[Chromatic study of composite resins. Report 1. The influence of the color measuring instruments and the background colors on the chromatic values].

The purpose of this study was to investigate the influence of the structural difference of the color measuring instruments and the background colors on the chromatical values of the composite resins. Composite resin disks which were 10 mm in diameter and 1 mm and 2 mm in thickness, and made by the light-cured composite resin Silux Plus (3M Co.) were chromatically measured. The colors of the composite resin used in this study were universal, yellow, dark-yellow and light. The color measuring instruments used in this study were the Murakami Color Research Laboratory Fast Spectrophotometer CMS-500 used with the Flexible Sensor FS-1, FS-2 and FS-3, and the Murakami Color Research Laboratory Color Difference Meter CD-270 used with the Improved Light Guide CD-270. The diameters of the head which receives the light from the object were: FS-1 (2 mm), FS-2 (3 mm), FS-3 (5 mm) and Improved Light Guide CD-270 (2 mm). The chromatical values of the resin specimens were measured without back color, backed by a white plate and backed by a black plate. The chromatical values of the composite resin disks were measured with the different color measuring instruments under the different background colors. The XYZ, Lab* and xy values were compared and the following results were obtained. 1) The chromatical XYZ, Lab* and xy values of the composite resins showed different value patterns among the color measuring instruments. 2) Different influences of the background colors on the chromatical values of the composite resins were obtained among the different colors and different thicknesses of the resins in the cases of some color measuring instruments were used. 3) The most precise color measuring instrument for chromatical measuring of the composite resins among the instruments used in this study was the Fast Spectrophotometer CMS-500 used with the FS-3. 4) Prior to the comparison of the chromatical values measured by the different color measuring instruments, the chromatical values obtained by measurement with the same specimens should be compared and the structural differences, the precision and the sensitivities of the instruments should be understood.