OPTION 1

Mach band effect:

•            Sometimes a similar but narrower shadow is apparent radiographically on the images of sound teeth below or sometimes above the occlusal enamel. This is an optical illusion which is called 'Mach band'.

•            Ernst Mach first defined this visual phenomenon in 1865.

•            When a uniformly dark shade meets a uniformly light shade, the dark shade seems to become even darker and the light shade lighter as they approach the interface, thereby enhancing the visualization of the edge.