Filler Contents of Resin Composites on Expression of Structural Color

Objectives: The purpose of this study was to examine the influence of filler contents of experimental flowable resin composites on structural color expression.
Methods: Experimental composites containing spherical fillers (average size: 260 nm) with different filler contents, and a structural colored resin composite Omnicroma, and a nanohybrid flowable resin composite Grace Fill LoFlo were used. Standardized specimens, 8.0 mm in diameter and 1.5 mm and 3.0 mm in thickness, were made. Measurements of the optical characteristics of the specimens on a black and white plates were performed using a spectrophotometer, and L*a*b* values were measured. Standardized cavity preparations, 4 mm in diameter and 1.5 mm or 3 mm in depth, were performed in the labial side of each artificial tooth. Each resin composite was placed into the cavity with a single application of paste. Color adjusting ability of the tested resin composites to artificial teeth were also measured using a dental color analysis system. One-way analysis of variance and Tukey post hoc tests were used at α level of 0.05.
Results: The spectral reflectance curve of Omnichroma and experimental composites showed that they reflected light of wavelengths from 430–700 nm on the black plate regardless of the thickness of the specimens. The % reflectance had tendencies to decrease with decrease in percentages of filler contents. The spectral reflectance on the white background was higher than the color change on the white background. The color matching ability of experimental composites improved with higher filler contents.
Conclusions: Within the limitations of the present study, colors of the flowable resin composites were affected by the filler contents and background color. Higher filler contents might be required to achieve the optimal color characteristics of structural colored flowable resin composites, should may lead to esthetic results of the restorations.