**Core Concept**
Calcium hydroxide, chlorhexidine digluconate, and other substances are used as intracanal medicaments to disinfect and promote the healing of the root canal system. Intracanal medicaments are placed inside the root canal to eliminate bacteria and prevent infection.

**Why the Correct Answer is Right**
MTAD (a mixture of tetracycline, an acid, and a detergent) is primarily used as an irrigant in endodontics, not as an intracanal medicament. It is designed to dissolve and remove organic matter, bacteria, and debris from the root canal system. While MTAD has antimicrobial properties, its primary function is as an irrigant, not a medicament.

**Why Each Wrong Option is Incorrect**
**Option A:** Calcium hydroxide is a well-established intracanal medicament used to promote the dissolution of organic matter, reduce microbial load, and stimulate the formation of a hard tissue barrier within the root canal.
**Option B:** Chlorhexidine digluconate is a broad-spectrum antimicrobial agent that is commonly used as an intracanal medicament to control microbial growth and promote root canal disinfection.
**Option D:** Since MTAD is not an intracanal medicament, this option is incorrect, but it's a distractor to test the student's understanding.

**Clinical Pearl / High-Yield Fact**
When selecting an intracanal medicament, consider the type of infection, the presence of a necrotic pulp, and the patient's overall condition. Calcium hydroxide is often used in cases of chronic infections, while chlorhexidine digluconate is preferred in acute infections.

**✓ Correct Answer: C. MTAD.**