Six months after placing calcium hydroxide in the canal of a young patient's non-vital central incisor with an open apex, a size 70 file still passes through the apex. What is the most appropriate next step?

Correct answer: C. Place an MTA apical plug and obturate

• A. Extraction is unjustified — the tooth is restorable and apical barrier techniques are highly predictable.
• B. Obturating an open apex with warm vertical compaction alone would extrude material freely into the periapical tissues; a barrier must be established first.
• C. CORRECT. Six months of calcium hydroxide has failed to produce a barrier that will stop a size 70 file, and traditional apexification can require 6–24 months of repeated dressings — during which the root is weakened by prolonged alkaline exposure. Contemporary management is a one-visit MTA APICAL PLUG: a 4–5 mm barrier condensed against a matrix, backfilled with gutta-percha and a bonded core. Bioceramic putties serve the same purpose.
• D. Zinc oxide-eugenol is not an apexification medicament, and simply waiting longer perpetuates the problem while further embrittling the root.

Note: That was standard practice historically, but current guidance favours an MTA or bioceramic apical plug once calcium hydroxide has failed — it is faster and avoids the increased cervical fracture risk associated with long-term calcium hydroxide. Worth discussing as a group.