Role of Irrigants in Endodontics

Irrigation is a key part of successful root canal treatment as it fulfi ls several important mechanical, chemical and (micro) biological functions including the healing of periapical tissues. It is the only way to reach and impact those areas of the root canal wall which are not touched by mechanical instrumentation. The initial and primary endodontic treatment (rootcanal treatment) goal must be to optimize root canal disinfection and to prevent reinfection. All over the years many materials have been used to serve as endodontic irrigants particularly sodium hypochloride and EDTA. However there are also other solutions available which can be used for the purpose of irrigation. So, in this article we will narrate different types of irrigating solutions with their specifi cs, requirements, which can be used in future endodontic practice, and their advantages and limitations. Review Article Role of Irrigants in Endodontics Prabjot Kaur* Lecturer, Department of Conservative Dentistry and Endodontics, Desh Bhagat Dental College and Hospital, Mandi Gobindgarh, Punjab, India Received: 30 November, 2020 Accepted: 07 December, 2020 Published: 09 December, 2020 *Corresponding author: Dr. Prabjot Kaur, Department of Conservative Dentistry and Endodontics, Desh Bhagat Dental College and Hospital, Mandi Gobindgarh, Punjab, India, E-mail: ORCID: https://orcid.org/0000-0001-7870-9552


Introduction
The main cause of pulpal and periapical diseases are different living and nonliving irritants. Then onliving irritants include the mechanical, thermal and chemical irritants. The living irritants include different types of microorganisms such as bacteria, yeasts and viruses. When different pathological changes start to occur within dental pulp, the space within canal of root acquires the calibrerto harbour irritants including various species of bacteria, their toxins and byproducts.
Investigations in animals and patients have shown that pulpal and/or periradicular diseases cannot develop without the presence of bacteria [1,2]. The greater test for irrigation might be the regions immaculate by the fi les, for example, fi ns, isthmuses and enormous lateral canals [3]. Additionally, enormous territories in the oval and fl at canals may remain untouched notwithstanding careful instrumentation and those zones contain tissue leftovers and biofi lms that just can be taken out by substance implies utilizing irrigation system.
The apical root canal poses a specifi c challenge to irrigation as the balance between safety and effectiveness is particularly important in this area.
There is no single irrigating solution that alone suffi ciently covers all of the functions required from an irrigant. Optimal irrigation is based on the combined use of 2 or several irrigating solutions, in a specifi c sequence, to predictably obtain the goals of safe and effective irrigation. Irrigants have traditionally been delivered into the root-canal space using syringes and metal needles of different size and tip design [4]. Clinical experience and research have shown, however, that the classic approach typically results in ineffective irrigation, particularly in peripheral areas such as anastomoses between canals, fi ns, and the most apical part of the main root canal. Therefore, many of the compounds used for irrigation have been chemically modifi ed and several mechanical devices have been developed to improve the penetration and effectiveness of irrigation. This article summarizes the chemistry, biology, and procedures for safe and effi cient irrigation and provides cutting-edge information on the most recent developments [4]. So, every effort should be made to eradicate infections during the root canal treatment. Thus in this paper we will discuss about the pros and cons of various endodontic irrigants.

Goals of irrigation
Irrigation has a central role in endodontic treatment.
During and after the process of instrumentation, the irrigants administers the removal of microorganisms, tissue remnants, and dentin chips from the root canal through a fl ushing mechanism. Different irrigants can help prevent packing of the hard and soft tissue in the apical root canal and extrusion of infected material into the periapical area. Most of the irrigants dissolve organic or inorganic tissue within the root canal.
Besides, different other irrigating solutions have antimicrobial action and effectively and decimate microbes and yeasts when presented in direct contact with the microorganisms. A few irrigating system likewise have cytotoxic potential, and they can cause serious torment in the event that they obtain entrance into the periapical tissues. Utilizing a blend of irrigants in the right grouping adds to a fruitful treatment outcome [5].
Classifi cation [6] Based on mechanism of action the irrigantsare classifi ed into nonbactericidal and bactericidal irrigants.  War I utilized for purifi cation of open or contaminated injuries, later in 1917, Barret spread the utilization of Dakin arrangement in dentistry, especially for root canal irrigation system. Dr. Blass was one among the pioneers who utilized 5% sodium hypochlorite (chlorinated soda) as organic solvent and a potent germicide.
The usage of 5% sodium hypochlorite for preparation of root canal in tooth with necrotic pulps was described by Walker. Lewis in 1954, focussed on the use of sodium hypochlorite with commercial brand-name Clorox, due to the fact that this product contained 5.25% available chlorine concentration. Shih in 1970 studied in vitro antibacterial action of 5.25% sodium hypochlorite on E. faecalis and S. Aureus [7,8].

Mechanism of action
Scheme 2: Amino acid neutralizationreaction.
Aminoacid Hypochlorousacid Chloramine Water The above three schemes of reactions that occur in the presence of microorganisms and organic tissue lead to the antimicrobial effect and tissue dissolution process.
Temperature: Various studies have showed that temperature rise of 25°C increased NaOCl effi cacy by 100 times. It suggest that the capacity of 1% of NaOCl at 45°C to dissolve pulp tissue is found to be equal to that of a 5.25% of the solution at20°C.

Ultrasonic agitation
This procedure uses mostly ISO no. 15 in canals fi lled with all safety measures must be attempted to forestall such mishap [12,13].

Adverse effect
Recently, it has been shown by in vitro studies that longterm exposure of dentin to a high concentration sodium hypochlorite can have a detrimental effect on dentin elasticity and fl exural strength. Although there are no clinical data on this phenomenon, it raises the question of whether hypochlorite in some situations may increase the risk of vertical root fracture [12,13].

Edta (Ethylenediamine Tetraacetic Acid)
Complete cleaning of the root canal requires the combined use of organic and inorganic tissue-dissolving irrigants. As Germany developed its own chelating material in the mid 1930's. The synthetic substance they invented was EDTA (Ethylene-diamine-tetra-acetate). Different chelating agents were brought into endodontics as a guide for the preparation of narrow and calcifi ed root canals [14]. Nowadays, EDTA is mainly synthesized from ethylenediamine (1,2-diaminoethane), formaldehyde (methanal), andsodiumcyanide [15]. This irrigant removes bacterial surface proteins by combining with metal ions from the cell envelope leading to bacterial death. When all available ions have been bound no further dissolution takes place, thus is self-limiting [14]. The addition of a quaternary ammonium bromide i.e. Cetavlon which increases the action of EDTA by decreasing its surface tension. This combination is called EDTAC which is effective in removal of smear layer and increasing the diameter of opened dentintubules [16].

CHX (Chlorhexidinedigluconate)
CHX is antimicrobial, and this effect is due to its positive charge, which is attracted to the negatively charged bacterial cell wall and increases the permeability of bacterial contents.

MTAD (Mixture of Tetracycline, Acid Anddetergent)
It was introduced as an alternative to EDTA by Torabinejad, et al. in order to remove smear layer. It is a combination of 3% doxycycline, 4.25% citric acid and detergent-Tween 80. It has a combined antibacterial chelating properties, however, its antibacterial activity might be inhibited by the buffering effect of dentin and the serum albumin which present in the root canal. The mechanism of action is completed when, the CA removes the smear layer that allows the doxycycline to enter the dentinal tubules and cause an antibacterial effect. It is advised that an initial irrigation for 20 min with 1.3% NaOCl should be done then it should be followed by a 5-min fi nal rinse with MTAD. The disadvantage is that they do not dissolve organic tissue and are thus uses at the end of chemomechanical preparation following sodium hypochloride [19,20].

H 2 O 2 (Hydrogenperoxide)
It is a clear odourless liquid and has been widely used in dentistry. It is highly unstable compound that decomposes by heat and light. It's mechanism of action is completed by peroxide is toxic to the tissues, concentrations from 1-30% are being used in dentistry and only 3-5% is preferred for endodontic treatments. Its combination with NaOCl have been proven to be less effective as irrigating solutions as compared to whenused individually, due to a chemical reaction that results in the release of oxygen. The disadvatage of rapid nascent oxygen production can also be a complication when it reacts with blood and pulp debris and causes a pressure build up which may result in severe pain [21,22].

Iodinecompounds
These are bactericidal,virucidal, fungicidal, tuberculocidal and sporicidal. Mostly 2% iodine in 4% potassium iodide (IPI) has been used in endodontics. This combination has shown low toxicity and has a decreased tendency to stain dentine.
The main advantage of Iodine is that 2% of preparations have shown to be lesspoisonous, less irritating and rapidly reduces the bacterial load than Formocresol, Camphorated Monochlorophenol (FMCP) and Cresatin.
Despite its antimicrobial effect, iodine is a highly potent allergen thereby increasing a risk for allergic reactions [23].

Citric Acid (CA)
It is easily available in the market and is used in concentrations ranging from 1% to 50%. Few studies suggested the use of 10% citric acid as a fi nal irrigation solution which yielded very good results in terms of smear layer removal. It has shown slightly better performance than EDTA at similar concentrations, although both solutions are highly effective in removing the smear layer from root canal walls. Various studies have showed the cytotoxicity of different chelators and in comparison 10% citric acid solution had proven to be more biocompatible than 17% EDTA . In other study, a 25% CA solution failed to destroy Enterococcus faecalis biofi lms [24,25].

Maleic Acid (MA)
MA is a mild organic acid which is used to roughen the surfaces of enamel and dentin in adhesive dentistry. It functions by removing the smear layer effectively at concentrations of 5% and 7%. Additionally, when used at concentrations of 10% or higher, it causes demineralization and erosion of the root canal wall. A study done by Ballal et al.provedthat 7% malic acid application for 1 minute as fi nal irrigant removed smear layer more effectively than 1 minute irrigation with 17% EDTA in the apical third canal. However, before theendodontic use, the effects of it on periapical tissues,appropriate usage techniques must be investigated [26,27].

Tetraclean
It is similar to MTAD, the difference is due to the addition of doxycycline-50 mg/ml and a detergent (polypropylene glycol).
It is effective against both facultative and anaerobic bacteria.
And removes the smear layer and opens up the dentinal tubule orifi ces. It shows low surface tension that allows the better penetration of the solution into the dentinal tubule.
Various in-vitro studies have proved that Tetraclean is more effi cient than MTAD against E. Faecalis [28,29].

Herbalirrigants [30]
Triphala: It consists of dried and powdered fruits of three medicinal plants. Terminaliabellerica,Emblicaoffi cinalis and Terminaliachebula. This combination achieved 100% killing of E. faecalis at 6 min. Triphala contains fruits that are rich in citric acid, which aids in removal of the smear layer.
Green tea: It's polyphenols showed a statistically signifi cant antibacterial activity against E. faecalis biofi lm formed on tooth substrate. It also takes 6 min to achieve 100% killing of E. faecalis.

Morinda Citrifoliajuice
MCJ has wide range of therapeutic effects such as antibacterial, antifungal,antiviral,analgesic, antitumor, antihelmintic, anti-infl ammatory, hypotensive, and immune-enhancing effects. It is biocompatible antioxidant which do not cause severe injuries to patients as can be caused by NaOCl accidents. New developments such as CFD and mechanical devices will help to advance safe and effective irrigation.