The Open Dentistry Journal




ISSN: 1874-2106 ― Volume 13, 2019

Root Canal Irrigation: Chemical Agents and Plant Extracts Against Enterococcus faecalis



Letizia Borzini, Roberta Condò, Paolo De Dominicis, Adriano Casaglia*, Loredana Cerroni
Department of Clinical Science and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy

Abstract

Background:

There are various microorganisms related to intra and extra-radicular infections and many of these are involved in persistent infections. Bacterial elimination from the root canal is achieved by means of the mechanical action of instruments and irrigation as well as the antibacterial effects of the irrigating solutions. Enterococcus faecalis can frequently be isolated from root canals in cases of failed root canal treatments. Antimicrobial agents have often been developed and optimized for their activity against endodontic bacteria. An ideal root canal irrigant should be biocompatible, because of its close contact with the periodontal tissues during endodontic treatment. Sodium hypoclorite (NaOCl) is one of the most widely recommended and used endodontic irrigants but it is highly toxic to periapical tissues.

Objectives:

To analyze the literature on the chemotherapeutic agent and plant extracts studied as root canal irrigants. In particularly, the study is focused on their effect on Enterococcus faecalis.

Method:

Literature search was performed electronically in PubMed (PubMed Central, MEDLINE) for articles published in English from 1982 to April 2015. The searched keywords were “endodontic irrigants” and “Enterococcus faecalis” and “essential oil” and “plant extracts”.

Results:

Many of the studied chemotherapeutic agents and plant extracts have shown promising results in vitro.

Conclusion:

Some of the considered phytotherapic substances, could be a potential alternative to NaOCl for the biomechanical treatment of the endodontic space.

Keywords: Root canal irrigation, Phytotherapic substances, Enterococcus faecalis, Essential oil, Plant extracts.


Article Information


Identifiers and Pagination:

Year: 2016
Volume: 10
First Page: 692
Last Page: 703
Publisher Id: TODENTJ-10-692
DOI: 10.2174/1874210601610010692

Article History:

Received Date: 18/04/2016
Revision Received Date: 12/10/2016
Acceptance Date: 02/11/2016
Electronic publication date: 19/12/2016
Collection year: 2016

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open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/legalcode), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.


* Address correspondence to this author at the Department of Clinical Science and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy; Tel: +39672596377; Fax: +39672596378; E-mail: a.casaglia@tiscali.it




INTRODUCTION

In most cases where endodontic treatments prove unsuccessful, it is due to treatment procedures that have failed to meet a satisfactory standard for control and elimination of infection [1Nair PN. Pathogenesis of apical periodontitis and the causes of endodontic failures. Crit Rev Oral Biol Med 2004; 15(6): 348-81.
[http://dx.doi.org/10.1177/154411130401500604] [PMID: 15574679]
].

The need for retreatment may be attributed to either reinfection by oral bacteria or, more often, to the persistence and regrowth of microorganisms that were not eliminated during the previous treatment. Elimination of microbes from the pulpal tissue as well as in root canals is the main goal when aiming to prevent and treat pulpal and periapical lesions. Successful root canal therapy relies on the combination of proper instrumentation, disinfection and obturation of root canal [2Krause TA, Liewehr FR, Hahn CL. The antimicrobial effect of MTAD, sodium hypochlorite, doxycycline, and citric acid on Enterococcus faecalis. J Endod 2007; 33(1): 28-30.
[http://dx.doi.org/10.1016/j.joen.2006.08.011] [PMID: 17185124]
].

Employment of mechanical instrumentation is the core method for bacterial reduction in the infected root canal, but achieving bacteria-free root canals still proves to be a difficult task [3Spratt DA, Pratten J, Wilson M, Gulabivala K. An in vitro evaluation of the antimicrobial efficacy of irrigants on biofilms of root canal isolates. Int Endod J 2001; 34(4): 300-7.
[http://dx.doi.org/10.1046/j.1365-2591.2001.00392.x] [PMID: 11482142]
].

Various studies have demonstrated that mechanical preparation with hand instruments and irrigation with saline cannot predictably eliminate the bacteria from the infected root canals [4Dalton BC, Orstavik D, Phillips C, Pettiette M, Trope M. Bacterial reduction with nickel-titanium rotary instrumentation. J Endod 1998; 24(11): 763-7.
[http://dx.doi.org/10.1016/S0099-2399(98)80170-2] [PMID: 9855830]
, 5Pataky L, Iványi I, Grigár A, Fazekas A. Antimicrobial efficacy of various root canal preparation techniques: an in vitro comparative study. J Endod 2002; 28(8): 603-5.
[http://dx.doi.org/10.1097/00004770-200208000-00010] [PMID: 12184424]
].

Therefore, the current focus of interest has been the use of irrigating solutions with strong antibacterial activity as the necessary supplement to mechanical preparation.

Nowadays, most studies focus on the antimicrobial properties of the irrigating solutions, involving both forms of bacterial growth, planktonic and biofilm. However, few studies look into the residual antibacterial activity and its influence on microbial adhesion to the dentin surface [6Chávez de Paz LE, Bergenholtz G, Svensäter G. The effects of antimicrobials on endodontic biofilm bacteria. J Endod 2010; 36(1): 70-7.
[http://dx.doi.org/10.1016/j.joen.2009.09.017] [PMID: 20003938]
].

This is a relevant aspect to take into consideration because microbial adherence to the dentin is the first step in colonization, including tubule invasion, and the origin of biofilm infections.

The purpose of this paper is to give a succinct literature review of different commercially available root canal irrigants, with particular attention to their effect against E. faecalis, and the state-of-the-art irrigating solutions using plant extracts.

MATERIALS AND METHODS

The first criteria for research in PubMed/Medline were dental journals from 1982 to 2015. A first research attempt was made with the keywords “endodontic irrigants” and “Enterococcus faecalis” and it resulted in 163 articles; the second search was done with the keywords “plant extracts” and “Enterococcus faecalis” and/or “endodontic”, resulting in 15-25 articles; the third search, with the keywords “Enterococcus faecalis” and “essential oil”, resulted in 104 articles. Inclusion criteria: in vitro studies, antibacterial activity against E. faecalis, antibacterial activity of the plant extracts compared to NaOCl and/or Chlorhexidine, essential oil tested as an endodontic irrigant and/or present in more than two publications.

Endodontic Bacteria

Once the root canal is infected coronally, the infection progresses apically until bacterial products or bacteria themselves are in a position to stimulate the periapical tissues, thereby leading to apical periodontitis. The microorganisms and their products (endotoxins) are closely related to the etiology of pulpal and periapical lesions. They can cause pulp necrosis due to their persistence in the root canal system after endodontic treatment and can induce a periapical inflammatory reaction. Root canals with primary infections contain a high bacterial load, but chemo-mechanical root canal preparation has proven able to reduce bacterial counts by at least 95% [7Blome B, Braun A, Sobarzo V, Jepsen S. Molecular identification and quantification of bacteria from endodontic infections using real-time polymerase chain reaction. Oral Microbiol Immunol 2008; 23(5): 384-90.
[http://dx.doi.org/10.1111/j.1399-302X.2008.00440.x] [PMID: 18793361]
].

Endodontic infections have a polymicrobial nature, with obligate anaerobic bacteria conspicuously dominating the microbiota in primary infections. The root canal microbiota includes more than 700 different bacterial species some of which have not yet been identified at species level [8Valera MC, Silva KC, Maekawa LE, et al. Antimicrobial activity of sodium hypochlorite associated with intracanal medication for Candida albicans and Enterococcus faecalis inoculated in root canals. J Appl Oral Sci 2009; 17(6): 555-9.
[http://dx.doi.org/10.1590/S1678-77572009000600003] [PMID: 20027425]
]. In addition to bacteria, other microorganisms like yeasts can be found in root canals with pulp necrosis [9Nair PN, Sjögren U, Krey G, Kahnberg KE, Sundqvist G. Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: a long-term light and electron microscopic follow-up study. J Endod 1990; 16(12): 580-8.
[http://dx.doi.org/10.1016/S0099-2399(07)80201-9] [PMID: 2094761]
].

The main microorganisms that are isolated before a root canal treatment include Gram-negative anaerobic rods, Gram-positive anaerobic cocci, Gram-positive anaerobic and facultative rods, (saccharolytic species such as many types of Prevotella and asaccarololytic species such as Porphyromonas, furthermore Tannerella forsythia, Dialister, Fusobacterium, Spirochetes), Lactobacillus species, and Gram-positive facultative Streptococcus [10Waltimo TM, Sen BH, Meurman JH, Ørstavik D, Haapasalo MP. Yeasts in apical periodontitis. Crit Rev Oral Biol Med 2003; 14(2): 128-37.
[http://dx.doi.org/10.1177/154411130301400206] [PMID: 12764075]
].

Obligate anaerobes are generally eradicated by the endodontic treatment; on the contrary, facultative bacteria such as non-mutants Streptococci, Enterococci, and Lactobacilli are able to survive chemo-mechanical instrumentation and root canal irrigation [6Chávez de Paz LE, Bergenholtz G, Svensäter G. The effects of antimicrobials on endodontic biofilm bacteria. J Endod 2010; 36(1): 70-7.
[http://dx.doi.org/10.1016/j.joen.2009.09.017] [PMID: 20003938]
].

Enterococcus faecalis

A commonly isolated species from persistent apical periodontitis [11Stuart CH, Schwartz SA, Beeson TJ, Owatz CB. Enterococcus faecalis: its role in root canal treatment failure and current concepts in retreatment. J Endod 2006; 32(2): 93-8.
[http://dx.doi.org/10.1016/j.joen.2005.10.049] [PMID: 16427453]
-15Sedgley CM, Lennan SL, Appelbe OK. Survival of Enterococcus faecalis in root canals ex vivo. Int Endod J 2005; 38(10): 735-42.
[http://dx.doi.org/10.1111/j.1365-2591.2005.01009.x] [PMID: 16164688]
], Enterococcus faecalis is a microorganism that can tolerate extreme conditions [16Ørstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990; 6(4): 142-9.
[http://dx.doi.org/10.1111/j.1600-9657.1990.tb00409.x] [PMID: 2133305]
].

Its long-term survival in the root canal system could be a result of its ability to adhere to dentin and invade dentinal tubules [17Distel JW, Hatton JF, Gillespie MJ. Biofilm formation in medicated root canals. J Endod 2002; 28(10): 689-93.
[http://dx.doi.org/10.1097/00004770-200210000-00003] [PMID: 12398165]
, 18Zehnder M. Root canal irrigants. J Endod 2006; 32(5): 389-98.
[http://dx.doi.org/10.1016/j.joen.2005.09.014] [PMID: 16631834]
] and to form communities organized in biofilms, which may contribute to bacterial resistance and persistence after intracanal antimicrobial procedures [19Kishen A, Sum CP, Mathew S, Lim CT. Influence of irrigation regimens on the adherence of Enterococcus faecalis to root canal dentin. J Endod 2008; 34(7): 850-4.
[http://dx.doi.org/10.1016/j.joen.2008.04.006] [PMID: 18570994]
].

Pinheiro et al. found E. faecalis in 52.94% of canals with bacterial growth [20Pinheiro ET, Gomes BP, Ferraz CC, Sousa EL, Teixeira FB, Souza-Filho FJ. Microorganisms from canals of root-filled teeth with periapical lesions. Int Endod J 2003; 36(1): 1-11.
[http://dx.doi.org/10.1046/j.1365-2591.2003.00603.x] [PMID: 12656508]
]. This microorganism has demonstrated the capacity to survive in an environment in which there are available nutrients and in which commensality with other bacteria is minimal [21Sundqvist G, Figdor D, Persson S, Sjögren U. Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998; 85(1): 86-93.
[http://dx.doi.org/10.1016/S1079-2104(98)90404-8] [PMID: 9474621]
].

It is therefore probable that bacteria within dentinal tubules surviving chemo-mechanical instrumentation and intracanal medication may colonize the tubules and reinfect the obturated root canal [22Kreft B, Marre R, Schramm U, Wirth R. Aggregation substance of Enterococcus faecalis mediates adhesion to cultured renal tubular cells. Infect Immun 1992; 60(1): 25-30.
[PMID: 1729187]
].

Its pathogenicity ranges from life-threatening diseases in compromised individuals, to less severe conditions, such as infection of obturated root canals with chronic apical periodontitis. In the latter situation, the infecting organisms are partly shielded from the defense mechanisms of the body. The most-cited virulence factors of E. faecalis that may be related to endodontic infection and the peri-radicular inflammatory response are aggregation substance, surface adhesions, sex pheromones, lipoteichoic acid, extracellular superoxide production, the lytic enzymes gelatinase and hyaluronidase, and the toxin cytolysin. Each of them may be associated with various stages of an endodontic infection as well as with periapical inflammation. While some products of the bacterium may be directly linked to damage of the periradicular tissues, a large part of the tissue damage is probably mediated by the host response to the bacterium and its products [23Kayaoglu G, Ørstavik D. Virulence factors of Enterococcus faecalis: relationship to endodontic disease. Crit Rev Oral Biol Med 2004; 15(5): 308-20.
[http://dx.doi.org/10.1177/154411130401500506] [PMID: 15470268]
].

The ability of E. faecalis to tolerate or adapt to harsh environmental conditions may act as an advantage over other species. It may explain its survival in root canal infections, where nutrients are scarce and there are limited means of escape from root canal medicaments.

In in vitro studies, E. faecalis has been shown to invade dentinal tubules [16Ørstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990; 6(4): 142-9.
[http://dx.doi.org/10.1111/j.1600-9657.1990.tb00409.x] [PMID: 2133305]
, 24Akpata ES, Blechman H. Bacterial invasion of pulpal dentin wall in vitro. J Dent Res 1982; 61(2): 435-8.
[http://dx.doi.org/10.1177/00220345820610021401] [PMID: 6120188]
-26Love RM. Enterococcus faecalisa mechanism for its role in endodontic failure. Int Endod J 2001; 34(5): 399-405.
[http://dx.doi.org/10.1046/j.1365-2591.2001.00437.x] [PMID: 11482724]
] whereas not all bacteria have this ability [24Akpata ES, Blechman H. Bacterial invasion of pulpal dentin wall in vitro. J Dent Res 1982; 61(2): 435-8.
[http://dx.doi.org/10.1177/00220345820610021401] [PMID: 6120188]
]. In animal studies, where pure cultures of various bacteria were inoculated separately into root canals, E. faecalis, unlike others, was found to colonize the root canal in most cases and to survive without the support of other bacteria [27Fabricius L, Dahlén G, Holm SE, Möller AJ. Influence of combinations of oral bacteria on periapical tissues of monkeys. Scand J Dent Res 1982; 90(3): 200-6.
[PMID: 7051261]
, 28Sobrinho AP, Barros MH, Nicoli JR, et al. Experimental root canal infections in conventional and germ-free mice. J Endod 1998; 24(6): 405-8.
[http://dx.doi.org/10.1016/S0099-2399(98)80021-6] [PMID: 9693583]
].

Root Canal Irrigants

Using root canal irrigant solutions has proved to be essential in endodontic treatment as they aid in disinfecting and lubricating the root canal, flushing out debris from the canal system, and dissolving organic and inorganic tissues [29Navarro-Escobar E, González-Rodríguez MP, Ferrer-Luque CM. Cytotoxic effects of two acid solutions and 2.5% sodium hypochlorite used in endodontic therapy. Med Oral Patol Oral Cir Bucal 2010; 15(1): e90-4.
[PMID: 19680178]
].

To effectively clean and disinfect the root canal system, an irrigant should ideally: (a) have a broad antimicrobial spectrum and high efficacy, (b) be able to digest proteins and necrotic tissue, (c) prevent the formation of a smear layer during instrumentation or dissolve the latter once it has formed, (d) present low surface tension to reach areas inaccessible to the tools (dentin tubules), (e) offer long-term antibacterial effect, (f) keep dentinal debris in suspension, (g) provide a lubricating action for root canal instruments, (h) be non-antigenic, non-toxic and non-carcinogenic. In addition, it should have no adverse effects on dentin or the sealing ability of filling materials. Furthermore, it should be relatively inexpensive, convenient to apply and cause no tooth discoloration [30Berutti E, Marini R, Angeretti A. Penetration ability of different irrigants into dentinal tubules. J Endod 1997; 23(12): 725-7.
[http://dx.doi.org/10.1016/S0099-2399(97)80342-1] [PMID: 9487845]
, 31Kandaswamy D, Venkateshbabu N. Root canal irrigants. J Conserv Dent 2010; 13(4): 256-64.
[http://dx.doi.org/10.4103/0972-0707.73378] [PMID: 21217955]
].

Sodium Hypochlorite

Sodium hypochlorite (NaOCl) is one of the most widely recommended and used endodontic irrigants for its antibacterial action and its capacity to dissolve organic tissues, and it has been so for more than 70 years [18Zehnder M. Root canal irrigants. J Endod 2006; 32(5): 389-98.
[http://dx.doi.org/10.1016/j.joen.2005.09.014] [PMID: 16631834]
]. Concentrations ranging from 0.5-6% have been reported in literature, with higher concentrations having better antibacterial efficacy on Enterococcus faecalis [32Berber VB, Gomes BP, Sena NT, et al. Efficacy of various concentrations of NaOCl and instrumentation techniques in reducing Enterococcus faecalis within root canals and dentinal tubules. Int Endod J 2006; 39(1): 10-7.
[http://dx.doi.org/10.1111/j.1365-2591.2005.01038.x] [PMID: 16409323]
-34Sirtes G, Waltimo T, Schaetzle M, Zehnder M. The effects of temperature on sodium hypochlorite short-term stability, pulp dissolution capacity, and antimicrobial efficacy. J Endod 2005; 31(9): 669-71.
[http://dx.doi.org/10.1097/01.don.0000153846.62144.d2] [PMID: 16123703]
] but also presenting higher toxicity [35Carson KR, Goodell GG, McClanahan SB. Comparison of the antimicrobial activity of six irrigants on primary endodontic pathogens. J Endod 2005; 31(6): 471-3.
[http://dx.doi.org/10.1097/01.don.0000148868.72833.62] [PMID: 15917691]
-37Giardino L, Ambu E, Savoldi E, Rimondini R, Cassanelli C, Debbia EA. Comparative evaluation of antimicrobial efficacy of sodium hypochlorite, MTAD, and Tetraclean against Enterococcus faecalis biofilm. J Endod 2007; 33(7): 852-5.
[http://dx.doi.org/10.1016/j.joen.2007.02.012] [PMID: 17804328]
]. Giardino et al. evaluated the efficacy of 5.25% NaOCl and MTAD (mixture of doxycycline, citric acid, and a detergent-Tween 80) and found that only 5.25% NaOCl can successfully disgregate and remove the E. faecalis biofilm [38Liu H, Wei X, Ling J, Wang W, Huang X. Biofilm formation capability of Enterococcus faecalis cells in starvation phase and its susceptibility to sodium hypochlorite. J Endod 2010; 36(4): 630-5.
[http://dx.doi.org/10.1016/j.joen.2009.11.016] [PMID: 20307735]
]. The latter proved more resistant to the irrigant when comprised of starved cells as opposed to stationary cells, with the efficacy of the 5.25% NaOCl decreasing as the biofilm matured.

The irrigation protocol based on the alternating use of NaOCl and EDTA seems to promote the elimination of root canal E.faecalis biofilms [39Soares JA, Roque de Carvalho MA, Cunha Santos SM, et al. Effectiveness of chemomechanical preparation with alternating use of sodium hypochlorite and EDTA in eliminating intracanal Enterococcus faecalis biofilm. J Endod 2010; 36(5): 894-8.
[http://dx.doi.org/10.1016/j.joen.2010.01.002] [PMID: 20416441]
].

However, the optimal organic tissue-dissolving property of NaOCl is non selective, which means that, especially at high concentrations, this chemical agent may dissolve both vital and necrotic pulp remnants indistinguishably and be toxic to periapical tissues in case of extrusion through the apical foramen to the peri-radicular space [40Kuruvilla JR, Kamath MP. Antimicrobial activity of 2.5% sodium hypochlorite and 0.2% chlorhexidine gluconate separately and combined, as endodontic irrigants. J Endod 1998; 24(7): 472-6.
[http://dx.doi.org/10.1016/S0099-2399(98)80049-6] [PMID: 9693573]
]. Cytotoxic and genotoxic effects on human peripheral lymphocytes have in fact been observed in connection with the application of sodium hypochlorite [41Gül S, Savsar A, Tayfa Z. Cytotoxic and genotoxic effects of sodium hypochlorite on human peripheral lymphocytes in vitro. Cytotechnology 2009; 59(2): 113-9.
[http://dx.doi.org/10.1007/s10616-009-9201-4] [PMID: 19484372]
]. The allergic potential of NaOCl has already been analyzed in medical literature, but only a few cases of known hypersensitivity have been reported in dental literature [42Kaufman AY, Keila S. Hypersensitivity to sodium hypochlorite. J Endod 1989; 15(5): 224-6.
[http://dx.doi.org/10.1016/S0099-2399(89)80241-9] [PMID: 2607295]
-44Serper A, Ozbek M, Calt S. Accidental sodium hypochlorite-induced skin injury during endodontic treatment. J Endod 2004; 30(3): 180-1.
[http://dx.doi.org/10.1097/00004770-200403000-00013] [PMID: 15055439]
]. Another disadvantage of NaOCl is that it decreases the mechanical resistance of dentin [45Marending M, Paqué F, Fischer J, Zehnder M. Impact of irrigant sequence on mechanical properties of human root dentin. J Endod 2007; 33(11): 1325-8.
[http://dx.doi.org/10.1016/j.joen.2007.08.005] [PMID: 17963956]
, 46Soares CJ, Santana FR, Silva NR, Preira JC, Pereira CA. Influence of the endodontic treatment on mechanical properties of root dentin. J Endod 2007; 33(5): 603-6.
[http://dx.doi.org/10.1016/j.joen.2007.01.016] [PMID: 17437882]
] by causing deterioration of collagen and proteoglycans [47Chivatxaranukul P, Dashper SG, Messer HH. Dentinal tubule invasion and adherence by Enterococcus faecalis. Int Endod J 2008; 41(10): 873-82.
[http://dx.doi.org/10.1111/j.1365-2591.2008.01445.x] [PMID: 18822013]
].

Chlorhexidine

Chlorhexidine is used extensively in periodontal therapy because of its substantivity and antimicrobial effects against Gram-positive and Gram-negative organisms. For these same reasons, it is also used as a root canal irrigant and intracanal medication in endodontics. It is a relatively non-toxic, broad spectrum antimicrobial agent that offers residual action with less potential for adverse effects, thus offering a clinical advantage over sodium hypochlorite. Another benefit of choosing Chlorhexidine over NaOCl, is that the former could be used to treat patients who are hypersensitive to the latter. In fact, no adverse effects regarding the use of CHX as an irrigant or intracanal medicament have yet been published [48Gomes BP, Vianna ME, Zaia AA, Almeida JF, Souza-Filho FJ, Ferraz CC. Chlorhexidine in endodontics. Braz Dent J 2013; 24(2): 89-102.
[http://dx.doi.org/10.1590/0103-6440201302188] [PMID: 23780357]
].

Delany et al. evaluated the 0.2% Chlorhexidine gluconate on infected root canals of extracted necrotic teeth [49Delany GM, Patterson SS, Miller CH, Newton CW. The effect of chlorhexidine gluconate irrigation on the root canal flora of freshly extracted necrotic teeth. Oral Surg Oral Med Oral Pathol 1982; 53(5): 518-23.
[http://dx.doi.org/10.1016/0030-4220(82)90469-8] [PMID: 6954427]
]. Bacteriologic samples were obtained before, during, immediately after and 24 hours after instrumentation, irrigation, and medication either with Chlorhexidine gluconate or with sterile saline. There was a highly significant reduction in microorganisms in the Chlorhexidine-treated specimens after the instrumentation and irrigation procedures. Jeansonne e and White comparing 2% Chlorhexidine and 5.25% NaOCl in vitro, showed that Chlorhexidine was more effective in reducing the number of positive culture, even if the difference was not statistically significant [50Jeansonne MJ, White RR. A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants. J Endod 1994; 20(6): 276-8.
[http://dx.doi.org/10.1016/S0099-2399(06)80815-0] [PMID: 7931023]
]. Lima et al. indicated that medications containing 2% Chlorhexidine were able to eliminate biofilms of E. faecalis at 1 and 3 days of maturation [51Lima KC, Fava LR, Siqueira JF Jr. Susceptibilities of Enterococcus faecalis biofilms to some antimicrobial medications. J Endod 2001; 27(10): 616-9.
[http://dx.doi.org/10.1097/00004770-200110000-00004] [PMID: 11592490]
]. Other in vitro works using a broth dilution test have shown that 2.0% Chlorhexidine and 5.25% NaOCl have similar antimicrobial performance against all tested microorganisms [52Gomes BP, Ferraz CC, Vianna ME, Berber VB, Teixeira FB, Souza-Filho FJ. In vitro antimicrobial activity of several concentrations of sodium hypochlorite and chlorhexidine gluconate in the elimination of Enterococcus faecalis. Int Endod J 2001; 34(6): 424-8.
[http://dx.doi.org/10.1046/j.1365-2591.2001.00410.x] [PMID: 11556507]
-54Gomes BP, Vianna ME, Matsumoto CU, et al. Disinfection of gutta-percha cones with chlorhexidine and sodium hypochlorite. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005; 100(4): 512-7.
[http://dx.doi.org/10.1016/j.tripleo.2004.10.002] [PMID: 16182174]
] using the agar diffusion method. Ercan et al. [55Ercan E, Ozekinci T, Atakul F, Gül K. Antibacterial activity of 2% chlorhexidine gluconate and 5.25% sodium hypochlorite in infected root canal: in vivo study. J Endod 2004; 30(2): 84-7.
[http://dx.doi.org/10.1097/00004770-200402000-00005] [PMID: 14977302]
] evaluated in vivo the antibacterial activity of 2% Chlorhexidine as irrigating solution in infected teeth compared to NaOCl. Counting of CFU (Colony Forming Units) in samples obtained from the root canals before and after chemo-mechanical preparation showed that both Chlorhexidine gluconate and sodium hypoclorite were significantly effective to reduce the endodontic pathogens in teeth with periapical pathologies. Chlorhexidine was significantly less effective against E. faecalis biofilm compared to 6% sodium hypochlorite [33Williamson AE, Cardon JW, Drake DR. Antimicrobial susceptibility of monoculture biofilms of a clinical isolate of Enterococcus faecalis. J Endod 2009; 35(1): 95-7.
[http://dx.doi.org/10.1016/j.joen.2008.09.004] [PMID: 19084133]
].

Endo et al. in a clinical study on secondarily infected root canals with post-treatment apical periodontitis, used 2% Chlorhexidine gel for root canal irrigation [56Endo MS, Martinho FC, Zaia AA, Ferraz CC, Almeida JF, Gomes BP. Quantification of cultivable bacteria and endotoxin in post-treatment apical periodontitis before and after chemo-mechanical preparation. Eur J Clin Microbiol Infect Dis 2012; 31(10): 2575-83.
[http://dx.doi.org/10.1007/s10096-012-1598-6] [PMID: 22565224]
]. They found that chemo-mechanical preparation was more effective in reducing bacteria (99.61%) than endotoxin (60.6%). If Chlorhexidine is extruded through the apex, it does not induce pain to the patients. However, the structure of the Chlorhexidine molecules poses a systemic risk because it is likely to decompose into reactive byproducts, such as para-chloroaniline [57Basrani BR, Manek S, Sodhi RN, Fillery E, Manzur A. Interaction between sodium hypochlorite and chlorhexidine gluconate. J Endod 2007; 33(8): 966-9.
[http://dx.doi.org/10.1016/j.joen.2007.04.001] [PMID: 17878084]
].

MTAD

The poor effectiveness of sodium hypochlorite ascribed to its inactivation by dentin and collagen, has induced many researchers to analyze antibiotic-based irrigants as an alternative because of their higher penetrating power. On this basis, a new root canal irrigant known as MTAD, comprising a tetracycline isomer (doxycycline) 150mg/5ml, citric acid, and a detergent (Tween 80), has been introduced for use as a final irrigation solution. This is reported to eliminate microorganisms that are resistant to conventional root canal irrigants [58Zhang W, Torabinejad M, Li Y. Evaluation of cytotoxicity of MTAD using the MTT-tetrazolium method. J Endod 2003; 29(10): 654-7.
[http://dx.doi.org/10.1097/00004770-200310000-00010] [PMID: 14606789]
].

The antimicrobial action is not due to the doxycycline alone, but it is the result of a synergistic effect among the various components [59Neglia R, Ardizzoni A, Giardino L, et al. Comparative in vitro and ex vivo studies on the bactericidal activity of Tetraclean, a new generation endodontic irrigant, and sodium hypochlorite. New Microbiol 2008; 31(1): 57-65.
[PMID: 18437842]
]. Doxycycline is effective against clinical isolates of E. faecalis, whilst citric acid removes the smear layer and the surfactants may facilitate the penetration of the medicament. On the downside, numerous authors have showed that MTAD was unsuccessful in the disintegration and removal of E. faecalis biofilms [37Giardino L, Ambu E, Savoldi E, Rimondini R, Cassanelli C, Debbia EA. Comparative evaluation of antimicrobial efficacy of sodium hypochlorite, MTAD, and Tetraclean against Enterococcus faecalis biofilm. J Endod 2007; 33(7): 852-5.
[http://dx.doi.org/10.1016/j.joen.2007.02.012] [PMID: 17804328]
, 60Dunavant TR, Regan JD, Glickman GN, Solomon ES, Honeyman AL. Comparative evaluation of endodontic irrigants against Enterococcus faecalis biofilms. J Endod 2006; 32(6): 527-31.
[http://dx.doi.org/10.1016/j.joen.2005.09.001] [PMID: 16728243]
, 61Prabhakar J, Senthilkumar M, Priya MS, Mahalakshmi K, Sehgal PK, Sukumaran VG. Evaluation of antimicrobial efficacy of herbal alternatives (Triphala and green tea polyphenols), MTAD, and 5% sodium hypochlorite against Enterococcus faecalis biofilm formed on tooth substrate: an in vitro study. J Endod 2010; 36(1): 83-6.
[http://dx.doi.org/10.1016/j.joen.2009.09.040] [PMID: 20003940]
].

Phytotherapic Agents

An increasing number of studies have examined the activity and possible applications of new and natural substances for root canal disinfection [62Murray PE, Farber RM, Namerow KN, Kuttler S, Garcia-Godoy F. Evaluation of Morinda citrifolia as an endodontic irrigant. J Endod 2008; 34(1): 66-70.
[http://dx.doi.org/10.1016/j.joen.2007.09.016] [PMID: 18155496]
].

Phytotherapy has evolved as a science, and there has been growing interest in evaluating plant extracts with a potential therapeutic application in dentistry. Below are some of the more relevant substances that may offer a viable alternative to the leading irrigants in the field.

Uncaria tomentosa

Commonly known as “cat’s claw” because of the small curved spines on the stem at the leaf juncture, it offers an anti-inflammatory, antiviral, antibacterical, antioxidant, and immunomodulating action [63Heitzman ME, Neto CC, Winiarz E, Vaisberg AJ, Hammond GB. Ethnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae). Phytochemistry 2005; 66(1): 5-29.
[http://dx.doi.org/10.1016/j.phytochem.2004.10.022] [PMID: 15649507]
]. Its toxicity is low when used correctly, this being an important advantage of medicinal plant treatments over more conventional methods [64Santa Maria A, Lopez A, Diaz MM, et al. Evaluation of the toxicity of Uncaria tomentosa by bioassays in vitro. J Ethnopharmacol 1997; 57(3): 183-7.
[http://dx.doi.org/10.1016/S0378-8741(97)00067-6] [PMID: 9292411]
]. Herrera et al. have evaluated the antimicrobial activity of Uncaria tomentosa against E. Faecalis, S. Aureus and C. albicans [65Herrera DR, Tay LY, Rezende EC, Kozlowski VA Jr, Santos EB. In vitro antimicrobial activity of phytotherapic Uncaria tomentosa against endodontic pathogens. J Oral Sci 2010; 52(3): 473-6.
[http://dx.doi.org/10.2334/josnusd.52.473] [PMID: 20881342]
]. 2% Uncaria tomentosa gel and 2% Chlorhexidine gel had similar antimicrobical activity against S. aureus, while Chlorhexidine is more effective against E. faecalis and C. albicans.

U. Tomentosa contains triterpens, vegetal steroids and glycoides, these compounds may be related to its antimicrobial activity [66Aquino R, De Feo V, De Simone F, Pizza C, Cirino G. Plant metabolites. New compounds and anti-inflammatory activity of Uncaria tomentosa. j Nat Prod 1991; 54(2): 453-9.
[http://dx.doi.org/10.1021/np50074a016]
, 67García R, Cayunao C, Bocic R, et al. Antimicrobial activity of isopteropodine. Z Naturforsch BJ Chem Sci 2005; 60(5-6): 385-8.
[http://dx.doi.org/10.1515/znc-2005-5-603] [PMID: 16042336]
].

Apple Vinegar

The use of different chemical irrigants for smear layer removal during the root canal treatment has also been proposed, with EDTA, citric acid, maleic acid and apple vinegar offering the most interesting results. Apple vinegar has been indicated as an antiseptic agent due to its medicinal properties, with its use as an auxiliary solution in the chemo-mechanical preparation of root canals showing good results when compared to NaOCl and EDTA [68Candeiro GT, Matos IB, Costa CF, Fonteles CS, Vale MS. A comparative scanning electron microscopy evaluation of smear layer removal with apple vinegar and sodium hypochlorite associated with EDTA. J Appl Oral Sci 2011; 19(6): 639-43.
[http://dx.doi.org/10.1590/S1678-77572011000600016] [PMID: 22231000]
].

The efficacy of apple vinegar on the endodontic microbiota has been evaluated, showing a good bactericidal action against microorganism associated with endodontic irrigations, such as S. Aureus and E. Faecalis [69Estrela C, Holland R, Bernabé PF, de Souza V, Estrela CR. Antimicrobial potential of medicaments used in healing process in dogs teeth with apical periodontitis. Braz Dent J 2004; 15(3): 181-5.
[http://dx.doi.org/10.1590/S0103-64402004000300003] [PMID: 15798819]
].

Schinus terebintifolius Raddi (aroeira-da-praia) and Syderoxylum obtusifolium Roem & Schult (quixabeira)

Schinus terebintifolius Raddi extracts have been employed as an anti-inflammatory and antimicrobial agent, with studies having demonstrated that acute and subacute administrations of the substances do not produce toxic effects on Wistar rats. On the contrary, only a few researches have investigated the therapeutic potential of Syderoxylum obtusifolium Roem & Schult, which has been used as an alternative medicine in the northeast of Brazil for the treatment of oral infections [70Santos EB, Dantas GS, Santos HB, Diniz MF, Sampaio FC. Etnobotanical studies of medicinal plants for oral conditions in the municipality of João Pessoa, Brazil. (acaio n.d.). Bras Farmacogn 2009; 19: 321-4.
[http://dx.doi.org/10.1590/S0102-695X2009000200024]
].

Tests conducted through the agar well diffusion method have compared the antimicrobial activities of Schinus terebintifolius Raddi and Syderoxylum obtusifolium Roem & Schult hydroalcoholic extracts, with those of 2.5% sodium hypochlorite and of 0.12% Chlorhexidine (positive control) against Enterococcus faecalis. The antimicrobial activity of aroeira-da-praia and quixabeira hydroalcoholic extracts against Enterococcus faecalis (ATCC 29212) was evaluated at the concentrations of 100%, 50%, 25%, 12.5% and 6.25% and compared with other solutions containing 2.5% NaOCl and 0.12% Chlorhexidine. Tests were performed on agar plates after 48 hours of incubation at 37°C. All solutions tested demonstrated antimicrobial activity against Enterococcus faecalis [71Costa EM, Evangelista AP, Medeiros AC, Dametto FR, Carvalho RA. In vitro evaluation of the root canal cleaning ability of plant extracts and their antimicrobial action. Braz Oral Res 2012; 26(3): 215-21.
[http://dx.doi.org/10.1590/S1806-83242012000300006] [PMID: 22641440]
].

Propolis and Zingiber officinale

Propolis presents anti-inflammatory and antimicrobial actions [72Grange JM, Davey RW. Antibacterial properties of propolis (bee glue). J R Soc Med 1990; 83(3): 159-60.
[PMID: 2182860]
-74Oncag O, Cogulu D, Uzel A, Sorkun K. Efficacy of propolis as an intracanal medicament against Enterococcus faecalis. Gen Dent 2006; 54(5): 319-22.
[PMID: 17004565]
]. Duarte et al. showed its influence in the reduction of acid production by S. mutans in the dental biofilm, besides its inhibitory action over the F-ATPase activity of S. mutans [75Duarte S, Gregoire S, Singh AP, et al. Inhibitory effects of cranberry polyphenols on formation and acidogenicity of Streptococcus mutans biofilms. FEMS Microbiol Lett 2006; 257(1): 50-6.
[http://dx.doi.org/10.1111/j.1574-6968.2006.00147.x] [PMID: 16553831]
].

Ferreira et al. evaluated the in vitro antimicrobial activity of propolis against anaerobic bacteria, such as Prevotella nigrescens, Fusobacterium nucleatum, and Enterococcus faecalis [76Ferreira FB, Torres SA, Rosa OP, et al. Antimicrobial effect of propolis and other substances against selected endodontic pathogens. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007; 104(5): 709-16.
[http://dx.doi.org/10.1016/j.tripleo.2007.05.019] [PMID: 17964476]
]. The microbiologic analysis did not reveal differences between groups irrigated with propolis and groups treated with other intracanal medicaments such as calcium hydroxide, camphorated para-monochlorophenol, and formocresol; these results are further confirmed by other authors.

For example Valera et al. evaluated the action of propolis and intracanal medications against Escherichia coli and endotoxin [77Valera MC, da Rosa JA, Maekawa LE, et al. Action of propolis and medications against Escherichia coli and endotoxin in root canals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110(4): e70-4.
[http://dx.doi.org/10.1016/j.tripleo.2010.01.029] [PMID: 20868987]
]. A biomechanical preparation with propolis extract was able to reduce the amount of endotoxins from the root canals, yet not completely inactivating them. The real mechanism of action of propolis appears to be rather complex and some authors attribute to flavonoids the higher antimicrobial activity [72Grange JM, Davey RW. Antibacterial properties of propolis (bee glue). J R Soc Med 1990; 83(3): 159-60.
[PMID: 2182860]
, 73Koo H, Gomes BP, Rosalen PL, Ambrosano GM, Park YK, Cury JA. In vitro antimicrobial activity of propolis and Arnica montana against oral pathogens. Arch Oral Biol 2000; 45(2): 141-8.
[http://dx.doi.org/10.1016/S0003-9969(99)00117-X] [PMID: 10716618]
].

While observing the antimicrobial activity of ginger extracts on Gram-negative anaerobes Porphyromonas gingivalis, Porphyromonas endodontalis and Prevotella intermedia, it was discovered that [10Waltimo TM, Sen BH, Meurman JH, Ørstavik D, Haapasalo MP. Yeasts in apical periodontitis. Crit Rev Oral Biol Med 2003; 14(2): 128-37.
[http://dx.doi.org/10.1177/154411130301400206] [PMID: 12764075]
]-gingerol and [12Chávez De Paz LE, Dahlén G, Molander A, Möller A, Bergenholtz G. Bacteria recovered from teeth with apical periodontitis after antimicrobial endodontic treatment. Int Endod J 2003; 36(7): 500-8.
[http://dx.doi.org/10.1046/j.1365-2591.2003.00686.x] [PMID: 12823706]
]-gingerol from the ginger rhizome evidenced potent antibacterial activities in vitro against anaerobic bacteria associated with periodontitis of the human oral cavity [78Park M, Bae J, Lee DS. Antibacterial activity of [10]-gingerol and [12]-gingerol isolated from ginger rhizome against periodontal bacteria. Phytother Res 2008; 22(11): 1446-9.
[http://dx.doi.org/10.1002/ptr.2473] [PMID: 18814211]
]. Maekawa et al. have evaluated the effectiveness of glycole propolis and ginger extract, calcium hydroxide and Chlorhexidine alone and in combination as intermediate canal medication, on extracted teeth after contaminations with Candida albicans, Enterococcus faecalis and Escherichia coli [79Maekawa LE, Valera MC, Oliveira LD, Carvalho CA, Camargo CH, Jorge AO. Effect of Zingiber officinale and propolis on microorganisms and endotoxins in root canals. J Appl Oral Sci 2013; 21(1): 25-31.
[http://dx.doi.org/10.1590/1678-7757201302129] [PMID: 23559108]
]. While all medications were able to eliminate the microorganisms in the root canals and reduce their amount of endotoxins, calcium hydroxide proved more effective in neutralizing endotoxins and less effective against C. albicans and E. faecalis. Instead, the effect of Ginger extracts on E. faecalis during biomechanical instrumentation on extracted teeth, was statistically similar to 2.5% NaOCl and 2% Chlorhexidine [80Valera MC, Maekawa LE, de Oliveira LD, Jorge AO, Shygei É, Carvalho CA. In vitro antimicrobial activity of auxiliary chemical substances and natural extracts on Candida albicans and Enterococcus faecalis in root canals. J Appl Oral Sci 2013; 21(2): 118-23.
[http://dx.doi.org/10.1590/1678-7757201302135] [PMID: 23739849]
].

Castor Oil Detergent (Ricinus communis)

Castor oil detergent has shown antimicrobial activity and biocompatibility, non-toxic results and detergent properties which are important requirements for an irrigant solution [81Camargo SE, Rode SdeM, do Prado RF, Carvalho YR, Camargo CH. Subcutaneous tissue reaction to castor oil bean and calcium hydroxide in rats. J Appl Oral Sci 2010; 18(3): 273-8.
[http://dx.doi.org/10.1590/S1678-77572010000300014] [PMID: 20857007]
]. Endodontic irrigation with castor oil extract is capable of removing debris, showing similar results to 1% NaOCl [82Meneghin MP, Nomelini SM, Sousa-Neto MD, Marchesan MA, França SC, dos Santos HS. Morphologic and morphometric analysis of the root canal apical third cleaning after biomechanical preparation using 3.3% Ricinus communis detergent and 1% NaOCl as irrigating solutions. J Appl Oral Sci 2006; 14(3): 178-82.
[http://dx.doi.org/10.1590/S1678-77572006000300006] [PMID: 19089069]
]. Root canal irrigation with castor oil reduces the number of Escherichia coli [83Valera MC, Maekawa LE, Chung A, et al. Effectiveness of castor oil extract on Escherichia coli and its endotoxins in root canals. Gen Dent 2012; 60(4): e204-9.
[PMID: 22782052]
] and E. faecalis [81Camargo SE, Rode SdeM, do Prado RF, Carvalho YR, Camargo CH. Subcutaneous tissue reaction to castor oil bean and calcium hydroxide in rats. J Appl Oral Sci 2010; 18(3): 273-8.
[http://dx.doi.org/10.1590/S1678-77572010000300014] [PMID: 20857007]
] during biomechanical preparation.

Essential Oils

Essential oils obtained from plants which have been known and used for centuries (spices, medicinal and aromatic plants) are increasingly tested for their antibacterial and antifungal activity. The antimicrobial activity of essential oils is strictly connected to their chemical composition, which is influenced by numerous factors including (but not limited to) the provenance of the plant, the part of plant used, the stage of plant development, climatic and growth condition (temperature, soil, fertilizers, etc.) as well as distillation and storage conditions. The mechanism of essential oil action towards microorganisms is complex and the common opinion is that the antibacterial action depends on their hydrophilic or lipophilic character. Terpenoids are an example of lipid soluble agents which affect the function of membrane-catalyzed enzymes, for instance their action on respiratory pathways. Certain components of essential oils can act as uncouplers, which interfere with proton translocation over a membrane vesicle and subsequently interrupt ADP phosphorylation (primary energy metabolism). Specific terpenoids with functional groups, such as phenolic alcohols or aldehydes, also interfere with membrane-integrated or associated enzyme proteins, stopping their production or activity [84Knobloch K, Pauli A, Iberl B, Weigand H, Weis NJ. Antibacterial and antifungal properties of essential oil components. Essent Oil Res 1989; 1: 119-28.
[http://dx.doi.org/10.1080/10412905.1989.9697767]
].

The mode of action of antimicrobial agents also depends on the type of microorganisms and is mainly related to their cell wall structure and the outer membrane arrangement. The susceptibility of a microorganism to essential oils depends, first of all, on the properties of the essential oil and the microorganism itself. Some general rules have been set, which enable us sometimes to predict the results of experiments. However, considering the specificity of both the microorganism and the essential oil, separate experiments for each system should be undertaken [85Kalemba D, Kunicka A. Antibacterial and antifungal properties of essential oils. Curr Med Chem 2003; 10(10): 813-29.
[http://dx.doi.org/10.2174/0929867033457719] [PMID: 12678685]
].

The antimicrobial property of essential oils from plants was used empirically for centuries, but only recently it has been studied scientifically. Dormans and Deans evaluated the antibacterial activity against 25 different genera of bacteria, all of which had a degree of sensitivity to essential oils tested [86Dorman HJ, Deans SG. Antimicrobial agents from plants: antibacterial activity of plant volatile oils. J Appl Microbiol 2000; 88(2): 308-16.
[http://dx.doi.org/10.1046/j.1365-2672.2000.00969.x] [PMID: 10736000]
]. Oils with higher activity were thyme, oregano and cloves.

Clove oil offers antibacterial and antifungal actions, and is used as an antiseptic in oral infections [87Meeker HG, Linke HA. The antibacterial action of eugenol, thyme oil, and related essential oils used in dentistry. Compendium 1988; 9(1): 32-, 34-35, 38 passim.
[PMID: 3278805]
, 88Shapiro S, Meier A, Guggenheim B. The antimicrobial activity of essential oils and essential oil components towards oral bacteria. Oral Microbiol Immunol 1994; 9(4): 202-8.
[http://dx.doi.org/10.1111/j.1399-302X.1994.tb00059.x] [PMID: 7478759]
]. The high levels of eugenol in clove essential oil are responsible for its strong antimicrobial activity, with its phenolic compound being able to denature protein and react with cell membranes’ phospholipids changing their permeability and inhibiting Gram-negative and Gram-positive bacteria [89Chaieb K, Hajlaoui H, Zmantar T, et al. The chemical composition and biological activity of clove essential oil, Eugenia caryophyllata (Syzigium aromaticum L. Myrtaceae): a short review. Phytother Res 2007; 21(6): 501-6.
[http://dx.doi.org/10.1002/ptr.2124] [PMID: 17380552]
]. Clove essential oil can be considered as a potential antimicrobial agent for external use because it is not inactivated by dilution or affected by organic matter [90Nuñez L, Aquino MD. Microbicide activity of clove essential oil (Eugenia caryophyllata). Braz J Microbiol 2012; 43(4): 1255-60.
[http://dx.doi.org/10.1590/S1517-83822012000400003] [PMID: 24031950]
].

Another essential oil worthy of mention is Cupressus lusitanica Mill, which is commonly used to treat hemorrhoids, rheumatism, whooping cough and skin infections [91Duke J. Phytochemical Database (Phytochem DB) Beltsville Agricultural Research Center. Beltsville, MD: USDA-ARS NGRL, 2004.] and it is rich in α-pinene and δ-3-carene [92Adams RP, Zanoni TA, Lara A, Barrero AF, Cool LG. Comparison among Cupressus arizonica Greene, Cupressus benthamii Endl., Cupressus lindleyi Klotz. Ex Endl. And Cupressus lusitanica Mill. using leaf essential oils and DNA finger printing. J Essent Oil Res 1997; 9: 303-9.
[http://dx.doi.org/10.1080/10412905.1997.10554249]
]. The MIC value of oil for E. faecalis (ATCC10541) ranged from 1.25 (10% v/v) compared to a 15.62 μg/ml of the reference compound (gentamicin); the lethal dose of this extract was evaluated at 6.33 g/Kg bodyweight on male Wistar albino rats [93Teke GN, Elisée KN, Roger KJ. Chemical composition, antimicrobial properties and toxicity evaluation of the essential oil of Cupressus lusitanica Mill. leaves from Cameroon. BMC Complement Altern Med 2013; 13: 130-8.
[http://dx.doi.org/10.1186/1472-6882-13-130] [PMID: 23758765]
].

Also exhibiting satisfactory antifungal, antibacterial and antioxidant activities [94Zomorodian K, Moein M, Goeini Lori Z, et al. Chemical composition and antimicrobial activities of the essential oil from Myrtus communis leaves. J Essential Oil Bear Plants 2013; 16: 76-84.
[http://dx.doi.org/10.1080/0972060X.2013.764183]
, 95Rasooli I, Moosavi ML, Rezaei MB, Jaimand K. Susceptibility of microorganisms to Myrtus communis L. essential oil and its chemical composition. J Agric Sci Technol 2002; 4: 127-33.], Myrtus communis is an evergreen small tree with a wide distribution in Iran and other tropical regions of the world. Nabavizadeh et al. have found that the Myrtus communis essential oil inhibited the growth of E. faecalis and S. aureus with a lower MIC compared to NaOCl; the main constituents of Myrtus essential oil were 1,8-cineole, α-pinene and linalool [96Nabavizadeh M, Abbaszadegan A, Gholami A, et al. Chemical constituent and antimicrobial effect of essential oil from Myrtus communis leaves on microorganisms involved in persistent endodontic infection compared to two common endodontic irrigants: An in vitro study. J Conserv Dent 2014; 17(5): 449-53.
[http://dx.doi.org/10.4103/0972-0707.139836] [PMID: 25298646]
].

RESULTS

An ideal endodontic irrigant should possess some essential properties already covered by many authors, but to this date there is no such substance known to researchers. Some endodontic irrigants do show good antimicrobial activity, however they might result toxic; others dissolve the smear layer, but do not efficiently disinfect the root canal system.

E. faecalis is considered the principal pathogen related to endodontic infections.

NaOCl is the main recommended irrigant by experts due to its antibacterial activity and dissolving capacity on pulp tissue, and presently the most efficient antibacterial agent for root canal disinfection. Numerous antimicrobial agents, like Chlorhexidine, have been proposed as alternatives for root canal disinfection. Chlorhexidine is relatively non-toxic but its efficacy is questionable, being that some authors reported a reduced activity against E. faecalis biofilm and endotoxins compared to NaOCl.

The antimicrobial action of MTAD is due to its complex formulation but even so, it is not able to completely disintegrate and remove the E. faecalis biofilm.

It is often requested by patients that the irrigant be formulated with natural substances, since many prefer holistic medicine. Thus five plant extracts have been selected for further studies.

Uncaria tomentosa has proved less effective than Chlorhexidine against E. faecalis, but it does have anti-inflammatory and immunomodulating properties.

Apple vinegar has shown good preliminary results in animal experiments regarding its smear-layer removal abilities.

Propolis and ginger extracts have demonstrated good activity as intracanal medicaments in ex vivo studies.

The research on the effects of essential oils on E. faecalis is still scarce, thus further studies on the subject should be conducted. In particular, pre-clinical studies would be necessary.

CONCLUSION

The purpose of endodontic treatment of teeth with pulpal necrosis and apical periodontitis is to eliminate microorganisms from the root canal system, dentinal tubules and the periapical region. NaOCl has continuously demonstrated stronger antimicrobial efficacy in the endodontic space than other irrigation solutions. The most important disadvantage of NaOCl is its strong toxicity to the periapical tissues when it extrudes through the apex. Many plant extracts have shown pharmaceutical potential against several microorganisms such as Enterococcus faecalis, but further studies have demonstrated their inefficacy when used in ex vivo studies.

The literature analyzed thus far, has focused its attention on plant derivatives that are capable of antibacterial activity against Enterococcus faecalis, without in vivo studies. We can therefore hypothesize that some of these phytotherapic substances could be a potential alternative to NaOCl for the biomechanical treatment of the endodontic space.

CONFLICT OF INTEREST

The authors confirm that this article content has no conflict of interest.

ACKNOWLEDGEMENTS

Declared none.

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