Reflectance spectra of composite resins on liners

The reflectance spectra of two types of composite resins were determined on various backgrounds. It was found that the shade differences caused by different "whitish" liners were perceptible only for thin resin specimens and were smaller than those caused by varying the resin type and thickness. Employing a light brown liner gave rise to a difference in shade which was also perceptible on resin specimens of 2.5 mm thickness. Shade differences due to varying the thickness of the specimens were more pronounced on white than on black backgrounds. The clinical significance and the qualitative physical interpretation of the results were discussed.