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# Irrigants and dressings inside the canal

- Dental material

Sodium hypochlorite is the main root canal irrigant because it dissolves tissue and kills bacteria. Pushed past the root tip, it causes a painful tissue injury.

Updated Nov 12, 2026

**See it in 3D:** [Maxillary sinus](https://durgical.com/en/anatomy/maxillary-sinus/)

## Key points

- Hypochlorite dissolves tissue; EDTA removes smear layer; chlorhexidine is antibacterial only.
- Calcium hydroxide between visits.
- Hypochlorite past the apex: severe pain and swelling.

## What it is

Irrigants flush, dissolve and disinfect the parts of the canal system files cannot reach. Sodium hypochlorite dissolves organic tissue and kills bacteria; a chelating agent such as EDTA removes the mineral smear layer left by files; chlorhexidine is antibacterial but does not dissolve tissue. Between visits a calcium hydroxide dressing keeps the canals disinfected.

## Composition and properties

- Sodium hypochlorite: the only common irrigant that dissolves pulp tissue; strongly antibacterial.
- EDTA (a chelator): removes the smear layer so irrigants and sealer reach the tubules.
- Chlorhexidine: antibacterial and long-acting, but mixed with hypochlorite it forms a brown precipitate, so the canal is rinsed between them.
- Calcium hydroxide paste: the standard dressing between visits; strongly alkaline and antibacterial.
- Antibiotic pastes are used mainly in regenerative endodontics; some contain minocycline, which stains teeth.

## Uses, limits and safety

- Hypochlorite accident: sudden severe pain, rapid swelling, bruising and bleeding from the canal when irrigant goes past the apex or through a perforation.
- Prevent it with rubber dam, a side-vented needle that does not bind in the canal, gentle pressure and staying short of working length.
- Hypochlorite also bleaches clothes and burns eyes: patient bib and eye protection are routine.

## Next step / Initial management

- Suspected hypochlorite accident: stop, irrigate the canal with saline, control pain, apply cold compresses and reassure the patient.
- Swelling spreading to the neck or floor of the mouth, or breathing difficulty: airway first and emergency referral; otherwise refer to the oral surgeon for review the same day.
- Eye splash: irrigate with plenty of water at once and refer to ophthalmology.

## Test yourself

Think of the answer, then tap the question to see it.

## Which root canal irrigant dissolves pulp tissue?

Sodium hypochlorite.

## Why are chlorhexidine and sodium hypochlorite not mixed in the canal?

Together they form a brown precipitate that can block tubules and stain the tooth.

## What are the signs of a hypochlorite accident?

Sudden severe pain, rapid swelling, bruising and bleeding from the canal during irrigation.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/dentistry/irrigants-and-dressings-inside-the-canal/)

## Connections

## See it in 3D 1

The structures of Durgical's 3D anatomy where it is found.

- [Maxillary sinus](https://durgical.com/en/anatomy/maxillary-sinus/)

## Related 5

- [Root canal treatment: access, cleaning, shaping and filling](https://durgical.com/en/dentistry/root-canal-treatment-access-cleaning-shaping-and-filling/)
- [Root canal filling materials and sealers](https://durgical.com/en/dentistry/root-canal-filling-materials-and-sealers/)
- [Immature teeth: apexification and regenerative endodontics](https://durgical.com/en/dentistry/immature-teeth-apexification-and-regenerative-endodontics/)
- [Facial swelling from a tooth: when it is dangerous](https://durgical.com/en/dentistry/facial-swelling-from-a-tooth-when-it-is-dangerous/)
- [Medical emergencies in the dental chair](https://durgical.com/en/dentistry/medical-emergencies-in-the-dental-chair/)

## In Pharmacology 1

- [Chlorhexidine](https://durgical.com/en/pharmacology/chlorhexidine/)

[← All of dentistry](https://durgical.com/en/dentistry/)

Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.

Sources: [Irrigants and irrigation activation systems in Endodontics](https://pmc.ncbi.nlm.nih.gov/articles/PMC10642269/) (Brazilian Dental Journal (PMC open access), 2023); [Factors influencing the occurrence and progress of sodium hypochlorite accident: A narrative and update review](https://pmc.ncbi.nlm.nih.gov/articles/PMC10003279/) (Journal of Conservative Dentistry (PMC open access), 2023); [Endodontic Materials Used To Fill Root Canals](https://www.ncbi.nlm.nih.gov/books/NBK587367/) (StatPearls Publishing (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/dentistry/irrigants-and-dressings-inside-the-canal/