Periodontal microbial complexes associated with specific cell and tissue responses

Biochemical and Microbiological Aspects of the Oral Cavity of Children and Young People with Neurological Impairment and Oropharyngeal Dysphagia

The components and the salivary flow have a direct influence on the composition of the oral microbiota of children and young people with oropharyngeal dysphagia, and studies have already demonstrated the excessive accumulation of supragingival dental calculus in individuals with enteral nutrition. This study aimed to compare the oral hygiene, biochemical, and microbiological aspects of the oral cavity of children and young people with neurological impairment and oropharyngeal dysphagia. Forty children and young people with neurological impairment and oropharyngeal dysphagia were enrolled and divided into two groups: group I, encompassing 20 participants fed via gastrostomy; and group II, encompassing 20 participants fed via the oral route. Oral hygiene and salivary pH and flow were assessed, and a polymerase chain reaction was performed to evaluate the messenger RNA expressions of Porphyromonas gingivalis, Tanerella forsythia, and Treponema denticola. In groups I and II, the mean Oral Hygiene Index-Simplified scores were 4 and 2, respectively, showing a significant difference; the mean Calculus Index scores were 2 and 0, respectively, showing a significant difference; and the mean pH was 7.5 and 6.0, respectively, showing a significant difference. Bacterial analysis indicated no association between the two groups. It can be concluded that children and young people who use gastrostomy had a poorer oral hygiene, greater dental calculus deposition, and higher salivary pH. The saliva of patients in both groups contained Porphyromonas gingivalis, Tanerella forsythia, and Treponema denticola.

Dysbiotic changes of periodontal pathogens in patients wearing conventional and self-ligating orthodontic appliances

Objective: This study aimed to analyse dysbiotic changes of periodontal pathogenic bacteria and their relationship with different types of fixed orthodontic appliances in a population located in Northwestern Mexico.

Methods: Three groups of patients were identified: a control group without orthodontic appliances (C), a conventional-ligating appliance group (CLA), and a self-ligating appliance group (SLA). Periodontal biofilm samples were collected for DNA extraction to identify the presence and load of Treponema denticola, Prevotella intermedia, and Fusobacterium nucleatum, using a quantitative real-time PCR technique.

Results: A total of 92 patients were included. The results showed that F. nucleatum was present in all groups including the control patients (C 96%, CLA 100%, and SLA 67%, respectively). Female participants displayed a higher frequency of periodontal pathogens than males, but males were more affected by F. nucleatum. In addition, the presence of T. denticola and P. intermedia was time-dependent, being more frequent in patients in treatment for longer than 12 months whereas CLA showed 74% and 78% of positive samples and SLA showed 78% and 89%, respectively. F. nucleatum was present in 100% of CLA samples before and after 12 months of treatment and its load was higher in the SLA group after 12 months.

Conclusions: Dysbiotic changes that could affect the periodontal tissues were seen in patients wearing orthodontic appliances. The frequency of F. nucleatum was significantly higher in CLA and noted with a greater load in SLA. In addition, female participants showed a higher frequency of periodontal pathogens while male subjects were more affected by F. nucleatum. As expected, treatment for longer than 12 months correlated with a higher frequency of all periodontal pathogens. The results support the concept that dysbiosis leading to periodontal disease can be caused by the rise of a dominant species, instead of the appearance of a new species.

Genome-Wide Analysis of Periodontal and Peri-implant Cells and Tissues

-Omics analyses, including the systematic cataloging of messenger RNA and microRNA sequences or DNA methylation patterns in a cell population, organ, or tissue sample, are powerful means of generating comprehensive genome-level data sets on complex diseases. We have systematically assessed the transcriptome, microbiome, miRNome, and methylome of gingival and peri-implant tissues from human subjects and further studied the transcriptome of primary cells ex vivo, or in vitro after infection with periodontal pathogens.Our data offer new insight on the pathophysiology underlying periodontal and peri-implant diseases, a possible route to a better and earlier diagnosis of these highly prevalent chronic inflammatory diseases and thus, to a personalized and efficient treatment approach.Herein, we outline the laboratory steps required for the processing of periodontal cells and tissues for -omics analyses using current microarrays or next-generation sequencing technology.

Multiple Brain Abscesses of Odontogenic Origin. May Oral Microbiota Affect Their Development? A Review of the Current Literature

In the last few years, the role of oral microbiota in the setting of oral diseases such as caries, periodontal disease, oral cancer and systemic infections, including rheumatoid arthritis, cardiovascular disease and brain abscess (BA), has attracted the attention of physicians and researchers. Approximately 5–7% of all BAs have an odontogenic origin, representing an important pathological systemic condition with a high morbidity and mortality. A systematic search of two databases (Pubmed and Ovid EMBASE) was performed for studies published up to 5 January 2021, reporting multiple BAs attributed to an odontogenic origin. According to PRISMA guidelines, we included a total of 16 papers reporting multiple BAs due to odontogenic infections. The aim of this review is to investigate the treatment modality and the clinical outcome of patients with multiple BAs due to odontogenic infections, as well as to identify the most common pathogens involved in this pathological status and their role, in the oral microbiota, in the onset of oral infections. A multidisciplinary approach is essential in the management of multiple BAs. Further studies are required to understand better the role of microbiota in the development of multiple BAs.

Efficacy of Probiotics as Adjunctive Therapy to Nonsurgical Treatment of Peri-Implant Mucositis: A Systematic Review and Meta-Analysis

Background: Peri-implant mucositis (PiM) is an inflammation of the soft tissues surrounding the dental implant and is the precursor of the destructive inflammatory peri-implantitis. PiM is usually reversible, but difficult to eradicate. Mechanical debridement (MD) is the conventional procedure to treat PiM although not enough to reach a complete resolution. Recently, probiotics have been considered in the treatment of peri-implant disease. Therefore, the aim of this systematic review and meta-analysis was to investigate the efficacy of the probiotic therapy combined with MD compared with MD alone or MD + placebo in patients with PiM.

Methods: A search using electronic databases (MEDLINE, Science Direct databases, and Cochrane Central Register of Controlled Trials) and a manual search were performed up to November 2019 by two reviewers independently of each other. Eligible randomized controlled trials (RCTs) comparing MD + probiotic vs. MD were included. The quality assessment for all the selected RCTs was conducted according to the Cochrane Handbook for Systematic Reviews of Interventions. Probing depth reduction was selected as the primary outcome. Weighted mean difference (WMD) and 95% confidence interval (CI) were calculated for continuous outcomes, and odds ratio (OR) and 95% CI were calculated for dichotomous outcomes, using random effect models. This review was registered on the PROSPERO database (CRD42020213625).

Results: Five eligible publications were included in this systematic review and four in the meta-analysis. As regards the implant, the WMD in the probing depth reduction between the test and control group was −0.12 mm [95% CI (−0.38, 0.14), p = 0.38], meaning that the adjunctive probiotic therapy was not improving PiM compared with MD alone or MD + placebo. The meta-analysis also showed no statistically significant results in the secondary outcomes (reduction of full mouth plaque index and full mouth bleeding on probing, absence of bleeding on probing at implant level, and changes in microorganism load and species).

Conclusion: The findings of this systematic review and meta-analysis suggested that the additional use of probiotics did not improve the efficacy of MD in PiM treatment regarding clinical and microbial outcomes, at least in a short-term.

Proteome and Microbiome Mapping of Human Gingival Tissue in Health and Disease

Efforts to map gingival tissue proteomes and microbiomes have been hampered by lack of sufficient tissue extraction methods. The pressure cycling technology (PCT) is an emerging platform for reproducible tissue homogenisation and improved sequence retrieval coverage. Therefore, we employed PCT to characterise the proteome and microbiome profiles in healthy and diseased gingival tissue. Healthy and diseased contralateral gingival tissue samples (total n = 10) were collected from five systemically healthy individuals (51.6 ± 4.3 years) with generalised chronic periodontitis. The tissues were then lysed and digested using a Barocycler, proteins were prepared and submitted for mass spectrometric analysis and microbiome DNA for 16S rRNA profiling analysis. Overall, 1,366 human proteins were quantified (false discovery rate 0.22%), of which 69 proteins were differentially expressed (≥2 peptides and p < 0.05, 62 up, 7 down) in periodontally diseased sites, compared to healthy sites. These were primarily extracellular or vesicle-associated proteins, with functions in molecular transport. On the microbiome level, 362 species-level operational taxonomic units were identified. Of those, 14 predominant species accounted for >80% of the total relative abundance, whereas 11 proved to be significantly different between healthy and diseased sites. Among them, Treponema sp. HMT253 and Fusobacterium naviforme and were associated with disease sites and strongly interacted (r > 0.7) with 30 and 6 up-regulated proteins, respectively. Healthy-site associated strains Streptococcus vestibularis, Veillonella dispar, Selenomonas sp. HMT478 and Leptotrichia sp. HMT417 showed strong negative interactions (r < −0.7) with 31, 21, 9, and 18 up-regulated proteins, respectively. In contrast the down-regulated proteins did not show strong interactions with the regulated bacteria. The present study identified the proteomic and intra-tissue microbiome profile of human gingiva by employing a PCT-assisted workflow. This is the first report demonstrating the feasibility to analyse full proteome profiles of gingival tissues in both healthy and disease sites, while deciphering the tissue site-specific microbiome signatures.

Effect of nonsurgical periodontal therapy on haematological parameters in grades B and C periodontitis: an exploratory analysis

Aim

Assessment of the effect of nonsurgical periodontal therapy on haematological parameters in patients with grades B (BP) and C periodontitis (CP).

Methods

Eight BP and 46 CP patients received full-mouth periodontal debridement within 48 h, if positive for Aggregatibacter actinomycetemcomitans with adjunctive systemic antibiotics (4 BP, 17 CP). Clinical data were collected prior and 12 weeks after periodontal therapy. Blood was sampled prior to and 1 day as well as 6 and 12 weeks after the first SD visit. Erythrocyte count, haemoglobin value, haematocrit (HCT), mean erythrocyte volume (MCV), mean corpuscular haemoglobin (MCH), MCH concentration (MCHC), platelets (PLT) and heat shock protein 27 (Hsp27) were assessed.

Results

Both groups showed significant clinical improvement (p < 0.05). Using univariate analysis, MCV was noticeably lower in CP than BP at all examinations, HCT only at baseline. For CP, MCHC was noticeably higher 12 weeks after SD than at baseline and 1 day (p ≤ 0.005) and Hsp27 increased noticeably at 1 day (p < 0.05). Repeated measures analysis of variance revealed African origin to be associated with lower MCV and female sex with lower MCHC.

Conclusion

Based on multivariate analysis, periodontal diagnosis (BP/CP) was not associated with haematological parameters measured in this study or serum Hsp27. In CP, nonsurgical periodontal therapy improved MCHC 12 weeks after SD. Also in CP Hsp27 was increased 1 day after SD.

Oral Microbiome and Gingival Transcriptome Profiles of Ligature-Induced Periodontitis

This investigation evaluated the relationship of the oral microbiome and gingival transcriptome in health and periodontitis in nonhuman primates (Macaca mulatta). Subgingival plaque samples and gingival biopsies were collected from healthy sites and at sites undergoing ligature-induced periodontitis. Microbial samples were analyzed with 16S amplicon sequencing to identify bacterial profiles in young (3 to 7 y) and adult (12 to 23 y) animals. The gingival transcriptome was determined with a microarray analysis and focused on the expression level of 452 genes that are associated with the development of inflammation and innate and adaptive immune responses. Of the 396 total operational taxonomic units (OTUs) identified across the samples, 81.8% were detected in the young group and 99.5% in the adult group. Nevertheless, 58 of the OTUs composed 88% of the signal in adults, and 49 OTUs covered 91% of the OTU readouts in the young group. Correlation analyses between the microbiome members and specific gingival genes showed a high number of significant bacteria-gene correlations in the young healthy tissues, which decreased by 75% in diseased tissues. In contrast, these correlations increased by 2.5-fold in diseased versus healthy tissues of adult animals. Complexes of bacteria were delineated that related to specific sets of immune genes, differing in health and disease and in the young versus adult animals. The correlated gene profiles demonstrated selected pathway overrepresentation related to particular bacterial complexes. These results provide novel insights into microbiome changes with disease and the relationship of these changes to specific gene profiles and likely biologic activities occurring in healthy and diseased gingival tissues in this human-like periodontitis model.

[The effect of probiotics on the secretory immunity of saliva in patients with type 2 diabetes]

To study the effect of the use of probiotics on the state of mucosal immunity in patients with type 2 diabetes. Evaluation of the results was carried out based on immunological parameters of the saliva of 50 patients suffering from type 2 diabetes with moderate periodontitis, before and 1 month after taking a probiotic complex based on Lactobacillus. In the salivary fluid of patients, a decrease in the concentration of pro-inflammatory cytokines IL-1β, TNF-α and IL-8 was noted, while an increase in the anti-inflammatory cytokine IL-10 was observed. An increase in local mucosal immunity was also observed, manifested in an increase in the synthesis of secretory immunoglobulin A.

HLA-B57.01 shields people living with HIV for significantly better periodontal health

BACKGROUND

To assess the association between HLA-B57.01 (Human leukocyte antigen) and clinical parameters of chronic periodontitis in people living with HIV (PLWHIV).

METHODS

All patients were recruited from the HIVCENTER at the University Hospital Frankfurt during April 2014 and July 2015. Periodontal examination included Periodontal Screening Index (PSI), Gingivalindex (GI), Bleeding on Probing Index (BOP), Periodontal Probing Depth (PD), Clinical Attachment Level (CAL) and DMF-T Score (decayed, missing, filled teeth). Associations among periodontitis, HLA-system and additional risk factors in PLWHIV were evaluated in multivariate analyses.

RESULTS

One hundred PLWHIV were enrolled. Forty-five patients were naive, meaning that these patients never took antiretroviral (ARV) drugs before, 55 patients treated with combined antiretroviral therapy (cART). Nineteen patients presented a positive HLA-B 57.01 status. PLWHIV who were carriers of HLA-B 57.01 had significantly lower PSI-scores (Grade 3 or higher; 0/19 [0%] versus 16/41 [39%] versus 17/40 [42%]; p = < 0.001), GI-scores (Grade 2 or higher; 0/19 [0%] versus 19/41 [46%] versus 28/40 [70%]; p = < 0.001) and BOP-Scores (2/19 [1%] versus 38/41 [92%] versus 40/40 [100%]; p = < 0.001) in comparison to naive PLWHIV and PLWHIV receiving cART, who were both not carriers of HLA-B 57.01. A lower value of PSI-, GI- and BOP-Score is associated with improved periodontal health. The adjusted odds ratio (OR) of periodontitis was decreased in patients who were carriers of HLA-B 57.01 by measurement of PSI-Score (OR = 0.006, 95% confidence interval (CI) = 0.001 to 0.026), GI-Score (OR = 0.018, 95% confidence interval (CI) = 0.003 to 0.104) and BOP-Score (OR = 0.003, 95% confidence interval (CI) = < 0.001 to 0.011).

CONCLUSIONS

HLA-B 57.01 is an independent resistance indicator for generalized periodontitis in PLWHIV with respect to established cofactors.

Periodontal diseases and adverse pregnancy outcomes: Is there a role for vitamin D?

Studies have shown a relationship between maternal periodontal diseases (PDs) and premature delivery. PDs are commonly encountered oral diseases which cause progressive damage to the periodontal ligament and alveolar bones, leading to loss of teeth and oral disabilities. PDs also adversely affect general health by worsening of cardiovascular and metabolic diseases. Moreover, maternal PDs are thought to be related to increasing the frequency of preterm-birth with low birth weight (PBLBW) in new-borns. Prematurity and immaturity are the leading causes of prenatal and infant mortality and is a major public health problem around the world. Inflamed periodontal tissues generate significantly high levels of proinflammatory cytokines that may have systemic effects on the host mother and the fetus. In addition, the bacteria that cause PDs produce endotoxins which can harm the fetus. Furthermore, studies have shown that microorganisms causing PDs can get access to the bloodstream, invading uterine tissues, to induce PBLBW. Another likely mechanism that connects PDs with adverse pregnancy outcome is maternal vitamin D status. A role of inadequate vitamin D status in the genesis of PDs has been reported. Administration of vitamin D supplementation during pregnancy could reduce the risk of maternal infections and adverse pregnancy outcomes. As maternal PDs are significant risk factors for adverse pregnancy outcome, preventive antenatal care for pregnant women in collaboration with the obstetric and dental professions are required.

Inflammatory serum markers up to 5 years after comprehensive periodontal therapy of aggressive and chronic periodontitis

Aim

The aim of the study is to assess the long-term effect of active periodontal therapy on serum inflammatory parameters in patients with aggressive (AgP) and chronic (ChP) periodontitis in a non-randomised clinical study.

Methods

Twenty-five ChP and 17 AgP were examined clinically prior to (baseline), 12 weeks and 60 months after subgingival debridement of all pockets within 2 days. Systemic antibiotics were prescribed if Aggregatibacter actinomycetemcomitans was detected (10 AgP, 8 ChP), flap surgery was rendered if required. Neutrophil elastase (NE), C-reactive protein (CRP), lipopolysaccharide binding protein, interleukin 6, 8, and leukocyte counts were assessed at baseline, 12 weeks and 60 months.

Results

Clinical parameters improved significantly in both groups from 12 weeks to 60 months. Eleven AgP and 18 ChP patients received surgical treatment after the 12 weeks examination. Only 3 patients in each group attended ≥ 2 supportive maintenance visits per year. NE and CRP were significantly higher in AgP than ChP at baseline and 60 months (p < 0.01). For leukocyte counts in ChP, significant changes were observed (baseline: 6.11 ± 1.44 nl⁻¹; 12 weeks: 5.34 ± 1.40 nl⁻¹; 60 months: 7.73 ± 2.89 nl⁻¹; p < 0.05). Multiple regression analysis identified African origin, surgical treatment and female sex to correlate with better clinical improvement.

Conclusion

Despite comprehensive periodontal treatment, AgP patients exhibit higher NE and CRP levels than ChP patients up to 5 years after therapy.

Clinical relevance

Systemic inflammatory burden in AgP patients is higher than in ChP patients even 5 years after periodontal treatment.

Electronic supplementary material

The online version of this article (10.1007/s00784-018-2398-x) contains supplementary material, which is available to authorized users.

Oral Biofilms from Symbiotic to Pathogenic Interactions and Associated Disease -Connection of Periodontitis and Rheumatic Arthritis by Peptidylarginine Deiminase

A wide range of bacterial species are harbored in the oral cavity, with the resulting complex network of interactions between the microbiome and host contributing to physiological as well as pathological conditions at both local and systemic levels. Bacterial communities inhabit the oral cavity as primary niches in a symbiotic manner and form dental biofilm in a stepwise process. However, excessive formation of biofilm in combination with a corresponding deregulated immune response leads to intra-oral diseases, such as dental caries, gingivitis, and periodontitis. Moreover, oral commensal bacteria, which are classified as so-called “pathobionts” according to a now widely accepted terminology, were recently shown to be present in extra-oral lesions with distinct bacterial species found to be involved in the onset of various pathophysiological conditions, including cancer, atherosclerosis, chronic infective endocarditis, and rheumatoid arthritis. The present review focuses on oral pathobionts as commensal and healthy members of oral biofilms that can turn into initiators of disease. We will shed light on the processes involved in dental biofilm formation and also provide an overview of the interactions of P. gingivalis, as one of the most prominent oral pathobionts, with host cells, including epithelial cells, phagocytes, and dental stem cells present in dental tissues. Notably, a previously unknown interaction of P. gingivalis bacteria with human stem cells that has impact on human immune response is discussed. In addition to this very specific interaction, the present review summarizes current knowledge regarding the immunomodulatory effect of P. gingivalis and other oral pathobionts, members of the oral microbiome, that pave the way for systemic and chronic diseases, thereby showing a link between periodontitis and rheumatoid arthritis.

A novel peptidic inhibitor derived from Streptococcus cristatus ArcA attenuates virulence potential of Porphyromonas gingivalis

Periodontitis is a global health problem and the 6th most common infectious disease worldwide. Porphyromonas gingivalis is considered a keystone pathogen in the disease and is capable of elevating the virulence potential of the periodontal microbial community. Strategies that interfere with P. gingivalis colonization and expression of virulence factor are therefore attractive approaches for preventing and treating periodontitis. We have previously reported that an 11-mer peptide (SAPP) derived from Streptococcus cristatus arginine deiminase (ArcA) was able to repress the expression and production of several well-known P. gingivalis virulence factors including fimbrial proteins and gingipains. Herein we expand and develop these studies to ascertain the impact of this peptide on phenotypic properties of P. gingivalis related to virulence potential. We found that growth rate was not altered by exposure of P. gingivalis to SAPP, while monospecies and heterotypic biofilm formation, and invasion of oral epithelial cells were inhibited. Additionally, SAPP was able to impinge the ability of P. gingivalis to dysregulate innate immunity by repressing gingipain-associated degradation of interleukin-8 (IL8). Hence, SAPP has characteristics that could be exploited for the manipulation of P. gingivalis levels in oral communities and preventing realization of virulence potential.

Genome-Wide Analysis of Periodontal and Peri-Implant Cells and Tissues

Omics analyses, including the systematic cataloging of messenger RNA and microRNA sequences or DNA methylation patterns in a cell population, organ or tissue sample, are powerful means of generating comprehensive genome-level data sets on complex diseases. We have systematically assessed the transcriptome, miRNome and methylome of gingival tissues from subjects with different diagnostic entities of periodontal disease, and studied the transcriptome of primary cells ex vivo, or in vitro after infection with periodontal pathogens. Our data further our understanding of the pathobiology of periodontal diseases and indicate that the gingival -omes translate into discernible phenotypic characteristics and possibly support an alternative, "molecular" classification of periodontitis.Here, we outline the laboratory steps required for the processing of periodontal cells and tissues for -omics analyses using current microarrays or next-generation sequencing technology.

Microbial complexes levels in conventional and self-ligating brackets

OBJECTIVES

The aims were to evaluate the levels of bacterial species in saliva and in situ and to assess whether the design of brackets influences the risk of developing periodontal disease.

MATERIALS AND METHODS

Twenty patients (13.3 mean age) were bonded with self-ligating brackets and a conventional bracket. Saliva was collected before bonding and 30 and 60 days after bonding. One sample of each bracket was removed 30 and 60 days after bonding. The analysis was determined by checkerboard DNA-DNA hybridization. The data was evaluated by the non-parametric test.

RESULTS

A significant increase in the levels of bacterial species in the saliva occurred in 15 of the 22 analyzed species. The self-ligating brackets presented the highest incidence percentages for the orange and red complexes 60 days after bonding. In situ analyses showed different patterns according to the bracket design. The levels of Campylobacter rectus showed significant differences (p = 0.011) 60 days after bonding among the three brackets; the highest values were observed in the In-Ovation®R bracket.

CONCLUSIONS

The bracket design seems to influence the levels of bacterial species involved in periodontal disease. Considering the wide variety of bacterial species, additional studies are needed to aid in the establishment of effective protocols to prevent the development of periodontal disease during orthodontic treatment.

CLINICAL RELEVANCE

A dynamic alteration in the oral microbiota may lead to inflammatory reactions in the supporting soft and hard tissues. The different types of brackets interfere with bacterial adherence. Bracket design should be considered in orthodontic treatment.

Ethical guidelines, animal profile, various animal models used in periodontal research with alternatives and future perspectives

Laboratory animal models serve as a facilitator to investigate the etiopathogenesis of periodontal disease, are used to know the efficacy of reconstructive and regenerative procedures, and are also helpful in evaluation of newer therapeutic techniques including laser and implant therapies prior to application in the human beings. The aim of this review is to know the different animal models used in various specialties of dental research and to know the ethical guidelines prior to the usage of experimental models with main emphasis on how to refine, replace, and reduce the number of animal models usage in the laboratory. An online search for experimental animal models used in dental research was performed using MEDLINE/PubMed database. Publications from 2009 to May 2013 in the specialty of periodontics were included in writing this review. A total of 652 references were published in PubMed/MEDLINE databases based on the search terms used. Out of 245 studies, 241 were related to the periodontal research published in English from 2009 to 2013. Relevant papers were chosen according to the inclusion and exclusion criteria. After extensive electronic and hand search on animal models, it has been observed that various animal models were used in dental research. Search on animal models used for dental research purpose revealed that various animals such as rats, mice, guinea pigs, rabbit, beagle dogs, goats, and nonhuman primates were extensively used. However, with the new advancement of ex vivo animal models, it has become easy to investigate disease pathogenesis and to test the efficacy of newer therapeutic modalities with the reduced usage of animal models. This review summarized the large amount of literature on animal models used in periodontal research with main emphasis on ethical guidelines and on reducing the animal model usage in future perspective.

Do oral bacteria alter the regenerative potential of stem cells? A concise review

Mesenchymal stem cells (MSCs) are widely recognized as critical players in tissue regeneration. New insights into stem cell biology provide evidence that MSCs may also contribute to host defence and inflammation. In case of tissue injury or inflammatory diseases, e.g. periodontitis, stem cells are mobilized towards the site of damage, thus coming in close proximity to bacteria and bacterial components. Specifically, in the oral cavity, complex ecosystems of commensal bacteria live in a mutually beneficial state with the host. However, the formation of polymicrobial biofilm communities with pathogenic properties may trigger an inadequate host inflammatory-immune response, leading to the disruption of tissue homoeostasis and development of disease. Because of their unique characteristics, MSCs are suggested as crucial regulators of tissue regeneration even under such harsh environmental conditions. The heterogeneous effects of bacteria on MSCs across studies imply the complexity underlying the interactions between stem cells and bacteria. Hence, a better understanding of stem cell behaviour at sites of inflammation appears to be a key strategy in developing new approaches for in situ tissue regeneration. Here, we review the literature on the effects of oral bacteria on cell proliferation, differentiation capacity and immunomodulation of dental-derived MSCs.

Effect of oral administration involving a probiotic strain of Lactobacillus reuteri on pro-inflammatory cytokine response in patients with chronic periodontitis

This study aimed at evaluation of pro-inflammatory cytokine response (TNF-α, IL-1β and IL-17) in patients with chronic periodontitis administered per os with a probiotic strain of Lactobacillus reuteri. In the 38 adult patients with moderate chronic periodontitis, professional cleaning of teeth was performed. Two weeks after performing the oral hygienization procedures, clinical examination permitted to distinguish a group of 24 patients (Group 1) in whom treatment with probiotic tablets containing L. reuteri strain, producing hydrogen peroxide (Prodentis), was conducted. In the remaining 14 patients, no probiotic tablet treatment was applied (the control group; Group 2). From all patients in two terms, gingival crevicular fluid (GCF) was sampled from all periodontal pockets. Estimation of TNF-α, IL-lβ and IL-17 in GCF was performed using the ELISA method. After completion of the therapy with probiotic tablets, 18 (75 %) of the patients of Group 1 have manifested a significant decrease in levels of studied pro-inflammatory cytokines (TNF-α, IL-1β and IL-17). In parallel, we have detected an improvement of clinical indices [sulcus bleeding index (SBI), periodontal probing depth (PPD), clinical attachment level (CAL)]. At individuals of Group 2 levels of studies, pro-inflammatory cytokines and clinical indices (SBI, PPD, CAL) were significantly higher than in Group 1. Results obtained in this study indicate that application of oral treatment with tablets containing probiotic strain of L. reuteri induces in most patients with chronic periodontitis a significant reduction of pro-inflammatory cytokine response and improvement of clinical parameters (SBI, PPD, CAL). Therefore, such an effect may result in a reduced activity of the morbid process.

Molecular differences between chronic and aggressive periodontitis

The 2 major forms of periodontitis, chronic (CP) and aggressive (AgP), do not display sufficiently distinct histopathological characteristics or microbiological/immunological features. We used molecular profiling to explore biological differences between CP and AgP and subsequently carried out supervised classification using machine-learning algorithms including an internal validation. We used whole-genome gene expression profiles from 310 'healthy' or 'diseased' gingival tissue biopsies from 120 systemically healthy non-smokers, 65 with CP and 55 with AgP, each contributing with ≥ 2 'diseased' gingival papillae (n = 241; with bleeding-on-probing, probing depth ≥ 4 mm, and clinical attachment loss ≥ 3 mm), and, when available, a 'healthy' papilla (n = 69; no bleeding-on-probing, probing depth ≤ 4 mm, and clinical attachment loss ≤ 4 mm). Our analyses revealed limited differences between the gingival tissue transcriptional profiles of AgP and CP, with genes related to immune responses, apoptosis, and signal transduction overexpressed in AgP, and genes related to epithelial integrity and metabolism overexpressed in CP. Different classifying algorithms discriminated CP from AgP with an area under the curve ranging from 0.63 to 0.99. The small differences in gene expression and the highly variable classifier performance suggest limited dissimilarities between established AgP and CP lesions. Future analyses may facilitate the development of a novel, 'intrinsic' classification of periodontitis based on molecular profiling.

Periodontal disease immunology: 'double indemnity' in protecting the host

During the last two to three decades our understanding of the immunobiology of periodontal disease has increased exponentially, both with respect to the microbial agents triggering the disease process and the molecular mechanisms of the host engagement maintaining homeostasis or leading to collateral tissue damage. These foundational scientific findings have laid the groundwork for translating cell phenotype, receptor engagement, intracellular signaling pathways and effector functions into a 'picture' of the periodontium as the host responds to the 'danger signals' of the microbial ecology to maintain homeostasis or succumb to a disease process. These findings implicate the chronicity of the local response in attempting to manage the microbial challenge, creating a 'Double Indemnity' in some patients that does not 'insure' health for the periodontium. As importantly, in reflecting the title of this volume of Periodontology 2000, this review attempts to inform the community of how the science of periodontal immunology gestated, how continual probing of the biology of the disease has led to an evolution in our knowledge base and how more recent studies in the postgenomic era are revolutionizing our understanding of disease initiation, progression and resolution. Thus, there has been substantial progress in our understanding of the molecular mechanisms of host-bacteria interactions that result in the clinical presentation and outcomes of destructive periodontitis. The science has embarked from observations of variations in responses related to disease expression with a focus for utilization of the responses in diagnosis and therapeutic outcomes, to current investigations using cutting-edge fundamental biological processes to attempt to model the initiation and progression of soft- and hard-tissue destruction of the periodontium. As importantly, the next era in the immunobiology of periodontal disease will need to engage more sophisticated experimental designs for clinical studies to enable robust translation of basic biologic processes that are in action early in the transition from health to disease, those which stimulate microenvironmental changes that select for a more pathogenic microbial ecology and those that represent a rebalancing of the complex host responses and a resolution of inflammatory tissue destruction.

Non-bacterial protein expression in periodontal pockets by proteome analysis

OBJECTIVES

To compare the proteomic profile of inter-proximal pocket tissues with inter-proximal healthy tissues in the same subject to reveal proteins associated with periodontal disease in sites where periodontopathogenic bacteria were not detectable.

METHODS

Twenty-five healthy patients, with moderate-to-advanced chronic periodontitis and presenting with at least one intra-bony defect next to a healthy inter-proximal site were enrolled. The periodontal defects were treated with osseous resective surgery, and the flap design included both the periodontal pockets and the neighbouring inter-proximal healthy sites. Pocket-associated and healthy tissues were harvested for proteomic analyses.

RESULTS

Fifteen proteins were differently expressed between pathological and healthy tissues. In particular, annexin A2, actin cytoplasmic 1, carbonic anhydrase 1 & 2; Ig kappa chain C region (two spots) and flavinreductase were overexpressed, whereas 14-3-3 protein sigma and zeta/delta, heat-shock protein beta -1 (two spots), triosephosphateisomerase, peroxiredoxin-1, fatty acid-binding protein-epidermal, and galectin-7 were underexpressed in pathological tissue.

CONCLUSIONS

The unbalanced functional network of proteins involved could hinder adequate tissue response to pathogenic noxa. The study of periodontal pocket tissue proteomic profile would be crucial to better understand the pathogenesis of and the therapeutic strategies for periodontitis.

Oral epithelial cell responses to multispecies microbial biofilms

This report describes the use of a novel model of multispecies biofilms to stimulate profiles of cytokines/chemokines from oral epithelial cells that contribute to local inflammation in the periodontium. Streptococcus gordonii (Sg)/S. oralis (So)/S. sanguinis (Ss) and Sg/Fusobacterium nucleatum (Fn)/Porphyromonas gingivalis (Pg) biofilms elicited significantly elevated levels of IL-1α and showed synergistic stimulatory activity compared with an additive effect of the 3 individual bacteria. Only the Sg/Actinomyces naeslundii (An)/Fn multispecies biofilms elicited IL-6 levels above those of control. IL-8 was a primary response to the Sg/An/Fn biofilms, albeit the level was not enhanced compared with a predicted composite level from the monospecies challenges. These results represent some of the first data documenting alterations in profiles of oral epithelial cell responses to multispecies biofilms.

Role of the NK cell-activating receptor CRACC in periodontitis

Periodontitis is a highly prevalent, biofilm-mediated chronic inflammatory disease that results in the loss of the tooth-supporting tissues. It features two major clinical entities: chronic periodontitis, which is more common, and aggressive periodontitis, which usually has an early onset and a rapid progression. Natural killer (NK) cells are a distinct subgroup of lymphocytes that play a major role in the ability of the innate immune system to steer immune responses. NK cells are abundant in periodontitis lesions, and NK cell activation has been causally linked to periodontal tissue destruction. However, the exact mechanisms of their activation and their role in the pathophysiology of periodontitis are elusive. Here, we show that the predominant NK cell-activating molecule in periodontitis is CD2-like receptor activating cytotoxic cells (CRACC). We show that CRACC induction was significantly more pronounced in aggressive than chronic periodontitis and correlated positively with periodontal disease severity, subgingival levels of specific periodontal pathogens, and NK cell activation in vivo. We delineate how Aggregatibacter actinomycetemcomitans, an oral pathogen that is causally associated with aggressive periodontitis, indirectly induces CRACC on NK cells via activation of dendritic cells and subsequent interleukin 12 (IL-12) signaling. In contrast, we demonstrate that fimbriae from Porphyromonas gingivalis, a principal pathogen in chronic periodontitis, actively attenuate CRACC induction on NK cells. Our data suggest an involvement of CRACC-mediated NK cell activation in periodontal tissue destruction and point to a plausible distinction in the pathobiology of aggressive and chronic periodontitis that may help explain the accelerated tissue destruction in aggressive periodontitis.

Failure to detect an association between aggressive periodontitis and the prevalence of herpesviruses

BACKGROUND

Herpes simplex virus type 1 (HSV-1), human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) have been suspected to play a causal role in periodontitis pathogenesis. The aim of this study was to determine the prevalence of these viruses in subgingival plaque samples of Caucasian patients with generalized aggressive periodontitis compared to periodontally healthy controls.

METHODS

A total of 65 patients with aggressive periodontitis and 65 unmatched controls from Germany were investigated in the study. Subgingival plaque samples were analysed for the presence of HSV-1, EBV and HCMV by quantitative real-time polymerase chain reaction assays. Viral antibody titres were determined quantitatively by immunosorbent assays.

RESULTS

DNA of HSV-1 and HCMV were detected in 1.5% of the patients and controls, whereas EBV DNA was present in 10.8% and 13.9% respectively. Detection rates of serum IgG against HSV-1 (76.1% versus 73.9%), EBV (98.5% versus 96.9%), HCMV (47.7% versus 46.2%) and IgM levels against HSV-1 (6.2% versus 1.5%), EBV (0% versus 0%), HCMV (0% versus 1.5%) did not significantly differ between patients and controls.

CONCLUSION

The data of our study do not suggest any contribution of HSV-1, EBV or HCMV to aggressive periodontitis in a German population. Ethnic and methodological aspects might have caused conflicting results of previous studies.

Multispecies biofilms and host responses: "discriminating the trees from the forest"

Periodontal diseases reflect a tissue destructive process of the hard and soft tissues of the periodontium that are initiated by the accumulation of multispecies bacterial biofilms in the subgingival sulcus. This accumulation, in both quantity and quality of bacteria, results in a chronic immunoinflammatory response of the host to control this noxious challenge, leading to collateral damage of the tissues. As knowledge of the characteristics of the host-bacterial interactions in the oral cavity has expanded, new knowledge has become available on the complexity of the microbial challenge and the repertoire of host responses to this challenge. Recent results from the Human Microbiome Project continue to extend the array of taxa, genera, and species of bacteria that inhabit the multiple niches in the oral cavity; however, there is rather sparse information regarding variations in how host cells discriminate commensal from pathogenic species, as well as how the host response is affected by the three-dimensional architecture and interbacterial interactions that occur in the oral biofilms. This review provides some insights into these processes by including existing literature on the biology of nonoral bacterial biofilms, and the more recent literature just beginning to document how the oral cavity responds to multispecies biofilms.

Probiotic effects of orally administered Lactobacillus reuteri-containing tablets on the subgingival and salivary microbiota in patients with gingivitis. A randomized clinical trial

OBJECTIVE

To investigate the effects of an orally administered probiotic on the oral microbiota.

METHODS

A placebo-controlled, parallel study was conducted in 40 gingivitis subjects during 8 weeks. Treatment consisted on the administration of a daily tablet, either containing Lactobacillus reuteri or placebo. Unstimulated saliva and subgingival samples were collected and analysed by culture and PCR. Clinical and microbiological outcome variables were compared between and within groups.

RESULTS

There were no significant changes between and within the groups in the clinical variables. In saliva, total anaerobic counts after 4 weeks (p = 0.021) and counts of Prevotella intermedia after 8 weeks (p = 0.030), showed reductions in the test group. In subgingival samples, significant reductions in the changes baseline to 4 weeks were observed for P. gingivalis counts (p = 0.008). With PCR, L. reuteri ATCC-PTA-5289 was more frequently detected than L. reuteri DSM-17938.

CONCLUSIONS

The effect of L. reuteri administered in tablets resulted in a reduction in the number of selected periodontal pathogens in the subgingival microbiota, without an associated clinical impact.

Detection of Fusobacterium nucleatum in chorionic tissues of high-risk pregnant women

AIM

This study was undertaken to investigate the existence of a periodontopathic bacterium, Fusobacterium nucleatum, in chorionic tissues of pregnant women, and the effects of F. nucleatum on human chorion-derived cells.

MATERIALS AND METHODS

Oral and chorionic tissue samples were collected from 24 high-risk pregnant women and 15 normal pregnant women. The presence of F. nucleatum in the samples was detected using polymerase chain reaction. Chorion-derived cells and Toll-like receptor (TLR)-2 or TLR-4 gene-silenced chorion-derived cells were stimulated with F. nucleatum lipopolysaccharide (LPS). Interleukin (IL)-6 and corticotrophin-releasing hormone (CRH) levels in the culture supernatants were measured using ELISA.

RESULTS

F. nucleatum was detected in all oral samples and seven chorionic tissues from the high-risk pregnant women, but was not detected in chorionic tissues from the normal pregnant women. F. nucleatum LPS significantly increased IL-6 and CRH secretion by chorion-derived cells. The F. nucleatum LPS-induced IL-6 and CRH levels were significantly reduced in TLR-2 or TLR-4 gene-silenced chorion-derived cells.

CONCLUSIONS

We suggest that F. nucleatum is detected in chorionic tissues of high-risk pregnant women, but not in chorionic tissues of normal pregnant women, and that F. nucleatum induces IL-6 and CRH production via both TLR-2 and TLR-4 in chorion-derived cells.

Oral microbial biofilm stimulation of epithelial cell responses

Oral bacterial biofilms trigger chronic inflammatory responses in the host that can result in the tissue destructive events of periodontitis. However, the characteristics of the capacity of specific host cell types to respond to these biofilms remain ill-defined. This report describes the use of a novel model of bacterial biofilms to stimulate oral epithelial cells and profile select cytokines and chemokines that contribute to the local inflammatory environment in the periodontium. Monoinfection biofilms were developed with Streptococcus sanguinis, Streptococcus oralis, Streptococcus gordonii, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis on rigid gas-permeable contact lenses. Biofilms, as well as planktonic cultures of these same bacterial species, were incubated under anaerobic conditions with a human oral epithelial cell line, OKF4, for up to 24h. Gro-1α, IL1α, IL-6, IL-8, TGFα, Fractalkine, MIP-1α, and IP-10 were shown to be produced in response to a range of the planktonic or biofilm forms of these species. P. gingivalis biofilms significantly inhibited the production of all of these cytokines and chemokines, except MIP-1α. Generally, the biofilms of all species inhibited Gro-1α, TGFα, and Fractalkine production, while F. nucleatum biofilms stimulated significant increases in IL-1α, IL-6, IL-8, and IP-10. A. naeslundii biofilms induced elevated levels of IL-6, IL-8 and IP-10. The oral streptococcal species in biofilms or planktonic forms were poor stimulants for any of these mediators from the epithelial cells. The results of these studies demonstrate that oral bacteria in biofilms elicit a substantially different profile of responses compared to planktonic bacteria of the same species. Moreover, certain oral species are highly stimulatory when in biofilms and interact with host cell receptors to trigger pathways of responses that appear quite divergent from individual bacteria.

Epithelial interleukin-8 responses to oral bacterial biofilms

An in vitro model of bacterial biofilms on rigid gas-permeable contact lenses (RGPLs) was developed to challenge oral epithelial cells. This novel model provided seminal data on oral biofilm-host cell interactions, and with selected bacteria, the biofilms were more effective than their planktonic counterparts at stimulating host cell responses.

Periodontal infections: understanding the complexity--consensus of the Seventh European Workshop on Periodontology

INTRODUCTION

Periodontal diseases are the pathological manifestation of the host response against the bacterial challenge from the dental biofilm at the tooth/gingival interface. The remit of this working group was to update the existing knowledge on the infectious nature of periodontal diseases.

MATERIAL AND METHODS

The literature was systematically searched and critically reviewed. Four manuscripts were produced in specific topics identified as key areas to understand the importance of the microorganisms in the etio-pathogenesis of periodontal diseases.

RESULTS/CONCLUSIONS

The results and conclusions of the review process are presented in the following papers, together with the group consensus statements aiming to answer the following questions: (1) Has the use of molecular methods for the characterization of the human oral microbiome changed our understanding of the role of bacteria in the pathogenesis of periodontal disease process? (2) Are the periodontal microbial complexes associated with specific cell and tissue responses? (3) How is the development of dental biofilms influenced by the host? (4) What can we learn about biofilm/host interactions from the study of inflammatory bowel disease? This consensus report provides answers to these questions with the most updated information on periodontal microbiology.