The purpose of this study was to find correlations among the color differences measured by three methods. Those tuere 1)spectrophotometric method(Differential Colorimeter, Model TC-6FX, Denshoku, Japan), 2) digital image method - photographed b~, digital camera(KODAK Digital Camera 40, Kodak, USA) and processed by computer program(Adobe Photoshop 3.0), 3) 35 mm standard slide method took photographic color slide, read using scanner(Nikon 35 mm Film scanner, LS-3510 AF, Nikon, Japan) and processed by computer program(Adobe Photoshop 3.0). The color of resin modified glass ionomers were determined in vitro before and after thermocycling for 500 to 2,000 cycles. The values of CIELAB AE*, L*, a*, b*, r, g, b, r*, g*, b` were, analyzed to find correlations among them. From the experiment, the following results were obtained
1. There´ were no statistically` significant correlation among the values of CIELAB AE*, AC measured by digital camera and AC* measured by color slid,´ and scanner(Sig. F>0.05):
2. There was a statistically significant correlation between` the values of CIELAB L* and GR´ measured by digital camera(Sig. F = 0), and some pairs showed-significant correlation among CIELAB a*, b* value and r,, g, b value determined by digital `camera and r*, g*, b* value determined by. color slide and scanner.
3 The values of r, g, b determined by digital camera, and the values of r*, g`, b* value determined by color slide and scanner showed significant correlation between each corresponding values(Sig. F = 0). In this case, correlation coeffcient were 0.:x;9 -0.413.
4. In the same materials; the degree of color change was different depending on the shades, and of some shades showed of ´materials clearly different color change depending the measuring method.
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