Properties of ideal irrigant solution : 1) broad spectrum antimicrobial properties.2) aid in debridement of the root canal system.3) ability to dissolve necrotic tissue or debris.4) low toxixity level.5) good lubricant.6) low surface tension to flow into inaccessible area.7) ability to sterilize the canal.8) prevent/ dissolve smear layer9) inactivate endotoxin

Functions of irrigants:1) Perform physical and biologic functions remove dentinal shavings by irrigation.2) Dissolve necrotic tissue3) Remove debris from lateral and accessory canals4) Germicidal as well as antibacterial properties5) Bleaching action6) Irrigants with lubricating agent further increase the efficiency7) Opening of dentinal tubules by removal of smear layer.

Factors modifying the activity of irrigating solutions:1) Concentration : tissue dissolving capability of NaOcl is higher at 5.2%2) Contact: to be effective, irrigant must come in contact with the substrate3) Presence of organic tissue : organic tissues must be removed for effective irrigation4) Quantity: increase in quantity increases the effectiveness5) Temperature: warming the NaOcl increases its efficacy

Sodium hypochlorite:1) It contains 5 % of free chlorine which is important for breakdown of proteins into amino groups2) If injected periapically can cause serious damage to tissue:a) Irrigation should be performed passivelyb) With needles with very small diameterc) The syringe should never be locked in the canal3) Efficacy of sodium hypochlorite as antimicrobial agent is increased when it is used in combination with other solutions such as calcium hydroxide , EDTA or chlorexidine.

Urea :1) It denatures the protein by destroying bonds of the secondary structure resulting in loss of functional activity. ( antiseptic property)2) It has the property of chemically debriding the wound by softening the underlying substrate of fibrin3) Excellent vehicle for antimicrobials such as sulfonamides4) It has low toxicity and so, it can be used in patients where vital uninfected pulp has been removed.5) It can be used in open apex or in areas of resorptive defects.

Hydrogen peroxide:1) It is highly unstable and easily decomposed by heat and light. It rapidly dissociates into H2O + [O] ( water and nascent oxygen).2) It causes oxidation of bacterial sulfhydryl group of enzymes and thus interferes with bacterial metabolism 3) The rapid release of [O] nascent oxygen on contact with organic tissue results in effervescence or bubbling action which is thought to aid in mechanical debridement

Urea peroxide:1) Urea peroxide decomposes into urea and H2O2.2) Its mechanism of action combines the effects of urea and hydrogen peroxide3) The anhydrous glyceride increases the stability of urea peroxide (glyoxide).4) the advantages of adding glycerol are:a) It increases the stability of solution, thus increases shelf lifeb) It acts as good lubricant, so facilitates negotiation and instrumentation of thin , tortuous root canalsc) Glyoxide can be used along with EDTA to clean the walls of the canal.5) Disadvantages :It dissociates more slowly than hydrogen peroxide. So, its effervevescence is prolonged but not as pronounced. This can be overcome by alternating irrigation with sodium hypochlorite.

Chlorexidine:1) It is a broad spectrum antimicrobial agent 2) Cationic bisguanide molecular action3) Both 2 and 0.2 % can cause residual antimicrobial activity for 72 hours, if used as an endodontic irrigant.4) Advantages and uses:a) A 2 % solution is used as root irrigant in canalsb) A 0.2% solution can be used in controlling plaque activityc) It is more effective on gram positive bacteria than gram negative bacteria5) Disadvantages :a) It is not considered as the main irrigant in standard endodontic therapyb) It is unable to dissolve necrotic tissue remnantsc) It is less effective on gram-negative than on gram-positive bacteria

Chelating agent:1) After canals are instrumented , an organic layer remains which covers the dentinal tubules.2) Most of studies recommended removal of smear layer because it is the source of microorganisms and also the closest possible adaptation of endodontic filling is possible only after its removal3) EDTA is the most commonly used chelating agent 4) It is commercially available as 15 % solution and PH of 7.3 under the name EDTAC5) EDTA + water soluble carbowax + urea peroxide = RC prep. It is an effective lubricating and cleaning agent. Presence of glycol makes it a lubricant and coats the instrument which facilitates its movement in the canal.6) Citric acid is other commonly used chelating agent for removal of smear layer as irrigating solution.7) Citric acid or EDTA should never be mixed with sodium hypochlorite because EDTA and citric acid strongly interact with sodium hypochlorite.

Irrigant solutions

Prepared by Marwa Merheb