CIE 2000) was compared between and within treatment groups over time with ANOVA and post hoc Tukey (a = 0.05). Subgroup testing confirmed the data were normally distributed. Two-way ANOVA showed significant interaction between product (Control, Crest, Snow) and treatment (light only, product only, light and product) on ∆E values for black (p-value < 0.001, F = 15.28) and white (p-value < 0.001, F = 13.62) backgrounds. Post hoc pairwise Tukey tests showed a significant effect of light-and-product treatments in contrast to light- or product-only treatments. Repeated measures ANOVA of between-treatment change (∆E) by product showed significant interaction between time and treatment for Snow products (p < 0.001, F = 10.9) and independent effects of time and treatment for Crest products (Time: p-value < 0.001, Treatment: p-value < 0.01, F = 7.21) on a black background. On white backgrounds, only a significant effect of treatment was reported for both Snow (p-value < 0.01, F = 5.427) and Crest (p-value < 0.001, F = 5.61). Overall, a combination of light and gel produces significantly higher tooth color and shade change over time, with the highest change seen for Snow products. Many patients use over-the-counter tooth bleaching products because they are more cost effective and easier to access than in-office bleaching. However, these products may have adverse effects, such as increased sensitivity with repeated use, in addition to increased consumption of time and money. This project measured tooth shade between treatments which can help determine which product is most effective for at home use.

Maintenance of dental bleaching: A systematic review

After bleaching procedure, color pigments can adhere to the rough dental surface and can trigger more discoloration. In this sense, no standard post-bleaching maintenance technique exists. The purpose of this study was to evaluate the maintenance of enamel color after bleaching procedure through a systematic review. The research question was defined as follows: Is the tooth whitening maintenance necessary after a bleaching treatment? Two reviewers conducted the literature search in PubMed (MEDLINE), Web of Science, Scopus, EMBASE, and SciELO. Both in vitro and clinical trials reporting the color change of bleached enamel after the use of a tooth whitening agent were included in the review. The risk of bias in the included manuscripts was evaluated using the RoBDEMAT tool. A total of 11 articles were included in the qualitative analysis. Due to the lack of groups for comparison, a meta-analysis could not be conducted. The whitening maintenance procedures identified were remineralizing agents, antioxidants, over-the-counter agents, toothpaste containing Blue Covarine, casein phosphopeptide-amorphous calcium phosphate fluoride paste, 0.05% sodium fluoride mouthwash, arginine, nano-hydroxyapatite, nano-carbonate apatite, and CO2 laser. In conclusion, tooth whitening maintenance could be achieved by using some agents. The association of these agents might be beneficial for maintaining the color of the enamel throughout 12 months following bleaching procedure.

The regularities of spent bleached earth treatment with the ester-aldehyde fraction

The regularities of extraction of adsorbate from spent bleaching earth (SBE) of sunflower oil by the esteraldehyde fraction (EAF) have been established. The content of the substances adsorbed by SBE was 34.1%, including 19.2% free fatty acids (FFA) and 11.1% moisture. The influence of temperature (50 and 700C), extraction duration (60 and 120 min), and the mass ratio of EAF to SBE ((2–4):1) on the extraction parameters has been determined. It was found that increasing these process parameters enhances the extraction degree of the adsorbate and FFA from the bleaching earth, reaching 41.9% and 34.4%, respectively, at a temperature of 700C, extraction duration of 120 min, and a mass excess of EAF to SBC at a ratio of 4:1. Optimal conditions for the removal of FFA from SBE were identified. It was established that strong acidic sites are present on the surface of the bleaching earth, with the acidity of fresh, spent, and EAF-treated bleaching earth being 0.79, 0.77, and 0.74 mmol H+ per gram, respectively. The basicity of fresh bleaching earth was 0.073 mmol OH– per gram, indicating the ability of bleaching earth to catalyze the esterification of FFA with ethanol. The suitability of the obtained extract for the production of FFA ethyl esters was demonstrated.

Isolation and extraction of microcellulose from Alpine galanga fiber

Bleaching and alkalization techniques enhance cellulose isolation and extraction, leading to higher yields and improved quality, but may cause inconsistencies in production and quality.This study investigates the extraction, characterization, and thermal properties of Alpine galanga fiber (AGF), a byproduct of traditional Indonesian herbal medicine. Utilizing hydrothermal bleaching and alkali treatments, the cellulose content in AGF was significantly enhanced, achieving a purity of up to 73%. These treatments effectively removed contaminants, improved fiber crystallinity as shown by X-ray diffraction (XRD) analysis, and enhanced surface features observed through scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) identified several stages of thermal decomposition, with treated fibers exhibiting increased thermal resistance. The findings indicate that bleaching and alkalization techniques enhance the yield, quality, and chemical properties of AGF, highlighting its potential for industrial applications. Further optimization and focused investigations are recommended to fully exploit AGF in the development of biocomposites and environmentally friendly materials.

Metal-Based Oxygen Reduction Electrocatalysts for Efficient Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) is a high-value chemical widely used in electronics, textiles, paper bleaching, medical disinfection, and wastewater treatment. Traditional production methods, such as the anthraquinone oxidation process and direct synthesis, require high energy consumption, and involve risks from toxic substances and explosions. Researchers are now exploring photochemical, electrochemical, and photoelectrochemical synthesis methods to reduce energy use and pollution. This review focuses on the 2-electron oxygen reduction reaction (2e- ORR) for the electrochemical synthesis of H2O2, and discusses how catalyst active sites influence O2 adsorption. Strategies to enhance H2O2 selectivity by regulating these sites are presented. Catalysts require strong O2 adsorption to initiate reactions and weak *OOH adsorption to promote H2O2 formation. The review also covers advances in single-atom catalysts (SACs), multi-metal-based catalysts, and highlights non-noble metal oxides, especially perovskite oxides, for their versatile structures and potential in 2e- ORR. The potential of localized surface plasmon resonance (LSPR) effects to enhance catalyst performance is also discussed. In conclusion, emphasis is placed on optimizing catalyst structures through theoretical and experimental methods to achieve efficient and selective H2O2 production, aiming for sustainable and commercial applications.

Association of biofilm and microbial metrics with healing rate in older adults with chronic venous leg ulcers.

The presence of microbial biofilms in many human chronic wounds led to the hypothesis that biofilms delay healing of these wounds. We tested this hypothesis in a population of 117 older individuals with venous leg ulcers who were receiving standardised therapy, including frequent debridement. Debridement specimens were analysed for the amount of bacterial biomass by two independent methods: a microscopic approach that scored the relative size and number of bacterial aggregates, interpreted as a biofilm metric, and conventional enumeration by agar plating for viable bacteria. The plating protocol yielded three distinct values: the total viable bacterial count, bleach-tolerant bacteria, and the log reduction in viable bacteria upon bleach treatment. Wound healing rates over an 8-week observation period were calculated as the rate of decrease of the equivalent diameter of the wound. There was no statistically significant association between wound healing and the biofilm metric in any of the three analyses performed (p ≥0.15). In all three statistical tests, wound healing was associated with the log reduction caused by bleach treatment (p ≤0.004); wounds that harboured bacteria that were more bleach-susceptible healed more slowly. A refinement of the model of chronic wound infection pathogenesis is proposed in which dormant bacteria constitute a persistent nidus and outgrowth of metabolically active cells impairs healing. This model constitutes a new hypothesis as metabolic activity was not directly measured in this investigation.

Chrysin Nano Formulation Using Cellulose of Rumex vesicarius Herb Leaf Waste: Isolation, Characterization and in-Vitro Evaluation

In this work, for the first time to our knowledge, cellulose was isolated from the Rumex vesicarius herb leaf waste, and cellulose nanospheres (CNS) were developed from this cellulose. Alkali, bleaching, acid hydrolysis, and ultrasonication treatments were used for fabrication of the CNS. The resulting CNS were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential and thermogravimetric analysis (TGA). CNS is considered as an effective nanocarrier to alleviate the problems of some drugs like instability, low water solubility and bioavailability. We used the CNS as an effective nanocarrier for the entrapment of chrysin (CHR), a flavonoid secondary metabolite of the flavone class. By adjusting the solvent composition ratio and processing method, the CHR was entrapped in the CNS and a CNS-CHR nano-formulation was developed. An entrapment efficiency of 88.11% was achieved. FTIR, TGA, XRD and TEM confirmed the entrapment of the CHR in the CNS. The in-vitro dissolution investigation demonstrated an 86.53% release of CHR from the CNS-CHR complex when subjected to a release study and 47.14% of CHR release after 24 h, as the pure CHR is poorly soluble in its pure form. These findings indicate that CNS is a highly effective natural carrier at the nanoscale for CHR owing to easy availability and cost-effectiveness.

Recyclable hemp hurd fibre-reinforced PLA composites for 3D printing

In this study, 3D printing filaments were produced from hemp hurd fibre-reinforced polylactide (PLA) composites. Hemp hurd microfibres were obtained through alkaline digestion followed by a bleaching treatment and were used to produce PLA-based composites with 20–40 wt% fibre content for fused deposition modelling. Tensile testing of 3D printed composites revealed a gradual increase of Young's modulus with the addition of fibres, reaching a maximum of 7.1 GPa for the 40 wt% composite - a two-fold increase to neat PLA. However, tensile strength was only improved for the 20 wt% formulation, with an increase of 8% in comparison with neat PLA. Nevertheless, the thermo-mechanical properties of the composites were significantly enhanced with the addition of fibres. In addition, physical objects were printed from the recycled filaments to assess their recyclability and printability. It was found that the recycled filaments maintained comparable mechanical properties and printability after three recycling cycles.

The influence of dental bleaching on patient's quality of life: A multistudy analysis of aesthetic and psychosocial outcomes

ObjectivesTo assess the Quality of Life (QoL) of participants treated with dental bleaching using different techniques by administering two questionnaires Oral Health Impact Profile (OHIP-14) and Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ), as well as the bleaching efficacy and tooth sensitivity (TS). Materials and MethodsSecondary results for nine randomized clinical trials were included, involving 489 participants who underwent bleaching procedures. The questionnaires were applied at baseline and 30-day post-bleaching. Bleaching efficacy (ΔSGU/ΔEab) and TS were also evaluated (VAS/NRS). The effect of bleaching on aesthetic self-perception was evaluated using the Paired t-test. The Kruskal-Wallis test assessed variations by technique. Also, the correlations between questionnaires and outcomes was evaluated (α = 0.05). ResultsAfter the bleaching treatment, both questionnaire revealed significant differences compared to the baseline, regardless of the factor evaluated (p < 0.05), except for Physical pain in OHIP-14 (p = 0.53). No correlation was found between OHIP-14 and bleaching efficacy (p < 0.008). A significant correlation was found between bleaching efficacy and dental self-confidence, indicating that dental self-confidence increased as the number of SGU (ΔSGU) increased, while social impact (ΔEab) and aesthetic concern (ΔSGU) decreased. Additionally, a significant correlation was observed between TS and OHIP-14 (Physical pain). For PIDAC, both dental self-confidence and psychological impact were correlated with TS in the VAS. ConclusionSubjects who underwent dental bleaching treatment improved their self-perception and dental self-confidence. Dental bleaching, besides enhancing the patient's smile, also improves their self-esteem. Clinical RelevanceDental bleaching, besides improving the patient's smile, also enhances their self-esteem.

Effects of Time-Elapsed Bleaching on the Surface and Mechanical Properties of Dentin Substrate Using Hydrogen Peroxide-Free Nanohydroxyapatite Gel.

There is a critical need to address concerns surrounding the potential impact of bleaching gels specifically on the tooth substrate. Therefore, this laboratory investigation aimed to assess the impact of a hydrogen peroxide (HP)-free bleaching (HiSmileTM) in comparison to an HP-based bleaching (Opalescence RegularTM) on the surface and mechanical characteristics of tooth substrate. Sixty sound human premolar teeth were sectioned to produce dentin fragments and divided into two primary groups based on the bleaching agent used. Each group was subdivided into three subgroups (n = 10) per distinct bleaching regimens: (T1) fragments underwent a 7-day immersion in distilled water at 37°C without any bleaching treatment, (T2) fragments underwent a 7-day immersion in distilled water at 37°C, with the application of bleaching gel occurring on the seventh day for 10minutes, and (T3) fragments underwent a bleaching regimen for seven consecutive days, each session lasting for 10minutes. The initial and final evaluations of surface roughness, nano-hardness, and elastic modulus were performed. Following the bleaching regimens of T3, a composite stub was fabricated on the dentin fragments for the shear bond strength (SBS) test. Statistical testing was accomplished using the analysis of variance (P < 0.05). HP-based bleaching gel showed significant differences between measurement intervals in surface roughness, elastic modulus, and SBS parameters (P < 0.05). In contrast, HP-free bleaching gel showed insignificant differences within the group (P > 0.05). The SBS between dentin-composite was significantly affected with the use of HP-based bleaching gel, while HP-free bleaching gel showed insignificant difference between measurement intervals. The qualitative validation of the treatment's impact was further demonstrated using the scanning electron microscopy. The findings suggest that the bonding stability of composite restorations to dentin may be compromised after bleaching with an HP-based gel, whereas immediate bonding procedures can be safely conducted following the application of an HP-free bleaching gel.

Cellulose, cellulose nanofibers, and cellulose acetate from Butia fruits (Butia odorata): Chemical, morphological, structural, and thermal properties

Cellulose possesses numerous advantageous properties and is a precursor to compounds and derivatives. The objective of this study was to isolate and characterize cellulose from Butia fruits and simultaneously produce cellulose nanofibers and cellulose acetate from the isolated cellulose. Cellulose extraction was performed using a combination of alkaline and bleaching treatments, while the production of cellulose nanofibers and cellulose acetate was achieved through acid hydrolysis and acetylation, respectively. The materials were characterized by their chemical composition, size distribution, zeta potential, morphology, relative crystallinity (XRD), functional groups (FTIR), molecular structure (NMR), and thermal stability (TGA). The Butia crude fibers presented 49.4 % cellulose, 4.5 % hemicellulose, 25.4 % lignin, and 1.3 % ash. The cellulose nanofibers presented an average diameter ranging from 13.7 to 93.1 nm and exhibited a high degree of crystallinity (63.3 %). FTIR, XRD, 13C, and 1H NMR analyses confirmed that the isolation processes effectively removed amorphous regions from the cellulose nanofibers and confirmed the cellulose acetylation process. As demonstrated, cellulosic materials derived from Butia fruit exhibit promise for various applications, including their potential use as reinforcing agents in polymer matrices, due to their high extraction yield, thermal properties, and crystallinity.

Effect of laser irradiation during in-office tooth bleaching on surface properties of resin-based restorative materials.

This study evaluated the changes in surface properties of three resin-based restorative materials after two laser-assisted, in-office tooth bleaching protocols using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) or diode (980nm) lasers. A nanohybrid composite (Enamel Plus HRi), a Bis-GMA-free composite (Enamel Plus HRi Bio Function), and a resin-matrix CAD-CAM ceramic (Shofu Block HC) were tested. Forty specimens for each material were prepared and divided into four groups (n=10/group). The control specimens did not undergo any bleaching treatment, whereas group 2 received bleaching with 40% hydrogen peroxide (H2O2), while groups 3 and 4 underwent the same bleaching procedure with the use of diode (980nm) or Er,Cr:YSGG lasers, respectively. Surface microhardness and roughness measurements were conducted using a Vickers tester and an optical profilometer. Microhardness was lower in bleached specimens, with the nanohybrid composite exhibiting the largest difference from the no bleaching group. For the Bis-GMA-free composite the microhardness difference between no bleaching and laser-assisted bleaching were smaller than seen for the conventional bleaching technique. Surface roughness was higher in bleached specimens, with nanohybrid composite showing the largest differences from the control specimens. The examined laser-assisted tooth bleaching protocols were found not to impact surface microhardness and roughness of the tested resin-based specimens and they are deemed suitable for clinical use.

Valorization of Spent Lignocellulosic Substrate of Edible Mushrooms into Cellulose Nanofibers for Bionanocomposites Production

AbstractAt the present, the spent Pleurotus substrate (SPS), which is a lignocellulosic waste from the industrial production of mushrooms, is poorly valorized and mostly landfilled. Considering the large amount of SPS that is required to produce one kilo of mushrooms and its hazard to the environment if not properly disposed of, finding means to valorize this waste is of utmost importance. This work proposes the valorization of SPS through the extraction of cellulose nanofibers (NC-SPS), by applying several bleaching and alkaline hydrolysis treatments followed by microfluidization. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) of NC-SPS showed that most of the lignin, hemicelluloses, and other impurities were removed after the treatments of SPS. The transmission electron microscopy analysis of NC-SPS showed the presence of nanofibers with an average width of 24.5 ± 14.9 nm, XRD indicated an increase in crystallinity from 60% for SPS to 71% for NC-SPS, while TGA showed that the onset degradation temperature increased with about 43 °C after the treatments. The new NC-SPS are similar to the nanocellulose extracted from wood and can replace it in various applications. In this work, NC-SPS were tested as modifiers for poly(lactic acid) (PLA) leading to an increase in its crystallinity, Young’s modulus (of up to 57%), and storage modulus, while preserving its thermal stability and transparency. These results showed that NC-SPS acted as good reinforcing agents for PLA, and more applications are foreseen.

Extraction and Characterization of Microcrystalline Cellulose (MCC) from Durian Rind for Biocomposite Application

AbstractThe scientific community has become interested in cellulose extraction from agro-industrial wastes because they contain large quantities of cellulose and are being researched globally due to their application. Cellulose extracted from these wastes offers varying characteristics and structures depending on the specific source. In this study, microcrystalline cellulose (MCC) was extracted from different parts of the durian husk through acid hydrolysis with various concentrations of oxalic acid and cellulose-to-acid ratios. The durian husk underwent a pretreatment method involving bleaching and alkaline treatment. The characteristics of MCC, such as functional group, morphology, and crystallinity, were studied. The findings indicated that lignin was successfully removed through pretreatment. However, traces of hemicellulose were still detected in a few samples. The extracted MCCs demonstrated a diameter range from 6.237 to 25.38 μm and crystallinity within the range of 71.43–78.30%. Polycaprolactone (PCL)-based biocomposites with different MCC weights (0.2, 0.5, and 1.0 wt%) were fabricated, and the performance was evaluated through tensile testing and biodegradability tests. The addition of 1.0 wt% MCC enhanced the tensile strength by 22%. SEM analysis revealed the cross-section fracture surface of the biocomposite, indicating the contribution of the MCC during pull-out. Meanwhile, the biodegradability of the biocomposite increased with the addition of MCC, indicating that the MCC-based biocomposite was fully biodegradable.

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.

Preparation and Characterization of Durian Husk-Based Biocomposite Films Reinforced With Nanocellulose From Corn Husk and Pineapple Leaf.

This research explores the integration of corn husk nanocellulose (CHNc) and pineapple leaf nanocellulose (PLNc) as reinforcing agents in a carboxymethyl cellulose-based film derived from durian husk (CMCDH). Through a solvent-casting method, composite films were fabricated with varying nanocellulose contents (15, 30, and 45 wt%). Analysis using Fourier transform infrared spectroscopy and x-ray diffraction confirmed the effectiveness of alkaline and bleaching treatments in eliminating noncellulosic components. Transmission electron microscopy image revealed the rod-like morphology of CHNc and PLNc, with dimensions approximately 206.5 × 7.2 nm and 150.7 × 6.5 nm, respectively. The inclusion of nanocellulose decreased the transparency of CMCDH films while enhancing their tensile strength, thermal stability, and water vapor transmission rate. Notably, CMCDH/PLNc(30%) exhibited the highest tensile strength at 5.06 ± 0.83 MPa, representing a remarkable 220% increase compared to CMCDH biofilm. Thermogravimetric analysis and differential scanning calorimeter results indicated that nanocellulose incorporation delayed the film's decomposition temperature by approximately 10°C. Moreover, CMCDH/PLNc(30%) demonstrated the lowest water vapor transmission rate, marking a 20% improvement. However, the film's properties were compromised at the highest nanocellulose content (45 wt%) due to observed fiber aggregation, as revealed by scanning electron microscopy analysis.

Effects of Different Concentrations of Carbamide Peroxide on Color, Surface Roughness, and Hardness of CAD/CAM Dental Ceramics.

This study assessed the effects of 15% and 20% carbamide peroxide (CP) on color, surface roughness, and hardness of computer-aided design/computer-aided manufacturing (CAD/CAM) dental ceramics. This in vitro study was conducted on 120 Vita Mark II, Celtra Duo, and Suprinity CAD/CAM ceramic specimens. The ceramic specimens in each group (n = 40) were randomly assigned to two subgroups (n = 20) for polishing and glazing, and their baseline color, surface roughness (Ra), and hardness were assessed. In each subgroup, half of the specimens were exposed to 15% CP, while the other half were exposed to 20% CP. Their color change (ΔE), surface roughness, and hardness were then measured again. Surface roughness, hardness, and color were analyzed sequentially by profilometer, Vickers hardness tester, and spectrophotometer, respectively. Data were analyzed by repeated measures ANOVA, one-way ANOVA, and post hoc Bonferroni test (α = 0.05). The surface roughness of all groups significantly increased after bleaching treatment (p < 0.05). Surface hardness of all groups decreased after bleaching treatment, but this reduction was only significant in Vita Mark II subgroups (glazed, polished, 15%, and 20% CP). The ΔE was not clinically and visually perceivable in any group. The present results revealed that concentration of CP and type of surface treatment affected the surface properties of CAD/CAM ceramics. Type of surface treatment only affected the surface hardness of Vita Mark II ceramics (p < 0.05). Concentration of CP had a significant effect only on polished Vita Mark II.

Dental bleaching: patient perception and satisfaction.

Teeth bleaching is a common practice performed by dental hygienists and dentists to correct aesthetic problems due to dental discoloration. Patients' opinions on this procedure may be different according to their personal experiences, expectations and individual sensitivities. The aim of this study is to assess the degree of satisfaction and related sensitivity of patients to professional and home bleaching treatment. A questionnaire consisting of 12 multiple-choice questions was submitted to 625 subjects among general population. These were related to: 1) patient's age and whether the patient is a smoker; 2) personal satisfaction; and 3) post-treatment tooth sensitivity. Descriptive analyses of all variables in the questionnaire were performed, and statistical analyses between variables were carried out by Chi-square test and Fisher's Exact test. Of the people surveyed, 66% performed home bleaching, while the remaining performed the treatment in a dental office. Thirty-three percent of patients had previously undergone teeth bleaching and the 95.7% stated that they were satisfied with the treatment. Of these, only 36.4% reported experiencing postoperative hypersensitivity. Most patients (91.3%) received professional scaling before undergoing bleaching treatment. Patient satisfaction with tooth whitening treatment can vary from patient to patient and represents a strong indicator of treatment efficacy and suitability. A proper communication, careful management and individualized patient assessment are key to maximizing satisfaction and ensuring a positive and fulfilling patient experience.

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.

OPTIMIZATION OF THE EXTRACTION AND PREPARATION OF CELLULOSE MICROFIBERS FROM RICE HUSK USING A FULL FACTORIAL EXPERIMENT

Cellulose is one of the most abundant biopolymers on Earth and is of most significant interest due to its properties and uses. Cellulose can be obtained from agro-industrial residues, such as rice husk, whose cellulose content is approximately 30%. In this study, cellulose microfibers were extracted from rice husks. Fibers were obtained by submitting the biomass to alkali (NaOH) and bleaching treatments. These treatments have already been reported in the literature; however, variables such as the concentration of reagents, the time, and the temperature of the chemical treatment have yet to be optimized. A factorial design of experiments with 3 factors and 2 levels for each factor was proposed to optimize the chemical processes. It was determined through the analysis of variance (ANOVA) that the factors evaluated significantly influenced the elimination of non-cellulosic compounds, and that the chemical treatment was more efficient when the factors took high level values. Ultraviolet-visible spectroscopy (UV-Vis) analysis showed the successful removal of undesired components during the alkaline treatment. The effect of the treatments on the morphology upon removing hemicelluloses, lignin, and inorganic material was evaluated through Scanning Electron Microscopy (SEM). The increase in the thermal stability in the alkali-treated rice husk and in cellulose microfibers, compared to the raw rice husk, was established by thermogravimetric analysis (TGA). X-ray diffraction (XRD) indicated that the treatments increased the percentage of crystallinity.