Background and surrounding colors affect the color blending of a single-shade composite

This study evaluated the background and effect of surrounding colors on the color blending of a single-shade composite used in a thin layer. Disc-shaped specimens (1.0 mm thickness) were built with the Vittra APS Unique composite surrounded (dual specimens) or not surrounded (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built with only control composites. The specimen color was measured against white and black backgrounds with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WID) was calculated for simple specimens. Differences (Delta E-00) in color and translucency parameters (Delta P-00) between the simple/dual specimens and the controls were calculated. The translucency adjustment potential (TAP) and color adjustment potential (CAP) were estimated based on the ratios between data from simple and dual specimens. The Vittra APS Unique composite showed higher WID values than the controls. No differences between Delta TP00_SIMPLE and Delta TP00_DUAL were observed for any of the shades. The composite shade did not affect TAP values. The lowest values of Delta E-00_SIMPLE and Delta E-00_DUAL were observed for shade A1 regardless of the background color. For the white background, Delta E-00_SIMPLE values did not differ from those of Delta E-00_DUAL for all shades. Only A1 showed Delta(E00_DUAL) values lower than Delta E-00_SIMPLE when the black background was used. The highest modulus of CAP (negative values for the white background) was observed when shade A1 surrounded the Vittra APS Unique composite. The color blending ability of the single-shade resin composite used in a thin layer was affected by both the surrounding shade and background color.