Introduction:-
The success of endodontic treatment is directly influenced by the elimination of microorganisms from infected root canals. Root canal irrigation is an irreplaceable step along with mechanical shaping in order to achieve a clean and disinfected root canal. (Ruddle). The Irrigants with concentration, technique and sequence of the usage will be discussed further.

Properties of an Ideal Irrigant:-
A successful root canal treatment has many aspects and one of the most important is root canal irrigation.

Properties of an irrigant include:-

1. Have a broad antimicrobial spectrum and high efficacy against anaerobic and facultative microorganisms organized in biofilms.
2. Dissolve necrotic pulp tissue remnants.
3. Inactivate endotoxin.
4. Prevent the formation of a smear layer during instrumentation or dissolve the latter once it has formed.

Though volume of the root canal irrigant needed for a root canal irrigation is not fixed, it is supposed to be thorough and copious thus helping dissolve and eliminate all possible sources of infection.

Sodium Hypochlorite (NaOCl):-
Its the most potent of all irrigants available. It is inexpensive & can destroy spore, bacteria & virus, but most importantly it dissolves vital and necrotic pulp leaving a disinfected area. Its the most widely used in the world. NaOCl concentrations have always been debatable but the two most widely used in India are 5% and 3%. Efficacy of the NaOCl can be increased by increasing its temperature and concentration. Despite of all the positives NaOCl cannot eliminate the smear layer formed on the dentinal wall. It is toxic and with the concentrations used it should be ideally used with high precautions. Extrusion of sodium hypochlorite in periapical tissues is known to cause severe intra-operative pain and necrosis of surrounding tissues.

EthyleneDiamineTetraAcetic Acid (EDTA):-
It is available in two forms Gel & Aqueous. Gel form is used commonly in dentistry it is combination of urea peroxide with EDTA in water soluble carbowax. It helps in lubricating the canal and holding the debris in suspension which makes it easier to flush it out. But the gel form doesn’t inhibit the formation of smear layer. Removal of smear layer is an important step to achieve tighter bond between dentinal walls and the obturating material. 17% Aqueous EDTA irrigation is effective  in removing the smear layer after the cleaning and shaping of root canal is done.

Chlorhexidine:-
Chlorhexidine is a Bisguanide widely used in plaque control. It has been advocated as the final irrigant.
Similar to NaOCl efficacy of chlorhexidine can be increased with increase in temperature. Chlorhexidine when used as final irrigant binds with the dentinal tissues exhibiting substantivity. It thus provides a prolonged antimicrobial action. Using Chlorhexidine as a final irrigant does not interfere with the bonding of the sealer. Chlorhexidine should never be used in conjugation with Sodium Hypochlorite as it will precipitate in brownish-reddish mass.

Role of Lateral Vented Needles :- (Figure 1 & Figure 2)
Lateral vented needles are custom made needles which are closed at the tip and have vents on the side thus minimizing the force which might push the irrigant periapically. When the solution is liberated from side of the needle it also flows in lateral canals thus helping disinfect all the accessory canals,fins webs and anastomoses.

Procedure of irrigation:- An irrigant can be used passively or actively depending on a operator. An irrigant when used is used with the help of a canula or needle to enter the canal. The needle/canula should have a lose fit, as to maximize the effect and let the debris be washed out coronally, A tight fit during injecting might push the irrigant periapically. Slowly injecting the irrigant with continous hand movements almost minimizes the NaOCl accidents.

Activation of Irrigation :- An irrigant maximizes its efficacy when it is agitated and thus produces a bubbling action (effervescence) which helps it flow into accessory canals. This can be achieved either by vigorous hand motion (Up & Down) with a file or an ultrasonic handpiece. The canal is filled with irrigant solution and then the procedure is performed. An endodontic activator is also available in the market to help in activation of irrigant.

Suggested Irrigation Regimen :-
Copious irrigation with Sodium Hypochlorite till completion of the Bio-mechanical prep is achieved to dissolve tissue and disinfect root canal with use of EDTA gel form for lubrication & to hold debris in suspension.
Aqueous EDTA to be used after cleaning & shaping of the root canal is finished to remove the smear layer.
Final irrigant Sodium Hypochlorite to be used.

Dealing with Irrigant Accidents:-
Irrigant accidents should not occur and all the necessary precaution should be taken by the dentist. But there are times when the accidents do occur and dealing with them without necessary equipments is a major challenge. Accidents are more common with NaOCl as it is the most widely used irrigant.

Irrigant Spillage is the most common accident that can occur during a endodontic procedure, it should be treated by washing the area where the irrigant is spilled and application of a gum smoothening agent like Gumex. It can be avoided by using a rubber dam.

Periapical extrusion of irrigant isn’t common but when it occurs it gives intense and spontaneous pain to the patient for 2-6 mins with ballooning of adjacent soft tissue, oedema, profuse internal bleeding
Treatment focuses on telling the patient about the accident and then immediately starting irrigation with saline to dilute NaOCl. Bleeding should be allowed to continue as it helps in flushing out the irrigant followed by ice pack and palliative treatment for pain, and monitoring of the patient.

The rarest case of accident is injecting the irrigant in soft tissue this should be followed by immediately injecting hyaluronidase enzyme in the same area within a minute,

Conclusion:-

Sodium Hypolchlorite comes very close to being the ideal irrigant but needs monitored usage. EDTA helps in the removal of smear layer and is therefore used, so as to have better bonding with the sealers. Chlorhexidine though advocated by some endodontists, cannot be used in conjunction with sodium hypochlorite, and usage of only chlorhexidine alone is not advocated. Thus the role of irrigants is very essential in the endodontic procedure right from the beginning but it also necessitates the cautious use of the solutions as to prevent accidents. With proper usage amazing results can be achieved in cases like Anastomoses (Figure 3) and even an ideal filling (Figure 4).

Fig. 1	Fig. 2	Fig. 3	Fig. 4

Refrences:-

1. Ingle Textbook of Endodontics
2. Matthias Zehnder, Review Article Root Canal Irrigants, Journal Of Endodontics — Volume 32, Number 5, May 2006
3. Rob Kauffman, The current status of irrigation in endodontics-What to use and how, The EndoFiles Fax January 2002: Volume 3 Issue I
4. Z. Mohammadi & P. V. Abbott, Chlorhexidine in Endodontics, International Endodontic Journal, 42, 288–302, 2009
5. Clifford J.Ruddle, Hydrodynamic Disinfection Tsunami Endodontics, Dentistry Today May 2007
6. Mehdipour O, Kleier DJ, Averbach RE,  Anatomy of sodium hypochlorite accidents, Compend Contin Educ Dent. 2007 Oct;28(10):544-6, 548, 550.