Color Alteration Research Articles

Sustainable Smart Packaging from Protein Nanofibrils.

Smart packaging technologies are revolutionizing the food industry by extending shelf life and enhancing quality monitoring through environmental responsiveness. Here, a novel smart packaging concept is presented, based on amyloid fibrils (AM) and red radish anthocyanins (RRA), to effectively monitor food spoilage by color change. A protein nanofibrils biofilm is developed from whey protein, which is functionalized with RRA to endow the resulting films with advanced monitoring capabilities. A comprehensive characterization, including pH responsiveness, water vapor permeability, thermal and mechanical testing, and colorimetric responses, demonstrates the superiority of AM/RRA films compared to control films based on whey monomer building blocks. The findings indicate that the AM/RRA films can effectively monitor, for example, shrimp freshness, showing visible changes within one day at room temperature and significant alterations in color after two days. Furthermore, these films exhibit high antibacterial and antioxidant activities, reinforcing their suitability for efficient food packaging. By integrating bio-based materials from whey and natural anthocyanins, this research presents a biodegradable, sustainable, and cost-effective smart packaging solution, contributing to eco-friendly innovations in food preservation.

Precise Tool to Target Positioning Widgets (TOTTA) in Spatial Environments: A Systematic Review.

TOTTA outlines the spatial position and rotation guidance of a real/virtual tool (TO) towards a real/virtual target (TA), which is a key task in Mixed reality applications. The task error can have critical consequences regarding safety, performance, and quality, such as surgical implantology or industrial maintenance scenarios. The TOTTA problem lacks a dedicated study and it is scattered in different domains with isolated designs. This work contributes to a systematic review of the TOTTA visual widgets, studying 70 unique designs from 24 papers. TOTTA is commonly guided by the visual overlap -an intuitive, pre-attentive "collimation" feedback- of simple shaped widgets: Box, 3D Axes, 3D Model, 2D Crosshair, Globe, Tetrahedron, Line, Plane. Our research discovers that TO and TA are often represented with the same shape. They are distinguished by topological elements (e.g. edges/vertices/faces), colors, transparency levels, and added. shapes, widget quantity, and size. Meanwhile some designs provide continuous "during manipulation feedback" relative to the distance between TO and TA by text, dynamic color, sonification, and amplified graphical visualization. Some approaches trigger discrete "TA reached feedback" such as color alteration, added sound, TA shape change, and added text. We found the lack of golden standards, including in testing procedures, as current ones are limited to partial sets with different and incomparable setups (different target configurations, avatar, background, etc.). We also found a bias in participants: right-handed, young male, non-color impaired.

Amorphous NiO nanopyramids with superior electrochromic energy storage properties

In this work, amorphous NiO nanopyramid film has been obtained by using the pulsed magnetron sputtering technique. The uniform amorphous NiO nanostructures exhibit significant electrochromic modulation efficiency in the visible and near-infrared ranges, achieving a high modulation efficiency of 60.73 % at 550 nm and 21.58 % at 1500 nm. It exhibits rapid response time (coloring takes 2.4 s, and bleaching takes 1.0 s) and significant coloring efficiency (43.23 cm2C-1). Moreover, amorphous NiO nanopyramid film displays promising properties of energy storage. The NiO nanopyramid film shows high areal capacitance (7.08 mF/cm2), along with satisfying rate capability. The alteration in the electrode color offers a convenient method for monitoring the quantity of energy stored. Furthermore, the microstructure characteristic, degree of crystallization and electrochemical performance of the NiO film are significantly influenced by both oxygen partial pressure and sputtering time. These findings highlight the potential of employing this bifunctional amorphous NiO nanopyramid film in diverse advanced nanodevices, encompassing electrochromic energy storage applications with superior performance.

Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions.

This study evaluated effects of various solutions on color stability and surface hardness of a nanohybrid dental composite in simulated oral environments. Sixty-four composite disks were fabricated and randomly allocated into eight groups (n = 8 per group): Artificial saliva (AS), Biotene (B), passion fruit juice (PFJ), orange juice (OJ), Sprite (S), Coca-Cola (CO), apple cider vinegar (ACV), and cranberry juice (CJ). Specimens were immersed in respective solutions at 37°C for 28 days. Surface microhardness was assessed using Vickers microhardness test, and color alterations were quantified using SpectroShade Micro spectrophotometer. Measurements were taken 24 hours after initial polymerization and after 28-day immersion period. Statistical analysis was performed using mixed model ANOVA. After 28 days, specimens exhibited significant changes in microhardness and color. Polished surfaces showed microhardness decreases of 21.9-35.5%, with ACV and CJ causing largest reductions. Non-polished surfaces unexpectedly showed increased microhardness (11.2-17.4%). Color changes were more pronounced on polished surfaces, with CO and CJ causing maximum alterations. Statistical analysis revealed significant interactions between surface treatment, staining media, and immersion time (p < 0.05). All experimental groups demonstrated significant changes, highlighting composite materials' susceptibility to environmental factors. Even well-polymerized and polished surfaces underwent alterations, emphasizing necessity for periodic follow-up and maintenance polishing in esthetic restorations. The present research emphasizes significance of oral environmental factors on composite restoration longevity and esthetics, advocating for patient education on dietary impacts and tailored maintenance strategies to preserve restoration quality. How to cite this article: Shetty P, Jayakumar HDN, Pulickal TJ, et al. Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions. J Contemp Dent Pract 2024;25(7):669-676.

A colorimetric paper based on curcumin-loaded CD-MOFs and CNFs for visual monitoring of strawberry freshness

Curcumin is a natural yellow colorant, but the color variation occurs only under alkaline conditions, limiting the monitoring range for food freshness. In this study, curcumin obtained the property of acid-responsive color transition from red to yellow by encapsulating in alkaline CD-MOFs. Then, the curcumin-loaded CD-MOFs (CD-MOFs-Cur) with red color was incorporated in cellulose nanofibrils (CNFs)/ethanol suspensions forming a colorimetric paper through the wet-forming process. Results showed that the cubic CD-MOFs-Cur was evenly distributed in the network of CNFs. With the increase amount of CD-MOFs-Cur, the paper exhibited a redder color, but all exhibited high color stability. In pH 5–10 buffer solutions, the paper showed obvious color change from red to yellow with the pH decreased, but the pH that induced the color of the paper turn to yellow was lower with the increase of CD-MOFs-Cur amount. Similar color alteration also occurred when CD-MOFs-Cur was exposed to CO2. Based on this, the CNFs/CD-MOFs-Cur composite paper was successfully used for visual monitoring of strawberry freshness. This work provides the possibility for curcumin to detect the freshness of foods that release acid gases during spoilage.

Improvement of Hygienic and Phytochemical Qualities of Mangosteen (Garcinia Mangostana) Peel by Irradiation

The aim of this study was to compare the effects of gamma ray and x-ray irradiation at different dose levels 95, 10, 15 and 20 kGy) on in mangosteen peel. The antioxidant activities were assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP), while total phenolic contents and antibacterial activities against Staphylococcus aureus and Escherichia coli of 60 % ethanolic mangosteen powder extracts were analyzed. The results indicated that both types of ionizing radiations showed a non-significant decrease in measured parameters with increasing doses. The minimum inhibitory concentration (MIC) values of irradiated mangosteen peel extracted against S. aureus and E. coli ranged from 0.125 to 2.0 mg/mL. The quantity of bioactive compound mangostin determined via high-performance liquid chromatography (HPLC), did not show significant decrease with different irradiation sources and doses. In microbiological aspect, total yeast and mold from both irradiation sources were reduced by 1 log cycle after irradiation at 5 kGy. The irradiation induced color changes corresponding to Hunter color L a b value. X-ray irradiation caused slight color alteration compared to gamma rays. The advantage of x-ray irradiation was that it revealed non-significant changes in b values, whereas gamma irradiation showed the significant change in L, and b values with increasing dosage. The x-ray irradiation at the dose 5 kGy effectively decreased microbial contamination while causing minimal changes to phytochemical qualities and color. HIGHLIGHTS Irradiation at 5 kGy was sufficient to control microbial contamination There were no significant changes in antioxidant activities (DPPH, FRAP), a-mangostin contents, total phenolic contents (TPC) and antibacterial activities: after irradiation up to 20 kGy X-ray irradiation was an excellent alternative to gamma irradiation for decontamination with a non-significant alteration in b values. GRAPHICAL ABSTRACT

Efficacy of zinc and copper oxide nanoparticles as heat and corrosion-resistant pigments in paint formulations

This study focuses on the synthesis of zinc and copper oxide nanoparticles using green methods by plant extracts. The resulting metal oxides were analyzed using FT-IR spectroscopy, TGA, TEM, zeta potential and assessed for their efficacy as pigments based on properties such as Hydrogen Ion Concentration, Oil absorption, Moisture Content, Fineness of grinding, Bleeding, and loss on ignition. The results confirmed that the prepared ZnO and CuO nanoparticles exhibited the formation of nanoparticles in the range of 10–40 nm with potential as pigments. Two paint formulations incorporating these nanoparticles and silicon resins as binders were tested for physico-mechanical attributes, chemical resistance, heat resistance, and corrosion resistance of the dry paint films. The study found that the films containing the prepared oxides demonstrated excellent performance, with no damage or color alteration observed after exposure to temperatures up to 500 °C. Moreover, the paint films containing ZnO nanoparticles showed superior efficiency after a 500 h salt spray test compared to those with CuO nanoparticles. These findings suggest that the synthesized mixed oxide nanoparticles are promising candidates for heat-resistant pigment applications.

Mycotoxin Detection through Colorimetric Immunoprobing with Gold Nanoparticle Antibody Conjugates.

Driven by their exceptional optical characteristics, robust chemical stability, and facile bioconjugation, gold nanoparticles (AuNPs) have emerged as a preferred material for detection and biosensing applications in scientific research. This study involves the development of a simple, rapid, and cost-effective colorimetric immuno-sensing probe to detect aflatoxin B1 and zearalenone using AuNP antibody (AuNP-mAb) conjugates. Anti-toxin antibodies were attached to the AuNPs by using the physical adsorption method. The colorimetric immunosensor developed operates on the principle that the optical properties of the AuNP are very sensitive to aggregation, which can be induced by a critical high salt concentration. Although the presence of antibodies on the AuNP surface inhibits the aggregation, these antibodies bind to the toxin with higher affinity, which leads to exposure of the surface of AuNPs and aggregation in a salt environment. The aggregation triggers a noticeable but variable alteration in color from red to purple and blueish gray, as a result of a red shift in the surface plasmon resonance band of the AuNPs. The extent of the shift is dependent on the toxin exposure dose and can be quantified using a calibration curve through UV-Visible-NIR spectroscopy. The limit of detection using this assay was determined to be as low as 0.15 ng/mL for both zearalenone and aflatoxin B1. The specificity of the prepared immunoprobe was analyzed for a particular mycotoxin in the presence of other mycotoxins. The developed immunoprobe was evaluated for real-world applicability using artificially spiked samples. This colorimetric immunoprobe based on localized surface plasmon resonance (LSPR) has a reduced detection limit compared to other immunoassays, a rapid readout, low cost, and facile fabrication.

Effect of Different Drying Methods on Colour, Total Phenolic Content, Flavonoid Content, and Antioxidant Activity Retention of Strobilanthes crispus Leaves

Strobilanthes crispus, a medicinal herb, is recognised for its abundant phytochemicals, notably in its leaves, contributing to its high antioxidant activity. However, the crucial step of drying, aimed at extending shelf life, can impact the stability of these bioactive compounds. This study evaluates the impact of different drying methods, which include oven, microwave, freeze drying, and air drying, on the colour, phenolic and flavonoid content, and antioxidant activities of S. crispus leaves. The colour analysis of the fresh and dried leaves was assessed using the chromameter. Total phenolic content (TPC) and total flavonoid content (TFC) were determined using Folin-Ciocalteu’s and aluminium chloride colourimetric assays, respectively. Antioxidant capacities were analysed via ferric-reducing antioxidant power (FRAP) and a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The results showed that microwave-dried S. crispus leaves exhibited minimal alterations in colour attributes L*, a*, and b*, closely resembling the fresh leaves (p &gt; 0.05). Microwave drying significantly preserved TPC (145.42 ± 1.61 mg GAE/g), TFC (117.27 ± 5.10 mg QE/g), FRAP activity (258.92 ± 0.15 µg TE/g extract), and displayed the most potent DPPH scavenging half-maximal inhibitory concentration (7.58 ± 0.48 µg/ml) compared to other methods (p &lt; 0.05). Notably, the DPPH scavenging potency surpassed that of the synthetic antioxidant butylated hydroxytoluene. In conclusion, microwave drying appeared to be an efficient method for preserving the colour and antioxidant properties of S. crispus leaves. It highlights its potential as a favourable drying technique for conserving bioactive compounds in medicinal plant materials, offering promising applications in the nutraceutical and pharmaceutical fields.

Value of Strain Elastography in Evaluation of Supraspinatus Tendinopathy in Patients with Chronic Shoulder Pain, A Comparative Study to MRI

Abstract Background Rotator cuff disorders are one of the most important causes of chronic shoulder pain and the clinical differentiation between the different rotator cuff disorders is difficult and imaging is mandatory for diagnosis and proper assessment of rotator cuff abnormalities. The most commonly used imaging modalities are ultrasonography (US) and magnetic resonance imaging (MRI) with MRI is the reference standard for imaging of rotator cuff disorders yet its use is hindered by high cost and MRI contraindications. Aim of the Work to assess role of SEL in the evaluation of supraspinatus tendon abnormalities and to evaluate the relationship between the measured strain ratio and the MRI grade of tendinopathy. Patients and Methods Our study included 40 patients with chronic shoulder pain including 11 patients with no evident tendinopathy on MRI (grade 0) (27.5%) 9 patients with grade I tendinopathy (22.5 %), 10 patients with grade II tendinopathy (25 %) and 10 patients (25 %) with supraspinatus tendon tear (grade III). Results Our study showed that normal supraspinatus tendons appear homogenous and stiff with high strain ratios, whereas pathological ones showed a more heterogenous and reduced stiffness pattern with intratendinous color alterations and lower strain ratios. This is explained by the fact that tendinopathy leads to collagen fiber degeneration and breaking down, resulting into tendon softening and weakness. Our study also showed strong linear association between the MRI grade and the stiffness indicated by the strain ratios (p &amp;lt; 0.05). There was a perfect negative correlation grade of tendinopathy and SEL strain ratio. As tendinopathy increased, tendons became softer which was indicated by the reduced strain ratio values. These findings were in agreement with many previously published studies. Conclusion The application of SEL in musculoskeletal system is not well established, but this study showed that SEL can detect differences between the normal and diseased rotator cuff tendons with good correlation to MRI with other studies showed improved sensitivity, specificity and accuracy in detection of tendon abnormalities. It can also add further important information to conventional shoulder imaging such as tendon quality which considered as a prognostic factor for rotator cuff repair.

Effect of whitening dentifrices on dental enamel: an analysis of color, microhardness, and surface roughness in vitro.

This study aimed to evaluate the influence of different whitening toothpastes on color change and alteration in enamel surface roughness and microhardness compared to a conventional toothpaste. Fifty bovine incisors were selected, cleaned, and stored before being divided into five groups: a conventional toothpaste group and three whitening toothpaste groups containing different abrasive agents: silica, hydrogen peroxide, and activated charcoal. Specimens underwent simulated brushing, staining with black tea solution, and subsequent analyses of color, surface roughness, and microhardness. Statistical analysis was performed using three-way ANOVA and Tukey post-hoc tests (P .05). The results showed that the color analysis revealed similar whitening potential among all toothpastes. They showed significant differences in surface roughness (P .001) and microhardness (P .001) after simulated brushing. While all toothpastes caused a decrease in microhardness, the charcoal-based toothpaste showed a significant increase in surface roughness compared to the initial condition. All toothpastes demonstrated whitening capability. Surface roughness changed after brushing with activated charcoal-based whitening toothpaste, but final roughness was similar across all groups. Whitening toothpastes led to a decrease in enamel microhardness, with similar final performance across all toothpastes analyzed.

Integrating Microwave Heating with Foam-Mat Drying: Drying Kinetics and Optimization for Thick Foamed Mango Pulp

This study addresses the challenge of processing undersized or overripe mangoes by integrating microwave heating with traditional foam-mat drying technique. The study aims at investigating drying kinetics coupled with thin-layer drying modeling and influences of microwave power (300 - 600 W) and hot-air temperature (55 - 75 °C). Among ten drying models, the so-called Midilli equation fitted well with experimental data. Results showed enhanced drying process associated with microwave heating, providing reduced drying time from 600 - 700 min (for conventional hot-air mode) to 30 - 100 min (for microwave-assisted mode). Standard deviations of moisture content and dried foam thickness measured at various points revealed uneven heat distribution when using high microwave energy, evidenced by burnt spots at 600 W. Additionally, foam collapse was observed under the mild process with low microwave powers, possibly due to prolonged drying periods. Response surface methodology demonstrated that microwave power was more important factor, positively affecting effective diffusivity coefficient (Deff) while inversely influencing specific energy consumption (SEC) and color difference (DE). Deff value increased from 5.41´10-6 m²×s-1 at 300 W and 55 °C to 18.43´10-6 m²×s-1 at 600 W and 75 °C, confirming enhance drying performance. As assisted with microwave heating, drying foamed mango sample consumed less energy up to 92 %. Optimal drying parameters were determined based on balancing the enhancement of drying performance and color alteration, suggesting drying the thick foamed mango pulp at temperature of 55 °C combined with microwave heating at 520 W, which can be served as a basis for further industrial scale-up. HIGHLIGHTS Novel method for thick mango pulp snacks. Reduced drying time from 600 - 700 to 30 - 100 min. Lowered energy use to 5.83 kWh×kg-1. Optimal conditions at 520 W, 55 °C, desirability 0.669. Applied Midilli model with 99 % accuracy. GRAPHICAL ABSTRACT

Integrated OPECT and Smartphone Colorimetry Dual‐Mode Detection of Okadaic Acid Based on Ce‐MOF Modified MXene@SnO2 Z‐Scheme Heterostructure

AbstractThe organic photoelectrochemical transistor (OPECT) biosensing relies solely on a singular signal readout inherently, which restrains the precision and dependability nestled within pertinent biological measurements. Herein, a high‐precision magnetic assisted OPECT and smartphone colorimetric (SCL) dual‐mode biosensing platform is first established for detecting harmful algal toxin okadaic acid (OA) by biocatalytic reaction. MXene@SnO2‐Ce‐MOF (MXSnO/Ce‐MOF) Z‐scheme heterojunctions with abundant oxygen vacancies are prepared as photoactive materials. Initially, in the presence of OA, the coupling of trigger DNA (tDNA) to magnetic beads (MBs) via anchor DNA (aDNA) is released through the interaction of the target analyte with the aptamer. Subsequently, the carried tDNA triggers HCR between the two hairpin sequences, producing long double helix chains to capture glucose oxidase (GOx). The obtained GOx supernatant catalyzes glucose to produce H2O2, which can oxidize Ce‐MOF, leading to the alteration of electrode color and a significant decrease in the overall photocurrent of MXSnO/Ce‐MOF. Crucially, the novel OPECT‐SCL biosensor exhibits excellent sensitivity and precision, boasting detection thresholds as low as 42.9 pM and 1.2 nM, respectively, and accomplishes the automated detection of OA within real samples. The proposed OPECT‐SCL dual‐signal measurement model constitutes a sensitive, portable, and precise platform for the quantification of marine toxins.

A Survey of Image Enhancement and Dehazing Algorithms to Improving Autonomous Navigation in Fog and Dust.

Video captured during sand-dust weather conditions indicates significant degradation, diminished contrast, and pronounced color distortion. The reason behind this phenomenon is the impact of sand-dust particles, which result in the dispersion and assimilating of light. Consequently, resultant image seems blurred and lacks contrast. Additionally, the alteration in color is attributed to the swift reduction of blue light. Adverse weather circumstances, such as fog, sand, and dust storms, cause problems with vision for deploying self-driving automobiles. To guarantee secure and seamless operations during frequent adverse weather conditions, video enhancement plays a vital role in facilitating vehicular mobility and navigational in both road and air transportation. To improve the safety and efficiency of operation, it is imperative to employ video dehazing techniques, particularly in adverse weather conditions. The purpose of our overview is to offer interested researchers a thorough and methodical examination of image enhancement approaches, serving as an important point of reference for their work. The text explored different image enhancement methods, along with the challenges, constraints, advantages, and drawbacks associated with using these techniques throughout the past five years. Specifically, it focused on three aspects: supervised algorithms, unsupervised algorithms, and quality evaluation.

How to improve photographs with smartphones for oral telemedicine

Photographic images are an essential tool in oral medicine practice, even though their value is conditioned by their quality. Digital photography using smartphones (SPhs) has had many advances, nowadays allowing the acquisition of high-quality pictures. Compared to professional cameras, it has advantages and disadvantages. The latter comprise photographs out of focus, poorly framed, and lighting problems due to shadows, artifacts, and color alterations, among other problems mainly mediated by the operator. Such defects can limit the proper interpretation of the image representing the patient’s condition. This perspective aims to describe the basic concepts of photography and the functional features of SPhs. This will allow programming those devices properly for oral telemedicine (OTM), understanding their limitations, and correcting errors for the photographs to be used effectively. We also include empirical solutions and illustrations showing that photography with SPhs could be easily executable by any health professional and even by the patients themselves.

A novel color-aided system for diagnosis of early gastric cancer using magnifying endoscopy with narrow-band imaging.

The Pink Zone Pattern (PP) sign is a typical color alteration of early gastric cancer (EGC) under magnifying endoscopic narrow-band imaging (ME-NBI). By integrating the color changes (PP sign) with the "vessel plus surface (VS)" classification system, we developed an innovative diagnostic system for EGC and named it "Pink Microsurface Microvascular (PSV)" system. Here, we aimed to elucidate the diagnostic performance of the PSV system for EGC. We conducted a single-center prospective clinical study (before-after design) consisting of 2 cross-sectional studies at 2 separate periods. In the before phase, 184 suspected lesions were evaluated using the VS system under ME-NBI; in the after phase, 183 suspected lesions were evaluated using the PSV system. We compared the diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) between the VS group and the PSV group. The accuracy, sensitivity, specificity, PPV, and NPV of the VS system for EGC were 84.6%, 87.0%, 83.6%, 67.8%, and 94.2%, respectively, and those for the PSV system were 93.0%, 92.0%, 93.4%, 85.2%, and 96.6%, respectively. The accuracy, specificity, and PPV of the PSV system were superior to those of the VS system. However, the sensitivity and NPV did not significantly differ between the VS system and the PSV system. The VS system was inconclusive for 22 lesions (12.0%) and the PSV system was inconclusive for 11 lesions (6.0%). The PSV system could identify more suspicious lesions than the VS system. We propose a new PSV diagnostic system by combining the VS system and the PP sign. Compared with the VS system, the PSV system could identify more suspected lesions and improve the diagnostic performance of EGC.

Thermal chemical pretreatment of waste-activated sludge for enhanced solubilization and biogas production: a review

ABSTRACT Waste-activated sludge (WAS) generation is increasing due to the increased generation of wastewater owing to industrialization and urbanization. The disposal of WAS is a significant environmental and financial concern that can be offset by stabilization and valorization via anaerobic digestion (AD). However, the biodegradation is limited due to microbial cells and extracellular polymeric substances (EPS). Physical, chemical, biological, and hybrid pretreatments and the addition of accelerant materials for enhancing direct interspecies electron transfer (DIET) are among the strategies to overcome the poor biodegradation of WAS. Alkaline pretreatment disintegrates the floc structure of WAS by increasing the osmotic pressure, while microwave irradiation has thermal and a-thermal effects and increases the availability of organics for biodegradation. Moreover, the combination of alkaline and thermal pretreatments has synergic effects on solubilization, biogas production, and dewaterability. The disintegration of WAS is recognized by alteration in volatile solid (VS) content, sCOD, BOD/sCOD, turbidity, nutrients solubilization, dewaterability, particle size, specific surface area, change functional group, alteration in microorganism community, microorganism abundance, color, moisture content, lag phase, and biogas production. Higher doses of pretreatment increase COD solubilization but not biodegradable COD. Maximum COD solubilization ranged from 2 to 37% in alkaline, 21 to 260% in the microwave (MW), and 28 to 624% in hybrid pretreatments.

Structural color of metallic glass through picosecond laser

Abstract The alteration in surface color of metallic glasses (MGs) holds great significance in the context of microstructure design and commercial utility. It is essential to accurately describe the structures that are formed during the laser and color separation processes in order to develop practical laser coloring applications. Due to the high oxidation sensitivity of La-based metallic glass, it can broaden the color range but make it more complex. Structure coloring by laser processing on the surface of La-based metallic glass can be conducted after thermoplastic forming. It is particularly important to clarify the role of structure and composition in the surface coloring process. The aim is to study the relationship between amorphous surface structural color, surface geometry, and oxide formation by laser processing in metallic glasses. The findings revealed that the periodic structure primarily determines the surface color at laser energy densities below 1.0 J/mm2. In contrast, the surface color predominantly depends on the proportion of oxides that are formed when energy densities exceed 1.0 J/mm2. Consequently, this study provides a novel concept for the fundamental investigation of laser coloring and establishes a new avenue for practical application.

Effect of glass infiltration and modified cooling rates on color characteristics alteration of monochrome and multilayer high yttrium oxide containing zirconia.

Sintering technique impacted color of zirconia. This study examined the effect of glass infiltration and altering cooling rate on color alteration of monochrome (Mo) and multilayer (Mu) 5 mol% yttria-partially stabilized zirconia (5Y-PSZ). 180 specimens (width, length, thickness = 10, 20, 2 mm) were prepared from Mo and Mu (comprising cervical (C) and incisal (I) zone) 5Y-PSZ shade VITA-A2. Unintentionally categorized samples (n=15/group) were sintered with traditional (T) versus glass infiltrated (G) technique and cooled down with slow (S: 5°C/min), normal (N: 35°C/min), and fast (F: 70°C/min). CIE-L*a*b* color characteristics were determined for translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), and color difference (∆Ediff). Microstructures were investigated with SEM and XRD. ANOVA and Tamhane's comparisons were determined for significant differences (p<0.05). TP and OP were significantly higher for Mo than MuC and MuI, but no significant difference in CR among them. Comparable ΔEdiff between Mo and MuC were indicated, but both were significantly lesser than MuL. Glass infiltration and raising cooling rate significantly decreased TP and OP, whereas increased CR and ΔEdiff, which amplified color alteration. Glass infiltration sintering and modified cooling rate significantly altered color parameters of 5Y-PSZ. Monochrome demonstrated higher translucency and opalescence than multilayer, possibly due to colorant additives. Glass infiltration decreased translucency and opalescence due to different refractive indices. Increased cooling rate resulted in decreasing translucency and opalescence due to smaller grain size and t→m transformation. Nevertheless, altered sintering and cooling rates still rendered an acceptable color alteration. Key words:Cooling rate, glass infiltration, optical characteristics, translucency.

The impact of Streptococcus mutans biofilms on the color stability and topographical features of three lithium disilicate ceramics.

Secondary caries around ceramic restorations is the most common reason for the replacement of fixed dental prostheses (FDPs). Therefore, it is important to examine the susceptibility of different ceramic materials to biofilm formation. This study aimed to evaluate biofilm development and associated roughness and color alterations in three lithium disilicate ceramics: Emax CAD (EC), Emax Press (EP), and LiSi Press (LP). Streptococcus mutans biofilms were grown on the three ceramics (n = 10 per group) for 7 days. Surface roughness values and color alteration were assessed before and after the biofilm using a non-contact profilometer and spectrophotometer, respectively. Biofilm growth was evaluated using colony-forming units (CFUs) and scanning electron microscope (SEM) images. The data were analyzed using one-way ANOVA and Tukey tests. There was a significant (p≤0.001) growth of S. mutans colonies on EC (6.75 ± 0.56) and EP (6.72 ± 0.54) specimens compared to LP, which showed no biofilm growth. The change in average surface roughness (∆Ra, nm) was significantly lower (p < 0.001) in the EC specimens (0.029 ± 0.003) compared to the EP (0.055 ± 0.012) and LP (0.041 ± 0.010). When the changes in the Rv and Rt values were investigated, no significant difference was observed among the groups. Following the biofilm challenge, the change in color (∆E00) was significantly lower (p = 0.005) in the LP group (1.68 ± 1.45) compared to the EC group (3.89 ± 1.50) and no significant difference was observed between the EP group (2.74±1.01) and the other two ceramics (p ≥ 0.05). LP ceramics exhibited superior resistance to S. mutans biofilm formation and associated changes in surface roughness and color compared to the Emax CAD and Emax Press ceramics. These findings suggest that the LiSi Press material may be more favorable to mitigate the risk of secondary caries.