Color distribution of maxillary primary incisors in Korean children

The purpose of this study was to investigate the color distribution of maxillary primary incisors measured with a colorimeter. The subjects were 100 Korean children aged 2–5 with total number of 400 teeth. A spot measurement intraoral colorimeter was used to determine the color of maxillary primary central and lateral incisors at labial central area. The CIE L*, a*, b* value of each tooth and color difference (ΔE) among each other were calculated and analyzed. The range of L*, a*, and b* values, regardless of the type of teeth, was 72.7–84.9, ?0.6 to 4.9, and 4.7–15.0, respectively. Mean value (SD) of L*, a*, and b* for maxillary primary incisors was 78.6 (2.3), 1.2 (0.9), and 9.6 (1.8), respectively. Boys showed more red (higher a* value) and less yellow (lower b* value) hue than girls in the central incisors (P < 0.05). Mean color difference (ΔE) (SD) between two values which selected from overall 400 L*, a*, b* values measured (n = ₄₀₀C₂) was 3.9 (1.8) with 95% confidence interval range of 3.86–3.89, and most of them were found to be present around the previously reported clinical acceptability thresholds (ΔE = 2.7–6.8). Because mean intraperson ΔE (SD) was 3.0 (1.6) with 95% confidence interval range of 2.86–3.12, most colors among primary incisors in the same person were presumably difficult to discern by naked eye (ΔE < 3.7). Age influenced L* and b* values significantly, but the correlation coefficients were not high (r = ?0.182 for L* of central incisors, P < 0.01; r = 0.188 for b* of central incisors, P < 0.01; and r = 0.143 for b* of lateral incisors, P < 0.05). The present study showed somewhat higher color coordinates than the previous reports which based on primary anterior teeth in other ethnic groups. The results of this study could be used for the color modification of esthetic materials for primary teeth. © 2009 Wiley Periodicals, Inc., Col Res Appl, 2010.     

Color of natural tooth crown in Japanese people

The aim of this study was to investigate the color of the natural maxillary incisor tooth from Japanese people of all age groups. These results were compared with the Trubyte Bioblend shade guide. The subjects of this study were in the age range of 13–84, 42 male and 45 female making 87 people in total. Areas with 1.0‐mm diameter at five sites were measured along the tooth axis for L*,a*,b*, according to CIELAB color spaces using a Spectroradiometric Color Computer. At the incisal site, two significant positive correlations were found between age and a* (r = 0.376, p < 0.001), and b* (r = 0.483, p < 0.001). At the center site, a significant negative correlation (r = −0.418, p < 0.001) was found between age and L*, but positive correlation (r = 0.497, p < 0.001) was found between age and b*. At the cervical site, a significant negative correlation (r = −0.326, p < 0.01) was found between age and L*, but positive correlation (r = 0.702, p < 0.001) was found between age and b*. Near the root, particularly, the values of a* were greater than those suggested by the Trubyte Bioblend shade guide. In conclusion, as the Trubyte Bioblend shade guide does not match the natural tooth color in red‐green chromaticity near the root, it is significant for us in dentistry to develop new shade guides that match the Japanese people based on the data collected. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 43–48, 2000     

Comparison of the metrics between the CIELAB and the DIN99 uniform color spaces using dental resin composite material values

The sizes for the perceptible or acceptable color difference measured with instruments vary by factors such as instrument, material, and color‐difference formula. To compensate for disagreement of the CIELAB color difference (ΔE^*_ab) with the human observer, the CIEDE2000 formula was developed. However, since this formula has no uniform color space (UCS), DIN99 UCS may be an alternative UCS at present. The purpose of this study was to determine the correlation between the CIELAB UCS and DIN99 UCS using dental resin composites. Changes and correlations in color coordinates (CIE L*,a*, and b* versus L₉₉, a₉₉, and b₉₉ from DIN99) and color differences (ΔE^*_ab and ΔE₉₉) of dental resin composites after polymerization and thermocycling were determined. After transformation into DIN99 formula, the a value (red–green parameter) shifted to higher values, and the span of distribution was maintained after transformation. However, the span of distribution of b values (yellow–blue parameter) was reduced. Although color differences with the two formulas were correlated after polymerization and thermocycling (r = 0.77 and 0.68, respectively), the color coordinates and color differences with DIN99 were significantly different from those with CIELAB. New UCS (DIN99) was different from the present CIELAB UCS with respect to color coordinates (a and b) and color difference. Adaptation of a more observer‐response relevant uniform color space should be considered after visual confirmation with dental esthetic materials. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 168–173, 2006     

Effect of orange fiber addition on yogurt color during fermentation and cold storage

Orange fiber obtained from orange juice by‐products was added to yogurt. Fiber (0%, 0.6%, 0.8%, and 1% doses and different fiber size: 0.417–0.701 and 0.701–0.991 mm) effects on color during yogurt fermentation and cold storage were studied. Overall composition, pH, acidity, syneresis, L*, a*, and b* values were determined. Sensory evaluation of yogurts was carried out. Fiber addition did not cause changes in yogurt acidification and color during fermentation process, though decreased L* value and increased b* value of the milk. Color evaluation along fermentation is pH dependent (R > 0.870). pH decreased and syneresis increased along cold storage. Because of the acidification process, L* value decreased and a* and b* values increased in all yogurts. Yogurts with 1% fiber were significantly different from the others along cold storage, presenting lower L*, higher a* and b* values, and lower syneresis. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 457–463, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20158     

Three‐dimensional color prediction modeling of single‐ and double‐layered woven fabrics

In this research, the three‐dimensional structural and colorimetric modeling of three‐dimensional woven fabrics was conducted for accurate color predictions. One‐hundred forty single‐ and double‐layered woven samples in a wide range of colors were produced. With the consideration of their three‐dimensional structural parameters, three‐dimensional color prediction models, K/S‐, R‐, and L*a*b*‐based models, were developed through the optimization of previous two‐dimensional models which have been reported to be the three most accurate models for single‐layered woven structures. The accuracy of the new three‐dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔE_CMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two‐dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔE_CMC(2:1) from 10.30 to 5.25 units on average after the three‐dimensional modeling.     

Effects of cold plasma on the color parameters of Hyssop (Hyssopus officinalis L.) using color imaging instrumentation and spectrophotometer

This research was conducted to evaluate the effects of cold atmospheric plasma treatment on the color of Hyssop (Hyssopus officinalis L.) and also to compare the usage of the spectrophotometer vs the color imaging instrumentation for the evaluation of the treatment on the color parameters. The experiments were investigated at different treatment times of 1, 5, and 10 minutes and the voltage values of 17, 20, and 23 kV. Possible changes of color were evaluated by using CIE L*a*b* values obtained with HunterLab colorimeter and CIE L*a*b* values obtained with a digital still camera (DSC) using digital image processing (MATLAB software). The values of L*, a*, and b* of the samples were obtained using both the methods. The results revealed that the L*, a*, and b* values of the treated Hyssop samples changed with increasing the treatment time and the voltage applied. Evaluating the interaction effects revealed that there was a significant difference in the (−a^*/b^* ) ratio. In addition, the results showed that the effects of all variables on the color parameters were significantly different in the case of the DSC using digital image processing. However, these effects were not significantly different using HunterLab colorimeter except for time variable and interaction effects of a* and (−a^*/b^* ) ratio. The lightest green color and the maximum chlorophyll content loss were observed for 23 kV applied over 10 minutes. Based on the results, the digital image processing can be used as a practical tool to study the variations at the color of dried Hyssop leaves after cold plasma treatment.     

Use of microemulsions for removal of color and dyes from textile wastewater

One of the major environmental problems in the textile dyeing industry is the removal of color from effluents. The present study deals with color removal from effluents using microemulsions. The wastewater used in this study was the reactive exhausted dye liquor from a dyeing house containing Procion Yellow H‐E4R (CI Reactive Yellow 84), Procion Blue H‐ERD (CI Reactive Blue 160) and Procion Red H‐E3B (CI Reactive Red 120). Color removal was determined by CIE L*a*b* (CIELAB) color space, CIE L*a*b* color difference, ΔE*_ab, and absorbance. Color removal greater than 95% was achieved, attaining values lower than the consent requirements established by the Environmental Agency. It was observed that pH is an important parameter in color removal and effluent pH correction from 10.44 to 9 before extraction improved results. The results obtained were modeled using the Scheffé net method and evaluated through the construction of isoresponse diagrams by correlation graphics between experimental values and those obtained through use of model equations, providing an experimental error of less than 2%. The optimized method very efficiently removed all dyes contained in the effluent. The same microemulsion phase recovered after the extraction process can be used at least a further 14 times and all the extractions gave good color removal. Copyright © 2004 Society of Chemical Industry     

Effect of microwave pretreatment on the color degradation kinetics in mustard greens (Brassica juncea)

In the present work, the impact of microwave pretreatment on the thermal degradation of color (chlorophylls) in mustard greens was studied. The drying experiments were conducted in the range of temperatures from 50 to 80°C. The degradation in the levels of chlorophylls has been quantified using Hunter color values (L*, a*, and b*) and calculating total color difference (ΔE). From the color results, the changes in color values (L*, a*, and b*) were observed as inappreciable, and changes in ΔE were found to be increased during drying. Analysis of kinetic data displayed a first-order reaction kinetics for chlorophyll degradation. Arrhenius equation was used to calculate the activation energies for rate constants, and it has been varied from 13.3 to 27.4?kJ/mol. Thermodynamic parameters, enthalpy of activation (ΔH^#), and entropy activation (ΔS^#) were found to be in the range of 1.40–2.63?J/mol and ?293 to ?305?J/mol?·?K, respectively. The data from the present work revealed that the microwave pretreatment of mustard greens remarkably influenced the retention of chlorophylls in the final dehydrated powder.     

Optimization of color design for military camouflage in CIELAB color space

The assessment of military camouflage is a key consideration in the modern military field. Traditionally, the assessment relies on traditional human visual detection tests because a large scale multi‐level and multi‐factor experiments are time‐ and resource‐consuming. One aspect of camouflage assessment, to which this current study pertains, entails improving upon or “enhancing” an existing or “selected” design. The current study presents a new and practical approach for enhancing the selected military camouflage by utilizing response surface methodology (RSM) of %L*, %a*, and %b* in CIELAB color space. Ten participants were recruited to evaluate 35 variations of %L*, %a*, and %b* on camouflage similarity index (CSI) and reaction time (RT). Based on RSM, the optimum combination occurs at L*: 61.4966, a*: ?5.6505, and b*: 10.5114. In addition, a predictive algorithm to calculate the optimum shift of %L*, %a*, and %b* from the original camouflage to the improved camouflage derived from RSM is also proposed. The optimum shift occurs at ?25%L*, ?55%a*, and + 80%b*. In the end, a new design guideline is proposed for the enhancement of selected military camouflage, which adopts the present study's research findings.     

Effect of mincing degree on colour properties in pork meat

Although the colour of different meat products has been studied, particularly in the final product , these studies do not separate the influence of degree of mincing from other factors such as additives, spices, manufacturing process, etc. The effect of degree of mincing on colour (CIELAB colour space) in pork meat was studied. Three mincing processes were studied, two using a grinder with 10 and 20 mm diameter holes in the plate, and a third in which a cutter was used to obtain a finely minced product. As control, intact meat was used. Colour parameters [lightness (L*), redness (a*), yellowness (b*), chroma (C*), hue (H*), a*/b* ratio, and colour differences], pH, and water holding capacity were determined. Mincing, regardless of the type used, increased the values of L*, b*, and H*, but decreased the values of a* and a*/b* ratio. The L* values increased with mincing degree. The H* values and a*/b* ratio of plate minced meats (10 and 20 mm) differed from that which had been finely minced. The mincing process did not modify the saturation values of the batters. Only the fine mincing process modified (increased) the water holding capacity of the batters. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 376–380, 2000     

A fallacy in the definition of ΔH*

When a color differs from the reference, it is desirable to ascribe the difference to differences in the perceptual attributes of hue, chroma, and/or lightness through psychometric correlates of these attributes. To this end, the CIE has recommended the quantity ΔH* as a psychometric correlate of hue as defined by ΔH* = [(ΔE*)² - (ΔL*)² - (ΔC*)²]^1/2, where the correlates correspond to either the 1976 CIELAB or CIELUV color spaces. Since ΔH* is defined as a “leftover,” this definition is valid only to the extent that ΔE* comprises exclusively ΔL*, ΔC*, and ΔH* and that ΔL*, ΔC*, and ΔH* are mutually independent compositionally, both psychophysically and psychometrically. It will be shown that as now defined ΔH* lacks psychometric independence of chroma and always leads to incorrect hue difference determination. Such a deficiency causes problems, especially in the halftone color printing industry, since it can suggest an incorrect adjustment for the hue of the inks. A revised definition herein of ΔH* provides a psychometric hue difference independent of chroma, valid for large and small psychometric color differences regardless of chroma. However, for small chromas, the seldom used metric ΔC might be a better color difference metric than ΔH* because complex appearance effects make the perceptual discrimination of lightness, chroma, and hue components more difficult than for high chromas.     

3D Master Toothguide according to L*, C*, and h* coordinates

The purposes of this study are to describe the color coordinates of the 26 shade tabs of the 3D Master Toothguide according to their L*, C*, h* coordinates, and to calculate ΔE_ab*, ΔL*, ΔC*, and Δh* in the 26 shade tabs. The tooth color of 1361 maxillary central incisors was measured “in vivo” using a spectrophotometer. Tooth color was recorded following the 3D Master system and its corresponding L*, C*, h*color coordinates. Of the 325 shade tabs pairs compared a color difference ( ) of between 2.6 and 5.5 units was found in 9.54% (31 pairs). In 291 pairs (89.54%) there was color difference that exceeded the 5.5 units. Only 0.92% of the color differences () were less than 2.6 units. The minimum color difference ( ) found was 2.1 units and the maximum 45.0 units. The intervals in lightness, chroma, and hue groups between adjacent shade tabs were not uniform. In conclusion, this toothguide is clearly ordered regarding lightness or the L* coordinate. Most of the color differences between the 26 shade tabs of the 3D Master exceed the perceptible threshold of 2.6 units. Some clinical implications are as follows: the 26 shade tabs of the 3D Master Toothguide offer improvements as far as spatial arrangement is concerned. Thus, it is highly possible that the subjective visual color of the measurement would be correct. If there is a mistake when choosing the shade tab from the 3D Master guide there will quite probably be an unacceptable color difference from the clinical point of view. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 518–524, 2015.     

Three-month evaluation of a low concentration (6% hydrogen peroxide) experimental bleaching gel containing Tio2 and chitosan: An in vitro study

The study aimed to compare the effectiveness of an experimental gel that contained 6% hydrogen peroxide, titanium dioxide (TiO₂), and chitosan nanoparticles with that of the two bleaching agents that are routinely used and evaluate their effectiveness in a 3-month period. Seventy-two extracted premolar teeth were divided into three groups for the bleaching procedure. TiO₂ and chitosan were added to increase the whitening effect of the low-concentration experimental gel. In group 1, the experimental gel was applied and activated with a D-Light Duo LED device. In group 2, Opalescence Boost PF was applied chemically. In group 3, Philips Zoom was applied and activated with Zoom Advanced Power. The color of the teeth was measured with a Vita Easyshade Advance 4.0 spectrophotometer before the bleaching and 24 hours, 7 days, 14 days, 30 days, and 3 months after final bleaching. The CIEDE2000 color differences (∆E₀₀) and average L*, a*, and b* values were calculated. Effective bleaching was observed in three groups as determined by the initial color at different measurement times (P < .05). Philips Zoom showed a higher value of color change than the other groups at all times. The experimental gel showed a bleaching activity like that of Opalescence Boost PF at all-time measurements. A slight decrease in color change was observed between the first-month measurement and third-month measurement in all groups. A low-concentration experimental gel containing TiO₂ and chitosan provided effective whitening, and the whitened color persisted throughout the 3-month period.     

Improving the compatibility of disperse dye mixtures using levelling agent — assessment through colour coordinates

The addition of a nonionic levelling agent to a dyebath containing a mixture of three disperse dyes in equal proportions and having similar hues (all in the red—yellow sector of colour space) significantly improved their compatibility, especially at higher applied depths of 3.0% and 4.5%. The dyed samples were measured for the differences in their colour coordinates with respect to the undyed substrate on a spectrophotometer attached to an IBM personal computer. The plots of ΔL* vs ΔC*_ab, ΔL* vs K/S, Δb* vs Δa*, Δa* vs K/S and Δ6* vs K/S clearly indicated the improvement in compatibility of the dye mixture.     

Image quality evaluation for high dynamic range and wide color gamut applications using visual spatial processing of color differences

High dynamic range (HDR) and wide color gamut imagery has an established video ecosystem, spanning image capture to encoding and display. This drives the need for evaluating how image quality is affected by the multitudes of ecosystem parameters. The simplest quality metrics evaluate color differences on a pixel‐by‐pixel basis. In this article, we evaluate a series of these color difference metrics on four HDR and three standard dynamic range publicly available distortion databases consisting of natural images and subjective scores. We compare the performance of the well‐established CIE L*a*b* metrics (ΔE₀₀ , ΔE₉₄ ) alongside two HDR‐specific metrics (ΔE_Z [J_za_zb_z], ΔE_ITP [IC_TC_P]) and a spatial CIE L*a*b* extension (). We also present a novel spatial extension to ΔE_ITP derived by optimizing the opponent color contrast sensitivity functions. We observe that this advanced metric, , outperforms the other color difference metrics, and we quantify the improved performance with the steps of metric advancement.     

Wood photography using light irradiation and heat treatment

To apply the coloring method using light irradiation and thermal treatment to print photographs on wood, the effect of the transmittance of negative films was investigated. ΔE* decreased with light irradiation when specimens covered with films with transmittances exceeding 20% were irradiated for 100 h. It was thought that this phenomenon was due to the decrease in Δb*. The color of light‐irradiated wood changed remarkably with thermal treatment; however, the change in the color of exposed specimens covered with films with transmittances exceeding roughly 20% became constant. Clear photographs could be printed on wood using negative films with transmittances less than approximately 20%. Furthermore, the difference between the maximum and minimum values of ΔE* after thermal treatment was about 22. Humans can distinguish four to seven colors that can be created by this method. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 312–316, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20027     

Do repeated firings affect the color properties of porcelain‐fused‐metal restorations that are fabricated differently?

Repeated firings can affect the quality of the porcelain color. The purpose of this study is to evaluate the effect of repeated firings on the color changes of porcelain‐fused‐metal restorations that are manufactured using different methods. A total of 60 cylindrical shaped cobalt–chromium alloys (Ø = 10 mm and h = 1.5 mm) were fabricated using casting (C), milling (M), direct metal laser sintering with and without annealing (EL+, EL‐), and selective laser melting with and without annealing (CL+, CL‐). The samples were veneered with A2 (as indicated by the Vita Shade Guide) dentin porcelain of 2 mm thickness. Then the samples subjected to the repeated firings (2nd, 4th, 6th, 8th, and 10th), and the color of each sample was recorded using a spectrophotometer. The CIEDE2000 (ΔE₀₀) formula was used to calculate color differences of the samples on repeated firings. Repeated measures analysis of variance (ANOVA ) and post‐hoc Tukey's test were utilized to analyze the results (a = 05). The L*, a*, and b* values of porcelain‐fused‐metal specimens were significantly affected by the number of firings (P < 0.001) and fabrication techniques (P < 0.001). The ΔE₀₀ values for C, M, CL‐, and EL‐ groups after 10th firing were above 0.8 unit, which indicates that visually perceivable color differences are clinically acceptable. On the other hand, the ΔE₀₀ values for CL+ and EL+ groups were above the PT value after 8th repeated firings. The color properties of porcelain‐fused‐metal restorations were affected by the fabrication techniques and the number of firings.     

Effect of tertiary amines on yellowing of UV‐curable epoxide resins

The work reported demonstrates that the yellowness of UV‐curable epoxide resins can be improved by adding certain tertiary amines in appropriately determined amounts. According to the results of our experiments, 2.0 wt% benzoyl peroxide added to a resin effectively enhances the crosslinking density, and phenolic free radicals are produced during UV curing, which consequently induce yellowness via the reaction of oxygen and the free radicals. Imidazole (1‐amine) and tertiary amines, including 1,2‐dimethylimidazole (2‐amine), 2,4,6‐tris(dimethylaminomethyl)phenol (3‐amine), 1‐methylimidazole (4‐amine) and 2‐methylimidazole (5‐amine), were chosen to be added to resins, and their effects on UV conversion and yellowness were investigated. According to the experimental results, tertiary amines in the resin can provide a certain degree of improvement in yellowness index (ΔYI) and color parameter (ΔE*_ab) of the resin sample. Whatever the type of tertiary amine, it is found that the optimum content of amine in resin is 1.0 wt%. Also, among the studied amines, the 3‐amine exhibits the highest UV reactivity and the best efficiency for yellowness improvement with values of Δa*, Δb*, ΔYI and ΔE*_ab as low as ? 1.4, 6.23, 11.27 and 6.48, respectively. Copyright © 2007 Society of Chemical Industry     

Mössbauer spectroscopic and chromaticity analysis on colorative mechanism of celadon glaze

The dependence of the color of a celadon glaze on the chemical composition and the electronic state of Fe was investigated by Mössbauer spectroscopic and chromaticity analysis. The amount of Fe₂O₃ was found to be the main factor influencing L* and b* values, whereas the amount of TiO₂ was found to affect all the parameters (L*, a*, b*). The effect of MnO on the color was significant only by interaction terms. The amount of P₂O₅ was found to be the main factor of the b* value. According to the Mössbauer analysis results, as the amount of divalent iron ions increases, the a* and b* values decreased; on the other hand, the L* value increased. As the amount of titanium increased, Fe²⁺ was found to be destabilized relative to Fe³⁺ due to the structural instability of Fe-O-Ti network.     

Surface properties of tannin-impregnated and varnished beech wood after exposure to accelerated weathering

The aim of this study was to determine selected surface properties of varnished beech wood impregnated with natural extracts after exposure to accelerated weathering. Beech wood samples were impregnated with aqueous solutions of 5 and 10% mimosa (Acacia mollissima) and quebracho (Shinopsis lorentzii) tannins. After weathering, colour changes (ΔL*, Δa*, Δb*, and ΔE*) in addition to scratch resistance and surface hardness values were calculated and evaluated. As a result of the weathering process, greater colour changes (ΔE*) were detected in the beech wood samples impregnated with tannins compared with the unimpregnated control samples. The least colour change occurred in the Tanalith-E-impregnated samples. Total colour change was adversely affected with tannin impregnation after the weathering processes. In terms of surface hardness and scratch resistance, the highest values were observed in the mimosa-solution-impregnated and control samples. Furthermore, it was found that scratch resistance and hardness values tended to increase during the first period of weathering and decreased thereafter. Regarding surface properties, the best results were obtained when polyurethane varnish was employed compared with the other varnish types.