What is the standard range of sodium hypochlorite concentration commonly used for intra-canal irrigation in conventional endodontic therapy, and what risk increases with higher concentrations?

• A. 0.5% to 1%
• B. 7% to 8%
• C. 2.5% to 5.25%
• D. 10% to 12%

Answer: (C)

Sodium hypochlorite irrigation is chosen to balance antimicrobial action and tissue dissolution with safety for the patient. In conventional endodontic therapy, the commonly used range is 2.5% to 5.25%. Within this window, the solution effectively disrupts Biofilm and dissolves organic tissue enough to clean the canal while remaining manageable in terms of toxicity when delivered carefully.

As the concentration rises toward the upper end, the solution becomes more cytotoxic to living tissues. This means a higher risk of irritation or necrosis if the solution is extruded beyond the apex or comes into contact with periapical tissues. The higher concentrations also enhance dentin dissolution, which can affect structural integrity if not used judiciously. So, the 2.5% to 5.25% range offers a practical balance between efficacy and safety.