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

Microbial composition and diversity in intraradicular biofilm formed in situ: New concepts based on next-generation sequencing

This study aimed to characterize the taxonomic composition of intraradicular multispecies biofilms (IMBs) formed in situ in a model to reproduce clinical conditions. Twelve palatal roots of maxillary molars had its canals prepared. Two roots were randomly selected to sterility control. Ten intraoral prosthetic appliances with lateral slots were fabricated. The roots were positioned in the slots with the canal access open to the oral cavity. Eight volunteers wore the appliance for 21 days, and two wore it at two different time points. One root from each appliance was removed and stored at -20°C until DNA extraction and sequencing (n = 10). Biofilm was analyzed using next-generation sequencing and bioinformatics. The V4 hyper-variable region of the 16SrRNA gene was amplified and sequenced. For data analyses, the mothur pipeline was used for 16SrRNA processing, and subsequent analyses of the sequence dataset were performed in R using the MicrobiomeAnalyst R package. The taxonomy-based analysis of bacterial communities identified 562 operational taxonomic units (OTUs), which belonged to 93 genera, 44 families, and 8 phyla. Bacterial colonization was different for each biofilm, and samples did not have the same group of bacteria. Alpha and beta diversity analysis revealed some general patterns of sample clustering. A core microbiome of prevalent OTUs and genera was identified. IMBs were heterogeneous when analyzed individually, but some diversity patterns were found after sample clustering. The experimental model seemed to reproduce the actual biofilm composition in endodontic infections, which suggests that it may be used to evaluate disinfection protocols.

Comparative evaluation of antimicrobial efficacy of different combinations of calcium hydroxide against Enterococcus faecalis

BACKGROUND

The study aims to compare the synergistic antibacterial efficacy of different combinations of calcium hydroxide as an intracanal medicament against E. faecalis.

MATERIAL AND METHODS

The current study included four hundred extracted human permanent mandibular premolar teeth. After complete chemo-mechanical preparation, the middle third of the root was sectioned using a rotary diamond disc and a total of 400 samples were obtained. The specimens were inoculated with E. faecalis for 21 days. After that, specimens were divided into five groups (n = 80) based on materials used for the disinfection of samples: Group I, calcium hydroxide alone; Group II, calcium hydroxide + 2% chlorhexidine gel; Group III, calcium hydroxide + 2% chitosan gel; Group IV, calcium hydroxide + 0.02% silver nanoparticle gel; Group V, calcium hydroxide + Bioactive glass S53P4. Dentin shavings from the apical third were obtained from the inner third of dentin were obtained using gates glidden no.1 to the apical depth, followed by no.2, 3, 4 and 5 analyzed for E. faecalis using the culture method. One-way analysis of variance (ANOVA) was used for data analysis, followed by post-hoc Tukey's test for multiple comparisons of means to check the difference in bacterial inhibition between the groups.

RESULTS

ANOVA results revealed a significant reduction of bacterial counts in all the groups compared (p < 0.001). Intergroup comparison showed maximum bacterial reduction (p < 0.001) with calcium hydroxide + bioactive glass S53P4 compared with other groups.

CONCLUSION

Synergistic effect of calcium hydroxide showed better bacterial reduction compared to calcium hydroxide alone. Among the combinations evaluated, calcium hydroxide with bioactive glass, found to be most effective compared to other groups.

Effect of systemic administration of Bifidobacterium animalis subsp. lactis HN019 on apical periodontitis

This study aimed to evaluate the effect of Bifidobacterium animalis subsp. lactis (B. lactis) HN019 in drinking water on the development of apical periodontitis (AP) in rats. In total 60 animals were divided into a control group (sound teeth); Group I - regular water without AP; Group II - probiotic water without AP; Group III - regular water with AP; Group IV - probiotic water with AP. AP was induced after 3 days in the control groups and after 7, 21, and 42 days in groups III and IV. The animals were euthanized, and the mandibles were subjected to histotechnical processing. Samples were stained with hematoxylin & eosin (H&E) to identify root canal features, apical and periapical regions. Additionally, histoenzymology was performed to detect osteoclasts, immunohistochemistry was used to identify osteoclastogenesis markers, and the Brown & Brenn technique was applied for microbiological analysis. The data were analyzed using GraphPad Prism 8.0.1 with a significance level of 5%. Although no statistical differences were observed, the groups administered with probiotics showed better conditions in terms of histological aspects seen microscopically. Furthermore, there were no differences in the number of osteoclasts (p > 0.05). The RANKL marker was not found in the probiotic group at 42 days, unlike in group III.

Antimicrobial Efficacy of a Novel Automated Irrigation Device As Compared to Conventional Needle Irrigation Against Enterococcus faecalis: An In Vitro Study

Aim The present study aims to compare the antibacterial efficacy of a novel automated endodontic irrigation device with that of a manual irrigation technique. Materials and methods The present study considered 45 extracted single-rooted teeth. After sectioning the teeth, the specimens were inoculated with Enterococcus faecalis (E. faecalis) bacteria for three weeks. Instrumentation was done using ProTaper Gold rotary files to size 50 and 5% taper. Based on the irrigation protocol, the experimental samples were divided into Group I: control (normal saline irrigation) (n = 15); Group II: conventional needle irrigation (n = 15); and Group III: automated irrigation (n = 15). The irrigation in Group III was done using the automated irrigation device. After the experimental irrigation, the pre-weighted dentinal shaving was collected in Eppendorf tubes, diluted 10 times, and incubated in the Petri dish with tryptone soy agar (TSA) for 48 hours. Finally, the colony-forming unit (CFU) counts were assessed. IBM SPSS Statistics for Windows version 23.0 (Armonk, NY, USA, IBM Corp.) was used for data analysis. Intergroup comparisons were made using the non-parametric Kruskal-Wallis test. Results The mean CFU count (CFU/ml) for the groups was: Group 1 (normal saline irrigation): 3.67x101; Group 2 (manual irrigation): 2.69× 101; Group 3 (automated irrigation): 1.57× 101. A statistically significant reduction in E. faecalis CFU count was seen among the groups assessed (p<0.01). The automated irrigation group exhibited the most substantial reduction in E. faecalis CFU count. Group 2 showed a significant difference compared to Group 1 (p<0.05). Conclusions The novel automated endodontic irrigation device was superior to manual irrigation in reducing E. faecalis CFU counts. This indicates that the automated irrigation device has the potential to enhance bacterial elimination efficacy during endodontic treatment.

Microbiome in paired root apices and periapical lesions and its association with clinical signs in persistent apical periodontitis using next-generation sequencing

AIM

To assess and compare the microbiome of paired root apices and periapical lesions from cases with failed endodontic treatment and to associate the microbiome and bacterial metabolic pathways in both sites with asymptomatic apical periodontitis (AAP) and symptomatic apical periodontitis (SAP), using next-generation sequencing (NGS).

METHODOLOGY

Matched root apices and periapical lesions of patients with failed root canal treatments were surgically extracted. Specimens were cryopulverized, bacterial DNA was extracted and the V3-V4 hypervariable regions of the 16 S rRNA gene were amplified and sequenced using the Illumina Miseq platform. Diversity and community composition were studied in the paired samples, as well as in AAP and SAP cases. Diversity indices were compared in each case by means of the Wilcoxon matched-pairs signed rank and Mann-Whitney U tests. Differences in the community composition were explored with multivariate statistical analysis and Linear discriminant analysis Effect Size (LEfSe). Bacterial functional study was performed through the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis.

RESULTS

Twenty-one paired apices and lesions were successfully sequenced and analysed, identifying a total of 21 phyla and 600 genera. A higher alpha-diversity was observed in the periapical lesions, although no global differences in the community composition between the two sites were found (p = .87), the most prevalent genera being Fusobacterium, Porphyromonas and Streptococcus. Prevotella, Clostridiales_vadinBB60_group, Bosea, Phreatobacter, Afipia and Xanthobacteriaceae_unclassified were enriched in SAP samples, while Pseudopropionibacterium, Campylobacter and Peptoniphilus were significantly more abundant in AAP cases (p < .05). Metabolic pathways involved in the amino acid metabolism or degradation and flagellum assembly were more abundant in SAP samples, whereas glucose metabolism-related pathways were associated with AAP.

CONCLUSIONS

The bacterial community composition was similar in the apices and periapical lesions. The microbiome was different in AAP and SAP samples, gram-negative bacteria showing higher relative abundances in SAP cases. An association was observed between amino acid degradation and flagellum assembly pathways, and the development of tenderness to percussion or palpation.

Taxonomic Assignment-Based Genome Reconstruction from Apical Periodontal Metagenomes to Identify Antibiotic Resistance and Virulence Factors

Primary apical periodontitis occurs due to various insults to the dental pulp including microbial infections, physical and iatrogenic trauma, whereas inadequate elimination of intraradicular infection during root canal treatment may lead to secondary apical periodontitis. We explored the complex intra-radicular microbial communities and their functional potential through genome reconstruction. We applied shotgun metagenomic sequencing, binning and functional profiling to identify the significant contributors to infection at the acute and chronic apical periodontal lesions. Our analysis revealed the five classified clusters representing Enterobacter, Enterococcus, Lacticaseibacillus, Pseudomonas, Streptococcus and one unclassified cluster of contigs at the genus level. Of them, the major contributors were Pseudomonas, with 90.61% abundance in acute conditions, whereas Enterobacter followed by Enterococcus with 69.88% and 15.42% abundance, respectively, in chronic conditions. Enterobacter actively participated in antibiotic target alteration following multidrug efflux-mediated resistance mechanisms, predominant in the chronic stage. The prediction of pathways involved in the destruction of the supportive tissues of the tooth in Enterobacter and Pseudomonas support their crucial role in the manifestation of respective disease conditions. This study provides information about the differential composition of the microbiome in chronic and acute apical periodontitis. It takes a step to interpret the role of a single pathogen, solely or predominantly, in establishing endodontic infection types through genome reconstruction following high throughput metagenomic DNA analysis. The resistome prediction sheds a new light on the therapeutic treatment guidelines for endodontists. However, it needs further conclusive research to support this outcome using a larger number of samples with similar etiological conditions, but different demographic origin.

Ex-vivo study about antimicrobial effectiveness of phytic acid against Enterococcus faecalis into root canals

BACKGROUND

Endodontic failure is due to the persistence of microorganisms, especially Enterococcus faecalis, which have become resistant to disinfection measures. Sodium hypochlorite has been traditionally used, whereas phytic acid, a natural irrigant, needs to be further investigated.

METHODS

This ex-vivo study compared the antibacterial effectiveness of 0.9% saline solution, 5% sodium hypochlorite and 5% phytic acid against Enterococcus faecalis ATCC 29212 into the apical root canal third of 96 single-rooted extracted teeth, after 1-minute push-and-pull irrigation - a basic irrigation technique. Survived microorganisms were evaluated both through a traditional colony-forming-unit count and introducing the viability PCR, which precisely detects only DNA from intact cells: dead and damaged cells were excluded thanks to a propidium monoazide dye.

RESULTS

The culture methods showed that 5% sodium hypochlorite (median: 0 CFU/mL) has a significant greater antibacterial effectiveness (P<0.001) compared both to 0.9% saline solution (median: 4.76 CFU/mL) and 5% phytic acid (median: 0.25 CFU/mL). However, 5% phytic acid proved to be significantly more effective (P<0.001) than 0.9% saline solution. The viability PCR did not reveal a significant difference between 5% sodium hypochlorite (median: 4.12×10⁴ survived bacteria) and 0.9% saline solution (median: 8.45×10⁴ survived bacteria). Five percent phytic acid (median: 0.83×10⁴ survived bacteria) was significantly more effective than both 0.9% saline solution (P<0.001) and 5% sodium hypochlorite (P<0.001).

CONCLUSIONS

The findings suggest that 5% phytic acid works against root canal bacteria even with a basic irrigation technique and viability PCR seems to lead to more reliable and sensitive data rather than the culture methods.

Evaluation of PCR primers to identify Porphyromonas endodontalis in apical periodontitis clinical samples

We aimed to evaluate whether two commonly used PCR primers are effective to identify P. endodontalis and discriminate from other prevalent black-pigmented bacteria in apical periodontitis (AP). Endodontic canal samples from patients with asymptomatic AP (n = 20) were collected and cultured in anaerobiosis. Two primer sets to detect P. endodontalis were selected from the literature and first analyzed for their specificity in silico; and then tested on clinical isolates in vitro and finally, in apical exudates ex vivo. The identity of P. endodontalis was verified by PCR and Sanger sequencing with universal primers for bacterial V3-V6 regions 16S rDNA. Only one primer set showed specificity only for P. endodontalis clones in silico and also was specific for P. endodontalis in vitro and ex vivo.

Nature and Prevalence of Bacterial Taxa Persisting after Root Canal Chemomechanical Preparation in Permanent Teeth: A Systematic Review and Meta-analysis

INTRODUCTION

Culture-independent molecular studies have shown a broad spectrum of bacterial taxa that persist after chemomechanical procedures (CMP). Therefore, this study systematically reviewed these reports to explore the prevalence of bacteria in post-instrumentation samples of root canals from permanent teeth, especially of as-yet-uncultivated/difficult-to-culture bacteria.

METHODS

Electronic databases were searched from 2007 to January 2021. Clinical studies using culture-independent molecular methods to identify species-level taxa before and after CMP were included. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist and the funnel plot analysis. The meta-analysis was performed on the prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa using RStudio.

RESULTS

A total of 3781 titles were screened, but only 20 studies were included. The most frequent species in post-instrumentation samples were Streptococcus spp., Leptotrichia buccalis, Fusobacterium nucleatum, and Capnocytophaga ochracea. The detection frequency of some species increased after CMP, including mainly Firmicutes members such as streptococci, Enterococcus faecium, Selenomonas noxia, and Solobacterium moorei. The prevalence (confidence interval) of difficult-to-culture species was as follows: Dialister invisus, 17% (7%-29%); Solobacterium moorei, 14% (8%-23%); Bacteroidaceae [G-1] bacterium HMT 272, 13% (5%-23%); and Filifactor alocis, 11% (3%-23%).

CONCLUSIONS

The prevalence of as-yet-uncultivated/difficult-to-culture bacterial taxa in post-instrumentation samples was low. The persistent species belonged mainly to the phylum Firmicutes, and streptococci were the major members. Future larger clinical studies on the composition of the whole bacterial community that persist after CMP are still necessary for a better understanding of bacterial interactions and their clinical significance in the treatment outcome.

A critical analysis of research methods and experimental models to study irrigants and irrigation systems

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro-omputed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Biocompatibility and Antibacterial Action of Salvadora persica Extract as Intracanal Medication (In Vitro and Ex Vivo Experiment)

This study aimed to test the biocompatibility and antibacterial properties of Salvadora persica (S. persica) extract, a natural product, as an intracanal medication in comparison with calcium hydroxide (Metapaste, META BIOMED, Cheongju, Korea). The pH values of both materials were tested. The biocompatibility of S. persica extract and Metapaste was determined using light microscopy and MTT assays. The antibacterial action was tested using the zone of bacterial inhibition on four common bacterial species. In addition, intracanal medication was administered using 68 extracted single-rooted teeth contaminated with Enterococcus faecalis (E. faecalis), and the percentage reduction in colony count (% RCC) at 1, 3, and 7 days was measured. The extension of activity for both materials was assessed using histological sections and scanning electron microscopy. S. persica was found to be acidic in nature. Both materials showed significantly lower cell viability than the positive control cells on days 1 and 3 but not on day 7. S. persica showed better antibacterial effects against E. faecalis and S. mutans. S. persica extract showed 97.6%, 98.9%, and 99.3% RCC values at 1, 3, and 7 days, respectively, which are comparable to those of Metapaste. S. persica herbal extract is a promising material that can be utilized as an intracanal medication, but its use requires further research.

Microbiological Aspects of Root Canal Infections and Disinfection Strategies: An Update Review on the Current Knowledge and Challenges

The oral cavity is the habitat of several hundreds of microbial taxa that have evolved to coexist in multispecies communities in this unique ecosystem. By contrast, the internal tissue of the tooth, i.e., the dental pulp, is a physiologically sterile connective tissue in which any microbial invasion is a pathological sign. It results in inflammation of the pulp tissue and eventually to pulp death and spread of inflammation/infection to the periradicular tissues. Over the past few decades, substantial emphasis has been placed on understanding the pathobiology of root canal infections, including the microbial composition, biofilm biology and host responses to infections. To develop clinically effective treatment regimens as well as preventive therapies, such extensive understanding is necessary. Rather surprisingly, despite the definitive realization that root canal infections are biofilm mediated, clinical strategies have been focused more on preparing canals to radiographically impeccable levels, while much is left desired on the debridement of these complex root canal systems. Hence, solely focusing on "canal shaping" largely misses the point of endodontic treatment as the current understanding of the microbial aetiopathogenesis of apical periodontitis calls for the emphasis to be placed on "canal cleaning" and chemo-mechanical disinfection. In this review, we dissect in great detail, the current knowledge on the root canal microbiome, both in terms of its composition and functional characteristics. We also describe the challenges in root canal disinfection and the novel strategies that attempt to address this challenge. Finally, we provide some critical pointers for areas of future research, which will serve as an important area for consideration in Frontiers in Oral Health.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

Present status and future directions - microbiology of endodontic infections

Apical periodontitis has a microbial aetiology and is one of the most common inflammatory diseases that affect humans. Fungi, archaea and viruses have been found in association with apical periodontitis, but bacteria are by far the most prevalent and dominant microorganisms in endodontic infections. Bacterial infection of the root canal system only occurs when the pulp is necrotic or was removed for previous treatment. In some specific cases, including acute and chronic abscesses, the bacterial infection may reach the periradicular tissues. Intracanal bacteria are usually observed as sessile multispecies communities (biofilms) attached to the dentinal root canal walls. Infection in the main root canal lumen can spread to other areas of the root canal system. Although more than 500 bacterial species have been detected in endodontic infections, a selected group of 20 to 30 species are most frequently detected and may be considered as the core microbiome. There is a high interindividual variability in the endodontic microbiome in terms of species composition and relative abundance. Obligate anaerobic species are more abundant in the intraradicular bacterial communities of teeth with primary apical periodontitis, while both anaerobes and facultatives dominate the communities in post-treatment apical periodontitis. Bacterial interactions play an essential role in determining the overall virulence of the community, which has been regarded as the unit of pathogenicity of apical periodontitis. This article reviews the microbiologic aspects of endodontic infections and provides perspectives for future research and directions in the field.

A critical analysis of research methods and experimental models to study the root canal microbiome

Endodontic microbiology deals with the study of the microbial aetiology and pathogenesis of pulpal and periradicular inflammatory diseases. Research in endodontic microbiology started almost 130 years ago and since then has mostly focussed on establishing and confirming the infectious aetiology of apical periodontitis, identifying the microbial species associated with the different types of endodontic infections and determining the efficacy of treatment procedures in eradicating or controlling infection. Diverse analytical methods have been used over the years, each one with their own advantages and limitations. In this review, the main features and applications of the most used technologies are discussed, and advice is provided to improve study designs in order to properly address the scientific questions and avoid setbacks that can compromise the results. Finally, areas of future research are described.

A Pilot Study of Chronological Microbiota Changes in a Rat Apical Periodontitis Model

Apical periodontitis caused by microbial infection in the dental pulp is characterized by inflammation, destruction of the pulpal and periradicular tissues, and alveolar bone resorption. We analyzed the chronological changes in microbiota using a pyrosequencing-based approach combined with radiologic and histopathologic changes in a rat apical periodontitis model. During the three-week observation, the pulp and periapical area showed a typical progress of apical periodontitis. A total of 27 phyla, 645 genera, and 1276 species were identified. The root apex had a lower bacterial species diversity than the pulp chamber. Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were dominant phyla in both the pulp chamber and root apex. Remarkably, bacterial communities showed a tendency to change in the root apex based on the disease progression. At the genus level, Escherichia, Streptococcus, Lactobacillus, Rodentibacter, and Bacteroidetes were dominant genera in the pulp chamber. The most abundant genera in the root apex were Bradyrhizobium, Halomonas, and Escherichia. The species Azospirillum oryzae increased in the pulp chamber, whereas the species Bradyrhizobium japonicum and Halomonas stevensii were highly observed in the root apex as the disease progressed. The experimental rat model of apical periodontitis demonstrated a relationship between the microbiota and the apical periodontitis progression.

Antimicrobial activities of natural plant compounds against endodontic pathogens and biocompatibility with human gingival fibroblasts

OBJECTIVES

The aim of the present study was to investigate three licorice-derived polyphenols (glabridin, licochalcone A, licoricidin) as well as cinnamon oil for their antimicrobial activities against major endodontic pathogens: Enterococcus faecalis, Streptococcus mutans, Actinomyces israelii, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas endodontalis, and Candida albicans. The synergistic interactions between the four compounds and chlorhexidine were assessed on E. faecalis. Lastly, the biocompatibility of the tested compounds was assessed using human gingival fibroblasts.

DESIGN

Minimal inhibitory concentrations (MIC) and minimal microbicidal concentrations (MMC) were determined using a microplate dilution assay. A luminescence assay monitoring adenosine triphosphate was used to assess the antimicrobial activity of the tested compounds against E. faecalis biofilm. The synergistic effects of the tested compounds in association with chlorhexidine were evaluated using the checkerboard technique. Cytotoxicity toward human gingival fibroblasts was assessed by determination of cell metabolic activity using a colorimetric assay.

RESULTS

Cinnamon oil showed the strongest microbicidal activity. Licochalcone A, licoricidin, and glabridin had MIC values ranging from 1.56 to 25 μg/mL against the six endodontic bacterial pathogens. The natural plant compounds were active to various extents against E. faecalis embedded in a biofilm. Synergistic antibacterial effects between chlorhexidine and the compounds, mainly glabridin, were observed against E. faecalis. Following a 2-h exposure, licochalcone A, licoricidin, and glabridin demonstrated no cytotoxicity toward gingival fibroblasts at concentrations up to 50 μg/mL, while cinnamon oil and, to a lesser extent, chlorhexidine displayed some cytotoxicity.

CONCLUSIONS

The present study provides evidence that the natural plant compounds tested show promise as root canal disinfection agents.

Quantitative Polymerase Chain Reaction Analysis of Cariogenic Streptococcus mutans in Saliva of Oral and Laryngeal Cancer Patients Undergoing Radiotherapy: A Clinical Study

CONTEXT

Radiotherapy leads to radiation-induced caries. There is limited knowledge about the quantification of cariogenic bacteria in the saliva of irradiated cancer patients.

OBJECTIVE

The aim of this study is to check salivary pH, flow rate, and the assessment of Streptococcus mutans in the saliva of irradiated oral and laryngeal cancer patients using quantitative real-time polymerase chain reaction (qRT-PCR).

SETTINGS AND DESIGN

This was time-bound study which consisted of 26 cancer patients undergoing radiotherapy (13-oral cancer 13-laryngeal cancer).

SUBJECTS AND METHODS

Resting saliva samples were gathered from oral (Group-I) and laryngeal (Group-II) cancer patients immediately before radiotherapy and after completion of radiotherapy (dose-60 Gy). pH of saliva and the salivary flow rate was measured. S. mutans were analyzed using qRT PCR.

STATISTICAL ANALYSIS USED

Data were analyzed using SPSS software 20. Paired t-test was used to evaluate salivary pH, flow rate, and amount of S. mutans pre- and post-radiotherapy for Group I and II. Independent t-test was used to compare salivary pH, flow rate, and S. mutans pre- and post-radiotherapy between Group I and II.

RESULTS

Salivary pH and flow rate significantly reduced postradiotherapy in oral and laryngeal cancer patients (P < 0.001). The amount of S. mutans statistically increased postradiotherapy in oral cancer patients (P = 0.001). While S. mutans count was statistically insignificant in laryngeal cancer patients (P = 0.091). There was a significant increase in the amount of S. mutans in Group I when compared with Group II (P = 0.002).

CONCLUSION

Amount of S. mutans increased postradiotherapy in oral cancer patients. While the salivary pH and salivary flow rate reduced postradiotherapy.

Novel Approaches to Detect and Treat Biofilms within the Root Canals of Teeth: A Review

Biofilms located within the root canals of teeth are a unique and pressing concern in dentistry and in medical microbiology. These multispecies biofilms, which include fungi as well as bacteria, form in a protected site with low shear stress and low oxygen tension. Systemic antibiotics are of limited value because of the lack of blood flow of the site, and issues with innate and acquired resistance. Physical disruption using hand or rotary powered instruments does not reach all locations in the root canal system where biofilms are present. Alternative strategies including agitated irrigation fluids, continuous chelation, materials with highly alkaline pH, and antimicrobial nanoparticles are being explored to meet the challenge. Detection and quantification of biofilms using fluorescence-based optical methods could provide an indication of successful biofilm removal and an endpoint for physical and chemical treatments.

Effect of passive ultrasonic activation on microorganisms in primary root canal infection: a randomized clinical trial

OBJECTIVE

This clinical study sought to evaluate the effectiveness of passive ultrasonic activation (PUA) in eliminating microorganisms in primary endodontic infection (PEI) after instrumentation of root canals using microbiological culture and checkerboard DNA-DNA hybridization.

METHODOLOGY

Twenty root canals with PEI and apical periodontitis were selected. The root canals were instrumented and then randomly divided into 2 groups, according to the irrigation method: PUA and conventional needle irrigation (CNI). Microbiological samples were collected before instrumentation (S1), after instrumentation (S2) and after irrigation with 17% EDTA (S3). The samples were subjected to anaerobic culture technique and checkerboard DNA-DNA hybridization analysis.

RESULTS

A statistically significant difference was found between CNI (23.56%) and PUA (98.37%) regarding the median percentage values for culturable bacteria reduction (p<0.05). In the initial samples, the most frequently detected species was S. constellatus (50%), and after root canal treatment was E. faecalis (50%).

CONCLUSION

Both treatments significantly decreased the number of bacterial species compared with the initial sample. However, no statistical difference in the total microbial load between PUA and CNI groups was detected. The number of cultivable anaerobic bacteria reduced significantly using PUA, and the bacterial composition and number of bacterial species after using either CNI or PUA was similar.

Significance of oral health in adult patients with congenital heart disease

Due to improved diagnosis and treatment life expectancy of patients with congenital heart disease is steadily increasing resulting in a growing portion of adult patients. When entering, adulthood patients commonly show a shift in their specific needs for medical care. Since the treatment is mostly not curative many patients have life-long cardiovascular anomalies, among others, entailing high risk for the development of infective endocarditis. Several oral diseases, i.e., caries, apical periodontitis and periodontitis show a very high overall prevalence. These entities are primarily initiated by bacterial infections. Hence, they cause an inherent risk for bacteremia and subsequently for infective endocarditis in patients with congenital heart disease during professional dental care and various daily activities. Conversely congenital heart disease seems to be inevitably associated with considerable impairment of oral health resulting in a tight interrelation between both entities. Different preventive strategies are available to address the elevated risk for infective endocarditis due to oral diseases in patients with congenital heart disease during professional dental care and routine daily activities. This review delineates the current evidence regarding the issue of oral health in adult patients with congenital heart disease.

Maintenance of the aseptic working field during endodontic treatment

Objective: The aim of this clinical quality study was to determine whether the aseptic working field is maintained during the endodontic procedure. Materials and methods: Bacterial samples were collected from the rubber dam of 27 patients during endodontic treatment performed by postgraduate students at the Department of Endodontics, University of Oslo. A bacterial sample was first obtained immediately after disinfection of the working field (A), and the second sample was collected just before obturation or dressing with calcium hydroxide cement (B). Aerobic cultivation technique and PCR were used for detection of bacterial growth and species. Results: All samples were negative on culturing except in one case, which showed positive results with cultivation in both sample A and B. Specie detected with cultivation technique were Streptococcus mitis. With PCR technique, 6 samples in 5 patients (11%), showed positive results. Species detected with PCR technique were Bacteroidales spp. Propionibacterium spp., Bacteroidetes spp., Prevotella nigrescens, Haemophilus parainfluenzae, Neisseria elongata, Alloprevotella tannerae, Capnocytophaga granulosa, Cardiobacterium hominis, Fusobacterium nucleatum and Streptococcus mitis. Conclusion: The present study showed that an aseptic working field was maintained throughout the endodontic procedure in 81% (22/27) of the cases after disinfection of the rubber dam.

Novel Approaches to the Control of Oral Microbial Biofilms

Effective management of biofilm-related oral infectious diseases is a global challenge. Oral biofilm presents increased resistance to antimicrobial agents and elevated virulence compared with planktonic bacteria. Antimicrobial agents, such as chlorhexidine, have proven effective in the disruption/inhibition of oral biofilm. However, the challenge of precisely and continuously eliminating the specific pathogens without disturbing the microbial ecology still exists, which is a major factor in determining the virulence of a multispecies microbial consortium and the consequent development of oral infectious diseases. Therefore, several novel approaches are being developed to inhibit biofilm virulence without necessarily inducing microbial dysbiosis of the oral cavity. Nanoparticles, such as pH-responsive enzyme-mimic nanoparticles, have been developed to specifically target the acidic niches within the oral biofilm where tooth demineralization readily occurs, in effect controlling dental caries. Quaternary ammonium salts (QAS) such as dimethylaminododecyl methacrylate (DMADDM), when incorporated into dental adhesives or resin composite, have also shown excellent and durable antimicrobial activity and thus could effectively inhibit the occurrence of secondary caries. In addition, custom-designed small molecules, natural products and their derivatives, as well as basic amino acids such as arginine, have demonstrated ecological effects by modulating the virulence of the oral biofilm without universally killing the commensal bacteria, indicating a promising approach to the management of oral infectious diseases such as dental caries and periodontal diseases. This article aims to introduce these novel approaches that have shown potential in the control of oral biofilm. These methods may be utilized in the near future to effectively promote the clinical management of oral infectious diseases and thus benefit oral health.

Etiologic role of root canal infection in apical periodontitis and its relationship with clinical symptomatology

Evidence shows the polymicrobial etiology of endodontic infections, in which bacteria and their products are the main agents for the development, progression, and dissemination of apical periodontitis. Microbial factors in necrotic root canals (e.g., endotoxin) may spread into apical tissue, evoking and supporting a chronic inflammatory load. Thus, apical periodontitis is the result of the complex interplay between microbial factors and host defense against invasion of periradicular tissues. This review of the literature aims to discuss the complex network between endodontic infectious content and host immune response in apical periodontitis. A better understanding of the relationship of microbial factors with clinical symptomatology is important to establish appropriate therapeutic procedures for a more predictable outcome of endodontic treatment.

Illumina MiSeq Sequencing for Preliminary Analysis of Microbiome Causing Primary Endodontic Infections in Egypt

The use of high throughput next generation technologies has allowed more comprehensive analysis than traditional Sanger sequencing. The specific aim of this study was to investigate the microbial diversity of primary endodontic infections using Illumina MiSeq sequencing platform in Egyptian patients. Samples were collected from 19 patients in Suez Canal University Hospital (Endodontic Department) using sterile # 15K file and paper points. DNA was extracted using Mo Bio power soil DNA isolation extraction kit followed by PCR amplification and agarose gel electrophoresis. The microbiome was characterized on the basis of the V3 and V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device. MOTHUR software was used in sequence filtration and analysis of sequenced data. A total of 1858 operational taxonomic units at 97% similarity were assigned to 26 phyla, 245 families, and 705 genera. Four main phyla Firmicutes, Bacteroidetes, Proteobacteria, and Synergistetes were predominant in all samples. At genus level, Prevotella, Bacillus, Porphyromonas, Streptococcus, and Bacteroides were the most abundant. Illumina MiSeq platform sequencing can be used to investigate oral microbiome composition of endodontic infections. Elucidating the ecology of endodontic infections is a necessary step in developing effective intracanal antimicrobials.

Diagnostic accuracy of multiplex real-time PCR approaches compared with cultivation -based detection methods: Monitoring the endopathogenic microbiota pre and post photo-activated disinfection

BACKGROUND

Several microbial species have been implicated in the pathogenesis of endodontic diseases that colonize the infected root canal system. Since the complete removal of endopathogenic agents is essential in endodontic infection therapy, photo-activated disinfection (PAD) is suggested as an alternative method to traditional antimicrobial therapy. Recent studies reported that the molecular methods with low sensitivity and high efficiency to identify fastidious anaerobic endopathogenic microbiota can be replaced by the cultivation-based approaches. This study aimed to validate the multiplex real-time PCR in order to identify six common microorganisms associated with the endodontic infections before and after the PAD.

MATERIALS AND METHODS

Microbial specimens from the root canals of 50 patients with primary and secondary endodontic infections were collected before PAD treatment using sterile paper points. Toluidine blue O (TBO)-mediated PAD was performed on the root canals, followed by resampling. The prePAD- and postPAD-treatment endodontic samples were transferred to a transport medium and six target microorganisms were then identified from the samples using the microbiological culture techniques and multiplex real-time PCR approach.

RESULTS

Multiplex real-time PCR could represent the presence of all target microorganisms in 100% cases before and after the PAD. Before PAD, using the culture method, Enterococcus faecalis (100%) was found to be the most frequent, followed by Veillonella parvula (97.5%), Aggregatibacter actinomycetemcomitans (94.7%), Porphyromonas gingivalis (84.3%), Lactobacillus rhamnosus (84.3%), and Actinomyces naeslundii (66.6%); whereas, after PAD these microbial frequencies changed to 80%, 83.3%, 66.6%, 80%, 66.6%, and 33.3%, respectively. The sensitivity and negative predictive value of the multiplex real-time PCR were 100% before and after the PAD, whereas the highest and the lowest specificities were 100% and 82% before PAD, and 97% and 89% after PAD for E. faecalis and P. gingivalis, respectively. The highest (100%) and the lowest (66%) positive predictive values were for V. parvula and A. naeslundii before and after the PAD, respectively.

CONCLUSION

As observed from the results, multiplex real-time PCR demonstrated high sensitivity and specificity when compared to the culture technique. Therefore, it can prove to be a highly sensitive technique to detect the endodontic infections microflora.

Frequency and levels of candidate endodontic pathogens in acute apical abscesses as compared to asymptomatic apical periodontitis

Introduction

Acute apical abscess is caused by bacteria that leave the infected dental root canal to invade the periodontal tissues. Most species occurring in abscesses are also found in asymptomatic infections; therefore, the possibility exists that not only the presence of certain species but also their specific counts influence the appearance of symptoms. This molecular study compared the frequency and levels of several candidate endodontic pathogens in teeth with acute apical abscesses and asymptomatic apical periodontitis.

Methods

Samples were taken from the root canals of teeth with asymptomatic apical periodontitis (n = 73) and by aspiration of purulent exudate from acute abscesses (n = 55). DNA was extracted from samples and bacterial identifications were performed by a closed-ended semi-quantitative reverse-capture checkerboard approach targeting 40 bacterial species/phylotypes.

Results

Bacterial DNA was detected in all cases. In abscesses, the most prevalent taxa were Fusobacterium nucleatum (60%), Porphyromonas endodontalis (53%), Parvimonas micra (51%), and Streptococcus species (45%). The most frequently detected taxa in asymptomatic teeth were P. endodontalis (63%), Dialister invisus (58%), Olsenella uli (56%), and F. nucleatum (51%). None of the targeted taxa were significantly associated with abscesses when only mere presence was evaluated (p>0.05). However, semi-quantitative data demonstrated that P. endodontalis, Prevotella baroniae, Treponema denticola and Streptococcus species were significantly more frequent at levels >10⁵ in abscesses than in asymptomatic cases (p<0.05).

Conclusion

None of the target species/phylotypes were associated with abscesses in terms of frequency. However, some taxa were significantly found in higher levels in abscesses. Presence of a potentially virulent pathogen in high counts may increase the collective pathogenicity of the bacterial community and give rise to symptoms.

Antibiotic and Analgesic Prescription Patterns among Dentists or Management of Dental Pain and Infection during Endodontic Treatment

OBJECTIVE

The aim of this study was to determine prescription patterns of antibiotics and analgesics among dentists in the management of dental pain and infection for medically healthy patients undergoing endodontic management.

MATERIALS AND METHODS

This descriptive cross-sectional survey was based on a structured questionnaire. The questionnaire collected data on age, gender, years of experience, and the qualifications of dentists. Feedback on prescription patterns for antibiotics and analgesics was collected for a number of clinical scenarios. Participants' choices regarding the type, dose, and duration of antibiotics/analgesics were recorded. Completed questionnaires were analyzed using the Statistical Package for Social Sciences (SPSS; version 24) to determine relationships between prescription patterns, age, gender, and educational qualification.

RESULTS

Of the 227 participants surveyed, 190 (83.7%) did not prescribe antibiotics for patients complaining of severe pain. There were significant associations between age and years of experience and antibiotic prescription for pain management (p = 0.035 and 0.04, respectively). Of the participants, 199 (87.7%) never prescribed antibiotics for reversible pulpitis with normal periapical area; there was a statistical significance in relation to gender (p = 0.044). Amoxicillin 500 mg was prescribed most of the time (51.5%). Diclofenac K (50 mg) was prescribed by 41% of the participants, while 39.2% of the participants very often prescribed ibuprofen (600 mg).

CONCLUSION

Most dentists prescribed analgesics and antibiotics as recommended, but more education on the proper use of these medicines is needed for dentists and patients.

Discuss the role of microorganisms in the aetiology and pathogenesis of periapical disease

The literature indicates that microorganisms have a critical role in the aetiology and pathogenesis of apical periodontitis. The advancement in microbiological study methods has allowed for the identification of newer species associated with the disease process. At our current understanding, however, the exact roles of specific microorganisms in apical periodontitis are not fully understood but the poly-microbial aetiology of the disease appears to be supported by the literature. The endodontic microbiota is comprised of a subset of microbiota present in the oral cavity, consisting of predominantly anaerobic bacterial species, some fungal and viral species. The pathogenesis of apical periodontitis is essentially the result of a complex interplay between bacterial and host factors, giving rise to a range of presentations depending on the balance of the interaction. The role of endodontic microbiota in the initiation and persistence of apical periodontitis means that the mainstay of endodontic treatment is the elimination of such bacteria. A challenge to the resolution of apical periodontitis after treatment lies in the inadequacy of treatment protocol in completely eradicating the pathogenic species and the inherent ability of certain species to survive the treatment. This issue should be the focus of future research as we continually search for more predictable treatment methods of achieving the resolution of apical periodontitis.

Prescription of antibiotics for pulpal and periapical pathology among dentists in southern Saudi Arabia

OBJECTIVES

Few dental conditions require treatment with antibiotics, yet dentists account for 7% of antimicrobial prescribing. In light of the emerging global problem of antibiotic resistance, this fact is problematic. Little is known about the antibiotic prescribing practices of dentists in Saudi Arabia. This study therefore aimed to investigate the attitudes of dentists in Saudi Arabia towards the prescription of antibiotics for pulpal and periapical pathology.

METHODS

This was a cross-sectional study involving an online questionnaire on antibiotic prescribing practices. A total of 195 dentists in three areas of southern Saudi Arabia (Najran, Gizan and Asser) completed the survey.

RESULTS

No significant differences in prescribing habits were found among respondents according to age, sex, level of education or time in endodontic practice. The percentage of respondents who reported that they would prescribe antibiotics for five endodontic conditions not requiring antibiotic treatment ranged from 8.1% to 28.1%. Most respondents (81.9%) would correctly prescribe antibiotics for a necrotic pulp with acute apical periodontitis and swelling; this result was consistent with previous studies. Reported antibiotic usage among the surveyed dentists was quite high.

CONCLUSIONS

Relatively high antibiotic use suggests a need to educate both dentists and patients about restricting the use of antibiotics to cases of severe infection and when indicated. More educational initiatives to rationalise the use of antibiotics in dental practice are needed to avoid further contributing to antibiotic resistance.

Worldwide pattern of antibiotic prescription in endodontic infections

BACKGROUND

Odontogenic infections, and especially endodontic infections, are polymicrobial, involving a combination of Gram-positive and Gram-negative facultative anaerobes and strictly anaerobic bacteria. Therefore, antibiotics can be used as an adjunct to endodontic treatment. However, most chronic and even acute endodontic infections can be successfully managed by disinfection of the root-canal system, which eliminates the source of infection, followed by abscess drainage or tooth extraction, without the need for antibiotics. The literature provides evidence of inadequate prescribing practices by dentists. The aim of this concise review was to analyse the worldwide pattern of antibiotic prescription in endodontic infections.

METHODS

Comprehensive searches were conducted in MEDLINE/PubMed, Wiley Online Database, Web of Science and Scopus. The databases were searched up to 13 March 2016 for studies in which dentists used systemic antibiotics to treat endodontic lesions and which reported data on the type of antibiotic prescribed and on the diagnosis of the endodontic disease treated.

RESULTS

The electronic and hand searches identified 69 titles, of which 25 were included in the final analysis. Amoxicillin was reported as the drug of choice for endodontic infections in most countries, and clindamycin and erythromycin were the choice for patients allergic to penicillin. Dentists worldwide prescribe antibiotics for non-indicated conditions, such as pulpitis.

CONCLUSION

Antibiotics are overprescribed for the management of endodontic infections. It is necessary to improve antibiotic-prescribing habits in the treatment of endodontic infections, as well as to introduce educational initiatives to encourage the coherent and proper use of antibiotics in such conditions.

The evaluation of cultivable microbiota profile in patients with secondary endodontic infection before and after photo-activated disinfection

BACKGROUND

Secondary/persistent endodontic infection can be the outcome of failure of endodontic treatment. Photo-activated disinfection (PAD) can be a useful adjunct to mechanical and antimicrobial agents in eliminating endopathogenic microorganisms. In this study, we evaluated the effect of PAD on diversity and count of microbiota related to secondary/persistent endodontic infections.

MATERIALS AND METHODS

Root canal samples were taken using sterile paper points from the root canals of 14 patients with secondary/persistent endodontic infections after removing the root-canal filling materials. PAD was performed on teeth with toluidine blue O (TBO) in combination with diode laser. Then re-sampling was conducted from the canal root using sterile paper points and transferred to transport medium. The samples were plated and pure cultures of the target microorganisms were then isolated and identified by analytical profile index (API ^® 20A) assays and 16S ribosomal RNA gene sequencing.

RESULTS

Before TBO-PAD, a total of 31 cultivable isolates could be retrieved; 25.8% of the isolated species were obligate anaerobic or microphilics including Veillonella parvula, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Propionibacterium acnes, and Lactobacillus acidophilus, and 74.2% of the isolated species were facultative anaerobic such as Enterococcus faecalis, Actinomyces naeslundii, L. rhamnosus, L. casei, Streptococcus sanguinis, S. mitis, and Candida albicans. According to this in vivo study, the diversity and count of microbiota in root canal-treated teeth were decreased after TBO-PAD, so that E. faecalis, V. parvula, and C. albicans were the microorganisms that recovered after PAD.

CONCLUSION

TBO-PAD is an effective approach that exhibited anti-microbial potential activity against microbiota involved in secondary/persistent endodontic infection.

Evaluation of Bacteriological Profile in the Apical Root Segment of the Patients with Primary Apical Periodontitis

INTRODUCTION

Apical periodontitis usually results from bacterial accumulation and contamination occurring in the root-canal system, and extending beyond the apical foramen to involve the periapical tissues. Literature has a paucity of the studies that stress on the division and analysis of the pulp canal segments. The reason for this disparity might be the technique used for collecting the samples from the pulp canals. Hence, we carried out the present study to evaluate the microbial flora in the apical part of the roots with necrotic pulp canals.

MATERIALS AND METHODS

The present study included the assessment of 40 freshly extracted teeth that had necrotized pulpal tissue along with the presence of periapical periodontal lesions. Removal of the soft tissue lesions attached to the root portion of the teeth along with apical periodontal lesions was done with the help of scalpel blade, after rinsing them with a sterile solution of saline. Thorough cleaning of the root surfaces was done with hydrogen peroxide followed by rapid disinfection with the help of sodium hypochlorite at varying concentrations. Sectioning of the root portion of all the specimens with the help of a disk was done perpendicular to the long axis of the teeth at a distance of roughly 5 to 6 mm from the teeth's apicalmost point. Cryotubes were used for transferring the specimens of apical portions containing 1 mL of buffer and were subjected to immediate frozen processing at a temperature of -20°C. A 10 K-type file was used for the initial collection of the samples followed by subsequent incubation of the files and paper pints in the incubation cabinet. Subsequent deoxyribonucleic acid (DNA) extraction from the samples was done following the procedure described by Siqueira et al. Paster et al's modification of the reverse-capture checkerboard assay was used in the present study. Semiquantitative data were used for overcoming the difficulties arising due to obtaining the counts of the polymerase chain reaction (PCR)-based analysis of specimens.

RESULTS

A positive result for the 16S ribosomal ribonucleic acid (rRNA) gene primer was observed only in two examined specimens of all the samples of the apical portion of the root canals in the present study. Negative result was shown by all the control group specimens, which were sterile samples. Presence of bacteria was confirmed by PCR in 38 out of 40 examined specimens. Amount of bacterial taxa, out of these 24 samples, ranged up to 6. Pseudoramibacter alactolyticus, Porphyromonas endodontalis, Dialister oral species, Bacteroidetes species, Streptococcus species, Olsenella uli, Synergistes species, Fusobacterium nucleatum, Parvimonas micra, Treponema denticola, and Filifactor alocis were the specific species detected. Bacteroidetes species was the only species that were detected at levels at or above 10⁵. Heavy bacterial infections were noticed in more than 45% of the cases at the periradicular part of the root canals.

CONCLUSION

Microbial flora of the apical segment of the root with necrotized pulp tissue comprises a vast variety of pathogenic bacteria.

CLINICAL SIGNIFICANCE

For better prognosis of the treatment of such cases, adequate knowledge of the microbial flora of the root, especially the apical portion is necessary.

Efficacy of Specific Plant Products on Microorganisms Causing Dental Caries

INTRODUCTION

Dental caries and periodontal diseases are the most common oral diseases seen globally, both in developed and developing countries. Oral microorganisms that is gram positive and gram negative bacteria are known to be involved in causation of these diseases. Nowadays commercially available dentrifices and mouth rinses are known to contain ingredients that can alter the oral microbial flora and have undesirable side effects such as vomiting, diarrhoea, disarrangement of oral, intestinal flora and tooth staining. Naturally available plant products are known to be less harmful with fewer side effects and also economical for the patient.

AIM

The aim of this study was to determine the antimicrobial properties of 10 naturally available plant products against oral microorganisms causing caries and to check the efficacy of these products in-vitro and to use these in mouth washes and dentrifices.

MATERIALS AND METHODS

Sample of caries material was scrapped out from the extracted teeth and transferred to liquid broth, streaked over the agar media to allow for the growth of microorganisms. Plant products like clove oil, neem, ginger-garlic paste, tea tree oil, ginger, garlic, cinnamon oil, green tea, eucalyptus oil and turmeric were used. Antimicrobial efficacy of these products, was estimated by measuring zones of inhibition in the nutrient agar media.

RESULTS

Clove oil was the most effective of all products against microorganisms causing caries with zone of inhibition - 30mm followed by ginger-garlic paste - 25mm, Neem - 15mm, tea tree oil - 15mm.

CONCLUSION

Based on the above results, it can be inferred that these natural products have the maximum efficacy against microorganisms and can be recommended in dentifrices, mouth rinses, topical gels, etc.

Microbiome in the Apical Root Canal System of Teeth with Post-Treatment Apical Periodontitis

INTRODUCTION

Bacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis. This study used a next-generation sequencing approach to identify the bacterial taxa occurring in cryopulverized apical root samples from root canal-treated teeth with post-treatment disease.

METHODS

Apical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. DNA was extracted from the powder and the microbiome was characterized on the basis of the V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device.

RESULTS

All samples were positive for the presence of bacterial DNA. Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity. Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. In general, these 4 phyla accounted for approximately 80% of the distinct OTUs found in the apical root samples. Proteobacteria was the most abundant phylum in 6/10 samples. Fourteen genera had representatives identified in all cases. Overall, the genera Fusobacterium and Pseudomonas were the most dominant. Enterococcus was found in 4 cases, always in relatively low abundance.

CONCLUSIONS

This study showed a highly complex bacterial community in the apical root canal system of adequately treated teeth with persistent apical periodontitis. This suggests that this disease is characterized by multispecies bacterial communities and has a heterogeneous etiology, because the community composition largely varied from case to case.

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.

Evolution of resistance to cationic biocides in Streptococcus mutans and Enterococcus faecalis

OBJECTIVES

The aim of this study was to investigate whether Streptococcus mutans and Enterococcus faecalis develop resistance to the cationic biocides chlorhexidine (CHX), cetylpyridinium chloride (CPC), and 12-methacryloyloxydodecylpyridinium bromide (MDPB).

METHODS

The minimum inhibitory concentrations (MICs) of CHX, CPC, and MDPB were assessed after repeated exposure of S. mutans and E. faecalis to these biocides. Cell-surface hydrophobicity and protein expression profiles of bacterial cells were examined to elucidate possible resistance mechanisms.

RESULTS

The MIC of CHX against E. faecalis showed constant increases up to 10 passages. No changes in the MICs of CPC and MDPB against E. faecalis were observed. The MICs of CHX, CPC, and MDPB against S. mutans did not increase. The surface hydrophobicity of E. faecalis significantly increased with increasing exposure to CHX and CPC. However, changes in protein expression profiles were only found in CHX-adapted E. faecalis, as evidenced by the emergence of a novel, approximately 19-kDa band following sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

CONCLUSIONS

While E. faecalis and S. mutans did not exhibit increased resistance to CPC or MDPB, repeated exposure of E. faecalis to CHX led to resistance. It is likely that the acquisition of resistance is related to an altered protein composition.

CLINICAL SIGNIFICANCE

Alkyl pyridinium compounds, such as CPC and MDPB, could have a lower risk to cause adaptation of E. faecalis, which is advantageous compared with CHX.

Evaluation of Enterococcus faecalis adhesion, penetration, and method to prevent the penetration of Enterococcus faecalis into root cementum: Confocal laser scanning microscope and scanning electron microscope analysis

Aim:

To ascertain the role of Enterococcus faecalis in persistent infection and a possible method to prevent the penetration of E. faecalis into root cementum.

Methodology:

One hundred and twenty human single-rooted extracted teeth divided into five groups. Group I (control): intact teeth, Group II: no apical treatment done, Group III divided into two subgroups. In Groups IIIa and IIIb, root apex treated with lactic acid of acidic and neutral pH, respectively. Group IV: apical root cementum exposed to lactic acid and roughened to mimic the apical resorption. Group V: apical treatment done same as Group IV and root-end filling done using mineral trioxide aggregate (MTA). Apical one-third of all samples immersed in E. faecalis broth for 8 weeks followed by bone morphogenetic protein and obturation and again immersed into broth for 8 weeks. Teeth split into two halves and observed under confocal laser scanning microscope and scanning electron microscope, organism identified by culture and polymerase chain reaction techniques.

Results:

Adhesion and penetration was observed in Group IIIa and Group IV. Only adhesion in Group II and IIIB and no adhesion and penetration in Group I and V.

Conclusion:

Adhesion and penetration of E. faecalis into root cementum providing a long-term nidus for subsequent infection are the possible reason for persistent infection and root-end filling with MTA prevents the adhesion and penetration.