2012 Iqbal - Antimicrobial Irrigants in the Endodontic Therapy

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International Journal of Health Sciences, Qassim University, Vol. 6, No. 2 (June 2012/ Rajab1433H)

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Antimicrobial Irrigants in the Endodontic TherapyAzhar IqbalAssistant Professor, Department of Conservative DentistryCollege of Dentistry, University of Al jouf

Abstract:

This paper highlights the importance of root canal disinfection. It discusses the different endodonticirrigants available and comments on how these can be used most effectively.Eliminating bacteria fromthe root canal system is an essential stage in endodontic therapy. An objective of endodontictreatment is removal of diseased tissue, elimination of bacteria from the root canal system andprevention of recontamination.

(1)Disinfection of the root canal system, as part of endodontic therapy,

by preparation and irrigation is a key in reducing the number of bacteria within the root canal andhelping to control periapical disease.

Correspondence:

Dr. Azhar Iqbal,Assistant Professor,Department of Conservative Dentistry,College of Dentistry,University of Aljouf, P. O. Box 2014,Aljouf Sakaka, Kingdom of Saudi ArabiaEmail: [email protected]

[email protected]


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IntroductionEliminating bacteria from the root canal

system is an essential stage in endodontictherapy. Practitioners should be adequately

informed and skilled in this vital aspect ofendodontics. It is desirable for endodontics tobe straightforward, cost-effective andpredictable. An objective of endodontictreatment is removal of diseased tissue,elimination of bacteria from the canal systemand prevention of recontamination.

(1)

Disinfection of the root canal system, as part ofendodontic therapy, by preparation andirrigation is key in reducing the number ofbacteria within the root canal and helping tocontrol periapical disease.

(2)Recent

guidelines,(3)

suggest single-use for allendodontic instruments. This further enforcesthe need for effective irrigation, as potentiallymost root canal therapy is likely to be carriedout over a single appointment. Additionally,greater than ever patient expectation ofsuccess makes it essential to optimize thedisinfection process during endodontictreatment. There is no evidence that directlycorrelates endodontic outcome with type ofirrigant used. Consequently, there is noagreement on which irrigant is best andwhether they should be used alone or withothers; however, it is agreed that the irrigantneeds to have a bactericidal action. It seemslogical to expect best results from an irrigantwith good disinfection power, in relation to thecausative organisms, when it is in contact withthe bacteria for an adequate time period withinthe root canal system. This means the safedelivery of an appropriate volume of irrigantfluid throughout the endodontic treatment tocomplement the preparation process prior toobturation. This paper will therefore deal withthe types and mode of action of modernendodontic irrigants.

Endodontic Microbes

Although around 500 species of bacteriahave been identified in the oral environment,only a limited number have been found tocolonize the root canal system.

(4)This might

suggest that the root canal system is a hostileand difficult environment for microbes tosurvive, and those that do survive may bedifficult to eliminate. The majority of infectivemicrobes within the root canal system arebacteria; however, fungi have also been

isolated.(5)

The microbial flora within necroticroot canals depends on the stage of theinfection.

(6)Initially, the bacterial load may be

facultative (i.e those that can use dissolved

oxygen or chemically derived oxygen forrespiration and can live under aerobic oranaerobic conditions, as time progresses (over3 months) and the consumption of oxygenwithin the root canal increases, about 90% ofthe microbial flora is obligate anaerobicbacteria (those that do not require oxygen tolive.

(6)Micro-organisms can exist within the

root canals, dentinal tubules, accessorycanals, canal

,s ramifications,apical deltas, fins

and transverse anastomoses.(7)

They are foundwithin biofilms (structured communitiesencapsulated within a self-developedpolymeric matrix and adherent to the rootsurface) or in planktonic form (drifting in a bodyof fluid). Microbes are difficult to culture and itis known that those within a biofilm are 1000times more resistant to biocides than the sameorganisms in planktonic forms.

(8)There is

disagreement on the importance of removingthe smear layer.

Endodontic Irrigants

Non-bactericidal IrrigantsSome general dental practitioners either

use saline, local anaesthetics and/or distilledwater.

(9)These have no antibacterial action

and will not reduce bacterial loadsignificantly.

(10)These irrigants may be used

frequently as they are easy to use and readilyavailable. In the case of local anaestheticsolutions, they also come in sterile packagingand can be dispensed easily through verysmall gauge needles. Additional contributingfactors for their use may be safety. Theseirrigants should have no role in managinginfected root canals. There are a number of

better irrigating solutions available which aremore appropriate for managing infected rootcanals.

Bacteriostatic/bactericidal IrrigantsThese include an array of solutions which

either kill bacteria or facilitate their death byallowing other irrigants to come into contactwith the bacteria.

Sodium hypochlorite


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Sodium hypochlorite (NaOCl) is the mostfrequently recommended and a commonlyused endodontic irrigant. Its advantages aretwo-fold; pulpal dissolution and antimicrobial

effect. NaOCl is a strong base (pH>11) andacts as an organic solvent, causing amino aciddegradation and hydrolysis through theproduction of chloramine molecules.

(11)There

is evidence to show that a decrease inmicrobial numbers is achievable when usingNaOCl for endodontic treatment of teeth withapical periodontitis.

(12)The smear layer is not

removed by NaOCl.(2)

NaOCl is available froma variety of sources from supermarkets todental supply companies and in a variety ofconcentrations. When NaOCl is chosen, itmust be remembered that the concentration

and temperature of the solution has a bearingon its effectiveness. A concentration of over0.5% is required to reduce bacterial loadsignificantly.

(13) In vitro evidence has implied

that using NaOCl at a concentration of 0.5%for 10 seconds can reduce the bacterial load ofA. naeslundi (found in untreated necrotic rootcanals) and C. albicans (found in endodonticfailure cases) to below the limit of detection. Itwas seen that a contact period of 30 minuteswas required to reduce the bacterial load of E.faecalis below the limit of detection. At aconcentration of 5.25%, 2 minutes of contactwas required to reduce the bacterial load.(14)Other studies have shown that a concentrationof 5.25% NaOCl can kill E. faecalis and C.albicans within 1530 seconds.

(2)NaOCl, at a

concentration of 1% heated to 20C, is lesseffective than that at 45C, which in turn is lesseffective than that at 60C, as more chlorine isreleased at higher temperatures. NaOCl at aconcentration of 5.25% heated to 20C is aseffective as NaOCl at a concentration of 1%heated to 45C. NaOCl at a concentration of1% heated to 60C is significantly moreeffective than 5.25% at 20C.

(15)The same

study showed that aqueous solutions of 1%,2.62% and 5.25% NaOCl heated to 21C, 45Cand 60C maintained 100% availability ofchlorine for at least 60 minutes. Stock solutionsshould be stored at low temperatures andheated chair-side when required. To achievepulpal dissolution a concentration of 1% orabove is required.

(15)There is a limited

evidence for NaOCl at a concentration of 6%being significantly better than 5.25%. However,common sense dictates that higher

concentrations will achieve reduction inbacterial load faster owing to the presence of ahigher concentration of chloramine molecules.It should also be kept in mind that the more

concentrated solutions of NaOCl are thickerand subsequently there is less wetting of thecanal walls.

(16)It has been observed that

NaOCl solutions at concentrations of 0.5%, 3%and 5% degrade the organic phase (collagen)of dentine with no loss of mineral, possiblyleading to brittleness of endodontically treatedteeth.

(14)There are significant biological toxicity

risks if NaOCl is expressed under pressure intothe periodontal ligament space. The outcomesare significantly worse the higher theconcentration. The advantage of lowerconcentrations of NaOCl heated to higher

temperatures is that, once they reach bodytemperature, the systemic toxicity should belower than that of nonheated, highconcentrations of NaOCl.

IodineIodine was introduced into endodontics in

1979 advocating the use of povidone iodine, asit was seen to be an antiseptic against a broadrange of micro-organisms, hypoallergenic, withlow toxicity and has a decreased tendency tostain dentine.

(17)Since then iodine has been

shown to be bactericidal, fungicidal,tuberculocidal, virucidal and sporicidal.(6)Thecollagen matrix in dentine can inhibit iodine.

(17)

It is thought that iodine attacks key groupproteins, nucleotides and fatty acids, leading tocell death.

(2)The advantage of iodine over the

other irrigants is that 2% preparations of IodinePotassium Iodide (IPI) used in endodontics areshown to be less irritating and toxic thanFormocresol, Camphorated Monochlorophenol(FMCP), and Cresatin.

(2,17)It is also suggested

that iodine at a concentration of 2% is faster atreducing the bacterial load than a calciumhydroxide inter-appointment dressing. 2%IPIneeds 12 hours to prevent growth of E.faecalis.

(17)

ChlorhexidineChlorhexidine (CHX) is a cationic bis-

biguanide antiseptic. Its advantages are basedon a broad spectrum of activity. CHX attacksmultiple sites at a cellular level, makingresistance less likely.

(3)CHX is a positively

charged hydrophilic and lipophilic moleculewhich interacts with phospholipids and

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lipopolysaccharides in cell membranes.Consequently, there is disruption of the cellmembranes which allows CHX molecules toenter the cell to cause intracellular toxic

effects, such as coagulation of thecytoplasm.

(15)CHX is bacteriostatic at low

concentrations and at higher concentrations isbactericidal to both gram positive and gramnegative microbes, with greater activity againstgram positive bacteria. CHX at a concentrationof 0.2% (Corsodyl, GlaxoSmithKline ConsumerHealthcare, UK) is not very bacteriocidal. CHXat a concentration of 2% (ChlorhexidineGluconate Solution, Essential Dental SystemsInc, USA) is better, although if used directlyfollowing NaOCl can cause a dark precipitate,which is difficult to remove. Hibiscrub (Regent

Medical, Bedfordshire, UK) contains 4% CHXand is a useful lubricant during endodonticprocedures. It is thought that the precipitate is,as a result of the acidbase reaction betweenNaOCl and CHX. The precipitate formed isneutral but insoluble.

(12)There is a question

mark regarding the potential health risksassociated with this precipitate. The authorsrecommend saline as an intermediate irrigant,when using both NaOCl and CHX as irrigantsin the same tooth. It has been suggested thatCHX is sporostatic but not sporocidal

(13)and

has been shown to inhibit adherence of P.gingivalis to host cells.(3) A disadvantage is thatCHX does not dissolve organic tissue. On theother hand, this contributes to the fact that it isof low toxicity to periapical tissues.

(11)

Chlorhexidine has a unique property in that ithas substantivity, i.e has a persistent residualantimicrobial action.

(3)It can theoretically

prevent microbial colonization for a period oftime after the actual medication period.However, while the dentine is absorbing CHXin the first hour, it is not yet active

(13)and the

dentine must reach a saturation point for there

to be a persistent antimicrobial effect. Somehave stated that CHX needs to be in contactwith the dentine for at least 7 days forsaturation of the dentine rather than be usedas an irrigant.

(10)CHX is unsuitable as an

interappointment dressing, as there are issuesof leakage which may increase the spaceavailable for recolonization of microbes. Likemany of the other irrigants, CHX is self limitingand antimicrobial substantivity depends uponthe number of CHX molecules available for

interaction with the dentine, and hence mustbe replenished frequently.

EDTA

Ethylene diamine tetra acetic acid (EDTA)is a synthetic amino acid and the sodium saltsof EDTA (Na2EDTA) are used in dentistry. It isoften used as a chelating agent. EDTA is notbactericidal nor bacteriostatic but inhibits thegrowth of, and eventually kills, bacteria bystarvation as metallic ions needed for growthare chelated thus are not available for use bymicro-organisms.

(12, 13)EDTA is relatively non

toxic but is slightly irritating in weak solution.EDTA at concentrations of 1517% removescalcium from dentine leaving a softened matrixof dentine. It also emulsifies soft tissue andremoves the smear layer with no deleteriouseffect to pulpal or periapical tissues.

(5)The

application of EDTA at a concentration of 17%for over 10 minutes has been shown to causeexcessive erosion of peritubular andintertubular dentine.

(4)The suggestion for

EDTA is to be in the root canal system 15minutes to achieve the desired effect.

(3,4)

EDTA, like many other irrigants, is self limiting.Frequent changing of the solution is moreeffective than one continuous application.EDTA is available in a liquid form for irrigationand a gel form for lubrication (Glyde File Prep,Dentsply-Maillefer, Ballaigues, Switzerland). Awell known alternative is Citric Acid, however,

EDTA has been shown to be a faster chelatingagent.

(6)

Hydrogen peroxideHydrogen peroxide (H2O2) is a colourless

liquid and has been used in dentistry inconcentrations varying from 1% to 30%. H2O2degrades to form water and oxygen. It is activeagainst viruses, bacteria, bacterial spores andyeasts

(16)via the production of hydroxyl free

radicals which attack proteins and DNA.

(7)

Ithas been shown that NaOCl, combined withH2O2, is no more effective against E. faecalisthan NaOCl alone

(8)however, CHX combined

with H2O2 was a better antimicrobial agentthan either one on their own.

(9)The current

evidence does not support the use of H2O2over other irrigants and it has not been shownto reduce bacterial load in canalssignificantly.

(2)There is the rare but potential

danger of effervescence with H2O2 and


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seepage into the tissues may lead to airemphysema.

(10)

Other products

AntibioticsMTAD (Mixture of Tetracycline, Acid and

Detergent) is a product with a pH of 2.15,consisting of doxycycline, citric acid and thedetergent Tween-80.

(2)MTAD has been seen

to remove the smear layer without significantlychanging the structure of the dentinal tubules,and the canals were seen to be cleaner whencompared with EDTA.

(11)MTAD was seen to

be less toxic than eugenol, 3% H2O2,Ca(OH)2 paste, 5.25% NaOCl, Peridex(a CHXmouthwash with additives) and EDTA,

(12)

however, was more toxic than NaOCl in

concentrations of 2.63%, 1.33% and 0.66%. (13)The protocol for clinical use of MTAD is 20minutes with 1.3% NaOCl followed by 5minutes of MTAD and is available fromDentsply as BioPure MTAD. Good antibacterialactivity with MTAD is reported.

(14, 15)As this

irrigant is based on a tetracycline isomer, theremay be problems with staining, resistance andsensitivity. Limited evidence is available for theuse of these compared with conventionalirrigants, such as NaOCl.Photo-activated disinfection (PAD)

PAD is the application of a dye (oftenToluidine blue) into the root canal system,followed by a laser radiationemitted from a lowpower (100 mW) laser device which activatesthe dye. Following normal irrigation, sterilewater is used to wash the canals and thecanals aredried using sterile paper points priorto introduction of the PAD solution into thecanals. The principle behind the system is thatthe photosensitizer molecules will attach to themembrane of the bacteria, and then theirradiation with a specific wavelength matchedto the absorption of the photosensitizer willlead to the production of singlet oxygen,causing rupture of the cell wall and death ofthe bacteria.

(16)The effectiveness against

endodontic pathogens depends on the power,length of exposure, absorption of light into thetissues, and tip-to-target tissue distance. Arecent in vivo study concluded that PAD offersa mean of destroying bacteria that may remainafter using conventional irrigants in endodontictherapy.

(17)The advantage is that the dye is

lethal to bacteria with no toxicity to the patient

and there are no thermal side-effects to tissuessurrounding the root.

(11)

There is no robust evidence for thistechnique.Neodymium:yttrium-aluminumgarnet

(Nd:YAG) lasers have also been used forphotothermal disinfection and it was found that,even when there was direct exposure to thelaser, all systems were not left bacteria freeand these were therefore no better thanirrigation with NaOCl.

(6)The use of a

photosensitizing agent and laser was not ableto achieve total reduction in bacterial load invitro, however, 3% NaOCl was seen to achievethis.

(8)It must be remembered that it may be

difficult to access small and curved canalspaces with lasers. These systems may alsobe expensive items to purchase.

Electronically Activated WaterElectronically Activated Water (EAW) is

also known as Oxidative Potential Water. It isessentially electrolysing saline solution and isused commonly to remove biofilms from dentalpiping and tubing. The thought is that EAW isable to disrupt biofilms as well as removing theadhering ability of microbes to canal walls bycreating a negative isotonic pressure whichdraws molecules into it. Research suggeststhat EAW with the use of ultrasound gave alarge reduction in bacterial load; however, itwas not as effective as 3% NaOCl.(9)

SummarySodium hypochlorite is still the most

effective gold standard irrigant. Unlike withsodium hypochlorite, the extrusion of iodineand chlorhexidine is thought to be moreforgiving to the soft tissues as they do notdissolve organic tissue. Chelators in liquid formare not a replacement for antimicrobial irrigantslike NaOCl. The antimicrobial properties ofchelators are low yet they can be used toremove the smear layer, increasing thepenetration of other irrigants such as NaOCland hence increasing their antimicrobialeffects.

(14)The inorganic portion of smear layer

can be removed by the use of 1517%concentrations of EDTA and the organicportion can be removed by NaOCl inconcentrations exceeding 1%. Chelators inpaste form can act as lubricants and mayreduce the risk of instrument separation. Localanaesthetic agents and saline have noantimicrobial properties. These are useful only


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as a flushing agent in non-infected teeth i.eirreversible pulpitis cases and electiveendodontic treatment. They cannot beexpected to remove and kill microbes within

the root canal system. They are also moreexpensive to purchase than sodiumhypochlorite. Dentine has a buffering capacityand is able to neutralize acids and alkalines.The organic part of dentine is able to reducethe antimicrobial effect of chlorhexidine, iodinepotassium iodide, and sodium hypochlorite. Asyet there is limited evidence of methods toovercome this problem.

ConclusionIt must be kept in mind that the effectiveness

of all irrigants has mostly been measured invitro environments. More research that relatesto endodontic success with irrigant types andmethods used is required. This paper hasdescribed the irrigants available for endodontictherapy, highlighted their method of action andexplained where they can be obtained. NaOClis probably still the best available irrigant owingto its wide antibacterial spectrum.

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10. Beltz RE, Torabinejad M, Pouresmail M.Quantitative analysis of the solubilisingaction of MTAD, sodium hypochloriteand EDTA on bovine pulp and dentine.JEndod2003; 29: 334337.

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14. Bergmans L, Moisiadis P, Teughels W,Van Meerbeek B, Quirynen M,Lambrechts P. Bactericidal effect ofNd:YAG laser irradiation on someendodontic pathogens ex vivo. IntEndodont J2006; 39: 111.

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16. Seal GJ, Ng L-Y, Spratt D, Bhatti M,Gulabivala K. An in vitro comparison ofbacterial efficacy of lethalphotosensitisation or sodium hypochloriteirrigation on Streptococcus intermediusbiofilms in root canals. Int Endodont J2002; 35: 268274.


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17. Gulabivala K, Stock CJR, Lewsey JD,Ghori S, Ng Y-L, Spratt DA. Effectivenessof electrochemically activated water as anirrigant in an infected tooth model. Int

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2012 Iqbal - Antimicrobial Irrigants in the Endodontic Therapy