Why does the gingival portion of natural teeth differ in color from the incisal portion?

The gingival portion of natural teeth differs in color from the incisal portion primarily due to the underlying dentin that affects how light is transmitted and perceived. The gingival area is more closely associated with the dental pulp and the denser dentin that lies beneath it, which tends to have a warmer, more yellowish hue. In contrast, the incisal edge is usually thinner, allowing more light to pass through and creating a lighter, often more translucent appearance due to enamel.

This difference in background tissue—dentin in the gingival area versus less dense enamel in the incisal area—plays a significant role in color perception. Dentin's inherent color affects the overall appearance of the tooth, giving the gingival area a darker or more opaque quality compared to the bright, light-reflecting qualities of the incisal edge, which is primarily influenced by the enamel.

While lighting conditions can affect the perceived color, and differences in fluorescent qualities of the materials certainly exist, the fundamental reason for the color variation lies in the composition and structural differences between the gingival and incisal portions of the teeth.