Influence of illuminating and viewing aperture size on the color of dental resin composites

Objectives. The objective was to evaluate the difference in the color of dental resin composites by the illuminating and viewing aperture sizes. The influences of the color measuring geometry, standard illumination and surface roughness on the color were also determined. Methods. Color of five brands of resin composites of A2 shade was measured after-polymerization and after-polishing. Color was measured according to the CIE L*a*b* color scale with the SCE and SCI geometry under the CIE standard illumination of A and D65. The illuminating/viewing aperture sizes were 11 mm/8 mm (8 mm) and 3 mm/3 mm (3 mm). Results. Regardless of the measuring geometry, CIE L*, a* and b* values measured at 3 mm were lower than those at 8 mm. Changes in L*, a* and b* values by the difference in the aperture size were 17.22–21.32, 3.43–6.64 and 13.82–16.81, respectively, and the color difference (ΔE*) was 16.23–27.87 with the SCE geometry. Regardless of the aperture size, ΔE* values caused by polishing measured with the SCE were significantly higher than those with the SCI. Significance. Aperture size, measuring geometry and surface conditions of specimen should be considered when comparing the result of color measurement.