The evolving new understanding of endodontic infections

Identification of root canal microbiota profiles of periapical tissue diseases using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

OBJECTIVES

The purpose of this study was to identify microorganisms isolated from various periapical tissue diseases using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF-MS) and classify them via an unsupervised machine learning approach.

METHODS

A total of 150 patients with various apical conditions and teeth in need of endodontic retreatment were divided into five groups, including Retreatment, Acute Apical Abscess, Chronic Apical Abscess, Acute Apical Periodontitis, and Chronic Apical Periodontitis. Samples were collected from root canals using paper points after agitating with a #10 K file then microorganisms were identified using MALDI-TOF-MS. Data were analyzed using a hierarchical clustering method. Quadruple clusters and dendrograms were formed according to similarities and dissimilarities.

RESULTS

A total of 80 species were identified representative of six different phyla. The most similar microorganism species identified were: ''Enterococcus faecalis'' between 21 and 23-year-old female cases in Retreatment group; ''Lactobacillus rhamnosus'' between 20 and 18-year-old male cases in Symptomatic Apical Abscess cases; ''Lactobacillus paracasei'' between 26 and 40-year-old male cases in Asymptomatic Apical Abscess cases; ''Enterococcus faecalis'' between 48 and 50-year-old female cases in Symptomatic Apical Periodontitis cases; ''Lactobacillus rhamnosus'' between 48 and 60-year-old male cases in Asymptomatic Apical Periodontitis cases.

CONCLUSIONS

MALDI-TOF MS can be considered a fast and high-throughput screening technique for microbial species identification in endodontics. Thus, it will provide valuable data for future research designs regarding periapical tissue diseases. As the MALDI-TOF MS database expands and comprehensive data becomes available, the relationship between microbial profiles and disease progression will become increasingly apparent.

Disinfectant effectiveness of chlorhexidine gel compared to sodium hypochlorite: a systematic review with meta-analysis

This study aimed to compare the disinfectant ability of chlorhexidine (CHX) gel and sodium hypochlorite (NaOCl). Systematic searches were conducted from inception until December 8th, 2022 (MEDLINE/PubMed, Cochrane Library, Web of Science, Scopus, Embase, and Grey Literature databases). Only randomized clinical trials were included. The revised Cochrane risk of bias tools for randomized trials were used to assess the quality of studies. Meta-analyses were performed. The overall quality of evidence was assessed through the Grading of Recommendations Assessment, Development, and Evaluation tool. Six studies were included. Five had a low risk of bias and 1 had some concerns. Three studies assessed bacterial reduction. Two were included in the meta-analysis for bacterial reduction (mean difference, 75.03 [confidence interval, CI, -271.15, 421.22], p = 0.67; I2 = 74%); and 3 in the meta-analysis for cultivable bacteria after chemomechanical preparation (odds ratio, 1.03 [CI, 0.20, 5.31], P = 0.98; I2 = 49%). Five studies assessed endotoxin reduction. Three were included in a meta-analysis (mean difference, 20.59 [CI, -36.41, 77.59], p = 0.48; I2 = 74%). There seems to be no difference in the disinfectant ability of CHX gel and NaOCl, but further research is necessary.

Roles of Porphyromonas gulae proteases in bacterial and host cell biology

Porphyromonas gulae, an animal-derived periodontal pathogen, expresses several virulence factors, including fimbria, lipopolysaccharide (LPS) and proteases. We previously reported that its invasive efficiency was dependent on fimbriae types. In addition, P. gulae LPS increased inflammatory responses via toll-like receptors. The present study was conducted to investigate the involvement of P. gulae proteases in bacterial and host cell biology. Porphyromonas gulae strains showed an ability to agglutinate mouse erythrocytes and also demonstrated co-aggregation with Actinomyces viscosus, while the protease inhibitors antipain, PMSF, TLCK and leupeptin diminished P. gulae proteolytic activity, resulting in inhibition of haemagglutination and co-aggregation with A. viscosus. In addition, specific proteinase inhibitors were found to reduce bacterial cell growth. Porphyromonas gulae inhibited Ca9-22 cell proliferation in a multiplicity of infection- and time-dependent manner. Additionally, P. gulae-induced decreases in cell contact and adhesion-related proteins were accompanied by a marked change in cell morphology from well spread to rounded. In contrast, inhibition of protease activity prevented degradation of proteins, such as E-cadherin, β-catenin and focal adhesion kinase, and also blocked inhibition of cell proliferation. Together, these results indicate suppression of the amount of human proteins, such as γ-globulin, fibrinogen and fibronectin, by P. gulae proteases, suggesting that a novel protease complex contributes to bacterial virulence.

In vitro antimicrobial activity and comparison of the herbal extracts and sodium hypochlorite against primary plaque colonizers

NaClO is not suitable as a root canal irrigant because of its cytotoxicity. Good biocompatibility irrigants are required to have antibacterial activity. Many herbal products like Bee glue, Noni juice and Azadirachta indica have such properties. This study aims to investigate the possible effects of propolis, MCJ and Neem on bacterial infections and cytotoxicity in primary plaque colonizers. Direct contact and agar diffusion tests evaluated the antibacterial activity of herbal products against Fusobacterium, Candida albicans and Prevotella. The CCK 8 test determined the influence of these herbal products on the proliferation of human apical papilla stem cells (hSCAPs) and human periodontal fibroblasts (hPDLFs). A migration assay test was performed in addition to quantitative real-time PCR which measured osteogenic differentiation in hSCAPs. All herbal extracts tested in this study exhibited antibacterial activity comparable to NaClO against bacterial infections, while the strongest bacteriostatic effect was shown in the herbal treated group. These extracts had much weaker effects on the proliferation and migration of hSCAPs and hPDLFs as calculated by the CCK-8 assay against NaClO. Bee glue treatment had the most potent effect on osteogenic differentiation, followed by treatment with Noni juice and Azadirachta indica (Neem), while NaClO showed the lowest effect. For primary plaque colonizers of immature or advanced permanent teeth, Bee glue, Noni juice, and Azadirachta indica can be promising irrigants with good biocompatibility. Direct contact process and agar diffusion studies have tested the antibacterial activity against Fusobacterium, Candida albicans and Prevotella. The CCK 8 test determined the influence of these three plants on the proliferation of human apical papilla stem cells (hSCAPs) and human periodontal fibroblasts (hPDLFs). In order to examine migration ability, migration assay test was performed. Alizarin red staining, alkaline phosphatase (ALP) staining and quantitative real-time PCR measured osteo-/odontogenic differentiation in hSCAPs. All herbal extracts tested in this study exhibited antibacterial activity comparable to NaClO against bacterial infections, while the strongest bacteriostatic effect was shown in the treated group. These extracts had much weaker effects on the proliferation and migration of hSCAPs and hPDLFs as calculated by the CCK-8 assay against NaClO. Bee glue treatment had the most potent effect on osteo-odontogenic differentiation, followed by treatment with Noni juice and Azadirachta indica (Neem), while NaClO showed the lowest effect. For primary plaque colonizers of immature or advanced permanent teeth, Bee glue, Noni juice and Azadirachta indica (Neem) can be promising irrigants.

Radiographic and Clinical Findings of Single-Visit Root Canal Treatments with Apical Enlargement in Necrotic Teeth: A Retrospective Cohort Study

This study evaluated the long-term clinical outcomes of single-visit root canal treatments with apical enlargement on patients with necrotic pulp tissue retrospectively. A total of 137 teeth with necrotic pulp tissue which underwent single-visit root canal treatments were included. The root canals were shaped up until the apical constriction, which was determined by an apex locator. The outcomes were evaluated by two independent and calibrated endodontists clinically and radiographically. Teeth were dichotomized into healed (PAI ≤ 2, no signs or symptoms) and nonhealed (PAI > 2, with/without signs or symptoms) groups. Each patients' preoperative PAI and lesion size were recorded to evaluate the preoperative periapical status as well as several other prognostic factors. Statistical analyses were performed (p = 0.05) on ninety teeth. The mean observation time was 60 months. Out of ninety teeth, 87 (96.7%) were healed and 3 (3.3%) were nonhealed. No correlations were found between the prognostic factors and the outcomes (p > 0.05). Cohen's kappa and Gwet's agreement coefficient scores between the preoperative PAI scores and preoperative lesion sizes showed good agreements, with values of 0.834 and 0.898, respectively. Apical enlargement is a viable treatment option for single-visit root canal treatments.

Can Herbal Extracts Serve as Antibacterial Root Canal Irrigating Solutions? Antimicrobial Efficacy of Tylophora indica, Curcumin longa, Phyllanthus amarus, and Sodium Hypochlorite on Enterococcus faecalis Biofilms Formed on Tooth Substrate: In Vitro Study

Aim:

The purpose of this study was to evaluate the antimicrobial efficacy of Tylophora indica, Curcumin longa, and Phyllanthus amarus on Enterococcus faecalis biofilms formed on the tooth substrate. Sodium hypochlorite was used as a positive control. DMSO (dimethyl sulfoxide), the vehicle for the herbal extracts, was used as the negative control.

Materials and Methods:

Extracted human teeth were biomechanically prepared, vertically sectioned, placed in the tissue culture wells exposing the root canal surface to E. faecalis to form a biofilm. At the end of the third week, all groups were treated for 15 min with the test solutions and the control. The results were analyzed both quantitatively and qualitatively.

Results:

Statistical analysis was performed by using one-way analysis of variance and compared by the Mann–Whitney test using the Statistical Package for the Social Sciences (SPSS) software, version 20.0. The qualitative assay with the 3-week biofilm on the canal portion showed complete inhibition of bacterial growth for NaOCl, whereas samples treated with herbal solutions showed significant reduction of bacterial growth compared to control group, which showed 139.9 × 10⁹ CFU/mL among the experimental herbal solutions groups. P. amarus has shown maximum bacterial count followed by C. longa and T. indica.

Conclusion:

NaOCl 5% showed maximum antibacterial activity against 3-week biofilm on tooth substrate. T. indica, P. amarus, and C. longa showed statistically significant antibacterial activity against 3-week biofilm. The use of herbal alternatives might prove to be advantageous considering the several undesirable characteristics of NaOCl.

Historical and Contemporary Perspectives on the Microbiological Aspects of Endodontics

The microbiota of the oral cavity plays a significant role in pulpal and periapical diseases. Historically, 100 years ago little was known on microbiota, but after a century of investigations, only now can many of the intimate secrets of microbial growth, expansion, persistence, communal activities, and virulence be revealed. However, with the capabilities of the microbiota for mutation, quorum sensing, and information transference, researchers are hard-pressed to keep up with both the changes and challenges that an amazingly wide range of bacterial species pose for both the scientist and clinician. Fortunately, the development and expansion of a vast array of molecular biological investigative techniques have enabled dentistry and its associated medical fields to attempt to keep pace with the wide and fascinating world of oral microbiology.

Restoration of the root canal treated tooth

When considering endodontically treated teeth, the quality of the restoration is important from the outset. It sheds light into possible causes of pulp necrosis or failure of endodontic treatment and influences the outcome of future endodontic treatment. A tooth undergoing endodontic treatment requires an effective coronal seal during and following completion of endodontic treatment. This paper discusses, using the available literature, the maintenance of optimal coronal seal and coronal integrity during and after root canal treatment.

Culture-based identification of pigmented Porphyromonas and Prevotella species in primary endodontic infections

Background. The most common species isolated from primary endodontic infections are black-pigmented bacteria. These species are implicated in apical abscess formation due to their proteolytic activity and are fastidious in nature. Therefore, the present study was carried out to evaluate the presence and identification of various pigmented Porphyromonas and Prevotella species in the infected root canal through culture-based techniques.

Methods. Thirty-one patients with primary endodontic infections were selected. Using sterile paper points, samples were collected from the root canals after access opening and prior to obturation, which were cultured using blood and kanamycin blood agar. Subsequently, biochemical test was used to identify the species and the results were analyzed using percentage comparison analysis, McNemar and chi-squared tests, Wilcoxon match pair test and paired t-test.

Results. Out of 31 samples 26 were positive for black-pigmented organisms; the predominantly isolated species were Prevotella followed by Porphyromonas. In Porphyromonas only P. gingivalis was isolated. One of the interesting features was isolation of P. gingivalis through culture, which is otherwise very difficult to isolate through culture.

Conclusion. The presence of Prevotella and Porphyromonas species suggests that a significant role is played by these organisms in the pathogenesis of endodontic infections.

Effect of Nanosilver Gel, Chlorhexidine Gluconate, and Camphorated Phenol on Enterococcus faecalis Biofilm

Aim. To assess the effectiveness of nanosilver gel (NSG) in comparison to chlorhexidine gluconate (CHX) and camphorated phenol (CP) against Enterococcus faecalis (E.f) biofilm. Methods and Materials. Two tests were done, methyl thiazolyl tetrazolium (MTT) assay and confocal laser scanning microscopy (CLSM) analysis, to determine the effectiveness of NSG, CHX, and CP on E.f biofilm. Polystyrene microtiter 96- and 6-well plates were used for MTT and CLSM, respectively. Nanosilver gel was in three concentrations (0.05%, 0.1%, and 0.2%), chlorhexidine gluconate used was 2%, and camphorated phenol and normal saline were as control. Analysis was done using one-way ANOVA; the post hoc test was run for multiple comparisons. The level of statistical significance was set at P < 0.05. Results. One-way ANOVA showed significant differences among groups (0.05% NSG and CP, 0.1% NSG and CP, 0.2% NSG and CP, 0.1% NSG and 2% CHX, 0.2% and NSG and 2% CHX) (P < 0.001) and also showed significant difference between groups (P < 0.001), f-ratio 87.823. A post hoc Tukey's test revealed no significant difference between chlorhexidine gluconate and 0.05% nanosilver gel (P > 0.05). Conclusions. 0.1% and 0.2% nanosilver gel is more effective on Enterococcus faecalis biofilm as compared to chlorhexidine gluconate and camphorated phenol.

What are the key endodontic factors associated with oral health-related quality of life?

AIM

To determine the associations between endodontic factors and oral health-related quality of life (OHQoL), controlling for socio-demographics, pain and other oral health clinical factors.

METHODOLOGY

OHQoL assessments were conducted amongst a consecutive sample of 412 Chinese patients requiring endodontic treatment employing the short-form Oral Heath Impact Profile (OHIP-14). Information on (i) number of teeth requiring endodontic treatment, (ii) tooth type, (iii) retreatment requirements, (iv) periapical radiolucency assessment and (v) diagnostic classification was obtained. In addition, socio-demographic information (age, gender, educational attainment and family income), pain ratings on a visual analogue scale (VAS) and other clinical oral health status information were collected.

RESULTS

Bivariate analyses identified association between number of teeth requiring endodontic treatment and summary OHIP-14 score (P < 0.01) and four of its seven domain scores (P < 0.05). Need for endodontic retreatment was associated with summary OHIP-14 score (P < 0.05) and two of its seven domain scores (P < 0.05). In regression analyses having controlled for socio-demographics, other clinical factors and pain rating amongst 15 confounding variables, patients requiring endodontic treatment for multiple teeth were more than twice as likely to have poor OHQoL (upper quintile OHIP-14 scores) compared with those requiring endodontic treatment for a single tooth (OR = 2.16, 95% CI 1.17, 3.98, P < 0.05). Pain VAS rating and age also emerged as significant factors associated with poor OHQoL in the regression analysis.

CONCLUSION

OHQoL is compromised amongst patients requiring endodontic treatment. Number of teeth requiring endodontic treatment is associated with poor OHQoL, controlling for socio-demographic and other oral health clinical and pain factors.

Microbial transformation from normal oral microbiota to acute endodontic infections

Background

Endodontic infections are a leading cause of oro-facial pain and tooth loss in western countries, and may lead to severe life-threatening infections. These infections are polymicrobial with high bacterial diversity. Understanding the spatial transition of microbiota from normal oral cavities through the infected root canal to the acute periapical abscess can improve our knowledge of the pathogenesis of endodontic infections and lead to more effective treatment. We obtained samples from the oral cavity, infected root canal and periapical abscess of 8 patients (5 with localized and 3 with systemic infections). Microbial populations in these samples were analyzed using next-generation sequencing of 16S rRNA amplicons. Bioinformatics tools and statistical tests with rigorous criteria were used to elucidate the spatial transition of the microbiota from normal to diseased sites.

Results

On average, 10,000 partial 16S rRNA gene sequences were obtained from each sample. All sequences fell into 11 different bacterial phyla. The microbial diversity in root canal and abscess samples was significantly lower than in the oral samples. Streptococcus was the most abundant genus in oral cavities while Prevotella and Fusobacterium were most abundant in diseased samples. The microbiota community structures of root canal and abscess samples were, however, more similar to each other than to the oral cavity microbiota. Using rigorous criteria and novel bioinformatics tools, we found that Granulicatella adiacens, Eubacterium yurii, Prevotella melaninogenica, Prevotella salivae, Streptococcus mitis, and Atopobium rimae were over-represented in diseased samples.

Conclusions

We used a novel approach and high-throughput methodologies to characterize the microbiota associated normal and diseased oral sites in the same individuals.

Molecular detection of transcriptionally active bacteria from failed prosthetic hip joints removed during revision arthroplasty

The purpose of this study was to use microbiological culture and bacterial 16S rRNA gene sequencing methods to detect transcriptionally active bacteria present on the surface of failed prosthetic hip joints removed during revision arthroplasty. Five failed prosthetic hip joints were sonicated to dislodge adherent bacteria and subjected to microbiological culture. Bacterial RNA was extracted from each sonicate, cDNA prepared by reverse transcription and the 16S rRNA gene amplified using universal primers. Polymerase chain reaction (PCR) products were cloned, assigned to distinct groups by restriction fragment length polymorphism (RFLP) analysis and one representative clone from each group was sequenced. Bacteria were identified by comparison of the obtained 16S rRNA gene sequences with those deposited in public access sequence databases. All five specimens were positive for the presence of bacteria by both culture and PCR. Culture methods identified species from eight genera. Molecular detection of transcriptionally active bacteria identified a wider range of species. A total of 42 phylotypes were identified, of which Lysobacter gummosus was the most abundant (31.6%). Thirty-four clones (14.5%) represented uncultivable phylotypes. No potentially novel species were identified. It is concluded that a diverse range of transcriptionally active bacterial species are present within biofilms on the surface of failed prosthetic hip joints.

Diversity of endodontic microbiota revisited

Although fungi, archaea, and viruses contribute to the microbial diversity in endodontic infections, bacteria are the most common micro-organisms occurring in these infections. Datasets from culture and molecular studies, integrated here for the first time, showed that over 460 unique bacterial taxa belonging to 100 genera and 9 phyla have been identified in different types of endodontic infections. The phyla with the highest species richness were Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria. Diversity varies significantly according to the type of infection. Overall, more taxa have been disclosed by molecular studies than by culture. Many cultivable and as-yet-uncultivated phylotypes have emerged as candidate pathogens based on detection in several studies and/or high prevalence. Now that a comprehensive inventory of the endodontic microbial taxa has been established, future research should focus on the association with different disease conditions, functional roles in the community, and susceptibility to antimicrobial treatment procedures.

EDTA treatment diminishes the antibacterial and anti-adherence effect of calcium hydroxide on Enterococcus faecalis: an in vitro study

This study sought to understand the cell surface characteristics, viability and biofilm-forming potential ofEnterococcus faecaliscells sequentially exposed to EDTA and calcium hydroxide, as in endodontic treatment. Bacterial cells exposed to EDTA and calcium hydroxide were assayed for cell viability, membrane integrity, cell surface hydrophobicity and surface charge, while alteration in the surface topography ofE. faecaliscells was examined using atomic force microscopy (AFM). The bacterial adherence potential to type I collagen was also examined to assess the biofilm-forming capacity ofE. faecaliscells exposed to EDTA and calcium hydroxide. It was found that calcium hydroxide treatment reduced the viability ofE. faecalis. However, prior exposure to EDTA significantly reduced the antibacterial effect of calcium hydroxide (P&lt; 0.05). Calcium hydroxide treatment resulted in impaired cell wall morphology, observed as increased surface roughness and pore formation under AFM. However, these topographical changes induced by calcium hydroxide were significantly reduced in EDTA pretreated cells (P&lt; 0.05). Calcium hydroxide treatment caused reduction in hydrophobicity and adherence ofE. faecalisto type I collagen. These effects due to calcium hydroxide were also significantly altered in EDTA-pretreated cells (P&lt; 0.001). The findings from this study showed that the antibacterial and anti-adherence effect of calcium hydroxide was diminished by prior exposure ofE. faecaliscells to EDTA.

Use of multiple-displacement amplification and checkerboard DNA-DNA hybridization to examine the microbiota of endodontic infections

Multiple-displacement amplification (MDA) has been used to uniformly amplify bacterial genomes present in small samples, providing abundant targets for molecular analysis. The purpose of this investigation was to combine MDA and checkerboard DNA-DNA hybridization to examine the microbiota of endodontic infections. Sixty-six samples were collected from teeth with endodontic infections. Nonamplified and amplified samples were analyzed by checkerboard DNA-DNA hybridization for levels and proportions of 77 bacterial taxa. Counts, percentages of DNA probe counts, and percentages of teeth colonized for each species in amplified and nonamplified samples were computed. Significance of differences for each species between amplified and nonamplified samples was sought with Wilcoxon signed-rank test and adjusted for multiple comparisons. The amount of DNA in the samples ranged from 6.80 (+/- 5.2) ng before to 6.26 (+/- 1.73) mug after MDA. Seventy of the 77 DNA probes hybridized with one or more of the nonamplified samples. All probes hybridized with at least one sample after amplification. Most commonly detected species at levels of >10(4) in both amplified and nonamplified samples were Prevotella tannerae and Acinetobacter baumannii at frequencies between 89 and 100% of samples. The mean number of species at counts of >10(4) in amplified samples was 51.2 +/- 2.2 and in nonamplified samples was 14.5 +/- 1.7. The endodontic microbiota was far more complex than previously shown, although microbial profiles at teeth with or without periradicular lesions did not differ significantly. Species commonly detected in endodontic samples included P. tannerae, Prevotella oris, and A. baumannii.

Photophysical, photochemical, and photobiological characterization of methylene blue formulations for light-activated root canal disinfection

Tissue-specific modification of treatment strategy is proposed to increase the antimicrobial activity of light-activated therapy (LAT) for root canal disinfection. Methylene blue (MB) dissolved in different formulations: water, 70% glycerol, 70% poly ethylene glycol (PEG), and a mixture of glycerol:ethanol:water (30:20:50) (MIX), is analyzed for photophysical, photochemical, and photobiological characteristics. Aggregation of MB molecules, as evident from monomer to dimer ratio, depends on the molar concentrations of MB, which is significantly higher in water compared to other formulations. MIX-based MB formulation effectively penetrates the dentinal tubules. Although, the affinity of MB for Enterococcus faecalis (gram positive) and Actinomycetes actinomycetemcomitans (gram negative) was found to be high in the water-based formulation, followed by MIX, the MIX-based formulation significantly enhanced the model substrate photooxidation and singlet oxygen generation compared to MB dissolved in other formulations. Finally, the efficacy of LAT is evaluated on biofilms produced by both organisms under in vitro and ex vivo conditions. A dual-stage approach that applies a photosensitization medium and an irradiation medium separately is tested. The MIX-based photosensitization medium in combination with dual-stage approach demonstrates thorough disinfection of the root canal with bacterial biofilms. This method will have potential application for root canal disinfection.

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics, non-phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.

Identification of Enterococcus faecalis in Root-filled Teeth With or Without Periradicular Lesions by Culture-dependent and—Independent Approaches

Enterococcus faecalis is the most commonly found species in root-filled teeth evincing recalcitrant periradicular lesions and as a consequence, a role in causation of endodontic treatment failure has been suggested. The purpose of this study was to evaluate the prevalence of this bacterial species in root-filled teeth with or without periradicular lesions. Identification of E. faecalis was carried out by polymerase chain reaction (PCR) or conventional culture procedures. Overall, E. faecalis was detected by species-specific 16S rRNA gene-based PCR in 40/50 teeth (80%), while culture revealed the occurrence of this species in 8/50 teeth (16%). PCR was significantly more effective than culture in detecting this bacterial species (p < 0.001). Of 27 root-filled teeth with no periradicular lesions, E. faecalis was found in 22 cases (81.5%) by PCR and in five cases (18.5%) by culture. Of 23 root-filled teeth with periradicular lesions, E. faecalis was identified in 18 cases (78%) by PCR and in three cases (13%) by culture. Regardless of the identification technique used, no significant difference was observed when comparing the occurrence of E. faecalis in root-filled teeth with and without periradicular lesions (p > 0.05). Although these findings apparently put into question the status of E. faecalis as the main species causing endodontic treatment failure, other related factors still need to be clarified before this assumption turns into certainty.

Consequences of and strategies to deal with residual post-treatment root canal infection

Bacterial sampling of prepared root canals is used to determine the presence and character of the remaining microbiota. However, it is likely that current sampling techniques only identify organisms in the main branches of the root canal system whereas it is unlikely that they can sample areas beyond the apical end-point of preparation and filling, or in lateral canals, canal extensions, apical ramifications, isthmuses and within dentinal tubules. Thus, it may be impossible by current techniques to identify residual post-treatment root canal infection. In histologic observations of root apices, bacteria have been found in inaccessible inter-canal isthmuses and accessory canals often in the form of biofilms. There is no in vivo evidence to support the assumption that these bacteria can be entombed effectively in the canal system by the root filling and thus be rendered harmless. As a consequence of this residual root infection, post-treatment apical periodontitis, which may be radiographically undetectable, may persist or develop as a defence mechanism to prevent the systemic spread of bacteria and/or their byproducts to other sites of the body. Histologic observation of root apices with surrounding bone removed from either patients or human cadavers has demonstrated that post-treatment apical periodontitis is associated with 50-90% of root filled human teeth. Thus, if the objective of root canal treatment is to eliminate apical periodontitis at a histological level, current treatment procedures are inadequate. It is essential that our knowledge of the local and systemic consequences of both residual post-treatment root infection and post-treatment apical periodontitis be improved. The continued development of treatments that can effectively eliminate root infection is therefore a priority in clinical endodontic research. Post-treatment disease following root canal treatment is most often associated with poor quality procedures that do not remove intra-canal infection; this scenario can be corrected via a nonsurgical approach. However, infection remaining in the inaccessible apical areas, extraradicular infection including apically extruded dentine debris with bacteria present in dentinal tubules, true radicular cysts, and foreign body reactions require a surgical intervention.

Treatment Outcome in Endodontics: The Toronto Study. Phase III: Initial Treatment

The 4- to 6-year outcome of initial endodontic treatment was assessed for phase III (1998-1999) of the Toronto Study. Of the 532 teeth treated, 248 were from discontinuers (excluded), 142 from dropouts, 10 extracted, and 132 (50% recall) examined for outcome: healed (no apical periodontitis [AP], signs, symptoms) or diseased. Phase III was analyzed alone and combined with phases I, II (n = 373 teeth). Logistic regression performed on the combined phases I-III sample identified significant (p < or = 0.05) outcome predictors: preoperative AP (OR = 3.5; CI 1.7-7.2; healed: absent, 93%; present, 80%), number of roots (OR = 2.2; CI 1.0-4.7; healed: 1 - 92%; > or =2 - 83%), and intraoperative complications (OR = 2.2; CI 1.1-4.5; healed: absent, 88%; present, 76%). Treatment technique (OR = 2.8; CI 1.3-6.1; healed: Schilder, 89%; alternative, 73%) was suggested as an outcome predictor in teeth with AP, requiring confirmation from randomized controlled trials.

The Role of Environmental Changes on Monospecies Biofilm Formation on Root Canal Wall by Enterococcus faecalis

Biofilm mode of growth is a strategy in microorganisms to survive harsh growth conditions. Although previous studies have established the ability of Enterococcus faecalis to survive postendodontic environmental conditions, the effect of such conditions on the ultrastructural and physiochemical features of E. faecalis biofilm has received less attention. This study aims to evaluate the effect of different growth conditions on the characteristics of E. faecalis biofilm on root canal, and the penetration of E. faecalis into dentinal tubules. Forty-five intact noncarious human maxillary molars were experimented under nutrient-rich, nutrient-deprived, aerobic, and anaerobic conditions for a period of 21 days. Scanning Electron Microscopy with Energy Dispersive X-ray microanalysis, Laser Confocal Scanning Microscopy and Light microscopic examinations were carried out. The microscopic analysis highlighted a distinct variation in the ultrastructure of the biofilms formed under different experimental conditions. The EDX microanalysis showed a significant increase in the levels of Calcium (Ca) in the biofilm structures formed under anaerobic nutrient-deprived condition (p < 0.001). The depth of bacterial penetration was significantly greater in nutrient-rich condition (p < 0.001). This study demonstrated distinct ultrastructural and physiochemical properties of the biofilms formed and dentinal tubular penetration of E. faecalis under different conditions.

Susceptibility of a polycaprolactone-based root canal filling material to degradation. I. Alkaline hydrolysis

Polycaprolactone, a thermoplastic aliphatic polyester, is reportedly susceptible to both alkaline and enzymatic hydrolyzes. This screening study examined the susceptibility of Resilon, a polycaprolactone-based root filling composite, to alkaline hydrolysis. There were 15-mm diameter disks of Resilon and Obtura gutta-percha prepared by compressive molding and immersed in 20% sodium ethoxide for 20 or 60 min. Control disks were immersed in ethanol for 60 min. These disks were examined using field-emission scanning electron microscopy and energy dispersive X-ray analysis. For Resilon, the surface resinous component was hydrolyzed after 20 min of sodium ethoxide immersion, exposing the spherulitic polymer structure and subsurface glass and bismuth oxychloride fillers. More severe erosion occurred after 60 min of sodium ethoxide treatment. Gutta-percha was unaffected after immersion in sodium ethoxide. As Resilon is susceptible to alkaline hydrolysis, it is possible that enzymatic hydrolysis may occur. Biodegradation of Resilon by bacterial/salivary enzymes and endodontically relevant bacteria warrants further investigation.

Uncultivated phylotypes and newly named species associated with primary and persistent endodontic infections

Endodontic infections have been traditionally studied by culture methods, but recent reports showing that over 50% of the oral microbiota is still uncultivable (B. J. Paster et al., J. Bacteriol. 183:3770-3783, 2001) raise the possibility that many endodontic pathogens remain unknown. This study intended to investigate the prevalence of several uncultivated oral phylotypes, as well as newly named species in primary or persistent endodontic infections associated with chronic periradicular diseases. Samples were taken from the root canals of 21 untreated teeth and 22 root-filled teeth, all of them with radiographic evidence of periradicular bone destruction. Genomic DNA was isolated directly from each sample, and 16S rRNA gene-based nested or heminested PCR assays were used to determine the presence of 13 species or phylotypes of bacteria. Species-specific primers had already been validated in the literature or were developed by aligning closely related 16S rRNA gene sequences. Species specificity for each primer pair was confirmed by running PCRs against a panel of several oral bacteria and by sequencing DNA from representative positive samples. All species or phylotypes were detected in at least one case of primary infections. The most prevalent species or phylotypes found in primary infections were Dialister invisus (81%), Synergistes oral clone BA121 (33%), and Olsenella uli (33%). Of the target bacteria, only these three species were detected in persistent infections. Detection of uncultivated phylotypes and newly named species in infected root canals suggests that there are previously unrecognized bacteria that may play a role in the pathogenesis of periradicular diseases.

Exploiting Molecular Methods to Explore Endodontic Infections: Part 2—Redefining the Endodontic Microbiota

The second part of this review discusses the application of molecular methods in endodontic microbiology research for a comprehensive characterization of the microbiota associated with different types of endodontic infections. Despite their recent introduction in endodontic research, molecular methods have already given a significant contribution to the understanding of endodontic infections and the future holds the perspective of a still better refinement of the knowledge about these infections. Molecular methods have revealed a higher complexity of the endodontic microbiota than previously reported by cultivation approaches. In addition to detecting some cultivable species in increased prevalence, molecular methods have also expanded the list of putative endodontic pathogens by inclusion of some fastidious bacterial species or even uncultivated bacteria that have never been previously found in endodontic infections.