• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.23.1-23.11
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• 2021

Objectives: This study assessed the reliability of digital color measurements using images of resin composite specimens captured with a cellphone. Materials and Methods: The reference color of cylindrical specimens built-up with the use of resin composite (shades A1, A2, A3, and A4) was measured with a portable spectrophotometer (CIELab). Images of the specimens were obtained individually or pairwise (compared shades in the same photograph) under standardized parameters. The color of the specimens was measured in the images using RGB system and converted to CIELab system using image processing software. Whiteness index (WI_D) and color differences (ΔE₀₀) were calculated for each color measurement method. For the cellphone, the ΔE₀₀ was calculated between the pairs of shades in separate images and in the same image. Data were analyzed using 2-way repeated-measures analysis of variance (α = 0.05). Linear regression models were used to predict the reference ΔE₀₀ values of those calculated using color measured in the images. Results: Images captured with the cellphone resulted in different WI_D values from the spectrophotometer only for shades A3 and A4. No difference to the reference ΔE₀₀ was observed when individual images were used. In general, a similar ranking of ΔE₀₀ among resin composite shades was observed for all methods. Stronger correlation coefficients with the reference ΔE₀₀ were observed using individual than pairwise images. Conclusions: This study showed that the use of cellphone images to measure the color difference seems to be a feasible alternative providing outcomes similar to those obtained with the spectrophotometer.

• The korean journal of orthodontics
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• v.53 no.3
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• pp.139-149
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• 2023

Objective: To assess the color stability and translucency of full cubic stabilized zirconia (FSZ) following orthodontic bonding with different surface treatments and coffee thermocycling (CTC). Methods: This in vitro study was conducted on 120 disc-shaped specimens of FSZ. Thirty specimens were selected as the control group and remained intact. The remaining specimens were randomly divided into three groups based on the type of surface treatment (n = 30): airborne particle abrasion (APA), silica-coating (CoJet), and carbon dioxide (CO₂) laser. After metal bracket bonding in the test groups, debonding and polishing were performed. Subsequently, all specimens underwent CTC (10,000 cycles). Color parameters, color difference (ΔE₀₀), and translucency parameter (TP) were measured three times at baseline (t0), after debonding and polishing (t1), and after CTC (t2). Data were statistically analyzed (α = 0.05). Results: Significant difference existed among the groups regarding ΔE₀₀t0t2 (p < 0.001). The APA group showed minimum (ΔE₀₀ = 1.15 ± 0.53) and the control group showed maximum (ΔE₀₀ = 0.19 ± 0.02) color stability, with no significant difference between the laser and CoJet groups (p = 0.511). The four groups were significantly different regarding ΔTPt0t2 (p < 0.001). Maximal increases in TP were noted in the CoJet (1.00 ± 0.18) and APA (1.04 ± 0.38) groups while minimal increase was recorded in the control group (0.1 ± 0.02). Conclusions: Orthodontic treatment makes zirconia restorations susceptible to discoloration and increased translucency. Nonetheless, the recorded ΔE₀₀ and ΔTP did not exceed the acceptability threshold.

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.710-714
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• 2014

The effect of titanium dioxide ($TiO_2$) on the properties of color conversion glasses was examined for glasses based on $BaO-ZnO-B_2O_3-SiO_2$. One glass sample, containing 25 mol% of each component, was used as a reference; the other three glass samples contained 1, 3, and 5 mol% $TiO_2$, respectively. The four color conversion glass samples were prepared by sintering a mixture of glass frits and a $YAG:Ce^+$ phosphor. The characteristics of the color conversion glass samples, such as luminous efficacy, luminance, CIE (Commission International de I'Eclairage) chromaticity, CCT (Correlated Color Temperature), and CRI (Color Rendering Index) were analyzed according to the PL spectrum. The refractive index of the glass samples was found to increase with the titanium dioxide content. In conclusion, luminous efficacy of color conversion glasses increased as the content of $TiO_2$ was raised in the glass matrix.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.122-126
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• 2010

In this article photoluminescence of the $Al_2O_3:xCr_2O_3$ solid solutions prepared by solid state reaction method are represented. The effect of $Cr_2O_3$-activator concentration and heat treatment time on the PL characteristics have been discussed in conjunction with microstructure of phosphor samples. The $Al_2O_3:xCr_2O_3$ phosphors show the highest PL intensity at x=0.003 mole when the samples are reacted at $1600^{\circ}C$ for 5 h. The PL emission and absorption spectra show the maximum peaks at 698 nm and at 398 nm respectively. The CIE color coordinate is (x=0.646, y=0.316) at 0.003 mole $Cr_2O_3$, which value is very close to the NTSC coordinate of red color. This characteristic feature of $Al_2O_3:xCr_2O_3$ has been applied for an additive to improve the color characteristic of other red phosphor $LiEuW_2O_8$ which has a relatively poor color purity with an emission peak centered at 615 nm and with a CIE coordinate (x=0.530, y=0.280). The $Al_2O_3:0.003Cr_2O_3$ phosphor has been mixed with the $LiEuW_2O_8$ phosphor powder and the PL characteristics and CIE color coordinates are characterized. The $Al_2O_3:xCr_2O_3$ phosphor was found effective for improving the CRI (color rendering index) of $LiEuW_2O_8$ phosphor.

• Communications of the Korean Mathematical Society
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• v.39 no.2
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• pp.345-352
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• 2024

We introduce a new class of bi-partition function c_k(n), which counts the number of bi-color partitions of n in which the second color only appears at the parts that are multiples of k. We consider two partitions to be the same if they can be obtained by switching the color of parts that are congruent to zero modulo k. We show that the generating function for c_k(n) involves the partial theta function and obtain the following congruences: c₂(27n + 26) ≡ 0 (mod 3) and c₃(4n + 2) ≡ 0 (mod 2).

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.7.1-7.10
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• 2023

Objectives: This study aimed to evaluate the surrounding and underlying shades' effect on the color adjustment potential (CAP) of a single-shade composite used in a thin layer. Materials and Methods: Cylinder specimens (1.0 mm thick) were built with the Vittra APS Unique composite, surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built only with the control composites. Each specimen's color was measured against white and black backgrounds or the simple control specimens with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WI_D) and translucency parameters (TP₀₀) were calculated for simple specimens. Differences (ΔE₀₀) in color between the simple/dual specimens and the controls were calculated. The CAP was calculated based on the ratios between data from simple and dual specimens. Results: The Vittra APS Unique composite showed higher WID and TP₀₀ values than the controls. The highest values of ΔE₀₀ were observed among simple specimens. The color measurements of Vittra APS Unique (simple or dual) against the control specimens presented the lowest color differences. Only surrounding the single-shade composite with a shaded composite barely impacted the ΔE₀₀. The highest CAP values were obtained using a shaded composite under simple or dual specimens. Conclusions: The CAP of Vittra APS Unique was strongly affected by the underlying shade, while surrounding this composite with a shaded one barely affected its color adjustment.

• The Journal of Advanced Prosthodontics
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• v.15 no.2
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• pp.93-100
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• 2023

PURPOSE. The aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns. MATERIALS AND METHODS. A total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 ㎛, 80 ㎛, and 120 ㎛) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE₀₀) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE₀₀ data were analyzed by using two-way ANOVA before and after thermocycling (α = .05). RESULTS. There was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE₀₀ was under the perceptibility threshold in the group of 40 ㎛ cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE₀₀ < 1.8) for all other groups. After thermocycling, the ΔE₀₀ values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values. CONCLUSION. The cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 ㎛ cement thickness. All study groups revealed perceptible color change after thermocycling.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.1
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• pp.88-97
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• 2024

The underwater color environment was assessed by conducting color calculations based on underwater spectral irradiance measurements at various depths. Changes in the distribution of underwater spectral irradiance values between 1 and 3 m, exhibited similar trends in areas Stn. 1, 5, and 6. Likewise, changes between 5 and 20 m displayed comparable patterns in areas Stn. 1, 2, 4, and 6. Color values for each observed area fell between 0.14 and 0.26 (x-values) and 0.2 and 0.36 (y-values), with the y-values exhibiting a variation 1-3 times greater than the x-values. Color a_* and b_* values ranged from a maximum of -17 and -6 to a minimum of -63 and -30, respectively. By classifying fishing grounds based on observed variations, Stn. 1, 9, Stn. 2, 3, Stn. 7, 8 and Stn. 4, 5, 6 were grouped independently. Particularly, Stn. 5, 6, 7, and 8 were categorized into distinct groups that could be visually differentiated, especially when considering the significant changes in color a_* as the water depth increased from 10 to 20 m. Tokyo Bay were classified into different color groups, and Wakayama Prefecture offshore was classified into the same color group as the surveyed fishing grounds.

• 한국해양학회지
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• v.3 no.2
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• pp.55-62
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• 1968

The distributions of average water color and the transparency in the seas around Korea show two patterns: the one is the East Sea and the South Ses, the other is the Yellow Sea. In the East Sea and the South Sea, the water colors C$\sub$E/ in Forel scales change from green to greenish blue with distance x in miles from the seashore, an average color is bluish green, 3.7 in Forel scales, and the relationship is given by C$\sub$E/ = 5e$\^$-0.056.root.x; an average transparency is 15m and the transparency T$\sub$E/ shows following formula with distance x, E$\sub$E/=0.9.root.x+10. In the Yellow Sea, the water color C$\sub$Y/ changes from green yellow to bluish green with distance, an average color is light green, 5.6 in Forel scales, and the relationship is given by C$\sub$Y/= 8.5e$\^$-0.086.root.x; an average transparency is 7m, the farther it is from the seashore, the deeper transparency T$\sub$Y/ is as following, T$\sub$Y/=1.2 .root.x+1. Along the seashore, the transparency T$\sub$Y/ is only 10% that of the East Sea and the South Sea. The distributions of the water color and the transparency by depth change in values within the continental shelf. The water color in Forel scales decreases with the distance from the seashore and depth; the transparency increases with the distance and depth. They are caused by suspended particles, especially suspended clay, and it is the major factor in the change in color and transparency, particularly in the Yellow Sea. In September, the sea water is the clearest in the seas around Korea, transparency shows the maximum and water color the minimum in forel scales. The water color shows green yellow when transparency is 1m, green at 10m, and greenish blue at 20m. the relationship between the water color and the transparency shows an exponential distribution as following, C=9e$\^$-kT/, k=0.0625m$\^$-1/. This formula agrees with calculated formulas between the water color and the transparency from the emprircal formulas C$\sub$E/ and T$\sub$E/, C$\sub$Y/ and T$\sub$Y.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.376-380
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• 2008

The optical properties of multi layered thin films with $Sb_2O_3/Na_3AlF_6/Sb_2O_3/Cr$ were simulated by using EMP(Essential Macleod Program). EMP is a comprehensive software package to design and analyse the optical characteristics of multi-layered thin film. $Sb_2O_3$ and $Na_3AlF_6$ were selected as a high refractive index and low refractive index material respectively. Additionally Cr was chosen as mid reflective material. Optical properties including color effect were systematically studied in terms of different optical thickness of low refractive index material. The optical thickness of $Na_3AlF_6$ was changed as 0.25, 0.5, 0.75 and $1.0\lambda$. The film with 0.25, 0.5, 0.75 and $1.0\lambda$ of optical thickness showed mixed color range between purple and red range, yellowish green and bluish green, purple and mixed color range of green and purple respectively.