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Biopolymers are biodegradable and renewable and can significantly reduce environmental impacts. For this reason, biocomposites based on a plasticized starch and cross-linker matrix and with a microfibrillated OCC cardboard cellulose reinforcement were developed. Biocomposites were prepared by suspension casting with varied amounts of microfibrillated cellulose: 0, 4, 8, and 12 wt%. Polyethylene glycol diglycidyl ether (PEGDE) was used as a cross-linking, water-soluble, and non-toxic agent. Microfibrillated cellulose (MFC) from OCC cardboard showed appropriate properties and potential for good performance as a reinforcement. In general, microfiber incorporation and matrix cross-linking increased crystallization, reduced water adsorption, and improved the physical and tensile properties of the plasticized starch. Biocomposites cross-linked with PEGDE and reinforced with 12 wt% MFC showed the best properties. The chemical and structural changes induced by the cross-linking of starch chains and MFC reinforcement were confirmed by FTIR, NMR, and XRD. Biodegradation higher than 80% was achieved for most biocomposites in 15 days of laboratory compost. [ABSTRACT FROM AUTHOR]

To evaluate the influence of printing orientation on flexural strength (σf) and elastic modulus (E) of different 3D printing dental restorative resins. Bar-shaped specimens (n = 20) were fabricated from two SLA-printed resins (FT- Formlabs Temporary, and FP- Formlabs Permanent) and two DLP-printed resins (DFT- Detax Freeprint Temp, and GCT- GC Temporary) using two building orientations (0º and 90º). The 3D-printed structures were aged (14 d) before submitted to three-point bending in 37ºC distilled water at a crosshead speed of 1.0 ± 0.3 mm/min until fracture to calculate the σf and the E values. The fractured surfaces were evaluated using stereomicroscopy and scanning electron microscopy (SEM) following fractography principles. Data were statistically analyzed using two-way ANOVA and Tukey post-hoc (α = 0.001). FP and FT showed significantly higher E values than DFT and GCT, irrespectively of printing orientation (p < 0.001). There was no statistical difference between the building orientations (0º and 90º) for the mean σf and E values for the resin materials evaluated. Fractographic characteristics were similar for the surface fracture from all the materials evaluated, showing typical brittle fracture behavior. Printing orientation did not influence of flexural strength and elastic modulus values for the 3D-printed resin structures evaluated. Surface topography was mostly governed by the 3D printer type. • Mechanical properties such as flexural strength and elastic modulus were not affected by the printing angle. • The surface topography of the evaluated 3D-printing resins is mostly governed by the printer type. • Typical brittle fracture features were found for the evaluated 3D-printing resins. [ABSTRACT FROM AUTHOR]

Objectives: Determine visual 50:50% color difference acceptability thresholds (AT) for regions of the dental color space with varying chromaticity. Methods: A 40‐observer panel belonging to two different groups (dentists and laypersons) evaluated 144 dental resin composites pairs (divided in three different sets of 48 pairs according to chroma value: Low Chroma (LC), Medium Chroma (MC) and High Chroma (HC) placed 40 cm away and inside of a viewing cabinet (D65 Standard light source; diffuse/0° geometry). A Takagi–Sugeno–Kang (TSK) fuzzy approximation was used for fitting the data points and calculate the 50:50% acceptability thresholds in CIEDE2000. A paired t‐test was used to evaluate the statistical significance between thresholds differences and Bonferroni correction was applied. Results: The CIEDE2000 50:50% AT were ∆E00 = 2.84, ∆E00 = 2.31 and ∆E00 = 1.80 for LC, MC and HC sets of sample pairs, respectively. The 50:50% AT values were statistically significant between the different sets of sample pairs, as well as the 50:50% AT values obtained for different observer groups. Conclusions: 50:50% CIEDE2000 acceptability thresholds for dentistry are significantly different depending on the chromaticity of the samples. Observers show higher acceptability for more achromatic samples (low chroma value) than for more chromatic samples. Clinical Significance: The difference in the AT for distinct regions of the dental color space can assist professionals as a quality control tool to assess clinical performance and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization processes. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate gingiva‐colored resin‐based composites' (GCRBC) color stability and degree of conversion (DC%). Methods: Eight discs (8 × 1 mm) of 20 shades of GCRBC were prepared. Color coordinates were measured against a gray background with a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry at baseline and after 30 days of storage in distilled water, coffee, and red wine. Color differences (∆E00) between final and baseline conditions were calculated. An ATR‐FTIR spectrometer with a diamond tip was used to calculate DC%. The results were analyzed statistically using ANOVA and Tukey post‐hoc test. The level of significance was p < 0.05. Results: DC% and color stability correlated with each other and with the GCRBC brand. DC% ranged between 43% and 96%, highest values correspond to flowable composites. All composites have experienced color changes after immersion in water, wine and coffee. However, the magnitude of the color change has varied widely depending on the immersion medium and the GCRBC. Color changes generated by the wine were, globally, greater than those induced by coffee (p < 0.001) and above the acceptability thresholds. Conclusions: The DC% of GCRBCs is sufficient to achieve adequate biocompatibility and physicomechanical properties, but the high susceptibility to staining could compromise aesthetic long‐term results. Clinical Significance: The degree of conversion and the color stability of gingiva‐colored resin‐based composites correlated with each other. All composites have experienced color changes after immersion in water, wine and coffee. Color changes generated by wine were, globally, greater than those induced by coffee and above the acceptability thresholds that could compromise aesthetic long‐term results. [ABSTRACT FROM AUTHOR]

Transparent conductive electrodes have become essential components of numerous optoelectronic devices. However, their optical properties are typically characterized by the direct transmittance achieved by making use of spectrophotometers, avoiding an in-depth knowledge of the processes involved in radiation attenuation. A different procedure based on the Double Integration Sphere combined with the numerical Inverse Adding-Doubling (IAD) method is employed in this work to provide a comprehensive description of the physical processes limiting the light transmittance in commercial indium tin oxide (ITO) deposited on flexible PET samples, highlighting the noticeable contribution of light scattering on the total extinction of radiation. Moreover, harnessing their flexibility, the samples were subjected to different mechanical stresses to assess their impact on the material's optical and electrical properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Objective To determine the visual whiteness thresholds for esthetic dentistry using the whiteness index for dentistry based on CIELAB color space (WI D). Methods A total of 60 observers (Dentists and Laypersons; n = 30) from three research sites participated in the study. A psychophysical experiment based on visual assessments of simulated images of teeth on a calibrated display was performed. Images of simulated upper central incisors (SUCI) were consecutively displayed in pairs (60) and the whiteness of each SUCI pair was compared. WI D was used to calculate the visual thresholds (WPT- perceptibility threshold; and WAT- acceptability threshold) with 95% confidence intervals (CI) and a Takagi-Sugeno-Kang (TSK) Fuzzy Approximation model was used as fitting procedure. Data was statistical analyzed using paired t -test (α = 0.05). Results WPT and WAT were 0.72 (CI: 0.0–2.69; r2 = 0.52) and 2.62 (CI: 0.2-7+; r2 = 0.57) WI D units, respectively. Significant differences (p < 0.05) were found between WPT and WAT, and between dentist (WPT = 0.46WI D units; WAT = 2.20 WI D units) and layperson (WPT = 0.94 WI D units; WAT = 2.95 WI D units). Significance The visual whiteness difference thresholds determined with WI D index can serve as reference values for research and manufacturing of dental materials, and for clinical practice situations such as assessing the effectiveness of bleaching treatments. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To determine 50:50% perceptibility threshold (PT) and 50:50% acceptability threshold (AT) for computer‐simulated samples of human gingiva using CIEDE2000 and CIELAB color difference formulas. Materials and Methods: Each of the 60 pairs of simulated human gingiva was displayed on a calibrated monitor, together with three pairs of upper central incisors of different lightness. The color of gingiva left and right from the midline was compared. A total of 30 observers (15 dentists, 15 laypersons) participated in the study. CIEDE2000 and CIELAB formulas were used to calculate the thresholds and a Takagi‐Sugeno‐Kang Fuzzy Approximation model was used as fitting procedure. Paired t‐test (α = 0.05) was used in evaluation of statistical significance of differences. Results: The PT and AT for CIEDE2000 and 95% confidence intervals were 1.1 [0.4, 1.7] and 2.8 [1.8, 4.0], respectively. Corresponding CIELAB values were 1.7 [0.2, 2.6] and 3.7 [2.1, 5.7]. Significant differences (P < .01) were recorded between PT and AT, between the corresponding threshold values in CIEDE2000 and CIELAB formulas as well as between dentists and laypersons. Conclusions: The difference between the perceptibility and acceptability threshold for gingiva was statistically significant in both CIEDE2000 and CIELAB. The same was true for differences between the corresponding thresholds using two color difference formulas, and between dentists and laypersons. Visual thresholds of human gingiva were not dependent upon lightness of adjacent teeth. Overall, CIEDE2000 color difference formula provided better fit than CIELAB formula in the evaluation of color difference thresholds of human gingiva. Clinical Significance: The data on visual thresholds for healthy human gingiva can be used as quality control tool/guide for selection and evaluation of dental materials, interpretation of color‐related findings in clinical dentistry and research, and for standardization in dentistry. It is of particular value that this study was designed based on in‐vivo color evaluation of healthy keratinized gingiva of subjects of different ethnicities, age groups, and gender. [ABSTRACT FROM AUTHOR]

Objectives To analyze the influence of lightness, chroma and hue differences on visual shade matching performed by dental students. Methods 100 dental students (DS) volunteers with normal vision participated in the study. A spectroradiometer (SP) was used to measure the spectral reflectance of 4 extracted human upper central incisors (UCI 1-4) and shade tabs from Vita Classical (VC) and Vita Toothguide 3D-Master (3D) shade guides. Measurements were performed over a gray background, inside a viewing booth and under D65 illuminant (diffuse/0° geometry). Color parameters ( L *, a *, b *, C * and h °) were calculated. DS used VC and 3D to visually select the best shade match for each UCI. CIE metric differences ( Δ a * , Δ b * , Δ L ′ , Δ C ′ and Δ H ′ ) and CIEDE2000(2:1:1) lightness ( Δ E L ), chroma ( Δ E C ) and hue ( Δ E H ) differences were obtained from each UCI and the first three shades selected by DS and the first option using CIELAB, CIEDE2000(1:1:1) and CIEDE2000(2:1:1) color difference metrics. The closest CIELAB color-discrimination ellipsoid (from RIT-DuPont visual color-difference data) to each UCI was selected for the analysis of visual shade matching. Results DS showed a preference for shades with lower chroma ( Δ C ′ and Δ E C ) and/or hue ( Δ H ′ and Δ E H ) values instead of shades with lower lightness values ( Δ L ′ and Δ E L ). Most best visual matches were near the tolerance ellipsoid centered on tooth shade. Significance This study is an attempt to partially explain the inconsistencies between visual and instrumental shade matching and the limitations of shade guides. Visual shade matching was driven by color differences with lower chroma and hue values. [ABSTRACT FROM AUTHOR]

To evaluate the influence of printing orientation on color and translucency of 3D printing restorative resins. Four 3D printing resin systems in the available shades (DFT-Detax Freeprint Temp- A1, A2,A3; FP-Formlabs Permanent Crown- A2,A3,B1,C2; FT- Formlabs Temporary CB- A2,A3,B1,C2; GCT-GC Temporary- Light, Medium) were evaluated. Three samples (10×10×1.2 mm) from each material were printed at two different printing orientations (0° and 90°) and polished to 1.00 ± 0,01 mm of thickness. Spectral reflectance was measured against black background using a calibrated spectroradiometer, CIE D65 standard illuminant and the 45°/0°geometry. Color and translucency differences were evaluated using CIEDE2000 metric (ΔE 00) and 50:50% perceptibility (PT 00 and TPT 00) and acceptability (AT 00 and TAT 00) thresholds. In general, color changes due to printing orientation at (0° and 90°) were mainly produced by ΔL* or ΔC*. ΔE 00 were above PT 00 for all DFT shades, FP-B1, FP-C2, FT-A2 and FT-B1. Only for DFT-1, ΔE 00 was above AT 00. ΔRTP 00 values were above TPT 00 for DFT-A1, DFT-A3, FP-B1 and FT-B1, but lower than TAT 00. The direction of the changes in translucency (ΔRTP 00) depends on the material and shade. The selection of building orientation (0° and 90°) for the 3D printed resins influence the visual color and translucency and therefore their esthetic appearance. These aspects should be considered when printing dental restorations using the evaluated materials. • Color and translucency of 3D printing resins is affected by printing orientation. • Differences in color (ΔE 00) and translucency (ΔRTP 00) may result visually perceptible. • Color differences are manly determined by lightness and chroma differences. • The direction of translucency differences depends on the material and shade. [ABSTRACT FROM AUTHOR]

Usually, dentin and enamel shades are layered in dental restorations with the purpose of mimicking the natural appearance of teeth. The main objective of this study was to develop and assess accuracy of a color-prediction method for both monolithic and layered dental resin-based composites with varying shades and under different illuminants. A total of 15 different shades of VITAPAN Excell, VITAPAN Dentine and VITA Physiodens as well as VITA Enamel of five different thicknesses (0.5–2.5 mm range) were used to manufacture monolithic and layered samples. A non-contact spectroradiometer with CIE 45 ∘ / 0 ∘ geometry was used to measure the color of all samples over a standard ceramic black background. Second-degree polynomial regression was used as predictive method for CIE-L*a*b* color coordinates. Performance of predictive models was tested using the CIEDE2000 total color difference formula ( Δ E 00 ), while accuracy was evaluated by comparative assessment of Δ E 00 with corresponding 50:50% acceptability ( A T 00 ) and perceptibly ( P T 00 ) thresholds for dentistry. A mean color difference between measured (real) and predicted color of Δ E 00 = 1.71 , with 62.86% of the color differences below A T 00 and 28.57% below P T 00 , was registered for monolithic samples. For bi-layered samples, the mean color difference was roughly Δ E 00 = 0.50 , with generally 100% and more than 85% of the estimations below A T 00 and P T 00 , respectively. The predictive method allowed highly accurate color estimations for both monolithic and layered dental resin-based composites with varying thicknesses and under different illuminations. These results could be useful to maximize the clinical success of dental restorations. [ABSTRACT FROM AUTHOR]

Objective: Color and optical properties are particularly crucial to mimic natural tooth. This scoping review aimed to present an overview of the literature published on color and optical properties of 3D printing restorative polymer‐based materials. The literature search was performed in MED‐LINE/Pubmed, Scopus and Web of Science. Materials and methods: The literature search was conducted in the three databases based on the question: "Are the optical properties and color adequately reported on polymer‐based 3D printing dental restorative materials studies?" with no restriction on year of publication. Data were reported and synthesized following PRISMA‐ScR statement. Results: Nine studies fit the inclusion criteria. Five studies focused on evaluating only color stability; three articles assessed the color stability along with mechanical and morphological properties and only one study compared color parameters of 3D printed to conventional polymers. Two studies evaluated translucency parameter and no study was found evaluating scattering, absorption, and transmittance. Conclusions: Color and optical properties of 3D printed polymers that can be used in restorative dentistry are not adequately evaluated and characterized. Future studies on the influence of experimental printing conditions should include these physical properties to assist on improving esthetics. Clinical significance: This review shows the scarce literature existing on color and optical properties of 3D printing restorative polymer‐based materials. These properties and their study are of outmost importance to create materials that mimic natural tooth to allow clinicians to obtain esthetically pleasant restorations. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the optical properties and the relative translucency parameter of Ceramill ZI White (3Y‐TZP) and Ceramill Zolid FX White (5Y‐PSZ) zirconia ceramic systems and compare them with those of the bovine dentin and enamel/dentin structures. Materials and Methods: 3Y‐TZP and 5Y‐PSZ zirconia ceramic systems were evaluated. A 0.5‐mm‐thick 3Y‐TZP (3Y‐NC.5), 0.5‐mm‐thick (5Y‐NC.5), and 1.4‐mm‐thick (5Y‐C.14) were used. A 0.5‐mm‐thick dentin specimens and 1.4‐mm‐thick enamel/dentin specimens (n = 5) were obtained from anterior bovine maxillary teeth. Scattering, absorption, transmittance, and albedo coefficient were calculated using Kubelka–Munk's model. Data were statistically analyzed using Kruskal–Wallis and Mann–Whitney tests (p < 0.001), and goodness‐of‐fit coefficient (GFC). Relative translucency parameter differences were evaluated using translucency thresholds. Results: Reflectance, scattering, absorption, and transmittance properties were wavelength dependent. Good matches (GFC ≥ 0.999) in spectral reflectance were observed between 0.5‐mm‐thick dentin and 1.4‐mm‐thick enamel/dentin, and 3Y‐NC.5 and 5Y‐NC.5. Scattering was the main optical extinction process during light interaction with zirconia and dental structures, as indicated by albedo coefficient. Translucency differences were acceptable only for 3Y‐NC.5 and the dentin structure, and 5Y‐C.14 and the enamel/dentin structure. Conclusions: Optical properties of 3Y‐TZP and 5Y‐PSZ dental zirconia differed from each other and from bovine dental structures. Nevertheless, 3Y‐TZP showed similar relative translucency parameter to bovine dentin. Clinical Significance: To achieve the best esthetic results in restorative dentistry, it is crucial for clinicians to know about the optical properties of 3Y‐TZP and 5Y‐PSZ and to be able to compare these properties with those of dental structures. [ABSTRACT FROM AUTHOR]

To evaluate the influence of thickness and printing angle on the optical properties of 3D-printed dental restorative resins. Four 3D printing resin systems were evaluated: DFT-Detax Freeprint Temp; FP- Formlabs Permanent Crown; FP- Formlabs Temporary CB; and GCT- GC Temporary-. Samples from each material were printed at 0° and 90°, and polished up to 0.5, 1.0, 1.5 and 2.0 mm thickness. Scattering (S), absorption (K) and albedo (a) coefficients, transmittance (T%), light reflectivity (RI) and infinite optical thickness (X ∞) were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal–Wallis¸ Mann-Whitney tests, and VAF coefficient. The spectral distribution on S, K, T%, RI, X ∞ were wavelength dependent. Although the spectral behaviors were similar for all the specimens evaluated, the values of S, K, T% and X ∞ presented significant differences between specimen thicknesses for all the materials used and for both printing orientations. Values for S and K increased, and T% and X ∞ decreased. Significant differences between 0° and 90° were found for RI values at 0.5 and 1.0 mm thick samples, for S and K at 2.0 mm, for X ∞ at 0.5 and 1.0 mm for DFT, and at 0.5 mm for FT. Optical properties of 3D-printed restorative resins vary between thicknesses, and could be affected by the building orientation. Therefore, these factors should be considered in order to improve the biomimetic potential of 3D-printed dental restorative resins. Understanding the optical behavior of the 3D-printed restorative resins is essential to optimize their clinical performance. • Spectral behavior of the scattering, absorption and transmittance are similar for all the 3D-printed dental resins evaluated. • Scattering is the most relevant attenuation phenomenon in 3D-printed dental resins. • Optical properties of 3D-printed dental resins are influenced by the thickness. • The printing angle may affect the optical properties of 3D-printed dental resins. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To design colorimetric and spectral models of gingival shade guides that adequately represent the color of human gingiva. Materials and Methods: A previously compiled database on the spectral reflectance of healthy keratinized gingiva was used for optimization. Coverage Error (CE) and Maximal Error (ME) were optimized using CIELAB and CIEDE2000 color difference formulas. A two‐phase process included an FCM algorithm and a nonlinear optimization. A t test was used to compare the performance of the different numbers of clusters/tabs in gingival shade guide models (α = .05). Results: CIELAB CE and ME for shade guide models with 3 to 6 clusters ranged from 3.1 to 3.9 (P = .028 for 3 vs. 4; and P = .033 for 5 vs. 6 cluster/tab comparison), while the corresponding CIEDE2000 range was from 2.1 to 2.8 (P < .001 for 3 vs. 4 tabs; P < .025 for 4 vs. 5; and P = 0.029 for 5 vs. 6 tab comparisons). The percentage of data points exhibiting a CIELAB color difference lower than the acceptability threshold ranged from 48.7% to 71.4%, and from 52.9% to 82.4%. for CIEDE2000. Conclusions: An increase in the number of clusters in the gingival shade guide models was associated with a decrease in coverage error (better match) to human gingiva. Gingival shade guide models with only 4 tabs provided a CIELAB and CIEDE2000 coverage error lower than the acceptability threshold for gingival color. Spectral clustering of human gingiva was determined to be valid. CIEDE2000 color difference formula outperformed the CIELAB formula in the optimization process. Clinical Significance: Providing a shade guide model with a small number of tabs and a coverage error lower than the 50:50% acceptability threshold would be an optimal solution for shade matching in dentistry. However, no actual gingival or tooth shade guide complies with this. The clustering method, with optimization of both Coverage Error and Maximal Error and spectral clustering that enables more reliable color formulation of cluster representatives of shade guide models, represents an advance when it comes to computer modeling in dentistry. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of thickness on color and translucency of a multi‐color polymer‐infiltrated ceramic‐network (PICN) material. Methods: Specimens of 0.5, 1.0, 1.5 mm thicknesses were obtained by sectioning VITA ENAMIC® multiColor (E‐MC) High Translucent CAD‐CAM blocks (1M1‐HT, 1M2‐HT, 2M2‐HT, 3M2‐HT, and 4M2‐HT). Spectral reflectance and color coordinates were measured on white and black backgrounds using a spectroradiometer, CIE D65 illuminant and CIE 45°/0° geometry. CIEDE2000 color and translucency differences (ΔE00 and ΔTP00) between thicknesses and adjacent layers were evaluated using their respective 50:50% perceptibility and acceptability thresholds (PT00 and AT00). Results: In general, ΔE00 between thicknesses for all shades and layers were above AT00 in general. Chroma decreased from cervical to incisal layers with statistically significant differences (p < 0.05), and ΔE00 between sequential layers were above PT00, for all shades and thicknesses. TP00 decreased from 0.5 to 1.5 mm and increased from cervical to incisal layers for all shades with statically significant translucency differences (p < 0.05). In general, for all thicknesses, TPT00 < ΔTP00 < TAT00 for sequential layers. Conclusions: The gradient in color and translucency of E‐MC PICN material was influenced by the thickness of the CAD‐CAM block. In addition, color and TP transition values between the layers depends on the thickness and shade. Clinical significance: The effect of thickness must be taken into account by dental technicians and dentists when CAD‐CAM multicolor PICN materials are used. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of layering strategy and substrate color on the masking ability of resin composites. Materials and Methods: A1‐shaded specimens from Charisma Diamond and Filtek Z350XT were produced using different layering strategies. Color measurements were made by a reflectance spectrophotometer over A2, C2, A3.5, C3, C4 substrates. Color differences were calculated and interpreted by the 50%:50% perceptibility and acceptability visual thresholds. Data was analyzed by Kruskal–Wallis and Dunn post hoc test. Chi‐square test was used to determine the association between masking ability, and independent variables. Results: Color differences were significantly lower on A2 and C2 in comparison with C4 for the majority of the layering strategies. Acceptable matches were observed on most of the combinations over A2. Moderately unacceptable mismatches were observed in most of the combinations over C2 and A3.5. Clearly unacceptable mismatches were observed on the C3 and C4. The ΔE00 color shifts were predominantly influenced by ΔL00 for all layering strategies and substrate colors. Conclusion: Masking ability was affected by the layering strategy and substrate color. Acceptable masking was associated with A2 and C2, and with layering strategy composed of 0.5 mm enamel opacity and 1.0 mm dentin opacity thicknesses, using the Filtek Z350XT. Clinical Significance: Resin composites—shade A1—applied by different layering strategies with a final thickness of 1.5 mm were able to mask mild and moderately discolored substrates. Severely discolored substrates were not masked effectively. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The purpose of this study was to determine the optical properties, color and translucency, of the new silorane-based resin composite and to compare it to universal dimethacrylate-based composites. Methods: Six dimethacrylate-based resin composites and one silorane-based resin composite (all A2 shade) were studied. Color of non-polymerized and polymerized composites was measured against white and black backgrounds using a spectroradiometer. Changes in color (ΔE*ab), translucency (ΔTP) and color coordinates (ΔL*, Δa* and Δb*) were calculated for each resin composite. Results were evaluated using a one-way ANOVA, a Tukey''s test and a t-test. Results: The polymerization-dependent ΔE*ab ranged from 4.7 to 9.1, with the smallest difference for the silorane-based resin composite. The color changes of silorane-based composite were due to the changes of coordinates Δa* and Δb*. However, for the dimethacrylate-based composites, the color changes mainly originated by ΔL*and Δb*. The silorane composite exhibited the smallest TP values. Tukey''s test confirmed significant statistical differences (p <0.05) between mean TP values of Filtek Silorane and each brand of dimethacrylate-based composites before and after polymerization. Conclusions: The new silorane-based restorative system showed different optical properties compared to clinically successful dimethacrylate composites. The silorane composite exhibited better polymerization-dependent chromatic stability, and a lower translucency compared to other tested products. [Copyright &y& Elsevier]

Abstract: Objectives: The objective of the study was to determine the perceptibility and acceptability thresholds for dental ceramics using CIEDE2000 (ΔE 00) and CIELAB color difference formulas and a novel TSK Fuzzy Approximation. Methods: A 13-observer panel performed independent observations of perceptibility and acceptability judgments on 105 pairs of ceramic discs (14mm in diameter and 3mm thick). Color differences of the disc pairs were calculated using both color difference formulas (ΔE 00 ranged from 0.10 to 9.91). Two fitting procedures were used: S-shaped curve and TSK Fuzzy Approximation. For both procedures, from the resultant fitting curves, the 95% confidence intervals were estimated and the 50:50% thresholds were calculated (50% positive and 50% negative answers). Results: With the S-shaped fitting procedure, a 50:50% acceptability threshold was found to be ΔE 00 =2.25 (r 2 =0.88) and (r 2 =0.85). Corresponding values with a TSK Fuzzy Approximation were ΔE 00 =2.23 (r 2 =0.89) and (r 2 =0.86). The perceptibility thresholds for fitted S-shape curves were ΔE 00 =1.30 (r 2 =0.74) and (r 2 =0.70) and ΔE 00 =1.25 (r 2 =0.75), and (r 2 =0.71) for the TSK Fuzzy Approximation. The ΔL′, ΔC′, ΔH′ values corresponding to a 50% acceptability threshold were ΔL′=2.44, ΔC′=3.15 and ΔH′=3.24 respectively. Conclusions: The CIEDE2000 color difference formula provided a better fit than CIELAB formula in the evaluation of color difference thresholds of dental ceramics. There was a statistically significant difference between perceptibility and acceptability thresholds for dental ceramics. The TSK Fuzzy Approximation has been proved to be a reliable alternative approach for the color threshold calculation procedure. [Copyright &y& Elsevier]

Objective: Evaluate the effectiveness and color stability of bleaching techniques on blood‐stained teeth. Material and Methods: The teeth were stained by blood and allocated to groups: walking bleach, inside/outside, and in‐office bleaching. L*, a*, b*, C*, h° color coordinates were measured using a clinical spectrophotometer at baseline, weekly (T1‐T2‐T3), and at 1‐week (T4), 6‐months (T5), and 1‐year (T6) follow‐up evaluations. ΔEab*, ΔE00, and ΔWID were calculated between sequential evaluation timepoints and between baseline and each evaluation timepoint. Color coordinates and WID differences in each timepoint and technique were analyzed by Wilcoxon Signed Rank, Kruskal‐Wallis and Mann–Whitney U test, respectively. ΔEab*, ΔE00, and ΔWID were interpreted by color visual thresholds. Results: The techniques presented a significant increase in L* and WID and, a significant decrease in a* and b* until the completion of treatments. Statistical differences between the techniques for a*, b* and WID were observed from T1 until T3. All techniques demonstrated excellent effectiveness for ΔEab*, ΔE00, and ΔWID between baseline and each evaluation and follow‐up timepoints. However, at T6, it was possible to identify a rebound effect for all techniques. Conclusions: All bleaching techniques presented excellent effectiveness. The stability of the whitening produced was maintained for 6 months. Clinical Significance: Effective whitening of blood‐stained teeth was achieved using walking bleach (sodium perborate), inside/outside (hydrogen peroxide ‐ 7.5%) and in‐office techniques (hydrogen peroxide ‐ 35%). The bleaching techniques were effective after the completion of the treatments. A slight rebound was observed at 1 year follow‐up. [ABSTRACT FROM AUTHOR]

Objective: To evaluate color, lightness, chroma, hue, and translucency adjustment potential of resin composites using CIEDE2000 color difference formula. Methods: Three resin composites (Filtek Universal, Harmonize, and Omnichroma) were tested. Two types of specimens were prepared: an outer base shade with an inner hole filled with test shades and single‐composite specimens of all shades. Spectrorradiometric reflectances measurements and subsequent CIELAB color coordinates and translucency parameter (TP) were performed. Color (CAP00), lightness, chroma, hue, and translucency (TAP00) adjustment potential using CIEDE2000 color difference were computed. Color and transparency differences among composite materials and shades were statistically tested (P < 0.05). Results: Positive CAP00 and TAP00 values were found for majority of tested materials. CAP00 values ranged from −0.14 to 0.89, with the highest values found for Omnichroma (>0.75 in all cases). TAP00 values ranged from −0.06 to 0.86 with significant translucency differences among dual and single specimens. Omnichroma exhibited the highest adjustment potential for all color dimensions studied. Conclusions: Lightness, hue, chroma, and translucency adjustment potential have been introduced using CIEDE2000 color difference formula, and have shown their usefulness to evaluate blending effect in dentistry. Color coordinates and translucency adjustment potential were dependent on dental material. Omnichroma exhibited the most pronounced blending effect. Clinical significance: Resin composites with increased color and translucency adjustment may simplify shade selection, making this process easier and less time consuming. Furthermore, these materials might facilitate challenging and complex color matching situations. [ABSTRACT FROM AUTHOR]

Objective: Evaluate the masking ability of bleach‐shade resin composites applied by multilayering techniques over colored substrates. Materials and methods: Disc‐shaped specimens were fabricated from bleach‐shade resin composites using different multilayering techniques. Substrates were produced in opaque ceramic discs simulating colored substrates (A2, A3, A3.5, C2, C3, C4) and a bleached tooth (0M1). Color coordinates were obtained using a reflectance spectrophotometer. Color difference was calculated by CIEDE2000 using coordinates of 0 M1 ceramic as standard reference. Data were analyzed by one‐way ANOVA and Tukey's post‐hoc test (p ≤ 0.05). Masking ability interpretation was based on perceptibility and acceptability thresholds. Results: All combinations presented ΔE00 above the acceptable threshold (ΔE00>1.8), ranging from 2.49 to 7.42, regardless of the restorative system, multilayering strategy or substrate color. Multilayering combinations placed over A2, A3 and A3.5 were moderately (1.8<ΔE00≤3.6) and clearly unacceptable (3.6<ΔE00≤5.4), combinations associated with C2, C3 and C4 were clearly unacceptable and, extremely unacceptable (ΔE00>5.4). Lower ΔE00 was observed for combinations with 0.5 mm extra white enamel layer (2.49), or 1.0 mm white dentin layer (2.69), over A2 and A3.5 substrates. Lightness difference showed the greatest contribution to ΔE00. Conclusions: Bleach‐shade resin composite systems applied by the multilayering technique were not able to ensure effective masking ability. Clinical significance: Bleach‐shade resin composites applied with different combinations of the multilayering technique were not effective in masking colored substrates. Alternative strategies, techniques and dental materials should be explored to obtain acceptable masking. [ABSTRACT FROM AUTHOR]

• One-shaded resin-based composites show lower spectral scattering and absorbance than the group-shaded resin-based composite. • One-shaded resin-based composites present higher spectral transmittance than the group-shaded resin-based composite. • One-shaded resin-based composites are more translucent than the group-shaded resin-based composite. • Value of opalescence parameter and the effect of thickness on opalescence are material-dependents. To evaluate optical properties, and translucency and opalescence parameters of one-shaded resin-based composites. Three one-shaded resin composites (OM — Omnichroma; VP — Venus Pearl; and VD — Venus Diamond) and a group-shaded resin composite (FU- Filtek Universal A2) were used. Three composite discs from each material were fabricated for each of the following thickness: 0.5, 1.0 and 2.0 mm. Diffuse reflectance was measured against white and black backgrounds using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry. Translucency parameter (TP) was calculated using Δ E a b * and Δ E 00. Scattering (S) and absorption (K) coefficients and transmittance (T%) were calculated using Kubelka–Munk's equations, and a reflection spectrophotometer was used to measure the opalescence parameter (OP). Data was statistically analyzed using Kruskal–Wallis, Mann–Whitney tests, and VAF coefficient. Spectral distributions of S, K and T were wavelength dependent, showing significant differences between materials of the same thickness and for different thicknesses of the same material (p < 0.001). OM showed the greatest translucency values for all thicknesses. Translucency decreased as thickness increased with statistically significant differences (p < 0.005). Values of ΔTP ab and ΔTP 00 between thicknesses were above of translucency thresholds for all materials. VP and VD showed the lowest OP values. One-shaded resin-based composites showed different optical behavior than the group-shaded resin-based composite. Understanding the optical behavior of the one-shaded resin-based composites is essential to optimize their clinical performance. [ABSTRACT FROM AUTHOR]

• Modern LED sources produce changes in color and whiteness of natural teeth. • Some LED illuminants recommended by CIE generate perceptible color shifts. • LED illuminants produce color shifts in very different directions of color space. • Color differences for pairs of teeth are almost independent of illuminants. • Whiteness differences for pairs of teeth are almost independent of illuminants. To evaluate color and whiteness changes of natural teeth under nine white LED illuminants recently proposed by CIE. From spectral reflectance factors of 36 caries-free upper central incisors, corresponding colors under illuminant D65 and CIE 1931 standard colorimetric observer were computed for all tested illuminants, using the chromatic adaptation transform CAT16. Color differences (CIELAB and CIEDE2000 units) and whiteness (W I D and W I O indices) from teeth illuminated by CIE standard illuminants (D65 and A) and white LED illuminants were calculated. The appearance of 630 pairs of teeth under all illuminants was also evaluated. Color gamuts from 36 teeth under tested illuminants showed similar volume and shape in CIELAB color space, but their centers of gravity changed in many different directions with respect to colors under D65 or A illuminants: Considering colors under D65/A, color shifts produced by white LED illuminants were in the ranges 2.0–8.6/1.1–7.0 CIELAB units (1.4–8.2/0.6–6.8 CIEDE2000 units). Average W I D and W I O values for the 36 teeth under different illuminants ranged from −5.8 to +19.3 and from −7.7 to +11.1, respectively. Considering 630 pairs of teeth, average color differences (mainly lightness differences) were below 0.5 CIELAB units (0.3 CIEDE2000 units), and average whiteness differences ranged from 8.1 to 10.7 for W I D (23.4–25.1 for W I O). Using CIE LED illuminants, most changes in color and whiteness for individual teeth were above typical threshold values of perceptibility and acceptability in dentistry. However, considering pairs of teeth, the average color and whiteness differences under all tested illuminants were very similar. [ABSTRACT FROM AUTHOR]

• Exist perceptible differences in color and translucency among layers of material. • Luminosity and saturation values decreases towards the incisal layer for all shades. • Translucency increases from cervical to incisal layers for all shades evaluated. • Shade of underlying tissues should be considered when selecting this material. To evaluate color, translucency parameter and optical properties (scattering (S), absorption (K) and transmittance (T)) of a multi-color polymer-infiltrated ceramic-network (PICN) material. Samples of shades 1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT from VITA ENAMIC® multiColor (E-MC) High Translucent were fabricated (n = 3). CAD-CAM blocks were cut and polished to 1.00 ± 0.01 mm of thickness. Diffuse reflectance and color coordinates were measured against white and black backgrounds, using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry. Color and translucency differences were evaluated using 50:50% perceptibility (PT and TPT) and 50:50% acceptability (AT and TAT) thresholds. S and K coefficients and T were calculated using Kubelka–Munk's equations. Data was statistically analyzed using Kruskal–Wallis, Mann–Whitney tests, and VAF coefficient. Mean C* and b* values increased from incisal to cervical layers with statistically significant differences (p < 0.05). In general, ΔE 00 between sequential layers were above PT for all shades. In addition, translucency parameter (TP) increased from cervical to incisal and ΔTP 00 values were greater than TPT 00 and lower than TAT 00 between all sequential layers. Layers from all shades showed similar spectral behavior for S (97.4% ≤ VAF), K (85.0% ≤ VAF) coefficients and T (95.3% ≤ VAF). However, these values presented significant differences (p < 0.05) from cervical to incisal layers. The gradient in color and translucency of this novel CAD-CAM multi-color PICN material can assist dental technicians and dentists to reach greater esthetics than the pre-existing CAD-CAM monolithicmaterials. [ABSTRACT FROM AUTHOR]

Objectives To compare visual and instrumental shade matching performances using two shade guides and three color difference formulas. Methods One hundred dental students (DS) volunteers (35 males and 65 females) with normal color vision participated in the study. The spectral reflectance of 4 extracted human upper central incisors (UCI) and shade tabs from Vita Classical (VC) and Vita Toothguide 3D-Master (3D) shade guides were measured using a spectroradiometer (SP) under D65 illuminant (diffuse/0° geometry) inside a viewing booth with a gray background. Color coordinates (CIE L *, a *, b *, C * and h °) were calculated according to CIE D65 illuminant and CIE 2° Standard Observer. Color coordinates of UCI were also evaluated using a dental spectrophotometer (EA – Easyshade Advance). DS used VC and 3D to visually select the best shade match for each UCI, under same experimental conditions used for the SP evaluation. Three color difference metrics (CIELAB, CIEDE2000(1:1:1) and CIEDE2000(2:1:1)) were used to calculate the best instrumental shade matching based on minimum color difference. Results The agreement between visual and instrumental shade matching was greater using SP (25–75%) than EA (0–25%). The percentage of best match for the visual assessment was more consistent using VC (23–55%) than 3D (19–34%). Considering the best performance (using SP and VC), the CIEDE2000(2:1:1) color difference formula showed the best estimate to the visual perception from DS. Significance Within the limitations of this study, combining the use of SP, CIEDE2000(2:1:1) and Vita Classical shade guide most closely represented the visual perception of DS. Instrumental shade determination should be accompanied by experienced human visual assessment. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate colour differences between (1) CAD-CAM ceramic systems considering shades A1, A2 and A3 and the corresponding nominal shade of VC (Vita Classical shade guide) and (2) shades A1-A2, A2-A3 and A1, A2 and A3 within the same ceramic system. Methods: Samples of shades A1, A2 and A3 were fabricated (n = 5) from CAD-CAM ceramic blocks (IPS e.max® CAD LT and HT, IPS Empress® CAD LT and HT, ParadigmTM C, and VITABLOCS® Mark II) and polished to 1.0 ± 0.01 mm in thickness. Spectral reflectance and colour coordinates were measured using a spectroradiometer inside a viewing booth using the CIE D65 illuminant and the d/0° geometry. Spectral reflectance curves were compared using VAF coefficient and were statistically analyzed using Kruskal-Wallis and the Mann- Whitney U test (α = 0.05). Colour coordinates were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α = 0.001). All colour differences (ΔE* ab and ΔE00) were analyzed through comparisons with the PT - perceptibility and AT - acceptability thresholds for dental ceramics. Results: DE between ceramic systems and its corresponding shade ranged from 6.32 to 13.42 (ΔE* ab) and 4.48 to 9.30 (ΔE00). DE between shades A1-A2, A2-A3 and A1, A2 and A3 ranged, respectively, 1.93-4.82, 1.22-5.59 and 3.63-8.84 (ΔE* ab); 1.54-3.87, 1.03-3.90 and 2.95-6.51 (ΔE00). Conclusions: Considering the corresponding nominal shade from VC, none of the ceramic systems showed colour differences below the AT. In addition, some ceramic systems showed colour differences below AT (shades A1-A2 and A2-A3) and below PT (shades A2-A3). Clinical significance: Careful adjustments should be made to the final shade of CAD-CAM ceramic restorations to reach a clinically acceptable shade match. [ABSTRACT FROM AUTHOR]

Objective: To assess dentine caries removal effectiveness (CRE) and minimal invasiveness potential (MIP) of carbide and polymer burs. Methods: Sectioned carious molars were photographed. Digital images were taken, before and after caries removal, using a Digital Single Lens Reflex camera. The following regions of interest were measured using visual criteria: Residual Infected Dentine (RI), Residual Affected Dentine (RA), Removal Sound Dentine (RA), Prepared Cavity (PC) and Removed Sound Dentine (RS). CRE was determined on basis of: relative residual infected dentine (RI/ II), relative residual carious-affected dentine (RA/IA) and total relative residual dentine (RI + RA/II - IA). MIP was determined on basis of: infected dentine cavity size (PC/II), total relative cavity size (PC/II + IA), and corrected relative cavity size (PC - RS/II + IA). Results: The polymer bur showed the highest preservation of carious-affected dentine after excavation, when the RA/IA ratio was studied. Both kind of burs showed similar values after assessing the RI/II and RI + RA/II -- IA ratios. The infected dentine relative cavity size (PC/II) was higher when the carbide bur was used. Both burs attained similar PC/II + IA and PC - RS/II + IA ratios. Conclusions: Polymer burs accomplished the concept of minimal-invasive dentistry, showing its self-limiting ability. The minimal-invasiveness potential showed that carbide burs resulted in the worst compromise between effective and selective infected-caries removal. [ABSTRACT FROM AUTHOR]

Objectives To evaluate relevant optical properties of esthetic direct restorative materials focusing on whitened and translucent shades. Methods Enamel (E), body (B), dentin (D), translucent (T) and whitened (Wh) shades for E (WhE) and B (WhB) from a restorative system (Filtek Supreme XTE, 3M ESPE) were evaluated. Samples (1 mm thick) were prepared. Spectral reflectance ( R %) and color coordinates ( L *, a *, b *, C * and h °) were measured against black and white backgrounds, using a spectroradiometer, in a viewing booth, with CIE D65 illuminant and d /0° geometry. Scattering ( S ) and absorption ( K ) coefficients and transmittance ( T %) were calculated using Kubelka–Munk's equations. Translucency (TP) and opalescence (OP) parameters and whiteness index ( W *) were obtained from differences of CIELAB color coordinates. R %, S , K and T % curves from all shades were compared using VAF (Variance Accounting For) coefficient with Cauchy–Schwarz inequality. Color coordinates and optical parameters were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction ( α = 0.0007). Results Spectral behavior of R % and S were different for T shades. In addition, T shades showed the lowest R %, S and K values, as well as the highest T %, TP an OP values. In most cases, WhB shades showed different color and optical properties (including TP and W *) than their corresponding B shades. WhE shades showed similar mean W * values and higher mean T % and TP values than E shades. Significance When using whitened or translucent composites, the final color is influenced not only by the intraoral background but also by the color and optical properties of multilayers used in the esthetic restoration. [ABSTRACT FROM AUTHOR]