The preferred material for canal obturation in a pulpectomy of a primary tooth is:

Correct answer: A. Zinc oxide eugenol (ZOE)

• A. Correct. Zinc oxide eugenol (ZOE) paste is the traditional preferred obturating material for primary tooth pulpectomy because it is resorbable (resorbs at a similar rate as the primary tooth roots during exfoliation), well-tolerated by periapical tissues, and antibacterial.
• B. Formocresol is used for pulpotomy (devitalization of coronal pulp in primaries), not for canal obturation in pulpectomy.
• C. Gutta-percha is non-resorbable and used in permanent teeth; it is contraindicated in primary tooth pulpectomy because it does not resorb with the primary root.
• D. Ca(OH)2 paste is resorbable and antibacterial, sometimes used in primary tooth pulpectomy, but ZOE is more established and traditionally preferred.