Streptococci from root canals in teeth with apical periodontitis receiving endodontic treatment

Reverse Vaccinology Approach to Identify Novel and Immunogenic Targets against Streptococcus gordonii

Streptococcus gordonii is a gram-positive, mutualistic bacterium found in the human body. It is found in the oral cavity, upper respiratory tract, and intestines, and presents a serious clinical problem because it can lead to opportunistic infections in individuals with weakened immune systems. Streptococci are the most prevalent inhabitants of oral microbial communities, and are typical oral commensals found in the human oral cavity. These streptococci, along with many other oral microbes, produce multispecies biofilms that can attach to salivary pellicle components and other oral bacteria via adhesin proteins expressed on the cell surface. Antibiotics are effective against this bacterium, but resistance against antibodies is increasing. Therefore, a more effective treatment is needed. Vaccines offer a promising method for preventing this issue. This study generated a multi-epitope vaccine against Streptococcus gordonii by targeting the completely sequenced proteomes of five strains. The vaccine targets are identified using a pangenome and subtractive proteomic approach. In the present study, 13 complete strains out of 91 strains of S. gordonii are selected. The pangenomics results revealed that out of 2835 pan genes, 1225 are core genes. Out of these 1225 core genes, 643 identified as non-homologous proteins by subtractive proteomics. A total of 20 essential proteins are predicted from non-homologous proteins. Among these 20 essential proteins, only five are identified as surface proteins. The vaccine construct is designed based on selected B- and T-cell epitopes of the antigenic proteins with the help of linkers and adjuvants. The designed vaccine is docked against TLR2. The expression of the protein is determined using in silico gene cloning. Findings concluded that Vaccine I with adjuvant shows higher interactions with TLR2, suggesting that the vaccine has the ability to induce a humoral and cell-mediated response to treat and prevent infection; this makes it promising as a vaccine against infectious diseases caused by S. gordonii. Furthermore, validation of the vaccine construct is required by in vitro and in vivo trials to check its actual potency and safety for use to prevent infectious diseases caused by S. gordonii.

Streptococcus gordonii Supragingival Bacterium Oral Infection-Induced Periodontitis and Robust miRNA Expression Kinetics

Streptococcus gordonii (S. gordonii, Sg) is one of the early colonizing, supragingival commensal bacterium normally associated with oral health in human dental plaque. MicroRNAs (miRNAs) play an important role in the inflammation-mediated pathways and are involved in periodontal disease (PD) pathogenesis. PD is a polymicrobial dysbiotic immune-inflammatory disease initiated by microbes in the gingival sulcus/pockets. The objective of this study is to determine the global miRNA expression kinetics in S. gordonii DL1-infected C57BL/6J mice. All mice were randomly divided into four groups (n = 10 mice/group; 5 males and 5 females). Bacterial infection was performed in mice at 8 weeks and 16 weeks, mice were euthanized, and tissues harvested for analysis. We analyzed differentially expressed (DE) miRNAs in the mandibles of S. gordonii-infected mice. Gingival colonization/infection by S. gordonii and alveolar bone resorption (ABR) was confirmed. All the S. gordonii-infected mice at two specific time points showed bacterial colonization (100%) in the gingival surface, and a significant increase in mandible and maxilla ABR (p < 0.0001). miRNA profiling revealed 191 upregulated miRNAs (miR-375, miR-34b-5p) and 22 downregulated miRNAs (miR-133, miR-1224) in the mandibles of S. gordonii-infected mice at the 8-week mark. Conversely, at 16 weeks post-infection, 10 miRNAs (miR-1902, miR-203) were upregulated and 32 miRNAs (miR-1937c, miR-720) were downregulated. Two miRNAs, miR-210 and miR-423-5p, were commonly upregulated, and miR-2135 and miR-145 were commonly downregulated in both 8- and 16-week-infected mice mandibles. Furthermore, we employed five machine learning (ML) algorithms to assess how the number of miRNA copies correlates with S. gordonii infections in mice. In the ML analyses, miR-22 and miR-30c (8-week), miR-720 and miR-339-5p (16-week), and miR-720, miR-22, and miR-339-5p (combined 8- and 16-week) emerged as the most influential miRNAs.

The Hidden World Within: Microbial Dynamics in Root Canal Systems

Several hundred different microbial taxa have made the oral cavity their home because of their evolution in multiple species communities within the special ecosystem. On the other hand, the dental pulp or internal tissue of the tooth is a connective tissue that is physiologically sterile and where any microbial infiltration is a harmful indication. It causes the pulp tissue to become inflamed, which leads to the death of the pulp and diffuses infection with inflammation to the peri-radicular tissues. Comprehending the biology of biofilms, the microbial makeup, and the host's reaction to infections in the pathobiology of root canal infections has received a lot of attention throughout the last few decades. Such comprehensive knowledge is required to design preventive medicines as well as clinically effective treatment regimens. Surprisingly, clinical approaches have concentrated more on radiographically perfecting channel preparation than on debridement of these intricate root canal systems, despite the clear realization that root canal infections are biofilm mediated. Since the present comprehension of the microbial etiopathogenesis of apical periodontitis highlights the significance of focusing on procedures such as "canal cleaning" and chemo-mechanical disinfection, the exclusive purpose of endodontic therapy is mainly missed while discussing "canal shaping." We thoroughly examine the state of our knowledge of the composition and functional traits of the root canal microbiome in this review. We also go into the difficulties with root canal disinfection and the cutting-edge approaches that try to solve these difficulties. In conclusion, we present essential guidance for prospective research areas, underscoring their significance as crucial considerations in the field of frontiers in oral health.

Oral streptococci: modulators of health and disease

Streptococci are primary colonizers of the oral cavity where they are ubiquitously present and an integral part of the commensal oral biofilm microflora. The role oral streptococci play in the interaction with the host is ambivalent. On the one hand, they function as gatekeepers of homeostasis and are a prerequisite for the maintenance of oral health - they shape the oral microbiota, modulate the immune system to enable bacterial survival, and antagonize pathogenic species. On the other hand, also recognized pathogens, such as oral Streptococcus mutans and Streptococcus sobrinus, which trigger the onset of dental caries belong to the genus Streptococcus. In the context of periodontitis, oral streptococci as excellent initial biofilm formers have an accessory function, enabling late biofilm colonizers to inhabit gingival pockets and cause disease. The pathogenic potential of oral streptococci fully unfolds when their dissemination into the bloodstream occurs; streptococcal infection can cause extra-oral diseases, such as infective endocarditis and hemorrhagic stroke. In this review, the taxonomic diversity of oral streptococci, their role and prevalence in the oral cavity and their contribution to oral health and disease will be discussed, focusing on the virulence factors these species employ for interactions at the host interface.

Impact of root canal preparation using two single-file systems on the intra-radicular microbiome of teeth with primary apical periodontitis

OBJECTIVES

This study aimed to describe the effects of two single-file systems on the diversity of the endodontic microbiome of teeth with primary asymptomatic apical periodontitis.

MATERIALS AND METHODS

The root canals from single-rooted teeth with apical periodontitis were prepared using either the Reciproc Blue (RB) or the XP-endo Shaper (XPS) instrument system. The latter was followed by a supplementary step with the XP-endo Finisher (XPF) instrument. For irrigation, 5.25% sodium hypochlorite was used. Root canal samples were taken at the baseline (S1), after preparation (S2), and after the supplementary step (S3). DNA was extracted and subjected to high-throughput sequencing using the MiSeq Illumina platform.

RESULTS

Samples from 10 teeth from the RB and 7 from the XPS group were subjected to DNA sequencing. Initial samples differed significantly from post-preparation samples in bacterial diversity, with no significant difference when comparing the two instrument systems. The most dominant phyla in S2 were Bacteroidetes, Proteobacteria, Firmicutes, Fusobacteria, and Actinobacteria. The same phyla were found to dominate baseline samples and samples taken after using XPF, but with differences in the ranking of the most dominant ones. At the genus level, the most dominant genera identified after RB instrumentation were Bacteroidaceae [G-1], Fusobacterium, and Staphylococcus, while the most dominant genera after XPS instrumentation were Fusobacterium and Porphyromonas. These genera were also dominant in the initial samples.

CONCLUSIONS

Both treatment protocols had measurable effects on the root canal microbial diversity, with no significant differences between them. Most of the dominant taxa involved in the primary infection and probably in the aetiology of apical periodontitis were eliminated or substantially reduced.

CLINICAL RELEVANCE

The most dominant taxa that persisted after instrumentation were Fusobacterium, Porphyromonas, Staphylococcus, and Bacteroidaceae [G-1].

Bacteriologic Conditions of the Apical Root Canal System of Teeth with and without Posttreatment Apical Periodontitis: A Correlative Multianalytical Approach

INTRODUCTION

This study used a correlative multianalytical approach to investigate the bacteriologic conditions in the apical root canal system of treated teeth with or without apical periodontitis and their correlation with the technical quality of the previous root canal obturation and the presence and volume of apical periodontitis lesions.

METHODS

Root apexes were obtained from recently extracted root canal-treated teeth with (n = 23) and without (n = 22) apical periodontitis lesions as demonstrated by cone-beam computed tomographic examination. The root apexes were sectioned and subjected to micro-computed tomographic (micro-CT) scanning. The specimens were cryopulverized, and DNA extracted from the powder was used as a template in real-time polymerase chain reaction assays to quantify total bacteria and members of the Streptococcus genus and Actinobacteria phylum. The bacteriologic findings were compared between the 2 groups and also evaluated for associations with cone-beam computed tomographic and micro-computed tomographic data.

RESULTS

Bacteria were detected in all apical canal samples except 1. The mean counts of total bacteria, streptococci, and actinobacteria did not differ significantly between teeth with or without apical periodontitis (P > .05). Streptococcus levels were significantly lower by 80% in the apical canals of teeth with small lesions compared with those without lesions (P < .05). The limit of filling >2 mm short was significantly associated with more total bacterial counts compared with canals filled 0-2 mm short (P < .05). An adequate coronal restoration was significantly associated with lesser counts of Streptococcus (P < .05).

CONCLUSIONS

Comparable bacterial loads were observed in the apical canal system of treated teeth with and without apical periodontitis, suggesting that factors other than only the total bacterial levels may also influence the development and progression of apical periodontitis. Bacteria were found in the apical canal in virtually all cases with a high prevalence of streptococci and actinobacteria. Streptococci counts were significantly higher in the apical canal of teeth with inadequate restorations and teeth with no lesions. Underfilled canals showed higher bacterial counts.

Lipoteichoic acid of Streptococcus gordonii as a negative regulator of human dendritic cell activation

Streptococcus gordonii, an opportunistic Gram-positive bacterium, causes an infective endocarditis that could be fatal to human health. Dendritic cells (DCs) are known to be involved in disease progression and immune responses in S. gordonii infection. Since lipoteichoic acid (LTA) is a representative virulence factor of S. gordonii, we here investigated its role in the activation of human DCs stimulated with LTA-deficient (ΔltaS) S. gordonii or S. gordonii LTA. DCs were differentiated from human blood-derived monocytes in the presence of GM-CSF and IL-4 for 6 days. DCs treated with heat-killed ΔltaS S. gordonii (ΔltaS HKSG) showed relatively higher binding and phagocytic activities than those treated with heat-killed wild-type S. gordonii (wild-type HKSG). Furthermore, ΔltaS HKSG was superior to wild-type HKSG in inducing phenotypic maturation markers including CD80, CD83, CD86, PD-L1, and PD-L2, antigen-presenting molecule MHC class II, and proinflammatory cytokines such as TNF-α and IL-6. Concomitantly, DCs treated with the ΔltaS HKSG induced better T cell activities, including proliferation and activation marker (CD25) expression, than those treated with the wild-type. LTA, but not lipoproteins, isolated from S. gordonii weakly activated TLR2 and barely affected the expression of phenotypic maturation markers or cytokines in DCs. Collectively, these results demonstrated that LTA is not a major immuno-stimulating agent of S. gordonii but rather it interferes with bacteria-induced DC maturation, suggesting its potential role in immune evasion.

Reactive arthritis and subacute infective endocarditis caused by Streptococcus gordonii infection: A case report

Streptococcus gordonii (S. gordonii) belongs to the alpha-hemolytic Streptococcus group. It is a symbiotic bacterium found in the human oral mucosa which is present in large quantities on the surface of the teeth. It is generally considered nonpathogenic or weakly pathogenic and is known to cause subacute endocarditis; however, there are few reports of reactive arthritis (ReA) caused by S. gordonii. Herein, we report a case of ReA complicated by subacute infective endocarditis caused by S. gordonii and explore the possible pathogenic mechanism of ReA caused by S. gordonii.

Transposon mutagenesis in oral streptococcus

Oral streptococci are gram-positive facultative anaerobic bacteria that are normal inhabitants of the human oral cavity and play an important role in maintaining oral microecological balance and pathogenesis. Transposon mutagenesis is an effective genetic manipulation strategy for studying the function of genomic features. In order to study cariogenic related genes and crucial biological element genes of oral Streptococcus, transposon mutagenesis was widely used to identify functional genes. With the advent of next-generation sequencing (NGS) technology and the development of transposon random mutation library construction methods, transposon insertion sequencing (TIS) came into being. Benefiting from high-throughput advances in NGS, TIS was able to evaluate the fitness contribution and essentiality of genetic features in the bacterial genome. The application of transposon mutagenesis, including TIS, to oral streptococci provided a massive amount of valuable detailed linkage data between genetic fitness and genetic backgrounds, further clarify the processes of colonization, virulence, and persistence and provides a more reliable basis for investigating relationships with host ecology and disease status. This review focuses on transposon mutagenesis, including TIS, and its applicability in oral streptococci.

Microbial identification from traumatized immature permanent teeth with periapical lesions using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

BACKGROUND

This study aims at identifying the microbiota in traumatized immature permanent teeth with periapical lesions using Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

METHODS

The study included 16 immature maxillary central incisors with periapical lesions in 13 patients. Field decontamination and negative control samples were performed before and after access cavity preparation. Root canal samples were taken using sterile stainless-steel hand files following field decontamination. In-office inoculation and pure sub-cultures were performed. Bacterial isolates were prepared for MALDI-TOF MS (Bruker, Billerica, MA USA) analysis using the formic acid extraction method. A comparison of the prevalence of isolated microorganisms was done using a one-sample chi-square test. Comparisons between identified microbial species with the, cone beam computed tomography periapical index (CBCT PAI) scores and lesion volume were also conducted. The Chi-square test was applied to investigate the association between the categorical variables .

RESULTS

Out of the forty isolates recovered from the 16 traumatized teeth included in the present study with the mean patients' age of 10.93 ± 1.77, 37 isolates were reliably identified by MALDI-TOF MS. Twelve teeth (62.5%) were polymicrobial. The recovered bacteria belonged to five phyla, 15 genera and 25 species. Firmicutes were the predominant phylum (P < 0.001) over Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria. Gram positive bacteria were significantly more prevalent than Gram negative (p = 0.03). Facultative anaerobes were the most prevalent (P < 0.001) compared to the obligate anaerobes and the obligate aerobes. The latter were the least prevalent. Statistically, significant differences existed in the comparison between CBCT PAI scores according to bacterial gram staining.

CONCLUSION

Traumatized immature permanent teeth with periapical lesions showed a significant predominance of Gram-positive facultative anaerobes. MALDI-TOF MS provided accurate identification of numerous viable endodontic microbes.

Propionate Attenuates Growth of Oral Streptococci through Enhancing Methionine Biosynthesis

Oral streptococci are considered as an opportunistic pathogen associated with initiation and progression of various oral diseases. However, since the currently-available treatments often accompany adverse effects, alternative strategy is demanded to control streptococci. In the current study, we investigated whether short-chain fatty acids (SCFAs), including sodium acetate (NaA), sodium propionate (NaP), and sodium butyrate (NaB), can inhibit the growth of oral streptococci. Among the tested SCFAs, NaP most potently inhibited the growth of laboratory and clinically isolated strains of Streptococcus gordonii under anaerobic culture conditions. However, the growth inhibitory effect of NaP on six different species of other oral streptococci was different depending on their culture conditions. Metabolic changes such as alteration of methionine biosynthesis can affect bacterial growth. Indeed, NaP enhanced intracellular methionine levels of oral streptococci as well as the mRNA expression level of methionine biosynthesis-related genes. Collectively, these results suggest that NaP has an inhibitory effect on the growth of oral streptococci, which might be due to alteration of methionine biosynthesis. Thus, NaP can be used an effective bacteriostatic agent for the prevention of oral infectious diseases caused by oral streptococci.

Potential of Bouea macrophylla kernel extract as an intracanal medicament against mixed-species bacterial-fungal biofilm. An in vitro and ex vivo study

OBJECTIVE

To investigate the antimicrobial activity of B. macrophylla kernel extract against mixed-species biofilms of E. faecalis, S. gordonii and C. albicans in vitro. To evaluate the efficacy of the extract as an intracanal medicament compared with Ca(OH)₂ and chlorhexidine in ex vivo tooth model.

METHODS

The antibiofilm effect of B. macrophylla kernel extract was determined by AlamarBlue™ assay and the effect on biofilms was visualized by LIVE/DEAD® BacLight™ viability test. Mixed-species biofilms were incubated into the tooth model (N = 42) for 21 days. The teeth were randomly divided into 4 medicament groups for 7 days: (i) normal saline, (ii) calcium hydroxide (Ca(OH)₂), (iii) chlorhexidine gel, (iv) B. macrophylla kernel extract. Dentine samples were collected, qPCR with PMA was used to quantify the viability and species composition of each sample. SEM was used to visualize the effect of medicament on biofilm structure.

RESULTS

The MBIC was 6.25 mg/mL and the MBEC was 50 mg/mL. The integrity of microbial cells was progressively compromised as concentration increased, resulting in greater cell death. Ex vivo tooth model revealed that biofilm treated with 50 mg/mL of the B. macrophylla extract demonstrated a significantly higher proportions of dead cells than in Ca(OH)₂, chlorhexidine and normal saline groups (p < 0.01). Disruption of biofilm structure and enlargement of dentinal tubules was observed in B. macrophylla group on SEM.

CONCLUSION

The extract of B. macrophylla kernel exhibited significant antibiofilm effect against the mixed-species biofilms of E. faecalis, S. gordonii and C. albicans.

Impact of agitation/activation strategies on the antibiofilm potential of sodium hypochlorite/etidronate mixture in vitro

Background

To investigate the effect of a rotary agitation method or ultrasonically activated irrigation on the antibiofilm effect of a mixture of sodium hypochlorite (NaOCl) and etidronate (1-hydroxyethylidene-1,1-bisphosphonate, HEBP) using a dual-species biofilm model in root canal system.

Methods

Mature dual-species biofilms of Enterococcus faecalis and Streptococcus gordonii were formed in root canals of mandibular premolars. Teeth were randomly allotted (n = 12) to group 1, XP-endo Finisher (XPF); group 2, ultrasonically activated irrigation (UAI); group 3, syringe-and-needle irrigation (SNI). In all groups, canals were instrumented with a rotary instrument (XP-endo Shaper) prior to irrigant agitation/activation. A mixture containing 2.5% NaOCl and 9% HEBP was used throughout the experiment. Bacterial counts from the canal were determined using qPCR before preparation (S1), after preparation (S2), and after final irrigation agitation/activation (S3). Bacterial viability within the dentinal tubules in the coronal, middle and apical root-thirds was quantified using confocal microscopy after Live/Dead staining. The bacterial counts and viability were compared between groups using one-way ANOVA and post-hoc Tukey’s tests. Paired t-test was used to compare the bacterial counts within groups.

Results

Instrumentation alone could significantly reduce the microbial counts in all the groups (P < 0.0001). Subsequent agitation/activation resulted in significant microbial reduction only in XPF and UAI (P < 0.05), both of which reduced significantly more microbial counts than SNI (P < 0.05). Live/Dead staining revealed that XPF and UAI showed significantly greater percentage of dead bacteria within the dentinal tubules than SNI in the coronal third (P < 0.05); UAI resulted in the significantly highest percentage of dead bacteria in the middle third (P < 0.05); while there was no significant difference between the groups in the apical third (P > 0.05).

Conclusions

When using the sodium hypochlorite/etidronate mixture for irrigation, final irrigant agitation/activation with XP-endo Finisher or ultrasonic can improve disinfection of the main root canal space and the dentinal tubules in the coronal third, while ultrasonically activated irrigation appears to exhibit better disinfection within dentinal tubules in the middle third.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02222-1.

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.

[Evaluation of the species diversity of microflora isolated from the epithelium of the oral mucosa in patients using removable orthopedic structures based on dental implants]

OBJECTIVE

To assess the species diversity of microorganisms isolated from the oral mucosa in patients with removable orthopedic structures based on dental implants.

MATERIALS AND METHODS

The indicators of the species diversity of microorganisms isolated from the oral mucosa in patients of the main and control groups were studied.

RESULTS

For prosthetic treatment of patients from main group we used a method of manufacturing an overlapping, frame prostheses supported by teeth and dental implants. The results turned out to be reliable for opportunistic microorganisms Streptococcus anginosus and representatives of the orange periodontopathogenic complex Streptococcus constellatus.

CONCLUSION

Microbiological assessment indicates the effectiveness of prosthetic treatment and the use of Corega tablets.

Induction of Apoptotic Cell Death by Oral Streptococci in Human Periodontal Ligament Cells

Initiation and progression of oral infectious diseases are associated with streptococcal species. Bacterial infection induces inflammatory responses together with reactive oxygen species (ROS), often causing cell death and tissue damage in the host. In the present study, we investigated the effects of oral streptococci on cytotoxicity and ROS production in human periodontal ligament (PDL) cells. Streptococcus gordonii showed cell cytotoxicity in a dose- and time-dependent manner. The cytotoxicity might be due to apoptosis since S. gordonii increased annexin V-positive cells, and the cytotoxicity was reduced by an apoptosis inhibitor, Z-VAD-FMK. Other oral streptococci such as Streptococcus mitis, Streptococcus sanguinis, and Streptococcus sobrinus also induced apoptosis, whereas Streptococcus mutans did not. All streptococci tested except S. mutans triggered ROS production in human PDL cells. Interestingly, however, streptococci-induced apoptosis appears to be ROS-independent, as the cell death induced by S. gordonii was not recovered by the ROS inhibitor, resveratrol or n-acetylcysteine. Instead, hydrogen peroxide (H₂O₂) appears to be important for the cytotoxic effects of streptococci since most oral streptococci except S. mutans generated H₂O₂, and the cytotoxicity was dramatically reduced by catalase. Furthermore, streptococcal lipoproteins are involved in cytotoxicity, as we observed that cytotoxicity induced by the lipoprotein-deficient S. gordonii mutant was less potent than that by the wild-type and was attenuated by anti-TLR2-neutralizing antibody. Indeed, lipoproteins purified from S. gordonii alone were sufficient to induce cytotoxicity. Notably, S. gordonii lipoproteins did not induce H₂O₂ or ROS but cooperatively induced cell death when co-treated with H₂O₂. Taken together, these results suggest that most oral streptococci except S. mutans efficiently induce damage to human PDL cells by inducing apoptotic cell death with bacterial H₂O₂ and lipoproteins, which might contribute to the progression of oral infectious diseases such as apical periodontitis.

Assessment of bacterial and dye penetration through post/crown interim restorations while under simulated masticatory load

The aim was to compare two temporary cements to determine which resisted bacterial and dye penetration under temporary posts/cores/crowns subjected to simulated masticatory function. Forty-six single canal human tooth roots were prepared for posts/crowns. A cotton pellet and Cavit were placed in each post space. Temporary posts/cores/crowns were cemented with Intermediate Restorative Material (IRM) (n = 23) or Tempocem (n = 23). Specimens were sterilised, then immersed in a mixture of Streptococcus gordonii and India ink, and subjected to 4 weeks simulated mastication. Dye penetration was assessed by visually inspecting the cotton pellets. Bacterial penetration was determined by placing the pellets into sterile broth and by plating them onto agar plates to confirm S. gordonii growth. There was no statistically significant difference between the cements and the dependent variables of bacterial and dye penetration. Hence, both cements are good options to cement temporary posts/cores/crowns during endodontic treatment of anterior teeth.

Efficacy of double antibiotics in hydroxypropyl methylcellulose for bactericidal activity against Enterococcus faecalis and Streptococcus gordonii in biofilm

OBJECTIVE

This study aimed to investigate the efficacy of double antibiotics, including ciprofloxacin and metronidazole, in a new vehicle, hydroxypropyl methylcellulose (HPMC), against Enterococcus faecalis and Streptococcus gordonii grown in biofilm.

DESIGN

Human mandibular premolars were prepared and divided into four groups: (i) negative control, (ii) positive control, (iii) infected with E. faecalis and S. gordonii for 21 days and intracanally medicated with double antibiotics in HPMC, and (iv) infected with E. faecalis and S. gordonii for 21 days and intracanally medicated with calcium hydroxide (UltraCal™). The efficacy of medication for 14 or 28 days was determined by bacterial cultures and RT-qPCR for absolute quantities of E. faecalis and S. gordonii cDNA and for relative mRNA expressions of pbp5 and gtfG genes.

RESULTS

There were significant decreases in the mean colony forming units and mean cDNA amounts of E. faecalis and S. gordonii in group (iii) on days 14 and 28 compared to those in group (ii) (p < 0.01). However, the mean cDNA amounts of E. faecalis and S. gordonii in group (iv) were found to be significantly increased on day 28 (p < 0.05). The mRNA expression of gtfG was significantly decreased in groups (iii) and (iv) on days 14 and 28, whereas that of pbp5 was significantly increased in group (iv) on days 14 and 28 (p < 0.01).

CONCLUSION

Double antibiotics in HPMC gel showed an in vitro efficacy against E. faecalis and S. gordonii grown in biofilm, suggesting its clinical application as an intracanal medicament for both primary and persistent infections.

Synergistic Effect of Plant Extracts on Endodontic Pathogens Isolated from Teeth with Root Canal Treatment Failure: An In Vitro Study

BACKGROUND AND OBJECTIVES

This study aimed to evaluate the synergistic antimicrobial activity of extracts obtained from Salvadora persica (Miswak), Commiphora molmol (myrrh) and Azadirachta indica (neem) in combination with commercially available antimicrobial agents: penicillin, tetracycline, ofloxacin and fluconazole on endodontic pathogens such as Enterococcus faecalis, Streptococcus mitis,Actinomyces naeslundii and Candida albicans.

MATERIALS AND METHODS

Microbiological samples from the root canals of the teeth undergoing retreatment were taken using sterile paper points kept at full length in the canal for 30 s. The disc diffusion method was used to check the susceptibility of microbes to the plant extracts and antimicrobials by measuring the diameter of the inhibition zones. Against the microbes, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) of the plant extracts were assessed. The fractional inhibitory concentration index (FICI) was used to estimate the synergistic effect of plant extracts combined with antimicrobials against the resistant endodontic microbes.

RESULTS

The findings clearly indicate the effectiveness of all the three plant extracts, Commiphora molmol, Azadirachta indica, Salvadora persica, against all the experimental pathogenic microorganisms except for the ineffectiveness of Azadirachta indica, Salvadora persica against Candidaalbicans. Maximum antimicrobial activity was displayed by Azadirachta indica against Enterococcusfaecalis (MIC = 0.09 ± 1.2 mg/mL, MBC = 0.78 ± 1.25 mg/mL) and the minimum antimicrobial activity was displayed by Commiphora molmol against Actinomyces naeslundii (MIC = 12.5 ± 3.25 mg/mL, MBC = 100 ± 3.75 mg/mL). The best synergy was displayed by Commiphora molmol with fluconazole against Candidaalbicans (FICI = 0.45).

CONCLUSIONS

The current study delineates the variable antimicrobial activity of plant extracts against the experimental endodontic pathogenic microorganisms. Plant extracts in conjunction with various antimicrobials can be valuable aids in combating relatively resistant endodontic microorganisms that have been the cause of worry in recent years, leading to failure even in treatment procedures following all required protocols.

Role of Streptococcus intermedius phosphoglucosamine mutase in bacterial growth, cell morphology, and resistance to polymorphonuclear leukocyte killing

OBJECTIVES

Streptococcus intermedius is a member of the anginosus group of streptococci, an oral commensal bacterium found in infected root canals, and the causative agent of deep-seated abscesses. This organism has slow clearance when phagocytosed within neutrophils. Here, we investigated the role of its phosphoglucosamine mutase (GlmM), an enzyme associated with peptidoglycan synthesis, in bacterial growth, cell morphology, and resistance to polymorphonuclear leukocyte killing.

METHODS

The glmM-deletion (ΔglmM) mutant and the plasmid-borne complementation (ΔglmM/glmM) strain of S. intermedius were generated. The wild type, the ΔglmM mutant, and the ΔglmM/glmM strain were phagocytosed with human polymorphonuclear leukocytes (PMNs), and bacterial viability in PMNs was determined by LIVE/DEAD staining. Additionally, bacterial growth and cell morphology were also compared.

RESULTS

The survival rate of the ΔglmM mutant was significant lower than that of the wild type. Although the difference in the survival rate of the ΔglmM/glmM strain compared to that of the wild type or the ΔglmM mutant was not significant, the rate appeared to be restored to the middle level. Compared to the wild type and the ΔglmM/glmM strain, the ΔglmM mutant showed reduced growth potential, a significant increase in the number of bacterial chains, and heterogeneous bacteria.

CONCLUSIONS

GlmM is one of the factors responsible for the stable resistance of S. intermedius to clearance by PMNs.

Streptococcus gordonii: Pathogenesis and Host Response to Its Cell Wall Components

Streptococcus gordonii, a Gram-positive bacterium, is a commensal bacterium that is commonly found in the skin, oral cavity, and intestine. It is also known as an opportunistic pathogen that can cause local or systemic diseases, such as apical periodontitis and infective endocarditis. S. gordonii, an early colonizer, easily attaches to host tissues, including tooth surfaces and heart valves, forming biofilms. S. gordonii penetrates into root canals and blood streams, subsequently interacting with various host immune and non-immune cells. The cell wall components of S. gordonii, which include lipoteichoic acids, lipoproteins, serine-rich repeat adhesins, peptidoglycans, and cell wall proteins, are recognizable by individual host receptors. They are involved in virulence and immunoregulatory processes causing host inflammatory responses. Therefore, S.gordonii cell wall components act as virulence factors that often progressively develop diseases through overwhelming host responses. This review provides an overview of S. gordonii, and how its cell wall components could contribute to the pathogenesis and development of therapeutic strategies.

Tetracycline and multidrug resistance in the oral microbiota: differences between healthy subjects and patients with periodontitis in Spain

Introduction: Antibiotic resistance is widely found even among bacterial populations not having been exposed to selective pressure by antibiotics, such as tetracycline. In this study we analyzed the tetracycline-resistant subgingival microbiota of healthy subjects and of patients with periodontitis, comparing the prevalence of tet genes and their multidrug resistance profiles.

Methods: Samples from 259 volunteers were analyzed, obtaining 813 tetracycline-resistant isolates. The prevalence of 12 antibiotic resistance genes was assessed, and multidrug profiles were built. Each isolate was identified by 16S rRNA sequencing. Differences in qualitative data and quantitative data were evaluated using the chi-square test and the Mann-Whitney-U test, respectively.

Results: tet(M) was the most frequently detected tet gene (52.03%). We observed significant differences between the prevalence of tet(M), tet(W), tet(O), tet(32) and tet(L) in both populations studied. Multidrug resistance was largely observed, with resistance to kanamycin being the most detected (83.64%). There were significant differences between the populations in the prevalence of kanamycin, chloramphenicol, and cefotaxime resistance. Resistant isolates showed significantly different prevalence between the two studied groups.

Conclusion: The high prevalence of multidrug resistance and tetracycline resistance genes found in the subgingival microbiota, highlights the importance of performing wider and more in-depth analysis of antibiotic resistance in the oral microbiota.

Enhanced biofilm formation of Streptococcus gordonii with lipoprotein deficiency

Streptococcus gordonii is a commensal Gram-positive bacterium that acts as an opportunistic pathogen that can cause apical periodontitis, endocarditis, and pneumonia. Biofilm formation of bacteria is important for the initiation and progression of such diseases. Although lipoproteins play key roles in physiological functions, the role of lipoproteins of S. gordonii in its biofilm formation has not been clearly understood. In this study, we investigated the role of lipoproteins of S. gordonii in the bacterial biofilm formation using its lipoprotein-deficient strain (Δlgt). The S. gordonii Δlgt exhibited increased biofilm formation on the human dentin slices or on the polystyrene surfaces compared to the wild-type strain, while its growth rate did not differ from that of the wild-type. In addition, the S. gordonii Δlgt strain exhibited the enhanced LuxS mRNA expression and AI-2 production, which is known to be a positive regulator of biofilm formation, compared to the wild-type. Concordantly, the augmented biofilm formation of S. gordonii Δlgt was attenuated by an AI-2 inhibitor, D-ribose. In addition, lipoproteins from purified S. gordonii inhibited the biofilm formation of S. gordonii wild-type and Δlgt. Taken together, these results suggest that lipoprotein-deficient S. gordonii form biofilms more effectively than the wild-type strain, which might be related to the AI-2 quorum-sensing system.

Prevalence of the Genus Propionibacterium in Primary and Persistent Endodontic Lesions: A Systematic Review

Propionibacterium are anaerobic/aero-tolerant rod Gram-positive bacteria, and numerous studies are associated with primary and secondary endodontic infections. The data in the literature on the prevalence of Propionibacterium are conflicting, and there are studies that report conflicting data on the prevalence in primary and secondary endodontic infections. This review aims to clarify the prevalence of bacteria of the genus Propionibacterium in endodontic lesions. The present systematic review work was performed on the basis of the Prisma protocol. A search was carried out on the PubMed and Scopus databases with the use of keywords. The research produced 410 records, which, after the elimination of the overlaps and the application of the inclusion and exclusion criteria, led to a number of 36 included articles divided by the three outcomes. The first outcome concerns prevalence of bacteria of the genus Propionibacterium in primary and secondary endodontic lesions. The secondary outcome, differences in the prevalence of bacteria of the genus Propionibacterium between primary endodontic infections and secondary endodontic infections. The tertiary outcome, differences in the prevalence of Propionibacterium Acnes compared to Propionibacterium propionicum in endodontic infections. The results of the meta-analysis show that the genus Propionibacterium bacteria are more prevalent in secondary endodontic infections and that P. Acnes has a higher prevalence than P. propionicum.

Prevalence of Bacteria of Genus Actinomyces in Persistent Extraradicular Lesions-Systematic Review

Actinomyces are anaerobic, rod-shaped, Gram-positive bacteria. They are associated with persistent extraradicular endodontic infections, with possible involvement of the soft tissues of the maxillofacial district. Many studies reported conflicting data on the presence of bacteria of the genus Actinomyces in endodontic infections. The aim of this systematic review of the literature was to determine the real prevalence of such bacteria in primary and/or secondary endodontic infections and in cases of persistence with extraradicular involvement. This systematic review was performed according to the PRISMA protocol. A search was carried out through the Scopus and PubMed databases of potentially eligible articles through the use of appropriate keywords. The literature research resulted in preliminary 2240 records which, after the elimination of overlaps and the application of inclusion and exclusion criteria, led to the inclusion of 46 articles focusing on three outcomes (primary outcome: number of teeth with the presence of a persistent extraradicular infection in which the presence of Actinomyces was ascertained; secondary outcome: number of teeth with endodontic infection in which the presence of Actinomyces was assessed; tertiary outcome: difference in the prevalence of bacteria of the genus Actinomyces between primary endodontic infections and secondary endodontic infections). Results of the meta-analysis show how bacteria of the genus Actinomyces are present in primary and secondary intraradicular infections and in those with persistence with a prevalence (ratio between teeth with actinomyces and teeth with infection) ranging from 0.091 up to 0.130 depending on the subgroups analyzed.

Streptococcus gordonii induces bone resorption by increasing osteoclast differentiation and reducing osteoblast differentiation

Streptococcus gordonii is commonly found in the periapical endodontic lesions of patients with apical periodontitis, a condition characterized by inflammation and periapical bone loss. Since bone metabolism is controlled by osteoclastic bone resorption and osteoblastic bone formation, we investigated the effects of S. gordonii on the differentiation and function of osteoclasts and osteoblasts. For the determination of bone resorption activity in vivo, collagen sheets soaked with heat-killed S. gordonii were implanted on mouse calvaria, and the calvarial bones were scanned by micro-computed tomography. Mouse bone marrow-derived macrophages (BMMs) were stimulated with M-CSF and RANKL for 2 days and then differentiated into osteoclasts in the presence or absence of heat-killed S. gordonii. Tartrate-resistant acid phosphatase staining was performed to determine osteoclast differentiation. Primary osteoblast precursors were differentiated into osteoblasts with ascorbic acid and β-glycerophosphate in the presence or absence of heat-killed S. gordonii. Alkaline phosphatase staining and alizarin red S staining were conducted to determine osteoblast differentiation. Western blotting was performed to examine the expression of transcription factors including c-Fos, NFATc1, and Runx2. Heat-killed S. gordonii induced bone destruction in a mouse calvarial implantation model. The differentiation of RANKL-primed BMMs into osteoclasts was enhanced in the presence of heat-killed S. gordonii. Heat-killed S. gordonii increased the expression of c-Fos and NFATc1, which are essential transcription factors for osteoclast differentiation. On the other hand, heat-killed S. gordonii inhibited osteoblast differentiation and reduced the expression of Runx2, an essential transcription factor for osteoblast differentiation. S. gordonii exerts bone resorptive activity by increasing osteoclast differentiation and reducing osteoblast differentiation, which may be involved in periapical bone resorption.

Serine-rich Repeat Adhesin Gordonii Surface Protein B is Important for Streptococcus gordonii Biofilm Formation

INTRODUCTION

Streptococcus gordonii is a predominant member of the oral microflora and has been isolated from root canals of teeth with refractory apical periodontitis. Biofilm formation is important for various dental diseases, and S. gordonii is involved in dental biofilm formation as an early colonizer. Although serine-rich repeat (SRR) adhesins of S. gordonii such as gordonii surface protein B (GspB) are associated with bacterial colonization, the role of GspB in biofilm formation is not clearly understood. In the present study, we investigated the effect of S. gordonii GspB on biofilm formation using wild-type and GspB-deficient mutant S. gordonii strains.

METHODS

Confocal microscopy and crystal violet assay were used to determine biofilm formation. Bacterial growth was examined by measuring optical density with spectrometry. Bacterial adherence and biofilm on the culture plate and human dentin slices were visualized with a scanning electron microscope.

RESULTS

The GspB-deficient S. gordonii mutant strain was less potent than the wild-type strain in biofilm formation. Of note, there was no difference in the bacterial growth rate between the mutant and wild-type strains. Differences in biofilm-forming ability between the wild-type and mutant strains were more distinct in the sucrose-supplemented media. Furthermore, the GspB-deficient mutant exhibited attenuated formation of aggregates on the surface of the culture plate and human dentin slices.

CONCLUSIONS

These results suggest that GspB is important for S. gordonii biofilm formation, which may contribute to the development of dental biofilm-associated diseases.

Assessment of Correlation between Clinical Parameters and Pulp Canal Pathogens in Endodontic Pathologies: A Microbiological Study

INTRODUCTION

Success and failure of root canal therapy is largely dependent on the clinician and the patient. Once the tooth is restored into its functional and esthetic place, the root canal therapy is considered to be complete. It is a well-known fact that root canal space acts as a rich reservoir for microorganisms. Past studies show that root canal harbors an array of different microorganisms. Streptococcus mitis and Enterococcus faecalis have been found to be the most prevalent microorganisms isolated from the infected pulp canal space. Hence, we evaluated the association of endodontic signs and symptoms with root canal pathogens.

MATERIALS AND METHODS

A total of 120 patients were selected for the study and divided broadly into two groups: Group I containing patients with primary infection and group II containing patients in which retreatment was required. Both groups contained 60 patients each. Clinical parameters recorded for the study are pain, tenderness on percussion, swelling, periapical radiolucency on radiographic analysis, caries, sinus formation, and tooth mobility. After assessment, opening, and initial filing, sterile paper points were inserted into the root canal space for collection of microbiological sample, which was further send to laboratory for cultural analysis. All the results were analyzed by Statistical Package for the Social Sciences (SPSS) software. Student's t-test and Fisher's exact test were used to evaluate the level of significance.

RESULTS

While comparing the mean age of the patients in the two groups, no significant association was seen. Statistically significant results were obtained while comparing the association between pain and S. mitis. Positive correlation was seen on comparing the association between tenderness on percussion and E. faecalis. Also, a positive association was seen between periapical radiolucency and S. mitis.

CONCLUSION

Strong positive correlation exists between S. mitis and E. faecalis and endodontic signs and symptoms.

CLINICAL SIGNIFICANCE

Sound knowledge regarding the association of microbes of root canal and specific endodontic signs and symptoms could help therapeutic management of root canal infections effectively.

Antibacterial Activity of MTA Fillapex and AH 26 Root Canal Sealers at Different Time Intervals

Introduction:

The main goal of endodontic treatment is elimination of bacteria and their by-products from infected root canals. This study compared the antibacterial effect of two different sealers, AH 26 and MTA Fillapex, on 4 microorganisms 24, 48 and 72 h and 7 days after mixing.

Methods and Materials:

The microorganisms used in this study consisted of Lactobacillus acidophilus (ATCC 4356), Lactobacillus casei (ATCC 39392), Staphylococcus aureus (ATCC 25923) and Enterococcus faecalis (ATCC 29212). This test is based on the growth of bacteria and turbidity measurement technique using a spectrophotometer, and direct contact was conducted. Multiple comparisons were carried out using repeated-measures ANOVA followed by Tukey’s test and student’s t-test. The level of significance was set at 0.05.

Results:

The antibacterial activity in the indirect technique was more than the technique with both sealers. In the direct technique the antibacterial activity on all microorganisms were lower for MTA Fillapex sealer. In the indirect technique, both sealers exhibited similar antibacterial properties.

Conclusion:

The antibacterial effect of MTA Fillapex sealer was significantly less than that of AH 26 sealer in the direct technique. The antibacterial effects of both sealers were similar in the indirect technique.

Infection Control in Retreatment Cases: In Vivo Antibacterial Effects of 2 Instrumentation Systems

INTRODUCTION

This in vivo study compared the antibacterial effects of 2 instrumentation systems in root canal-treated teeth with apical periodontitis.

METHODS

Forty-eight teeth with a single root and a single canal showing post-treatment apical periodontitis were selected for this study. For retreatment, teeth were randomly divided into 2 groups according to the instrumentation system used: Self-Adjusting File (SAF; ReDent-Nova, Ra'anana, Israel) and Twisted File Adaptive (TFA; SybronEndo, Orange, CA). In both groups, 2.5% sodium hypochlorite was the irrigant. Bacteriological samples were taken before (S1) and after chemomechanical preparation (S2). In the TFA group, passive ultrasonic irrigation (PUI) was performed after instrumentation, and samples were also taken after this supplementary step (S2b). DNA was extracted from the clinical samples and subjected to quantitative real-time polymerase chain reaction to evaluate the levels of total bacteria, streptococci, and Enterococcus faecalis. Statistical analyses from quantitative real-time polymerase chain reaction data were performed within groups using the Wilcoxon matched pairs test and between groups using the Mann-Whitney U test and the Fisher exact test with the significance level set at P < .05.

RESULTS

Bacteria were detected in S1 samples from 43 teeth, which were then included in the antibacterial experiment. Both SAF and TFA instrumentation protocols showed a highly significant intracanal bacterial reduction (P < .001). Intergroup quantitative comparisons disclosed no significant differences between TFA with or without PUI and SAF (P > .05). PUI did not result in significant improvement in disinfection (P > .05).

CONCLUSIONS

Both instrumentation systems/treatment protocols were highly effective in significantly reducing the intracanal bacterial counts. No significant difference was observed between the 2 systems in disinfecting the canals of teeth with post-treatment apical periodontitis.

Short-chain Fatty Acids in Infected Root Canals of Teeth with Apical Periodontitis before and after Treatment

INTRODUCTION

Short-chain fatty acids (SCFAs) are bacterial metabolic end products that may function as virulence factors. This study evaluated the occurrence of SCFAs in infected root canals before and after treatment.

METHODS

Samples were taken from root canals of teeth with apical periodontitis before (S1) and after (S2) chemomechanical preparation with either NaOCl or chlorhexidine as the irrigant and then after interappointment medication with calcium hydroxide (S3). High-performance liquid chromatography was used for detection of SCFAs. Selected bacterial taxa that are recognized producers of the target SCFAs were identified by real-time polymerase chain reaction.

RESULTS

Butyric acid was the most common fatty acid in S1, followed by propionic acid. Both molecules were also found in S2 and S3 from both NaOCl and chlorhexidine groups. Lactic acid was not present in detectable levels in S1, but it occurred in 1 postinstrumentation sample and in 9 samples taken after calcium hydroxide medication. Of the target taxa, Fusobacterium nucleatum was the most prevalent in S1 (76%), followed by members of the Actinobacteria phylum (71%), Streptococcus species (59%), and Parvimonas micra (53%). Gram-positive taxa, especially streptococci, were the most prevalent bacteria in S2 and S3. SCFA detection was matched with the respective potential producer species in most cases.

CONCLUSIONS

This first report of SCFAs in infected root canals suggests that these molecules may play a role in the pathogenesis of apical periodontitis. Significance of persistence of SCFAs after treatment and its effects on the long-term outcome await elucidation.

Streptococcus gordonii collagen-binding domain protein CbdA may enhance bacterial survival in instrumented root canals ex vivo

INTRODUCTION

The surface-associated collagen-binding protein Ace of Enterococcus faecalis has been implicated as a virulence factor that contributes to bacterial persistence in endodontic infections. The purpose of this study was to determine if proteins with amino acid sequence similarity to Ace found in more abundant oral streptococci could play a similar role in potentially enhancing endodontic infections.

METHODS

A Streptococcus gordonii gene similar to ace was identified by genome sequence searches in silico. An isogenic derivative of strain DL1 with a disruption in the identified gene was constructed by allelic replacement. Parent and mutant strains were characterized for their ability to bind immobilized collagen type 1 in a microtiter plate-binding assay. Survival of the strains in a human tooth ex vivo-instrumented root canal model was compared by inoculating canals with parental or mutant bacteria and determining the colony-forming units (CFUs) recovered at various time points over a 12-day period.

RESULTS

The S. gordonii gene, encoding a protein with a conserved collagen-binding domain similar to that of Ace, was designated cbdA. The cbdA-deficient cells were less able to bind collagen type 1 than parental cells (P < .0001). Genetic complementation of the cbdA-deficient strain restored the collagen-binding phenotype. By day 12, significantly fewer (P = .03) cbdA-deficient than parental CFUs were recovered from instrumented canals.

CONCLUSIONS

A gene encoding a putative collagen-binding protein was identified in S. gordonii. Fewer S. gordonii cbdA-deficient cells survived ex vivo compared with parental cells, suggesting that collagen-binding proteins may contribute to the persistence of oral streptococci in instrumented root canals.

Characterization of microbiota of root canal-treated teeth with posttreatment disease

This study evaluated the microbiota of root canals undergoing retreatment. The most prevalent taxa detected by checkerboard included Propionibacterium species, Fusobacterium nucleatum, streptococci, and Pseudoramibacter alactolyticus. Quantitative real-time PCR detected Enterococcus faecalis and streptococci in 38% and 41% of the cases, comprising 9.76% and 65.78% of the total bacterial counts, respectively. The findings call into question the status of E. faecalis as the main pathogen and suggest that other species can be candidate pathogens associated with persistent/secondary endodontic infections.

Photoactivated disinfection of Streptococcus intermedius through dentin disc at clinically relevant intervals: an in vitro study

In this present study we have tested the impact of porfimer sodium (Photofrin, AXCAN PHARMA Inc., Quebec, Canada) photoactivated disinfection (PD) on cells of Streptococcus intermedius in suspension. In order to provide basic data to support future clinical studies of PD in dentistry the study used exposure to Quartz-tungsten-halogen (QTH) dental curing light for clinically relevant time periods to activate Photofrin and measured its effectiveness under a variety of conditions including activation through dentin hard tissue. S. intermedius was grown in planktonic suspension for 48h. Nine groups were formed: three control groups (1-3) and six experimental groups (4-9). Groups 4-6 tested the use of Photofrin treatment combined with QTH light at various intervals of irradiation (5, 15 and 60s). Groups 7-9 were similar to groups 4-6 with the exception that irradiation commenced through a dentin disc. Following treatment, bacteria were plated. Colony counts were measured following 72h incubation at 37 degrees C. Statistical analysis was carried out by one-way ANOVA at a 95% confidence level. A significant reduction in S. intermedius colony counts was observed for all experimental groups and one control group. The reduction in numbers of colonies in the experimental groups varied from 79.28 to 99.40% with an average of 94.61%. Reduction in viable bacterial cells indicated a strong relationship between power density and irradiation interval. When curing light energy density was lower due to the irradiation through the 1mm dentin disc, prolonged irradiation interval enhanced bacterial kill. In conclusion, where direct irradiation is not possible for PD treatment, irradiation through dentin may still be done successfully within a clinically relevant interval.

Bacterial and dye penetration through interim restorations used during endodontic treatment of molar teeth

INTRODUCTION

The purpose of this study was to investigate the association between dye and bacterial penetration through interim restorations used during endodontic treatment.

METHODS

Sixty-four extracted human teeth were used, with 2 teeth each as positive and negative controls. Endodontic access with a mesio-occluso-distal cavity was prepared. Palatal cusps of maxillary molars and buccal cusps of mandibular molars were removed. Cotton was placed over the canals and covered with Cavit. Thirty teeth were restored with Ketac Silver (KS) and 30 with KS reinforced with a stainless steel band (KSSB). Samples were submersed in India ink mixed with brain heart infusion broth containing Streptococcus gordonii. After 3 months of simulated chewing, structural integrity and dye and bacterial penetration were assessed.

RESULTS

Positive controls had both dye and bacterial penetration. Negative controls had no dye or bacterial penetration. All KS restorations debonded, whereas 18 KSSB restorations (60%) debonded. KS restorations were 1.67 times more likely to debond than KSSB restorations (Fisher exact test). KS was 1.3 times more likely to have dye penetration than KSSB (Fisher exact test) and 3 times more likely to have bacterial penetration, although not statistically significant (chi(2) test). Overall, 88.3% of specimens had dye penetration, and 20% had bacterial penetration. This 68.3% difference indicated no association between dye and bacterial penetration (exact McNemar test).

CONCLUSIONS

Stainless steel bands helped maintain structural integrity of KS restorations under masticatory function. Bands helped prevent dye penetration but not bacterial penetration. There was no association between dye and bacterial penetration.

Identification of selected respiratory pathogens in endodontic infections

OBJECTIVE

To determine whether endodontic infections could harbor common etiologic agents of respiratory infections such as Streptococcus pneumoniae and Chlamydia pneumoniae.

STUDY DESIGN

Specimens were aseptically obtained from 40 patients with endodontic infections. For the detection of C. pneumoniae, single-step 16S rRNA-based polymerase chain reaction (PCR) and nested PCR targeting aromatic amino acid hydroxylase were used. For the identification of S. pneumoniae, primers targeting 16S rRNA gene and autolysin (lytA) were used.

RESULTS

Of 21 patient samples tested with the 16S rRNA-based PCR for S. pneumoniae, positive amplification was observed in all except 3 specimens. However, sequencing and phylogenetic analysis revealed that the product belonged to other bacterial phylotypes. The lytA-based PCR for S. pneumoniae and both PCR assays for C. pneumoniae failed to detect these organisms in all of the specimens tested.

CONCLUSIONS

Streptococcus pneumoniae and C. pneumoniae were not present in endodontic infections. PCR primers with less stringent specificity will inaccurately identify respiratory pathogens.

Plasminogen binding by oral streptococci from dental plaque and inflammatory lesions

Plasminogen binding by bacteria is a virulence factor important for the entry and dissemination of bacteria in the body. A wide variety of bacteria bind plasminogen, including both organisms causing disease and components of the normal oral flora. The purpose of this study was to examine the characteristics of plasminogen binding by six clinical isolates of oral streptococci from both dental plaque and inflammatory lesions. All the strains bound plasminogen with approximately the same affinity, and binding was specific and lysine-dependent as evidenced by its inhibition by epsilon-aminocaproic acid. All of the test strains were capable of activating bound plasminogen to plasmin without the addition of a plasminogen activator, and subsequent analysis revealed the presence of streptokinase in all strains. However, the streptococci exhibited fibrinolytic activity only in the presence of plasminogen and this could be inhibited by the addition of epsilon-aminocaproic acid. SDS-PAGE and 2D gel electrophoresis coupled with plasminogen ligand blotting showed that only a subset of the total proteins (2-15) were involved in the binding of plasminogen. Partial identification of the binding proteins revealed that four glycolytic enzymes, enolase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate mutase, were predominant in binding plasminogen. The binding of plasminogen by bacteria from pus did not differ from that of the strains from supragingival plaque. The findings illustrate how apparently innocuous commensal bacteria are capable of utilizing a mechanism that is generally regarded as being of importance to pathogenicity and suggest an additional role of plasminogen binding.

The Antimicrobial Effect of Silver Ion Impregnation into Endodontic Sealer against Streptococcus mutans

Pulpal and periradicular diseases are primarily caused by bacterial invasion of the root canal system as a result of caries progression. The presence of residual bacteria at the time of root canal completion (obturation) is associated with significantly higher rate of treatment failure. Re-infection of obturated root canals can be potentially prevented by enhancing the antibacterial activities of root canal obturation materials. We evaluated, in an in vitro model, the antimicrobial efficacy of silver ions added to a common endodontic sealer. For that purpose we performed growth inhibition studies and bacterial viability tests. We measured the zone of inhibition, optical density and performed confocal laser scanning microscopy. Our results show that the silver ions enhance the antimicrobial activity of the root canal sealer against Streptococcus mutans. This study approach may hold promise for studying other biologically based therapies and therefore increasing the success rate of routine orthograde root canal treatment.