Introduction 

The shaping and cleaning of the root canal constitutes one of the most important phases of endodontic therapy. The shaping of the root canal is done by hand and rotary instrumentation. Cleaning of the root canal is majorly done by endodontic irrigants. It also removes the debris and dentinal chips produced during shaping and cleaning; disinfects the root canal thereby eradicating the intraradicular microbial infection.

Objective of Irrigation 

• Remove the debris created during shaping of the root canal.

• Lubricate the root canal. 

• Dissolve organic and inorganic tissues. 

• Remove and prevent the formation of a smear layer.

Ideal Requirements of an Endodontic Irrigants

• Antimicrobial activity 

• Mechanically pushes out the debris from the root canal 

• Nontoxic and nonirritating to the periapical tissues 

• Dissolves necrotic and vital pulp tissues 

• Serves as a lubricant 

• Removes the smear layer 

• Low surface tension 

• Has no adverse effect on the physical properties of dentin 

• Does not interact with the sealing ability of either the root canal sealer or the obturating material 

• Is easy to use and economical

Classification 

Tissue dissolving:

• Sodium hypochlorite 

• Chloroform

Antibacterial:

• Bactericidal: Chlorhexidine

• Bacteriostatic: MTAD

Chelating agents:

• Mild pH: HEBP

• Strong pH: EDTA

Sodium Hypochlorite

It is a reducing agent, clear, straw-coloured solution containing 5% of available chlorine.

Mechanism of action:

On ionization, NaOCl produces hypochlorous acid and hypochlorite leading to antibacterial action. 

It penetrates the bacterial cell wall and chemically combines with the protoplasm and disrupts the DNA synthesis. 

It removes the organic part of the endodontic smear layer.

Properties:

• 0.5% to 5.2% of NaOCl can be used as an irrigant for root canal.

• It dissolves the entire pulp in 20 minutes to 2 hours. 

• Cytotoxicity and caustic effects as side effects.

• It has an unpleasant taste.

• Most commonly 2.5% concentration is used as it decreases the toxicity while maintaining the tissue dissolving and antimicrobial properties.

• Effectiveness of NaOCl is increased by increasing volume of irrigants, increasing exposure time, ultrasonic activation, warming the solution.

• It should not be mixed with EDTA, or else, tissue dissolving property is lost.

EDTA - EthyleneDiamineTetraAcetic acid

It is a chelating agent introduced by Nygaard - Ostby. 

17% of EDTA is non toxic. 

Mechanism of action:

It forms calcium chelate with the calcium ions of dentin which is more friable and easier for instrumentation. It removes the inorganic component of the endodontic smear layer. 

Properties:

• It softens dentin.

• It removes the inorganic part of the smear layer.

• Extent of demineralisation is proportional to the exposure time.

• It can be used to negotiate the root canals with instruments coated with EDTA.

• It should be used as final irrigant after using NaOCl.

Recommended regimen: 5.25% NaOCl during shaping -> 17% EDTA as final rinse before obturation.

Chlorhexidine Digluconate 2%

It is a cationic bisbiguanide. It is less toxic compared to other irrigants.

Mechanism of action:

2% CHX electrostatically binds with negatively charged bacterial surfaces and renders antimicrobial activity. 

It penetrates the cell wall of gram positive bacteria and yeast, coagulating the cytoplasmic components. 

Properties:

• It is very effective against E. fecalis

• Substantivity - sustained action within the root canal for prolonged time.

• It lacks tissue dissolving property.

• It does not remove the smear layer.

• It is used as an adjuvant to other irrigants.

Other irrigants

1-Hydroxyethylidene-1,1-Bisphosphonate - HEBP

It is also called Etidronic Acid.

HEBP is a weak chelator.

HEBP does not interact with NaOCl and thus can be used in conjunction with NaOCl, potentially removing the endodontic smear layer.

Iodine Potassium Iodide - IKI 

IKI is a broad-spectrum antimicrobial irrigant used in a concentration of 2–5% in endodontics. 

It can be an allergen to some patients.

MTAD

It consists of:

• Aqueous solution of 3% doxycycline, antibiotic

• 4.25% citric acid, a demineralizing agent 

• 0.5% polysorbate 80 detergent (Tween 80) 

It is commonly employed after initial irrigation with 1.3% NaOCl. 

Tetraclean 

It is similar in composition to MTAD with a lower concentration of doxycycline. 

QMix

QMix contains a CHX-analog, triclosan, and EDTA as a decalcifying agent.

It is recommended to be used as a final rinse after NaOCl as an irrigant.

It has antimicrobial and smear layer removal properties.

Guidelines 

Instruments used:

• Disposable Luer lock syringes

• Closed-ended 30-gauge side-vented needles for apical third irrigation

• Open-ended 25- to 27-gauge needles for coronal and middle third root canal irrigation

Rubber dam is mandatory to isolate the pulp space and prevent irrigants contact with oral tissues.

Keep separate color-coded syringes for different irrigants.

All needles should be inserted passively without binding into the root canal. 

The open-ended 25- to 27-gauge needle ejects the irrigant a greater rate of flow and directs the irrigant flow apically. 

The 30-gauge needle should be inserted at a distance of 1–3 mm short of the working length without binding. 

Irrigation should be followed by thorough drying of the root canals a er the completion of shaping and cleaning. Final drying should be e ected with absorbent points.

Factors affecting the efficacy of irrigants:

• Volume of the irrigant

• Concentration of the irrigant 

• Frequency of irrigation 

• Temperature of the irrigant 

• Length and time of intracanal contact 

• Gauge of the irrigating needle 

• Depth of penetration 

• Diameter of the prepared canals 

• Age of the irrigating solution 

Irrigant agitation/activation

It is the process of activating an irrigant through the introduction of an instrument into the canal and moving it within the canal with a reciprocating, oscillating, or rotating action.