Intracanal medication in endodontics is necessary for complete canal cleaning because it helps eliminate bacteria that mechanical instrumentation and irrigation alone cannot remove. These medications, such as calcium hydroxide, provide sustained antimicrobial action within the complex root canal system, reducing bacterial load and preventing reinfection. Additionally, intracanal medicaments aid in dissolving necrotic tissue remnants and controlling inflammation, which are crucial for successful healing of periapical tissues. Without intracanal medication, complete microbial eradication is often unachievable, compromising treatment outcomes.

Reference: Pathways of the Pulp, Cohen & Hargreaves, 12th Edition.