1.      Stage 1

• Initial demineralization at the microscopical level
• Formation of the translucent zone
• No clinical or radiographical signs.

2.      Stage 2

• Further demineralization
• Spread of the translucent zone
• Initial redeposition of minerals within the defect
• Formation of dark zone
• No clinical or radiographical signs.

3.      Stage 3

• Formation of the classical structure of the lesion
• Increased porosity in the body of the lesion clinically on the dry surface layer remains intact

4.      Stage 4

• Progression of the lesion towards the enamel dentin junction
• Bacterial invasion and clinically visible destruction of the surface layer
• Can be seen dentin reaction.