ORIGINAL RESEARCH
Clinical implications of Enterococcus faecalis microbial contamination in root canals of devitalized teeth: Literature review
Implicancias clínicas de la contaminación microbiana por Enterococcus faecalis en canales radiculares de dientes desvitalizados: Revisión de la literatura
a School of Dentistry, Endodontics Chair, Mayor University, Temuco Campus, Temuco, Chile. Master's Program in Dentistry, School of Dentistry, La Frontera University, Temuco, Chile
b Comprehensive Adult Dentistry Department, School of Dentistry, La Frontera University, Temuco, Chile. Center of Molecular Biology and Pharmacogenetics, Basic Sciences Department, School of Dentistry, La Frontera University, Temuco, Chile
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Reporte de un caso y revisión de la literatura" ] ] "contieneResumen" => array:2 [ "en" => true "es" => true ] "contieneTextoCompleto" => array:1 [ "en" => true ] "contienePdf" => array:1 [ "en" => true ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:7 [ "identificador" => "fig0025" "etiqueta" => "Figure 5" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr5.jpeg" "Alto" => 631 "Ancho" => 997 "Tamanyo" => 111481 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0035" class="elsevierStyleSimplePara elsevierViewall">Circumscribed lesion with presence of approximately 4 x 4<span class="elsevierStyleHsp" style=""></span>cm permanent canine therein.</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Risk Díaz Castillejos, Ana María Nieto Munguía, Guillermina Castillo Ham" "autores" => array:3 [ 0 => array:2 [ "nombre" => "Risk" "apellidos" => "Díaz Castillejos" ] 1 => 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=> "<span class="elsevierStyleTextfn">ORIGINAL RESEARCH</span>" "titulo" => "Physicochemical analysis of MTA Angelus® and Biodentine® conducted with X ray difraction, dispersive energy spectrometry, X ray fluorescence, scanning electron microscope and infra red spectroscopy" "tienePdf" => "en" "tieneTextoCompleto" => "en" "tieneResumen" => array:2 [ 0 => "en" 1 => "es" ] "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "e170" "paginaFinal" => "e176" ] ] "titulosAlternativos" => array:1 [ "es" => array:1 [ "titulo" => "<span class="elsevierStyleItalic">Análisis fisicoquímico del MTA Angelus® y Biodentine® mediante difracción de rayos X, espectrometría de energía dispersiva, fluorescencia de rayos X, microscopio electrónico de barrido y espectroscopía de rayos infrarrojos</span>" ] ] "contieneResumen" => array:2 [ "en" => true "es" => true ] "contieneTextoCompleto" => array:1 [ "en" => true ] "contienePdf" => array:1 [ "en" => true ] "resumenGrafico" => array:2 [ "original" => 0 "multimedia" => array:7 [ "identificador" => "fig0005" "etiqueta" => "Figure 1" "tipo" => "MULTIMEDIAFIGURA" "mostrarFloat" => true "mostrarDisplay" => false "figura" => array:1 [ 0 => array:4 [ "imagen" => "gr1.jpeg" "Alto" => 583 "Ancho" => 2106 "Tamanyo" => 162327 ] ] "descripcion" => array:1 [ "en" => "<p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">Biodentine Scanning electron micrographs at magnifications of 500X, 1000X and 2000X where irregular and filiform shaped crystals can be observed.</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Alejandra Citlalli Rodríguez Rocha, Genoveva Hernández Padrón, Margarita V García Garduño, Raúl Luis García Aranda" "autores" => array:4 [ 0 => array:2 [ "nombre" => "Alejandra Citlalli Rodríguez" "apellidos" => "Rocha" ] 1 => array:2 [ "nombre" => "Genoveva Hernández" "apellidos" => "Padrón" ] 2 => array:3 [ "preGrado" => "PhD researcher" "nombre" => "Margarita V García" "apellidos" => "Garduño" ] 3 => array:3 [ "preGrado" => "PhD" "nombre" => "Raúl Luis García" "apellidos" => "Aranda" ] ] ] ] ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S1870199X16000410?idApp=UINPBA00004N" "url" => "/1870199X/0000001900000003/v2_201602290913/S1870199X16000410/v2_201602290913/en/main.assets" ] "en" => array:15 [ "idiomaDefecto" => true "cabecera" => "<span class="elsevierStyleTextfn">ORIGINAL RESEARCH</span>" "titulo" => "Clinical implications of <span class="elsevierStyleItalic">Enterococcus faecalis</span> microbial contamination in root canals of devitalized teeth: Literature review" "tieneTextoCompleto" => true "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "e177" "paginaFinal" => "e182" ] ] "autores" => array:1 [ 0 => array:4 [ "autoresLista" => "Cynthia Rodríguez-Niklitschek, Gonzalo H Oporto V" "autores" => array:2 [ 0 => array:4 [ "nombre" => "Cynthia" "apellidos" => "Rodríguez-Niklitschek" "email" => array:1 [ 0 => "cynthia.rodriguez@mayor.cl" ] "referencia" => array:2 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] 1 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">*</span>" "identificador" => "cor0005" ] ] ] 1 => array:3 [ "nombre" => "Gonzalo H" "apellidos" => "Oporto V" "referencia" => array:1 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">b</span>" "identificador" => "aff0010" ] ] ] ] "afiliaciones" => array:2 [ 0 => array:3 [ "entidad" => "School of Dentistry, Endodontics Chair, Mayor University, Temuco Campus, Temuco, Chile. Master's Program in Dentistry, School of Dentistry, La Frontera University, Temuco, Chile" "etiqueta" => "a" "identificador" => "aff0005" ] 1 => array:3 [ "entidad" => "Comprehensive Adult Dentistry Department, School of Dentistry, La Frontera University, Temuco, Chile. Center of Molecular Biology and Pharmacogenetics, Basic Sciences Department, School of Dentistry, La Frontera University, Temuco, Chile" "etiqueta" => "b" "identificador" => "aff0010" ] ] "correspondencia" => array:1 [ 0 => array:3 [ "identificador" => "cor0005" "etiqueta" => "⁎" "correspondencia" => "Corresponding author." ] ] ] ] "titulosAlternativos" => array:1 [ "es" => array:1 [ "titulo" => "<span class="elsevierStyleItalic">Implicancias clínicas de la contaminación microbiana por</span> Enterococcus faecalis <span class="elsevierStyleItalic">en canales radiculares de dientes desvitalizados: Revisión de la literatura</span>" ] ] "textoCompleto" => "<span class="elsevierStyleSections"><span id="sec0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0025">INTRODUCTION</span><p id="par0005" class="elsevierStylePara elsevierViewall">In many countries, oral cavity diseases represent a public health issue. Dental caries is one the most prevalent diseases. In Chile the MINSAL (Chile's Health Ministry) established the fact that 66% of total population was afflicted with dental caries.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1–4</span></a> Endodontic treatment represents one option to treat teeth widely destroyed by this condition. Endodontic treatment's objective is to execute a meticulous chemical and mechanical cleansing of root canals to later achieve tri-dimensional seal with inert material and thus prevent re-infection. After this, rehabilitation of the dental crown is undertaken, thus dental caries containment and tooth loss prevention is finally achieved. Even though this kind of therapies, when suitably prescribed, exhibit favorable prognosis, scientific literature indicates there is a possibility of failure. One of the main causes of failure in endodontic treatments is incomplete removal of pulp tissue or micro-organisms present within the root canals. These micro-organisms might have survived biochemical procedures or have invaded root canals through crown filtration in teeth with filled roots.<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a> Several studies have revealed the fact that microbiota present in root canals of endodontically treated roots differ from microbiota normally found in untreated teeth.<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a> When analyzing the micro-organism factor, literature suggests that bacteria most frequently found in first time treatments, as well as treatments with infection recurrence, are limited to a very specific variety of micro-organisms, where gram positive anaerobic facultative species predominate, especially <span class="elsevierStyleItalic">Enterococcus faecalis</span>.<a class="elsevierStyleCrossRef" href="#bib0025"><span class="elsevierStyleSup">5</span></a> This bacteria has been isolated within root canal systems as well as in periapical lesions. It has equally been found in infected teeth that had not been previously endodontically treated. Nevertheless, it is most frequently observed in teeth that have suffered recurrence, that is to say failure of previous endodontic treatment.<a class="elsevierStyleCrossRefs" href="#bib0025"><span class="elsevierStyleSup">5–9</span></a></p></span><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0030">MATERIALS AND METHODS</span><p id="par0010" class="elsevierStylePara elsevierViewall">Bibliographic review was undertaken through internet search of different scientific articles collected from electronic databases such as EBSCO, Cochcrane, Medline and Lilacs, using electronic search engines such as Pubmed and Decs.</p><p id="par0015" class="elsevierStylePara elsevierViewall">To undertake the search, the following key words were used: <span class="elsevierStyleItalic">Enterococcus faecalis</span>, endodontics, failed endodontic treatment, endodontic infection.</p><p id="par0020" class="elsevierStylePara elsevierViewall">Experimental studies, written in Spanish and English as well as literature reviews published during the preceding 30 years (1985 to 2014) were used. The search was not limited to search by country or by type of study. Once the articles were downloaded, they were stored in pdf format to preserve their originality.</p><p id="par0025" class="elsevierStylePara elsevierViewall">In order to proceed to selection, abstracts were reviewed, and when needed, full articles were examined, so as to decide whether their information was related (or unrelated) to the target of the present work.</p><p id="par0030" class="elsevierStylePara elsevierViewall">After initial search, 52 articles were located, out of which 22 were discarded due to lack of relevance to the target of this review. 26 articles were finally selected.</p></span><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0035">CAUSES FOR ENDODONTIC TREATMENT FAILURE</span><p id="par0035" class="elsevierStylePara elsevierViewall">Bacteria and their by-products are considered primary etiological agents for pulp necrosis and periapical lesions. For this reason, their complete elimination is one of the most important steps of endodontic treatment.<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a></p><p id="par0040" class="elsevierStylePara elsevierViewall">In most cases, treatment failure sets in when procedures undertaken within root canals do not achieve a satisfactory control and infection elimination. Incomplete removal of pulp tissue and microorganisms present in the root canal systems have been proposed as main causes for endodontic treatment failure.<a class="elsevierStyleCrossRefs" href="#bib0055"><span class="elsevierStyleSup">11,12</span></a> In many cases, full debridement of infected canals can be unattainable due to inaccessibility of infection sites, for example, when there is presence of accessory canals which are totally unreachable to instruments, medication or irrigants.<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a> In most cases, endodontic treatment failures are due to the activity of microorganisms which are surviving within the apical portion of root canal systems, even in well-treated teeth. It has been demonstrated that parts of the root canal frequently remain intact during the process of chemical and mechanical preparation, regardless of technique employed or instruments used. Areas untouched by instruments may contain bacteria or rest of necrotic tissue, even though root canals filling might appear radiographically adequate.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a></p><p id="par0045" class="elsevierStylePara elsevierViewall">Within the canal system, bacteria are found located in areas such as isthmus ramifications, deltas, canal irregularities and dentine tubules.<a class="elsevierStyleCrossRefs" href="#bib0070"><span class="elsevierStyleSup">14–16</span></a> In those cases when use of bio-mechanical instruments, irrigator materials or medication are unable to reach those sites, it is probable that nutrient supply for bacteriae placed therein remain unaltered after root therapy. Nevertheless, bacteria present in areas such as dentin tubules might have a drastically reduced substrate. In those anatomical regions, bacteria isolated by root filling normally die. Nevertheless, some bacterial species might survive for relatively long periods. Thus, in cases when root filling materials fail, and provide incomplete sealing, fluid filtration from the periapical tissue might provide a substrate suitable for bacterial growth.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a> The same situation might take place in cases when there are filtrations from the crown.</p><p id="par0050" class="elsevierStylePara elsevierViewall">Depending on the circumstances present in root canals, some bacteria might be more capable to survive and multiply than others. Thus, even though it is possible to find facultative anaerobes in teeth with pulp necrosis, it is more frequent to find strict anaerobes in primarily infected canals (that is to say, without previous endodontic treatment and with necrotic pulp), and facultative anaerobes in cases of failed endodontic treatment.<a class="elsevierStyleCrossRefs" href="#bib0030"><span class="elsevierStyleSup">6,8</span></a> Microbial flora present in canals after endodontic treatment failure is limited to a small number of predominantly Gram-positive microbial species. Facultative anaerobes, especially <span class="elsevierStyleItalic">Enterococcuss</span> spp, are the most frequently<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a> isolated species.<a class="elsevierStyleCrossRefs" href="#bib0050"><span class="elsevierStyleSup">10,13,14</span></a> Several studies have shown that frequency of <span class="elsevierStyleItalic">Enterococcus</span> species found in filled roots which exhibit apical periodontitis can even reach 70%.<a class="elsevierStyleCrossRefs" href="#bib0030"><span class="elsevierStyleSup">6,15–18</span></a></p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0040">ROLE OF <span class="elsevierStyleItalic">ENTEROCOCCUS FAECALIS</span> IN ENDODONTIC TREATMENT FAILURE</span><p id="par0055" class="elsevierStylePara elsevierViewall">The gender <span class="elsevierStyleItalic">Enterococcus</span> corresponds to gram-positive, facultative anaerobe type coccus bacteriae; they are part of the habitual flora found in the mouth, human gastrointestinal tract and female genital tract. Moreover, they are a wellknown cause of endodontic treatment failure as well as some systemic diseases such as urinary tract infections, surgical wounds infections, bacteremia and bacterial endocarditis.<a class="elsevierStyleCrossRefs" href="#bib0025"><span class="elsevierStyleSup">5,19</span></a> They have developed high resistance to antimicrobial agents and possess numerous virulence factors such as aggregation substances, surface protein, gelatinase, extracellular superoxide production, capsular polysaccharides and antibiotic resistance determinant. <span class="elsevierStyleItalic">Enterococcus</span> are recognized as potential human pathogens, causing 12% of all hospital infections. In recurrent endodontic infections, the <span class="elsevierStyleItalic">Enterococcus</span> species most frequently isolated is <span class="elsevierStyleItalic">Enteroccoccus faecalis</span>.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a></p><p id="par0060" class="elsevierStylePara elsevierViewall">The frequent presence of <span class="elsevierStyleItalic">Enterococcus faecalis</span> in root canals where endodontic treatment has failed suggests that this is an opportunist pathogen, whose persistence in the canals represents a significant therapeutic problem.</p><p id="par0065" class="elsevierStylePara elsevierViewall">Once it is installed within the canals system, <span class="elsevierStyleItalic">Enterococcus faecalis</span> faces several challenges in order to ensure survival, including the ability to withstand the action of antimicrobial agents used during endodontic treatment as well as surviving lack of nutrients in canals which have been cleansed and filled.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a> Two potential causes emerge when analyzing the causes which lead to fi nding this bacteria in teeth which require secondary endodontic treatment. One indicates that <span class="elsevierStyleItalic">Enterococcus faecalis</span> possesses the ability to colonize and infect dentin tubules, this fact complicates its removal through chemical and mechanical cleansing, given the small diameter of these anatomical structures,<a class="elsevierStyleCrossRefs" href="#bib0100"><span class="elsevierStyleSup">20,21</span></a> along with the ability exhibited by these bacteriae to bond to collagen.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a> Another possible cause is the potential resistance these bacteria might possess against calcium hydroxide, which is the antibacterial medication most commonly used within the root canal system during endodontic therapy<a class="elsevierStyleCrossRef" href="#bib0110"><span class="elsevierStyleSup">22</span></a> which would allow these micro-organisms to remain in quiescent state.<a class="elsevierStyleCrossRefs" href="#bib0035"><span class="elsevierStyleSup">7,8,13,20,21</span></a><span class="elsevierStyleItalic">Enterococcus faecalis</span> persistence has been attributed to its ability to resist the high pH of calcium hydroxide, material which is frequently introduced in the canals, and preserved in that location for at least a week.<a class="elsevierStyleCrossRef" href="#bib0115"><span class="elsevierStyleSup">23</span></a> The resistance of this microorganism might be influenced by the effects of dentin plugging, so that pH increase cannot be achieved within dentin tubules<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a> where this bacteria might be lodged. Besides this fact, research on the possible causes which produce <span class="elsevierStyleItalic">Enterococcus faecalis</span> resistance to calcium hydroxide, suggests that the expression of certain genes of this bacteria as well as the operation of a proton bomb, play an important role in this phenomenon.<a class="elsevierStyleCrossRefs" href="#bib0065"><span class="elsevierStyleSup">13,20</span></a></p></span><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0045"><span class="elsevierStyleItalic">ENTEROCOCCUS FAECALIS</span> RESISTANCE MECHANISMS TO ANTIMICROBIAL AGENTS</span><p id="par0070" class="elsevierStylePara elsevierViewall">Antimicrobial activity of calcium hydroxide is based upon release of hydroxide ions<a class="elsevierStyleCrossRef" href="#bib0120"><span class="elsevierStyleSup">24</span></a> which are able to generate numerous alterations in the cell's aqueous environment and generate harmful changes in the membrane's structure, finally affecting the bacterial DNS. When the <span class="elsevierStyleItalic">Enterococcus faecalis</span> cells enter into their latency phase, they acquire greater resistance to the calcium hydroxide's antibacterial effect, through mechanisms which have not yet been fully ascertained. Even though it has been documented that <span class="elsevierStyleItalic">Enterococcus faecalis</span> can withstand the high pH of calcium hydroxide, relatively little is known about the survival mechanisms that enable it to tolerate such exposition. Curiously, the resistance to calcium hydroxide destruction exhibited by <span class="elsevierStyleItalic">Enterococcus faecalis</span> is shared with other microorganisms associated with endodontic treatment failures, such as species of <span class="elsevierStyleItalic">Candida</span> and Actonomyces.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a></p><p id="par0075" class="elsevierStylePara elsevierViewall">The ability to survive in adverse circumstances is important for most bacteriae, due to the long starvation periods they normally experience. Several regulation systems play essential roles in the ability of bacteriae to withstand nutrient depletion. These systems are under the control of certain genes whose transcription is activated under starvation circumstances.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a></p><p id="par0085" class="elsevierStylePara elsevierViewall">In general when bacteriae are confronted to an adverse or potentially lethal agent, a stress response is activated which allows them to withstand the threat, survive and recover.<a class="elsevierStyleCrossRefs" href="#bib0125"><span class="elsevierStyleSup">25,26</span></a> When this response is elicited, said status can confer general protection against a variety of other stress factors, for example, a stress response triggered by lack of nutrients can afford protection against heat exposition. <span class="elsevierStyleItalic">Enterococcus faecalis</span> is able to synthesize a wide variety of proteins when exposed to adverse environmental circumstances, such as an environment with high pH or exposure to sodium hypochlorite (irrigator material used in endodontic procedures). If nutrient depletion, exposure to sodium hypochlorite solution or calcium hydroxide induce <span class="elsevierStyleItalic">Enterococcus faecalis</span> to trigger a stress response, then said response could confer crossed protection for this bacteria at later exposures, for example, exposure to a new medication with calcium hydroxide;<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a> thus this mechanism could partly explain its resistance.</p><p id="par0090" class="elsevierStylePara elsevierViewall">Studies have shown that at a pH level of 11.5 or over, <span class="elsevierStyleItalic">Enterococcus faecalis</span> cannot survive, nevertheless it can survive at lesser concentrations.<a class="elsevierStyleCrossRefs" href="#bib0100"><span class="elsevierStyleSup">20,27</span></a> Due to the dentin's buffer effect, it is unlikely that the high pH of calcium hydroxide reaches dentin tubules, location where <span class="elsevierStyleItalic">Enterococcus faecalis</span> has the ability to deeply penetrate into.<a class="elsevierStyleCrossRef" href="#bib0140"><span class="elsevierStyleSup">28</span></a> Although pH value of calcium hydroxide pastes used in endodontic treatments is 12.3, in the root dentin achieved alkalinity does not exceed 10.3 pH. After canals are covered with calcium hydroxide<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a> in the root canal system, this value can fall to even pH 8.5-9.0 due to the dentin plugging effect. This value is not sufficiently high to eradicate <span class="elsevierStyleItalic">Enterococcus faecalis</span>.<a class="elsevierStyleCrossRef" href="#bib0145"><span class="elsevierStyleSup">29</span></a> Furthermore, since endodontic treatment generally includes alternate use of drugs at the different stages of root instrumentation procedures. <span class="elsevierStyleItalic">Enterococcus faecalis</span> is frequently exposed to a sub-lethal alkaline pH and this could induce bacterial cells to generate a stress response that might improve survival. Thus, repeated exposure of <span class="elsevierStyleItalic">Enterococcus faecalis</span> to calcium hydroxide and sodium hypochloride solution could trigger resistance mechanisms at subsequent exposures, even at levels which could be lethal.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a></p><p id="par0095" class="elsevierStylePara elsevierViewall">In addition to the adaptive response in an alkaline pH and stress-induced protein synthesis, in these bacteriae a proton bomb has also been described, with the ability to acidify cytoplasm. This mechanism would be vital for the survival of <span class="elsevierStyleItalic">Enterococcus faecalis</span> at high pH levels, and could be considered more important than the aforementioned adaptive mechanisms.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a> The operating mechanism of this proton bomb basically consists on a bacterial response to penetration of hydroxyl ions into the bacterial cytoplasm, which could increase intracellular pH. In that situation, the proton bomb is activated and responds sending (positively charged) potassium ions to the bacterial cytoplasm, thus achieving their acidification and preventing enzymatic inhibition.<a class="elsevierStyleCrossRef" href="#bib0145"><span class="elsevierStyleSup">29</span></a></p><p id="par0100" class="elsevierStylePara elsevierViewall">Microorganisms remaining within root canals can die or remain viable depending on the nutrient availability in the canal system and the ability to survive in nutrient-depleted circumstances. In those cases when they remain viable, their proliferation can be inhibited or reduced. In spite of aforementioned resistance mechanisms, failure of endodontic treatment attributed to residual microorganisms will only take place in cases when they possess pathogenicity, reach sufficient numbers and have access to periapical tissues in order to induce or preserve the disease around the root.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a> Furthermore, variation of resistance to alkaline pH can be related to existence of variable genotypes among <span class="elsevierStyleItalic">Enterococcus faecalis</span> strains, that is to say, genetic variations of <span class="elsevierStyleItalic">Enterococcus faecalis</span> strains can take place in the time they generate phenotypes of greater resistance to alkaline pH.<a class="elsevierStyleCrossRef" href="#bib0150"><span class="elsevierStyleSup">30</span></a></p></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0050">CONCLUSIONS</span><p id="par0105" class="elsevierStylePara elsevierViewall">The fact of frequently finding <span class="elsevierStyleItalic">Enterococcus faecalis</span> in the root canals of teeth having received failed endodontic procedures means that this species is intimately involved in the pathogenesis and persistence of apical periodontitis. Thus, this bacteria is frequently isolated in cases of primary and secondary endodontic infections. It is thus necessary to conduct further research which might allow to lead to the preparation of more efficient antimicrobial agents to be used in endodontic treatments.</p><p id="par0110" class="elsevierStylePara elsevierViewall">It is important to point out that <span class="elsevierStyleItalic">Enterococcus faecalis's</span> survival in root canals is due to the fact that irrigator materials or drugs used during the instrument-phase of the treatment are not able to fully reach the canal system, or the fact that root filling might not achieve full tri-dimensional seal, leaving thus spaces where these microorganisms might hide and survive, this would be the case of dentin tubules. Therefore in addition to finding better and more effective endodontic drugs, emphasis must be placed on searching for more efficient and tri-dimensionally effective filling systems.</p><p id="par0115" class="elsevierStylePara elsevierViewall">An important point to assess would be the clinical importance of <span class="elsevierStyleItalic">Enterococcus faecalis</span> antibacterial resistance mechanisms. Is has been documented that this bacteria is resistant to the antimicrobial effect of several drugs, including calcium hydroxide. Therefore, when <span class="elsevierStyleItalic">Enterococcus faecalis</span> is established within the canal system its eradication with conventional means can be extremely difficult. Thus, it would be interesting to further the search for new drugs that might be used by themselves, or associated to calcium hydroxide, or else determine minimal inhibitory concentrations of different drugs so as to achieve improved clinical results. It is worth mentioning that in order to prevent microbial reinfection of the canal system, how important it is to disinfect root canals and completely fill them as well as to place a suitable crown seal immediately after endodontic treatment, and its timely substitution for a permanent restoration.</p><p id="par0120" class="elsevierStylePara elsevierViewall">Although it has been proven that <span class="elsevierStyleItalic">Enterococcus faecalis</span> is present in most cases of infected canals, (mainly those which have been endodontically retreated) its role in the pathogenesis of periapical diseases associated to necrotic pulp or endodontic failure has not yet been clearly established. Even though <span class="elsevierStyleItalic">Enterococcus faecalis</span> might possess the ability to resist medication used in endodontic treatments, the possibility that some strains are more resistant than others or might be better adapted to surviving in extreme circumstances must not be overlooked. Furthermore, identification of genes expressed by cells of this bacteria during the stationary phase could further the development of treatment protocols which might permanently eradicate <span class="elsevierStyleItalic">Enterococcus faecalis</span> from infected root canals.</p></span></span>" "textoCompletoSecciones" => array:1 [ "secciones" => array:11 [ 0 => array:3 [ "identificador" => "xres610934" "titulo" => "ABSTRACT" "secciones" => array:1 [ 0 => array:1 [ "identificador" => "abst0005" ] ] ] 1 => array:2 [ "identificador" => "xpalclavsec624924" "titulo" => "Keywords" ] 2 => array:3 [ "identificador" => "xres610935" "titulo" => "RESUMEN" "secciones" => array:1 [ 0 => array:1 [ "identificador" => "abst0010" ] ] ] 3 => array:2 [ "identificador" => "xpalclavsec624923" "titulo" => "Palabras clave" ] 4 => array:2 [ "identificador" => "sec0005" "titulo" => "INTRODUCTION" ] 5 => array:2 [ "identificador" => "sec0010" "titulo" => "MATERIALS AND METHODS" ] 6 => array:2 [ "identificador" => "sec0015" "titulo" => "CAUSES FOR ENDODONTIC TREATMENT FAILURE" ] 7 => array:2 [ "identificador" => "sec0020" "titulo" => "ROLE OF ENTEROCOCCUS FAECALIS IN ENDODONTIC TREATMENT FAILURE" ] 8 => array:2 [ "identificador" => "sec0025" "titulo" => "ENTEROCOCCUS FAECALIS RESISTANCE MECHANISMS TO ANTIMICROBIAL AGENTS" ] 9 => array:2 [ "identificador" => "sec0030" "titulo" => "CONCLUSIONS" ] 10 => array:1 [ "titulo" => "REFERENCES" ] ] ] "pdfFichero" => "main.pdf" "tienePdf" => true "PalabrasClave" => array:2 [ "en" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Keywords" "identificador" => "xpalclavsec624924" "palabras" => array:4 [ 0 => "<span class="elsevierStyleItalic">Enterococcus faecalis</span>" 1 => "endodontics" 2 => "failed endodontic treatment" 3 => "endodontic infection." ] ] ] "es" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Palabras clave" "identificador" => "xpalclavsec624923" "palabras" => array:4 [ 0 => "<span class="elsevierStyleItalic">Enterococcus faecalis</span>" 1 => "endodoncia" 2 => "tratamiento de endodoncia fallido" 3 => "infección endodóntica." ] ] ] ] "tieneResumen" => true "resumen" => array:2 [ "en" => array:2 [ "titulo" => "ABSTRACT" "resumen" => "<span id="abst0005" class="elsevierStyleSection elsevierViewall"><p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">Dental caries is a highly prevalent disease in the world. Endodontic treatment is an option to treat teeth widely destroyed by dental caries. Even though this type of therapy offers favorable prognosis in most cases, scientific literature suggests there is a possibility for failure. In endodontic treatments, one of the most prevalent causes for treatment failure is permanence of microorganisms within root canals. Among the numerous existing bacterial species, <span class="elsevierStyleItalic">Enterococcus faecalis</span> is one of the most frequently found in teeth with pulp necrosis (lacking previous history of endodontic treatment). It is equally the most frequently isolated species in teeth with infection recurrence (teeth exhibiting evidence of recurrent treatment). To achieve successful endodontic treatment in devitalized teeth it is of the utmost importance to study and be aware of endodontic microbiology. This leads then to the need of studying bacterial behavior within the system of root canals as well as their resistance and defense mechanisms in order to best manage their interaction with the tooth and achieve bacterial obliteration. The present article purports to offer a bibliographic review of existing literature on <span class="elsevierStyleItalic">Enterococus faecalis</span>, its main characteristics as well as resistance mechanisms. Bibliographic search was conducted through electronic databases (EBSCO, Cochcrane, Medline and Lilacs), using search engines (Pubmed and Decs). Included articles were written in Spanish and English and published during the last 30 years. Out of a total 52 articles, 26 were selected; they corresponded to experimental studies and literature reviews.</p></span>" ] "es" => array:2 [ "titulo" => "RESUMEN" "resumen" => "<span id="abst0010" class="elsevierStyleSection elsevierViewall"><p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">La caries dental es una enfermedad altamente prevalente en el mundo. Una opción para tratar dientes ampliamente destruidos por caries dental es la realización de tratamientos de endodoncia. Aun cuando estas terapias tienen un pronóstico favorable en la mayoría de los casos, la literatura señala que existe la posibilidad de fracaso. Una de las principales causas de fracaso en los tratamientos de endodoncia es la permanencia de microorganismos en los canales radiculares. Dentro de las numerosas especies bacterianas existentes, una de las más frecuentemente encontradas en dientes con necrosis pulpar (sin historia previa de endodoncia) y la más aislada en aquellos con recidiva de infección (dientes con indicación de retratamiento) es <span class="elsevierStyleItalic">Enterococcus faecalis</span>. Estudiar y conocer la microbiología endodóntica es requisito fundamental para lograr un tratamiento de endodoncia exitoso en dientes desvitalizados. Surge así la necesidad de conocer el comportamiento de las bacterias dentro del sistema de canales radiculares, así como sus mecanismos de defensa y resistencia, para manejar de la mejor manera posible su interacción con el diente y lograr su eliminación. El siguiente artículo corresponde a una revisión bibliográfica de la literatura existente acerca de <span class="elsevierStyleItalic">Enterococcus faecalis</span>, sus características principales y mecanismos de resistencia. La búsqueda bibliográfica se realizó a través de bases de datos electrónicas (EBSCO, Cochcrane, Medline y Lilacs), utilizando motores de búsqueda (Pubmed y Decs); se incluyeron artículos en inglés y español, publicados durante los últimos 30 años. De un total de 52 artículos, se seleccionaron 26, correspondientes a estudios experimentales y revisiones de literatura.</p></span>" ] ] "bibliografia" => array:2 [ "titulo" => "REFERENCES" "seccion" => array:1 [ 0 => array:2 [ "identificador" => "bibs0005" "bibliografiaReferencia" => array:30 [ 0 => array:3 [ "identificador" => "bib0005" "etiqueta" => "1" "referencia" => array:1 [ 0 => array:2 [ "contribucion" => array:1 [ 0 => array:2 [ "titulo" => "Caries dentaria y fluorosis en niños de 6 a 8 y 12 años de II, RM, VI, VIII, IX y X regiones" "autores" => array:1 [ 0 => array:2 [ "etal" => false "autores" => array:3 [ 0 => "T. Urbina" 1 => "J.C. Caro" 2 => "M. 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| Year/Month | Html | Total | |
|---|---|---|---|
| 2024 November | 10 | 2 | 12 |
| 2024 October | 99 | 11 | 110 |
| 2024 September | 112 | 19 | 131 |
| 2024 August | 116 | 35 | 151 |
| 2024 July | 97 | 11 | 108 |
| 2024 June | 72 | 8 | 80 |
| 2024 May | 77 | 12 | 89 |
| 2024 April | 89 | 7 | 96 |
| 2024 March | 107 | 10 | 117 |
| 2024 February | 92 | 15 | 107 |
| 2024 January | 133 | 17 | 150 |
| 2023 December | 72 | 10 | 82 |
| 2023 November | 101 | 19 | 120 |
| 2023 October | 107 | 22 | 129 |
| 2023 September | 93 | 6 | 99 |
| 2023 August | 78 | 13 | 91 |
| 2023 July | 82 | 12 | 94 |
| 2023 June | 135 | 18 | 153 |
| 2023 May | 137 | 11 | 148 |
| 2023 April | 101 | 9 | 110 |
| 2023 March | 118 | 20 | 138 |
| 2023 February | 73 | 11 | 84 |
| 2023 January | 105 | 18 | 123 |
| 2022 December | 75 | 18 | 93 |
| 2022 November | 85 | 11 | 96 |
| 2022 October | 64 | 19 | 83 |
| 2022 September | 55 | 20 | 75 |
| 2022 August | 61 | 21 | 82 |
| 2022 July | 60 | 15 | 75 |
| 2022 June | 50 | 15 | 65 |
| 2022 May | 74 | 22 | 96 |
| 2022 April | 54 | 22 | 76 |
| 2022 March | 57 | 16 | 73 |
| 2022 February | 58 | 18 | 76 |
| 2022 January | 58 | 12 | 70 |
| 2021 December | 68 | 14 | 82 |
| 2021 November | 85 | 8 | 93 |
| 2021 October | 54 | 14 | 68 |
| 2021 September | 37 | 10 | 47 |
| 2021 August | 34 | 10 | 44 |
| 2021 July | 33 | 10 | 43 |
| 2021 June | 34 | 5 | 39 |
| 2021 May | 18 | 13 | 31 |
| 2021 April | 41 | 23 | 64 |
| 2021 March | 32 | 18 | 50 |
| 2021 February | 13 | 41 | 54 |
| 2021 January | 22 | 12 | 34 |
| 2020 December | 13 | 6 | 19 |
| 2020 November | 13 | 7 | 20 |
| 2020 October | 5 | 5 | 10 |
| 2020 September | 11 | 26 | 37 |
| 2020 August | 15 | 29 | 44 |
| 2020 July | 13 | 7 | 20 |
| 2020 June | 8 | 6 | 14 |
| 2020 May | 20 | 12 | 32 |
| 2020 April | 12 | 5 | 17 |
| 2020 March | 13 | 4 | 17 |
| 2020 February | 14 | 8 | 22 |
| 2020 January | 16 | 10 | 26 |
| 2019 December | 20 | 8 | 28 |
| 2019 November | 17 | 10 | 27 |
| 2019 October | 7 | 1 | 8 |
| 2019 September | 7 | 6 | 13 |
| 2019 August | 7 | 3 | 10 |
| 2019 July | 9 | 18 | 27 |
| 2019 June | 24 | 8 | 32 |
| 2019 May | 75 | 13 | 88 |
| 2019 April | 20 | 17 | 37 |
| 2019 March | 0 | 4 | 4 |
| 2019 February | 5 | 7 | 12 |
| 2019 January | 3 | 6 | 9 |
| 2018 December | 2 | 0 | 2 |
| 2018 November | 7 | 1 | 8 |
| 2018 October | 9 | 6 | 15 |
| 2018 September | 6 | 2 | 8 |
| 2018 August | 4 | 3 | 7 |
| 2018 July | 7 | 1 | 8 |
| 2018 June | 1 | 0 | 1 |
| 2018 May | 4 | 2 | 6 |
| 2018 April | 2 | 1 | 3 |
| 2018 March | 5 | 0 | 5 |
| 2018 February | 2 | 1 | 3 |
| 2018 January | 3 | 0 | 3 |
| 2017 December | 3 | 0 | 3 |
| 2017 November | 7 | 0 | 7 |
| 2017 October | 4 | 4 | 8 |
| 2017 September | 8 | 5 | 13 |
| 2017 August | 4 | 12 | 16 |
| 2017 July | 10 | 2 | 12 |
| 2017 June | 17 | 3 | 20 |
| 2017 May | 11 | 1 | 12 |
| 2017 April | 5 | 0 | 5 |
| 2017 March | 10 | 43 | 53 |
| 2017 February | 13 | 3 | 16 |
| 2017 January | 8 | 1 | 9 |
| 2016 December | 10 | 0 | 10 |
| 2016 November | 12 | 2 | 14 |
| 2016 October | 12 | 0 | 12 |
| 2016 September | 7 | 1 | 8 |
| 2016 August | 5 | 0 | 5 |
| 2016 July | 5 | 0 | 5 |
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