Search Results (84)

Projection-based spatial augmented reality (P-SAR) supports appearance-oriented design evaluation by projecting digital materials onto physical mock-ups, but the projected result may deviate from the intended screen-rendered appearance in both colour distribution and normal-induced shading. This paper proposes a screen-referenced, measurement-driven appearance optimisation framework in which a calibrated monitor serves as the visual reference and the projected mock-up as the optimisation target. The workflow combines controlled Unity rendering, colourimetric measurement, D65 CIE Lab analysis, and MATLAB (R2024b)-based iterative update, and separates the problem into albedo appearance optimisation and shading appearance optimisation. The albedo branch uses dominant-colour grouping and CIEDE2000-guided group-wise correction, while the shading branch uses a lightness-contrast descriptor derived from flat and normal-modulated renderings to update the normal-map-driven shading response. Experiments on ten material textures showed that all 23 identified colour groups converged below the adopted $\Delta E_{00}$ threshold of 2.3; the mean texture-level colour difference decreased from 6.24 to 1.36, corresponding to an average reduction of 77.43%. Comparative evaluation showed that the proposed group-wise optimisation outperformed global neutral-grey and global Lab-offset correction baselines. For shading, the mean residual $r_D=|D_{\mathrm{proj}}-D_{\mathrm{ref}}|$ decreased from 1.164 to 0.264 $L^{\ast }$ units, and all ten normal-map cases satisfied the 1.0 $L^{\ast }$ tolerance. A comparison with a global luminance-contrast baseline further supported the benefit of material-level normal-map update over image-domain contrast adjustment. Additional analyses examined the sensitivity to the number of dominant colour groups and clarified the rationale and scope of the adopted thresholds. Integrated photographic examples provided qualitative illustrations of the overall appearance tendency after the complete workflow, while the quantitative assessment was based on colourimetric and lightness-domain measurements. The full workflow required approximately 26 min per material case, indicating practical feasibility for controlled or semi-controlled P-SAR material appearance preparation and design-review scenarios. Full article

Background/Objectives: Esophageal cancer is one of the major global causes of cancer mortality, and the 5-year survival rate remains below 20% because many cases are detected late. In this study, a Spectral-Aided Vision Enhancer (SAVE) algorithm was utilized to convert conventional white-light endoscopic images (WLI) into hyperspectral-like narrow-band imaging (NBI) images for machine-learning classification of Dysplasia, Normal, and Squamous Cell Carcinoma (SCC). Methods: A total of 762 WLI images obtained from Kaohsiung Medical University were augmented to 1074 using the Al bumentations library, employing vertical flipping, horizontal flipping, and rotations. The SAVE conversion pipeline employs a 24-patch Macbeth color checker for calibration, γ-correction, CIE XYZ transformation, and multivariate regression to interpolate spectral bands, yielding an average color difference of 2.79 (CIEDE2000) from true NBI. The training outcomes and performance metrics illustrate the versatility of the machine learning/deep learning models—Random Forest (RF), Support Vector Machine (SVM), and Convolutional Neural Network (CNN)—which were trained and evaluated on both the original WLI and SAVE datasets. Performance metrics were analyzed based on precision, recall, accuracy, and F1-score. Results: The CNN sample achieved an accuracy of 100 percent on SAVE data, compared to 93 percent for WLI. The accuracy of RF improved, with WLI at 91% and SAVE at 96%, while SVM increased from 79% to 84%. These improvements indicate the diagnostically valuable spectral variations that can be amplified with SAVE, resulting in significant enhancements in pre-cancer/SCC sensitivity. Conclusions: The proposed SAVE method demonstrates significant potential for enhancing endoscopic imaging and advancing computer-aided diagnosis in esophageal cancer screening, with applicability in other gastrointestinal imaging scenarios as well. Full article

Background/Objectives: Modern restorative dentistry increasingly focuses on achieving optimal aesthetic integration while simplifying clinical procedures. Single-shade resin composites were introduced to reduce the complexity of conventional multi-shade layering techniques through enhanced color adjustment potential and structural color technology. However, concerns remain regarding their long-term color stability. The aim of this systematic review was to evaluate the color stability and aesthetic performance of single-shade resin composites compared with conventional multi-shade systems under different staining and aging conditions. Methods: This systematic review was conducted according to PRISMA 2020 guidelines and registered in the Open Science Framework. A systematic search was performed in PubMed, Scopus, and Cochrane Library up to 31 October 2025. Studies evaluating color stability using the CIEDE2000 (ΔE₀₀) formula after staining and aging procedures were included. Risk of bias was assessed using the RoBDEMAT tool. Results: The search identified 169 records, of which 11 in vitro studies met the inclusion criteria. Across the included studies, discoloration increased progressively over time, and chromogenic agents frequently induced ΔE₀₀ values exceeding clinical acceptability thresholds. Turmeric and red wine demonstrated the highest staining potential, whereas distilled water and artificial saliva showed minimal color variation. Single-shade composites generally exhibited greater susceptibility to discoloration than multi-shade systems, although variability among materials was observed depending on composition and experimental conditions. Conclusions: Single-shade resin composites simplify restorative procedures and provide initial aesthetic integration; however, they appear more susceptible to clinically relevant discoloration under experimental conditions. Further clinical and in vitro investigations are required to confirm these findings. Full article

Background: The aim of this study was to evaluate the whitening efficacy and long-term stability of different in-office bleaching agents containing high concentrations of hydrogen peroxide (HP). Methods: Records of 50 patients who underwent in-office bleaching treatment at the Department of Restorative Dentistry, Ege University, were retrospectively analyzed. Five bleaching agents were evaluated: Opalescence (40%HP), FGM Whiteness HP (35%HP), FGM Whiteness HP Blue (35%HP), Biowhiten (40%HP) and Powerbright (35%HP). Color measurements were obtained using a spectrophotometer (VITA Easyshade V, VITA Zahnfabrik, Bad Säckingen, Germany) and standardized intraoral photographs at baseline, immediately after treatment, at 1 week, 6 months, 12 months, and 18 months. Color change (ΔE₀₀) was calculated using the CIEDE2000 formula, and shade differences were assessed using ΔSGU values. Statistical analyses were performed using repeated-measures ANOVA and Kruskal–Wallis tests, followed by post hoc comparisons where appropriate (p < 0.05). Results: Baseline age distribution, initial color parameters, and patient-related behavioral factors were comparable among the groups, with no statistically significant differences observed. All bleaching agents resulted in significant color improvement at the 1-week evaluation (ΔE₀₀ range: 3.67–6.34; p < 0.05), exceeding clinically acceptable thresholds. At 6 months, slight, non-significant reductions in ΔE₀₀ values were observed in the Powerbright, FGM Whiteness HP Blue, and FGM Whiteness HP groups (p > 0.05). At 18 months, ΔE₀₀ values remained within a clinically acceptable range (3.56–4.74), with no significant color regression in most groups (p > 0.05), except for a significant decrease in the FGM Whiteness HP group (p < 0.05). Conclusions: High-concentration (35–40%) in-office bleaching agents demonstrated effective short-term whitening and maintained clinically acceptable and stable color outcomes over 18 months. Although material-dependent differences were observed, bleaching efficacy and long-term color stability appear to be influenced by multiple factors beyond hydrogen peroxide concentration alone. These findings support the clinical reliability of in-office bleaching procedures and highlight the importance of long-term follow-up. Full article

Plaque-disclosing agents are widely used to enhance visualization of dental biofilm. However, their chromogenic components may adhere to enamel surfaces, resulting in transient extrinsic discoloration. This study evaluated the extent and short-term recovery of such discoloration and compared three removal modalities in terms of enamel color change (CIEDE2000, ΔE₀₀), surface roughness (Ra), and gloss (GU). Extracted human anterior teeth with intact buccal enamel were stained using an erythrosine-based disclosing agent and randomly allocated into three groups (n = 15): manual brushing with conventional toothpaste, rubber-cup polishing with a perlite-containing paste (1000 rpm, 5 s), or erythritol-based air-polishing (5 s; 50% power/100% water). ΔE₀₀ was measured at baseline, immediately after cleaning, and after 1 week of storage in artificial saliva. Ra and GU were recorded at baseline and post-cleaning. Data were analyzed using appropriate tests (p < 0.05). All modalities were associated with a reduction in visible discoloration without significantly affecting Ra or GU (p > 0.05). Immediate ΔE₀₀ values remained above commonly reported acceptability thresholds, indicating residual discoloration. Partial color recovery occurred after artificial saliva storage. Within the limitations of this study, the findings indicate no statistically significant differences among the tested procedures, without evidence of superiority of any single modality. Full article

Objectives: This study aimed to evaluate the masking ability of different thicknesses of advanced lithium disilicate (ALDS) ceramic used for implant-supported crowns compared to conventional lithium disilicate (LDS) and to assess the influence of their combination with various implant abutment materials. Methods: Two types of high-translucency computer-aided design/computer-aided manufacturing (CAD/CAM) glass–ceramics in shade A2 were tested: IPS e.max CAD (LDS) and CEREC Tessera (ALDS). Each material was sectioned into four thicknesses (n = 8 per group). Four implant abutments were evaluated: titanium (Ti), yellow-anodized titanium (TiY), pink-anodized titanium (TiP), and white zirconia (Zir). The translucency parameter (TP₀₀) and color difference (ΔE₀₀) between the glass–ceramic and abutment were calculated using the CIEDE2000 formula. Results: Significant differences were observed between 1.0 mm and 2.5 mm thicknesses in all groups except for ALDS on TiY. Both glass–ceramics on TiY and TiP showed lower ΔE00 values than those on Ti, except for 2.0 mm and 2.5 mm ALDS. Additionally, their ΔE00 values were lower than those on Zir. Clinically acceptable ΔE₀₀ values occurred for 2.5 mm LDS on TiP, 2.0 mm ALDS on TiY and TiP, and 2.5 mm ALDS on TiY and TiP. ALDS demonstrated lower TP₀₀ values than LDS at corresponding thicknesses. Conclusions: Greater restoration thickness and titanium anodization improved color masking. Anodized titanium enhanced the glass–ceramic masking ability. ALDS at 2.0–2.5 mm on TiY or TiP and 2.5 mm LDS on TiP achieved clinically acceptable masking, with ALDS showing lower translucency than LDS. Full article

This study evaluated the effects of thermocycling on surface roughness (Ra), gloss (GU), color stability (ΔE₀₀), and water sorption of interim materials manufactured by three methods. Disc specimens (n = 20/group) were fabricated from a conventional bis-acryl (PreVISION^® Temp), a computer-aided design/computer-aided manufacturing (CAD/CAM)-milled methacrylate-based composite (StructurCAD Disc^®), and a 3D-printed resin composite (Alias Dental Temp C&B^®). Two disc dimensions were used: 10 × 2 mm for Ra, GU, and color, and 15 × 1 mm for water sorption. Measurements were performed before and after thermocycling (10,000 cycles; 5–55 °C). Nonparametric tests were used (α = 0.05). After thermocycling, Ra increased in the conventional and 3D-printed groups, whereas the milled group demonstrated a decrease (p < 0.05). GU decreased across all groups (p < 0.001) and differed among materials (p = 0.021), with a significant difference only between milled and 3D-printed groups. Color stability differed among materials (p < 0.001): the milled group showed the lowest ΔE₀₀ perceptibility threshold (below PT₀₀ = 0.81), whereas conventional and 3D-printed groups exceeded the acceptability threshold (AT₀₀ = 1.81). Water sorption differed among groups (p < 0.001), with a significant difference between the milled and 3D-printed groups (p < 0.001). The tested 3D-printed material exhibited less favorable post-thermocycling optical properties, whereas the evaluated CAD/CAM-milled material demonstrated more favorable overall surface and optical performance under the applied aging conditions. Full article

We propose a Dual-Channel assisted Music Emotion Perception and Visualization (DC-MEPV) framework designed for ambient lighting in intelligent vehicle cockpits, addressing the increasing demand for advanced human–machine interaction in the automotive industry. This framework consists of three main components: the Multi-Scale Feature Extraction Block (MSFEB), the Global Sequence Modeling Block (GSMB), and the Emotional Color Visualization Algorithm (ECV-Algo). The MSFEB extracts valence and arousal (V-A) features from dual channels at multiple temporal scales, with each channel employing a hybrid neural network architecture to capture multi-scale emotional representations. The GSMB integrates positional encoding, bidirectional long short-term memory (BiLSTM) networks, and multi-head self-attention mechanisms to dynamically model global emotional sequences. The ECV algorithm utilizes personalized emotion–color association rules to achieve expressive emotion-driven lighting visualization based on a continuous mapping from emotion space to color space. We conducted comprehensive comparison and ablation experiments to evaluate the model’s emotion perception performance, and designed three metrics to evaluate the quality of the generated visualizations. The model outperformed other networks in both comparative and ablation experiments. Additionally, the generated lights demonstrated strong performance in terms of CIEDE2000 variation rates, unique color ratios, and joint histogram entropy. DC-MEPV achieved excellent performance in emotion perception and visualizations on the DEAM and PMEmo datasets. Full article

Objective: This in vitro study aimed to compare the layer-matched color compatibility of three 3Y/4Y/5Y multilayer zirconia grades marketed in shade A2. Materials and Methods: Disc specimens (18 mm × 1.5 mm) were milled from pre-shaded multilayer zirconia blanks (Katana™ Multi-Layered Zirconia; Kuraray Noritake Dental Inc., Tokyo, Japan) in three grades: UTML (5Y), STML (4Y), and HTML (3Y). Twelve discs per grade were polished and measured on a neutral-gray background (Munsell N7) using a dental spectrophotometer (VITA Easyshade Advance 4.0; VITA Zahnfabrik, Bad Säckingen, Germany) at the incisal, middle, and cervical thirds. Color differences were calculated using CIEDE2000 (ΔE₀₀). Yttria content (wt%) was determined using EDS (JSM-7800F; JEOL Ltd., Tokyo, Japan), and phases were assessed using XRD (X’Pert PRO; Malvern Panalytical, Almelo, The Netherlands); microstructure and grain size were examined using FE-SEM after thermal etching. Statistics: A two-way mixed-design ANOVA with Bonferroni adjustment (α = 0.05) was conducted. Results: A significant incisal-to-cervical gradient was observed within each grade (p < 0.001), whereas layer-matched inter-material differences were small (all ΔE00 < 1.0), i.e., below the commonly accepted perceptibility threshold. EDS confirmed the expected stepwise decrease in Y₂O₃ from UTML to HTML, accompanied by corresponding changes in phase constitution and grain size. Conclusions: Despite compositional and microstructural differences, the three multilayer zirconia grades showed no clinically perceptible layer-matched color differences, supporting their combined use in extended rehabilitations while maintaining the natural-like color gradient across the multilayer blank. Full article

This in vitro study evaluated and compared the surface roughness, color stability, and gloss of two single-shade composite resins after simulated toothbrushing, and investigated the correlations among these parameters. Twenty disk-shaped specimens (n = 10 per group) were prepared from two single-shade composite resins (Material A and Group B) and subjected to simulated toothbrushing up to 15,000 cycles. Surface roughness (Ra) was measured at baseline and after 5000, 10,000, and 15,000 cycles. Color parameters (CIE Lab*) and gloss (60°) were measured at baseline and after 15,000 cycles. Color change was calculated using the CIEDE2000 formula (ΔE₀₀). Data were analyzed using two-way mixed ANOVA, t-tests, and Pearson correlation analysis (α = 0.05). Both materials showed progressive increases in surface roughness. Material B exhibited significantly higher Ra values than Material A from 10,000 cycles onward (p < 0.01). After 15,000 cycles, Material B demonstrated significantly greater color change (ΔE₀₀: 2.21 ± 0.18 vs. 1.48 ± 0.13; p < 0.001), exceeding the acceptability threshold (ΔE₀₀ = 1.8), while Material A remained clinically acceptable. Material B also showed greater gloss reduction (60% vs. 35%; p < 0.001). Strong correlations were found between surface roughness and both gloss change (r = −0.919) and color change (r = 0.826). Material A demonstrated greater resistance to surface degradation and better preservation of optical properties compared to Material B. Surface roughness was identified as the common underlying factor driving both color instability and gloss reduction in single-shade composites. Clinical Significance: Not all single-shade composites perform equally under mechanical aging. Clinicians should consider the filler technology and long-term surface stability when selecting single-shade composite resins for clinical use. Full article

Long-term aesthetic success in dentistry largely depends on the color stability of restorative materials. This study investigated the color changes (ΔE₀₀) of resin nanoceramic and lithium disilicate ceramic restorative materials used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems following beverage immersion and after repolishing. One hundred specimens were prepared from lithium disilicate (Initial LiSi Block) and resin nanoceramic (Cerasmart), and polished. The specimens were divided into ten groups according to material and beverage type (n = 10) and immersed in distilled water, cola, tea, coffee, and turnip juice at 37 °C for 3 months. Color values were recorded at baseline, 1 week, 1 month, and 3 months, and after repolishing. ∆E₀₀ values were calculated using the CIEDE2000 color difference formula. Data were analyzed using three-way repeated measures ANOVA and post hoc Tukey and Bonferroni tests (α = 0.05). Material type, beverage type, and immersion time significantly affected color stability (p < 0.05). The highest ∆E₀₀ observed in the resin nanoceramic–tea group at 3 months (ΔE₀₀ = 11.39 ± 1.76). Lithium disilicate demonstrated better color stability. After repolishing, all ΔE₀₀ values were below the clinically acceptable limit (ΔE₀₀ ≤ 1.8). Repolishing may help maintain the long-term aesthetic success of dental restorations in the oral environment. Full article

Introduction: Recent advancements in technologies, such as 3D printing, have been adopted in prosthodontics to streamline clinical procedures and provide high-quality prosthetic devices to patients within a reduced timeframe. Aim of the study: This study primarily aimed to determine the color change levels of 3D-printed dental resins for temporary and long-term intraoral applications. We also evaluated the effectiveness of post-processing procedures such as polishing or glazing on color stability. Materials and methods: Three types of dental resins were tested in distilled water, coffee, and wine environments for 2, 7, 30, and 60 days. A spectrophotometric analysis was conducted, and the Ciede2000 formula was used to determine the DE. Results: The material type, conditioning method, and storage time significantly affected the color changes of the tested materials. The post-processing technique had the most remarkable impact on color stability over time. Conclusions: Glazing of the 3D-printed material surface appears to be the most effective approach to prolong its clinical applicability by maintaining color stability. Full article

Background/Objectives: The increasing use of digital manufacturing techniques in prosthodontics has raised concerns regarding the long-term esthetic performance of provisional restorations. This in vitro study aimed to compare the color stability of provisional restorations fabricated by additive (3D-printed) and subtractive (milled) manufacturing techniques after immersion in common staining beverages. Methods: Eighty polymethyl methacrylate (PMMA)-based specimens (16 × 1 mm) were fabricated and divided into two groups: additive (n = 40) and subtractive (n = 40). Each group was immersed in coffee, red wine, green tea, or cola for 60 and 120 h at 37 °C. Color measurements were recorded using a spectrophotometer in the CIE LCh* system, and color differences (ΔE₀₀) were calculated using the CIEDE2000 formula. Data were analyzed using repeated-measures analysis of variance (ANOVA) and Tukey post hoc tests (α = 0.05). Results: Additively manufactured specimens showed significantly higher color change (ΔE₀₀) values than subtractively milled specimens across all immersion media and time intervals (p < 0.05). Red wine and coffee caused the greatest discoloration, whereas cola produced the least effect. Conclusions: Within the limitations of this study, additive manufacturing resulted in lower color stability than subtractive fabrication. Subtractive PMMA materials exhibited superior optical behavior, suggesting their suitability for long-term provisionalization in esthetically demanding clinical situations. Full article

This study aimed to evaluate the intra-model repeatability of three artificial intelligence-based chatbots (ChatGPT-4.0, Microsoft Copilot, and Claude 3.5) in composite shade selection and their agreement with a dental specialist. Ten acrylic resin maxillary central incisor teeth representing different VITA Classical shades (n = 10) were photographed together with A1, A2, and A3 composite shade tabs under standardized illumination. Shade selections were performed by each artificial intelligence model based on the photographs and repeated on five different days using identical images and prompts. Visual shade selection by the dental specialist was determined by consensus between two calibrated evaluators. CIE L*, a*, and b* values of the acrylic teeth and composite shade tabs were obtained by photometric analysis, and color differences were calculated using the CIEDE2000 formula. Intra-model repeatability was assessed using Fleiss’ kappa coefficient, and agreement with the dental specialist was evaluated using Cohen’s kappa statistic. Intra-model repeatability differed among the models, with ChatGPT-4.0 demonstrating fair repeatability (κ = 0.33), Claude 3.5 showing moderate repeatability (κ = 0.45), and Microsoft Copilot exhibiting poor repeatability (κ = −0.12). Trial-level agreement with the dental specialist varied across repeated assessments, with ChatGPT-4.0 generally demonstrating higher agreement than the other models, whereas Microsoft Copilot showed consistently low agreement. Artificial intelligence chatbots showed variable repeatability and limited agreement with expert evaluation in composite shade selection under standardized conditions. Full article

Motivation: Accurate spectral reconstruction of printed halftone images is essential for achieving high-fidelity color reproduction and robust color management across modern printing systems. However, traditional physics-based models, such as the Yule–Nielsen and Clapper–Yule formulations, rely on simplified empirical assumptions and often fail to capture the complex nonlinear and asymmetric interactions induced by multi-ink overlays and substrate light scattering. Meanwhile, existing data-driven approaches based on single learning models exhibit limited capability in modeling the complementary and symmetrical characteristics inherent in halftone structures, resulting in suboptimal prediction accuracy and generalization performance. Method: To address these limitations, we propose a Stacking Ensemble Spectral Prediction (SESP) framework. The proposed method adopts a two-layer stacking architecture that integrates heterogeneous base regressors, including Support Vector Regression (SVR), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost 3.0.3), with Ridge Regression employed as the meta-learner for optimal prediction aggregation. This ensemble design enables effective modeling of both halftone pattern symmetry and complex substrate scattering behavior. Results: Extensive experiments conducted on printed halftone image datasets demonstrate the superior performance of the proposed SESP framework. Compared with the best-performing reference method (PCA-IPSO-DNN), SESP achieves relative reductions in RMSE and CIEDE2000 of 12.8% and 6.8% under illuminant A, 9.5% and 6.9% under D50, and 12.2% and 7.2% under D65, respectively. In addition, SESP consistently outperforms traditional physics-based models, including Yule–Nielsen and Clapper–Yule, in terms of both spectral prediction accuracy and colorimetric fidelity. These results confirm the effectiveness of the proposed framework in modeling the intricate nonlinear and asymmetric relationships between CMYK halftone patterns and spectral reflectance. Full article