Towards microbiome transplant as a therapy for periodontitis: an exploratory study of periodontitis microbial signature contrasted by oral health, caries and edentulism

Dynamics of the oral microbiome during orthodontic treatment and antimicrobial advances for orthodontic appliances

The oral microbiome plays an important role in human health, and an imbalance of the oral microbiome could lead to oral and systemic diseases. Orthodontic treatment is an effective method to correct malocclusion. However, it is associated with many adverse effects, including white spot lesions, caries, gingivitis, periodontitis, halitosis, and even some systematic diseases. Undoubtedly, increased difficulty in oral hygiene maintenance and oral microbial disturbances are the main factors in developing these adverse effects. The present article briefly illustrates the characteristics of different ecological niches (including saliva, soft tissue surfaces of the oral mucosa, and hard tissue surfaces of the teeth) inhabited by oral microorganisms. According to the investigations conducted since 2014, we comprehensively elucidate the alterations of the oral microbiome in saliva, dental plaque, and other ecological niches after the introduction of orthodontic appliances. Finally, we provide a detailed review of recent advances in the antimicrobial properties of different orthodontic appliances. This article will provide researchers with a profound understanding of the underlying mechanisms of the effects of orthodontic appliances on human health and provide direction for further research on the antimicrobial properties of orthodontic appliances.

Characterising healthy Australian oral microbiomes for 'super donor' selection

OBJECTIVES

Among healthy people, we understand very little about the sociodemographic, lifestyle, and dental hygiene behaviours that shape their oral microbiota. This study investigates how sociodemographic, lifestyle and dental hygiene behaviours shape oral microbiota diversity and composition in an Australian population to better inform healthy oral microbiota donors for Oral Microbiota Transplantation (OMT).

METHODS

The study comprised 93 healthy adults who underwent comprehensive oral examinations and questionnaires to assess their health status. Participants were excluded if they had any active systemic or oral disease. All completed a questionnaire containing information on socio-economic, lifestyle, behavioural, and oral health factors. Supragingival plaque was collected, and 16S ribosomal RNA (rRNA) amplicon sequencing was used to analyse microbial composition. Associations between the core microbiome, alpha- (within-sample), beta-diversity (between-sample) and an individual's co-variates were tested for statistical significance. A redundancy analysis (RDA), multivariate adonis, differential abundance and correlation analysis were performed to characterise which factors drive the variation in the healthy oral microbiome.

RESULTS

Streptococcus and Corynebacterium were the most prevalent and abundant genera among healthy Australians. The alpha and beta diversity were higher among unemployed non-Australian-born students who consumed low carbohydrates, fat, and sugar and had not visited the dentist for over 12 months. Additionally, beta diversity was significantly higher among daily flossers who abstained from fluoride treatment and had high salivary pH, although no single factor explained >4 % of the total variation (R2= 0.042). Alloprevotella, Lachnosporacea, and Parvimonas were significantly abundant among non-Australians who did not visit the dentist within a year. The RDA analysis revealed associations between microbiome composition and factors such as high carbohydrate, sugar, and fat consumption, low fibre intake, and regular dental checks among Australian-born individuals.

CONCLUSION

These findings indicate that alpha and beta diversity of the oral microbiome varied significantly with sociodemographic, lifestyle, and dietary factors, including non-Australian birthplaces, unemployment, diet, and infrequent dental visits.

CLINICAL SIGNIFICANCE

These findings underscore the importance of considering diverse sociodemographic, lifestyle, and dietary factors in oral health management. Before microbiome transplantations, clinicians should account for individual characteristics that may be beneficial for shaping and maintaining optimal oral microbiome diversity and health.

Periodontal bacteria influence systemic diseases through the gut microbiota

Many systemic diseases, including Alzheimer disease (AD), diabetes mellitus (DM) and cardiovascular disease, are associated with microbiota dysbiosis. The oral and intestinal microbiota are directly connected anatomically, and communicate with each other through the oral-gut microbiome axis to establish and maintain host microbial homeostasis. In addition to directly, periodontal bacteria may also be indirectly involved in the regulation of systemic health and disease through the disturbed gut. This paper provides evidence for the role of periodontal bacteria in systemic diseases via the oral-gut axis and the far-reaching implications of maintaining periodontal health in reducing the risk of many intestinal and parenteral diseases. This may provide insight into the underlying pathogenesis of many systemic diseases and the search for new preventive and therapeutic strategies.

Microbiota transplantation

Microbiota refers to a collection of living microorganisms, including bacteria, yeasts, and viruses, that coexist in various sites of the human body. Microbiota can perform multiple functions in the body, which have an essential effect on human health and homeostasis. For example, the microbiota can digest polysaccharides, produce vitamins, modulate the immune system, and protect the body against pathogens. Various factors can occasionally alter the microbiota population in the human body, a condition known as dysbiosis. Dysbiosis can disrupt the homeostasis of a person's body and cause disease. Recent years have witnessed efforts to restore the microbiota population of an individual's body to its original state and eradicate dysbiosis through microbiota transplantation. The noteworthy point is that different methods such as fecal microbiota transplantation, vaginal microbiota transplantation (VMT), skin microbiota transplantation (SMT), oral microbiota transplantation (OMT), washed microbiota transplantation (WMT), and sinonasal microbiota transplantation (SiMT) are used for microbiota transplantation (MT). According to the results of studies and the usefulness of MT in improving a person's health, the purpose of this study is to investigate different methods of MT to eliminate dysbiosis.

Mechanisms underlying the effects, and clinical applications, of oral microbiota in lung cancer: current challenges and prospects

The oral cavity contains a site-specific microbiota that interacts with host cells to regulate many physiological processes in the human body. Emerging evidence has suggested that changes in the oral microbiota can increase the risk of lung cancer (LC), and the oral microbiota is also altered in patients with LC. Human and animal studies have shown that oral microecological disorders and/or specific oral bacteria may play an active role in the occurrence and development of LC through direct and/or indirect mechanisms. These studies support the potential of oral microbiota in the clinical treatment of LC. Oral microbiota may therefore be used in the prevention and treatment of LC and to improve the side effects of anticancer therapy by regulating the balance of the oral microbiome. Specific oral microbiota in LC may also be used as screening or predictive biomarkers. This review summarizes the main findings in research on oral microbiome-related LC and discusses current challenges and future research directions.

Oral microbiota and metabolites: key players in oral health and disorder, and microbiota-based therapies

The review aimed to investigate the diversity of oral microbiota and its influencing factors, as well as the association of oral microbiota with oral health and the possible effects of dysbiosis and oral disorder. The oral cavity harbors a substantial microbial burden, which is particularly notable compared to other organs within the human body. In usual situations, the microbiota exists in a state of equilibrium; however, when this balance is disturbed, a multitude of complications arise. Dental caries, a prevalent issue in the oral cavity, is primarily caused by the colonization and activity of bacteria, particularly streptococci. Furthermore, this environment also houses other pathogenic bacteria that are associated with the onset of gingival, periapical, and periodontal diseases, as well as oral cancer. Various strategies have been employed to prevent, control, and treat these disorders. Recently, techniques utilizing microbiota, like probiotics, microbiota transplantation, and the replacement of oral pathogens, have caught the eye. This extensive examination seeks to offer a general view of the oral microbiota and their metabolites concerning oral health and disease, and also the resilience of the microbiota, and the techniques used for the prevention, control, and treatment of disorders in this specific area.

Oral microbiota transplantation for intra-oral halitosis: a feasibility analysis based on an oral microbiota colonization trial in Wistar rats

BACKGROUND

Intra-oral halitosis (IOH) is bad breath produced locally by the mouth in addition to systemic diseases and is one of the main causes of interpersonal communication and psychological disorders in modern society. However, current treatment modalities still only alleviate IOH and do not eradicate it. Therefore, based on the differential performance of oral microecology in IOH patients, we propose a microbiota transplantation treatment aimed at restoring oral microecological balance and analyze its feasibility by oral flora colonization test in Wistar rats.

OBJECTIVE

Saliva flora samples were collected from IOH patients and healthy subjects to analyze the feasibility of oral microbiota transplantation (OMT) for the treatment of IOH by the Wistar rat oral flora colonization test.

METHODS

Seven patients with IOH who visited the First Affiliated Hospital of Xinjiang Medical University from June 2017 to June 2022 with the main complaint of halitosis and three healthy subjects were randomly selected. A Halimeter portable breath detector was used to record breath values and collect saliva flora samples. Sixteen SPF-grade male Wistar rats were housed in the Animal Experiment Center of Xinjiang Medical University and randomly divided into an experimental group (Group E) and a control group (Group C) for the oral flora colonization test. Species composition and associated metabolic analysis of oral flora during the Wistar rat test using 16SrRNA sequencing technology and PICRUSt metabolic analysis. Also, the changes in the breath values of the rats were recorded during the test.

RESULTS

The proportion of Porphyromonas, Fusobacterium, Leptotrichia, and Peptostreptococcus was significantly higher in group E compared to group C after colonization of salivary flora of IOH patients (all P < 0.05), and the abundance with Gemella was zero before colonization, while no colonization was seen in group C after colonization compared to baseline. PICRUSt metabolic analysis also showed significantly enhanced IOH-related metabolic pathways after colonization in group E (all P < 0.05), as well as significantly higher breath values compared to baseline and group C (all P < 0.0001). After colonization by salivary flora from healthy subjects, group E rats showed a decrease in the abundance of associated odor-causing bacteria colonization, a reduction in associated metabolism, and a significant decrease in breath values. In contrast, group C also showed differential changes in flora structure and breath values compared to baseline after salivary flora colonization of IOH patients.

CONCLUSIONS

OMT for IOH is a promising green treatment option, but the influence of environmental factors and individual differences still cannot be ignored.

Microbiota Transplantation as an Adjunct to Standard Periodontal Treatment in Periodontal Disease: A Systematic Review

Periodontitis is a disease linked to severe dysbiosis of the subgingival microbiome. The treatment of periodontitis aims to change the dysbiosis environment to a symbiosis environment. We hypothesized that oral microbiota transplantation can lead to a significant improvement in periodontitis. Therefore, the aim of this study was to determine the effectiveness of microbiota transplantation after standard periodontal treatment in periodontitis patients. The search strategy was carried out by using the Boolean term "AND" to combine the keywords, which were "periodontitis AND microbiota transplantation". Due to the limited resources of the study, we included both in vitro and in vivo investigations in this systematic review. The QUIN risk of bias tool was employed to assess the risk of bias in in vitro studies, while SYRCLE's risk of bias assessment was used for in vivo studies. Oral microbiota transplants (OMTs) have shown potential in treating periodontitis. OMTs significantly reduced periodontitis-associated pathogenic microbial species (P. endodontalis, Prevotella intermedia, T. vincentii, Porphyromonas sp.) and increased beneficial bacteria (P. melaninogenica, Fusobacterium nucleatum, P. catoniae, Capnocytophaga ochracea, C. sputigena, C. gingivalis, Haemophilus parainfluenzae, and Neisseria elongata) upon in vitro testing. Furthermore, in the in vivo tests, single adjunctive OMT also had an effect on the oral microbiota composition compared to the full-mouth mechanical and antimicrobial debridement. OMTs may be cheaper and more effective at addressing high-risk individuals. At present, it is not possible to provide OMT clinical advice due to the lack of available information. This treatment needs to be subjected to more safety and efficacy testing before being included human clinical trials.

Predicting potential microbe-disease associations based on multi-source features and deep learning

Studies have confirmed that the occurrence of many complex diseases in the human body is closely related to the microbial community, and microbes can affect tumorigenesis and metastasis by regulating the tumor microenvironment. However, there are still large gaps in the clinical observation of the microbiota in disease. Although biological experiments are accurate in identifying disease-associated microbes, they are also time-consuming and expensive. The computational models for effective identification of diseases related microbes can shorten this process, and reduce capital and time costs. Based on this, in the paper, a model named DSAE_RF is presented to predict latent microbe-disease associations by combining multi-source features and deep learning. DSAE_RF calculates four similarities between microbes and diseases, which are then used as feature vectors for the disease-microbe pairs. Later, reliable negative samples are screened by k-means clustering, and a deep sparse autoencoder neural network is further used to extract effective features of the disease-microbe pairs. In this foundation, a random forest classifier is presented to predict the associations between microbes and diseases. To assess the performance of the model in this paper, 10-fold cross-validation is implemented on the same dataset. As a result, the AUC and AUPR of the model are 0.9448 and 0.9431, respectively. Furthermore, we also conduct a variety of experiments, including comparison of negative sample selection methods, comparison with different models and classifiers, Kolmogorov-Smirnov test and t-test, ablation experiments, robustness analysis, and case studies on Covid-19 and colorectal cancer. The results fully demonstrate the reliability and availability of our model.

Subgingival microbiome in periodontal health, gingivitis and different stages of periodontitis

AIM

To characterize the subgingival microbiome in subjects with different periodontal health statuses.

MATERIALS AND METHODS

In this cross-sectional observational study, subgingival samples were harvested from Spanish subjects with different periodontal health statuses, based on the 2018 Classification of Periodontal and Peri-Implant Diseases and Conditions. Samples were processed using high-throughput sequencing technologies (Illumina MiSeq). Taxa differentially abundant were identified using Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC). α- and β-diversity metrics were calculated using q2-diversity in QIIME2. The analyses were adjusted for age, gender and smoking status.

RESULTS

The identified subgingival microbiome showed statistically significant differences among subjects, categorized into periodontal health, gingivitis and stages I-II and III-IV periodontitis (p < .05). In patients with severe (stages III-IV) periodontitis, the genera Filifactor and Fretibacterium were detected 24 times more frequently than in periodontally healthy subjects. Similarly, the genera Porphyromonas, Prevotella and Tannerella were detected four times more frequently (p < .05). The genera Granulicatella, Streptococcus, Paracoccus, Pseudomonas, Haemophilus, Actinobacteria, Bergeyella and Capnocytophaga were significantly associated with healthier periodontal status (p < .05).

CONCLUSIONS

Significant differences were detected in the subgingival microbiome among periodontal health, gingivitis and stages I-II or III-IV periodontitis, suggesting overlapping, yet distinguishable microbial profiles.

The Oral Microbiota in Valvular Heart Disease: Current Knowledge and Future Directions

Oral microbiota formation begins from birth, and everything from genetic components to the environment, alongside the host's behavior (such as diet, smoking, oral hygiene, and even physical activity), contributes to oral microbiota structure. Even though recent studies have focused on the gut microbiota's role in systemic diseases, the oral microbiome represents the second largest community of microorganisms, making it a new promising therapeutic target. Periodontitis and dental caries are considered the two main consequences of oral bacterial imbalance. Studies have shown that oral dysbiosis effects are not limited locally. Due to technological advancement, research identified oral bacterial species in heart valves. This evidence links oral dysbiosis with the development of valvular heart disease (VHD). This review focuses on describing the mechanism behind prolonged local inflammation and dysbiosis, that can induce bacteriemia by direct or immune-mediated mechanisms and finally VHD. Additionally, we highlight emerging therapies based on controlling oral dysbiosis, periodontal disease, and inflammation with immunological and systemic effects, that exert beneficial effects in VHD management.

Immunomodulatory role of oral microbiota in inflammatory diseases and allergic conditions

In recent years, the interplay between oral microbiota and systemic disease has gained attention as poor oral health is associated with several pathologies. The oral microbiota plays a role in the maintenance of overall health, and its dysbiosis influences chronic inflammation and the pathogenesis of gum diseases. Periodontitis has also been associated with other diseases and health complications such as cancer, neurogenerative and autoimmune disorders, chronic kidney disease, cardiovascular diseases, rheumatic arthritis, respiratory health, and adverse pregnancy outcomes. The host microbiota can influence immune cell development and immune responses, and recent evidence suggests that changes in oral microbiota composition may also contribute to sensitization and the development of allergic reactions, including asthma and peanut allergies. Conversely, there is also evidence that allergic reactions within the gut may contribute to alterations in oral microbiota composition. Here we review the current evidence of the role of the oral microbiota in inflammatory diseases and health complications, as well as its future relevance in improving health and ameliorating allergic disease.

Molecular Iodine Mouthrinse Antimicrobial Activity Against Periodontopathic Bacteria

AIM

This study compared two molecular iodine mouthrinses for their in vitro bactericidal effects against subgingival biofilm bacteria from severe periodontitis patients.

MATERIALS AND METHODS

In a subgingival biofilm eradication assay, dilution aliquots of subgingival microbial specimens from 32 adults with severe periodontitis were mixed in vitro with either a mouthrinse containing 100 parts per million (ppm) molecular iodine (Iorinse®) or one containing 150 ppm molecular iodine (iClean®), followed by mouthrinse neutralization after 60 seconds with 3% sodium thiosulfate. The mixtures, along with unexposed subgingival biofilm aliquots, were inoculated onto enriched Brucella blood agar and incubated anaerobically for 7 days to quantitate total viable bacterial counts and selected red/orange complex periodontal pathogens (Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Parvimonas micra, Campylobacter rectus, and Fusobacterium nucleatum).

RESULTS

Both molecular iodine mouthrinses significantly reduced total viable bacterial counts in the subgingival biofilm samples, with iClean® providing significantly greater in vitro suppression than Iorinse®. Both molecular iodine mouthrinses also significantly reduced total red/orange complex periodontal pathogens, with significantly greater suppression also exhibited by iClean®.

CONCLUSION

The molecular iodine mouthrinses exerted marked bactericidal activity in vitro against human subgingival biofilm microbial species, including red/orange complex periodontal pathogens associated with severe periodontitis, with iClean® providing significantly better antimicrobial activity than Iorinse®.

CLINICAL SIGNIFICANCE

These findings suggest potential value of molecular iodine mouthrinses in the treatment and prevention of periodontal diseases.

Advances in novel therapeutic approaches for periodontal diseases

Periodontal diseases are pathological processes resulting from infections and inflammation affecting the periodontium or the tissue surrounding and supporting the teeth. Pathogenic bacteria living in complex biofilms initiate and perpetuate this disease in susceptible hosts. In some cases, broad-spectrum antibiotic therapy has been a treatment of choice to control bacterial infection. However, increasing antibiotic resistance among periodontal pathogens has become a significant challenge when treating periodontal diseases. Thanks to the improved understanding of the pathogenesis of periodontal disease, which involves the host immune response, and the importance of the human microbiome, the primary goal of periodontal therapy has shifted, in recent years, to the restoration of homeostasis in oral microbiota and its harmonious balance with the host periodontal tissues. This shift in therapeutic goals and the drug resistance challenge call for alternative approaches to antibiotic therapy that indiscriminately eliminate harmful or beneficial bacteria. In this review, we summarize the recent advancement of alternative methods and new compounds that offer promising potential for the treatment and prevention of periodontal disease. Agents that target biofilm formation, bacterial quorum-sensing systems and other virulence factors have been reviewed. New and exciting microbiome approaches, such as oral microbiota replacement therapy and probiotic therapy for periodontal disease, are also discussed.

Development and characterization of an oral microbiome transplant among Australians for the treatment of dental caries and periodontal disease: A study protocol

BACKGROUND

Oral microbiome transplantation (OMT) is a novel concept of introducing health-associated oral microbiota into the oral cavity of a diseased patient. The premise is to reverse the state of oral dysbiosis, and restore the ecological balance to maintain a stable homeostasis with the host immune system. This study will assess the effectiveness, feasibility, and safety of OMT using an interdisciplinary approach.

METHODS/DESIGN

To find donors suitable for microbial transplantation, supragingival plaque samples will be collected from 600 healthy participants. Each sample (200μL) will subsequently be examined in two ways: 1) 100μL of the sample will undergo high-throughput 16S rRNA gene amplicon sequencing and shotgun sequencing to identify the composition and characterisation of a healthy supragingival microbiome, 2) the remaining 100μL of the plaque sample will be mixed with 25% artificial saliva medium and inoculated into a specialised in-vitro flow cell model containing a hydroxyapatite disk. To obtain sufficient donor plaque, the samples would be grown for 14 days and further analysed microscopically and sequenced to examine and confirm the growth and survival of the microbiota. Samples with the healthiest microbiota would then be incorporated in a hydrogel delivery vehicle to enable transplantation of the donor oral microbiota. The third step would be to test the effectiveness of OMT in caries and periodontitis animal models for efficacy and safety for the treatment of oral diseases.

DISCUSSION

If OMTs are found to be successful, it can form a new treatment method for common oral diseases such as dental caries and periodontitis. OMTs may have the potential to modulate the oral microbiota and shift the ecological imbalances to a healthier state.

The forgotten oral microbial transplantation for improving the outcomes of COVID-19

Ever since the uncovering of the severe discrepancy of COVID-19 manifestations, irrespective of viral load, scientists have raced to locate and manage factors contributing to the genesis of a critical state. Recent evidence delineates the role of oral dysbiosis in the development of low-grade inflammation, characterized by the increase of inflammatory cytokines common to those fundamental to the development of severe COVID. Furthermore, high periodontopathic bacteria were recorded in severe acute respiratory syndrome in COVID patients, as well as its common provoking comorbidities such as diabetes and hypertension. This can be explained by the immigration and elimination of oral bacteria into the airways, which, in the context of an injured lung, allows for their preferential overgrowth familiar to that, causing the progression to advanced lung diseases. This is why we indicate the promising usage of oral microbiome transplantation as a treatment of oral microbial dysbiosis, not only associated with the worst outcomes of COVID-19 but also in other disorders of low-grade inflammation.

Oral Microbiota Transplant in Dogs with Naturally Occurring Periodontitis

In periodontitis patients, dysbiosis of the oral microbiota is not only found at clinically diseased periodontal sites but also at clinically healthy periodontal sites, buccal mucosae, tongue, and saliva. The present study evaluated the safety and efficacy of an oral microbiota transplant (OMT) for the treatment of periodontitis in dogs. Eighteen systemically healthy beagle dogs with naturally occurring periodontitis were enrolled in the study and randomly assigned to a test or control group. A 4-y-old, periodontally healthy female beagle dog served as a universal OMT donor. To reduce periodontal inflammation, all dogs received full-mouth mechanical debridement of teeth and mucosae 2 wk before baseline. At baseline, full-mouth mechanical debridement was repeated and followed by adjunctive subgingival and oral irrigation with 0.1% NaOCl. Subsequently, test dogs were inoculated with an OMT from the healthy donor. No daily oral hygiene was performed after OMT transplantation. Adverse events were assessed throughout the observation period. Clinical examinations were performed and whole-mouth oral microbiota samples were collected at week 2, baseline, week 2, and week 12. The composition of oral microbiota samples was analyzed using high-throughput 16S ribosomal RNA gene amplicon sequencing followed by taxonomic assignment and downstream bioinformatic and statistical analyses. Results demonstrated that the intergroup difference in the primary outcome measure, probing pocket depth at week 12, was statistically insignificant. However, the single adjunctive OMT had an additional effect on the oral microbiota composition compared to the full-mouth mechanical and antimicrobial debridement alone. The OMT resulted in an "ecological shift" toward the composition of the donor microbiota, but this was transient in nature and was not observed at week 12. No local or systemic adverse events were observed throughout the study period. The results indicate that OMT may modulate the microbiota composition in dogs with naturally occurring periodontitis and can be applied safely.

Association Between Serum Thyroid-Stimulating Hormone Levels and Salivary Microbiome Shifts

High serum thyroid-stimulating hormone (TSH) levels are linked to many metabolic disorders, but the effects of TSH levels on the oral microbiota are still largely unknown. This study aimed to explore the association between the salivary microbiome in adults and serum TSH levels. Saliva and fasting blood samples were obtained from a health census conducted in Southeast China. All participants were divided according to serum TSH levels. The microbial genetic profiles and changes were acquired by 16S rDNA sequencing and bioinformatics analysis. Relevant anthropometric and biochemical measurements such as insulin resistance, blood lipids, and body composition were evaluated with laboratory tests and physical examinations. The salivary microbiome in individuals with higher TSH level showed significantly higher taxa diversity. Principal coordinates analysis and partial least squares discriminant analysis showed distinct clustering in the Abnormal and Normal Groups (Adonis, P=0.0320). Granulicatella was identified as a discriminative genus for comparison of the two groups. Fasting serum insulin, Homeostatic Model Assessment for Insulin Resistance, and hemoglobin A1 were elevated in the Abnormal Group (P<0.05), showing the presence of insulin resistance in individuals with abnormal higher serum TSH levels. Distance-based redundancy analysis revealed the association of this distinctive difference with salivary microbiome. In conclusion, shifts in microbial profile were observed in the saliva of individuals with different serum TSH levels, and insulin resistance may play an important role in the biochemical and microbial alteration.

Did Omics change periodontal therapy?

The starting point for defining effective treatment protocols is a clear understanding of the etiology and pathogenesis of a condition. In periodontal diseases, this understanding has been hindered by a number of factors, such as the difficulty in differentiating primary pathogens from nonpathogens in complex biofilm structures. The introduction of DNA sequencing technologies, including taxonomic and functional analyses, has allowed the oral microbiome to be investigated in much greater breadth and depth. This article aims to compile the results of studies, using next-generation sequencing techniques to evaluate the periodontal microbiome, in an attempt to determine how far the knowledge provided by these studies has brought us in terms of influencing the way we treat periodontitis. The taxonomic data provided, to date, by published association and elimination studies using next-generation sequencing confirm previous knowledge on the role of classic periodontal pathogens in the pathobiology of disease and include new species/genera. Conversely, species and genera already considered as host-compatible and others less explored were associated with periodontal health as their levels were elevated in healthy individuals and increased after therapy. Functional and transcriptomic analyses also demonstrated that periodontal biofilms are taxonomically diverse, functionally congruent, and highly cooperative. Very few interventional studies to date have examined the effects of treatment on the periodontal microbiome, and such studies are heterogeneous in terms of design, sample size, sampling method, treatment provided, and duration of follow-up. Hence, it is still difficult to draw meaningful conclusions from them. Thus, although OMICS knowledge has not yet changed the way we treat patients in daily practice, the information provided by these studies opens new avenues for future research in this field. As new pathogens and beneficial species become identified, future randomized clinical trials could monitor these species/genera more comprehensively. In addition, the metatranscriptomic data, although still embryonic, suggest that the interplay between the host and the oral microbiome may be our best opportunity to implement personalized periodontal treatments. Therapeutic schemes targeting particular bacterial protein products in subjects with specific genetic profiles, for example, may be the futuristic view of enhanced periodontal therapy.

The role of the oral microbiota in chronic non-communicable disease and its relevance to the Indigenous health gap in Australia

BACKGROUND

Aboriginal Australians and Torres Strait Islanders (hereafter respectfully referred to as Indigenous Australians) experience disproportionately poor health and low life expectancy compared to non-Indigenous Australians. Poor oral health is a critical, but understudied, contributor to this health gap. A considerable body of evidence links poor oral health to increased risks of other chronic non-communicable conditions, such as diabetes, cardiovascular disease, chronic kidney disease, and poor emotional wellbeing.  MAIN: The oral microbiota is indisputably associated with several oral diseases that disproportionately affect Indigenous Australians. Furthermore, a growing literature suggests direct and indirect links between the oral microbiota and systemic chronic non-communicable diseases that underpin much of the Indigenous health gap in Australia. Recent research indicates that oral microbial communities are shaped by a combination of cultural and lifestyle factors and are inherited from caregivers to children. Systematic differences in oral microbiota diversity and composition have been identified between Indigenous and non-Indigenous individuals in Australia and elsewhere, suggesting that microbiota-related diseases may be distinct in Indigenous Australians.  CONCLUSION: Oral microbiota research involving Indigenous Australians is a promising new area that could benefit Indigenous communities in numerous ways. These potential benefits include: (1) ensuring equity and access for Indigenous Australians in microbiota-related therapies; (2) opportunities for knowledge-sharing and collaborative research between scientists and Indigenous communities; and (3) using knowledge about the oral microbiota and chronic disease to help close the gaps in Indigenous oral and systemic health.

Dental black plaque: metagenomic characterization and comparative analysis with white-plaque

Extrinsic black dental staining is an external dental discoloration of bacterial origin, considered a special form of dental plaque. Currently, there is no definitive therapeutic option for eliminating black stain. This study employed 16S rRNA metagenomics to analyze black stain and white-plaque samples from 27 adult volunteers. Study objectives were to: describe the microbial diversity of adult black stain samples; characterize their taxonomic profile; compare the microbiomes of black stain versus white-plaque from adult volunteers and propose a functional map of the black stain microbiome using PICRUSt2. The black stain microbiome was poorer in species diversity as compared to white-plaque. The five most abundant genera in black stain were Capnocytophaga, Leptotrichia, Fusobacterium, Corynebacterium and Streptococcus. Functional analysis of microbial species revealed conserved and consistent clustering of functional pathways within and between black stain and white-plaque microbiomes. We describe enrichment of heme biosynthetic pathways in black stain. Our results suggest that the dysbiosis in black stain resembles "orally healthy" communities. The increased abundance of heme biosynthetic pathways suggests that heme-dependent iron sequestration and subsequent metabolism are key for black stain formation. Further research should decipher the regulation of heme biosynthetic genes and characterize the temporal sequence leading to colonization and dysbiosis.

Metagenomic Assessment of Different Interventions for Treatment of Chronic Periodontitis: A Systematic Review and Meta-Analysis

Background:

Chronic periodontitis is attributed to oral microbial imbalance and host inflammatory reaction.

Objective:

Our review addresses the question of: Are the available interventions able to regain oral microbial balance in patients having chronic periodontitis?

Data Sources:

We performed a comprehensive systematic search of MEDLine via Pubmed, Cochrane CENTRAL, Clinicalkey, Clarivate Analytics, Springer materials, Wiley, SAGE, Elsevier, Taylor & Francis group, and Wolter Kluwer, together with hand searching and searching the grey literature.

Eligibility Criteria:

We included interventional studies testing the microbiome analysis using metagenomic techniques as an outcome to any intervention for chronic periodontitis.

Study Appraisal and Synthesis Methods:

All studies were imported in Mendeley. The risk of bias was assessed using the specific tool for each study design. The results were analysed using RevMan. All the review steps were performed in duplicates.

Results:

The search yielded 2700 records. After exclusion steps, 10 records were found eligible. We included 5 RCTs, 1 non-RCT, 3 before-and-after studies, and 1 ongoing study. The studies tested non-surgical periodontal treatment with and without antibiotic coverage, probiotics, sodium hypochlorite rinse, and different toothpaste ingredients. One RCT tested the use of enamel matrix derivatives in cases with furcation involvement.

Limitations:

The eligible available studies were small in number. Also, the risk of bias and lack of a standardized protocol impaired the ability to pool all the results.

Conclusions:

The body of the available evidence is not sufficient, and future studies are recommended to better evaluate the effect of periodontal treatments on the periodontal microbiome.

Oral microbiota and Alzheimer's disease: Do all roads lead to Rome?

Alzheimer's disease (AD) is a progressive neurodegenerative pathology affecting milions of people worldwide associated with deposition of senile plaques. While the genetic and environmental risk factors associated with the onset and consolidation of late onset AD are heterogeneous and sporadic, growing evidence also suggests a potential link between some infectious diseases caused by oral microbiota and AD. Oral microbiota dysbiosis is purported to contribute either directly to amyloid protein production, or indirectly to neuroinflammation, occurring as a consequence of bacterial invasion. Over the last decade, the development of Human Oral Microbiome database (HOMD) has deepened our understanding of oral microbes and their different roles during the human lifetime. Oral pathogens mostly cause caries, periodontal disease, and edentulism in aged population, and, in particular, alterations of the oral microbiota causing chronic periodontal disease have been associated with the risk of AD. Here we describe how different alterations of the oral microbiota may be linked to AD, highlighting the importance of a good oral hygiene for the prevention of oral microbiota dysbiosis.

Bayesian hierarchical negative binomial models for multivariable analyses with applications to human microbiome count data

The analyses of large volumes of metagenomic data extracted from aggregate populations of microscopic organisms residing on and in the human body are advancing contemporary understandings of the integrated participation of microbes in human health and disease. Next generation sequencing technology facilitates said analyses in terms of diversity, community composition, and differential abundance by filtering and binning microbial 16S rRNA genes extracted from human tissues into operational taxonomic units. However, current statistical tools restrict study designs to investigations of limited numbers of host characteristics mediated by limited numbers of samples potentially yielding a loss of relevant information. This paper presents a Bayesian hierarchical negative binomial model as an efficient technique capable of compensating for multivariable sets including tens or hundreds of host characteristics as covariates further expanding analyses of human microbiome count data. Simulation studies reveal that the Bayesian hierarchical negative binomial model provides a desirable strategy by often outperforming three competing negative binomial model in terms of type I error while simultaneously maintaining consistent power. An application of the Bayesian hierarchical negative binomial model using subsets of the open data published by the American Gut Project demonstrates an ability to identify operational taxonomic units significantly differentiable among persons diagnosed by a medical professional with either inflammatory bowel disease or irritable bowel syndrome that are consistent with contemporary gastrointestinal literature.

Microbiological dynamics of red complex bacteria following full-mouth air polishing in periodontally healthy subjects-a randomized clinical pilot study

OBJECTIVES

Suppression of periodontal pathogens in the oral cavity of periodontally healthy individuals may lower the risk for periodontal or periimplant diseases. Therefore, the present study aimed to analyze the effect of supragingival debridement (SD) with adjunctive full mouth glycine powder air polishing (FM-GPAP) on the prevalence of periodontal pathogens in periodontally healthy individuals.

MATERIALS AND METHODS

Eighty-seven systemically and periodontally healthy intraoral carriers of red complex bacteria, i.e., Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola or other periodontal pathogens including Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Eikenella corrodens were enrolled into the study and randomly assigned to receive SD with adjunctive FM-GPAP (test, n = 42) or SD alone (control, n = 45). In the first observation period, microbiological samples were obtained prior to, and 2, 5, and 9 days following intervention. If one of these periodontal pathogens could still not be identified, additional microbial sampling was performed after 6 and 12 weeks.

RESULTS

The prevalence of red complex bacteria was significantly reduced in the test compared to the control group following treatment (p = 0.004) and at day 9 (p = 0.031). Intragroup comparison showed a significant (test, p < 0.001; control, p ≤ 0.01) reduction in the mean prevalence in both groups from BL through day 9 with an additional significant intergroup difference (p = 0.048) at day 9. However, the initial strong reduction returned to baseline values after 6 and 12 weeks.

CONCLUSION

In periodontally healthy carriers of periodontal pathogens, FM-GPAP as an adjunct to SD transiently enhances the suppression of red complex bacteria.

CLINICAL RELEVANCE

Whether the enhanced suppression of red complex bacteria by adjunctive FM-GPAP prevents the development of periodontitis in periodontally healthy carriers requires further investigations.

Oral Dysbiosis in Pancreatic Cancer and Liver Cirrhosis: A Review of the Literature

The human body is naturally colonized by a huge number of different commensal microbial species, in a relatively stable equilibrium. When this microbial community undergoes dysbiosis at any part of the body, it interacts with the innate immune system and results in a poor health status, locally or systemically. Research studies show that bacteria are capable of significantly influencing specific cells of the immune system, resulting in many diseases, including a neoplastic response. Amongst the multiple different types of diseases, pancreatic cancer and liver cirrhosis were significantly considered in this paper, as they are major fatal diseases. Recently, these two diseases were shown to be associated with increased or decreased numbers of certain oral bacterial species. These findings open the way for a broader perception and more specific investigative studies, to better understand the possible future treatment and prevention. This review aims to describe the correlation between oral dysbiosis and both pancreatic cancer and liver cirrhotic diseases, as well as demonstrating the possible diagnostic and treatment modalities, relying on the oral microbiota, itself, as prospective, simple, applicable non-invasive approaches to patients, by focusing on the state of the art. PubMed was electronically searched, using the following key words: "oral microbiota" and "pancreatic cancer" (PC), "liver cirrhosis", "systemic involvement", and "inflammatory mediators". Oral dysbiosis is a common problem related to poor oral or systemic health conditions. Oral pathogens can disseminate to distant body organs via the local, oral blood circulation, or pass through the gastrointestinal tract and enter into the systemic circulation. Once oral pathogens reach an organ, they modify the immune response and stimulate the release of the inflammatory mediators, this results in a disease. Recent studies have reported a correlation between oral dysbiosis and the increased risk of pancreatic and liver diseases and provided evidence of the presence of oral pathogens in diseased organs. The profound impact that microbial communities have on human health, provides a wide domain towards precisely investigating and clearly understanding the mechanism of many diseases, including cancer. Oral microbiota is an essential contributor to health status and imbalance in this community was correlated to oral and systemic diseases. The presence of elevated numbers of certain oral bacteria, particularly P. gingivalis, as well as elevated levels of blood serum antibodies, against this bacterial species, was associated with a higher risk of pancreatic cancer and liver cirrhosis incidence. Attempts are increasingly directed towards investigating the composition of oral microbiome as a simple diagnostic approach in multiple diseases, including pancreatic and liver pathosis. Moreover, treatment efforts are concerned in the recruitment of microbiota, for remedial purposes of the aforementioned and other different diseases. Further investigation is required to confirm and clarify the role of oral microbiota in enhancing pancreatic and liver diseases. Improving the treatment modalities requires an exertion of more effort, especially, concerning the microbiome engineering and oral microbiota transplantation.

Oral microbiomes: more and more importance in oral cavity and whole body

Microbes appear in every corner of human life, and microbes affect every aspect of human life. The human oral cavity contains a number of different habitats. Synergy and interaction of variable oral microorganisms help human body against invasion of undesirable stimulation outside. However, imbalance of microbial flora contributes to oral diseases and systemic diseases. Oral microbiomes play an important role in the human microbial community and human health. The use of recently developed molecular methods has greatly expanded our knowledge of the composition and function of the oral microbiome in health and disease. Studies in oral microbiomes and their interactions with microbiomes in variable body sites and variable health condition are critical in our cognition of our body and how to make effect on human health improvement.

Ecological Therapeutic Opportunities for Oral Diseases

The three main oral diseases of humans, that is, caries, periodontal diseases, and oral candidiasis, are associated with microbiome shifts initiated by changes in the oral environment and/or decreased effectiveness of mucosal immune surveillance. In this review, we discuss the role that microbial-based therapies may have in the control of these conditions. Most investigations on the use of microorganisms for management of oral disease have been conducted with probiotic strains with some positive but very discrete clinical outcomes. Other strategies such as whole oral microbiome transplantation or modification of community function by enrichment with health-promoting indigenous oral strains may offer more promise, but research in this field is still in its infancy. Any microbial-based therapeutics for oral conditions, however, are likely to be only one component within a holistic preventive strategy that should also aim at modification of the environmental influences responsible for the initiation and perpetuation of microbiome shifts associated with oral dysbiosis.

Amplicon Sequencing Reveals Microbiological Signatures in Spent Nuclear Fuel Storage Basins

Water quality is an important determinant for the structural integrity of alloy cladded fuels and assemblies during long-term wet storage. Detailed characterization of a water filled storage basin for spent nuclear reactor fuel was performed following the formation and proliferation of an amorphous white flocculent. White precipitant was sampled throughout the storage basin for chemical and spectroscopic characterization, and environmental DNA was extracted for 454 pyrosequencing of bacterial 16S rRNA gene diversity. Accordingly, spectroscopic analyses indicated the precipitant to be primarily amorphous to crystalline aluminum (oxy) hydroxides with minor associated elemental components including Fe, Si, Ti, and U. High levels of organic carbon were co-localized with the precipitant relative to bulk dissolved organic concentrations. Bacterial densities were highly variable between sampling locations and with depth within the water filled storage basin; cell numbers ranged from 4 × 10³to 4 × 10⁴ cells/mL. Bacterial diversity that was physically associated with the aluminum (oxy) hydroxide complexes exceeded an estimated 4,000 OTUs/amplicon library (3% cutoff) and the majority of sequences were aligned to the families Burkholderiaceae (23%), Nitrospiraceae (23%), Hyphomicrobiaceae (17%), and Comamonadaceae (6%). We surmise that episodic changes in the physical and chemical properties of the basin contribute to the polymerization of aluminum (oxy) hydroxides, which in turn can chemisorb nutrients, carbon ligands and bacterial cells from the surrounding bulk aqueous phase. As such, these precipitants should establish favorable microhabitats for bacterial colonization and growth. Comparative analyses of 16S rRNA gene amplicon libraries across a selection of natural and engineered aquatic ecosystems were performed and microbial community and taxonomic signatures unique to the spent nuclear fuel (SNF) storage basin environment were revealed. These insights could spur the development of tractable bio-indicators that are specific of and diagnostic for water quality at discrete locations and finer scales of resolution, marking an important contribution for improved water quality and management of SNF storage facilities.

Use of Probiotics and Oral Health

PURPOSE OF REVIEW

The purpose of this study is to critically assess recent studies concerning the use of probiotics to control periodontal diseases, dental caries and halitosis (oral malodour).

RECENT FINDINGS

Clinical studies have shown that probiotics when allied to conventional periodontal treatment can ameliorate microbial dysbiosis and produce significant improvement in clinical indicators of disease. However, this effect is often not maintained by the host after the end of probiotic use. Current probiotics also show limited effects in treating caries and halitosis. Novel approaches based up on replacement therapy and using highly abundant health-associated oral species, including nitrate-reducing bacteria, have been proposed to improve persistence of probiotic strains and maintain oral health benefits.

SUMMARY

Probiotics have potential in the management of multifactorial diseases such as the periodontal diseases and caries, by more effectively addressing the host-microbial interface to restore homeostasis that may not be achieved with conventional treatments.

Oral microbiota transplant: a potential new therapy for oral diseases

Dental caries and periodontitis are amongst the most common diseases affecting humans worldwide. There is an evolving trend for dental and medical research to share knowledge on the etiology and promising therapies for human diseases. Inspired by the success of fecal microbiota transplant to manage gastro-intestinal disordes, oral microbiome transplant has been proposed but not yet tested in humans. This article critically reviews the potential of oral microbiome transplant for managing oral diseases.

Effect of erythritol on microbial ecology of in vitro gingivitis biofilms

Gingivitis is one of the most common oral infections in humans. While sugar alcohols such as erythritol are suggested to have caries-preventive properties, it may also have beneficial effects in prevention of gingivitis by preventing maturation of oral biofilms. The aim of this study was to assess the effect of erythritol on the microbial ecology and the gingivitis phenotype of oral microcosms. Biofilms were inoculated with stimulated saliva from 20 healthy donors and grown in a gingivitis model in the continuous presence of 0 (control group), 5, and 10% erythritol. After 9 days of growth, biofilm formation, protease activity (gingivitis phenotype), and microbial profile analyses were performed. Biofilm growth was significantly reduced in the presence of erythritol, and this effect was dose dependent. Protease activity and the Shannon diversity index of the microbial profiles of the biofilms were significantly lower when erythritol was present. Microbial profile analysis revealed that presence of erythritol induced a compositional shift from periodontitis- and gingivitis-related taxa toward early colonizers. The results of this study suggest that erythritol suppresses maturation of the biofilms toward unhealthy composition. The gingivitis phenotype was suppressed and biofilm formation was reduced in the presence of erythritol. Therefore, it is concluded that erythritol may contribute to a healthy oral ecosystem in vitro.

Red fluorescence of dental plaque in children -A cross-sectional study

OBJECTIVES

The relation between the presence of red fluorescent plaque and the caries status in children was studied. In addition, the microbial composition of dental plaque from sites with red fluorescent plaque (RFP) and from sites with no red fluorescent plaque (NFP) was assessed.

METHODS

Fluorescence photographs were taken from fifty children (6-14 years old) with overnight plaque. Full-mouth caries scores (ICDAS II) were obtained. The composition of a saliva sample and two plaque samples (RFP and NFP) was assessed using 16S rDNA sequencing.

RESULTS

At the site level, no clinically relevant correlations were found between the presence of RFP and the caries status. At the subject level, a weak correlation was found between RFP and the caries status when non-cavitated lesions were included (r_s=0.37, p=0.007). The microbial composition of RFP differed significantly from NFP. RFP had more anaerobes and more Gram-negative bacterial taxa. The most discriminative operational taxonomic units (OTUs) for RFP were Corynebacterium, Leptotrichia, Porphyromonas and Selenomonas, while the most discriminative OTUs for NFP were Neisseria, Actinomyces, Streptococcus and Rothia.

CONCLUSIONS

There were no clinical relevant correlations in this cross-sectional study between the presence of RFP and (early) caries lesions. There were differences in the composition of these phenotypically different plaque samples: RFP contained more Gram-negative, anaerobic taxa and was more diverse than NFP.

CLINICAL SIGNIFICANCE

The study outcomes provide more insight in the possibilities to use plaque fluorescence in oral health risk assessments.

Datasets used to discover the microbial signatures of oral dysbiosis, periodontitis and edentulism in humans

This article provides supporting data for the research article ‘Microbial Signatures of Oral Dysbiosis, Periodontitis and Edentulism Revealed by Gene Meter Methodology’ (M.C. Hunter, A.E. Pozhitkov, P.A. Noble, 2016) [1]. In that article, we determined the microbial abundance signatures for patient with periodontics, edentulism, or health using Gene Meter Technology. Here we provide the data used to make the DNA microarray and the resulting microbial abundance data that was determined using the calibrated probes and the 16S rRNA genes harvested from patients. The first data matrix contains two columns: one is the GenInfo Identifier (GI) numbers of the 16S rRNA gene sequences and the other is the corresponding oral bacterial taxonomy. The probes were then screened for redundancy and if they were found to be unique, they were synthesized onto the surface of the DNA microarrays. The second data matrix consists of the abundances of the 576 16S rRNA genes that was determined using the median value of all individual calibrated probes targeting each gene. The data matrix consists of 16 columns and 576 rows, with the columns representing the 16 patients and the rows representing 576 different oral microorganisms. The third data matrix consists of the abundances of 567 16S rRNA genes determined using the calibrated abundance of all aggregated probes targeting the same 16S rRNA gene. The data matrix of the aggregated probes consists of 16 samples and 567 rows.

Microbial signatures of oral dysbiosis, periodontitis and edentulism revealed by Gene Meter methodology

Conceptual models suggest that certain microorganisms (e.g., the "red" complex) are indicative of a specific disease state (e.g., periodontitis); however, recent studies have questioned the validity of these models. Here, the abundances of 500+ microbial species were determined in 16 patients with clinical signs of one of the following oral conditions: periodontitis, established caries, edentulism, and oral health. Our goal was to determine if the abundances of certain microorganisms reflect dysbiosis or a specific clinical condition that could be used as a 'signature' for dental research. Microbial abundances were determined by the analysis of 138,718 calibrated probes using Gene Meter methodology. Each 16S rRNA gene was targeted by an average of 194 unique probes (n=25nt). The calibration involved diluting pooled gene target samples, hybridizing each dilution to a DNA microarray, and fitting the probe intensities to adsorption models. The fit of the model to the experimental data was used to assess individual and aggregate probe behavior; good fits (R²>0.90) were retained for back-calculating microbial abundances from patient samples. The abundance of a gene was determined from the median of all calibrated individual probes or from the calibrated abundance of all aggregated probes. With the exception of genes with low abundances (<2 arbitrary units), the abundances determined by the different calibrations were highly correlated (r~1.0). Seventeen genera were classified as 'signatures of dysbiosis' because they had significantly higher abundances in patients with periodontitis and edentulism when contrasted with health. Similarly, 13 genera were classified as 'signatures of periodontitis', and 14 genera were classified as 'signatures of edentulism'. The signatures could be used, individually or in combination, to assess the clinical status of a patient (e.g., evaluating treatments such as antibiotic therapies). Comparisons of the same patient samples revealed high false negatives (45%) for next-generation-sequencing results and low false positives (7%) for Gene Meter results.

The Oral Microbiome in Health and Its Implication in Oral and Systemic Diseases

The oral microbiome can alter the balance between health and disease, locally and systemically. Within the oral cavity, bacteria, archaea, fungi, protozoa, and viruses may all be found, each having a particular role, but strongly interacting with each other and with the host, in sickness or in health. A description on how colonization occurs and how the oral microbiome dynamically evolves throughout the host's life is given. In this chapter the authors also address oral and nonoral conditions in which oral microorganisms may play a role in the etiology and progression, presenting the up-to-date knowledge on oral dysbiosis as well as the known underlying pathophysiologic mechanisms involving oral microorganisms in each condition. In oral pathology, oral microorganisms are associated with several diseases, namely dental caries, periodontal diseases, endodontic infections, and also oral cancer. In systemic diseases, nonoral infections, adverse pregnancy outcomes, cardiovascular diseases, and diabetes are among the most prevalent pathologies linked with oral cavity microorganisms. The knowledge on how colonization occurs, how oral microbiome coevolves with the host, and how oral microorganisms interact with each other may be a key factor to understand diseases etiology and progression.

Polymicrobial Biofilm Studies: From Basic Science to Biofilm Control

Microbes rarely exist as single species planktonic forms as they have been commonly studied in the laboratory. Instead, the vast majority exists as part of complex polymicrobial biofilm communities attached to host and environmental surfaces. The oral cavity represents one of the most diverse and well-studied polymicrobial consortia. Despite a burgeoning field of mechanistic biofilm research within the past decades, our understanding of interactions that occur between microbial members within oral biofilms is still limited. Thus, the primary objective of this review is to focus on polymicrobial biofilm formation, microbial interactions and signaling events that mediate oral biofilm development, consequences of oral hygiene on both local and systemic disease, and potential therapeutic strategies to limit oral dysbiosis.