CIEDE2000 Color Difference Formula Research Articles

Instrumental and Visual Evaluation of the Chameleon Effect of Single-shaded Composite Resins.

To evaluate the shade-matching ability of single-shade resin-based composite restorations in different thicknesses using both instrumental and visual techniques. Cavities with 4 mm diameter and 2 mm (n=96) or 3 mm (n=96) depth were prepared in acrylic incisor teeth of shades A2, A3, B3, and C2 and restored with three single-shade resin composites, Omnichroma (Tokuyama Dental America, Encinitas, CA, USA [OM]), Vittra APS Unique (FGM Dental Group, Joinville, SC, Brazil [VU]), Zenchroma (President Dental, Allershausen, Germany [ZC]), and a microhybrid resin composite (Filtek 3M Z250 3M ESPE, St Paul, MN, USA [FZ]) of A2, A3, B3, and C2 shades. Readings were obtained using VITA Easyshade V spectrophotometer for the teeth and restorations. The CIEDE2000 (ΔE00) color difference formula was used, and the values were assessed using three-way analysis of variance (ANOVA). Forty-eight evaluators graded the shade match of 32 different specimens visually as (A) best shade match, (B) intermediate shade match, and (C) poor shade match. FZ material achieved satisfactory matches for both thicknesses, across all shades, and OM material demonstrated statistically significant lower shade matches than the ZC and the FZ materials (p<0.05). VU exhibited poor shade match with the highest ΔE00 value on C2 shade. According to the visual examination, the best shade matches were observed for FZ on A3-shade and ZC on C2-shade teeth. Shade matching for 2 mm and 3 mm-thick composite resin restorations is material- and tooth-shade dependent.

A superpixel‐based color difference detection algorithm for dyed fabrics

AbstractIn order to enhance the accuracy and efficiency of color difference detection for dyed fabrics, this article introduces a novel superpixel‐based color difference detection algorithm, which exhibits three significant improvements over the previous algorithm. First, it proposes a more rational color feature extraction method to extract more detailed color features from fabric images, which uses superpixels as basic units for both color feature extraction and color difference detection. Second, the algorithm employs the CIEDE2000 color difference formula to calculate color difference values. This eliminates the need for obtaining standard fabric images as references in advance, making the process more convenient and practical. Finally, an area‐based color difference calculation method is proposed based on the human visual mechanism, ensuring that the evaluation results are more consistent with human eye observations. Experimental results demonstrate that the proposed algorithm provides more accurate and visually consistent color difference assessments compared to the previous algorithm.

The Effect of Aging on Artificial Saliva at Different pH Values on the Color Stability of New Generation Denture Base Materials.

New-generation denture base materials are used successfully in denture fabrication; however, the effect of saliva pH change on the color stability of materials is unknown. The purpose of this in vitro study is to evaluate the color stability of new-generation denture base materials after immersion in artificial saliva with different pH values (3,7,14). Disc-shaped samples (Ø 10 mm x 2 mm) were prepared from three different denture base materials (1 pre-polymerized polymethylmethacrylate [PMMA], 1 graphene-reinforced PMMA, and heat-cure polymethyl methacrylate resin) (n=10). After polishing, color coordinates were measured using a PCE-CSM 5 colorimeter programmed in the CIE system (L* a* b*). The samples were kept in artificial saliva at different pH values and 37°C for 21 days. At the end of 21 days, color coordinates were measured again. The suitability of the measurements for a normal distribution was examined with the Kolmogro-Smirnov test. Whether color measurements obtained at different pH levels differed according to groups was examined with the Kruskal-Wallis test. The correlation between the CIEDE2000 and CIELab color difference formulas was examined by correlation analysis. The highest color difference occurred in heat-cure samples at pH 3 (p<0.001). The color difference at different pH values was least observed in pre-polymerized PMMA samples. Significant color differences occurred in the graphene-reinforced pre-polymerized PMMA group at pH 7 (p<0.001). It was observed that color differences occurred in all groups. Dentures made of new-generation CAD/CAM PMMA, which are less exposed to color differences, can be recommended for elderly patients with systemic diseases who are frequently exposed to pH changes in the oral cavity. Color differences on denture surfaces over time negatively affect aesthetics. Since pH changes cause changes on the prosthesis surface, it may be recommended for these patients to fabricate dentures from new-generation CAD/CAM PMMA resins, which are less deformable.

Harmonizing color measurements in dentistry using translucent tooth-colored materials

BackgroundSince color measurements are relative, the discrepancy among different instruments is alarmingly high. This multicenter study evaluated the effectiveness of instrument calibration and inter-instrument harmonization of different spectrophotometers with the same optical geometry using tooth-colored, translucent dental materials.MethodsThe coordinating center (CC) spectrophotometer was calibrated using the NPL Ceram Series II set. Two sets of 10 specimens, labeled 1 to 10 and I to X (10 mm in diameter and 1 mm thick), were tested at CC and three research sites (RS1, RS2, and RS3) using the same d/8° optical geometry spectrophotometers. Calibration factors were calculated for each material and site to obtain the average calibration factors for sets 1–10, set I-X, and the combination of both. The differences among the non-corrected and corrected reflection values were calculated using CIEDE2000 (DeltaE00) and CIELAB (DeltaEab) color difference formulas and were submitted to ANOVA and Tukey test (α = 0.05).ResultsA significant decrease of color differences between non-corrected as compared to corrected measurements was recorded for all CC-RS and RS-RS comparisons. The reduction of DeltaE00 values between non-corrected and corrected for CC-RS1, CC-RS2, and CC-RS3 were 83.1%, 77.2%, and 73.6%, respectively. The corresponding DeltaE00 values for RS1-RS2, RS1-RS3, and RS2-RS3 comparisons, indirectly compared in the experiment, were 84.2%, 82.8%, and 68.5%, respectively. There was a significant reduction of DeltaE00 and DeltaEab color difference for all combined RS pairs and each of three RS pairs, corrected with one of two specimen sets calibration factors separately.ConclusionsCalibration and harmonization of color measurements in dentistry using tooth-colored, translucent restorative materials significantly decreased measurement discrepancies between the coordinating center and research sites and among pairs of research sites.

Influence of Composition and Thickness on The Color and Translucency of Glass-Ceramic Materials for Laminate Veneer Restorations: An In Vitro study

Statement of the problem: Numerous glass-ceramic materials are commercially available, yet achieving optimal esthetic results relies significantly on material composition and thickness. The selection of suitable material and thickness poses an ongoing challenge in clinical practice. Objective: This study aimed to investigate the effect of the composition and thickness of different glass-ceramic materials on the Commission Internationale de l'éclairage (CIE) L*, a*, and b* color coordinates and the translucency parameter (TP00). Materials &amp; Methods: Glass-ceramic blocks of A2 shade, with low translucency, encompassing feldspathic (FS), leucite-reinforced feldspathic (LR), and lithium-disilicate (LD) compositions, were sectioned into three thicknesses: 0.5 mm, 0.7 mm, and 1 mm (n=10). All specimens were polished with ceramic polishing rubbers. Using a spectrophotometer, the CIE L*, a*, and b* color coordinates of the specimens were measured over gray, white, and black backgrounds. The TP00 was calculated using the CIEDE2000 color difference formula. The CIE L*, a*, b*, and TP00 were analyzed using two-way ANOVA and Tukey HSD post-hoc tests (α=0.05). Results: Material, thickness, and their interaction significantly influenced the CIE L*, a*, b*, and TP00 values (P&lt;0.001). The LR group displayed the highest L* and a* values, while the LD group showed the lowest (P&lt;0.001). Conversely, the LD group exhibited the highest b* value (P&lt;0.001). Lightness was lowest in 0.5 mm-thick specimens (P&lt;0.001) and similar for 0.7 mm-thick and 1.0 mm-thick specimens (P&gt;0.05). Redness and yellowness increased with increasing thickness (P&lt;0.001). Regardless of thickness, the FS group had the highest TP00 (16.32±1.54), while the LR group had the lowest TP00 (14.31±1.67). Regardless of material, 0.5 mm-thick specimens demonstrated significantly higher TP00 (17.49±1.10) than 0.7 mm-thick (15.45±0.83) and 1.0 mm-thick (13.11±1.12) specimens. There was no significant difference between the 0.5 mm-thick FS and LD groups (P&gt;0.05) and 1.0 mm-thick LR and LD groups (P&gt;0.05). Conclusions: Even when sharing the same shade, glass ceramics may exhibit varying color and translucency properties due to their distinct chemical compositions and thicknesses.

A Study on DNN-Based Practical Model for Predicting Spot Color

The color of product packaging plays an important role in brand awareness and consistency. Given the importance of consistent color reproduction, the use of standardized spot colors is essential. However, the reproduction of specific spot colors in offset packaging printing involves additional processes and costs. This study presents an efficient approach to predict the color result of spot color inks in the packaging printing industry, using only the amount of ink involved in the mixing process as an input. Using a neural network-based model, our approach uses the CIEDE2000 color difference formula as a loss function to accurately estimate the final color. This method provides a simplified alternative to traditional color mixing techniques, which often involve subjective judgment and can be resource-intensive. Particularly beneficial for smaller companies, our approach reduces the complexity and cost associated with achieving accurate spot colors. The significance of this work lies in its practical application, providing a simpler, more objective and cost-effective solution for consistent color reproduction in packaging printing.

Research on fabric image registration and color difference detection based on cyclic elements

In order to realize online color difference detection of printed fabrics, a color difference detection method of printed fabrics based on image segmentation and image registration was proposed to detect the color difference of simple printed fabrics. The acquired standard fabric images are segmented using the combination of a Canny edge detector and uniform grid partitioning. The color information of each sub image is extracted based on the segmentation results and saved. We use the speeded-up robust features algorithm that incorporates the position information of the cyclic element where the feature points are located. The segmentation path of the standard image is registered onto the fabric image to be detected. The color information of each sub image of the image to be detected is extracted according to the registered segmentation path. The color difference value between the sub image of the image to be detected and the sub image of the standard sample is calculated using the CIEDE2000 color difference formula. The experimental results show that when fabric images with duplicate patterns are registered, the image registration methods mentioned in this paper significantly improve the accuracy of registration. The accuracy of the detection method in this paper on the printed fabric dataset can reach 95% compared to the manual calibration results.

The impact of remineralization agents on dental bleaching efficacy and mineral loss in bleached enamel.

This study evaluated the effect of remineralization agents on bleaching efficiency, enamel mineral changes, and post-bleaching color stability. A total of 112 enamel-dentin blocks were prepared from bovine teeth. Following initial color measurements, separate treatment regimens were carried out as follows: negative control (no treatment); positive control (bleaching only); bleaching, then NaF; bleaching + NaF (mix); bleaching, then CPP-ACPF; bleaching + CPP-ACPF (mix); bleaching, then nHAP+F; bleaching + nHAP+F (mix). Color measurements were repeated after immersion in distilled water for 7 days, and again after staining with coffee solution for 14 days. The CIELAB-based whiteness index was used to evaluate bleaching efficiency, and the CIEDE2000 color difference formula for color stability. Chemical investigation was performed using scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction analyses. The experimental groups showed significant increases in whiteness compared to the negative control, and the staining after bleaching did not result in statistically significant differences between the groups. Energy dispersive spectroscopic analysis revealed that bleaching protocols had no impact on elemental levels as well as the ratio of Ca/P. The combined use of bleaching agents with remineralization agents did not affect bleaching effectiveness but also did not provide an additional contribution.

Color Change Evaluation of Three Universal Resin Composites after Storage in Water: An In Vitro Study

Aim: The aim of this in vitro study was to evaluate the color changes of three different universal resin composites after immersion in distilled water for one month. Materials and Methods: Omnichroma, Estelite Σ Quick, and Filtek Universal Restorative were investigated. Ten disk shaped specimens (6 mm diameter, 2 mm thickness) were prepared according to the manufacturers’ instructions for each material. After polishing, initial color measurements were taken followed by individual storage of the specimens in distilled water at 37 °C for one month when color measurements were repeated. The change in the color of each resin composites (Δ E00) was calculated with a digital method, using the CIEDE2000 color difference formula. The data were analyzed using one-way ANOVA followed by Tukey post-hoc test ( P &lt; .05). Results: All resin composites exhibited acceptable color change after one month. Omnichroma exhibited the highest color change (2.26 ± 0.48) value while Filtek Universal Restorative showed the lowest (1.14 ± 0.38) value. All color parameters influenced the Δ E00 values in all groups except Filtek Universal for Δ L* and Δ b values. Conclusion: When performing composite resin restorations, especially for esthetic purposes, polymerization may lead to change in the color of restorative material over time, but it should be considered whether this is within acceptable limits.

Optimizing Parametric Factors in CIELAB and CIEDE2000 Color-Difference Formulas for 3D-Printed Spherical Objects.

The current color-difference formulas were developed based on 2D samples and there is no standard guidance for the color-difference evaluation of 3D objects. The aim of this study was to test and optimize the CIELAB and CIEDE2000 color-difference formulas by using 42 pairs of 3D-printed spherical samples in Experiment I and 40 sample pairs in Experiment II. Fifteen human observers with normal color vision were invited to attend the visual experiments under simulated D65 illumination and assess the color differences of the 82 pairs of 3D spherical samples using the gray-scale method. The performances of the CIELAB and CIEDE2000 formulas were quantified by the STRESS index and F-test with respect to the collected visual results and three different optimization methods were performed on the original color-difference formulas by using the data from the 42 sample pairs in Experiment I. It was found that the optimum parametric factors for CIELAB were = 1.4 and = 1.9, whereas for CIEDE2000, = 1.5. The visual data of the 40 sample pairs in Experiment II were used to test the performance of the optimized formulas and the STRESS values obtained for CIELAB/CIEDE2000 were 32.8/32.9 for the original formulas and 25.3/25.4 for the optimized formulas. The F-test results indicated that a significant improvement was achieved using the proposed optimization of the parametric factors applied to both color-difference formulas for 3D-printed spherical samples.

Does Backgrounds Color Influence the Appearance of Gingiva-Colored Resin-Based Composites?

Dental materials are mainly tested in vitro, so laboratory conditions must reproduce the oral environment to ensure the validity of their results. This study aimed to evaluate the influence of backgrounds on the color of gingiva-colored resin-based composites (GCRBC). Three discs of each of 20 shades of GCRBCs and each thickness (1 and 2 mm) were prepared. Diffuse reflectance was measured on-air and over three natural teeth (0M3/B1, 3M3/B3, and 5M3/B4 shades of Vita 3D Master/Vita Classical guides, respectively) using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry. CIEDE2000 color difference formula and its 50:50% perceptibility and acceptability thresholds have been used to calculate and interpret the results. It can be stated that the background influences the color of all GCRBCs tested, although the effect is more pronounced for 1 mm thick samples. L*, a* and b* coordinates values of GCRBCs on air were significantly different from those obtained on natural teeth backgrounds, and the total color differences were greater than the acceptability thresholds. Since GCRBCs are placed on a dental substrate in clinical conditions, it is not advisable to perform color measurements of GCRBCs on-air because of the high color differences found. This recommendation is especially relevant for thin specimens.

Color and translucency of enamel in vital maxillary central incisors

Statement of problemLimited data, especially in vivo data, exist regarding translucency parameter (TP) values for vital anterior nonrestored dentition. Additionally, published information on the CIELab values of vital enamel at a theoretical infinite thickness is lacking. Obtaining TP and CIELab values in a population that varies in terms of ethnicity, age, and sex would be useful to inform the development and placement of esthetic dental restorations that more accurately capture the complex optical qualities of enamel. PurposeThe purpose of this clinical study was to investigate in vivo the TP and CIELab values of vital anterior incisor enamel at a theoretical infinite thickness in a diverse pool of participants who varied in age, ethnicity, and sex. Material and methodsSpectral reflectance measurements (380 to 780 nm at 2-nm intervals) of the mid-incisal region of vital, unrestored maxillary anterior teeth were made in 120 participants, equally divided into 2 sexes, 4 racial or ethnic groups, and 5 age ranges. Instruments were oriented to achieve 0-degree observation and 45-degree illumination, and spectral measurements were made with white and black silicone backgrounds. Reflectance spectra of the incisal enamel from both the black and white silicone backing were used to fit to the Kubelka-Munk (K-M) reflectance theory. The CIEDE2000 color difference formula was used to determine TP, and data were compared among participant demographics. CIELab color coordinate values for enamel at an infinite thickness were calculated by using a D65 illumination and CIE standard human (2-degree) observer. To determine value ranges and significant differences among participant groups, CIELab values were analyzed with a 4-way ANOVA, and TP values were analyzed with a generalized linear mixed model. Pairwise comparisons of interest were evaluated with Bonferroni-corrected Student t tests. ResultsFor maxillary central incisor enamel, the average TP was 10.1 ±3.6, and the average CIELab color coordinates were L∗=73.5 ±7.6, a∗=2.2 ±1.8, b∗=11.9 ±8.4. TP values of incisal enamel significantly differed among specific age and ethnic groups, with general significant interactions of age and sex (P=.009), as well as ethnicity and age (P=.042). CIE color coordinates of enamel at an infinite thickness were found in the L∗ coordinate among different age groups with the same sex and ethnicity, specifically when comparing CIELab direction with the population characteristics of age (P=.011) and the interaction between age, sex, and ethnicity (P=.035). ConclusionsIn vivo L∗ values and TP values of incisal enamel differed significantly among groups determined by ethnicity, age, and sex.

Comparison of visual shade matching and photographic shade analysis.

To compare the performance of a standardized photographic shade analysis (PSA) and visual shade matching (VSM) using two color difference formulas. Fifty observers (35 undergraduate and 15 graduate students) evaluated the color of two upper left central incisors (LT-light tooth, and DT-dark tooth). VSM was performed using the VITA 3D Master (3D) shade guide in a controlled clinical environment. For PSA, a cross-polarized filter and a gray card (Whibal) were used to standardize the photographs taken (target teeth and shade tabs from 3D). From the pictures obtained, the CIELAB coordinates, and color differences ( and ΔE00 ) were obtained. The shade tabs selected by two experienced researchers were conducted as part of the pilot study, and finally used as a standard for the analysis. Data were analyzed using descriptive statistics and the chi-square test (p ≤ 0.05). Shade tabs selections of VSM and PSA agreed only for LT. The best "Match" selected by the researchers agreed with data from PSA using ΔE00 . PSA using ΔE00 showed higher total percentages of "Match" and higher percentage of agreement among observers. A relationship was found for LT performing the PSA (p < 0.05). The performance of the PSA was better than the VSM, but only when the CIEDE2000 color difference formula was used. Therefore, the color difference formulas influenced on the performance of PSA. Finally, the PSA improved the precision of the VSM. To use a standardized PSA to improve the VSM and shade communication in clinical esthetic dentistry.

Development of Bayesian Neural Network Model to Predict the Correlated Color Temperature Using Digital Camera and Macbeth ColorChecker Chart

Information about correlated color temperature influencing the scene due to the surrounding lighting is vital, especially for circadian lighting and photography. This paper proposes a novel image-based machine learning model to predict the correlated color temperature in a scene with the help of the Macbeth ColorChecker color rendition chart and a DSLR camera. In the proposed technique, the researcher fixes the white balance setting in the camera, thereby forcing color difference in the captured image of the Macbeth ColorChecker chart placed in the scene. The Bayesian neural network model considers the color difference values of the six spectrally neutral patches of the Macbeth ColorChecker chart as inputs for CCT prediction. The color differences are calculated using the CIEDE2000 color difference formula. Fours models with white balance settings in the camera as 5000 K, 6500 K, 8000 K, and 10000 K were developed and analyzed. It is experimentally found that the correlated color temperature prediction error is less than five percent by the proposed model with white balance setting in the DSLR camera as 10000 K. The proposed model performed consistently during varied lighting levels and mixed CCT lighting conditions set up with LED, incandescent, and fluorescent lamps.

Influence of background color on color perception in dentistry

ObjectiveTo evaluate the influence of neutral color backgrounds on the perception of color differences in dentistry. MethodsA software was developed for this study that calculated the perceptibility (PT) and acceptability (AT) thresholds of color differences between a pair of computer-simulated incisor samples (n = 60 pairs) over three neutral color (white, gray and black) backgrounds. CIELAB and CIEDE2000 color difference formulas were used. Five groups of volunteer observers (N = 100) participated in the psychophysical experiment (n = 20): Dentists; Dental students; Dental auxiliaries; Dental technicians; and Laypersons. The psychophysical experiment was performed in a dark environment on a calibrated high-resolution screen. To determine PT and AT values, the 60 pairs of samples were randomly presented to each observer over the different backgrounds. The data were adjusted (TSK Fuzzy) and analyzed statistically using Student t-test and ANOVA (α = 0.05). ResultsRegardless of the metric and the background used, the PT values showed no difference among different observers (p > 0.05). Dentists showed the lowest PT values. Dental technicians showed the lowest AT (p ≤ 0.05) and similar values for the three backgrounds (p > 0.05), regardless of the metric used. The other groups of observers showed the lowest and the highest AT values when using black and white backgrounds, respectively (p ≤ 0.05). ConclusionsThe lowest AT values using a black background indicates that the use of this background allows for the evaluation of slight color differences, and should be used for challenging color differences in esthetic dentistry. This study showed the influence of the observer experience on color evaluation in dentistry. Clinical significanceThere was no influence of the background color on the perceptibility threshold. However, dentists and dental technicians showed greater ability to perceive slight color differences compared to other groups of observers.

Visual and instrumental color evaluation of computerized color matching system for color reproduction of maxillofacial prostheses

Statement of problemA commercially available computerized color matching system (e-Skin) has been introduced for maxillofacial prostheses. However, studies that have tested its ability to produce an acceptable color match for skin color are lacking. PurposeThe purpose of this clinical study was to determine the color match acceptability of light and dark skin silicone replicas fabricated with the use of the computerized color matching system. Material and methodsFifteen participants with light skin and 15 participants with dark skin were recruited through personal invitation. These 30 participants (aged around 20 years) voluntarily consented to forearm skin color measurements with a spectrophotometer and a spectrocolorimeter integrated in a computerized color matching system. Silicone skin replicas for each participant were produced from the color formulations provided by the online calculator tool of the system according to the manufacturers’ recommendations. The color difference between initial skin color measurements with the spectrophotometer and skin replica color measurements with the spectrophotometer for all participants was calculated by using both the CIELab (ΔE∗ab) and CIEDE2000 (ΔE00) color difference formulas. To compare the instrumental and visual evaluation of color match, 3 observers (a maxillofacial prosthodontist, a prosthodontist, and a postgraduate student) visually evaluated and rated the color match of each silicone replica on a 5-point scale. Statistical analyses were performed by using the Student t, Mann Whitney U, and chi-square tests (α=.05). ResultsNo significant differences were detected between the light and dark skin groups in terms of the ΔE∗ab and ΔE00 values obtained between the first skin color measurements and their silicone replica color measurements (P=.573, P=.338, respectively). However, a significant difference was found between light and dark skin groups for the ΔL and Δa values obtained from the same measurements (P=.031, P=.017, respectively). L∗, a∗, and b∗ values of light skin were significantly higher than those of their silicone replications (P=.008, P=.033, P=.046, respectively). Color match ratings of observers did not significantly differ when comparing the ratings of light skin replicas to ratings of dark skin replicas. ConclusionsThe e-Skin system provided skin replicas that matched the skin color within clinically acceptable thresholds and with ratings of at least “good” by experienced dental clinicians.

Effect of mouth rinses on optical properties of CAD-CAM materials used for laminate veneers and crowns.

The purpose of this study was to investigate the effect of mouth rinses on the color and translucency of three computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials in laminate veneer and crown thicknesses. Specimens from two different 5Y-TZP zirconia (InCoris TZI (IT), and Zirkonzahn (ZH)) and lithium disilicate (IPS e.max CAD [IC]) in two different thicknesses (0.7 mm for laminate veneer, and 1.5 mm for crown) were sectioned. All specimens were colored with an A2-shade liquid, and the baseline color values were recorded according to the CIELab system with a spectrophotometer. Each group was divided into two subgroups (n=15) according to the immersion solution: two different mouth rinses, KL (Klorhex), and LI (Listerine, cool mint) for 180 hours. The color coordinates (L*, a*, b*) of the specimens were measured before and after immersion in a mouth rinse, and TP and ΔE00 color differences were calculated by using the CIEDE2000 color difference formula. A 3-way ANOVA, Bonferroni test, and 1-sample t tests were used to analyze the data (α=0.05). The 3-way ANOVA revealed a significant interaction of material, thickness, and mouth rinse for translucency parameter and color difference (ΔE00 ) data (p < 0.001). TP decreased for both zirconia materials in laminate veneer thickness when immersed in LI mouth rinse (p < 0.05). No difference was found among the TP mean values of three materials in crown thickness after immersed in mouth rinses (p > 0.826). Both zirconia materials immersed in LI showed greater discoloration than after immersed in KL (p < 0.05). A significant difference was found in color change values among three materials for the laminate veneer thickness after immersed in LI (p < 0.001). However, all color difference values were within the clinical acceptability threshold, except for when ZH in laminate veneer thickness was immersed in LI. The color change of ZH zirconia with LI mouth rinse in laminate veneer thickness was high. For both zirconia ceramics, translucency decreased and the color was less stable in laminate veneer thickness after immersed in LI compared to the crown thickness. The results of this in vitro study suggest that long-term use of alcohol-containing mouth rinse may alter the optical properties of tested CAD-CAM materials in tested laminate veneer thickness. For color stability with the long term use of tested mouth rinses, lithium disilicate may be preferred for both types of restorations.

Effect of in vitro aging and acidic storage on color, translucency, and contrast ratio of monolithic zirconia and lithium disilicate ceramics

Statement of problemHow the translucency and color of ceramic restorations are affected by surface changes from the corrosive environment in the oral cavity and aging of materials is unclear. PurposeThe purpose of this in vitro study was to compare the impact of acidic exposure and aging on the color and translucency of monolithic zirconia and lithium disilicate ceramics. Material and methodsTwenty computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic zirconia specimens and 20 pressed lithium disilicate specimens were fabricated. Half of the specimens of each group were aged in an autoclave (7.5 hours, 134 °C, 0.2 MPa), and the rest were immersed in hydrochloric acid to simulate the acidic conditions in the oral cavity from gastric reflux. The color coordinates L∗, a∗, and b∗ were measured with an ultraviolet spectrophotometer before and after aging or acidic storage. The translucency parameters and contrast ratios were calculated, and the CIEDE2000 color difference formula was used to determine color differences before and after each treatment. ANOVA and ANCOVA test models were used for data analysis (α=.05), while differences of color parameters in respect to acceptability and perceptibility thresholds were evaluated with the 1-sample t test (α=.05). ResultsLithium disilicate presented a significantly higher translucency parameter and lower contrast ratio at baseline compared with monolithic zirconia specimens (P<.001). Acidic storage significantly impacted all parameters compared with aging, especially for the lithium disilicate group. Color differences were above the acceptability ΔΕ00 threshold for lithium disilicate after acidic storage (P=.001) and below for monolithic zirconia after acidic storage (P=.003). ConclusionsThe performance of lithium disilicate was slightly inferior compared with that of monolithic zirconia specimens, as they presented significant and clinically observable differences for the translucency parameter and ΔΕ00 after acidic storage and aging.

Comparison of judgment results between the color comparison method of urine analysis test papers using the CIE DE2000 color-difference formula and the automatic urine analyzer

Comparison of judgment results between the color comparison method of urine analysis test papers using the CIE DE2000 color-difference formula and the automatic urine analyzer

ProLab: A Perceptually Uniform Projective Color Coordinate System

The construction of perceptually uniform color space is an important task of color theory. Many image processing applications requires the color difference to replicate human perception. The perceptual difference is poorly approximated by Euclidean distance within linear color coordinate systems, in particular, within CIE XYZ. Almost all uniform color spaces are constructed as some nonlinear transformation from CIE XYZ. Such transformations do not preserve the straightness of the color tone curves and other collinearity properties which are important for high dynamic range and wide color gamut imagery and required for linear color analysis, including separation of homogeneous backgrounds. In this work, we propose proLab, a new color coordinate system derived as a 3D projective transformation of CIE XYZ that preserves the linearity of manifolds by definition. We show that proLab is far superior to the widely used CIELAB coordinate system (though inferior to the modern CAM16-UCS) in terms of perceptual uniformity, evaluated by the STRESS metric in reference to the CIEDE2000 color difference formula. We also demonstrate that shot noise in proLab is more homoscedastic than in CAM16-UCS or other standard color spaces. This makes proLab a convenient coordinate system for linear color analysis.