Effect of surrounded shade and specimen`s thickness on color adjustment potential of a single-shade composite

This study evaluated the effect of surrounded shade and specimens` thickness on the color adjustment potential (CAP) of a single-shade composite. The composite Vittra APS Unique was surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens of the control composite were also confectioned. Opacity and whiteness index for dentistry (WID) were calculated for simple specimens. Color differences between the simple (ΔE*SIMPLE)/ dual specimens (ΔE*DUAL) and the controls were calculated. CAP was calculated based on the ratio between ΔE* SIMPLE and ΔE* DUAL. The tested composite presented lower opacity (53 to 62% vs. 80 to 93%) and higher WID (≈ 42 vs. 18 to 32) than controls. Irrespective of the specimens' thickness (1.0/ 1.5 mm), the lowest values of ΔE* SIMPLE (11.1/ 10.8) and ΔE*DUAL (7.2/ 6.1) were observed using the surrounding shade A1. The shade A3 yielded higher ΔE*SIMPLE (16.4/ 17.1) and ΔE* DUAL (11.3/ 12.3) than the A2 (ΔE*SIMPLE = 13.4/ 14.6; and ΔE* DUAL = 9.7/ 10.3). The specimen`s thickness significantly affected the CAP (0.35 and 0.44 for 1.0 and 1.5 mm, respectively) only for shade A1, which had the highest CAP values. The shade A3 resulted in higher CAP values (0.31) than A2 (0.27) when 1.0-mm thick specimens were used, but similar values were observed for 1.5 thick specimens (≈ 0.29). In conclusion, both surrounding shade and specimen thickness can affect the CAP of a single-shade resin composite.