Illuminant metameric effects on interbrand and intrabrand color differences of direct composite resins

Information on the illuminant metameric effects on the intrabrand and interbrand differences in color of direct composite resins is lacking.

The purpose of this in vitro study was to evaluate the effects of different illuminations on the color differences of the same or different brands of composite resins.

Sixty-four disks were prepared from 8 different direct dental composite resins of A3 shade, and, after polymerization and hydration for 48 hours, their color coordinates were measured in the Commission Internationale de I'Eclairage (CIE) L∗a∗b∗ color space with a portable colorimeter on a black and white background under D65 (daylight), F2 (cool white fluorescence), and A (incandescence) illuminations. Translucency parameters (TP) and fluorescence intensities (FI) of the brands were also measured to assist in the interpretation of brand behavior under the illuminations. The Kruskal-Wallis and Friedman nonparametric tests with post hoc multiple comparisons tests were applied to analyze the data for differences within and between brands under all illuminations (α=.05), while regression analysis was used to estimate the relationship between D65 and F2 or A illumination data.

Statistical analysis showed significant differences among brands (P<.05) for all color coordinates under all illuminations, with a strong linear relationship between them (R2=0.72-0.97). Intrabrand differences were significantly different across brands (P<.05) and ranged from 0.06 to 3.1 across illuminations in ΔE∗_ab units (0.05 to 2.4 in ΔΕ₀₀ units). Interbrand differences were also significantly different (P<.05), with a range of 0.15 to 8.7 ΔE∗_ab units or 0.14 to 5.7 ΔΕ₀₀ units.

Primary color coordinates of composite resins were affected by A or F2 illumination and were strongly associated with D65 values. Redder or yellower composite resins were affected more under A or F2 illumination. Intrabrand differences, although small, may contribute to clinical mismatches under A or F2 illuminations. Clinicians should be aware that certain brand pairs may present acceptable differences under D65 illumination but could become unacceptable under A or F2 illumination.