How far into dentin should the initial cavity extension reach?

• A. 0.2 mm
• B. 1.0 mm
• C. 0.05 mm
• D. 0.5 mm

Answer: (A)

Conserving tooth structure while allowing effective caries removal is the key idea. The initial dentin extension should be very shallow so you can remove the softened infected dentin without approaching the pulp too closely. About 0.2 mm into dentin gives a safe margin: it’s deep enough to begin cleaning away compromised tissue and assess hardness, yet shallow enough to minimize pulpal irritation and preserve dentin thickness for strength and for future restoration.

If you go deeper than this in the initial stage, you increase the risk of pulp exposure or weakening the tooth, especially before placing any liner or base. Too shallow a depth, on the other hand, might not adequately remove affected dentin and could leave caries behind. So, the chosen depth represents a cautious, controlled start that can be followed by further extension only as needed and with appropriate protective steps.