Changes in root canal microbiota during the development of rat periapical lesions

Molecular analyses indicate profuse bacterial diversity in primary and post- treatment endodontic infections within a cohort from the United Arab Emirates-A preliminary study

OBJECTIVE

Endodontic microbiota appears to undergo evolutionary changes during disease progression from inflammation to necrosis and post-treatment. The aim of this study was to compare microbiome composition and diversity in primary and post-treatment endodontic infections from a cohort of patients from the UAE.

DESIGN

Intracanal samples were collected from primarily infected (n = 10) and post-treatment infected (n = 10) root canals of human teeth using sterile paper points. Bacterial DNA was amplified from seven hypervariable regions (V2-V4 and V6-V9) of the 16S rRNA gene, then sequenced using next-generation sequencing technology. The data was analyzed using appropriate bioinformatic tools.

RESULTS

Analyses of all the samples revealed eight major bacterial phyla, 112 genera and 260 species. Firmicutes was the most representative phylum in both groups and was significantly more abundant in the post-treatment (54.4%) than in primary (32.2%) infections (p>0.05). A total of 260 operational taxonomic units (OTUs) were identified, of which 126 (48.5%) were shared between the groups, while 83 (31.9%) and 51 (19.6%) disparate species were isolated from primary and post-treatment infections, respectively. A significant difference in beta, but not alpha diversity was noted using several different indices (p< 0.05). Differential abundance analysis indicated that, Prevotella maculosa, Streptococcus constellatus, Novosphigobium sediminicola and Anaerococcus octavius were more abundant in primary infections while Enterrococcus faecalis, Bifidobacterium dentium, Olsenella profusa and Actinomyces dentalis were more abundant in post-treatment infections (p <0.05).

CONCLUSION

Significant differences in the microbiome composition and diversity in primary and post-treatment endodontic infections were noted in our UAE cohort. Such compositional differences of microbiota at various stages of infection could be due to both intrinsic and extrinsic factors impacting the root canal ecosystem during disease progression, as well as during their therapeutic management. Identification of the key microbiota in primarily and secondarily infected root canals can guide in the management of these infections.

Effectiveness of probiotics in apical periodontitis progression: A scoping review and implications for research

To synthesise the current knowledge on the effects of probiotics in apical periodontitis progression by a scoping review of animal and human studies. Reporting was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. The literature search and screening was performed on PubMed and Scopus databases by two independent reviewers selecting human and animal studies that evaluated the effectiveness of probiotics in reducing the severity of apical periodontitis. Two animal studies with 3 publications met the eligibility criteria for qualitative synthesis. The most common probiotics were Lactobacillus rhamnosus and Lactobacillus acidophilus orally administered for gavage in Wistar rats with induced apical periodontitis. Overall, probiotics significantly reduced inflammation and bone resorption with an improvement in the apical periodontitis progression. Although results in animal studies are promising, the use of probiotics in apical periodontitis progression requires caution due to the insufficient available evidence.

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.

Oral Osteomicrobiology: The Role of Oral Microbiota in Alveolar Bone Homeostasis

Osteomicrobiology is a new research field in which the aim is to explore the role of microbiota in bone homeostasis. The alveolar bone is that part of the maxilla and mandible that supports the teeth. It is now evident that naturally occurring alveolar bone loss is considerably stunted in germ-free mice compared with specific-pathogen-free mice. Recently, the roles of oral microbiota in modulating host defense systems and alveolar bone homeostasis have attracted increasing attention. Moreover, the mechanistic understanding of oral microbiota in mediating alveolar bone remodeling processes is undergoing rapid progress due to the advancement in technology. In this review, to provide insight into the role of oral microbiota in alveolar bone homeostasis, we introduced the term “oral osteomicrobiology.” We discussed regulation of alveolar bone development and bone loss by oral microbiota under physiological and pathological conditions. We also focused on the signaling pathways involved in oral osteomicrobiology and discussed the bridging role of osteoimmunity and influencing factors in this process. Finally, the critical techniques for osteomicrobiological investigations were introduced.

Periapical lesions in two inbred strains of rats differing in immunological reactivity

AIM

To investigate the influence of strain differences in immune responses on the pathogenesis of experimental periapical lesions in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

METHODOLOGY

Periapical lesions were induced in male DA and AO rats by pulp exposure of the first mandibular right molars to the oral environment. Animals were killed 21 days after pulp exposure. The mandibular jaws were retrieved and prepared for radiographic, pathohistological, immunohistochemical analysis, real-time PCR and flow cytometry. Blood samples and the supernatant of periapical lesions were collected for measurement of cytokines and oxidative stress marker levels. Statistical analysis was performed using the Kruskal-Wallis H and Mann-Whitney U non-parametric tests or parametric One-Way anova and Independent Samples T-test to determine the differences between groups depending on the normality of the data. A significant difference was considered when p values were <.05.

RESULTS

DA rats developed significantly larger (p < .05) periapical lesions compared to AO rats as confirmed by radiographic and pathohistological analysis. The immunohistochemical staining intensity for CD3 was significantly greater in periapical lesions of DA rats compared to AO rats (p < .05). In DA rats, periapical lesions had a significantly higher (p < .05) percentage of CD3+ cells compared to AO rats. Also, the percentage of INF-γ, IL-17 and IL-10 CD3+CD4+ cells was significantly higher in DA rats (p < .05). DA rats had a significantly higher Th17/Th10 ratio. RT-PCR expression of IL-1β, INF-γ and IL-17 genes was significantly higher in periapical lesions of DA compared to AO rats (p < .05). The receptor activator of nuclear factor kappa-Β ligand/osteoprotegerin ratio was higher in DA compared to AO rats with periapical lesions (p < .05). Systemic levels of TNF-α and IL-6 were significantly higher in DA compared to AO rats (p < .05). Levels of lipid peroxidation measured as thiobarbituric acid reactive substances and reduced glutathione were significantly higher (p < .05) in the supernatant in the periapical lesions of DA rats.

CONCLUSION

After pulp exposure, DA rats developed much larger periapical lesions compared to AO rats. Genetically determined differences in immunopathology have been demonstrated to be a significant element defining the severity of periapical lesions.

Exploiting dentine matrix proteins in cell-free approaches for periradicular tissue engineering

The recent discovery of mesenchymal stem cells within periapical lesions (PL-MSC) has presented novel opportunities for managing periradicular diseases in adult teeth by way of enhancing tissue regeneration. This discovery coincides with the current paradigm shift toward biologically driven treatment strategies in endodontics, which have typically been reserved for non-vital immature permanent teeth. One such approach that shows promise is utilizing local endogenous non-collagenous dentine extracellular matrix components (dECM) to recruit and upregulate the intrinsic regenerative capacity of PL-MSCs in situ. At picogram levels, these morphogens have demonstrated tremendous ability to enhance the cellular activities in in vitro and in vivo animal studies that would otherwise be necessary for periradicular regeneration. Briefly, these include proliferation, viability, migration, differentiation, and mineralization. Therefore, topical application of dECMs during ortho- or retrograde root canal treatment could potentially enhance and sustain the regenerative mechanisms within diseased periapical tissues that are responsible for attaining favorable clinical and radiographic outcomes. This would provide many advantages when compared with conventional antimicrobial-only therapies for apical periodontitis (AP), which do not directly stimulate healing and have had stagnant success rates over the past five decades despite significant advances in operative techniques. The aim of this narrative review was to present the novel concept of exploiting endogenous dECMs as clinical tools for treating AP in mature permanent teeth. A large scope of literature was summarized to discuss the issues associated with conventional treatment modalities; current knowledge surrounding PL-MSCs; composition of the dECM; inductive potentials of dECM morphogens in other odontogenic stem cell niches; how treatment protocols can be adapted to take advantage of dECMs and PL-MSCs; and finally, the challenges currently impeding successful clinical translation alongside directions for future research.

Excessive caffeine intake increases bone resorption associated with periapical periodontitis in rats

AIM

To evaluate the effect of excessive caffeine intake on the inflammation/resorption processes associated with periapical periodontitis (PP) in rats.

METHODOLOGY

Sixteen Wistar rats were used. Periapical periodontitis was induced in the four first molars in each animal. The animals were arranged into two groups: control (C)-rats with periapical periodontitis; and caffeine (CAF)-rats with periapical periodontitis under caffeine administration protocol. The CAF animals received 10 mg/100 g of body weight/day of caffeine via gavage starting fifteen days before PP induction and continuing for thirty more days until euthanasia. On the 30th day, the animals were euthanized and the jaws removed for microcomputed tomography, histological and immunohistochemical analysis for RANKL, OPG, TRAP, IL-10, TNF-⍺ and IL-1β. The Mann-Whitney test was performed for nonparametric data, and Student's t test was performed for parametric data, using p < .05.

RESULTS

There was no significant difference in the weight change between the groups. The median score of the inflammatory process was significantly greater in the CAF group (3) compared with the C group (2), p = .0256. Bone resorption was greater in the group consuming caffeine (1.08 ± 0.15 mm³ ) compared with the C group (0.88 ± 0.10 mm³ ), p = .0346. The immunolabelling for RANKL, TRAP and IL-1β was significantly higher in the CAF group when compared to the control, p < .05. No differences were found for the OPG, IL-10 and TNF-⍺ immunolabelling.

CONCLUSION

Excessive caffeine exposure via gavage in rats was able to exacerbate the volume of periapical bone destruction, and the inflammatory pattern deriving from periapical periodontitis altering the expression of RANKL, IL-1β and TRAP.

Enterococcus faecalis sustained infection induces macrophage pro-resolution polarization

AIM

To investigate macrophage function in the presence of sustained infection with Enterococcus faecalis, a prevalent root canal resident in asymptomatic apical periodontitis.

METHODOLOGY

The human monocyte cell line (THP-1) was differentiated into macrophages by exposure to phorbol myristate acetate (PMA), and the cultures were inoculated with E. faecalis for up to 48 h. At three time-points 90 min, 24 and 48 h after inoculation, the macrophages and their supernatants were examined. Assays included macrophage phagocytosis rate and vitality, bacterial survival, reactive oxygen species (ROS) production, mitochondrial activity, cytokine production and the expression of pro/anti-inflammatory M1/M2 markers. Also, periapical tissue from apicectomy samples of human endodontically treated teeth were collected for histological and immunofluorescent analysis. Statistical differences were analysed with RM ANOVA.

RESULTS

E. faecalis were phagocytized, and subsequently, most of the macrophages underwent apoptosis and necrosis. The small population of macrophages that remained vital after 48 h post-inoculation harboured surviving bacteria. Despite a reduction in the number of macrophages over time, the mitochondrial activity of the surviving macrophages remained constant and external ROS decreased, whereas internal ROS increased. During the infection, a shift to a M2 macrophage population at 48 h post-infection was observed; the results were similar to those obtained in periapical human tissue biopsies (p < .05).

CONCLUSIONS

The study portrays a continuous non-resolved infection with E. faecalis and activation of macrophages that are polarized to the M2 pro-resolution phenotype.

A Case of Dialister pneumosintes Bacteremia-Associated Neck and Mediastinal Abscess

BACKGROUND Dialister pneumosintes is a suspected periodontal pathogen. It can affect different parts of the body either by hematogenous transmission or regional spread. Here, we report a case of 30-year-old previously healthy woman diagnosed with mediastinal and neck abscess caused by this pathogen. CASE REPORT A 30-year-old woman presented with a 1-day history of fever, vomiting, and diarrhea. She was on her last dose of a 2-week course of oral antibiotic for suspected dental abscess. On admission, parenteral broad-spectrum antibiotic was started for sepsis of unknown source. Because of intermittent spike of high temperature despite being on an antibiotic, cross-sectional imaging was performed, which revealed a superior mediastinal abscess with extension in the neck. She was referred to the ENT surgeon for incision and drainage of the collection. However, the procedure was complicated by injury to the right internal jugular vein. Her postoperative period was also convoluted with the development of pulmonary embolism, followed by deep vein thrombosis of the right upper limb. Her pus polymerase chain reaction test detected 16s rRNA gene, suggestive of gram-negative anaerobic bacilli, and anaerobic blood culture grew Dialister pneumosintes. After a prolonged course of illness and antibiotic treatment, she recovered well, and now is back to her normal activities. CONCLUSIONS Potential life-threatening complications may develop from periodontal infection by this microorganism. In patients being treated for sepsis of unknown origin, not responding to antibiotic treatment, and with a history of recent periodontal infection, a deep-seated abscess needs to be considered.

Dietary supplementation with multi-strain formula of probiotics modulates inflammatory and immunological markers in apical periodontitis

Objective

The aim of this study was to evaluate whether probiotics multi-strain formula affects the development of apical periodontitis (AP) induced in rats.

Methodology

16 Wistar rats were divided in two groups (n=8): rats with AP fed with regular diet (Control-C (CG)); rats with AP, fed with regular diet and supplemented with multi-strain formula (one billion colony-forming units (CFU)): GNC Probiotic Complex (PCG) ( Lactobacillus acidophilus, Lactobacillus salivaris, Lactobacillus plantarum, Lactobacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium animalis subs. lactis and Streptococcus thermofilus ). AP was induced in the upper and lower first molars by dental pulp exposure to the oral environment. PCG was administered orally through gavage for 30 days during the AP development. After this period the animals were euthanized and the mandibles were removed and processed for histologic analysis, and immunochemical assays for interleukin (IL)-6, IL-10, IL-1β, RANKL, OPG, and TRAP. The Mann–Whitney U test and Student’s t test were performed (P<.05).

Results

The CG showed more intense inflammatory infiltrate than the PCG group (P<.05). IL-1β, IL 6 and RANKL decreased in the PCG group compared with CG (P<.05). The IL-10 level increased in the PCG group (P<.05). The OPG level was similar in both groups (P>.05). The number of mature osteoclasts (TRAP-positive multinucleated cells) was lower in PCG group when compared to the CG (P<.05).

Conclusion

Probiotic Complex modulates inflammation and bone resorption in apical periodontitis.

Metaproteome and metabolome of oral microbial communities

The emergence of high-throughput technologies for the comprehensive measurement of biomolecules, also referred to as "omics" technologies, has helped us gather "big data" and characterize microbial communities. In this article, we focus on metaproteomic and metabolomic approaches that support hypothesis-driven investigations on various oral biologic samples. Proteomics reveals the working units of the oral milieu and metabolomics unveils the reactions taking place; and so these complementary techniques can unravel the functionality and underlying regulatory processes within various oral microbial communities. Current knowledge of the proteomic interplay and metabolic interactions of microorganisms within oral biofilm and salivary microbiome communities is presented and discussed, from both clinical and basic research perspectives. Communities indicative of, or from, health, caries, periodontal diseases, and endodontic lesions are represented. Challenges, future prospects, and examples of best practice are given.

Reduced bone resorption and inflammation in apical periodontitis evoked by dietary supplementation with probiotics in rats

AIM

To evaluate the relationship between systemic administration of probiotics and inflammation/resorption processes associated with apical periodontitis (AP) in a rat model.

METHODOLOGY

Twenty-four male Wistar rats were used. AP was induced in the mandibular left/right first molars. The animals were arranged into three groups: Control, Lactobacillus rhamnosus and L. acidophilus. Probiotics were orally administered via gavage (10⁹ colony-forming units (CFU) diluted in 5 mL of water) for 30 days during the development of AP. On the 30th day, blood was collected to analyse the calcium, phosphorus and alkaline phosphatase concentrations in plasma. Then, the animals were euthanized and the jaws removed for micro-computed tomography and immune-histopathological analysis for receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG) and tartrate-resistant acid phosphatase (TRAP). After the Shapiro-Wilk test of normality, the Kruskal-Wallis followed by Dunn's test was performed for nonparametric data, and analysis of variance followed by the Tukey test was performed for parametric data (P < 0.05).

RESULTS

There was no significant difference in the calcium and phosphorus levels in plasma amongst the groups (P > 0.05). The level of alkaline phosphatase was significantly higher in the groups that consumed probiotics (P < 0.05). A significantly lower volume of bone resorption was observed in groups that consumed probiotics (P < 0.05). The inflammatory infiltrates and the immunolabelling for RANKL and TRAP were significantly lower in probiotic groups when compared to the control (P < 0.05). Also, the OPG was significantly more immunolabelled in the L. acidophilus group than in the L. rhamnosus and control groups (P < 0.05).

CONCLUSION

Probiotic supplementation through gavage (L. rhamnosus and L. acidophilus) had a significant effect on the reduction of inflammation and bone resorption in apical periodontitis development in rats.

Systemic administration of probiotics reduces the severity of apical periodontitis

AIM

To evaluate the effect of systemic administration of probiotics on the severity of apical periodontitis (AP).

METHODOLOGY

Twenty-four male Wistar rats were used. AP was induced in the maxillary left/right first molars. The animals were arranged into groups: Control, Lactobacillus rhamnosus, and Lactobacillus acidophilus. Probiotics were administered orally for gavage (10⁹ colony-forming units diluted in 5 mL of water for 30 days) during the development of AP. After 30 days, cardiac puncture was performed to analyse the complete blood count. Moreover, microbiological analysis of the root canal contents and saliva was performed. Then, the animals were euthanized and the jaw removed for histopathological and IL-10, IL-1β and IL-6 immunolabeling analyses. After the Shapiro-Wilk test of normality, the Kruskal-Wallis followed by Dunn's test was performed for nonparametric data, and analysis of variance followed by the Tukey test was performed for parametric data (P < 0.05).

RESULTS

No significance difference was observed in the blood profiles and in the counts of microorganisms from the saliva samples among the groups (P > 0.05). Total microorganism counts in the root canal, the inflammatory infiltrate and the immunostaining for IL-1β and IL-6 in AP were significantly lower in the probiotic groups when compared with the control group (P < 0.05). IL-10 was significantly more immunolabled in the probiotic groups than in the control group (P < 0.05).

CONCLUSION

Supplementation with probiotics (Lactobacillus rhamnosus and Lactobacillus acidophilus) had a significant effect on the severity of apical periodontitis in rats, demonstrating the anti-inflammatory effect of probiotics on the development of apical periodontitis.

Development of Medication-Related Osteonecrosis of the Jaw After Extraction of Teeth With Experimental Periapical Disease

PURPOSE

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but severe side effect of antiresorptive medications. Most animal models use tooth extraction as an instigating local factor to induce MRONJ, with varied results. However, these teeth are healthy and absent of dental disease, a rare finding that does not reflect clinical practices. The authors hypothesized that extraction of teeth with periapical inflammation would lead to MRONJ in rats treated with high-dose bisphosphonates.

MATERIALS AND METHODS

Rats were pretreated with zoledronic acid (ZA) for 1 week. Pulp exposure (PE) was established by exposing the pulpal chamber of the first and second molars. Experimental periapical disease (EPD) was induced by PE and bacterial inoculation into pulp chambers of the first and second mandibular molars. The mandibular molars were extracted 4 weeks after PE or EPD, and animals were euthanized 4 weeks after tooth extraction. Extraction sockets were assessed clinically, radiographically, and histologically.

RESULTS

Clinically, radiographically, and histologically, socket healing was observed in all vehicle-treated animals and in ZA-treated animals after extraction of healthy teeth or teeth with PE. In contrast, bone exposure, lack of socket healing, and osteonecrosis were present in most ZA-treated animals after extraction of teeth with EPD. Bacterial presence was noted in areas of osteonecrotic alveolar bone.

CONCLUSION

These data support a synergistic contribution of severe dental disease and tooth extraction to MRONJ pathogenesis. Importantly, this model is amenable to manipulation of methodologic conditions for the dissection of parameters involved in MRONJ pathogenesis.

Tissue reaction to Aroeira (Myracrodruon urundeuva) extracts associated with microorganisms: an in vivo study

Based on aroeira's (Myracrodruon urundeuva) antimicrobial activity and a future trend to compose intracanal medication, the aim of this study was to assess in vivo inflamatory tissue response to the extracts by edemogenic and histological analysis containing inactivated facultative and anaerobic microorganisms. For edema quantification, eighteen animals were divided into three groups (n = 3, periods: 3 and 6 hours) and 0.2 mL of 1% Evans blue per 100 g of body weight was injected into the penile vein under general anesthesia. After 30 min the animals received a subcutaneous injection in the dorsal region of aqueous or ethanolic extract of aroeira or saline (control) containing inactivated bacteria. Samples were collected, immersed in formamide for 72h, and evaluated by spectrophotometry (630 m). For histological analysis, polyethylene tubes with the extracts were implanted in the dorsal of 30 male rats. Analysis of the fibrous capsule and inflammatory infiltrate were performed after 7 and 30 days. The aqueous extract group induced less edema in both postoperative periods compared to the other groups, but the differences were not significant (p > 0.05). Tissue repair was significantly better after 30 days than after 7 days (p < 0.01). The aqueous solution showed less inflammatory response than the ethanolic solution (p < 0.05), with tendency for better results than control after 7 days. After 30 days, the response to both extracts was similar to control. The aqueous and ethanolic aroeira extracts containing inactivated microorganisms showed a trend for better results than saline, even when associated with microorganisms, and facilitated the tissue repair process.

Development of a root canal treatment model in the rat

Root canal treatment is performed to treat apical periodontitis, and various procedures and techniques are currently used. Although animal models have been used in the developmental research of root canal treatment, little of this research has used small animals such as rats, because of their small size. In this study, root canal treatment was performed on the rat mandibular first molar, which had four root canals, using a microscope, and the therapeutic effect was evaluated bacteriologically, radiologically and histopathologically. By performing root canal treatment, the level of bacteria in the mesial root of the treated teeth was reduced by 75% compared with the control. Additionally, the volume of the periapical lesions of the treated teeth as measured by micro-computed tomography decreased significantly 2 weeks after the root canal treatment when compared with the control. Histological evidence of healing was observed in the treatment group 8 weeks after root canal treatment. These results suggest that a root canal treatment model using rats can be used in developmental research for novel methods of root canal treatment.

Biofilm removal and antimicrobial activity of two different air-polishing powders: an in vitro study

BACKGROUND

Biofilm removal plays a central role in the prevention of periodontal and peri-implant diseases associated with microbial infections. Plaque debridement may be accomplished by air polishing using abrasive powders. In this study, a new formulation consisting of erythritol and chlorhexidine is compared with the standard glycine powder used in air-polishing devices. Their in vitro antimicrobial and antibiofilm effects on Staphylococcus aureus, Bacteroides fragilis, and Candida albicans are investigated.

METHODS

Biofilm was allowed to grow on sandblasted titanium disks and air polished with glycine or erythritol-chlorhexidine powders. A semiquantitative analysis of biofilm by spectrophotometric assay was performed. A qualitative analysis was also carried out by confocal laser scanning microscopy. Minimum inhibitory concentrations and minimum microbicidal concentrations were evaluated, together with the microbial recovery from the residual biofilm after air-polishing treatment.

RESULTS

The combination of erythritol and chlorhexidine displayed stronger antimicrobial and antibiofilm activity than glycine against all microbial strains tested.

CONCLUSION

Air polishing with erythritol-chlorhexidine seems to be a viable alternative to the traditional glycine treatment for biofilm removal.

Promotion of endodontic lesions in rats by a novel extraradicular biofilm model using obturation materials

Although extraradicular biofilm formation is related to refractory periapical periodontitis, the mechanism of extraradicular biofilm development, as well as its effect on periapical lesions, is unknown. Therefore, we aimed to develop an in vivo extraradicular biofilm model in rats and to identify and quantify extraradicular biofilm-forming bacteria while investigating the effect of extraradicular biofilms on periapical lesions. Periapical lesions were induced by exposing the pulpal tissue of the mandibular first molars of male Wistar rats to their oral environment. Four weeks later, gutta-percha points were excessively inserted into the mesial root canals of the right first molars (experimental sites) but not the left first molars (control sites). After 6 and 8 weeks of pulp exposure, the presence of extraradicular biofilms was confirmed histomorphologically, and biofilm-forming bacteria were identified by using classical culture methods. The biofilms were observed in the extraradicular area of the experimental sites. Similar species were detected both inside and outside the root canals. The bacterial count, quantified by real-time PCR assays, in the extraradicular area gradually increased in the experimental sites until 20 weeks after pulp exposure. After 8 weeks of pulp exposure, the periapical lesion volume that was measured by micro-computed tomography was significantly larger in the experimental sites than in the control sites (P < 0.05 by Welch's t test). These results suggest that we developed an extraradicular biofilm model in rats and that extraradicular biofilms affect developing periapical lesions.

An investigation of the presence of specific anaerobic species in necrotic primary teeth

Different microbial identification methods have shown that the microbial community profiles in endodontic infections are diverse and assorted. The aim of this study was to evaluate the frequency of selected endodontic pathogens in the pulp chambers (PCs) and root canals (RCs) of infected primary teeth using PCR methods. Paired PC and RC samples were collected from 15 subjects and analyzed by PCR for the presence of Filifactor alocis, Fusobacterium nucleatum, Parvimonas micra, Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Prevotella tannerae, Tanerella forsythia, Treponema denticola, and Treponema socranskii. The frequency of each species was determined in the PC and RC of each case. The species most frequently detected in PCs were P. nigrescens (86.7%), P. gingivalis (73.3%), and F. alocis (73.3%). Of the PC samples, 13.3% contained P. micra and T. denticola, and 6.7% contained T. forsythia. The species most frequently detected in RCs were P. gingivalis (100%) and P. nigrescens (93.3%). P. tannerae, P. micra, and T. denticola were found in 40% of the RC samples; T. forsythia was found in 26.7% of the RC samples. The "red complex", which comprises P. gingivalis, T. denticola, and T. forsythia, was not found in the PC of any tooth but was found in 30% of the RC samples. The detection of P. nigrescens in the PC was statistically associated with the presence of P. nigrescens in the RC (p = 0.04). The results suggest high heterogeneity among the samples, even among those from the same subject.

Calcium-enriched mixture pulpotomy of a human permanent molar with irreversible pulpitis and condensing apical periodontitis

This case report describes a pulpotomy treatment of a permanent mature molar tooth with established irreversible pulpitis and condensing apical periodontitis, using calcium-enriched mixture (CEM) cement. Clinical examination revealed that the first right lower molar had a large carious lesion with history of spontaneous/lingering pain; radiographic examination showed condensing apical periodontitis. Pulpotomy was opted as the treatment; cervical pulpotomy was carried out. Following hemostasis, the radicular pulp stumps were covered with ~2-mm-thick layer of the prepared CEM cement; the tooth was restored with amalgam. Two-year follow-up showed that the treated tooth had been symptomless, and there were no clinical signs/symptoms of either inflammation or infection. Radiographically, the periradicular lesion was completely healed with reconstruction of bone structures to normal appearance; the root canals were not calcified. According to chemical, physical, and biological properties of the CEM cement, this novel biomaterial may be suitable for endodontic treatment.

Synergistic growth effect among bacteria recovered from root canal infections

The objective of this study was to determine the ecological relationships between bacterial species that colonize infected root canals. Root canal bacteria recovered from one patient with pulp canal necrosis were evaluated in vitro for synergistic and antagonistic activities determined by mono and co-culture growth kinetics and the production of bacteriocin-like substances using the double layer diffusion method. Peptostreptococcus prevotii triggered a significant increase of Fusobacterium nucleatum growth, while the former bacteria did not affect the growth of P. prevotii. The bacterial species did not produce antagonism activity against itself or against any of the other two species. Despite many studies have demonstrated the capability of root canal microorganisms to produce antagonistic substances, these in vitro experimental tests show the synergistic effect of P. prevotii on the growth of F. nucleatum.

Studying bacterial infections through culture-independent approaches

The ability to characterize accurately the cause of infection is fundamental to effective treatment. The impact of any antimicrobial agents used to treat infection will, however, always be constrained by both the appropriateness of their use and our ability to determine their effectiveness. Traditional culture-based diagnostic microbiology is, in many cases, unable to provide this information. Molecular microbiological approaches that assess the content of clinical samples in a culture-independent manner promise to change dramatically the types of data that are obtained routinely from clinical samples. We argue that, in addition to the technical advance that these methodologies offer, a conceptual advance in the way that we reflect on the information generated is also required. Through the development of both of these advances, our understanding of infection, as well as the ways in which infections can be treated, may be improved. In the analysis of the microbiological content of certain clinical samples, such as blood, cerebrospinal fluid, brain and bone biopsy, culture-independent approaches have been well documented. Herein, we discuss how extensions to such studies can shape our understanding of infection at the many sites of the human body where a mixed flora, or in more ecological terms, a community of microbes, is present. To do this, we consider the underlying principles that underpin diagnostic systems, describe the ways in which these systems can be applied to community characterization, and discuss the significance of the data generated. We propose that at all locations within the human body where infection is routinely initiated within the context of a community of microbes, the same principles will apply. To consider this further, we take insights from areas such as the gut, oral cavity and skin. The main focus here is understanding respiratory tract infection, and specifically the infections of the cystic fibrosis lung. The impact that the use of culture-independent, molecular analyses will have on the way we approach the treatment of infections is also considered.

Expression of Toll-like receptor 2 and 4 in inflamed pulp in severe combined immunodeficiency mice

INTRODUCTION

Toll-like receptors (TLRs) are important receptors mediating innate immune responses because they detect factors released from bacterial cell wall components during inflammatory reactions. However, the role of TLRs in dental pulp, which is bounded by hard tissues, is poorly understood. The purpose of this study was to investigate the relationship between the innate immune system and the defense of pulp tissue by using immunodeficient mice that lack an adaptive immune response

METHODS

Mice with severe combined immunodeficiency (SCID) were used as a model because they lack an adaptive immune response. The expression of TLR-2 and TLR-4 in experimentally inflamed pulps in SCID mice was measured by quantitative real-time polymerase chain reaction and immunohistochemistry. Total RNA was isolated from pulp tissues at 0 to 24 hours after bacterial dentinal infection. Anti-TLR-2, anti-TLR-4 cells, anti-CD64, and antinestin cells were detected with labeled streptavidin-biotin methods.

RESULTS

TLR-2 messenger RNA was detected at 3 hours after bacterial infection and then gradually increased from 9 to 24 hours. Numerous TLR-2- and CD64-positive cells detected on macrophages and dendritic-like cells, and TLR-4- and CD64-positive macrophages were detected in the early stage of pulpitis.

CONCLUSION

These results suggest that the expression of TLR-2 and TLR-4 may be triggered by bacterial infection in irreversible pulpitis without a need for an adaptive immune response. Those signals may relate to pulpal responses to bacterial infection.

Detection of periapical lesion development by conventional radiography or computed tomography

OBJECTIVE

The aim of this study was to detect the development of experimentally induced periapical lesions using conventional radiography and computed tomography.

STUDY DESIGN

The root canals of dogs' teeth were exposed to the oral environment for 7 days for contamination and then sealed for 7 days (GI), 15 days (GII), 30 days (GIII), and 60 days (GIV). Immediately after each experimental period, radiographs and tomograms were taken in order to detect the occurrence of periapical bone resorption. The periapical radiographs were digitized and areas of bone resorption were measured using the VIXWIN 2000 software. Scores were assigned to the tomograms based on the progression of periapical bone resorption. The specimens were evaluated by calibrated examiners who were blinded to the groups. The radiographic results were analyzed by ANOVA and Tukey's test (P < .05) and the tomographic results were analyzed by Kruskal-Wallis and Dunn's tests (P < .05).

RESULTS

The radiographic evaluation did not reveal periapical lesions at the 7-day control. Lesions were radiographically visible at 15 and 30 days (47.4% and 77.8% of the cases, respectively) and presented similar dimensions (P > .05). At 60 days, lesions were detected in all specimens, presenting larger dimensions than those of the earlier evaluation periods (P < .05). The tomographic evaluation detected lesions at 7 and 15 days (32.5% and 83.3% of the cases, respectively). Lesions were detected in all specimens at the 30- and 60-day periods, when the greatest values of bone resorption were observed (P < .05).

CONCLUSIONS

Tomography was able to detect periapical lesion development in its initial stages, even when the lesions were undetectable radiographically.

Bacterial profile in primary teeth with necrotic pulp and periapical lesions

The objective of this study was to evaluate the bacterial profile in root canals of human primary teeth with necrotic pulp and periapical lesions using bacterial culture. A total of 20 primary teeth with necrotic pulp and radiographically visible radiolucent areas in the region of the bone furcation and/or the periapical region were selected. After crown access, 4 sterile absorbent paper points were introduced sequentially into the root canal for collection of material. After 30 s, the paper points were removed and placed in a test tube containing reduced transport fluid (RTF) and were sent for microbiological evaluation. Anaerobic microorganisms were found in 100% of the samples, black-pigmented bacilli in 30%, aerobic microorganisms in 60%, streptococci in 85%, Gram-negative aerobic rods in 15% and staphylococci were not quantified. Mutans streptococci were found in 6 root canals (30%), 5 canals with Streptococcus mutans and 1 canal with Streptococcus mutans and Streptococcus sobrinus. It was concluded that in root canals of human primary teeth with necrotic pulp and periapical lesions, the infection is polymicrobial with predominance of anaerobic microorganisms.

Methods of experimental induction of periapical inflammation. Microbiological and radiographic evaluation

AIM

To evaluate the influence of coronal filling and apical perforation on the induction of periapical inflammation.

METHODOLOGY

Fifty-eight root canals in the teeth of dogs were divided into four groups. Groups I and II: root canals were exposed for 180 days; groups III and IV: root canals were exposed for 7 days and then the access cavity filled for 53 days. The root apices of groups I and III were perforated after the coronal opening, whilst those of groups II and IV remained intact. Standard radiographs were taken before and after the experimental periods. Digital images of the radiographs were created and then analysed by three examiners. After induction of periapical inflammation, the root canal contents were collected using paper points. Microbiologic evaluation of the type of microorganism was carried out by culture in different growth media. The radiographic and microbiologic data were statistically analysed using anova at a 5% significance level.

RESULTS

There were a greater total number of microorganisms in groups I and II (P < 0.05). The number of anaerobes was greater than the number of aerobes (P < 0.05). The size of the periapical radiolucencies were not significantly different between the experimental groups.

CONCLUSIONS

The different methods analysed induced similar areas of periapical radiolucency in dogs with predominantly anaerobic bacteria. However, the time required for induction was less when the method with coronal filling was used.

Effect of root canal dressings on the regeneration of inflamed periapical tissue

The aim of this study was to evaluate the effects of chlorhexidine and calcium hydroxide on apical periodontitis in rats. Experimentally induced apical periodontitis was established on the mesial roots of maxillary molars of Wistar rats by leaving the root canals exposed to the oral cavity for 14 d. In the positive control group (n=10 teeth), the root canals were not further treated, but the coronal access openings were filled with composite. In the negative control group (n=10 teeth), partial pulpotomies were performed aseptically and the coronal access openings were sealed immediately. In a third control group (n=10 teeth) the canals were instrumented, left empty, and the coronal access openings were sealed. In the experimental groups, the root canals were instrumented and filled with either 2% chlorhexidine gel or calcium hydroxide paste (n=10 teeth per group). After 7 d all rats were killed and the histological sections were stained for microscopic analysis of periapical regeneration. The data of the subjective evaluation were analyzed with the Kruskal-Wallis test. Lesion sizes were measured and statistically analyzed using the ANOVA and post-hoc Scheffé test. The two treatment groups showed significantly lower average inflammatory scores and smaller lesion sizes than the positive and third control group (p<0.05). No statistically significant differences were obtained between the two treatment groups (p>0.05). Chlorhexidine used as an intra-canal medicament showed good periapical regeneration, suggesting that this may be an alternative to calcium hydroxide root canal dressing.

In vitro effects of calcium hydroxide and polymyxin B on endotoxins in root canals

OBJECTIVES

To evaluate the effects of intracanal medicaments on endotoxins in root canals.

METHODS

Seventy-five freshly extracted maxillary incisors were used in this study. The crowns of teeth were sectioned near the CEJ in order to standardize the root length to 14 mm. The root canals were instrumented to an apical size #50 file and irrigated with 1% sodium hypochlorite solution and sterilized with 60Co gamma irradiation. Standardized suspension containing Escherichia coli endotoxin was inoculated into the 60 root canals. The specimens were randomly assigned to 5 groups (n=15), according to the intracanal medicament used: (G1) calcium hydroxide; (G2) polymyxin B; (G3) combination neomycin-polymyxin B-hydrocortisone; (G4) positive control (no intracanal medicament); (G5) negative control (no endotoxin and no intracanal medicament). After 7 days, the detoxification of endotoxin was evaluated by Limulus lysate assay and antibody production in B-lymphocytes culture.

RESULTS

Groups 1, 2 and 5 presented the best results by Limulus lysate and were significantly different to groups 3 and 4 (p<0.05). Stimulation of antibodies production in cell culture by groups 1 and 6 was smaller and statistically different than groups 2, 3, 4 and 5 (p<0.05). Groups 2 and 5 induced a small increase in the antibodies production in relation to the groups 1 and 6. Groups 3 and 4 induced a significant increase of antibodies production (p<0.05).

CONCLUSIONS

The calcium hydroxide and polymyxin B intracanal medicaments detoxified endotoxin in root canals and altered the properties of LPS to stimulate the antibody production by B-lymphocytes. The combination neomycin-polymyxin B-hydrocortisone did not detoxified endotoxin.

Simultaneous Detection of Dialister pneumosintes and Filifactor alocis in Endodontic Infections by 16S rDNA-directed Multiplex PCR

Dialister pneumosintes and Filifactor alocis have been recently considered as candidate endodontic pathogens. In this study, we devised a 16S rDNA-directed multiplex PCR protocol for simultaneous detection of these two bacterial species in endodontic infections. Samples were taken from infected root canals associated with asymptomatic periradicular lesions as well as from cases of acute periradicular abscesses. DNA extracted from the samples was used as template for simultaneous detection of D. pneumosintes and F. alocis through a multiplex PCR assay. Two fragments of the expected sizes, one specific for D. pneumosintes and the other for F. alocis, were simultaneously amplified from a mixture of reference genomic DNA containing DNA from both species. Clinical samples that were positive for the target species showed a single band of the predicted size for each species. D. pneumosintes was detected by multiplex PCR in 11 samples (7 asymptomatic and 4 abscesses) and F. alocis was identified in 9 cases (6 asymptomatic and 3 abscesses). Six samples (3 asymptomatic and 3 abscesses) shared the two species. Data from the present study confirmed that D. pneumosintes and F. alocis are common members of the microbiota present in primary endodontic infections and thereby may participate in the pathogenesis of periradicular lesions. The proposed multiplex PCR assay is a simple, rapid, and accurate method for the simultaneous detection of these two candidate endodontic pathogens.

Clinical and Radiographic Evaluation of Root-canal Obturation with Obtura II

This study evaluated clinical and radiographic healing of 236 root-canal treatments in 131 cases obturated with the Obtura II system. One operator performed all canal preparation and obturation with sealer. A standardized apical-coronal preparation technique instrumented all canals. Clinical symptoms, periodontal condition, and radiographic findings were evaluated at 3, 6, and 12 months. Radiographs taken immediately postobturation were compared to recall radiographs. The level of the final root filling was classified as short (more than 2 mm short of the apex), flush (within 2 mm), or over (beyond) in 12.7%, 81.4%, and 5.9% of cases, respectively. More than 96% of cases were treated successfully by the Obtura II system. Where roots were filled flush, over, or short, lesions healed in 97%, 93%, and 93% of cases, respectively, with no significant differences (p < 0.05). Root filling excess had no impact on the healing process.

Positive and negative bacterial associations involving Dialister pneumosintes in primary endodontic infections

Dialister pneumosintes is an anaerobic Gram-negative rod that has been recently implicated as a candidate endodontic pathogen. In this study, samples taken from abscessed teeth and infected root canals associated with asymptomatic or symptomatic periradicular lesions were examined for the occurrence of bacterial associations involving D. pneumosintes. DNA was extracted from the samples, and the presence of D. pneumosintes and 16 other bacterial species was determined by means of species-specific nested polymerase chain reaction. Positive and negative associations involving D. pneumosintes were investigated by computing the odds ratio of D. pneumosintes being found in a sample from endodontic infection in co-infection with one of the other target species. The association between the pairs containing D. pneumosintes and the occurrence of pain also was evaluated. D. pneumosintes was always detected in mixed infections with at least two of the other target species. D. pneumosintes was positively associated with Treponema denticola, Porphyromonas endodontalis, Fusobacterium nucleatum, Peptostreptococcus micros, Campylobacter rectus, Prevotella intermedia, T. pectinovorum, and T. vincentii. Negative associations were observed with Bacteroides forsythus, P. gingivalis, and Actinomyces israelii. No pair containing D. pneumosintes was found to be significantly associated with symptomatic cases (p > 0.01). The findings of this study lend considerable support to the notion of D. pneumosintes being an important endodontic pathogen, usually in a mixed infection. Positive associations of this species with other highly prevalent species, such as T. denticola and P. endodontalis, suggest that bacterial synergism can occur and thereby play an important role in the pathogenesis of different forms of periradicular lesions.

Bacterial concentrations determine the ability to implant in the root canal system and translocate to lymph nodes in germ-free mice

The purpose of this study was to evaluate the influence of the infecting dose on bacterial colonization in root canal systems (RCS) and translocation to the submandibular lymph node (SML) of gnotobiotic (germ-free) mice. RCS were inoculated with 10(2) and 10(1) colony-forming units (CFU) of Enterococcus faecalis (ATCC 4083) or 10(5), 10(4), 10(3), and 10(2) CFU of Prevotella nigrescens (ATCC 33563). E. faecalis implanted in 83.3% of the cases, for both inocula. Translocation was detected in 58.3% of lymph nodes for the 10(2) CFU inoculum and in 33.3% of lymph nodes for the 10(1) CFU inoculum. P. nigrescens implanted in 25%, 16.7%, 8.3%, and 0%, for the 10(5), 10(4), 10(3), and 10(2) CFU inocula, respectively, and did not translocate at any of the concentrations used. These results indicate that E. faecalis was able to implant in the RCS and translocate to the SML, whereas P. nigrescens implanted in lower percentages in the RCS and did not translocate to the SML.

Dialister pneumosintes can be a suspected endodontic pathogen

OBJECTIVE

Dialister pneumosintes is a nonmotile, nonfermentative, non-spore-forming, obligately anaerobic, gram-negative bacillus that has been associated with some infections in the human body. A species-specific nested polymerase chain reaction assay was used to investigate the occurrence of D pneumosintes in primary root canal infections.

STUDY DESIGN

Samples were collected from 32 teeth with carious lesions, necrotic pulps, and radiographic evidence of periradicular bone destruction. Twenty-two teeth were asymptomatic, and 10 cases were diagnosed as acute apical periodontitis. DNA extracted from the samples was initially amplified with universal 16S ribosomal DNA primers. A second round of amplification used the first polymerase chain reaction products to specifically detect D pneumosintes.

RESULTS

This bacterial species was detected in 17 of 22 asymptomatic cases (77.3%) and in 4 of 10 root canals associated with acute apical periodontitis (40%). No relationship was found between the presence of this bacterial species and the occurrence of symptoms. In general, D pneumosintes was detected in 21 of 32 root canal samples (65.6%).

CONCLUSION

This study is the first to report a high prevalence of D pneumosintes in root canal infections of humans. Because of this high prevalence and the apparent pathogenicity of the microorganism, we suggest the inclusion of D pneumosintes in the selected group of putative endodontic pathogens.

Endodontic infections: concepts, paradigms, and perspectives

Overwhelming evidence indicates that periradicular diseases are infectious disorders. The question now is no longer whether microorganisms are involved in the pathogenesis of such diseases, but which specific microbial species are. The list of microorganisms involved in periradicular diseases keeps expanding and has the potential to become increasingly more accurate during the next few years. Molecular methods have contributed significantly to the knowledge about the microbial species involved. Undoubtedly, a great deal of additional research is needed to define the specific role played by suspected endodontic pathogens in the etiology of each form of periradicular disease and to determine the best therapeutic measures for the pathogen's eradication. In addition, there is an emergent need to define markers that permit the clinician to know when he or she should conclude the treatment and to predict the outcome of the treatment. Although endodontic procedures and some acute endodontic infections can cause bacteremia, there is no clear evidence that microorganisms from the root canal can cause diseases in remote sites of the body. However, there is a risk in some compromised individuals, and prophylactic measures should be taken. Prescription of systemic antibiotics in endodontic therapy is rarely necessary. Because of the emergence of bacterial resistance against most known antibiotics, their use in endodontics should be highly limited and restricted to a few cases.

Periapical lesion progression with controlled microbial inoculation in a type I diabetic mouse model

Uncontrolled or poorly controlled diabetes mellitus may be a risk factor for the development of large and/or debilitating periapical infections. The objectives of this investigation were to: (i) determine the effect of diabetes mellitus on the pathogenesis of periapical lesions with or without specific bacterial inoculations at the exposure sites, and (ii) test the sensitivities of two microbiological techniques in detecting the persistence of the bacterial inoculum in exposed pulps of nonobese diabetic (NOD) mice. Periapical lesions were induced in first molars of 29 female NOD mice and 31 BALB/c controls. Acute (1-2 wk) or chronic (5 wk) exposures were either inoculated with a mixture of facultative and anaerobic bacteria or exposed to oral flora without inoculations. After death the teeth in the chronic groups were analyzed for the presence of the inoculated bacteria by culturing and by polymerase chain reaction amplification of 16S rDNA. Periapical lesion size was measured histomorphometrically and the interleukin-6 content was measured immunohistochemically. The mortality among NOD mice with inoculated and sealed exposures was 83%, compared with 29% for BALB/c mice. In the inoculated and uninoculated chronic NOD mice groups, 38% of the animals versus none of the BALB/c mice died. The chronic uninoculated NOD mice lost significantly more weight at the time of death than controls. Polymerase chain reaction was more sensitive than culturing in detecting the inoculated anaerobic bacteria. In the animals that survived to the predetermined time periods, lesion size and interleukin-6 content in NOD and BALB/c mice were not statistically different.

Microorganisms isolated from root canals presenting necrotic pulp and their drug susceptibility in vitro

The knowledge about causative agents involved in endodontic infections is increasing, especially due to the improvement of culture techniques for anaerobic bacteria, showing that these microorganisms are predominant in this pathology. In this study, 31 canals with pulp necrosis were microbiologically analyzed before and after manipulation. Obligate and facultative anaerobes, microaerophilic bacteria and yeasts were recovered from 24, 14, 5 and 2 clinical specimens, respectively. The most frequent genera were Prevotella, Fusobacterium, Lactobacillus, Streptococcus, Clostridium and Peptostreptococcus for bacteria and Candida and Saccharomyces for yeasts. Strong positive associations, using an odds ratio system, were found between Clostridium and Prevotella and between Peptostreptococcus and Fusobacterium. Even after the instrumentation and the use of Ca(OH)2, facultative anaerobes were detected in two root canals and yeasts in three. Microorganisms were isolated from seven canals at the end of the endodontic treatment: facultative anaerobes from five and yeasts from one. The microbiological evaluation of root canals with pulp necrosis suggests the presence of polymicrobial infections, mainly involving obligate anaerobes, and shows that the infection may persist after treatment.

Importance of Dialister pneumosintes in human periodontitis

Anaerobic bacteria play important roles in the pathogenesis of human periodontitis. This study examined the relationship between a potentially new periodontopathic bacterium Dialister pneumosintes and periodontal disease. A total of 73 women and 62 men aged 18 to 86 years participated in the study. Using a 16S rRNA polymerase chain reaction identification method, the presence of D. pneumosintes was determined in paper-point samples from periodontal pockets of 105 periodontitis and 30 gingivitis patients. D. pneumosintes was detected in 83% of patients having severe periodontitis and in 19% of patients having slight periodontitis. We suggest adding D. pneumosintes to the group of suspected periodontal pathogens.