Beyond apexification and apexogenesis, what is the principal use of CALCIUM HYDROXIDE in conventional root canal treatment?

Correct answer: D. As an interappointment intracanal medicament

• A. Calcium hydroxide is a component of some sealers, but as a material in its own right it is not a definitive sealer — it is soluble and resorbs over time.
• B. Its solubility makes calcium hydroxide entirely unsuitable as a permanent obturating material in a mature tooth. It resorbs, leaving voids and a route for reinfection.
• C. SODIUM HYPOCHLORITE remains the primary irrigant because of its tissue-dissolving capacity and broad antimicrobial action; calcium hydroxide can be used in a slurry but does not replace it.
• D. CORRECT. Calcium hydroxide is placed as an INTERAPPOINTMENT INTRACANAL MEDICAMENT between visits. Its high pH of approximately 12.5 makes it antibacterial, it hydrolyses the lipid A component of bacterial lipopolysaccharide and thereby inactivates endotoxin, it helps control persistent exudate and inflammatory root resorption, and it acts as a physical barrier against recontamination. It is the most widely used interappointment dressing in endodontics.

Note: ⚑ The contributor found this option surprising because files usually present calcium hydroxide only in the apexification/apexogenesis context. The full list of uses is broader: interappointment dressing, direct and indirect pulp capping, pulpotomy medicament, apexification barrier, and management of inflammatory root resorption. One caveat: prolonged placement over many months weakens dentine and increases fracture risk.