Microbiology of periodontal diseases: introduction

Pursuing new periodontal pathogens with an improved RNA-oligonucleotide quantification technique (ROQT)

OBJECTIVE

The aim of this study was to optimize the sensitivity, specificity and cost-effectiveness of the RNA-Oligonucleotide Quantification Technique (ROQT) in order to identify periodontal pathogens that remain unrecognized or uncultured in the oral microbiome.

DESIGN

Total nucleic acids (TNA) were extracted from subgingival biofilm samples using an automated process. RNA, DNA and Locked Nucleic Acid (LNA) digoxigenin-labeled oligonucleotide probes targeting 5 cultivated/named species and 16 uncultivated or unnamed bacterial taxa were synthesized. Probe specificity was determined by targeting 96 oral bacterial species; sensitivity was assessed using serial dilutions of reference bacterial strains. Different stringency temperatures were compared and new standards were tested. The tested conditions were evaluated analyzing samples from periodontally healthy individuals, and patients with moderate or severe periodontitis.

RESULTS

The automated extraction method at 63⁰C along with LNA-oligunucleotides probes, and use of reverse RNA sequences for standards yielded stronger signals without cross-reactions. In the pilot clinical study, the most commonly detected uncultivated/unrecognized species were Selenomonas sp. HMT 134, Prevotella sp. HMT 306, Desulfobulbus sp. HMT 041, Synergistetes sp. HMT 360 and Bacteroidetes HMT 274. In the cultivated segment of the microbiota, the most abundant taxa were T. forsythia HMT 613 and Fretibacterium fastidiosum (formerly Synergistetes) HMT 363.

CONCLUSIONS

In general, samples from severe patients had the greatest levels of organisms. Classic (T. forsythia, P. gingivalis) and newly proposed (F. alocis and Desulfobulbus sp. HMT 041) pathogens were present in greater amounts in samples from severe periodontitis sites, followed by moderate periodontitis sites.

Clinical Microbial Identification of Severe Oral Infections by MALDI-TOF Mass Spectrometry in Stockholm County: an 11-Year (2010 to 2020) Epidemiological Investigation

Growing evidence suggests that oral infections can modify the course of systemic diseases. To date, epidemiological data on microbial oral infections are scarce. Here, we performed a comprehensive analysis of the trend and microbial diversity in oral infection specimens referred for clinical microbiology analysis from 2010 to 2020. The microbes were isolated by culture and were identified via matrix-assisted laser desorption ionization-time of flight mass spectrometry technology (MALDI-TOF MS) throughout the study period. A total of 1,014 referred samples from dental clinics in Stockholm County with dentoalveolar abscesses and jaw osteomyelitis being the main reason were identified. Overall, the microbial composition was dominated by Firmicutes (51%), followed by Bacteroidetes (19%), Proteobacteria (12%), and Actinobacteria (5%). At the genus level, Streptococcus spp. (36%), Prevotella spp. (18%), and Staphylococcus spp. (11%) were among the most frequently reported. Interestingly, a strong increase in trend was noted for Streptococcus anginosus, Streptococcus mitis, Streptococcus sanguinis, Eikenella corrodens, Actinomyces spp., Aggregatibacter aphrophilus, Staphylococcus epidermidis, and Granulicatella adiacens during the study time (R = 0.66 to 0.89, P < 0.05), and a minor increase was noted for Enterococcus faecalis and Klebsiella spp., whereas steady levels were noted for most of the others. The present study shows the diversity of bacteria that have been involved in dental infections during the last decade in the capital of Sweden, as well as the emerging oral microbiota trend, with clear clinical implications on the oral-systemic link. IMPORTANCE Oral diseases and associated microbes are a risk factor for systemic diseases and can change the courses of these diseases. To date, epidemiological data on microbial oral infections are scarce, and longitudinal reports are lacking. We present for the first time the microbial composition of severe oral bacterial infections determined via the MALDI-TOF mass spectrometry technique in a comprehensive study between 2010 and 2020 (11 years) in Stockholm County. The trend and microbial diversity of oral infections were analyzed on referred clinical microbiological samples and were processed by standardized protocols. Trend increase was noted for Streptococcus anginosus, Streptococcus mitis, Streptococcus sanguinis, Eikenella corrodens, Actinomyces spp., Aggregatibacter aphrophilus, Staphylococcus epidermidis, Granulicatella adiacens, Enterococcus faecalis, and Klebsiella spp. Our results provide new insights into the diversity and trend of oral microbiota that were involved in serious oral infections over the past decade in the capital of Sweden and may influence the oral-systemic link.

Potential Roles of Selectins in Periodontal Diseases and Associated Systemic Diseases: Could They Be Targets for Immunotherapy?

Periodontal diseases are predisposing factors to the development of many systemic disorders, which is often initiated via leukocyte infiltration and vascular inflammation. These diseases could significantly affect human health and quality of life. Hence, it is vital to explore effective therapies to prevent disease progression. Periodontitis, which is characterized by gingival bleeding, disruption of the gingival capillary's integrity, and irreversible destruction of the periodontal supporting bone, appears to be caused by overexpression of selectins in periodontal tissues. Selectins (P-, L-, and E-selectins) are vital members of adhesion molecules regulating inflammatory and immune responses. They are mainly located in platelets, leukocytes, and endothelial cells. Furthermore, selectins are involved in the immunopathogenesis of vascular inflammatory diseases, such as cardiovascular disease, diabetes, cancers, and so on, by mediating leukocyte recruitment, platelet activation, and alteration of endothelial barrier permeability. Therefore, selectins could be new immunotherapeutic targets for periodontal disorders and their associated systemic diseases since they play a crucial role in immune regulation and endothelium dysfunction. However, the research on selectins and their association with periodontal and systemic diseases remains limited. This review aims to discuss the critical roles of selectins in periodontitis and associated systemic disorders and highlights the potential of selectins as therapeutic targets.

Effect of chewing gum containing Xylitol and blackberry powder on oral bacteria: A randomized controlled crossover trial

OBJECTIVE

The aim was to determine the effect of chewing gum containing xylitol and freeze-dried blackberry powder on oral bacteria.

DESIGN

This was a randomized, controlled, cross-over study (RCT #: NCT05133557). Fifty participants chewed gum over an 8 h period, four times for 20 min at 2-hour intervals, containing 700 mg xylitol (CG) with or without 50 mg blackberry powder (BG), while wearing a stent containing a sterile enamel chip. After a 1 week washout, participants chewed gum from the other group following the same protocol. The primary outcome was the amount of nine oral bacteria in saliva as determined by quantitative PCR. The secondary outcome was bacteria formed on enamel chips.

RESULTS

Chewing BG for four twenty-minute intervals reduced mean total bacteria load and the relative abundance of six of the nine bacteria studied in saliva (p < 0.05). In comparison, only four bacteria were reduced in abundance in the CG group. After gum chewing and regardless of group, S. sanguinis and A. naeslundii were the predominant bacteria adherent to enamel, with S. mutans representing < 1 % of the total bacteria on enamel.

CONCLUSION

Bacterial loads in saliva were rapidly, differentially, and significantly reduced after one day of chewing BG.

A cross-sectional study of relationships between periodontal disease and general health: The Hitachi Oral Healthcare Survey

BACKGROUND

This cross-sectional study performed to clarify the relationship between periodontal disease and non-communicable diseases (NCDs), such as obesity, diabetes mellitus, impaired glucose tolerance (IGT), chronic obstructive pulmonary disease (COPD), and atherosclerotic cardiovascular disease (ASCVD) by introducing dental examinations into the annual health examinations conducted by Japanese companies, and to highlights the importance of a medical system that connects dental and medical professionals.

METHODS

A total of 1.022 Hitachi Ltd. employees were enrolled in this cross-sectional study. We examined correlations and odds ratios (ORs) between the dental and overall health of employees using stratification and multiple logistic regression analyses based on the periodontal health indicators, general health indicators, and occlusal force.

RESULTS

The adjusted OR of PPD for obesity (OR, 1.42; 95% confidence interval [CI], 1.09-1.84; p = 0.009), IGT (OR, 1.48; 95% CI, 1.00-2.20; p = 0.049), and COPD (OR, 1.38; 95% CI, 1.02-1.88; p = 0.038) significantly differed. The adjusted OR of body mass index (OR, 1.28; 95% CI 1.15-1.42; p < 0.001), haemoglobin A1C (HbA1c) (OR, 4.34; 95% CI, 1.89-9.98; p < 0.001), fasting blood glucose (FBG) levels (OR, 1.08; 95% CI 1.04-1.11; p < 0.001), postbronchodilator forced expiratory volume in one second/forced vital capacity ratio (%FEV1) (OR, 0.95; 95% CI 0.91-1.00; p = 0.031) and smoking (OR, 2.32; 95% CI 1.62-3.33; p < 0.001) for severe periodontal disease also significantly differed. Occlusal force was significantly reduced in employees aged 50-59 years compared to those aged 40-49 years. Both PPD, HbA1c, FBG levels were significantly associated with occlusal force among employees with moderate/severe periodontitis. PPD was significantly associated with occlusal force among employees with and moderate COPD, and ASCVD. %FEV1 was significantly associated with occlusal force among employees with IGT.

CONCLUSIONS

This cross-sectional study revealed mutual relationships among periodontal disease, NCDs, and occlusal force on Japanese corporate workers. We demonstrated that a comprehensive, regional healthcare system centred on annual integrated dental and physical health examinations in the workplace will benefit employees and positively impact corporate health insurance.

Application of specialized pro-resolving mediators in periodontitis and peri-implantitis: a review

Scaling and root planning is a key element in the mechanical therapy used for the eradication of biofilm, which is the major etiological factor for periodontitis and peri‐implantitis. However, periodontitis is also a host mediated disease, therefore, removal of the biofilm without adjunctive therapy may not achieve the desired clinical outcome due to persistent activation of the innate and adaptive immune cells. Most recently, even the resident cells of the periodontium, including periodontal ligament fibroblasts, have been shown to produce several inflammatory factors in response to bacterial challenge. With increased understanding of the pathophysiology of periodontitis, more research is focusing on opposing excessive inflammation with specialized pro‐resolving mediators (SPMs). This review article covers the major limitations of current standards of care for periodontitis and peri‐implantitis, and it highlights recent advances and prospects of SPMs in the context of tissue reconstruction and regeneration. Here, we focus primarily on the role of SPMs in restoring tissue homeostasis after periodontal infection.

Adjunctive systemic antimicrobials for the non-surgical treatment of periodontitis

BACKGROUND

Systemic antimicrobials can be used as an adjunct to mechanical debridement (scaling and root planing (SRP)) as a non-surgical treatment approach to manage periodontitis. A range of antibiotics with different dosage and combinations are documented in the literature. The review follows the previous classification of periodontitis as all included studies used this classification.

OBJECTIVES

To assess the effects of systemic antimicrobials as an adjunct to SRP for the non-surgical treatment of patients with periodontitis.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases to 9 March 2020: Cochrane Oral Health's Trials Register, CENTRAL, MEDLINE, and Embase. The US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) which involved individuals with clinically diagnosed untreated periodontitis. Trials compared SRP with systemic antibiotics versus SRP alone/placebo, or with other systemic antibiotics.

DATA COLLECTION AND ANALYSIS

We selected trials, extracted data, and assessed risk of bias in duplicate. We estimated mean differences (MDs) for continuous data, with 95% confidence intervals (CIs). We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 45 trials conducted worldwide involving 2664 adult participants. 14 studies were at low, 8 at high, and the remaining 23 at unclear overall risk of bias. Seven trials did not contribute data to the analysis. We assessed the certainty of the evidence for the 10 comparisons which reported long-term follow-up (≥ 1 year). None of the studies reported data on antimicrobial resistance and patient-reported quality of life changes. Amoxicillin + metronidazole + SRP versus SRP in chronic/aggressive periodontitis: the evidence for percentage of closed pockets (MD -16.20%, 95% CI -25.87 to -6.53; 1 study, 44 participants); clinical attachment level (CAL) (MD -0.47 mm, 95% CI -0.90 to -0.05; 2 studies, 389 participants); probing pocket depth (PD) (MD -0.30 mm, 95% CI -0.42 to -0.18; 2 studies, 389 participants); and percentage of bleeding on probing (BOP) (MD -8.06%, 95% CI -14.26 to -1.85; 2 studies, 389 participants) was of very low certainty. Only the results for closed pockets and BOP showed a minimally important clinical difference (MICD) favouring amoxicillin + metronidazole + SRP. Metronidazole + SRP versus SRP in chronic/aggressive periodontitis: the evidence for percentage of closed pockets (MD -12.20%, 95% CI -29.23 to 4.83; 1 study, 22 participants); CAL (MD -1.12 mm, 95% CI -2.24 to 0; 3 studies, 71 participants); PD (MD -1.11 mm, 95% CI -2.84 to 0.61; 2 studies, 47 participants); and percentage of BOP (MD -6.90%, 95% CI -22.10 to 8.30; 1 study, 22 participants) was of very low certainty. Only the results for CAL and PD showed an MICD favouring the MTZ + SRP group. Azithromycin + SRP versus SRP for chronic/aggressive periodontitis: we found no evidence of a difference in percentage of closed pockets (MD 2.50%, 95% CI -10.19 to 15.19; 1 study, 40 participants); CAL (MD -0.59 mm, 95% CI -1.27 to 0.08; 2 studies, 110 participants); PD (MD -0.77 mm, 95% CI -2.33 to 0.79; 2 studies, 110 participants); and percentage of BOP (MD -1.28%, 95% CI -4.32 to 1.76; 2 studies, 110 participants) (very low-certainty evidence for all outcomes). Amoxicillin + clavulanate + SRP versus SRP for chronic periodontitis: the evidence from 1 study, 21 participants for CAL (MD 0.10 mm, 95% CI -0.51 to 0.71); PD (MD 0.10 mm, 95% CI -0.17 to 0.37); and BOP (MD 0%, 95% CI -0.09 to 0.09) was of very low certainty and did not show a difference between the groups. Doxycycline + SRP versus SRP in aggressive periodontitis: the evidence from 1 study, 22 participants for CAL (MD -0.80 mm, 95% CI -1.49 to -0.11); and PD (MD -1.00 mm, 95% CI -1.78 to -0.22) was of very low certainty, with the doxycycline + SRP group showing an MICD in PD only. Tetracycline + SRP versus SRP for aggressive periodontitis: we found very low-certainty evidence of a difference in long-term improvement in CAL for the tetracycline group (MD -2.30 mm, 95% CI -2.50 to -2.10; 1 study, 26 participants). Clindamycin + SRP versus SRP in aggressive periodontitis: we found very low-certainty evidence from 1 study, 21 participants of a difference in long-term improvement in CAL (MD -1.70 mm, 95% CI -2.40 to -1.00); and PD (MD -1.80 mm, 95% CI -2.47 to -1.13) favouring clindamycin + SRP. Doxycycline + SRP versus metronidazole + SRP for aggressive periodontitis: there was very low-certainty evidence from 1 study, 27 participants of a difference in long-term CAL (MD 1.10 mm, 95% CI 0.36 to 1.84); and PD (MD 1.00 mm, 95% CI 0.30 to 1.70) favouring metronidazole + SRP. Clindamycin + SRP versus metronidazole + SRP for aggressive periodontitis: the evidence from 1 study, 26 participants for CAL (MD 0.20 mm, 95% CI -0.55 to 0.95); and PD (MD 0.20 mm, 95% CI -0.38 to 0.78) was of very low certainty and did not show a difference between the groups. Clindamycin + SRP versus doxycycline + SRP for aggressive periodontitis: the evidence from 1 study, 23 participants for CAL (MD -0.90 mm, 95% CI -1.62 to -0.18); and PD (MD -0.80 mm, 95% CI -1.58 to -0.02) was of very low certainty and did not show a difference between the groups. Most trials testing amoxicillin, metronidazole, and azithromycin reported adverse events such as nausea, vomiting, diarrhoea, mild gastrointestinal disturbances, and metallic taste. No serious adverse events were reported.

AUTHORS' CONCLUSIONS

There is very low-certainty evidence (for long-term follow-up) to inform clinicians and patients if adjunctive systemic antimicrobials are of any help for the non-surgical treatment of periodontitis. There is insufficient evidence to decide whether some antibiotics are better than others when used alongside SRP. None of the trials reported serious adverse events but patients should be made aware of the common adverse events related to these drugs. Well-planned RCTs need to be conducted clearly defining the minimally important clinical difference for the outcomes closed pockets, CAL, PD, and BOP.

Clinical outcomes of adjunctive indocyanine green-diode lasers therapy for treating refractory periodontitis: A randomized controlled trial with in vitro assessment

BACKGROUND/PURPOSE

It is still challengeable to treat periodontal pockets refractory to mechanical debridement. This study is to evaluate the potential of indocyanine green (ICG)-diode laser-based photothermal therapy (PTT) for solving this dilemma.

METHODS

Bone marrow-derived mesenchymal stem cells (BMSCs) and periodontal ligament cells (PDLCs) were incubated with phosphate-buffered saline, chlorhexidine, or ICG, non-irradiated or irradiated with 810-nm diode lasers, and the cell viability was evaluated. Patients with teeth refractory to mechanical periodontal debridement on different quadrants were recruited. At baseline (T0), all examined teeth received scaling and root planing, and those on the test quadrant (PTT group) received ICG-diode laser treatment. The outcome was evaluated using clinical parameters and cytokines in the gingival crevicular fluids at 4-6 weeks (T1) and 6 months (T2).

RESULTS

In ICG-treated cultures, the viability of BMSCs and PDLCs was recovered on day 4, and laser irradiation inhibited the metabolic activities of BMSCs. 22 patients with 30 control teeth and 35 PTT-treated teeth were examined. All examined teeth showed modest reductions in probing pocket depth (PPD), clinical attachment loss (CAL), bleeding upon probing (BOP), and plaque score at T1 and T2 and significant reductions in IL-1β and MMP-8 at T2. Compared with controls, BOP was reduced more prominently, IL-1β and MMP-8 were significantly lower, and reductions in PPD and CAL were slightly greater in the PTT group at T1 (0.05-0.19 mm).

CONCLUSION

ICG-diode laser-based PTT is compatible to periodontium and assists in faster resolution of gingival inflammation in periodontal pockets refractory to mechanical debridement.

Subgingival Microbiota of Mexicans with Type 2 Diabetes with Different Periodontal and Metabolic Conditions

Background: Type-2-Diabetes (T2D) and Periodontitis are major inflammatory diseases. However, not much is known about the specific subgingival microbiota in Mexicans with diabetes and metabolic dysbiosis. The aim of this study was to describe the subgingival microbiota of Mexicans with T2D and the different periodontal and metabolic conditions, through “Checkerboard” DNA–DNA hybridization. Methods: Subjects were divided into two groups—periodontal-health (PH) (PH_non-T2D; n = 59, PH_T2D; n = 14) and generalized-periodontitis (GP) (GP_non-T2D; n = 67, GP_T2D; n = 38). Obesity (BMI ≥ 30 kg/m²) and serum levels of glycated-hemoglobin (HbA1c), total-lipids, triglycerides, total-cholesterol, high-density-lipids, and low-density-lipids were measured for the T2D individuals. Subgingival microbial identification was processed for 40 species through DNA-probes. Results: Subjects with T2D harbored significantly higher mean total levels (PH: p < 0.001, and GP_NS), a lower proportion of “red” complex (GP: p < 0.01), a higher proportion of “yellow” (GP; p < 0.001), and “orange” (GP; p < 0.01) complex than the non-T2D. GP_T2D individuals exhibited a greater proportion of putative-species—Campylobacter gracilis and S. constellatus (p < 0.001), and Parvimonas micra and Prevotella nigrescens (p < 0.01), than GP_non-T2D. T2D individuals with HbA1c > 8% had presented significantly higher mean pocket-depth and higher levels of G. morbillorum (p < 0.05) and those with obesity or dyslipidemia harbored higher levels, prevalence, or proportion of Streptococcus sp., Actinomyces sp., and Capnocytophaga sp. Conclusions: T2D individuals harbored a particular microbial profile different to non-T2D microbiota. Metabolic control was related to dysbiosis of microbiota—HbA1c>8% related to periodontitis and obesity or dyslipidemia with the predominance of saccharolytic bacteria, irrespective of their periodontal condition.

Orthodontic appliances did not increase risk of dental caries and periodontal disease under preventive protocol

OBJECTIVES

To assess periodontal parameters and microbial species levels after orthodontic appliance placement in patients who received oral hygiene instructions and who were monitored and motivated throughout the study.

MATERIALS AND METHODS

The Periodontal Index was recorded and saliva collection was performed before (T0) and 30 (T1), 60 (T2), and 90 (T3) days after orthodontic appliance placement in 15 patients (mean age 17.53 ± 8.0 years). Analysis was carried out using checkerboard DNA-DNA hybridization. Nonparametric statistical analysis was performed.

RESULTS

The Periodontal Index did not change. The total amount of the purple and red complexes and Candida species showed a significant decrease from T2. The green, yellow, and orange complex showed a significant decrease at T3. The specific species analysis showed that Prevotella nigrescens, Pseudomonas putida, Fusobacterium periodonticum, Pseudomonas aeruginosa, Peptostreptococcus anaerobius, and Tanerella forsythia showed high incidence before bonding, and their levels decreased at T2 and T3. Only Porphyromonas gingivalis showed increased levels at T2 and displayed the highest level at T3. The Streptococcus group decreased their levels from T2 onward.

CONCLUSIONS

A dynamic change in microbial levels was identified. The decrease in the levels of complexes present was only possible due to the mechanical method of oral hygiene implemented in this sample.

Bruxism-Related Signs and Periodontal Disease: A Preliminary Study

Background:

The effect of awake and sleep bruxism on periodontal disease has not been evaluated separately to date. Furthermore, there are few studies that have focused on awake bruxism with light force.

Objective:

The study aimed to investigate the frequency of sleep and awake bruxism in patients with periodontal disease.

Methods:

The subjects were 57 patients with periodontal disease who visited the Department of Periodontics of the Dental Hospital affiliated with Tokyo Medical and Dental University. Subjects were asked to fill out a questionnaire consisting of three items on bruxism (sleep and awake bruxism), and the maximum community periodontal index was investigated.

Results:

The proportions of individuals with high sleep bruxism-related signs and high awake bruxism-related signs were 6.0% and 44.0%, respectively. No significant difference was found in the comparison of maximum community periodontal index proportions between individuals with high sleep bruxism-related signs and high awake bruxism-related signs.

Conclusion:

The results of this survey of patients with periodontal disease showed that the proportion of subjects with high awake bruxism-related signs subjects was higher than those of the subjects with high sleep bruxism-related signs. Sleep bruxism has attracted attention as a factor influencing periodontal disease, and our data suggest that patients with periodontal disease demonstrate more bruxism while being awake than during sleep.

Association between obstructive sleep apnea and comorbidities with periodontal disease in adults

Background:

Several studies have reported an association between periodontal disease and obstructive sleep apnea (OSA). However, heterogeneity of results suggests that there is insufficient evidence to support this association.

Aims:

The objective of this study was to identify the association between periodontal disease and OSA in adults with different comorbidities.

Settings and Design:

One hundred and ninety-nine individuals (107 women and 92 men) underwent polysomnography with a mean age of 49.9 years were recruited.

Materials and Methods:

The presence of OSA, comorbidities, and periodontal disease was evaluated in each individual. Student's t-tests or Chi-square and ANOVA tests were used to determine the differences between groups.

Results:

The prevalence of periodontal disease was 62.3% and 34.1% for gingivitis. The results showed no statistically significant association between all groups of patients with OSA and non-OSA patients for gingivitis (P = 0.27) and for periodontitis (P = 0.312). However, statistically significant association was shown between periodontitis and mild OSA compared with the periodontitis and non-OSA referent (P = 0.041; odds ratio: 1.37 and 95% confidence interval 1.11–2.68). The analysis between OSA and comorbidities showed a statistically significant difference for patients with OSA and hypertension (P < 0.001) and for patients with OSA and hypertensive cardiomyopathy (P < 0.001) compared with healthy individuals. Periodontitis was more likely in men with severe OSA and with any of two comorbidities such as hypertension or hypertensive cardiomyopathy. Women with hypertension or hypertensive cardiomyopathy were more likely to have mild OSA, and these associations were statistically significant (P < 0.05).

Conclusions:

This study identified association between periodontitis and mild OSA and this association was more frequent in women with hypertension or hypertensive cardiomyopathy. Periodontitis was associated with severe OSA in men who showed any of two comorbidities such as hypertension or hypertensive cardiomyopathy.

Potent In Vitro and In Vivo Activity of Plantibody Specific for Porphyromonas gingivalis FimA

Fimbrial protein fimbrillin (FimA), a major structural subunit of Porphyromonas gingivalis, has been suggested as a vaccine candidate to control P. gingivalis-induced periodontal disease. Previously, cDNAs encoding IgG monoclonal antibodies (MAbs) against purified FimA from P. gingivalis 2561 have been cloned, and the MAbs have been produced in rice cell suspension. Here we examined the biological activities of the plant-produced MAb specific for FimA (anti-FimA plantibody) of P. gingivalis in vitro and in vivo. The anti-FimA plantibody recognized oligomeric/polymeric forms of native FimA in immunoblot analysis and showed high affinity for native FimA (KD = 0.11 nM). Binding of P. gingivalis (10(8) cells) to 2 mg of saliva-coated hydroxyapatite beads was reduced by 53.8% in the presence of 1 μg/ml plantibody. Anti-FimA plantibody (10 μg/ml) reduced invasion of periodontal ligament cells by P. gingivalis (multiplicity of infection, 100) by 68.3%. Intracellular killing of P. gingivalis opsonized with the anti-FimA plantibody by mouse macrophages was significantly increased (77.1%) compared to killing of bacterial cells with irrelevant IgG (36.7%). In a mouse subcutaneous chamber model, the number of recoverable P. gingivalis cells from the chamber fluid was significantly reduced when the numbers of bacterial cells opsonized with anti-FimA plantibody were compared with the numbers of bacterial cells with irrelevant IgG, 66.7% and 37.1%, respectively. These in vitro and in vivo effects of anti-FimA plantibody were comparable to those of the parental MAb. Further studies with P. gingivalis strains with different types of fimbriae are needed to investigate the usefulness of anti-FimA plantibody for passive immunization to control P. gingivalis-induced periodontal disease.

Activation and resolution of periodontal inflammation and its systemic impact

Inflammation is a highly organized event impacting upon organs, tissues and biological systems. Periodontal diseases are characterized by dysregulation or dysfunction of resolution pathways of inflammation that results in failure to heal and in a dominant chronic, progressive, destructive and predominantly unresolved inflammation. The biological consequences of inflammatory processes may be independent of the etiological agents, such as trauma, microbial organisms and stress. The impact of the inflammatory pathological process depends upon the tissues or organ system affected. Whilst mediators are similar, there is tissue specificity for the inflammatory events. It is plausible that inflammatory processes in one organ could directly lead to pathologies in another organ or tissue. Communication between distant parts of the body and their inflammatory status is also mediated by common signaling mechanisms mediated via cells and soluble mediators. This review focuses on periodontal inflammation, its systemic associations and advances in therapeutic approaches based on mediators acting through orchestration of natural pathways to resolution of inflammation. We also discuss a new treatment concept in which natural pathways of resolution of periodontal inflammation can be used to limit systemic inflammation and promote healing and regeneration.

Long-term evaluation of oral gavage with periodontopathogens or ligature induction of experimental periodontal disease in mice

OBJECTIVE

To evaluate in long-term periods the destruction of periodontal tissues and bacterial colonization induced by oral gavage with periodontopathogens or ligature experimental periodontal disease models.

MATERIAL AND METHODS

Forty-eight C57BL/6 J mice were divided into four groups: group C: negative control; group L: ligature; group G-Pg: oral gavage with Porphyromonas gingivalis; and group G-PgFn: oral gavage with Porphyromonas gingivalis associated with Fusobacterium nucleatum. Mice were infected by oral gavage five times in 2-day intervals. After 45 and 60 days, animals were sacrificed and the immune-inflammatory response in the periodontal tissue was assessed by stereometric analysis. The alveolar bone loss was evaluated by live microcomputed tomography and histometric analysis. qPCR was used to confirm the bacterial colonization in all the groups. Data were analyzed using the Kruskal-Wallis, Wilcoxon, and ANOVA tests, at 5 % of significance level.

RESULTS

Ligature model induced inflammation and bone resorption characterized by increased number of inflammatory cells and decreased number of fibroblasts, followed by advanced alveolar bone loss at 45 and 60 days (p < 0.05). Bacterial colonization in groups G-Pg and G-PgFn was confirmed by qPCR but inflammation and bone resorption were not observed (p < 0.05).

CONCLUSIONS

The ligature model but not the oral gavage models were effective to induce inflammation and bone loss in long-term periods. Pg colonization was observed in all models of experimental periodontal disease induction, independent of tissue alterations. These mice models of periodontitis validates, compliments, and enhances published PD models that utilize ligature or oral gavage and supports the importance of a successful colonization of a susceptible host, a bacterial invasion into vulnerable tissue, and host-bacterial interactions that lead to tissue destruction.

CLINICAL RELEVANCE

The ligature model was an effective approach to induce inflammation and bone loss similar to human periodontitis, but the oral gavage models were not efficient in inducing periodontal inflammation and tissue destruction in the conditions studied. Ligature models can provide a basis for future interventional studies that contribute to the understanding of the disease pathogenesis and the complex host response to microbial challenge.

Microbiological and clinical effects of enamel matrix derivative and sustained-release micro-spherical minocycline application as an adjunct to non-surgical therapy in peri-implant mucosal inflammation

Objectives

The purpose of this study was to compare the microbial and clinical effects of mechanical debridement (MD) alone or in combination with the application of enamel matrix derivative (EMD) and sustained-release micro-spherical minocycline (MSM) for treatment of peri-implant mucosal infl ammation (PIMI).

Materials and Methods

Subjects with at least one implant with PIMI were included and divided into control and two different test groups. In all three groups, MD was performed. In the MSM group, following MD, MSM was placed subgingivally around the implants. In the EMD group, after MD, EMD was placed in the sulcus around the implants. Sampling of peri-implant crevicular fl uid for microbial analysis with real-time polymerase chain reaction and recording of probing depth (PD) and bleeding on probing (BOP) were performed prior to as well as two weeks and three months after treatment. Median values and interquartile range were estimated for each variable during the various assessment intervals of the study.

Results

In all groups, at two weeks and three months, the counts of Porphyromonas gingivalis decreased significantly compared to baseline. Levels of P. gingivalis were significantly reduced in MSM (P<0.001) and EMD (P=0.026) groups compared to the control group. Also, clinical parameters improved significantly at two weeks and three months. Reduction of PD was significant in MSM (P<0.001) and EMD (P<0.001) groups. The decrease in BOP in the MSM, EMD, and control groups was 60%, 50%, and 20%, respectively.

Conclusion

The use of MSM and EMD can be an adjunctive treatment for management of PIMI and improves clinical parameters and reduces P. gingivalis burden three months after treatment.

Dental prophylaxis decreases the risk of acute myocardial infarction: a nationwide population-based study in Taiwan

Purpose

To investigate the association between periodontal disease (PD) and acute myocardial infarction (AMI), and evaluate the effect of dental prophylaxis on the incidence rate (IR) of AMI.

Methods

The Longitudinal Health Insurance Database 2000 from the National Health Insurance program was used to identify 511,630 patients with PD and 208,713 without PD during 2000–2010. Subjects with PD were grouped according to treatment (dental prophylaxis, intensive treatment, and PD without treatment). The IRs of AMI during the 10-year follow-up period were compared among groups. Cox regression analysis adjusted for age, sex, socioeconomic status, residential urbanicity, and comorbidities was used to evaluate the effect of PD treatment on the incidence of AMI.

Results

The IR of AMI among subjects without PD was 0.19%/year. Among those with PD, the IR of AMI was lowest in the dental prophylaxis group (0.11%/year), followed by the intensive treatment (0.28%/year) and PD without treatment (0.31%/year; P<0.001) groups. Cox regression showed that the hazard ratio (HR) for AMI was significantly lower in the dental prophylaxis group (HR =0.90, 95% confidence interval =0.86–0.95) and higher in the intensive treatment (HR =1.09, 95% confidence interval =1.03–1.15) and PD without treatment (HR =1.23, 95% confidence interval =1.13–1.35) groups than in subjects without PD.

Conclusion

PD is associated with a higher risk of AMI, which can be reduced by dental prophylaxis to maintain periodontal health.

Prevalence and quantitative analysis of Epstein-Barr virus DNA and Porphyromonas gingivalis associated with Japanese chronic periodontitis patients

Objective

A number of studies have recently suggested Epstein–Barr virus (EBV) involvement in the pathogenesis of periodontitis. In this study, we investigated the association between major periodontopathic bacteria Porphyromonas gingivalis (P. gingivalis) and EBV in Japanese chronic periodontitis (CP) patients.

Materials and methods

A group of 25 patients with CP participated in the study along with 13 individuals without periodontitis. Subgingival samples were obtained with paper points. Quantitative real-time polymerase chain reaction (PCR) was used to detect EBV DNA and P. gingivalis.

Results

In the CP patients, EBV DNA and P. gingivalis were detected in both 80 % of sites with probing pocket depths (PPD) of ≥5 mm and in 40 and 36 % of sites with PPD ≤3 mm, respectively. EBV DNA and P. gingivalis were detected in 50 and 27 % of the sites in periodontally healthy individuals. Coexistence of EBV DNA and P. gingivalis was significantly higher in the deeper PPD sites of CP patients (68 %) than in the PPD sites of the healthy controls (15 %) and shallow PPD sites of CP patients (12 %). PCR-positive deeper PPD sites of CP patients for EBV DNA and P. gingivalis range between 3.74 × 10³∼2.83 × 10⁹ and 2.73 × 10⁵∼6.65 × 10⁹ (copies/ml), respectively.

Conclusion

These results suggest an association between EBV DNA, P. gingivalis, and CP in Japanese individuals. Further studies are required to clarify this association; however, we believe that our enhanced understanding of the pathogenesis of periodontal diseases involving viral infections will lead to new treatments.

Elastase and metalloproteinase-9 concentrations in saliva in patients with chronic periodontitis

Elastase and metalloproteinase-9 (MMP-9) are two of numerous proteolytic enzymes released by neutrophilic granulocytes in the course of periodontitis. The aim of the study was to determine the concentrations of elastase and MMP-9 in saliva in patients with chronic periodontitis compared to healthy individuals.

The enzyme-linked immunosorbent assay method was employed to determine the concentrations of elastase and MMP-9 in saliva in patients with chronic periodontitis and with pocket depth (PD) ≥ 6 mm and PD < 6 mm, as well as in saliva of healthy individuals. Significantly higher concentrations of elastase and MMP-9 were observed in patients with periodontitis compared to healthy individuals (p < 0.01). Also a significant difference in elastase concentration in saliva was observed between the PD ≥ 4 mm and PD < 6 mm groups and between the PD ≥ 6 mm and control groups, and statistically significant differences in MMP-9 concentrations between the PD ≥ 6 mm and control groups. No statistically significant differences were observed between the PD < 6 mm and control groups for elastase concentrations in saliva as well as between the PD ≥ 6 mm and PD < 6 mm groups, and also between the PD < 6 mm and control groups for MMP-9 concentrations in saliva. Elastase and MMP-9 concentrations in saliva can be considered as biochemical indicators of severity of periodontitis.

The novel role of HtrA1 in gingivitis, chronic and aggressive periodontitis

Proteolytic tissue degradation is a typical phenomenon in inflammatory periodontal diseases. HtrA1 (High temperature requirement A 1) has a serine protease activity and is able to degrade fibronectin whose fragments induce the expression and secretion of several matrix metalloproteinases (MMPs). The aim of this study was to investigate for the first time if HtrA1 has a role in gingivitis and in generalized forms of chronic and aggressive periodontitis. Expression of HtrA1 was investigated in 16 clinically healthy gingiva, 16 gingivitis, 14 generalized chronic periodontitis and 10 generalized aggressive periodontitis by immunohistochemistry and real-time PCR. Statistical comparisons were performed by the Kruskall-Wallis test. Significantly higher levels of HtrA1 mRNA and protein expression were observed in pathological respect to healthy tissues. In particular, we detected an increase of plasma cell HtrA1 immunostaining from gingivitis to chronic and aggressive periodontitis, with the higher intensity in aggressive disease. In addition, we observed the presence of HtrA1 in normal and pathological epithelium, with an increased expression, particularly in its superficial layer, associated with increasingly severe forms of periodontal disease. We can affirm that HtrA1 expression in plasma cells could be correlated with the destruction of pathological periodontal tissue, probably due to its ability to trigger the overproduction of MMPs and to increase the inflammatory mediators TNF-α and IL-1β by inhibition of TGF-β. Moreover, epithelial HtrA1 immunostaining suggests a participation of the molecule in the host inflammatory immune responses necessary for the control of periodontal infection.

Oral microbiome of deep and shallow dental pockets in chronic periodontitis

We examined the subgingival bacterial biodiversity in untreated chronic periodontitis patients by sequencing 16S rRNA genes. The primary purpose of the study was to compare the oral microbiome in deep (diseased) and shallow (healthy) sites. A secondary purpose was to evaluate the influences of smoking, race and dental caries on this relationship. A total of 88 subjects from two clinics were recruited. Paired subgingival plaque samples were taken from each subject, one from a probing site depth >5 mm (deep site) and the other from a probing site depth ≤3mm (shallow site). A universal primer set was designed to amplify the V4–V6 region for oral microbial 16S rRNA sequences. Differences in genera and species attributable to deep and shallow sites were determined by statistical analysis using a two-part model and false discovery rate. Fifty-one of 170 genera and 200 of 746 species were found significantly different in abundances between shallow and deep sites. Besides previously identified periodontal disease-associated bacterial species, additional species were found markedly changed in diseased sites. Cluster analysis revealed that the microbiome difference between deep and shallow sites was influenced by patient-level effects such as clinic location, race and smoking. The differences between clinic locations may be influenced by racial distribution, in that all of the African Americans subjects were seen at the same clinic. Our results suggested that there were influences from the microbiome for caries and periodontal disease and these influences are independent.

Virulence mechanism of bacteria in mixed infection: attenuation of cytokine levels and evasion of polymorphonuclear leukocyte phagocytosis

BACKGROUND

The objective of the present study is to evaluate the effect of bacterial viability on the virulence of mixed infection.

METHODS

Expression of pro- and anti-inflammatory cytokines (interleukin [IL]-1β and IL-10, respectively) was tested in vivo, following live versus heat-killed infection (mono or mixed), using the mouse chamber model of infection. Ex vivo, phagocytosis of fluorescently labeled bacteria was tested in primary mouse polymorphonuclear leukocytes by flow cytometry.

RESULTS

In monoinfection, heat-killed Porphyromonas gingivalis led to augmented levels of IL-1β 2 hours postinfection, whereas IL-10 levels remained unaffected. Phagocytosis of heat-killed P. gingivalis was reduced compared with that of the live P. gingivalis, whereas phagocytosis of heat-killed Fusobacterium nucleatum was augmented compared with that of live F. nucleatum. In mixed infection, both IL-1β and IL-10 levels were augmented 24 hours postinfection when the bacteria were heat-killed. Although the phagocytosis pattern of F. nucleatum in the mixed infection remained similar to that upon monoinfection, phagocytosis of P. gingivalis was reduced following mixed infection.

CONCLUSIONS

The inflammatory response to live mixed infection is attenuated with reduced phagocytosis, compared with that of heat-killed mixed infection. The lower response to live mixed infection could stem from a mechanism enabling the bacteria to evade the host response, thereby increasing bacterial survival.

Occlusal adjustment associated with periodontal therapy--a systematic review

OBJECTIVES

Occlusal adjustment as part of periodontal therapy has been controversial for years, mostly because the literature does not provide enough evidence regarding the influence of trauma from occlusion (TfO) on periodontitis. The need for occlusal adjustment in periodontal therapy is considered uncertain and requires investigation. The aim of this systematic review was to identify and analyse those studies that investigated the effects of occlusal adjustment, associated with periodontal therapy, on periodontal parameters.

DATA

A protocol was developed that included all aspects of a systematic review: search strategy, selection criteria, selection methods, data collection and data extraction.

SOURCES

A literature search was conducted using MEDLINE via PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE.

STUDY SELECTION

Three reviewers screened the titles and abstracts of articles according to the established criteria. Every article that indicated a possible match, or could not be excluded based on the information given in the title or abstract, was considered and evaluated. On final selection, four articles were included.

CONCLUSIONS

Although the selected studies suggest an association between occlusal adjustment and an improvement in periodontal parameters, their methodological issues (explored in this review) suggest the need for new trials of a higher quality. There is insufficient evidence at present to presume that occlusal adjustment is necessary to reduce the progression of periodontal disease.

CLINICAL SIGNIFICANCE

Although it is still not possible to determine the role of occlusal adjustment in periodontal treatment, adverse effects have not been related to occlusal adjustment. This means that the decision made by clinicians whether or not to use occlusal adjustment in conjunction with periodontal therapy hinges upon clinical evaluation, patient comfort, and tooth function.

Non-inflammatory destructive periodontal disease: a clinical, microbiological, immunological and genetic investigation

Periodontitis comprises a group of multifactorial diseases in which periodontopathogens accumulate in dental plaque and trigger host chronic inflammatory and immune responses against periodontal structures, which are determinant to the disease outcome. Although unusual cases of non-inflammatory destructive periodontal disease (NIDPD) are described, their pathogenesis remains unknown. A unique NIDPD case was investigated by clinical, microbiological, immunological and genetic tools. The patient, a non-smoking dental surgeon with excessive oral hygiene practice, presented a generalized bone resorption and tooth mobility, but not gingival inflammation or occlusion problems. No hematological, immunological or endocrine alterations were found. No periodontopathogens (A. actinomycetemcomitans, P. gingivalis, F. nucleatum and T. denticola) or viruses (HCMV, EBV-1 and HSV-1) were detected, along with levels of IL-1β and TNF-a in GCF compatible with healthy tissues. Conversely ALP, ACP and RANKL GCF levels were similar to diseased periodontal sites. Genetic investigation demonstrated that the patient carried some SNPs, as well HLA-DR4 (*0404) and HLA-B27 alleles, considered risk factors for bone loss. Then, a less vigorous and diminished frequency of toothbrushing was recommended to the patient, resulting in the arrest of alveolar bone loss, associated with the return of ALP, ACP and RANKL in GCF to normality levels. In conclusion, the unusual case presented here is compatible with the previous description of NIDPD, and the results that a possible combination of excessive force and frequency of mechanical stimulation with a potentially bone loss prone genotype could result in the alveolar bone loss seen in NIDPD.

Host-bacteria crosstalk at the dentogingival junction

The dentogingival junction is of crucial importance in periodontal host defense both structurally and functionally. Oral bacteria exert a constant challenge to the host cells and tissues at the dentogingival junction. The host response is set up to eliminate the pathogens by the innate and adaptive defense mechanisms. In health, the commensal bacteria and the host defense mechanisms are in a dynamic steady state. During periodontal disease progression, the dental bacterial plaque, junctional epithelium (JE), inflammatory cells, connective tissue, and bone all go through a series of changes. The tissue homeostasis is turned into tissue destruction and progression of periodontitis. The classical study of Slots showed that in the bacterial plaque, the most remarkable change is the shift from gram-positive aerobic and facultatively anaerobic flora to a predominantly gram-negative and anaerobic flora. This has been later confirmed by several other studies. Furthermore, not only the shift of the bacterial flora to a more pathogenic one, but also bacterial growth as a biofilm on the tooth surface, allows the bacteria to communicate with each other and exert their virulence aimed at favoring their growth. This paper focuses on host-bacteria crosstalk at the dentogingival junction and the models studying it in vitro.

Levels of Selenomonas species in generalized aggressive periodontitis

BACKGROUND AND OBJECTIVE

To compare the levels of Selenomonas sputigena and uncultivated/unrecognized Selenomonas species in subgingival biofilms from periodontally healthy subjects and from subjects with generalized aggressive periodontitis.

MATERIAL AND METHODS

Fifteen periodontally healthy subjects and 15 subjects with generalized aggressive periodontitis were recruited and their clinical periodontal parameters were evaluated. Nine subgingival plaque samples were collected from each subject and all were individually analyzed for the levels of 10 bacterial taxa, including cultured and uncultivated/unrecognized microorganisms, using the RNA-oligonucleotide quantification technique. Between-group differences in the levels of the test taxa were determined using the Mann-Whitney U-test.

RESULTS

  Subjects with generalized aggressive periodontitis showed significantly higher mean counts of Porphyromonas gingivalis, S. sputigena and the Mitsuokella sp. Human Oral Taxon (HOT) 131 (previously described as Selenomonas sp. oral clone CS002), while higher mean counts of Actinomyces gerencseriae and Streptococcus sanguinis were found in periodontally healthy subjects (p < 0.01). Selenomonas sp. HOT 146 was only detected in the generalized aggressive periodontitis group. In the generalized aggressive periodontitis group, the levels of P. gingivalis and S. sputigena were higher in deep sites (probing depth ≥ 5 mm) than in shallow sites (probing depth ≤ 3 mm) (p < 0.01). Furthermore, in subjects with generalized aggressive periodontitis, sites with probing depth of ≤ 3 mm harbored higher levels of these two species than sites with the same probing depth in periodontally healthy subjects. There were positive correlations between probing depth and the levels of P. gingivalis (r = 0.77; p < 0.01), S. sputigena (r = 0.60; p < 0.01) and Selenomonas dianae (previously described as Selenomonas sp. oral clone EW076) (r = 0.42, p < 0.05).

CONCLUSION

S. sputigena and Mitsuokella sp. HOT 131 may be associated with the pathogenesis of generalized aggressive periodontitis, and their role in the onset and progression of this infection should be investigated further.

E-selectin mediates Porphyromonas gingivalis adherence to human endothelial cells

Porphyromonas gingivalis, a major periodontal pathogen, may contribute to atherogenesis and other inflammatory cardiovascular diseases. However, little is known about interactions between P. gingivalis and endothelial cells. E-selectin is a membrane protein on endothelial cells that initiates recruitment of leukocytes to inflamed tissue, and it may also play a role in pathogen attachment. In the present study, we examined the role of E-selectin in P. gingivalis adherence to endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with tumor necrosis factor alpha (TNF-α) to induce E-selectin expression. Adherence of P. gingivalis to HUVECs was measured by fluorescence microscopy. TNF-α increased adherence of wild-type P. gingivalis to HUVECs. Antibodies to E-selectin and sialyl Lewis X suppressed P. gingivalis adherence to stimulated HUVECs. P. gingivalis mutants lacking OmpA-like proteins Pgm6 and -7 had reduced adherence to stimulated HUVECs, but fimbria-deficient mutants were not affected. E-selectin-mediated P. gingivalis adherence activated endothelial exocytosis. These results suggest that the interaction between host E-selectin and pathogen Pgm6/7 mediates P. gingivalis adherence to endothelial cells and may trigger vascular inflammation.

Comparing culture, real-time PCR and fluorescence resonance energy transfer technology for detection of Porphyromonas gingivalis in patients with or without peri-implant infections

BACKGROUND AND OBJECTIVE

The aim of the study was to compare the detection of Porphyromonas gingivalis using a fluorescence resonance energy transfer (FRET) technology with commonly used diagnostic methods in salivary and subgingival plaque samples from subjects with dental implants. P. gingivalis was considered as a marker for a pathogenic microbiota.

MATERIAL AND METHODS

Ninety-seven adult subjects were recruited, including periodontally healthy controls with no dental implants, implant controls with no peri-implant disease and patients with peri-implant disease. Saliva and subgingival/submucosal plaque samples were collected from all subjects and were analyzed using culture, real-time PCR and FRET technology employing P. gingivalis-specific substrates.

RESULTS

It was found that the P. gingivalis-specific substrates were highly suitable for detecting the presence of P. gingivalis in saliva and in subgingival plaque samples, showing comparable specificity to culture and real-time PCR.

CONCLUSION

We applied the FRET technology to detect P. gingivalis in implant patients with or without an implant condition and in controls without implants. The technique seems suitable for detection of P. gingivalis in both plaque and saliva samples. However, with all three techniques, P. gingivalis was not very specific for peri-implantitis cases. Future work includes fine-tuning the FRET technology and also includes the development of a chair-side application.

Effect of periodontal pathogens on the metatranscriptome of a healthy multispecies biofilm model

Oral bacterial biofilms are highly complex microbial communities with up to 700 different bacterial taxa. We report here the use of metatranscriptomic analysis to study patterns of community gene expression in a multispecies biofilm model composed of species found in healthy oral biofilms (Actinomyces naeslundii, Lactobacillus casei, Streptococcus mitis, Veillonella parvula, and Fusobacterium nucleatum) and the same biofilm plus the periodontopathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. The presence of the periodontopathogens altered patterns in gene expression, and data indicate that transcription of protein-encoding genes and small noncoding RNAs is stimulated. In the healthy biofilm hypothetical proteins, transporters and transcriptional regulators were upregulated while chaperones and cell division proteins were downregulated. However, when the pathogens were present, chaperones were highly upregulated, probably due to increased levels of stress. We also observed a significant upregulation of ABC transport systems and putative transposases. Changes in Clusters of Orthologous Groups functional categories as well as gene set enrichment analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways showed that in the absence of pathogens, only sets of proteins related to transport and secondary metabolism were upregulated, while in the presence of pathogens, proteins related to growth and division as well as a large portion of transcription factors were upregulated. Finally, we identified several small noncoding RNAs whose predicted targets were genes differentially expressed in the open reading frame libraries. These results show the importance of pathogens controlling gene expression of a healthy oral community and the usefulness of metatranscriptomic techniques to study gene expression profiles in complex microbial community models.

Correlation network analysis applied to complex biofilm communities

The complexity of the human microbiome makes it difficult to reveal organizational principles of the community and even more challenging to generate testable hypotheses. It has been suggested that in the gut microbiome species such as Bacteroides thetaiotaomicron are keystone in maintaining the stability and functional adaptability of the microbial community. In this study, we investigate the interspecies associations in a complex microbial biofilm applying systems biology principles. Using correlation network analysis we identified bacterial modules that represent important microbial associations within the oral community. We used dental plaque as a model community because of its high diversity and the well known species-species interactions that are common in the oral biofilm. We analyzed samples from healthy individuals as well as from patients with periodontitis, a polymicrobial disease. Using results obtained by checkerboard hybridization on cultivable bacteria we identified modules that correlated well with microbial complexes previously described. Furthermore, we extended our analysis using the Human Oral Microbe Identification Microarray (HOMIM), which includes a large number of bacterial species, among them uncultivated organisms present in the mouth. Two distinct microbial communities appeared in healthy individuals while there was one major type in disease. Bacterial modules in all communities did not overlap, indicating that bacteria were able to effectively re-associate with new partners depending on the environmental conditions. We then identified hubs that could act as keystone species in the bacterial modules. Based on those results we then cultured a not-yet-cultivated microorganism, Tannerella sp. OT286 (clone BU063). After two rounds of enrichment by a selected helper (Prevotella oris OT311) we obtained colonies of Tannerella sp. OT286 growing on blood agar plates. This system-level approach would open the possibility of manipulating microbial communities in a targeted fashion as well as associating certain bacterial modules to clinical traits (e.g.: obesity, Crohn's disease, periodontal disease, etc).

Associations of periodontal microorganisms with salivary proteins and MMP-8 in gingival crevicular fluid

OBJECTIVE

We investigated in subjects with and without periodontitis, the levels of certain salivary proteins and matrix metalloproteinase-8 (MMP-8) in gingival crevicular fluid (GCF), in relation to the presence of specific periodontal pathogens.

METHODS

Clinical parameters were recorded at baseline, in 1985 and in 2009 from 99 subjects; 56 with and 43 without periodontitis (mean age 59.2 ± SD 2.9). Saliva samples collected in 2009 were analysed for salivary albumin, total protein and immunoglobulins A, G and M. GCF was collected for analysis of MMP-8 levels and for the PCR-analysis of the microorganisms Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola and Tannerella forsythia.

RESULTS

Periodontitis patients were more often infected by P. gingivalis (p < 0.05), P. intermedia and T. denticola (p = 0.01) than controls. Salivary albumin and protein concentrations were significantly higher in subjects with T. denticola (p < 0.05). MMP-8 levels were significantly higher in subjects with T. denticola (p < 0.001) and T. forsythia (p < 0.01). No corresponding results were found in salivary immunoglobulin concentrations.

CONCLUSION

The presence of T. denticola seemed to increase salivary albumin and total protein concentrations, and GCF levels of MMP-8. Both T. denticola and T. forsythia seemed to induce a cascade of host response with increased MMP-8 in GCF.

Paradigm shift in the pharmacological management of periodontal diseases

It is becoming clear that variations in inflammatory response are a major determinant in susceptibility to periodontitis. However, our understanding of the relationship of the causal agents in periodontitis to the pathogenesis is not as clear as we once thought, and thus therapies based on etiopathogenesis are similarly in question. We are entering a new era of therapeutic discovery that may have a major impact on our management of the periodontal diseases. Fundamentally, periodontitis is an irreversible condition and once both soft and hard tissues are lost, the healthy periodontal architecture cannot be completely or predictably rebuilt. The discovery of new families of lipid mediators of resolution of inflammation (the lipoxins) and eicosapentaenoic-acid- and docosahexaenoic-acid-derived chemical mediators (the resolvins and protectins) opens new avenues to designing resolution-targeted therapies to control the unwanted side effects of excessive inflammation. The novel protective and therapeutic actions of pro-resolution lipid mediators following microbial challenge are mediated by regulation of the local and systemic inflammatory response that has a direct impact on the organization of the biofilm (plaque) and suggests a new paradigm in clinical periodontal therapeutics.

Prevotella nigrescens and Porphyromonas gingivalis are associated with signs of carotid atherosclerosis in subjects with and without periodontitis

BACKGROUND AND OBJECTIVE

Oral microorganisms may be involved in the development of cardiovascular diseases, and Porphyromonas gingivalis is one of the periodontal microorganisms that has been found in carotid atheroma. The aim of this work was to study subgingival microorganisms and early carotid lesions in subjects with and without periodontitis.

MATERIAL AND METHODS

Eighty-eight subjects with periodontitis and 40 subjects without periodontitis underwent dental examinations in 2003. The presence of the periodontal microorganisms Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens and Tannerella forsythia was analyzed from subgingival plaque using PCR amplification. The common carotid artery was scanned using ultrasound and the calculated intima-media area (cIMA) was measured. The association between periodontitis, the cIMA value and the presence of periodontal microorganisms, together with several confounders, was studied in a multiple logistic regression model.

RESULTS

Smoking [odds ratio (OR) = 5.64; p = 0.001), level of education (OR = 5.02; p < 0.05) and the presence of P. gingivalis (OR = 6.50; p < 0.05) were associated with periodontitis. Explanatory factors for the increased cIMA were periodontitis (OR = 4.22; p < 0.05), hypertension (OR = 4.81; p < 0.05), high body mass index (OR = 5.78; p < 0.01), male gender (OR = 3.30; p < 0.05) and poor socioeconomic status (OR = 4.34; p < 0.05). P. nigrescens (OR 4.08; p < 0.05) and P. gingivalis (OR 7.63; p < 0.01) also appeared as explanatory variables associated with increased cIMA values.

CONCLUSION

This cross-sectional study showed that P. nigrescens and P. gingivalis were significantly associated with increased cIMA values.

Synergistic growth effect among bacteria recovered from root canal infections

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

The riboswitch regulates a thiamine pyrophosphate ABC transporter of the oral spirochete Treponema denticola

Thiamine pyrophosphate (TPP), a biologically active form of thiamine (vitamin B₁), is an essential cofactor in all living systems. Microorganisms either synthesize TPP via de novo biosynthesis pathways or uptake exogenous thiamine from the environment via specific transporters. The oral spirochete Treponema denticola is an important pathogen that is associated with human periodontal diseases. It lacks a de novo TPP biosynthesis pathway and needs exogenous TPP for growth, suggesting that it may obtain exogenous TPP via a thiamine transporter. In this study, we identified a gene cluster that encodes a TPP ABC transporter which consists of a TPP-binding protein (TDE0143), a transmembrane permease (TDE0144), and a cytosolic ATPase (TDE0145). Transcriptional and translational analyses showed that the genes encoding these three proteins are cotranscribed and form an operon (tbpABC(Td)) that is initiated by a σ⁷⁰-like promoter. The expression level of this operon is negatively regulated by exogenous TPP and is mediated by a TPP-sensing riboswitch (Td(thi-)(box)). Genetic and biochemical studies revealed that the TDE0143 deletion mutant (T. denticola ΔtbpA) had a decreased ability to transport exogenous TPP, and the mutant failed to grow when exogenous TPP was insufficient. These results taken together indicate that the tbpABC(Td) operon encodes an ABC transporter that is required for the uptake of exogenous TPP and that the expression of this operon is regulated by a TPP-binding riboswitch via a feedback inhibition mechanism.

Community and gene composition of a human dental plaque microbiota obtained by metagenomic sequencing

Human dental plaque is a complex microbial community containing an estimated 700 to 19,000 species/phylotypes. Despite numerous studies analysing species richness in healthy and diseased human subjects, the true genomic composition of the human dental plaque microbiota remains unknown. Here we report a metagenomic analysis of a healthy human plaque sample using a combination of second-generation sequencing platforms. A total of 860 million base pairs of non-human sequences were generated. Various analysis tools revealed the presence of 12 well-characterized phyla, members of the TM-7 and BRC1 clade, and sequences that could not be classified. Both pathogens and opportunistic pathogens were identified, supporting the ecological plaque hypothesis for oral diseases. Mapping the metagenomic reads to sequenced reference genomes demonstrated that 4% of the reads could be assigned to the sequenced species. Preliminary annotation identified genes belonging to all known functional categories. Interestingly, although 73% of the total assembled contig sequences were predicted to code for proteins, only 51% of them could be assigned a functional role. Furthermore, ~2.8% of the total predicted genes coded for proteins involved in resistance to antibiotics and toxic compounds, suggesting that the oral cavity is an important reservoir for antimicrobial resistance.

Type 1 diabetes predisposes to enhanced gingival leukocyte margination and macromolecule extravasation in vivo

BACKGROUND AND OBJECTIVE

Diabetes predisposes to periodontal disease. However, the cellular and molecular mechanisms linking the two conditions are not clear. The impact of chronic hyperglycemia on leukocyte margination and macromolecule extravasation was determined in gingival vessels in vivo.

MATERIALS AND METHODS

Gingival intravital microscopy was employed to measure extravasation of fluorescein isothiocyanate (FITC)-dextran in diabetic Akita and healthy wild-type (WT) mice. Rhodamine 6G and FITC-LY6G were injected for nonspecific and polymorphonuclear-specific leukocyte labeling, respectively. Surface expression of leukocyte adhesion molecules was determined with flow cytometry and western blotting.

RESULTS

Vascular permeability was significantly increased in Akita gingival vessels compared with WT [permeability index (PI): WT, 0.75 ± 0.05; Akita, 1.1 ± 0.03: p < 0.05). Wild-type gingival vessels reached comparable permeability 2 h after intragingival injection of tumor necrosis factor α (TNFα), used here as positive control (PI, 1.17 ± 0.16). The number of rolling leukocytes was significantly elevated in diabetic gingiva (WT, 25 ± 3.7 cells/min; Akita, 42 ± 8.5 cells/min; p < 0.03). Similar rolling cell counts were obtained in WT after intragingival injection of TNFα (10 ng TNFα, 47 ± 1.3 cells/min; 100 ng TNFα, 57.5 ± 5.85 cells/min). The number of leukocytes firmly attached to the endothelium was similar in WT and Akita mice. Leukocyte cell-surface expression of P-selectin glycoprotein ligand-1 and CD11a was increased in Akita mice, while L-selectin remained unchanged when compared with WT. Moreover, P-selectin expression in Akita gingival tissues was elevated compared with that of WT.

CONCLUSION

Chronic hyperglycemia induces a proinflammatory state in the gingival microcirculation characterized by increased vascular permeability, and leukocyte and endothelial cell activation. Leukocyte-induced microvascular damage, in turn, may contribute to periodontal tissue damage in diabetes.

Periodontal disease may associate with breast cancer

The main purpose was to evaluate the association between periodontal disease and the incidence of breast cancer in a prospective study of 3273 randomly selected subjects aged 30-40 years at baseline. Breast cancer incidence was registered from 1985 to 2001 according to the WHO International Classification of Diseases criteria. At baseline, 1676 individuals also underwent a clinical oral examination (Group A) whereas 1597 subjects were not clinically examined but were registered (Group B). The associations between breast cancer, periodontal disease, and missing molars were determined using multiple logistic regression models with several background variables and known risk factors for cancer. In total 26 subjects in group A and 15 subjects in group B had breast cancer. The incidence of breast cancer was 1.75% in subjects who had periodontal disease and/or any missing molars, and 0 in subjects who had periodontal disease but had no missing molars. For periodontally healthy subjects with no missing teeth the breast cancer incidence was 1%. For group B the respective incidence was 0.94%. Female gender (odds ratio (OR) 13.08) and missing any molar in the mandible (OR 2.36) were explanatory variables for breast cancer. Of the subjects with periodontal disease and any missing molars in the mandible 5.5% had breast cancer in comparison to 0.5% of the subjects who had periodontal disease but no missing molars in the mandible (P < 0.02). Chronic periodontal disease indicated by missing molars seemed to associate statistically with breast cancer.

The Hpk2-Rrp2 two-component regulatory system of Treponema denticola: a potential regulator of environmental and adaptive responses

Treponema denticola levels in the gingival crevice become elevated as periodontal disease develops. Oral treponemes may account for as much as 40% of the total bacterial population in the periodontal pocket. The stimuli that trigger enhanced growth of T. denticola, and the mechanisms associated with the transmission of these signals, remain to be defined. We hypothesize that the T. denticola open reading frames tde1970 (histidine kinase) and tde1969 (response regulator) constitute a functional two-component regulatory system that regulates, at least in part, responses to the changing environmental conditions associated with the development of periodontal disease. The results presented demonstrate that tde1970 and tde1969 are conserved, universal among T. denticola isolates and transcribed as part of a seven-gene operon in a growth-phase-dependent manner. tde1970 undergoes autophosphorylation and transfers phosphate to tde1969. Henceforth, the proteins encoded by these open reading frames are designated as Hpk2 and Rrp2 respectively. Hpk2 autophosphorylation kinetics were influenced by environmental conditions and by the presence or absence of a PAS domain. It can be concluded that Hpk2 and Rrp2 constitute a functional two-component system that contributes to environmental sensing.

Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints

Periodontal diseases (PD) are chronic infectious inflammatory diseases characterized by the destruction of tooth-supporting structures, being the presence of periodontopathogens required, but not sufficient, for disease development. As a general rule, host inflammatory mediators have been associated with tissue destruction, while anti-inflammatory mediators counteract and attenuate disease progression. With the discovery of several T-cell subsets bearing distinct immunoregulatory properties, this pro- vs. anti-inflammatory scenario became more complex, and a series of studies has hypothesized protective or destructive roles for Th1, Th2, Th17, and Treg subpopulations of polarized lymphocytes. Interestingly, the "protective vs. destructive" archetype is usually considered in a framework related to tissue destruction and disease progression. However, it is important to remember that periodontal diseases are infectious inflammatory conditions, and recent studies have demonstrated that cytokines (TNF-α and IFN-γ) considered harmful in the context of tissue destruction play important roles in the control of periodontal infection. Therefore, in this review, the state-of-the-art knowledge concerning the protective and destructive roles of host inflammatory immune response will be critically evaluated and discussed from the tissue destruction and control-of-infection viewpoints.