ENDODONTIC IRRIGANTS

Endodontic success depends on the triad of biomechanical preparation, pulp space sterilization, and three-dimensional obturation.

Complete disinfection of the pulp space cannot be achieved with instrumentation techniques alone.

The use of adjunctive aids like endodontic irrigants in achieving this goal is essential.

 Irrigants can augment mechanical debridement by flushing out debris, dissolving tissue, and disinfecting the root canal system

IDEAL REQUIREMENTS OF ROOT CANAL IRRIGANTS

Sodium hypochlorite-NaOCl has two important properties, namely, antimicrobial activity, and organic tissue dissolution

NaOCl has organic tissue dissolving properties which will help in degrading fatty acids and transforming them into fatty acid salts (soap) and glycerol (alcohol) which will help to reduce the surface tension of the remaining solution. 

NaOCl buffers the amino acids forming water and salt. Formation of hydroxyl ions takes place which leads to the reduction of pH.

 Hypochlorous acid combines with protein amino groups to form chloramines. This reaction between chlorine and the amino group (NH) leads to the formation of chloramines that interfere with the cell metabolism.

Antimicrobial action of chlorine occurs by inhibiting bacterial enzymes and leading to an oxidation of SH groups (sulphydryl groups) of bacterial enzymes

Methods to increase the efficacy of NaOCl

1. TemperatureWarming of low concentration NaOCl solution increases the

efficacy of tissue dissolution and its antibacterial propertiesRecent studies showed that a temperature rise of 25°C

increased NaOCl efficacy by 100 times.

2. Ultrasonic agitationThe ultrasonic agitation with a small file (mostly ISO no. 15) in

canals filled with NaOCl lead to the development of ultrasonic energy which warms the solution in the canal.

The vibrations cause movement of aqueous NaOCl into the ramifications in the canal, this effect being called as "acoustic streaming." 

3. Use of fresh solution

Freshly prepared NaOCl solutions have better antimicrobial and tissue dissolving effects. Since NaOCl decomposes quickly, it is stored in opaque containers.

4. Increasing the volume and the duration of the irrigation.

Quick points

NaOCl is an efficient organic solvent that causes dentin degeneration because of the dissolution of collagen 

Busslinger and Barbakow evaluated corrosion of endodontic files caused by NaOCl solutions of different concentrations from 0.5% to 5.5%, and concluded that the quantities of ions released by the corrosion process into the NaOCl solutions were insignificant

NaOCl irrigation leads to decreased bond strength between dentin and resin cements and may require a reversal agent because of its ability to affect the polymerization of the resin sealer

Ascorbic acid or sodium ascorbate have been shown to completely reverse this reduction in bond strength.

The reaction between NaOCl and CHX produces a carcinogenic product, parachloroanaline (PCA). This reaction coats the canal surface and significantly occludes the dentinal tubules and affects the seal of the root canal

CHX

It belongs to the poly biguanide family, substances which have a positive charge. 

 The antibacterial effect of CHX is due to its positive charge, which is attracted to the negatively charged bacterial cell wall and increases the permeability of bacterial contents.

It shows increased antimicrobial activity against endodontic pathogens like Staphylococcus aureus, Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, E. faecalis, C. albicans, and Streptococcus mutants

Quick points

CHX can bind phosphate, which leads to release of small amounts of calcium from the root canal dentin.

When CHX and EDTA interact, a precipitate is formed that is over 90% CHX and EDTA. No clinical significance

Antimicrobial substantivity of a 2% CHX solution as an endodontic irrigant and reported that the substantivity lasted 72 h

 Antimicrobial substantivity depends on the number of CHX molecules available to interact with the dentine

 Because of its broad-spectrum MMP-inhibitory effect, CHX can significantly improve the resin–dentine bond stability

Iodine

 Iodine is bactericidal, fungicidal, virucidal, sporicidal, degrades proteins, nucleotides, and fatty acids, leading to bacterial cell death. 

 The advantages of iodine over the other irrigants is that 2% of preparations are shown to be less irritating, poisonous, and rapidly reduces the bacterial load

 Two percent IKI needs 1-2 h to inhibit the development of E. faecalis and C. albicans. 

 Iodine has the capability to penetrate all the way through dentinal tubules and destroy bacteria, though the period of its antimicrobial action is less. 

 It has the disadvantage of staining dentin tissue. 

Ethylene diamine tetra acetic acid

It is available in concentrations of 17% as a root canal irrigant with a pH of 7. 

 It kills microbes by chelating with metallic ions needed for growth of bacteria. 

The concentrations of 15-17% eliminates calcium from dentine leaving an organic matrix and removes the smear layer.

Application of EDTA in the root canal system is done for 1-5 min to get the optimum effect.

It has been reported that EDTA decalcified dentin to a depth of 20–30 μm in 5 min

The addition of a quaternary ammonium bromide (Cetavlon) increases the action of EDTA by decreasing its surface tension. This combination is called as EDTAC, and it is effective in smear layer removal and increasing the diameter of opened dentin tubules

Citric acid

It is available in 10-50% concentration which is a demineralizing solution that is used during the endodontic therapy to remove the smear layer from the prepared root canal. 

Citric acid interferes with the mechanism of action of NaOCl Citric acid 10% is more biocompatible and effective in

removing smear layer than 17% of EDTA 10% citric acid has proven to be more biocompatible than

17% EDTA-T and 17% EDTA

Mixture of tetracycline, acid, and detergent-MTAD

It is a mixture of an antibiotic, a chelating agent , and a detergent Tetracycline has many unique properties of low pH and thus can act

as a calcium chelator and cause enamel and root surface demineralization 

MTAD is a mixture of 3% doxycycline, 4.25% citric acid, and detergent (Tween-80)

Citric acid eliminates the smear layer, allowing the doxycycline to pass into the dentinal tubules and cause an antibacterial effect.

The protocol for clinical use of MTAD is 1.3% NaOCl for 20 min followed by 5 min application of MTAD. 

A final rinse with MTAD might have a negative effect on the bonding ability of both resin-based and calcium hydroxide–based sealers due to the precipitate formation

There may be a risk of development of bacterial resistance, intrinsic staining of dentine, and sensitivity of tooth.

Torabinejad et al. showed that the effectiveness of the MTAD was enhanced when low concentration of NaOCl is used as an intracanal irrigant before the use of MTAD as a final rinse. MTAD does not seem to significantly change the structure of the dentinal tubules

MTAD can be a useful irrigant due to its antimicrobial property, less cytotoxic, but its effectiveness against fungi and value in the apical one third need to be assessed further.

Tetraclean

Tetraclean is similar to MTAD, the only difference being the addition of doxycycline-50 mg/ml-(at a lower concentration than in MTAD), and a detergent (polypropylene glycol).

It is effective against both anaerobic and facultative bacteria.  It is able to eliminate microorganisms and smear layer in

dentinal tubules of infected root canals with a final 5-min rinse It removes the smear layer and opens up the dentinal tubule

orifices. It has shown low surface tension which allows better

penetration of the solution into the dentinal tubule.   In vitro studies have proved that Tetraclean is more efficient

than MTAD against E. faecalis.

Maleic acid

Maleic acid is a mild organic acid used as an acid conditioner in adhesive dentistry at 5-7% concentration.

Final irrigation with 7% of maleic acid is more efficient than 17% of EDTA in the removal of smear layer from the apical third of the root canal system, which is a crucial area for disinfection.

7% of maleic acid produces maximum surface roughness on root canal walls as compared to 17% of EDTA.

This surface roughness provides an important role in micromechanical bonding of resin sealers.

 Bis-dequalinium Acetate

BDA, a dequalinium compound and an oxine derivative with the trade name Salvizol has been shown to remove the smear layer throughout the canal, even in the apical third. 

 BDA is well-tolerated by periodontal tissues and has a low surface tension allowing good penetration.

It is considered less toxic than NaOCl and can be used as a root canal dressing.

Salvizol (Ravens Gmbh, Konstanz, Germany) is a commercial brand of 0.5% BDA and possesses the combined actions of chelation and organic debridement.

Triclosan and Gantrez®

Triclosan is a broad spectrum antimicrobial agent, active against gram-positive and gram-negative bacteria as well as some fungi and viruses

Nudera et al evaluated the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of triclosan and triclosan with Gantrez® against P intermedia, F nucleatum, A naeslundii, P gingivalis, and E faecalis.

HEBP (1-hydroxyethylidene- 1, 1-bisphosphonate), also known as etidronic acid or etidronate, has been proposed as a potential alternative to EDTA or citric acid because this agent shows no short-term reactivity with NaOCl.

Chlorine dioxide-Chlorine dioxide (ClO 2) is chemically similar to chlorine or hypochlorite, the familiar household bleach. An In vitro study compared organic tissue dissolution capacity of NaOCl and ClO2. It was concluded that ClO2and NaOCl are equally efficient for dissolving organic tissue

Photo-activated Disinfection 

PAD is the placement of a dye (toluidine blue or methylene blue) into the root canals which is then activated by the laser radiation emitted from a low power (100 mW) laser device, causing interference with the microbial cell walls and bacterial death. 

 After normal irrigation, the canals are washed with sterile water, and they are dried by sterilized paper points before the application of the PAD solution into the canals.

The photosensitizer molecules will attach to the membrane of the microorganisms and the irradiation with a precise wavelength coordinated to the absorption of the photosensitizer will form singlet oxygen which causes cell wall rupture and death of the microbes.

The benefit of PAD is that the dye is only poisonous to bacteria, and there are no side effects to adjacent tissues.

ozone

It occurs in the environment either in gaseous form or as ozonated water.

 It is an antiseptic, powerful oxidant, and antibacterial agent. It is a strong oxidizer of cell walls and the cytoplasmic

membranes of microorganisms, making it a bactericidal, antiviral, and antifungal agent

 Electronically Activated Water  EAW is also recognized as oxidative potential water. It is an electrolyzed saline solution and usually utilized to remove

the microbial contamination and biofilm It is able to disturb biofilms by reducing the adhering capability of

bacteria to the canal walls by generating a negative isotonic pressure. 

Herbal Irrigants

Triphala Triphala consists of dried and powdered fruits of three

medicinal plants Terminalia bellerica, Terminalia chebula, and Emblica officinalis.

Triphala achieved 100% killing of E. faecalis at 6 min. Triphala contains fruits that are rich in citric acid, which

may aid in removal of the smear layer.  The major advantages of using herbal alternatives are easy

availability, cost-effectiveness, longer shelf life, low toxicity, and lack of microbial resistance

Green tea Green tea polyphenols, the traditional drink of Japan and China is

prepared from the young shoots of the tea plant Camellia sinensis Green tea polyphenols showed statistically significant antibacterial

activity against E faecalis biofilm formed on tooth substrate. It takes 6 min to achieve 100% killing of E faecalis Morinda citrifolia juice Morinda citrifolia juice (MCJ) has a broad range of therapeutic

effects, including antibacterial, antiviral, antifungal, antitumor, antihelmintic, analgesic, hypotensive, anti-inflammatory, and immune-enhancing effects.

MCJ is a biocompatible antioxidant MCJ contains the antibacterial compounds L-asperuloside and

alizarin

Azadirachta indica

Azadirachta indica , commonly known as Neem, is an evergreen tree, cultivated in several parts of the Indian subcontinent.

Every part of the tree is used as traditional medicine for the household remedy against various human ailments, from the ancient period. 

 Neem has been proved to be effective against E. faecalis and C. albicans. Its antioxidant and antimicrobial properties makes it a potential agent for root canal irrigation as an alternative to sodium hypochlorite