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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]

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]

(1) Background: This study aimed to determine the effect of repeated pre-polymerization heating on the color and translucency of a one-shaded resin-based composite and to evaluate whether the heating cycles affect its color stability. (2) Methods: Fifty-six samples of 1-mm thickness were fabricated from Omnichroma (OM) after applying different heating cycles (for one, five, and ten times at 45 °C) before polymerization (n = 14/group) and afterwards were stained with a yellow dye solution. CIE L*, a*, b*, C*, h° coordinates were recorded, and color differences, whiteness, and translucency were calculated, before and after staining. (3) Results: Heating cycles significantly influenced the color coordinates, WID00, and TP00 of OM being higher after one heating cycle and decreasing as the number of heating cycles increased. The color coordinates, WID, and TP00 after staining significantly differed for each group. The color and whiteness differences calculated after staining exceeded the acceptability thresholds for all groups. The color and whiteness variations after staining were clinically unacceptable. (4) Conclusions: Repeated pre-polymerization heating induces a clinically acceptable color and translucency change to OM. Although the color changes resulting after staining are clinically unacceptable, increasing the number of heating cycles up to ten times slightly reduces the color differences. [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]

The aim of this study was to evaluate color inconstancy of dental ceramics under the white light-emitting diode illuminants recently proposed by the CIE. From spectral reflectance factors of 18 dental ceramics (VST, NSP, and IEC; shades A1, A2, A3, A3.5, B2, and C2), the corresponding colors under illuminant D65 and CIE 1931 Standard Colorimetric Observer were computed for all samples, using the chromatic adaptation transform CIECAT16. CIEDE2000 color differences between dental ceramics illuminated by CIE D65 standard illuminant and different white LED illuminants were calculated. Perceptibility and acceptability thresholds (PT00 and AP00) in dental ceramics were used to analyze color changes. Color gamut size was within the same range for all illuminants and for all ceramics, since MCDM computed values were 4.1–4.4 for VST, 4.0–4.2 for NSP, and 4.3–4.6 for IEC. For all ceramics and shades, the color inconstancies were higher than 50:50% PT00 and, in general, lower than 50:50% AT00. The effect of CIE-proposed LED illuminants on dental ceramic is perceptible and slightly lower than on natural teeth. Dental clinicians should consider these lighting effects on the visual appearance of dental ceramics. [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: 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]

A full comprehension of colorimetric relationships within and between teeth is key for aesthetic success of a dental restoration. In this sense, hyperspectral imaging can provide point-wise reliable measurements of the tooth surface, which can serve for this purpose. The aim of this study was to use a hyperspectral imaging system for the colorimetric characterization of 4 in-vivo maxillary anterior teeth and to cross-check the results with similar studies carried out with other measuring systems in order to validate the proposed capturing protocol. Hyperspectral reflectance images (Specim IQ), of the upper central (UCI) and lateral incisors (ULI), were captured on 30 participants. CIE-L*a*b* values were calculated for the incisal (I), middle (M) and cervical (C) third of each target tooth. Δ E a b * and Δ E 00 total color differences were computed between different tooth areas and adjacent teeth, and evaluated according to the perceptibility (PT) and acceptability (AT) thresholds for dentistry. Non-perceptible color differences were found between UCIs and ULIs. Mean color differences between UCI and ULI exceeded AT ( Δ E a b * = 7.39–7.42; Δ E 00 = 5.71–5.74) in all cases. Large chromatic variations between I, M and C areas of the same tooth were registered ( Δ E a b * = 5.01–6.07 and Δ E 00 = 4.07–5.03; Δ E a b * = 5.80–8.16 and Δ E 00 = 4.37–5.15; and Δ E a b * = 5.42–5.92 and Δ E 00 = 3.87–4.16 between C and M, C and I and M and I, respectively). The use of a hyperspectral camera has proven to be a reliable and effective method for color evaluation of in-vivo natural teeth. [ABSTRACT FROM AUTHOR]

Objectives: The study aimed to compare the color of monolithic and layered zirconia crowns fabricated using different brands in the cervical, middle, and incisal areas. Materials and Methods: A total of 45 crowns were fabricated from three brands (Katana, Nacera, Cercon) using three methods (monolithic = ML (n=5), cut‐back + enamel = BL (n=5), cut‐back + dentin + enamel = TL (n=5)). CIE L*, a* b*, C*, h° color coordinates were recorded with a dental spectrophotometer in cervical, middle, and incisal areas. Color differences between manufacturing techniques, tooth areas, and brands were calculated using the CIEDE2000(1:1:1) formula, and the values were compared to the perceptibility (PT00) and acceptability thresholds (AT00). Comparisons between color coordinates were analyzed statistically (Kruskal‐Wallis and Mann‐Whitney U tests, p < 0.001). Results: Significant differences were found between CIE L*, a*, b*, C*, h° coordinates of the zirconia crowns (p < 0.001), generally. The lowest color differences were obtained between BL and TL crowns in cervical and middle areas. Color differences between cervical and middle areas were mostly below PT00. An acceptable color difference was found between Katana and Cercon crowns. Conclusions: The manufacturing technique and the brand influenced the color of zirconia crowns. Also, the color of the crowns varied from cervical to incisal. Clinical Significance: Reproducing the optical properties of teeth with ceramic crowns might be challenging, given the differences in the internal configuration of the enamel and dentine, as well as their complex behavior when interacting with light. When deciding whether to fabricate a monolithic crown in translucent zirconia or improve its appearance by layering with more translucent glass–ceramic, the clinicians and dental technicians must be aware of these procedures' effect on the final color of the restorations. [ABSTRACT FROM AUTHOR]

The most recent generation of bioengineered human skin allows for the efficient treatment of patients with severe skin defects. Despite UV sunlight can seriously affect human skin, the optical behavior in the UV range of skin models is still unexplored. In the present study, absorbance and transmittance of the UGRSKIN bioartificial skin substitute generated with human skin cells combined with fibrin-agarose biomaterials were evaluated for: UV-C (200–280 nm), -B (280–315 nm), and -A (315–400 nm) spectral range after 7, 14, 21 and 28 days of ex vivo development. The epidermis of the bioartificial skin substitute was able to mature and differentiate in a time-dependent manner, expressing relevant molecules able to absorb most of the incoming UV radiation. Absorbance spectral behavior of the skin substitutes showed similar patterns to control native skin (VAF > 99.4%), with values 0.85–0.90 times lower than control values at 7 and 14- days and 1.05–1.10 times the control values at 21- and 28-days. UV absorbance increased, and UV transmission decreased with culture time, and comparable results to the control were found at 21 and 28 days. These findings support the use of samples corresponding to 21 or 28 days of development for clinical purposes due to their higher histological similarities with native skin, but also because of their absorbance of UV radiation. [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]

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]

Objective: To analyze translucency variations among four different contemporary esthetic ceramic systems having different shades and thicknesses. Material and Methods: Ceramic specimens having different shades and translucencies were tested: leucite reinforced glass–ceramic (ECAD), conventional feldspathic ceramic (Noritake), zirconia reinforced lithium silicate glass–ceramic (Suprinity) and hybrid ceramic (Enamic). Specimens of 0.6, 0.9, 1.2, 1.5 and 2.0‐mm thickness (n = 3/group, 615 total) were prepared. Translucency (TP) and Relative Translucency (RTP) Parameters were calculated from spectroradiometric color readings. Effects of shade and thickness for a given system were statistically analyzed using MANOVA and Tukey post‐hoc multiple comparisons tests. Translucency variations were assessed comparatively with literature‐based perceptibility and acceptability thresholds. Results: TP/RTP values of all ceramic materials decreased with increasing thickness. The most translucent specimens were 0.6‐mm thick ECAD HT‐A3.5 (TP = 31.99) and ECAD HT‐C2 (RTP = 23.75), while the least translucent was 2‐mm thick Enamic T‐3 M2 (TP = 7.27; RTP = 4.79). Thickness and material type significantly influenced translucency (p < 0.001). Noritake and ECAD LT showed similar translucency values, as well as Suprinity HT and ECAD LT. Conclusions: For ceramic restorations thicker than 0.9‐mm, any thickness increase of 0.3–0.5 mm produces a perceptible but clinically acceptable translucency variation. Increases in thickness larger than 0.6‐mm will result in an unacceptable translucency shift. Dental practitioners need to recognize key factors that influence translucency of ceramic restorations in order to choose the optimal material, shade, translucency, and thickness suitable for different clinical scenarios. While shade plays a minor role in translucency variation, ceramic type and restoration thickness significantly affect overall translucency. [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]

To assess accuracy of reflectance reconstruction and color estimation of different dental materials with varying thicknesses using Principal Component Analysis (PCA). A1, A2, A3, A3.5, B2, C2 and D2 shades and 5 thicknesses (within 0.5–2.5 mm range) of Vita Suprinity (VS-PC) and Vitapan Dentine (VD), were used. Reflectance measurements were performed over black background using a non-contact spectroradiometer with CIE 45∘∕0∘ geometry. A PCA based algorithm was proposed to reconstruct spectral data and color of samples, using both extrapolation and interpolation approaches. Root Mean Square Error (RMSE), Goodness of Fit (GFC), correlation coefficient (R 2) as well as Δ E 00 with corresponding 50:50% acceptability and perceptibly thresholds (AT and PT) were used as performance assessment. The interpolation approach provided an average RMSE = 0.01 and GFC > 0.999 when comparing predicted and measured spectral reflectances for both materials, while for the extrapolation approach RMSE = 0.02 and GFC > 0.999. Interpolation approach also resulted in lower overall mean color difference Δ E 00 = 0.8 (Δ E 00 = 0.9 for VS-PC and Δ E 00 = 0.7 for VD), while using extrapolation approach resulted in higher overall mean color difference Δ E 00 = 1.6, although below the AT (Δ E 00 = 1.8 for VS-PC and Δ E 00 = 1.5 for VD). Correlation values between predicted and measured spectral reflectances of R 2 = 0.987 and R 2 = 0.993 were globally obtained for VS-PC and VD, respectively. The proposed PCA-based algorithm is able to efficiently predict reflectance spectrum and color of monolithic samples of different dental materials with varying thickness. It can be used to optimize dental materials manufacturing processes and to improve chromatic accuracy of clinical dental restorations. • Reflectance data of dental materials can be estimated by PCA-based algorithms. • Thickness and shade variations do not affect the accuracy of the estimation. • Predicted - measured color differences are generally lower than AT. [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]

Objective: To determine the visual 50:50% perceptibility and acceptability CIEDE2000 lightness, chroma and hue human gingiva thresholds., Methods: A psychophysical experiment based on visual assessments of simulated images of human gingiva on a calibrated display was performed. A 20-obsever panel (dentists and laypersons; n=10) evaluated three subsets of simulated human gingiva: lightness subset (|ΔL ' /ΔE 00 |≥ 0.98); chroma subset (|ΔC ' /ΔE 00 |≥ 0.98) and hue subset (|ΔH ' /ΔE 00 |≥ 0.96) using ΔE 00 < 5 units. A Takagi-Sugeno-Kang (TSK) Fuzzy Approximation model was used as fitting procedure, and 50:50% perceptibility threshold (PT) and acceptability threshold (AT) were calculated. Data was statistically analyzed using t-test (p ≤ 0.05)., Results: The 50:50% PT were ΔL' = 0.74 (95% confidence interval (CI) 0.39-1.09); ΔC' = 1.10 (95% CI 0.57-1.46); ΔH' = 2.40 (95% CI 1.66->3.85). The 50:50% AT were ΔL' = 2.57 (95% CI 2.00-3.06); ΔC' = 2.70 (95% CI 2.19-3.38). AT ΔH' may be considered no computable. PT values were statistically significant among the three metric differences (p ≤ 0.05). No difference was found between observers for PT values., Conclusions: Statistically differences in perceptual limit were found among hue, lightness and chroma for human gingiva. Thus, the observers seem to show lower sensitivity for changes in hue (ΔH ' ) than in chroma (ΔC ' ) and in lightness (ΔL ' ) in the gingiva color space., Clinical Significance: PT and AT for lightness, chroma and hue specific for human gingiva should be used when evaluating natural gingiva, pink gingival shade guides or pink materials, since the thresholds of perception and acceptability for teeth are not suitable., (Copyright © 2022. Published by Elsevier Ltd.)

There is scarce information on the colorimetric behavior of monolithic and layered zirconia crowns in combination with various abutment colors. This study evaluated the masking ability on discolored substrates of monolithic and layered zirconia crowns. Anterior crowns were fabricated using 3Y-TZP zirconia and layering ceramic and divided into three groups: monolithic (ML), bi-layer (BL), and tri-layer (TL). The crowns were placed over eleven substrates (ND1-ND9, zirconia, metal), and CIE L*, a*, b*, C*, and h° color coordinates were measured in the cervical, middle, and incisal areas with a spectrophotometer. Masking ability was calculated using the color difference formula, and values were interpreted according to the perceptibility and acceptability thresholds. Data were analyzed statistically (α = 0.001). The L* coordinate was not significantly different between BL and TL crowns, regardless of the measurement area or substrate (p ≥ 0.001). In the middle area, the L* coordinate of the ML group was statistically different from the BL and TL groups only for zirconia and metal substrates, while in the incisal area, only for ND7 and metal substrates. The a* coordinate was significantly different between the ML and layered crowns for all measurement areas and substrates (except zirconia). The b* and C* coordinates differed significantly between the groups only in the cervical area (p < 0.001). The ML crown had better masking ability than the BL and TL crowns. However, the color differences for ML crowns were below the acceptability threshold for ND2, ND3, and ND7 substrates in the cervical and middle areas and below perceptibility threshold only for the incisal area. The lowest masking ability of the crowns was found for ND9 and metal substrates in all measurement areas.

Objective: To determine in-vivo chromatic and whiteness changes produced by short-term dental dehydration., Methods: Spectral reflectance of 452 upper incisors (226 centrals and 226 laterals) of 113 participants were measured using a spectroradiometer at baseline and after short-term dehydration (minutes 2, 4, 6, 8 and 10). CIE L*a*b* color coordinates (L*, a*, b*, C* ab and h ab ) and whiteness index for dentistry (WI D ) were calculated. Color differences (ΔE 00 , ΔE ab * ) and whiteness differences (ΔWI D ) were computed and interpreted based on their respective 50:50% perceptibility (PT) and acceptability thresholds (AT). Statistical analysis was performed using the related samples Wilcoxon signed-rank test., Results: L* showed an increasing trend with dehydration, while a*, b*, C* ab and h ab have a decreasing tendency. All chromatic coordinates showed statistically significant differences (p < 0.003) at each interval of dehydration compared with baseline, except a* for all teeth. For ΔE 00 and ΔE ab * values were higher than PT after 2 min of teeth dehydration and higher than AT after 6 and 8 min, respectively. The percentage of teeth exceeding corresponding PT was higher than 50% after 2 min. WI D index increased with dehydration time, while whiteness differences were clinically perceptible after 4 min. Statistically significant differences were found for WI D between all dehydration intervals (except 8-10 min). The percentage of teeth exceeding whiteness PT was higher than 50% after 6 min of teeth dehydration., Conclusions: Short-term dental dehydration produces clinically unacceptable changes in tooth color and clinically perceptible increase in tooth whiteness level., Clinical Significance: Clinical shade matching must be done within the first two minutes of any clinical procedure that requires precise chromatic determination but implies a risk of tooth dehydration., (Copyright © 2020 Elsevier Ltd. All rights reserved.)