An avulsed tooth with an open apex has been replanted, and the pulp has become necrotic. Which material is used to create the apical seal?

Correct answer: D. Mineral trioxide aggregate

• A. Zinc oxide-eugenol is a temporary material; eugenol is cytotoxic to periapical tissues and it does not seal reliably against an open apex.
• B. Amalgam was historically used as a root-end filling but is dimensionally unstable at the margins, stains tissue, and has been superseded by MTA.
• C. Conventional glass ionomer is moisture-sensitive during setting and is not indicated for an apical barrier in a wet field.
• D. CORRECT. MTA is the material of choice for creating an apical barrier in an open apex. It sets in the presence of moisture and blood, seals exceptionally well, is highly biocompatible, and is actively osteoconductive — hard tissue forms directly against it. A 4–5 mm apical plug is condensed and the remainder of the canal backfilled.

Note: Bioceramic putties (Biodentine, EndoSequence) share MTA's properties with faster setting and less discolouration — worth knowing as equivalent alternatives.