R E V I E W A R T I C L E
Irrigants in endodontic treatment
Sajedeh Ghorbanzadeh1, Sara Arab Loodaricheh2, Sara Samizade3, Saeede Zadsirjan1
1Department of Endodontics, Dental School of Shahid Beheshti University of Medical Sciences, Tehran, Iran, 2Department of Oral Medicine, Dental School
(Faculty), Khorasgan Branch, Islamic Azad University, Isfahan, Iran, 3Department of Periodontics, School of Dentistry, Mashhad University of Medical Sciences,
Mashhad, Iran
Abstract
The aim of root canal treatment is to remove virulence factors from this system. Cleaning and shaping of the root canal are at the outmost importance in endodontic treatment. Canal irrigation during the process of cleaning and shaping can lead to the elimination of microorganism, which are not removable through physical methods. Moreover, during the preparation of root canal, manually and by rotary instruments, the smear layer is created that must be eliminated by irrigants. In the present review article, irrigants were investigated in terms of chemical and biological features and their eff ective and safe ways of usage, along with some information that have been proposed on recent developments of root canal solutions. Furthermore, this topic has been studied regarding its eff ect on microorganisms and smear layer. In the present article, a review has been conducted through libraries, PubMed, ISI Web of science, Scopus websites, and Google using keywords such as endodontic treatment, intracanal irrigant, anti-bacterial, chlorhexidine, smear layer, and sodium hypochlorite. Diff erent materials have been introduced as root canal irrigants. Although sodium hypochlorite is the most common material used in the endodontic treatment against root canal microorganism, it has certain disadvantages and limitations and could not entirely remove the smear layer. Therefore, there is no irrigant that is capable of providing all the features of an appropriate irrigant individually. To remove the smear layer, ethylene diamine tetra acetic acid is required as the fi nal rinse. High-density sodium hypochlorite (NaOCl) is more eff ective than 1 and 2% solutions. In order to eliminate the microorganisms of the root canal and the smear layer, it is suggested to use two or more detergents with a proper frequency. Using chlorhexidine as the fi nal detergent creates a lasting impact.
Keywords: Anti-bacterial materials, chlorhexidine, intracanal irrigant, root canal treatment, smear layer, sodium hypochlorite
Correspondence
Sara Arab Loodaricheh, Department of Oral Medicine, Dental School (Faculty), Khorasgan Branch, Islamic Azad University, Isfahan, Iran. Tel.: +98-31-35354053, Fax: +98-31-35354053. E-mail: [email protected]
Received 12 May 2015; Accepted 14 June 2015
doi: 10.15713/ins.ijcdmr.77
How to cite the article: Sajedeh Ghorbanzadeh, Sara Arab Loodaricheh, Sara Samizade, Saeede Zadsirjan, “Irrigants in endodontic treatment,” Int J Contemp Dent Med Rev, vol.2015, Article ID: 030515, 2015. doi: 10.15713/ins. ijcdmr.77
Introduction
The success of endodontic treatment depends on the elimination of the existing bacteria in root canal system and preventing their regrowth.[1] Removing debris, biofi lm, microbes, and necrotic
tissues from the root canal system is performed manually or through rotary shaping, as well as frequently canal irrigation.[2]
The main objective of preparation and canal shaping is to facilitate canal irrigation, disinfection, and obturation. However, a study conducted by the advanced technique of micro-computed tomography indicated that, some areas might remain intact during canal shaping.[3] This issue puts forward the signifi cance of using
chemical materials to clean and disinfection the root canal system. In fact, since there is no irrigant that is capable of providing all the expected characteristics, ideal irrigation is feasible by using a combination of two or more appropriate solutions through a
certain sequence.[4] Accordingly, the chemical composition of
canal irrigants has been changed to improve penetration and the eff ects of irrigation.
In this study, irrigants have been investigated in terms of chemical and biological properties and the eff ective and safe ways of application, along with data that were provided on recent developments in this fi eld.
In the present article, a review has been conducted through libraries, PubMed, ISI Web of science, Scopus websites, and Google using keywords such as endodontic treatment, intracanal irrigant, anti-bacterial, chlorhexidine, smear layer, and sodium hypochlorite.
Aim of Irrigation
perform an infl uential role in removing microorganisms, remaining tissues and dentin fragments found in the canal. In addition, irrigants prevent accumulation and compression of hard and soft tissue remnants at the apical end of the root canal and hinder the leakage of these pollutant materials toward the periapical area.[4]
Some irrigants will dissolve both organic and inorganic tissues of the root canal while others contain antibacterial and anti-microbial properties and actively kill bacteria and fungi. Some of them, however, are toxic to cells and will cause severe pain if they gain access to the periapical tissues.[5]
The resultant debris of preparing root canal manually or by rotary instruments will lead to the formation of smear layer on the root dentin, which includes organic and inorganic materials.[6]
The layer will decrease the bacterial penetration into dentinal tubules,[7,8] but enables a wide range of molecules to penetrate
inside the tubules. During months or years, the oral fl uid leaking through restoration and tooth[9] will gradually dissolve the smear
layer. Smear layer removal with Atch acid or chelating agents increases the permeability of dentine; yet there are many debates to whether remove this layer during root canal preparation. Smear layer removal might improve the seal quality between root canal fi lling materials and dentin. According to a systematic review and a meta-analysis, carried out by Shahravan et al.,[10]
removing the smear layer during root canal preparation must be performed.
An ideal irrigant must have all or some positive characteristics of a solution while being free of any detrimental properties. Positive features of a canal irrigant is as follows: Help debris removal (irrigation act), decrease tools friction during root preparation (lubricating act), dissolve the mineral tissue, penetrate the canal area, dissolve the organic materials, kill bacteria and fungi (even inside the biofi lm), do not irritate the living tissue surrounding the root, and do not weaken the tooth structure.[11,12]
Since there is no irrigant that contains all the desired properties with no detrimental factors such as cytotoxicity, none of the available options is considered as ideal; thus a combination of these products must be used in a correct sequence to achieve a successful treatment result.[13]
Sodium hypochlorite
Sodium hypochlorite is the most popular root canal irrigant that creates Na+ and OCl− ions when combined with water, which are
balanced with hypochlorous acid. Hypochlorous acid is an anti-bacterial agent that can be more eff ective than Col−.[14]
In acidic or neutral pH form of hypochlorous acid and in pH equal to 4 or more, the presence of OCl− is dominant. Therefore,
pH can aff ect the anti-bacterial property of a solution. By decomposing the vital activities of microbial cells, hypochlorous acid can lead to cell death.[15]
Sodium hypochlorite is usually used in densities between 0.5% and 6%, which is a potential anti-bacterial agent, lethal in facing with most of the bacteria. Moreover, sodium hypochlorite
is successful in dissolving organic compositions, cologne, and pulp remnants and it is the only irrigant capable of dissolving alive and dead organic tissues; hence, without this detergent, a satisfying root canal treatment seems to be diffi cult. In the case of removing smear layer, sodium hypochlorite is not applicable individually, but could aff ect the organic parts and provided a complete removal by using other irrigants such as ethylene diamine tetraacetic acid (EDTA) and citric acid.[16]
There are diff erent ideas about anti-bacterial properties of sodium hypochlorite. Some studies suggest that even in low densities, this substance is able to eliminate microorganisms within a few seconds,[14,17] while some others state that much
time is needed to reach this goal.[18,19] These diff erences can be
due to the existence of confounding factors in some studies. For example, the presence of organic materials could have negative eff ects on sodium hypochlorite activities.
Haapasalo et al.[20] has indicated that the existence of dentin
can cause a delay in the eff ects of 1% sodium hypochlorite on Enterococcus faecalis. In previous studies, however, there were diff erent amounts of organic materials in the root and pH was not under control. In fact, it can be said that when the confounding factors are limited or removed, even densities lower than 1% sodium hypochlorite can exterminate the targeted microorganisms.[18,19,21] Nevertheless, in clinical conditions, the
presence of organic materials such as infl ammatory exudate, tissue remnants, and microbial population can consume and weaken the sodium hypochlorite. Consequently, frequent irrigation and timing are important factors in the eff ectiveness of hypochlorite.[10]
Byström and Sundqvist[22] evaluated necrotic canal irrigation
which are replete with anaerobic bacteria. They indicated that, comparing with normal saline, 0.5 or 5% sodium hypochlorite with/without EDTA would lead to the reduction of considerable numbers of bacteria. Siqueira et al.[23] presented the same
results about canals that are contaminated with E. faecalis as well. All three papers found no signifi cant diff erence between anti-bacterial eff ects of low-density and high-density sodium hypochlorite. Contrary to these results, Clegg et al.[24] reported
an enormous diff erence between 3% and 6% densities of sodium hypochlorite, in terms of being applicable on bacterial biofi lm and illustrated that higher densities are more eff ective. Besides its great advantages, sodium hypochlorite has many disadvantages such as unpleasant odor and taste, toxicity, and the inability to remove the smear layer. In fact, sodium hypochlorite is only capable of dissolving the organic materials of the smear layer.[25]
Among other disadvantages of this substance is its limited anti-bacterial eff ect at “in vivo” condition, due to the inability of penetrating into the surrounding area of the root canal such as apical anastomosis, lateral canal, and dentinal tubule. In addition, the existence of non-activator materials including exudate, collagen pulp tissue, and microbial populations can interfere with the function of sodium hypochlorite and reduce its eff ectiveness.[20]
NaOCl and the eff ect of that amount on them is reduced by the biofi lm growth.[26] Ozdemir et al. indicated that a mixed
application of EDTA and NaOCl decreases the amount of root canal biofi lms, signifi cantly.[27]
In summary, sodium hypochlorite is the most signifi cant solution and the only option, which capable of dissolving the organic tissues such as biofi lm and the organic parts of the smear layer that must be used during canal preparation a complete process of cleaning the root canal system requires a irrigant that is competent to dissolve the organic and mineral materials. Although sodium hypochlorite could properly dissolve the organic substances, other irrigants must be employed to remove the smear layer and dentinal debris, completely. Citric acid, EDTA, and tetracycline contain this functionality.[28-30]
EDTA
This substance is subtle or has no eff ect on organic contents of the root, along with no anti-bacterial impact. However, there are some reports suggesting that direct and long contact of a bacterium with this substance leads to the release of bacterial proteins and subsequently cellular death. Furthermore, some studies illustrated that removing smear layer by this irrigant, increases the anti-bacterial eff ects of disinfecting factors in deeper layers.[31,32] This irrigant is mostly presented as 17%
neutral solution (disodium EDTA, pH7), but as it is stated in a study, lower densities like 10, 5, or even 1 percent could have a similar eff ect after irrigation with sodium hypochlorite, as well. Since EDTA is expensive, lower densities can be practical.[33]
Citric acid
Citric acid is accessible in various densities from 1% to 50%, although its 10% solution is more prevalent. As it is demonstrated in a study, its 10% density compared with 1%, can remove the smear layer more eff ectively.[34] By removing the smear layer, the
composition improves the anti-bacterial eff ect of topical antiseptics factors in deeper layers of the dentin. Khademi and Feizianfard[35]
claimed that EDTA is more eff ective in removing the smear layer from citric acid, especially in third apical and middle, however, both materials have removed the smear layer in third middle and cervical better than third apical. It is suggested by another study that, compared with ultrasonic 10%, citric acid has the potential to remove the smear layer in third apical more eff ectively.[36] It is
much better to use EDTA and citric acid for 2-3 min at the end of the preparation phase and after irrigation by hypochlorite.[37]
Citric acid and EDTA are available in liquid and gel form. It is probable that the limited capacity of the root canal may lead to rapid saturation of the chemical solution and decreases its eff ectiveness. In this case, using liquid products is recommended in frequent irrigation.[38,39]
Tetracycline
This substance has some specifi c properties including low pH. Its acidic property causes it to function as calcium chelator
and demineralize enamel and dentin.[40] This mineralization is
comparable by what is gained through citric acid.[41] Furthermore,
tetracycline has retention property absorbed by dentin and cementum and freed gradually;[42] however, its retention is
less than chlorhexidine.[43] In contrary to the two previous
irrigants, this substance has broad anti-bacterial (bacteriostatic) property,[44] which are used through the inhibition of protein
synthesis. In high densities, tetracycline can have a bactericidal impact. Among other specifi c properties of tetracycline is its ability to decrease the root resorption by aff ecting the osteoclast activity and reducing collagenase;[45] although tooth color is a
harmful side-eff ect of this irrigant.[46]
Chlorhexidine
Due to its anti-bacterial property, chlorhexidine digluconate has widespread disinfecting functionality in dentistry.[47,48]
This product is free of unfavorable characteristics of sodium hypochlorite such as taste, odor, and severe irritation of periapical tissues, but cannot dissolve the tissue and replace it.[49]
Chlorhexidine permeates through microbial cell walls or external membrane, hits the cytoplasm or internal membrane of the bacterium, and exterminates them. In high densities, this substance can result in the coagulation of intercellular components.[49]
Retention is one of the favorable characteristics of chlorhexidine since it sticks to the hard tissues and remains in place. However, like other antiseptic agents of root canal treatment, the functionality of chlorhexidine is contingent to pH and reduces considerably in the presence of organic materials.[50] Various studies compared the anti-bacterial eff ect
of sodium hypochlorite and chlorhexidine, indicating that there is no signifi cant diff erence between them.[51-54] Consequently,
although bacteria will be killed by chlorhexidine, biofi lm, and other organic debris might not be removed and may aff ect the quality of permanent obturation seal of the root canal.[53,54] This
problem points out the signifi cance of using hypochlorite during root canal preparation.
Accordingly, due to dentinal erosion, sodium hypochlorite cannot be used as the fi nal detergent after the EDTA, but it is not the case about 2% chlorhexidine and it can be employed for accessing the most anti-bacterial eff ect in the fi nal phase of mechanical and chemical preparation of the canal.[55] Most
studies, however, on using chlorhexidine in root canal treatment has been in the form of in vitro or in vivo and on Gram-positive organisms such as E. faecalis.[14,56] Chlorhexidine is available in
forms of the solution in water, gel, and liquid combined with surface activator factors. According to a study, chlorhexidine gel has better functionality, but the reason is not identifi ed.[57]
Regarding the current drawbacks, there are increasing evidences confi rming that 2% chlorhexidine (liquid or gel) as an irrigant is appropriate for endodontic treatment.[58]
In an in vitro study, Gomes et al.[14] compared the
and fi ve densities of NaOCl (0.5%, 1%, 2.5%, 4%, and 2.25%). All these irrigants are eff ective in killing E. faecalis, but the required impact time is diff erent. However, the required time for 0.2% liquid CHX and 2% gel CHX for increasing the negative growth is 30 and 1 min, respectively. Even if all these tested irrigants have an antibacterial function, the required time for elimination of E. faecalis depends on density and kind of irrigant. On the other hand, Siqueira et al.[59] found that, 4% NaOCl was
statistically better than 0.2% and 2% CHX against four aerobic antimicrobial Gram-negative with black pigments and four non-aerobic optional bacteria. For the fi rst time, Ferraz et al.[57]
entered 2% CHX gel as a root canal irrigant. They evaluated the CHX gel ability in disinfection of infected root canal with E. faecalis and cleaning compared with the obtained results from other tested irrigants, such as NaOCl and liquid CHX. The results indicated that, compared with other yielded outcomes from tested irrigants, the CHX gel produced more cleanly root canal level and signifi cantly had more antibacterial capabilities. Consequently, CHX gel is capable of being used as a root irrigant. Sena et al.[60] investigated the antimicrobial function of 2.5% and
5.25% NaOCl gel and 2.0% liquid CHX, as a root canal irrigant against selected single-species biofi lms. Results have shown that, mechanical simulation improved the antibacterial properties of chemicals by a biofi lm model, which is indicative of the existence agents in liquid cases, especially the 2.25% NaOCl and 2% CHX.
Iodine potassium iodide
2% and 4% iodine potassium iodide has anti-bacterial properties as well, but it is not capable of dissolving the tissues.[61] The
current iodine is less active than chlorine in sodium hypochlorite; however, it dispatches the microorganisms immediately and has bactericidal functionality. Moreover, the substance is eff ective in fungus, tuberculosis, virus, and even spirochetaes.[62] The
antiseptic role of potassium iodide iodine on the tooth surface is well-documented.[63] Similar to chlorhexidine, it can be used
at the end of mechanical and chemical preparation. According to a study, irrigation by this substance, after a typical mechanical and chemical preparation, will decrease number of negative implants in infected canals before the treatment.[64] On the other
hand, some studies have shown that irrigation by potassium iodide iodine will not cause the shaping of microorganism-free canals.[65,66] These studies consider the deactivation of
iodine compositions by dentin and necrotic tissues inside the canal, as the most signifi cant factors. Several allergic patients to these materials have emphasized on this issue to be taken into consideration.[58]
Other irrigants
Other applicable irrigants in endodontic treatment are distilled water, physiological saline, hydrogen peroxide, and urea peroxide. When used individually, these materials have no anti-bacterial activity and cannot dissolve the tissues. Hence, there is no cogent reason to use them as common irrigant. Furthermore, distilled water and saline increase the risk of infection when
used from bottles or containers that were unbolted more than once.[33,67]
Interaction between irrigants
Sodium hypochlorite and EDTA are the most prevalent irrigants. They have various features and functionalities, which cause them to be used as a composition. EDTA, however, in combination with sodium hypochlorite decreases the amount of chlorine and fi nally reduces the sodium hypochlorite activity. Accordingly, these two solutions should not be combined together.[68]
Chlorhexidine is not tissue soluble and can be mixed with sodium hypochlorite to get useful features, yet these two solutions are not soluble and the resultant becomes orange-brown sediment. Maybe the properties of this sediment and the liquid phase have not been tested so far, yet it seems that its existence made the clinical function of this composition impossible. Atomic absorption spectrophotometry has shown that iron-included sediments can be the reason of orange color.[69]
It is proved that the presence of para chlorine in sediments could have Mutagenic properties, as well.[70,71]
The combination of chlorhexidine and EDTA also creates white sediment promptly. Although the characteristics of this sediment have not been studies so far, but it seems that, the ability to remove the smear layer of EDTA is aff ected and reduced. Most dentists mix the sodium hypochlorite with hydrogen peroxide that due to the formation of excessive bubbles, it does not seem to be better than sodium hypochlorite.[51] Therefore, the combination of chlorhexidine
and Hydrogen peroxide in “in vivo” conditions leads to increase of combined anti-bacterial activity, however it appears that there are no information available on the eff ects of this combination in clinical conditions.
Synthetic Irrigants
New compositions of root irrigants include MTAD (tetracycline, citric acid, and irrigant compound) and Tetra clean, which contain antibiotic (doxycycline)[72-74] and have been developed
to remove the smear layer and create anti-bacterial property. Both comprise citric acid and irrigant, and their diff erence is in citric acid density and the type of irrigant. These two materials do not dissolve the organic tissue, and it is better to be used at the end of mechanical and chemical preparation after sodium hypochlorite. While former studies were the indicator of the appropriate anti-bacterial activity of MTAD,[75,76] recent studies
have shown that MTAD-sodium hypochlorite composition are as eff ective or less eff ective as EDTA - sodium hypochlorite.[77,78]
A comparative study between MTAD and Tetra clean has also demonstrated that the later has more anti-bacterial eff ect.[79]
in light exposure,[80] but it seems that there is no report available
of its occurrence in in vivo conditions.
Conclusion
Irrigation plays a signifi cant role in a successful root canal treatment and to achieve a proper root canal irrigation, it is crucial to have accurate information about the functionality of irrigants. Although sodium hypochlorite is the most important irrigant, yet there are no options that can provide all the required characteristics individually. Tissue dissolution and antimicrobial eff ect are two signifi cant features of irrigation. To secure the optimal results in an apical third of the canal, small, 30 gauge side-vented needles and/or negative pressure irrigation with NaOCl and EDTA are suggested.
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