Influence of fluorescent and opalescent properties of resin composites on the masking effect.

The objective of this study was to determine the influence of fluorescent properties in the reflectance and transmittance modes and opalescent properties and translucency under ultraviolet (UV)-included and -excluded conditions on the masking effect of commercial resin composites quantitatively. Color and spectral distribution of seven resin composites (14 shades) of 1-mm thick were measured in the reflectance and transmittance modes under UV-included and -excluded conditions. For the fluorescence evaluation, subtraction spectra by the inclusion and exclusion of the UV component of the illumination in the reflectance and transmittance modes were calculated. Opalescence parameter (DeltaO*(ab)) was calculated as the difference in yellow-blue (Deltab*) and red-green (Deltaa*) coordinates between the reflected and transmitted colors under UV-included and -excluded conditions. Under UV-included and -excluded conditions, translucency parameter (TP) was calculated and masking effect was calculated as the color difference between a specimen over a black tile and black tile itself. Fluorescent and opalescent properties varied by the brand and shade of composites and measurement protocols. Masking effect was correlated with TP values when TP values of materials were obviously different. But when TP values were in the similar range, the opalescent property influenced the masking effect of resin composites. The influence of fluorescent property on masking effect was also confirmed, although the degree of correlation was very low.