Changes of optical properties of dental nano-filled resin composites after curing and thermocycling

The objective was to evaluate the color changes after curing, polishing, and thermocycling of a nano-filled resin composite. A nano-filled composite was grouped into two shades of enamel (EN) and translucent (TL). One hybrid composite was used as a control (CL). Color of specimens of 10 mm in diameter and 2 mm in thickness was measured on a reflection spectrophotometer with SCE geometry under the D65 illumination over white and black backgrounds. Color before curing and after curing, polishing and thermocycling was measured. Color change (DeltaE*(ab)), translucency parameter (TP), and contrast ratio (CR) were compared. Average DeltaE*(ab) after curing was 4.6 in the EN group and 10.4 in the TL group compare to 2.9 in CL. Polishing caused average DeltaE*(ab) of 3.3-3.6, which was not different by the shade group (p > 0.05). After 2000 cycles of thermocycling, average DeltaE*(ab) was 1.4-1.8, which was not different by the shade group (p > 0.05). TP values increased after curing in the EN group, but decreased in the TL group (p < 0.05). TP values after thermocycling decreased in the EN group but did not change in TL (p = 0.05). TP values of TL shades were higher than those of EN regardless of specimen conditions (p < 0.05). Changes in CR values showed similar trends to those of TP values in translucency. Changes of color and translucency after curing, polishing, and thermocycling varied by the shade group. (C) 2004 Wiley Periodicals, Inc.