Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates

2015 ◽  
Author(s):  
Author(s):  
Mara Elena Rusnac ◽  
Cristina Gasparik ◽  
Ada Gabriela Delean ◽  
Alexandra Iulia Aghiorghiesei ◽  
Diana Dudea

Background and aims. To assess the color, translucency and masking properties of novel flowable giomers. Methods. Three flowable giomers were used for the fabrication of 1-mm thick samples (n=126) in three consistencies (Beautifil flow Plus X F00; Beautifil flow F02; Beautifil flow Plus X F03, Shofu Dental Corporation, Japan) and two shades (A2 and A3). The relative spectral reflectance was recorded over white, black, C3, and a tested-sample colored background. Lightness (L*), and color coordinates a* and b*, Relative Translucency parameter (RTP00) and masking capacity of C3 background were calculated; differences in color and translucency were compared with thresholds for perceptibility and acceptability (PT and AT). Statistical analyses used significance tests for paired samples. Results. All tested materials displayed increased values of L*: for A2 F00=86.16(±0.86), F02=86.39(±0.63), F03=86.40(±0.63); for A3: F00=84.24(±0.58), F02=83.34(±0.3), F03=84.19(±0.4), as well as of RTP: for A2 F00=30.34(±0.88), F02=31.37(±0.94), F03=31.11(±1.15), for A3 F00=29.64(±1.64), F02=30.79(±1.02), F03=30.1(±1.26). For A2 samples, the masking capacity was significantly different for all materials, whilst for A3 there were differences only between F00-F03 and F02-F03. Conclusions. The tested flowable giomers proved high lightness and translucency. The color differences between the materials with the same designation were below the perceptibility threshold in most cases. In addition, the differences in relative translucency parameters ranged between the perceptibility and acceptability thresholds. All tested flowable giomers had an unacceptable masking capacity for a C3 background.


2016 ◽  
Vol 21 (2) ◽  
pp. 81-87 ◽  
Author(s):  
Yong-Keun Lee ◽  
Yu Bin

ABSTRACT Objective: Since the color of esthetic brackets should match that of teeth, the aims of this study were to determine the color and translucency of esthetic brackets by means of the clinically relevant use of a spectroradiometer, and to compare the color of brackets with that of a commercial shade guide. Methods: The color of central and tie-wing regions of four plastic and four ceramic brackets was measured according to the CIE L*a*b* color scale over white and black backgrounds. Brackets were classified into five groups based on their composition. The color of Vitapan Classical Shade Guide tabs was also measured. Translucency parameter (TP) and contrast ratio (CR) were calculated to determine translucency. Results: Color differences between brackets and the shade guide tabs were 10.4 - 34.5 ∆E*ab units. TP and CR values for the central region were 16.4 - 27.7 and 0.38 - 0.58, whereas for the tie-wings they were 24.0 - 39.9 and 0.25 - 0.45, respectively. The color coordinates, TP and CR values were significantly influenced by bracket composition and brand (p < 0.05). Conclusions: Esthetic brackets investigated herein showed unacceptable color differences (∆E*ab > 5.5) compared with the shade guide tabs. Differences in the translucency of brackets by brand were within the visually perceptible range (∆CR > 0.07). Therefore, brackets showing the best matching performance for each case should be selected considering esthetic and functional demands.


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