What is metamerism in the context of dental shade matching?

Metamerism occurs when two objects with different spectral reflectance curves appear to match in color under one light source (e.g., daylight) but appear different under another light source (e.g., incandescent or fluorescent light). In dentistry, this is clinically significant when a crown or restoration appears to match the adjacent teeth in the dental office but appears mismatched in different lighting conditions (e.g., at home or in sunlight). To minimize metamerism, shade selection should be performed under multiple light sources.