[Temporomandibular dysfunction and bruxism in patients with early rheumatoid arthritis and at-risk patients: a cross-sectional study]. / Temporomandibulaire disfunctie en bruxisme bij patiënten met vroege reumatoïde artritis en risicopatiënten: een cross-sectioneel onderzoek.

What is the prevalence of temporomandibular dysfunction in patients with early rheumatoid arthritis and individuals at risk of rheumatoid arthritis? 3 groups (of 50 participants each) were examined for a possible TMD diagnosis: 1. patients with early rheumatoid arthritis, 2. at-risk individuals, and 3. healthy controls. A possible association with bruxism, determined on the basis of self-reporting and clinical features, was also examined. At-risk patients had a higher prevalence of TMD pain diagnoses compared to healthy controls (p = 0.046). Within the early rheumatoid arthritis group, seronegative patients had a higher prevalence of TMD pain diagnoses than seropositive patients (p = 0.048). No further differences in the prevalence of TMD diagnoses were found between the groups. Participants with a TMD pain diagnosis were more often diagnosed with probable sleep bruxism than those without a TMD pain diagnosis. The prevalence of TMD pain is increased in individuals at risk of rheumatoid arthritis and seronegative early rheumatoid arthritis patients, and is associated with signs of bruxism.

Reactive oxygen species can be traced locally and systemically in apical periodontitis: A systematic review.

OBJECTIVES: The aim of this systematic review was to summarize the existing evidence on the local production and systemic traces of reactive oxygen species (ROS) in apical periodontitis (AP). DESIGN: A search of MEDLINE-PubMed and EMBASE was conducted up to January 12 of 2021 to identify studies in 6 different languages. Eligibility was evaluated and data were extracted from the eligible studies following the predefined objective. The Newcastle-Ottawa Scale was used for quality assessment of the included studies. RESULTS: After screening, 21 papers met the inclusion criteria. Six studies were about systemic oxidative stress, 14 studies examined local production of reactive oxygen species and one studied both. ROS modulate cell signalling and cause oxidant imbalance locally at the site of AP. Cell signalling leads to a pro-inflammatory response, activation of MMPs and formation and progression of the AP lesion. Simultaneously, these oxidative stress biomarkers are also found in blood and saliva of subjects with AP. CONCLUSIONS: Understanding the mechanism of ROS generation, involved in chronic inflammation, can provide us with important information to enhance local and systemic healing and possibly improve diagnostic tools. Future research considerations would be to use antioxidants to accelerate the return to oxidative balance.

[Cross contamination: spatters, aerosols, and biofilm in dental practices]. / Kruiscontaminatie: spatten, aerosolen en biofilm in de mondzorgpraktijk.

During treatment in dental practices, drops of different sizes are produced (spats and aerosols). Microorganisms in these drops are of human origin or originate from the water in the dental unit. Therefore, these drops can contribute to cross contamination in dental practices. Large drops settle quickly, while smaller drops can remain suspended in the air for a longer period of time. The highest level of contamination is found in the immediate vicinity of the source (the patient's mouth). Further away from the source and after stopping drop producing activities, the level of contamination in the air is comparable to control circumstances. Studies into the spread of viruses via this route in the dental practice have not yet been conducted. The risk of catching an infectious disease in the dental practice seems limited, but can be high in the case of a virulent microorganism, when the circumstances for spread of the virus are favorable, or if the recipient is immunocompromised.

The influence of apical periodontitis on the concentration of inflammatory mediators in peripheral blood plasma and the metagenomic profiling of endodontic infections: Study design and protocol.

Increased systemic inflammation has been identified in presence of oral disease, specifically endodontic disease. It is important to investigate whether treatment of the oral disease ameliorates systemic inflammation. Furthermore, there is no information about the extent to which different microorganisms may trigger inflammatory response. OBJECTIVES: Primarily (i) to compare the plasma concentrations of inflammatory mediators of apical periodontitis (AP) subjects to controls, (ii) to evaluate whether elimination of the endodontic infection reduces systemic inflammation (iii) to investigate the microbiome of root canal infections. Secondarily i) to correlate the inflammatory mediator data with the microbiome data to investigate whether the type of infection influences the type and severity of the inflammatory condition ii) to examine patterns in the inflammatory mediator data before and after tooth extraction in order to establish a biomarker signature of AP/oral disease.This is a multi-centre prospective case-control intervention study. The cohort will consist of 30 healthy human volunteers with one or two teeth with a root-tip inflammation and 30 matched healthy controls. Peripheral blood will be drawn at 6 time points, 3 before and 3 after the extraction of the tooth with apical periodontitis. The teeth will be pulverized, DNA extraction and sequencing will be performed.This study aims to compare the concentration of inflammatory blood plasma proteins in between AP-subjects and controls at different time points before and after the tooth extraction in a systematic and complete way. Additionally the composition of the root canal microbiome in association with the inflammatory response of the host will be assessed.

Subgingival Microbiota during Healthy Pregnancy and Pregnancy Gingivitis.

INTRODUCTION: Previous studies have largely explored the microbial composition and pathogenesis of pregnancy gingivitis. However, the patterns of microbial colonization during pregnancy in the absence of pregnancy gingivitis have rarely been studied. Characterization of the oral microbiome in pregnant women with healthy gingiva is an important initial step in understanding the role of the microbiome in progression to pregnancy gingivitis. OBJECTIVES: In this study, we compared the oral microbiome of pregnant women without gingivitis (healthy pregnancy) with pregnant women having gingivitis and nonpregnant healthy women to understand how pregnancy modifies the oral microbiome and induces progression to pregnancy gingivitis. METHODS: Subgingival plaque samples were collected from Chinese pregnant women with gingivitis (n = 10), healthy pregnant women (n = 10), and nonpregnant healthy women (n = 10). The Illumina MiSeq platform was used to perform 16S rRNA gene sequencing targeting the V4 region. RESULTS: The alpha and beta diversity was significantly different between pregnant and nonpregnant women, but minimal differences were observed between pregnant women with and without gingivitis. Interestingly, the oral bacterial community showed higher abundance of pathogenic taxa during healthy pregnancy as compared with nonpregnant women despite similar gingival and plaque index scores. However, when compared with overt pregnancy gingivitis, pathogenic taxa were less abundant during healthy pregnancy. PICRUSt analysis (phylogenetic investigation of communities by reconstruction of unobserved states) also suggested no difference in the functional capabilities of the microbiome during pregnancy, irrespective of gingival disease status. However, metabolic pathways related to amino acid metabolism were significantly increased in healthy pregnant women as compared with nonpregnant women. CONCLUSION: The presence of pathogenic taxa in healthy pregnancy and pregnancy gingivitis suggests that bacteria may be necessary for initiating disease development but progression to gingivitis may be influenced by the host environmental factors. More efforts are required to plan interventions aimed at sustaining health before the appearance of overt gingivitis. KNOWLEDGE TRANSFER STATEMENT: The results of this study draw attention to the importance of oral health maintenance during pregnancy, as women without any prenatal oral conditions are predisposed to the risk of developing pregnancy gingivitis. Hence, it is important to incorporate comprehensive assessment of oral health in the prenatal health care schedules. Pregnant woman should be screened for oral risks, counseled on proper oral hygiene and expected oral changes, and referred for dental treatment, when necessary.

Home sampling is a feasible method for oral microbiota analysis for infants and mothers.

OBJECTIVES: Large longitudinal cohort studies in infants are needed to understand oral microbiome maturation in relation to general health. The logistics of such studies are complex and costs involved high. Methods like home sampling by caretakers might be a solution to these issues. This study aimed to evaluate feasibility of home sampling by caretakers and to assess which oral niche provides the most reliable sample. METHODS: In this cross-sectional study 30 mothers and their infants aged 2-15 months participated. Swabs of the tongue, buccal mucosa, saliva, and dental plaque of the mother and the infant were collected by the mother after watching an instruction video. Thereafter, the trained researcher repeated the sample collection. Variations on the sampling protocol were listed. Bacterial DNA was quantified and microbial composition was assessed using 16S rDNA amplicon sequencing. RESULTS: None of the sampled niches appeared to be unfeasible based on interviews and observed variations on protocol. No significant differences in bacterial DNA concentration between operators (mother and researcher) were found. In infant's saliva, Shannon diversity of samples collected by the researcher was significantly higher than those collected by mothers (p = 0.0009) and the bacterial composition was influenced by variations on sampling protocol (p = 0.01). CONCLUSIONS: Home sampling by caretakers is a feasible method for oral sample collection in infants and mothers. Oral samples collected by mothers resemble samples collected by a trained researcher, with the tongue sample being the most similar and saliva the least. CLINICAL SIGNIFICANCE: Home sampling can simplify longitudinal oral microbiota collection.

Modeling of the Transmission of Coronaviruses, Measles Virus, Influenza Virus, Mycobacterium tuberculosis, and Legionella pneumophila in Dental Clinics.

Dental health care workers are in close contact to their patients and are therefore at higher risk for contracting airborne infectious diseases. The transmission rates of airborne pathogens from patient to dental health care workers are unknown. With the outbreaks of infectious diseases, such as seasonal influenza, occasional outbreaks of measles and tuberculosis, and the current pandemic of the coronavirus disease COVID-19, it is important to estimate the risks for dental health care workers. Therefore, the transmission probability of these airborne infectious diseases was estimated via mathematical modeling. The transmission probability was modeled for Mycobacterium tuberculosis, Legionella pneumophila, measles virus, influenza virus, and coronaviruses per a modified version of the Wells-Riley equation. This equation incorporated the indoor air quality by using carbon dioxide as a proxy and added the respiratory protection rate from medical face masks and N95 respirators. Scenario-specific analyses, uncertainty analyses, and sensitivity analyses were run to produce probability rates. A high transmission probability was characterized by high patient infectiousness, the absence of respiratory protection, and poor indoor air quality. The highest transmission probabilities were estimated for measles virus (100%), coronaviruses (99.4%), influenza virus (89.4%), and M. tuberculosis (84.0%). The low-risk scenario leads to transmission probabilities of 4.5% for measles virus and 0% for the other pathogens. From the sensitivity analysis, it shows that the transmission probability is strongly driven by indoor air quality, followed by patient infectiousness, and the least by respiratory protection from medical face mask use. Airborne infection transmission of pathogens such as measles virus and coronaviruses is likely to occur in the dental practice. The risk magnitude, however, is highly dependent on specific conditions in each dental clinic. Improved indoor air quality by ventilation, which reduces carbon dioxide, is the most important factor that will either strongly increase or decrease the probability of the transmission of a pathogen.

Dental aerosols: microbial composition and spatial distribution.

Background: High-speed dental instruments produce aerosols, which can contribute to the transmission of pathogenic microorganisms. The aim of this study is to describe the microbial load and - composition and spatial distribution of aerosols in dental clinics. Methods: In four dental clinics active and passive sampling methods were used before, during and after treatment and at different locations. Retrieved colony forming units (CFU) were sequenced for taxon identification. Results: The samples contained up to 655 CFU/plate/30 minutes and 418 CFU/m3/30 minutes during dental treatment for active and passive sampling, respectively. The level of contamination after treatment and at 1.5 m distance from the patient's head was similar to the start of the day. The highest contamination was found at the patient's chest area. The aerosols consisted of 52 different taxa from human origin and 36 from water. Conclusion: Contamination in dental clinics due to aerosols is mainly low, although high level of contamination with taxa from both human and water origin was found within 80 cm around the head of the patient. Our results stress the importance of infection control measures on surfaces in close proximity to the head of the patient as well as in dental water lines.

Heterogeneity in the efficacy of dental chemical disinfectants on water-derived biofilms in vitro.

Conditions in dental unit waterlines are favourable for biofilm growth and contamination of dental unit water. The aim of this study was to assess the effect of several chemical disinfectants on bacteria in a biofilm model. Water-derived biofilms were grown in a static biofilm model (Amsterdam Active Attachment model), using two growth media. Biofilms were challenged with Alpron/Bilpron, Anoxyl, Citrisil, Dentosept, Green & Clean, ICX and Oxygenal in shock dose and maintenance doses. The concentration and the composition of the chemical disinfectants influenced the number of culturable bacteria in the biofilms. The application of a single shock dose followed by a low dose of the same chemical disinfectants resulted in the greatest suppression of viable bacteria in the biofilms. Exposure to Citrisil and ICX consistently resulted in failure to control the biofilms, while Alpron/Bilpron had a substantial and relevant effect on the number of bacteria in the biofilms.

Temporomandibular joint function, periodontal health, and oral microbiome in early rheumatoid arthritis and at-risk individuals: a prospective cohort study protocol.

OBJECTIVES/AIMS: Rheumatoid arthritis (RA) is an autoimmune disease affecting the joints, including the temporomandibular joint (TMJ). Early diagnosis and treatment can alleviate symptoms and prevent progression. Predictors for disease outcome in individuals at risk for RA are therefore valuable. While limited information is available on the prevalence of TMJ involvement in early RA, previous studies suggest that RA, periodontitis and the oral microbiome are interrelated. Predictive factors for RA development may thus be present in the oral cavity. Our two aims are: (1) to assess the prevalence of TMJ involvement in early RA, and (2) to investigate the predictive value of oral factors in RA development. MATERIALS AND METHODS: We will include 150 individuals in this multi-center, prospective cohort study: 50 patients with early RA, 50 at-risk individuals, and 50 healthy controls. At baseline, the TMJ, periodontal health, and the oral microbiome will be examined. The general health will be followed over time, on four occasions up to 3 years. DISCUSSION: Our results will provide insight into the prevalence and clinical characterization of TMJ involvement in early RA. For at-risk individuals, oral factors can be studied as possible predictors for the development of RA.

Long-term impact of oral surgery with or without amoxicillin on the oral microbiome-A prospective cohort study.

Routine postoperative antibiotic prophylaxis is not recommended for third molar extractions. However, amoxicillin still continues to be used customarily in several clinical practices worldwide to prevent infections. A prospective cohort study was conducted in cohorts who underwent third molar extractions with (group EA, n = 20) or without (group E, n = 20) amoxicillin (250 mg three times daily for 5 days). Further, a control group without amoxicillin and extractions (group C, n = 17) was included. Salivary samples were collected at baseline, 1-, 2-, 3-, 4-weeks and 3 months to assess the bacterial shift and antibiotic resistance gene changes employing 16S rRNA gene sequencing (Illumina-Miseq) and quantitative polymerase chain reaction. A further 6-month follow-up was performed for groups E and EA. Seven operational taxonomic units reported a significant change from baseline to 3 months for group EA (adjusted p < 0.05). No significant change in relative abundance of bacteria and ß-lactamase resistance genes (TEM-1) was observed over 6 months for any group (adjusted p > 0.05). In conclusion, the salivary microbiome is resilient to an antibiotic challenge by a low-dose regimen of amoxicillin. Further studies evaluating the effect of routinely used higher dose regimens of amoxicillin on gram-negative bacteria and antibiotic resistance genes are warranted.

Bifidobacterium breve as a delivery vector of IL-24 gene therapy for head and neck squamous cell carcinoma in vivo.

Beneficial bacteria are becoming ever more popular gene delivery method for hypoxia-tumor targeting in vivo. In this study we investigated the therapeutic effect of new recombinant Bifidobacterium breve strain expressing interleukin (IL)-24 gene (B. breve-IL24) on head and neck tumor xenograft in mice. Briefly, B. breve transformants were obtained through electro-transformation. Bacteria-tumor-targeting ability were analyzed in vivo over different time points (1, 3 and 7 days post-bacteria injection). Furthermore, the therapeutic effect of bacteria on tumor cells in vivo were analyzed as follows: 30 Balb/c nude mice bearing subcutaneous tumor were randomly divided in three groups (Drug group, green fluorescent protein (GFP) group and Saline group). The therapy lasted for 2 weeks and included B. breve-IL24 administration via tail vein for Drug group, B. breve-GFP for GFP group and phosphate buffered saline for Saline group. The tumor growth was monitored using standard caliper technique, while the apoptosis induction in vivo was analyzed by Real-time Positron Emission Tomography/Computed Tomography (PET/CT) imaging ([18F]-ML-10 tracer). At the end of the experiment, tumor tissues were collected and analyzed by western blotting. Briefly, our results suggested that our new recombinant bacterium has the capability of targeting tumor tissue in vivo. As for the therapeutic effect, our new strain has revealed to be a promising therapeutic approach against tumor growth in vivo. Briefly, higher tumor growth inhibition and higher tumor cell apoptosis induction were observed in Drug group compared with the GFP and Saline groups. To conclude, a new recombinant strain B. breve-IL24 offers a novel, safe and clinically acceptable therapeutic approach for tumor therapy in vivo.

A reproducible microcosm biofilm model of subgingival microbial communities.

OBJECTIVE: To develop a reproducible subgingival microcosm biofilm model. MATERIAL AND METHODS: Subgingival plaque samples were collected from four deep pockets (probing pocket depth ≥6 mm) in each of seven patients with periodontitis and from shallow pockets (probing pocket depth ≤3 mm) in two periodontally healthy donors. An active attachment model and a peptone medium (Thompson et. al., Appl Environ Microbiol 2015;81:8307-8314) supplemented with 30% serum was used. Biofilms were harvested at 2 and 4 weeks. DNA of dead cells was blocked for amplification by propidium monoazide treatment. Composition was analyzed using 16S rRNA gene amplicon pyrosequencing. Similarities between the biofilm samples were assessed by non-metric multidimensional scaling using the Bray-Curtis similarity index and similarity percentage analysis. Data from duplicate experiments, different biofilm sources and different biofilm age were compared. RESULTS: The non-metric multidimensional scaling revealed a strong clustering by the inoculum source, the donor and their periodontal status. Statistically significant differences were found between the sources of inoculum (P=.0001) and biofilm age (P=.0016). Furthermore, periodontitis biofilms (P) were distinct in composition from health-derived biofilms (H) by genera: Porphyromonas (P=19%; H=0%), Filifactor (P=10%; H=0%), Anaeroglobus (P=3%; H=0%), Phocaeicola (P=1.5%; H=0%), Parvimonas (P=19%; H=14%), Fusobacterium (P=2%; H=26%), Peptostreptococcus (P=20%; H=30%), Veillonella (P=7%; H=8%) and 57 other genera. Similarity distances (Bray-Curtis) (mean 0.73, SD 0.15) and the Shannon diversity index (mean 2, SD 0.2) revealed no differences between duplicate experiments (P=.121). CONCLUSION: This biofilm model allows reproducible production of complex subgingival microbial communities.

Candida albicans alters the bacterial microbiome of early in vitro oral biofilms.

The yeast Candida albicans is an oral commensal microorganism, occurring in the oral cavity of 50-70% of healthy individuals. Its effect on oral ecology has mostly been studied using dual-species models, which disregards the complex nature of oral biofilms. The aim of this study was to culture C. albicans in a complex model to study its effect on oral biofilms. Biofilms, inoculated using pooled stimulated saliva with or without addition of C. albicans, were grown under anaerobic, aerobic, or aerobic +5% CO2 conditions. Red autofluorescence was quantified using a spectrophotometer and visualized in fluorescence photographs. The microbiome of 5 h biofilms was determined using 16S rDNA sequencing. C. albicans was only able to proliferate in biofilms grown under aerobic conditions. After 48 h, C. albicans did not induce differences in total biofilm formation, lactic acid accumulation (cariogenic phenotype) or protease activity (periodontitis phenotype). In vitro, anaerobically grown biofilms developed red autofluorescence, irrespective of inoculum. However, under aerobic conditions, only C. albicans-containing biofilms showed red autofluorescence. Facultative or strict anaerobic Veillonella, Prevotella, Leptotrichia, and Fusobacterium genera were significantly more abundant in biofilms with C. albicans. Biofilms without C. albicans contained more of the aerobic and facultative anaerobic genera Neisseria, Rothia, and Streptococcus. The presence of C. albicans alters the bacterial microbiome in early in vitro oral biofilms, resulting in the presence of strictly anaerobic bacteria under oxygen-rich conditions. This in vitro study illustrates that C. albicans should not be disregarded in healthy oral ecosystems, as it has the potential to influence bacteria significantly.

Prevalence and nature of fungi in root canal infections: a systematic review and meta-analysis.

The role of bacteria in causing apical periodontitis has been widely established, whilst the role of other microorganisms is studied less thoroughly. This systematic review and meta-analysis reviewed the literature for the prevalence and diversity of fungi in root canal infections. An extensive literature search was carried out in the Cochrane databases, EMBASE, MEDLINE, LILACS, SciELO and Web of Science. Additional studies were identified from six endodontic journals, four main endodontic textbooks and references of relevant papers. Selected clinical studies included sampling of necrotic pulps in permanent teeth and microbial analysis of these samples. Studies were critically appraised using the Joanna Briggs Institute Prevalence Critical Appraisal Checklist. Meta-analysis was performed using MetaXL. The screening of 1041 titles and abstracts and full-text reading yielded 54 studies. The overall prevalence of fungi in root canal infections was 7.5% (CI 95%: 3.6-11.8%) in the inverse variance fixed effect heterogeneity model. Candida albicans was the most frequently isolated species. Significant heterogeneity was observed (P < 0.001, I2  = 85.04%). Subgroup analyses based on geographical location, period of publication, type of infection, state of general health, communication with the oral cavity, type of sample and identification method revealed no factor influencing the prevalence. Better standardized techniques and a comprehensive analysis will reveal a more detailed and accurate representation of the prevalence and nature of fungi in root canal infections.

Diffusion of antimicrobials in multispecies biofilms evaluated in a new biofilm model.

AIM: To describe the application of a newly-developed in vitro model in which the diffusion of antimicrobials in oral biofilms can be studied. METHODOLOGY: In a flow chamber consisting of three parallel feeding channels connected with each other by eight perpendicular side channels, multispecies biofilms were grown from saliva of a single donor for 48 h. The dimensions of the side channels were 100 µm × 100 µm × 5130 µm (H × W × L). When one or more side channels were filled with biofilm, the biofilms were stained with fluorescent stains. Then, one side-channel biofilm was selected and treated with phosphate buffered saline, 2% sodium hypochlorite (NaOCl), 17% ethylenediaminetetra-acetic acid (EDTA) or modified salt solution (MSS). Diffusion of the irrigants was observed by acquiring fluorescence images at 10× objective every 15 s for 30 min. RESULTS: It was possible to culture biofilms in the narrow (100 µm) channels. The biofilms varied in phenotype. In this model, no diffusion of NaOCl into the biofilms was seen after its application. Seventeen-percentage EDTA only diffused into the biofilm up to 200 µm in 30 min. MSS did diffuse in the biofilm over a distance of 450 µm within 2 min after a single application. CONCLUSIONS: This new model enables the investigation of the diffusion of antimicrobials in biofilms. Other applications to improve our understanding of the characteristics of biofilms are now possible.

Caries Incidence in a Healthy Young Adult Population in Relation to Diet.

In the past, epidemiological studies focused on cavitated stages of caries. The arrival of the International Caries Detection and Assessment System (ICDAS) in 2004 allowed for clinical measurements of the initial stages of enamel caries. However, since the introduction, most studies applying the ICDAS still have studied the diseased population. The objective of this cross-sectional observational study was to describe early enamel caries in a large healthy young adult population and determine the relationship with diet and oral hygiene measures. The study population consisted of 268 healthy participants without frank cavitation. The examinations were done visually and radiographically using ICDAS on all tooth surfaces. In total, 8.6% of the surfaces (occlusal > approximal > smooth) had caries, of which 92.0% were confined to enamel (28.5% ICDAS score 1, 54.0% score 2, 8.6% score 3). Thirteen percent of the occlusal and 63% of the approximal caries were found with radiography. Thus, radiography is quintessential for the diagnosis of approximal enamel lesions. We found a positive correlation between enamel caries (ICDAS 1 to 3) and the consumption of mono- and disaccharides and carbohydrates ( r = 0.226 and r = 0.188, respectively, both P < 0.01), as well as a negative correlation with alcohol consumption ( r = -0.202, P < 0.01). There was also a positive correlation between enamel caries and the energy intake from mono- and disaccharides (sugar kJ, r = 0.206, P < 0.01), which was independent of body mass index. Only 11 participants consumed less than 10% of total energy as sugar kJ, which is the recommended percentage of kJ from free sugar by the World Health Organization. No clear correlation was found with oral hygiene. In conclusion, in this healthy young adult population, caries was found in 97.8% of the subjects, mostly initial enamel caries (ICDAS 1 to 2) in the occlusal surface of molars, and was related with dietary factors.

Microbial profiles at baseline and not the use of antibiotics determine the clinical outcome of the treatment of chronic periodontitis.

Antibiotics are often used in the treatment of chronic periodontitis, which is a major cause of tooth loss. However, evidence in favour of a microbial indication for the prescription of antibiotics is lacking, which may increase the risk of the possible indiscriminate use of antibiotics, and consequent, microbial resistance. Here, using an open-ended technique, we report the changes in the subgingival microbiome up to one year post-treatment of patients treated with basic periodontal therapy with or without antibiotics. Antibiotics resulted in a greater influence on the microbiome 3 months after therapy, but this difference disappeared at 6 months. Greater microbial diversity, specific taxa and certain microbial co-occurrences at baseline and not the use of antibiotics predicted better clinical treatment outcomes. Our results demonstrate the predictive value of specific subgingival bacterial profiles for the decision to prescribe antibiotics in the treatment of periodontitis, but they also indicate the need for alternative therapies based on ecological approaches.

In mixed biofilms Enterococcus faecalis benefits from a calcium hydroxide challenge and culturing.

AIM: To evaluate the fate of Enterococcus faecalis in dual-species and multispecies biofilms after treatment with calcium hydroxide (Ca(OH)2 ). METHODOLOGY: Biofilms were cultured from laboratory strains of E. faecalis and Pseudomonas aeruginosa, or from microbiota retrieved from primary root canal infections. The biofilms were then treated with Ca(OH)2 . The proportion of E. faecalis and P. aeruginosa and their susceptibility to disinfection were evaluated in a viability assay. In the mixed-species assay, the presence and proportions of E. faecalis before and after Ca(OH)2 treatment were evaluated with a quantitative polymerase chain reaction assay. Groups were compared using Mann-Whitney U-test and Student's t-tests. An α <0.05 was considered statistically significant. RESULTS: After Ca(OH)2 treatment in dual-species biofilms, the proportion of E. faecalis had increased (P < 0.001), whereas the total number of CFUs per biofilm was equal. Enterococcus faecalis was equally susceptible to disinfection by sodium hypochlorite (NaOCl) or by chlorhexidine. Pseudomonas aeruginosa had become more susceptible to NaOCl disinfection. The root canal isolates contained no detectable amounts of E. faecalis. After biofilm culturing or Ca(OH)2 treatment, it appeared that E. faecalis must have been present in 5 of 6 (83%) root canal samples. CONCLUSIONS: Calcium hydroxide favours the population of E. faecalis in a dual-species biofilm. Culturing multispecies root canal isolates makes E. faecalis detectable. E. faecalis was often present in primary endodontic infections, albeit in low numbers.

Does apical periodontitis have systemic consequences? The need for well-planned and carefully conducted clinical studies.

Apical periodontitis, infection of the root canal system, may have systemic consequences. This proposal has been brought forward many times in dentistry literature but the general consensus is that there is no scientific basis for an association between endodontic infections and general health. This opinion paper argues that, in order to obtain such a scientific basis, or to rule out the issue all together, we need carefully designed longitudinal challenge model (that is, intervention) studies in which we follow specific biomarkers of inflammation. These biomarkers can be those that are currently being substantiated in chronic inflammation and low-grade inflammation studies in medicine and nutritional science, where the presence of these inflammatory disorders is linked to systemic outcomes. A list of suggested biomarkers has been included.