Endodontic irrigation is the most important disinfection step in root canal treatment. Mechanical shaping alone cannot reach the complex canal anatomy — isthmuses, lateral canals, apical deltas, and dentinal tubules. The irrigant is what actually kills bacteria and dissolves the tissue that files leave behind.
The primary irrigant. Concentrations from 0.5% to 6% are used; most practitioners use 3–5.25%. NaOCl is the only commonly used irrigant that dissolves organic tissue. Antimicrobial efficacy depends on concentration, volume, contact time, and temperature.
Ethylenediaminetetraacetic acid is used in a 1–3 minute final rinse to remove the smear layer by chelating calcium ions in dentine. Use at the end of shaping; do not mix directly with NaOCl (they deactivate each other).
Broad-spectrum antimicrobial, with substantivity in dentine. Does not dissolve tissue. Often used as a final rinse or alternative in iodine/NaOCl allergy. Do not mix with NaOCl — forms a brown precipitate (parachloroaniline).
Inert flush; used between NaOCl and EDTA to prevent direct mixing.
Passive needle irrigation delivers fluid but does not distribute it effectively, especially in the apical third. Activation greatly improves efficacy: