Use of checkerboard DNA-DNA hybridization to study complex microbial ecosystems

The effects of a probiotic milk drink on bacterial composition in the supra- and subgingival biofilm: a pilot study

Probiotics can convert a dysbiotic bacterial environment into a healthy one. The aim of the present study was to assess the effect of daily intake of a probiotic milk drink on the composition of bacterial species in dental supra- and subgingival biofilms. Sixteen dental students were enrolled into this study with a crossover, within subject, design. The participants were asked to allow plaque accumulation by refraining from cleaning their molars during two separate periods, each lasting three weeks. Each period consisted of an initial professional dental cleaning procedure done at the university clinic, then a 3 week plaque accumulation period, followed by a return to the clinic for supra- and subgingival plaque sampling. The first period served as a control, and during the second plaque accumulation period the participants drank 200 ml probiotic milk beverage each day. The accumulated plaque removed at the end of the accumulation period was later tested against a panel of 20 oral bacterial species using the checkerboard method. Three weeks consumption of a probiotic beverage led to a significant reduction in 15 of 20 bacterial species present in supragingival plaque and a reduction in 4 of 20 bacterial species in subgingival plaque (all P<0.05). This study showed a favorable effect of probiotics on periodontopathic bacteria in dental biofilms. The potential influence of this kind of probiotic in prevention or treatment of periodontal inflammation deserves further study.

The subgingival periodontal microbiota of the aging mouth

Different mechanisms have been hypothesized to explain the increase in prevalence and severity of periodontitis in older adults, including shifts in the periodontal microbiota. However, the actual impact of aging on the composition of subgingival biofilms remains unclear. In the present article, we provide an overview of the composition of the subgingival biofilm in older adults and the potential effects of age on the oral microbiome. In particular, this review covers the following topics: (i) the oral microbiota of an aging mouth; (ii) the effects of age and time on the human oral microbiome; (iii) the potential impact of inflammaging and immunosenescence in the host-oral microbiota interactions; and (iv) the relationship of the aging oral microbiota and Alzheimer's disease. Finally, we present analyses of data compiled from large clinical studies that evaluated the subgingival microbiota of periodontally healthy subjects and patients with periodontitis from a wide age spectrum (20-83 years of age).

Studying the human oral microbiome: challenges and the evolution of solutions

Since the pioneering work of van Leeuwenhoek in 1684, subsequently built upon by other renowned microbiologists Robert Koch, Willoughby Miller and GV Black, oral microbiology has developed innovative techniques to study the oral microflora (now termed the 'oral microbiome'). The advent of molecular techniques such as DNA-DNA hybridization, polymerase chain reaction and DNA sequencing has created an array of opportunities to construct a comprehensive picture of the diversity and composition of the oral microbiome. Approximately 700 oral bacterial species have been identified, of which 50% have yet to be cultivated, and some of these are known only by their signature DNA sequences. The synergism of ever-evolving culture-based and state-of-the-art culture-independent molecular techniques has facilitated in-depth understanding of the dynamics, acquisition and transfer of oral bacteria, along with their role in oral and general health and disease. Further research is needed to not only analyse but also to make sense of the ever-increasing volumes of data which these molecular techniques (especially high-throughput DNA sequencing) are generating, as well as why particular bacteria are present and what they are 'actually doing' there. This review presents a comprehensive literature search of oral microbiology-related methods currently used to study the oral microbiome.

Lipopolysaccharide, a possible molecular mediator between periodontitis and coronary artery disease

AIM

We aimed to study how lipopolysaccharide (LPS) in saliva and serum associates with each other, periodontal microbial burden, periodontitis and coronary artery disease (CAD).

MATERIALS AND METHODS

The used Parogene cohort comprised N = 505 Finnish adults. Coronary diagnosis was acquired by coronary angiography, and the main outcomes were as follows: no significant CAD (n = 123), stable CAD (n = 184) and acute coronary syndrome (n = 169). Periodontitis was defined according to clinical and radiographic examinations. Levels for 75 strains of subgingival bacteria were determined by checkerboard DNA-DNA hybridization. Saliva and serum LPS activity was analysed by Limulus amebocyte lysate assay.

RESULTS

The level of 11 bacterial strains, which were mainly oral and respiratory Gram-negative species, associated with salivary LPS levels in an age- and gender-adjusted linear regression. A total of 4.9% of the serum LPS, that is endotoxemia, variation was explainable by saliva LPS among patients with periodontitis (n = 247, R²  = .049, Pearson's r = .222, p < .001). Endotoxemia associated with stable CAD in a confounder adjusted multinomial logistic regression model (OR 1.99, 95% CI 1.04-3.81, p = .039, 3rd tertile).

CONCLUSIONS

In particular in periodontitis patients, subgingival microbial burden contributes to endotoxemia. LPS is a possible molecular mediator between periodontitis and CAD.

Microbiota Analysis of Biofilms on Experimental Abutments Mimicking Dental Implants: An In Vivo Model

BACKGROUND

The microbiota colonizing dental implants has been said to be similar to the microbiome surrounding teeth. In the absence of inflammation, a biofilm with pathologic bacteria can cover implant surfaces exposed to the oral cavity, for example, due to a remodeling process. The aim of the present study is to identify microbiota surrounding exposed dental implants in patients with and without a history of periodontitis through a deep-sequencing approach.

METHODS

An experimental abutment with the same surface and structure as a commercially available dental implant was used. Bacterial DNA was isolated, and the 16S ribosomal RNA gene was amplified and sequenced. Multiplexed tag-encoded sequencing of DNA from the samples was performed, and the reads were processed by metagenomic rapid annotation.

RESULTS

A wide variety of bacteria, 96 species, were identified. The most frequently found bacteria were Fusobacterium nucleatum and Prevotella denticola. Some species generally associated with periodontitis were found to a greater extent in patients without a history of periodontitis. Some bacteria that have never been described as part of the oral microbiome were identified in the present sample.

CONCLUSIONS

Analysis of data suggests that the bacteria surrounding exposed dental implants form a diverse microbiome regardless of the periodontal profile of patients. Further research is needed to clarify the role of these microorganisms in the oral environment.

The salivary microbiome is altered in the presence of a high salivary glucose concentration

Background

Type II diabetes (T2D) has been associated with changes in oral bacterial diversity and frequency. It is not known whether these changes are part of the etiology of T2D, or one of its effects.

Methods

We measured the glucose concentration, bacterial counts, and relative frequencies of 42 bacterial species in whole saliva samples from 8,173 Kuwaiti adolescents (mean age 10.00 ± 0.67 years) using DNA probe analysis. In addition, clinical data related to obesity, dental caries, and gingivitis were collected. Data were compared between adolescents with high salivary glucose (HSG; glucose concentration ≥ 1.0 mg/d, n = 175) and those with low salivary glucose (LSG, glucose concentration < 0.1 mg/dL n = 2,537).

Results

HSG was associated with dental caries and gingivitis in the study population. The overall salivary bacterial load in saliva decreased with increasing salivary glucose concentration. Under HSG conditions, the bacterial count for 35 (83%) of 42 species was significantly reduced, and relative bacterial frequencies in 27 species (64%) were altered, as compared with LSG conditions. These alterations were stronger predictors of high salivary glucose than measures of oral disease, obesity, sleep or fitness.

Conclusions

HSG was associated with a reduction in overall bacterial load and alterations to many relative bacterial frequencies in saliva when compared with LSG in samples from adolescents. We propose that hyperglycemia due to obesity and/or T2D results in HSG and subsequent acidification of the oral environment, leading to a generalized perturbation in the oral microbiome. This suggests a basis for the observation that hyperglycemia is associated with an increased risk of dental erosion, dental caries, and gingivitis. We conclude that HSG in adolescents may be predicted from salivary microbial diversity or frequency, and that the changes in the oral microbial composition seen in adolescents with developing metabolic disease may the consequence of hyperglycemia.

Dental plaque microbial profiles of children from Khartoum, Sudan, with congenital heart defects

Few studies have focused on the bacterial species associated with the deterioration of the dental and gingival health of children with congenital heart defects (CHD). The aims of this study were (1) to examine the dental plaque of children with CHD in order to quantify bacterial load and altered bacterial composition compared with children without CHD; and (2) to investigate the correlation between the level of caries and gingivitis and dental biofilm bacteria among those children. In this cross-sectional study, participants were children (3-12 years) recruited in Khartoum State, Sudan. A total of 80 CHD cases from the Ahmed Gasim Cardiac Centre and 80 healthy controls from randomly selected schools and kindergartens were included. Participants underwent clinical oral examinations for caries (decayed, missing, and filled teeth indices [DMFT] for primary dentition, and DMFT for permanent dentition), and gingivitis (simplified gingival index [GI]). Pooled dental biofilm samples were obtained from four posterior teeth using paper points. Real-time quantitative polymerase chain reaction was used for the detection and quantification of Streptococcus mutans, Streptococcussanguinis, and Lactobacillus acidophilus. Checkerboard DNA-DNA hybridization was used for the detection of 40 additional bacterial species. CHD cases had a significantly higher caries experience (DMFT = 4.1 vs. 2.3, p < 0.05; DMFT = 1.4 vs. 0.7, p < 0.05) and a higher mean number of examined teeth with gingivitis (4.2 vs. 2.0; p < 0.05) compared with controls. S. mutans counts were significantly higher among the CHD cases (p < 0.05). Checkerboard results revealed that 18/40 bacterial species exhibited significantly higher mean counts among CHD cases (p < 0.01). Correlation analyses revealed that among CHD cases, the detection levels of Tannerella forsythia, Campylobacter rectus, Fusobacterium nucleatum subsp. vincentii, F. nucleatum subsp. nucleatum, and F. nucleatum subsp. polymorphum were highly positively correlated with GI. CHD cases harbor more cariogenic and periodontopathogenic bacterial species in their dental plaque, which correlated with higher levels of caries and gingivitis.

Oral microflora in preschool children attending a fluoride varnish program: a cross-sectional study

Background

To compare the oral microflora in preschool children attending a fluoride varnish program with a reference group receiving a standard oral health program without fluoride varnish applications. A second aim was to relate the microbial composition to the caries prevalence.

Methods

Five hundred seven 3-year-old children were enrolled from a cohort of 3403 preschool children taking part in a community based oral health project. Two hundred sixty-three of them had attended caries-preventive program with semi-annual applications of a fluoride varnish since the age of 1 year (test group) while 237 had received standard preventive care (reference group). Oral samples were collected with a sterile swab and analysed with checkerboard DNA-DNA hybridization using 12 pre-determined bacterial probes. Caries and background data were collected from clinical examinations and questionnaires.

Results

Gram-positive streptococci (S. intermedius, S. salivarius, S. oralis) were most frequently detected and displayed the highest counts in both groups. There were no significant differences between the groups concerning prevalence of any of the selected bacterial strains except for S. oralis that occurred less frequently in the reference group. In children with caries, V. parvula were significantly more common (p < 0.05) while strains of Lactobacillus, Bifidobacterium and Neisseria were more prevalent among the caries-free children (p < 0.05).

Conclusions

A 2-year community program with semi-annual fluoride varnish applications did not seem to significantly influence the oral microflora in preschool children.

Trial registration

www.controlled-trials.com (ISRCTN35086887) 20131216 ‘retrospectively registered’.

Association of Endodontic Lesions with Coronary Artery Disease

An endodontic lesion (EL) is a common manifestation of endodontic infection where Porphyromonas endodontalis is frequently encountered. EL may associate with increased risk for coronary artery disease (CAD) via similar pathways as marginal periodontitis. The aim of this cross-sectional study was to delineate the associations between EL and CAD. Subgingival P. endodontalis, its immune response, and serum lipopolysaccharide were examined as potential mediators between these 2 diseases. The Finnish Parogene study consists of 508 patients (mean age, 62 y) who underwent coronary angiography and extensive clinical and radiographic oral examination. The cardiovascular outcomes included no significant CAD ( n = 123), stable CAD ( n = 184), and acute coronary syndrome (ACS; n = 169). EL was determined from a panoramic tomography. We combined data of widened periapical spaces (WPSs) and apical rarefactions to a score of EL: 1, no EL ( n = 210); 2, ≥1 WPS per 1 apical rarefaction ( n = 222); 3, ≥2 apical rarefactions ( n = 76). Subgingival P. endodontalis was defined by checkerboard DNA-DNA hybridization analysis, and corresponding serum antibodies were determined by ELISA. In our population, 50.4% had WPSs, and 22.8% apical rarefactions. A total of 51.2% of all teeth with apical rarefactions had received endodontic procedures. Subgingival P. endodontalis levels and serum immunoglobulin G were associated with a higher EL score. In the multiadjusted model (age, sex, smoking, diabetes, body mass index, alveolar bone loss, and number of teeth), having WPSs associated with stable CAD (odds ratio [OR] = 1.94, 95% confidence interval [95% CI] = 1.13 to 3.32, P = 0.016) and highest EL score were associated with ACS (OR = 2.46, 95% CI = 1.09 to 5.54, P = 0.030). This association was especially notable in subjects with untreated teeth with apical rarefactions ( n = 59, OR = 2.72, 95% CI = 1.16 to 6.40, P = 0.022). Our findings support the hypothesis that ELs are independently associated with CAD and in particular with ACS. This is of high interest from a public health perspective, considering the high prevalence of ELs and CAD.

Profile of bacteria colonizing the exposed bone of patients with anti-osteoclastic drug-related osteonecrosis of the jaws

Microbial etiology for anti-osteoclastic drug-related osteonecrosis of the jaw (ARONJ) was suggested. This study investigates any link between bacteria colonizing ARONJ sites and other oral cavity sites. Microbiota samples of 10 ARONJ patients were collected from the exposed bone, adjacent teeth, contralateral teeth, and tongue. DNA checkerboard hybridization was used for microbiota analysis with 43 genomic DNA probes prepared from human oral bacterial (38) and candida (5) species, using Socransky's bacterial complexes as a guide. The frequency and the mean proportion of each bacterial species were used. Eikenella corrodens, Streptococcus constellatus, and Fusobacterium nucleatum were dominant in the ARONJ sites and detected in most teeth samples. Staphylococcus aureus was also dominant in the ARONJ sites and tongue. Significant correlations were found between the mean proportions of bacterial species colonizing adjacent teeth, contralateral teeth, and tongue (p < 0.001, R(2) > 0.69). No significant correlation (p > 0.05, R(2) < 0.025) was found between bacteria colonizing ARONJ sites and other evaluated sites. Within the study limitations, it was concluded that the primary sources of microorganisms colonizing ARONJ sites could be other sites such as teeth and tongue. The microbial profile of the necrotic bone is predominantly colonized with bacteria from Socransky's green and orange complexes, as well as with species associated with bone infections.

Microbial Ecosystem Analysis in Root Canal Infections Refractory to Endodontic Treatment

INTRODUCTION

The purpose of this study was to combine multiple displacement amplification and checkerboard DNA-DNA hybridization to qualitatively and quantitatively evaluate the microbiota present in infections refractory to endodontic treatment.

METHODS

The subjects of this study were 40 patients presenting with periapical lesions refractory to endodontic treatment. Samples were taken by scraping or filing root canal walls with a #10 K-type hand file. Sample DNA was amplified by multiple displacement amplification, and the levels of 107 bacterial taxa were analyzed by checkerboard DNA-DNA hybridization. The taxa were divided into 3 distinct microbial populations depending on their mean proportion in samples (% DNA probe counts ± standard error of the mean) as follows: dominant (≥3.0%), subdominant (>1.6%-3.0%), and residual (≤1.6%) populations. The significance of differences was determined using the Mann-Whitney test.

RESULTS

The taxa present with the highest mean proportions (constituting the dominant population) were Corynebacterium diphtheriae (8.03 ± 0.98), Porphyromonas gingivalis (5.42 ± 2.09), Streptococcus sobrinus (5.33 ± 0.69), and Stenotrophomonas maltophilia (4.72 ± 1.73). Among the subdominant population were Eubacterium saphenum (3.85 ± 1.06), Helicobacter pylori (3.16 ± 0.62), Dialister pneumosintes (3.12 ± 1.1), Clostridium difficile (2.74 ± 0.41), Enterobacter agglomerans (2.64 ± 0.54), Salmonella enterica (2.51 ± 0.52), Mobiluncus mulieris (2.44 ± 0.6), and Klebsiella oxytoca (2.32 ± 0.66). In the population of bacteria present at the lowest mean proportions (the residual population), Bacteroides ureolyticus (0.04 ± 0.01), Haemophilus influenzae (0.04 ± 0.02), and Prevotella oris (0.01 ± 0.01) were found at the lowest mean proportions. Enterococcus faecalis was detected in the residual population (0.52 ± 0.26).

CONCLUSIONS

The microbial climax community in teeth refractory to endodontic treatment not only harbors medically important species but also contains distinct microbial consortia present with different population levels.

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.

Microbiological and clinical outcomes of fixed complete-arch mandibular prostheses supported by immediate implants in individuals with history of chronic periodontitis

OBJECTIVES

The aim of this study was to assess the microbiological and clinical outcomes of immediate implants placed in chronically infected sockets for rehabilitation with fixed full-arch mandibular prostheses.

MATERIAL AND METHODS

Fourteen individuals (mean age 60.14 ± 7.69 years) were enrolled in this investigation and followed up until 8 months of function. Microbiological (microbial count and profile) and clinical (probing depth, clinical attachment level, bleeding on probing, and bone resorption) parameters were conducted before teeth extraction (T₀ - baseline) and after 4 (T₁ ) and 8 (T₂ ) months of loading. Thirty-nine microbial species including periodontopathogenic species and Candida spp. were detected and quantified by DNA checkerboard analysis.

RESULTS

Moderate to high levels of pathogenic and non-pathogenic species were found colonizing teeth and implant-related sites. No significant differences in total or individual microbial counts and microbial profile were found over time (P = 0.4929). Probing depth values from teeth (T₀ : 3.05 ± 1.45) were significantly higher when compared with implants (T₁ : 1.81 ± 0.56; T₂ : 1.66 ± 0.53; P < 0.0001). High percentages of bleeding sites were found for both teeth and implants, with the highest values recorded for teeth (P < 0.05). No significant differences were detected comparing marginal bone resorption over time.

CONCLUSIONS

Total and individual counts of target species did not differ between teeth and implants for 8 months of investigation. The mean proportions of pathogenic and non-pathogenic species remained unaltered, and no clinical complications were reported over time. Data obtained suggest that immediate loading of complete mandibular prostheses retained by implants placed immediately after extraction may be a viable treatment option for edentulous individuals with previous history of periodontal disease.

Salivary microflora and mode of delivery: a prospective case control study

Background

Previous cross-sectional studies have suggested that the mode of delivery can influence the composition of oral microflora. The aim of this prospective study was to compare the salivary colonization in vaginally delivered children with children delivered by Caesarian section (C-section) during their first 6 months of life.

Methods

The study group consisted of 149 consecutively enrolled infants, delivered either vaginally (n = 96) or by C-section (n = 53) that volunteered after consent of their parents. Saliva samples were collected within 2 days after birth and then after 1, 3, and 6 months. A saliva sample from the mothers was obtained 6 months after delivery. The parents were asked to complete a questionnaire on socioeconomic factors, lifestyle, and hygiene at baseline and throughout the study period. All samples were analyzed with 13 pre-determined bacterial probes using checkerboard DNA-DNA hybridization.

Results

The groups were balanced at baseline concerning all relevant background factors. Gram-positive streptococci (S. mitis, S. salivarius) displayed the highest counts in both groups but a greater diversity was observed in the vaginally delivered group. A. naeslundi, A. odontolytics, F. nucleatum and L. salivarius were only detected among the vaginally delivered infants. The prevalence of S. sanguinis, S. gordoni, R. denticariosa, and B. dentinum increased by age in both groups but the prevalence was significantly lower in the C-section group (p < 0.05). There was a link between the mothers and their offspring’s concerning the salivary microbial profile.

Conclusion

The microbial composition in saliva differs by the mode of delivery during the first six months of life.

Periodontal Microorganisms and Cardiovascular Risk Markers in Youth With Type 1 Diabetes and Without Diabetes

BACKGROUND

A subset of periodontal microorganisms has been associated with cardiovascular disease (CVD), which is the leading complication of type 1 diabetes (t1DM). The authors therefore evaluated the association between periodontal microorganism groups and early markers of CVD in youth with t1DM.

METHODS

A cross-sectional analysis was conducted among youth aged 12 to 19 years at enrollment; 105 had t1DM for ≥5 years and were seeking care at the Barbara Davis Center, University of Colorado, from 2009 to 2011, and 71 did not have diabetes. Subgingival plaque samples were assessed for counts of 41 periodontal microorganisms using DNA-DNA hybridization. Microorganisms were classified using cluster analysis into four groups named red-orange, orange-green, blue/other, and yellow/other, modified from Socransky's color scheme for periodontal microorganisms. Subsamples (54 with t1DM and 48 without diabetes) also received a periodontal examination at the University of Colorado School of Dental Medicine.

RESULTS

Participants were ≈15 years old on average, and 74% were white. Mean periodontal probing depth was 2 mm (SE 0.02), and 17% had bleeding on probing. In multivariable analyses, glycated hemoglobin (HbA1c) was inversely associated with the yellow/other cluster (microorganisms that are not associated with periodontal disease) among youth with t1DM. Blood pressure, triglycerides, low-density lipoprotein, high-density lipoprotein, and total cholesterol were not associated with microorganism clusters in this group. HbA1c was not associated with periodontal microorganism clusters among youth without diabetes.

CONCLUSION

Among youth with t1DM who had good oral health, periodontal microorganisms were not associated with CVD risk factors.

Microbiology of aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been considered the most likely etiologic agent in aggressive periodontitis. Implementation of DNA-based microbiologic methodologies has considerably improved our understanding of the composition of subgingival biofilms, and advanced open-ended molecular techniques even allow for genome mapping of the whole bacterial spectrum in a sample and characterization of both the cultivable and not-yet-cultivable microbiota associated with periodontal health and disease. Currently, A. actinomycetemcomitans is regarded as a minor component of the resident oral microbiota and as an opportunistic pathogen in some individuals. Its specific JP2 clone, however, shows properties of a true exogenous pathogen and has an important role in the development of aggressive periodontitis in certain populations. Still, limited data exist on the impact of other microbes specifically in aggressive periodontitis. Despite a wide heterogeneity of bacteria, especially in subgingival samples collected from patients, bacteria of the red complex in particular, and those of the orange complex, are considered as potential pathogens in generalized aggressive periodontitis. These types of bacterial findings closely resemble those found for chronic periodontitis, representing a mixed polymicrobial infection without a clear association with any specific microorganism. In aggressive periodontitis, the role of novel and not-yet-cultivable bacteria has not yet been elucidated. There are geographic and ethnic differences in the carriage of periodontitis-associated microorganisms, and they need to be taken into account when comparing study reports on periodontal microbiology in different study populations. In the present review, we provide an overview on the colonization of potential periodontal pathogens in childhood and adolescence, and on specific microorganisms that have been suspected for their role in the initiation and progression of aggressive forms of periodontal disease.

Site-specific treatment outcome in smokers following non-surgical and surgical periodontal therapy

Aim

To evaluate the effect of smoking at patient, tooth, and site level following non‐surgical and surgical periodontal therapy.

Material and Methods

Eighty chronic periodontitis patients, 40 smokers and 40 non‐smokers, were recruited to this single‐arm clinical trial. Smoking status was validated by measuring serum cotinine levels. Periodontal examinations were performed at baseline (T0) and 3 months following non‐surgical and surgical periodontal therapy (T1). At T0 and T1, subgingival plaque samples were collected from the deepest periodontal pocket in each patient and analysed using checkerboard DNA–DNA hybridization. Probing depth (PD) ≥ 5 mm with bleeding on probing (BoP) was defined as the primary outcome. Unadjusted and adjusted logistic regression analyses, corrected for clustered observations within patients and teeth, were conducted comparing smokers with non‐smokers.

Results

Clinical parameters significantly improved in both groups (p < 0.001). An association was revealed between smoking and PD ≥ 5 mm with BoP (OR= 1.90, CI: 1.14, 3.15, p = 0.013), especially for plaque‐positive sites (OR= 4.14, CI: 2.16, 7.96, p < 0.001). A significant reduction of red complex microbiota was observed for non‐smokers only (p = 0.010).

Conclusion

Smokers respond less favourably to non‐surgical and surgical periodontal therapy compared with non‐smokers, in particular at plaque‐positive sites.

Identification and Classification of Rhizobia by Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry

Mass spectrometry (MS) has been widely used for specific, sensitive and rapid analysis of proteins and has shown a high potential for bacterial identification and characterization. Type strains of four species of rhizobia and Escherichia coli DH5α were employed as reference bacteria to optimize various parameters for identification and classification of species of rhizobia by matrix-assisted laser desorption/ionization time-of-flight MS (MALDI TOF MS). The parameters optimized included culture medium states (liquid or solid), bacterial growth phases, colony storage temperature and duration, and protein data processing to enhance the bacterial identification resolution, accuracy and reliability. The medium state had little effects on the mass spectra of protein profiles. A suitable sampling time was between the exponential phase and the stationary phase. Consistent protein mass spectral profiles were observed for E. coli colonies pre-grown for 14 days and rhizobia for 21 days at 4°C or 21°C. A dendrogram of 75 rhizobial strains of 4 genera was constructed based on MALDI TOF mass spectra and the topological patterns agreed well with those in the 16S rDNA phylogenetic tree. The potential of developing a mass spectral database for all rhizobia species was assessed with blind samples. The entire process from sample preparation to accurate identification and classification of species required approximately one hour.

An Overview of Pathogen Recognition Receptors for Innate Immunity in Dental Pulp

Pathogen recognition receptors (PRRs) are a class of germ line-encoded receptors that recognize pathogen-associated molecular patterns (PAMPs). The activation of PRRs is crucial for the initiation of innate immunity, which plays a key role in first-line defense until more specific adaptive immunity is developed. PRRs differ in the signaling cascades and host responses activated by their engagement and in their tissue distribution. Currently identified PRR families are the Toll-like receptors (TLRs), the C-type lectin receptors (CLRs), the nucleotide-binding oligomerization domain-like receptors (NLRs), the retinoic acid-inducible gene-I-like receptors (RLRs), and the AIM2-like receptor (ALR). The environment of the dental pulp is substantially different from that of other tissues of the body. Dental pulp resides in a low compliance root canal system that limits the expansion of pulpal tissues during inflammatory processes. An understanding of the PRRs in dental pulp is important for immunomodulation and hence for developing therapeutic targets in the field of endodontics. Here we comprehensively review recent finding on the PRRs and the mechanisms by which innate immunity is activated. We focus on the PRRs expressed on dental pulp and periapical tissues and their role in dental pulp inflammation.

Salivary IL-1β and red complex bacteria as predictors of the inflammatory status in sub-peri-implant niches of subjects with peri-implant mucositis

BACKGROUND AND OBJECTIVES

Salivary biomarkers may enhance diagnostic sensitivity for peri-implant disease assessment. This study aimed to investigate the association of salivary periodontopathogen count and salivary interleukin-1beta (IL-1β) level with the peri-implant crevicular fluid IL-1β response at peri-implant mucositis (PM) sites among subjects with differing periodontal disease susceptibility.

MATERIALS AND METHODS

Eighty-seven partially edentulous subjects having at least one implant with peri-implant mucositis were included: 40 with history of chronic periodontitis (P) and 47 with no history of periodontitis (NP). Salivary IL-1β, peri-implant crevicular fluid (PICF) IL-1β, and salivary red complex pathogen counts were recorded. Subjects were scored according to a threshold salivary pathogen level of more than 5log (10) counts and assigned a "red complex score." Quartiles of salivary and PICF IL-1β levels were also scored. Area under receiver operating curve (AUC) was computed to predict the highest PICF IL-1β score using salivary biomarker as predictors and age-adjusted logistic regression performed for the significant predictors.

RESULTS

In the NP group, red complex score (AUC = 0.758 P = 0.010) (odds ratio = 1.377) and salivary IL-1β (AUC = 0.708 P = 0.038) (odds ratio = 2.506) were significant predictors of highest PICF IL-1β quartile score. In the P group, no significant associations were noted.

CONCLUSIONS

Salivary biomarkers could distinguish the "high" pro-inflammatory responders at PM sites only in subjects without inherent periodontal disease susceptibility. Periodontal susceptibility may impact the immuno-inflammatory response in sub-peri-implant niches of those with peri-implant mucositis.

A randomized trial of ethyl lauroyl arginate-containing mouthrinse in the control of gingivitis

Aim

This 4‐week, single‐centre, randomized, examiner‐blind, controlled study investigated the efficacy and safety of 0.15% ethyl lauroyl arginate (LAE)‐containing mouthrinse in adults with mild‐to‐moderate gingivitis.

Material and Methods

Subjects were randomized to use 0.15% LAE‐containing mouthrinse or 5% hydroalcohol‐negative control twice daily after brushing with standard fluoride toothpaste. Plaque, gingivitis and bleeding were assessed at baseline and Weeks 2 and 4. The oral microflora was analysed at baseline and Week 4.

Results

Eighty‐seven subjects were randomized to treatment. The 0.15% LAE‐containing mouthrinse was associated with statistically significantly (p < 0.001) greater reductions in mean plaque and gingivitis scores versus the negative control at Week 2 (difference [95% confidence interval]: plaque 0.83 [0.64, 1.02], 29.1%; gingivitis 0.11 [0.07, 0.14], 4.8%) and Week 4 (co‐primary endpoints: plaque 1.23 [1.07, 1.39], 42.6%; gingivitis 0.23 [0.19, 0.28], 10.7%). Bleeding‐index scores were significantly (p < 0.001) reduced versus the control at Weeks 2 (by 0.04 [0.03, 0.06], 36.3%) and 4 (by 0.06 [0.04, 0.08], 50.9%). No shifts were detected in the oral microflora. There were no treatment‐related adverse events.

Conclusions

The 0.15% LAE‐containing mouthrinse was well tolerated and significantly reduced plaque, gingivitis and bleeding when used as an adjunct to tooth brushing for 4 weeks.

Periodontal disease in a remote Asian population: association between clinical and microbiological parameters

OBJECTIVE

The aim was to clinically and microbiologically describe the periodontal conditions in a remote adult Asian population with poor oral hygiene.

METHODS

The subjects were 30-60-year-old adults of Karen Hill tribes with no access to dental care. Eighty-six subjects were selected randomly. Clinical registrations included number of remaining teeth, plaque index (PlI), bleeding on probing (BoP), clinical attachment loss (CAL), and probing pocket depth (PPD). Subgingival plaque samples were collected and analyzed with the checkerboard method.

RESULTS

Subjects of the study group had mean number of remaining teeth of 26.5 despite the abundant plaque and a high bleeding score. Severe periodontitis (CAL ≥ 7 mm) was recorded in 12.9% of the youngest age group (30-39 years) while it was significantly higher (52%) in the middle group (40-49 years) and (60%) in the eldest age group (50-60 years). Pathological pocketing (PPD ≥ 7 mm) was significantly lower in all age groups. Age, betel chewing, and a microbiological cluster including at least one of Prevotella tannerae, Filifactor alocis and Porphyromonas endodontalis significantly correlated with the severity of periodontal disease.

CONCLUSION

Age, betel chewing, and a new bacterial complex other than the "red complex" correlated to periodontal breakdown in this remote adult Asian population.

Genomic identification and quantification of microbial species adhering to toothbrush bristles after disinfection: A cross-over study

PURPOSE

The aim of this clinical investigation was to identify and quantify the microbial species adhering to toothbrush bristles after controlled brushing and storage in different antimicrobial agents.

METHODS

Sixteen healthy participants were enrolled in this study and randomly submitted to 4 interventions in a cross-over design: brushing and toothbrush storage in (I) Periogard/(II) Periobio (Chlorhexidine gluconate 0.12%), (III) Cepacol (cetylpyridinium chloride 0.05%) and (IV) distilled water (positive control). Thirty-eight bacterial species including putative pathogens and 5 Candida spp. were assessed by Checkerboard DNA-DNA hybridization.

RESULTS

The results of the study have shown a striking reduction of the total microbial counts, including bacteria and Candida spp., on the toothbrush bristles after storage in cetylpyridinium chloride 0.05% (p < 0.0001). Chlorhexidine gluconate 0.12% showed no differences on the total bacterial count when compared to distilled water (p > 0.05). Cetylpyridinium chloride solution also presented the lowest genome counts and frequency of detection for individual target species; distilled water showed the highest individual genome counts (p < 0.05). Potential pathogenic species were recorded in moderate to high levels for chlorhexidine gluconate and distilled water.

CONCLUSION

Cetylpyridinium chloride 0.05% was the most effective storage solution in the reduction of total and individual microbial counts, including pathogenic species.

The Peri-Implant and Periodontal Microbiota in Patients with and without Clinical Signs of Inflammation

Late implant failures, caused by the inflammation of surrounding tissues are a problem in implant dentistry. The path of bacterial transmission from teeth to implants is not completely understood. Therefore, the purpose of this study was to analyze intraindividual bacterial transmission characterizing subgingival microbiomes in teeth and implants, both in healthy subjects and in those with signs of periodontitis or peri-implantitis. Samples of peri-implant and dental sulcus fluid were collected. To identify the predominant microbiota, amplified fragments of bacterial 16S rRNA gene were separated by single strand conformation polymorphism analysis, sequenced and taxonomically classified. A total of 25 different predominant genera were found in the diseased group and 14 genera in the healthy group. Species richness did not differ significantly between implants, neighboring teeth and teeth with largest probing depth in the diseased group. Additionally, no differences between teeth and implants in the healthy group were detected. In contrast, microbial diversity varied between the different sampling points. Species richness is similar in healthy and diseased sites, but the composition of the bacterial community differed within the individual subjects. The underlying analyses strongly suggest that complete transmission from neighboring teeth to implants is unlikely.

The effect of blue light on periodontal biofilm growth in vitro

We have previously shown that blue light eliminates the black-pigmented oral bacteria Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, and Prevotella melaninogenica. In the present study, the in vitro photosensitivity of the above black-pigmented microorganisms and four Fusobacteria species (Fusobacterium nucleatum ss. nucleatum, F. nucleatum ss. vincentii, F. nucleatum ss. polymorphum, Fusobacterium periodonticum) was investigated in pure cultures and human dental plaque suspensions. We also tested the hypothesis that phototargeting the above eight key periodontopathogens in plaque-derived biofilms in vitro would control growth within the dental biofilm environment. Cultures of the eight bacteria were exposed to blue light at 455 nm with power density of 80 mW/cm2 and energy fluence of 4.8 J/cm2. High-performance liquid chromatography (HPLC) analysis of bacteria was performed to demonstrate the presence and amounts of porphyrin molecules within microorganisms. Suspensions of human dental plaque bacteria were also exposed once to blue light at 455 nm with power density of 50 mW/cm2 and energy fluence of 12 J/cm2. Microbial biofilms developed from the same plaque were exposed to 455 nm blue light at 50 mW/cm2 once daily for 4 min (12 J/cm2) over a period of 3 days (4 exposures) in order to investigate the cumulative action of phototherapy on the eight photosensitive pathogens as well as on biofilm growth. Bacterial growth was evaluated using the colony-forming unit (CFU) assay. The selective phototargeting of pathogens was studied using whole genomic probes in the checkerboard DNA-DNA format. In cultures, all eight species showed significant growth reduction (p < 0.05). HPLC demonstrated various porphyrin patterns and amounts of porphyrins in bacteria. Following phototherapy, the mean survival fractions were reduced by 28.5 and 48.2% in plaque suspensions and biofilms, respectively, (p < 0.05). DNA probe analysis showed significant reduction in relative abundances of the eight bacteria as a group in plaque suspensions and biofilms. The cumulative blue light treatment suppressed biofilm growth in vitro. This may introduce a new avenue of prophylactic treatment for periodontal diseases.

Effects of azithromycin, metronidazole, amoxicillin, and metronidazole plus amoxicillin on an in vitro polymicrobial subgingival biofilm model

Chronic periodontitis is one of the most prevalent human diseases and is caused by dysbiosis of the subgingival microbiota. Treatment involves primarily mechanical disruption of subgingival biofilms and, in certain cases, adjunctive use of systemic antibiotic therapy. In vitro biofilm models have been developed to study antimicrobial agents targeting subgingival species. However, these models accommodate a limited number of taxa, lack reproducibility, and have low throughput. We aimed to develop an in vitro multispecies biofilm model that mimics subgingival plaque, to test antimicrobial agents. Biofilms were cultivated using the Calgary Biofilm Device and were exposed to amoxicillin (AMX), metronidazole (MTZ), azithromycin (AZM), and AMX-MTZ at four different concentrations for 12, 24, or 36 h. Chlorhexidine (CHX) (0.12%) was used as the positive control. The compositions of the biofilms were analyzed by checkerboard DNA-DNA hybridization, and the percent reduction in biofilm metabolic activity was determined using 2,3,5-triphenyltetrazolium chloride and spectrophotometry. Thirty-five of the 40 species used in the inoculum were consistently recovered from the resulting in vitro biofilms. After 36 h of exposure at the 1:27 dilution, AMX-MTZ reduced metabolic activity 11% less than CHX (q = 0.0207) but 54% more than AMX (q = 0.0031), 72% more than MTZ (q = 0.0031), and 67% more than AZM (q = 0.0008). Preliminary evidence of a synergistic interaction between AMX and MTZ was also observed. In summary, we developed reproducible biofilms with 35 subgingival bacterial species, and our results suggested that the combination of AMX and MTZ had greater antimicrobial effects on these in vitro multispecies biofilms than expected on the basis of the independent effects of the drugs.

Anaerobic culture to detect periodontal and caries pathogens

BACKGROUND

Anaerobic culture has been critical in our understanding of the oral microbiotas.

HIGHLIGHT

Studies in advanced periodontitis in the 1970's revealed microbial complexes that associated with different clinical presentations. Taxonomy studies identified species newly-observed in periodontitis as Aggregatibacter (Actinobacillus) actinomycetemcomitans, Campylobacter (Wolinella) rectus and other Campylobacter species, and Tannerella (Bacteroides) forsythia. Anaerobic culture of initial periodontitis showed overlap in the microbiota with gingivitis, and added Selenomonas noxia and Filifactor alocis as putative periodontal pathogens. Porphyromonas gingivalis and T. forsythia were found to be associated with initial periodontitis in adults. The dominant microbiota of dental caries differs from that of periodontitis. The major cariogenic species are acidogenic and acid tolerant species particularly Streptococcus mutans, and Lactobacillus and Bifidobacterium species. Anaerobic culture of severe early childhood caries revealed a widely diverse microbiota, comparable to that observed using cloning and sequencing. The PCR-based cloning approach, however, underestimated Actinobacteria compared with culture. Only a subset of the caries-associated microbiota was acid tolerant, with different segments of the microbiota cultured on blood agar compared to a low pH acid agar. While the major caries-associated species was S. mutans, a new species, Scardovia wiggsiae, was significantly associated with early childhood caries. Higher counts of S. wiggsiae were also observed in initial white spot carious lesions in adolescents.

CONCLUSION

In periodontitis and dental caries, anaerobic culture studies of advanced disease provided a comprehensive analysis of the microbiota of these infections. Anaerobic culture highlighted the limitation of PCR with standard primers that underestimate detection of Actinobacteria.

Microbial diversity of the supra- and subgingival biofilm of healthy individuals after brushing with chlorhexidine- or silver-coated toothbrush bristles

Nanoparticulate silver has recently been reported as an effective antimicrobial agent. The aim of this clinical study was to investigate the potential changes on the oral microbiota of healthy individuals after controlled brushing with chlorhexidine- or silver-coated toothbrush bristles. Twenty-four healthy participants were enrolled in this investigation and randomly submitted to 3 interventions. All the participants received, in a crossover format, the following toothbrushing interventions: (i) chlorhexidine-coated bristles, (ii) silver-coated bristles, and (iii) conventional toothbrush (Control). All the interventions had a duration of 30 days. The DNA checkerboard hybridization method was used to identify and quantify up to 43 microbial species colonizing the supra- and subgingival biofilm. The supragingival samples presented higher genome counts than the subgingival samples (p < 0.0001). The total genome counts from the Control group showed the highest values, followed by the silver and chlorhexidine groups (p < 0.0001). After 4 weeks of brushing, the silver-coated and chlorhexidine-coated bristles were capable of reducing or maintaining lower levels of the bacterial counts of the putative periodontal pathogens Tanerella forsythia, Treponema denticola, and Porphyromonas gingivalis. Other major periodontal pathogens, such as Prevotella intermedia, Fusobacterium nucleatum, Prevotella nigrescens, and Parvimonas micra, were also detected at lower levels. The toothbrush bristles impregnated with silver nanoparticles reduced the total and individual genome count in the supra- and subgingival biofilm after 4 weeks of brushing. Chlorhexidine was not effective in reducing the total genome counts in both supra- or subgingival biofilm after 4 weeks of brushing. Chlorhexidine reduced the individual genome counts in the supragingival biofilm for most of the target species, including putative periodontal pathogens.

Methodological issues in the quantification of subgingival microorganisms using the checkerboard technique

The reproducibility and reliability of quantitative microbiological assessments using the DNA-DNA hybridization "checkerboard method" (CKB) were assessed. The data originated from 180 chronic periodontitis patients, who were enrolled in a clinical trial and sampled at baseline, and 3 and 12m post-therapy. The samples were divided into two portions allowing evaluation of reproducibility. In total, 531 samples were analyzed in a first run, using standard bacterial preparations of cells and 513 samples were accessible for analysis in the second, using standards based on purified DNA from the species. The microbial probe panel consisted of periodontitis marker bacteria as well as non-oral microorganisms. Three different ways of quantifying and presenting data; the visual scoring method, VSM, the standard curve method, SCM, and the percent method, PM, were compared. The second set of analyses based on the use of standard preparations of pure DNA was shown to be more consistent than the first set using standards based on cells, while the effect of storage time per se up to 2.5y seemed to be marginal. The best reproducibility was found for Tannerella forsythia, irrespective of quantification technique (Spearman's rho=0.587, Pearson's r≥0.540). The percent method (PM) based on percent of High Standard (10(6) cells) was more reliable than SCM based on a linear calibration of the High Standard and a Low Standard (10(5) cells). It was concluded that the reproducibility of the CBK method varied between different bacteria. High quality and pure specific DNA whole genomic probes and standards may have a stronger impact on the precision of the data than storage time and conditions.

Dysbiosis and alterations in predicted functions of the subgingival microbiome in chronic periodontitis

Chronic periodontitis is an inflammatory disease of the periodontium affecting nearly 65 million adults in the United States. Changes in subgingival microbiota have long been associated with chronic periodontitis. Recent culture-independent molecular studies have revealed the immense richness and complexity of oral microbial communities. However, data sets across studies have not been directly compared, and whether the observed microbial variations are consistent across different studies is not known. Here, we used 16S rRNA sequencing to survey the subgingival microbiota in 25 subjects with chronic periodontal disease and 25 healthy controls and compared our data sets with those of three previously reported microbiome studies. Consistent with data from previous studies, our results demonstrate a significantly altered microbial community structure with decreased heterogeneity in periodontal disease. Comparison with data from three previously reported studies revealed that subgingival microbiota clustered by study. However, differences between periodontal health and disease were larger than the technical variations across studies. Using a prediction score and applying five different distance metrics, we observed two predominant clusters. One cluster was driven by Fusobacterium and Porphyromonas and was associated with clinically apparent periodontitis, and the second cluster was dominated by Rothia and Streptococcus in the majority of healthy sites. The predicted functional capabilities of the periodontitis microbiome were significantly altered. Genes involved in bacterial motility, energy metabolism, and lipopolysaccharide biosynthesis were overrepresented in periodontal disease, whereas genes associated with transporters, the phosphotransferase system, transcription factors, amino acid biosynthesis, and glycolysis/gluconeogenesis were enriched in healthy controls. These results demonstrate significant alterations in microbial composition and function in periodontitis and suggest genes and metabolic pathways associated with periodontal disease.

Molecular characterization of Lactobacillus plantarum DMDL 9010, a strain with efficient nitrite degradation capacity

Nitrites commonly found in food, especially in fermented vegetables, are potential carcinogens. Therefore, limiting nitrites in food is critically important for food safety. A Lactobacillus strain (Lactobacillus sp. DMDL 9010) was previously isolated from fermented vegetables by our group, and is not yet fully characterized. A number of phenotypical and genotypical approaches were employed to characterize Lactobacillus sp. DMDL 9010. Its nitrite degradation capacity was compared with four other Lactobacillus strains, including Lactobacillus casei subsp. rhamnosus 719, Lactobacillus delbrueckii subsp. bulgaricu 1.83, Streptococcus thermophilus 1.204, and lactobacillus plantarum 8140, on MRS medium. Compared to these four Lactobacillus strains, Lactobacillus sp. DMDL 9010 had a significantly higher nitrite degradation capacity (P<0.001). Based on 16S rDNA sequencing and sequence comparison, Lactobacillus sp. DMDL 9010 was identified as either Lactobacillus plantarum or Lactobacillus pentosus. To further identify this strain, the flanking regions (922 bp and 806 bp upstream and downstream, respectively) of the L-lactate dehydrogenase 1 (L-ldh1) gene were amplified and sequenced. Lactobacillus sp. DMDL 9010 had 98.92 and 76.98% sequence identity in the upstream region with L. plantarum WCFS1 and L. pentosus IG1, respectively, suggesting that Lactobacillu sp. DMDL 9010 is an L. plantarum strain. It was therefore named L. plantarum DMDL 9010. Our study provides a platform for genetic engineering of L. plantarum DMDL 9010, in order to further improve its nitrite degradation capacity.

Reproducibility of subgingival bacterial samples from patients with peri-implant mucositis

OBJECTIVE

The aim of the present study was to investigate the reproducibility of bacterial enumeration from subsequent subgingival samples collected from patients with peri-implant mucositis.

MATERIAL AND METHODS

Duplicate microbial samples from 222 unique implant sites in 45 adult subjects were collected with paper points and analyzed using the checkerboard DNA-DNA hybridization technique. Whole genomic probes of 74 preselected bacterial species were used. Based on the bacterial scores, Cohen's kappa coefficient was used to calculate the inter-annotator agreement for categorical data. The percentage agreement was considered as "good" when the two samples showed the same score or differed by 1 to the power of 10.

RESULTS

Moderate to fair kappa values were displayed for all bacterial species in the test panel (range 0.21-0.58). There were no significant differences between Gram-positive and Gram-negative species. The percentage of good agreement between the first and second samples averaged 74.7 % (n = 74; range 56-83 %), while the proportion of poor agreement ranged from 1 to 19 % for the various strains.

CONCLUSION

While an acceptable clinical agreement was obtained in most cases, diverging bacterial scores may appear in subgingival samples collected at the same time point from patients with peri-implant mucositis.

CLINICAL RELEVANCE

The broad bulky base of implant crowns may present an obstacle for the collection of reproducible subgingival samples with paper points.

Relation of gelsolin amyloidosis and periodontal health

OBJECTIVE

Hereditary gelsolin amyloidosis (AGel amyloidosis) is a rare, dominantly inherited systemic disease with worldwide distribution, caused by a gelsolin gene mutation. We studied the periodontal conditions and microbiological plaque composition of AGel amyloidosis patients.

MATERIAL AND METHODS

A voluntary study group of 36 AGel amyloidosis patients (mean age 61) filled in a questionnaire. A thorough periodontal examination included periodontal pocket depth and attachment level measurements, registrations of visible plaque, bleeding on probing and panoramic radiographs. The presence of oral Candida was studied by fungal culture method. Bacterial samples from deepened pockets (≥4 mm) were analyzed with checkerboard DNA-DNA hybridization method.

RESULTS

VPI (15.3 %) and BOP (11.2 %) of the patients were modest reflecting relatively adequate oral self-care. Still 89 % of the patients had at least one PPD of ≥4 mm; 78.5 % of the PPDs ≥6 mm were found in molars. Patients had lost one third of the molars due to periodontitis and/or tooth decay. Half of the patients (53 %) were Candida carriers. Bacterial analysis of subgingival plaque samples revealed bacterial species common to chronic periodontitis.

CONCLUSION

AGel amyloidosis may increase the risk for periodontitis even when the oral self-care is adequate. Molar teeth appear to be mostly affected, leading to tooth loss.

CLINICAL RELEVANCE

AGel amyloidosis as a systemic disease is related with a vast variety of symptoms with variable severity. Even though a causal relationship of the systemic disease and periodontitis has not yet been proven, increased risk for periodontal problems should be considered when examining AGel amyloidosis patients.

Bacteria and bacterial DNA in atherosclerotic plaque and aneurysmal wall biopsies from patients with and without periodontitis

Background

Several studies have reported an association between chronic periodontitis (CP) and cardiovascular diseases. Detection of periodontopathogens, including red complex bacteria (RCB), in vascular lesions has suggested these bacteria to be involved in the pathogenesis of atherosclerosis and abdominal aortic aneurysms.

Objective

In this study, we investigate bacteria and their DNA in vascular biopsies from patients with vascular diseases (VD; i.e. abdominal aortic aneurysms, atherosclerotic carotid, and common femoral arteries), with and without CP.

Methods

DNA was extracted from vascular biopsies selected from 40 VD patients: 30 with CP and 10 without CP. The V3-V5 region of the 16S rDNA (V3-V5) was polymerase chain reaction (PCR)-amplified, and the amplicons were cloned into Escherichia coli, sequenced, and classified (GenBank and the Human Oral Microbiome database). Species-specific primers were used for the detection of Porphyromonas gingivalis. In addition, 10 randomly selected vascular biopsies from the CP group were subjected to scanning electron microscopy (SEM) for visualization of bacteria. Checkerboard DNA–DNA hybridization was performed to assess the presence of RCB in 10 randomly selected subgingival plaque samples from CP patients.

Results

A higher load and mean diversity of bacteria were detected in vascular biopsies from VD patients with CP compared to those without CP. Enterobacteriaceae were frequently detected in vascular biopsies together with cultivable, commensal oral, and not-yet-cultured bacterial species. While 70% of the subgingival plaque samples from CP patients showed presence of RCB, only P. gingivalis was detected in one vascular biopsy. Bacterial cells were seen in all 10 vascular biopsies examined by SEM.

Conclusions

A higher bacterial load and more diverse colonization were detected in VD lesions of CP patients as compared to patients without CP. This indicated that a multitude of bacterial species both from the gut and the oral cavity, rather than exclusively periodontopathogens, may be involved as additional risk factors in the pathogenesis of VD.

Subgingival bacteria in Ghanaian adolescents with or without progression of attachment loss

OBJECTIVE

This study describes subgingival bacterial profiles associated with clinical periodontal status in Ghanaian adolescents with or without progression of attachment loss.

MATERIALS AND METHODS

Among 500 adolescents included in a cohort study, 397 returned 2 years later for a periodontal re-examination, including full-mouth CAL measurements. At follow-up, a subgroup of 98 adolescents was also subjected to bacterial sampling with paper points at four periodontal sites (mesial aspect of 11, 26, 31, and 46) and analyzed with the checkerboard DNA-DNA hybridization technique against DNA-probes from nine periodontitis-associated bacterial species.

RESULTS

The 98 Ghanaian adolescents examined in the present study were similar to the entire group examined at the 2-year follow-up with respect to age, gender, and CAL ≥3 mm. A high detection frequency of Fusobacterium nucleatum and Prevotella intermedia (>99%) using checkerboard analysis was found, while for Aggregatibacter actinomycetemcomitans the detection frequency was <50%. A strong correlation was found at the individual level between the presence of P. intermedia and the total CAL change, and P. intermedia and Porphyromonas gingivalis were strongly correlated with a change in CAL and probing pocket depth (PPD) at the sampled sites. In a linear regression model, a significant discriminating factor for the total CAL change in the dentition during the 2-year follow-up period was obtained for P. intermedia and public school.

CONCLUSION

This study indicates that subgingival bacterial species other than A. actinomycetemcomitans, for example, P. intermedia, have a significant association with periodontal breakdown (change in CAL) in Ghanaian adolescents with progression of periodontal attachment loss.

Dental plaque pH and ureolytic activity in children and adults of a low caries population

OBJECTIVES

The aim of this study was to evaluate the plaque pH level and ureolytic activity among children and adults of Karen Hill tribes.

METHODS

Thirty-four children aged 6-10 years and 46 adults aged 20-38 years were interviewed regarding oral hygiene practices, sucrose intake and betel chewing. Caries experience (DMFT and DT), calculus, bleeding on probing (BoP) and Plaque index (PlI) were registered. Ureolytic activity in supragingival plaque was tested at two interproximal sites (11/12 and 41/42) with the rapid urease test (RUT). Registration of plaque pH was performed at two interproximal sites (15/16 and 31/41) before, during and 30 min after rinsing with an urea solution (0.25%). Four interproximal plaque samples (one from each quadrant) per individual were collected to test the bacterial composition using the checkerboard technique.

RESULTS

Children and adults had similarly low DMFT and DT values. Children had a higher baseline pH and a higher ureolytic activity in the maxilla (p < 0.05) compared with adults. A significant correlation (r (2) = 0.63) was found between baseline pH and urease activity in the mandibular anterior teeth. Caries-free individuals had a higher baseline pH compared with caries active individuals in the anterior mandibular region (p < 0.01). The microbiological composition was characterized by an anaerobic low acidiogenic microbiota.

CONCLUSIONS

Dental plaque pH is related to the ureolytic activity, which explains the low acidogenic plaque microflora and the low caries levels in the Karen population.

Lessons learned and unlearned in periodontal microbiology

Periodontal diseases are initiated by bacterial species living in polymicrobial biofilms at or below the gingival margin and progress largely as a result of the inflammation elicited by specific subgingival species. In the past few decades, efforts to understand the periodontal microbiota have led to an exponential increase in information about biofilms associated with periodontal health and disease. In fact, the oral microbiota is one of the best-characterized microbiomes that colonize the human body. Despite this increased knowledge, one has to ask if our fundamental concepts of the etiology and pathogenesis of periodontal diseases have really changed. In this article we will review how our comprehension of the structure and function of the subgingival microbiota has evolved over the years in search of lessons learned and unlearned in periodontal microbiology. More specifically, this review focuses on: (i) how the data obtained through molecular techniques have impacted our knowledge of the etiology of periodontal infections; (ii) the potential role of viruses in the etiopathogenesis of periodontal diseases; (iii) how concepts of microbial ecology have expanded our understanding of host-microbe interactions that might lead to periodontal diseases; (iv) the role of inflammation in the pathogenesis of periodontal diseases; and (v) the impact of these evolving concepts on therapeutic and preventive strategies to periodontal infections. We will conclude by reviewing how novel systems-biology approaches promise to unravel new details of the pathogenesis of periodontal diseases and hopefully lead to a better understanding of their mechanisms.

Diagnosis and anti-infective therapy of periodontitis

Periodontal diseases (gingivitis and periodontitis) are chronic bacterial infections with a remarkably high prevalence and morbidity. Periodontitis, in contrast to gingivitis, is not reversible, is associated with certain bacterial species and affects all of the soft tissue and bone that support teeth. Among the periodontal pathogens, species, such as Aggregatibacter (Actinobacillus) actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and several forms of uncultivable spirochetes play the major role in the pathogenesis. In severe chronic, recurrent and especially aggressive forms of periodontitis, diagnosis of the species involved and, whenever possible, an optimized evidence-based antimicrobial treatment is indicated. In order to monitor alarming bacterial changes in the periodontal pocket, several techniques, namely microscopy, culture, immunoassays, enzyme tests and DNA-based techniques, have been established and the methods are described in the first part of this review. In the second part, the selection and use of locally delivered (topical) and systemic antibiotics used adjunctively in periodontal therapy are discussed.