Search Results (244)

Biomimetic restorative dentistry aims to preserve tooth structure and achieve optimal aesthetic harmony with surrounding dentition. The principles and protocols associated with biomimetic restorative dentistry are designed to enhance the longevity of the restoration. The use of flowable CRs is increasingly common; however, the effect of viscosity on the discoloration has not been clearly established. This in vitro study aimed to assess the color stability of flowable CRs with varying viscosities following immersion in common staining solutions and subsequent repolishing. A total of 250 disc-shaped specimens (8 mm × 2 mm) were prepared from five CRs with different viscosity profiles: high-viscosity (Spectra STHV, Dentsply, Milford, DE, USA), medium-viscosity (Estelite Universal Flow Medium, Tokuyama Dental Co., Tokyo, Japan), bulk-fill (Estelite Bulk-Fill Flow, Tokuyama Dental Co., Tokyo, Japan; SDR Plus, Dentsply, Milford, DE, USA), and packable (Estelite Posterior, Tokuyama Dental Co., Tokyo, Japan). After polymerization and baseline color measurements, specimens were immersed in coffee, tea, cola, red wine, or distilled water for 144 h. Color values were recorded before and after staining, and again following repolishing. Color changes (ΔE₁, ΔE₂, ΔE₃) were calculated using the CIE Lab system and statistically analyzed via two-way ANOVA and Tukey HSD (α = 0.05). Both the CR type and the staining solution substantially affected the color change. SDR Plus exhibited the highest ΔE values. Red wine caused the most discoloration. Repolishing enhanced color in selected groups. Full article

Background: The rising demand for aesthetic dental treatments has spurred interest in peroxide-free color correctors as alternatives to traditional hydrogen peroxide formulations, which are associated with tooth sensitivity and potential enamel demineralization. This systematic review evaluates the whitening efficacy and safety profile of hydrogen peroxide-free color corrector (HPFCC) products, focusing on color change metrics, enamel and dentin integrity, and adverse effects. Methods: Following PRISMA guidelines, we searched PubMed, Scopus, and Web of Science throughout January 2025 for randomized controlled trials, observational studies, and in vitro experiments comparing HPFCC to placebo or peroxide-based agents. The data extraction covered study design, sample characteristics, intervention details, shade improvement (ΔE00 or CIE Lab), enamel/dentin mechanical properties (microhardness, roughness, elastic modulus), and incidence of sensitivity or tissue irritation. Risk of bias was assessed using the Cochrane tool for clinical studies and the QUIN tool for in vitro research. Results: Six studies (n = 20–80 samples or subjects) met the inclusion criteria. In vitro, HPFCC achieved mean ΔE00 values of 3.5 (bovine incisors; n = 80) and 2.8 (human molars; n = 20), versus up to 8.9 for carbamide peroxide (p < 0.01). Across studies, HPFCC achieved a mean ΔE00 of 2.8–3.5 surpassing the perceptibility threshold of 2.7 and approaching the clinical acceptability benchmark of 3.3. Surface microhardness increased by 12.9 ± 11.7 VHN with HPFCC (p < 0.001), and ultramicrohardness rose by 110 VHN over 56 days in prolonged use studies. No significant enamel erosion or dentin roughness changes were observed, and the sensitivity incidence remained below 3%. Conclusions: These findings derive from one clinical trial (n = 60) and five in vitro studies (n = 20–80), encompassing violet-pigment serums and gels with differing concentrations. Due to heterogeneity in designs, formulations, and outcome measures, we conducted a narrative synthesis rather than a meta-analysis. Although HPFCC ΔE00 values were lower than those of carbamide peroxide, they consistently exceeded perceptibility thresholds while maintaining enamel integrity and causing sensitivity in fewer than 3% of subjects, supporting HPFCCs as moderate but safe alternatives for young patients. Full article

Bioactive resin-based cements (RBCs) were recently introduced, but data on their color stability remain limited. This study analyzed the impact of thermal cycling on the color and whiteness of bioactive RBCs. Specimens (n = 10) were fabricated from Panavia SA Universal (PN), Predicta Bioactive Cement (PR), and ACTIVA BioACTIVE cement (AC). CIE Lab* values were registered at baseline and after 5000, 10,000, and 15,000 thermal cycles (5–55 °C). Changes in color (ΔE₀₀) and whiteness index (ΔWI_D) were calculated and compared. Material type and thermal cycling significantly affected ΔE₀₀ and ΔWI_D (p < 0.001). AC showed the highest ΔE₀₀ values at all stages (p < 0.001), with a progressive increase over time. PN differed significantly between early and later cycles (p < 0.05), while PR remained stable (p > 0.05). Analysis of color parameters indicated that AC underwent the most pronounced changes, particularly in Δa and Δb, while PN exhibited the greatest shift in Δb. For ΔWI_D, PR had significantly lower values than PN (p < 0.05) and AC (p < 0.001), with no difference between PN and AC (p > 0.05), and thermal cycling significantly affected all groups, with PR and AC differing across all stages (p < 0.05). Thermal cycling significantly influenced the color stability and whiteness of bioactive RBCs, with AC exhibiting the greatest changes over time, while PR demonstrated superior stability. Full article

In this work, biocomposites of polylactic acid (PLA) and polypropylene (PP) with micronized cellulose (MC) were produced by mold injection and subjected to accelerated aging with ultraviolet (UV) radiation. The tests took place over 10 weeks, during which the produced specimens were exposed to a total of 1050 h of ultraviolet light. During the UV aging test, images were captured, and spectral reflectance and colorimetric measurements were carried out on the specimens exposed to UV and on specimens of the same materials kept in the dark (originals). As expected, only residual color differences were observed in the original specimens with values of ΔE*_ab always below 0.5. On the other hand, spectral reflectance and colorimetric changes were noticed over time in the specimens subjected to UV radiation. In particular, the values of ΔE*_ab increased over time and were found to be higher for PLA with MC compared to PP with MC. Values of ΔE*_ab = 4.7, 9.0, and 10.4 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PLA with MC, whereas ΔE*_ab = 4.5, 6.8, and 7.3 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PP with MC. Therefore, it was found that the specimens of PLA with MC showed greater color fading compared to the specimens of PP with MC when subjected to UV exposure. In addition, it was also found in this work that besides the color differences noted in the tested specimens, those made of PP with MC also showed signs of surface damage. Full article

The common bean is a widely cultivated food source. Many domesticated species of common bean varieties, known as landraces, are cultivated in Mexico by local farmers, exhibiting various colorations and seed mixtures as part of agricultural practices. In this work, we propose a methodology for classifying bean landrace samples using three two-dimensional histograms with data in the CIE L*a*b* color space while additionally integrating chroma (C*) and hue (h°) to develop a new proposal from histograms, employing deep learning for the classification task. The results indicate that utilizing three histograms based on L*, C*, and h° brings an average accuracy of 85.74 ± 2.37 compared to three histograms using L*, a*, and b*, which reported an average accuracy of 82.22 ± 2.84. In conclusion, the new color characterization approach presents a viable solution for classifying common bean landraces of both homogeneous and heterogeneous colors. Full article

We explored anodic aluminum oxide (AAO) stealth materials combining low infrared emissivity and visible structural coloration through multi-parameter modulation. Using DC ion gold sputtering and UHV magnetron chromium sputtering, we successfully prepared an AAO stealth material with high-saturation visible structural coloration and low infrared emissivity (ε < 0.17). Quantitative evaluation based on the CIE Lab color difference model indicated that the gold-coated samples had high matching accuracy with PANTONE standard colors ($\mathsf{\Delta }{E}_{ab}^{*}$ < 1.6). The chromium-coated samples had slightly lower matching accuracy ($\mathsf{\Delta }{E}_{ab}^{*}$ < 3.0), but still displayed rich coloration, with color difference within human-perceptible tolerance limits. Full article

The classification of bean landraces based on their coloration is of particular interest, as the color of these plants is associated with the nutritional components present in their seeds. In this paper, the authors propose a procedure to identify the colors of heterogeneous color bean landraces based on the information from their digital images. The proposed methodology employs a three-dimensional histogram representation of the estimated color, expressed in the CIE L*a*b* color space, with an unsupervised learning method called the Gaussian Mixture Model. This approach facilitates the acquisition of representative information for the colors of a bean landrace, represented as points in the CIE L*a*b* color space. Furthermore, the K-$nn$ method can be trained with these punctual representations to identify colors, yielding satisfactory results on landraces with homogeneous and heterogeneous seeds. Full article

Dominant colors significantly influence visual image perception and are widely used in computer vision and design. Traditional extraction methods often neglect visually salient colors that occupy small areas yet possess high aesthetic relevance. This study introduces a method for detecting both dominant and visually prominent colors in a wide range of hues and images. We analyzed the color gamut of images in the CIE L^*a^*b^* color space and concluded that it is difficult to identify the dominant and prominent colors due to high color variability. To address these challenges, the proposed approach transforms images into the orthogonal ICaS color space, integrating the properties of RGB and CMYK models, followed by K-means clustering. A spectral residual saliency map is applied to exclude background regions and emphasize perceptually significant objects. Experimental evaluation on an image database shows that the proposed method yields color palettes with broader gamut coverage, preserved luminance, and visually balanced combinations. A comparative analysis was conducted using the ΔE₀₀ metric, which accounts not only for differences in lightness, chroma, and hue but also for the perceptual interactions between colors, based on their proximity in the color space. The results confirm that the proposed method exhibits greater color stability and aesthetic coherence than existing approaches. These findings highlight the effectiveness of the orthogonal saliency mean method for delivering a more perceptually accurate and visually consistent representation of the dominant colors in an image. This outcome validates the method’s applicability for image analysis and design. Full article

The colour degradation of murals presents a significant challenge in the conservation of architectural heritage. Previous research has often concentrated on localized pigment changes while paying insufficient attention to the interaction between colour variation and indoor environmental conditions. Although non-destructive analytical techniques are widely used in heritage studies, their integrated application in combination with colourimetry has been limited, particularly in the context of Tibetan Buddhist murals in highland continental climates. This study investigates the murals of Liuli Hall in Meidai Lamasery, Inner Mongolia, as a representative case. We employed a comprehensive methodology that combines non-destructive analytical tools, gas chromatography–mass spectrometry, and quantitative colour analysis to examine pigment composition, binding material, and surface deterioration. Through joint analysis using the CIE Lab and CIE LCh colour space systems, we quantified mural colour changes and explored their correlation with material degradation and environmental exposure. The pigments identified include cinnabar, atacamite, azurite, and chalk, with animal glue and drying oils as binding materials. Colourimetric results revealed pronounced yellowing on the east and west walls, primarily caused by the ageing of organic binders. In contrast, a notable reduction in brightness on the south wall was attributed to dust accumulation. These findings support tailored conservation measures such as regular surface cleaning for the south wall and antioxidant stabilization treatments for the east and west walls. Initial cleaning efforts proved effective. The integrated approach adopted in this study provides a replicable model for mural diagnostics and conservation under complex environmental conditions. Full article

The purpose of this study was to determine the effect of postharvest ripening on the concentration of phenolic compounds and antioxidant activity in fruits of ten plum cultivars. The degree of ripeness was defined as the CIRG index, based on the CIE Lab color values and ranging from 1.05 to 10.04, soluble solids (12.9 to 20.7%), and firmness (4.47 to 13.64 N). Fruits were analyzed directly after harvest and after 3 and 6 days of storage at 18 °C. The CIRG index increased by 2% to 23% after 3 days of storage, and by as much as 64% after 6 days, depending on the cultivar. Ripening resulted in increased concentration of phenolic compounds and in higher antioxidant activity. The predominant compounds in the majority of the cultivars were proanthocyanidins, which constituted over 50% of the total polyphenols, at concentrations between 30 and 453 mg 100 g⁻¹ FW. Additionally, postharvest ripening caused the proanthocyanidins to increase up to 76%. The polymerization of proanthocyanidins ranged from 6.6 to 20.0. For some cultivars, the concentration of anthocyanins approximately doubled after 6 days of fruit storage. Fruits of ‘Čačanska Najbolja’ and ‘Čačanska Lepotica’ were characterized by the highest concentration of bioactive compounds and the highest antioxidant activity. Full article

Food contact polymers require thermochromic pigments to provide temperature-sensitive visual cues for consumer safety and product integrity. However, their susceptibility to ultraviolet (UV) degradation limits long-term application. This study investigates the UV resistance of food-grade thermochromic polypropylene blends under simulated indoor and outdoor UV exposure for 500 and 1000 h. Visual properties, colorimetric (CIE L*a*b*) measurements, mechanical testing (tensile and impact), and mass variation analysis were performed to assess photostability and material integrity. Exposure to UV led to progressive discoloration (ΔE*_ab up to 34.07) and significant mechanical deterioration. Tensile strain at break decreased by 48.67%, and notched impact strength dropped by 44.15% after 1000 h of UV exposure. No measurable mass loss occurred, indicating degradation was confined to surface-level oxidation rather than bulk material erosion or leaching. These findings highlight the need for optimal pigment loading and UV stabilization to extend the shelf life of thermochromic food packaging materials in light-exposed storage and retail environments. The study offers a framework for improving the long-term reliability of smart packaging in the food industry. This work uniquely integrates optical, mechanical, and mass loss analyses to evaluate thermochromic packaging degradation under extended UVA exposure. Full article

Most dyeing occurs when a fabric is in a wet state, while color matching is performed when the fabric is in a dry state. As water is a colorless liquid, it has been difficult to analytically map these two states using existing color theories. Machine learning models provide a heuristic approach to this class of problems. Linear regression, random forest, eXtreme Gradient Boosting (XGBoost), and multiple neural network models were constructed and compared to predict the color of dry cotton fabric from its wet state. Different models were developed based on squeeze pressure (water pickup), with inputs to the models consisting of the L*a*b* (L*: lightness; a*: red–green axis; b*: blue–yellow axis) coordinates in the wet state and the outputs of the models consisting of the predicted L*a*b* coordinates in the dry state. The neural network model performed the best by correctly predicting the final shade to under a 1.0 color difference unit using the International Commission on Illumination (CIE) 2000 color difference formula (CIEDE2000) color difference equation about 63.9% of the time. While slightly less accurate, XGBoost and other tree-based models could be trained in a fraction of the time. Full article

As human labour is limited and therefore expensive, computer vision has emerged as a solution with encouraging results for monitoring and sorting tasks in the agrifood sector, where conventional methods for inspecting fruit browning that are generally subjective, time-consuming, and costly. Thus, this study investigated the application of computer vision techniques and various RGB cameras in the detection and classification of enzymatic browning in cut pears, comparing convolutional neural networks (CNNs) with stochastic modelling. More specifically, light is shed on the potential of CNN-based approaches for high-throughput and easily adapted applications and the potential of stochastic methods for precise, quantitative analyses. In particular, the developed CNN model was easily trained and achieved an accuracy of 96.6% and an F1-score greater than 0.96 during testing with real pear slices. On the other hand, stochastic modelling provided quantitative indices (i.e., the Browning Index (BI) and Yellowing Index (YI)) derived from the CIE Lab* colour model, thus offering accurate monitoring of enzymatic browning and related optical changes but it was less versatile as it required human expertise for implementation and tuning. Using both the BI and YI as input vectors in the NN Bayesian classifier increased the correct classification rate of control samples to 82.85% (4.6% increase) and to 89.81% (15% increase) for treated samples. Finally, a future need for a hybrid approach combining the strengths of both methods was identified, with improved robustness and practicality of image analysis systems in agricultural quality control to enable higher levels of automation in this area. Full article

Objectives: The synergistic effect of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and antimicrobial photodynamic therapy (aPDT) in mandibular molar root canal disinfection remains underexplored, particularly against dual-species biofilms that better simulate clinical conditions. This study evaluates their combined antimicrobial efficacy against Enterococcus faecalis and Candida albicans biofilms and assesses potential tooth discoloration caused by riboflavin and nano-curcumin. Materials and Methods: The mesiobuccal canals of 57 extracted mandibular molars were inoculated with E. faecalis and C. albicans biofilms. The antimicrobial effects were assessed using riboflavin or nano-curcumin with a 450 nm diode laser (BDL), SWEEPS, or their combinations, compared to 5.25% NaOCl (positive control) and saline (negative control). Biofilm reduction was quantified by colony-forming units (CFUs/mL), and discoloration was evaluated using the ΔE metric in the CIE L*a*b* color space. Results: Both microorganisms showed a significant decrease in colony numbers in all experimental groups compared to the negative control (p < 0.001), except for E. faecalis, where no significant difference was observed between the riboflavin/nano-curcumin groups and the negative control. Combining riboflavin or nano-curcumin with SWEEPS or BDL significantly enhanced antimicrobial efficacy compared to individual treatments (p < 0.001). The combined photodynamic therapy and SWEEPS groups showed the lowest colony counts. The ΔE values were, on average, 1.81 for riboflavin and 1.09 for nano-curcumin. Conclusions: The combination of SWEEPS and aPDT effectively reduces E. faecalis and C. albicans biofilms in molars, supporting its potential as an adjunct in endodontic disinfection. Minimal discoloration further highlights its clinical applicability. Full article

Particles from gasoline-powered vehicle combustion often contain dark or black magnetic iron oxides. This work evaluates color variations and heavy metal concentrations in urban dust by separating magnetic particles. We used a high-power magnet to separate the magnetic particles of 30 urban dust samples from the Metropolitan Zone of the Valley of Mexico. In this way, we obtained three types of dust samples: complete particles (CPs), magnetic particles (MPs), and residual particles (RPs). The change in color with the CIE L*a*b* and RGB systems was estimated, while the concentrations of 18 heavy metals with XRF were measured. Results showed significant color differences between magnetic particles (MPs) and complete (CPs) or residual particles (RPs), with MPs exhibiting darker tones and higher concentrations of Cu, Fe, Mn, and V. The redness and saturation indices may help to identify urban dust samples contaminated with heavy metals and magnetic particles. Magnetism is a method that removes magnetic particles and some heavy metals from urban dust, partially reducing its toxicity. Full article