Which visual sign indicates an inactive carious lesion?

• A. Shiny
• B. Semitransparent
• C. Smooth with explorer
• D. Plaque free

Answer: (C)

The key sign is a surface that is smooth and resists probing. When a carious lesion has become inactive (arrested), the surface mineralizes and hardens, so an explorer can glide over it without catching, indicating a firm, smooth surface. This tactile finding is the most reliable indicator that progression has stopped, which is why it best identifies an inactive lesion.

Shiny surfaces can be seen with arrested lesions but are not as definitive on their own, and semitransparent describes subsurface changes typical of early demineralization rather than inactivity. Plaque-free status isn’t a reliable activity indicator by itself, since activity depends on lesion progression and surface integrity rather than plaque presence or absence.