Oral-to-rectum microbial transmission in orthopedic patients without a history of intestinal disorders.

The enrichment of oral taxa in the gut has recently been reported as a notable alteration in the microbial balance in patients with intestinal disorders. However, translocation in populations without such diseases remains controversial. In this study, we examined 49 pairs of tongue and rectal samples collected from orthopedic patients without a history of intestinal disorders to verify the presence of oral taxa in the rectal microbiota. The bacterial composition of each sample was determined using 16S rRNA gene sequencing and amplicon sequence variant (ASV) analysis. Although the bacterial compositions of the tongue and rectal microbiota were distinctly different, tongue ASVs were detected in 67.3% of the participants and accounted for 0.0%-9.37% of the rectal microbiota. Particularly, Streptococcus salivarius, Fusobacterium nucleatum, and Streptococcus parasanguinis were abundant in the rectal microbiota. According to the network analysis, tongue taxa, such as S. salivarius and S. parasanguinis, formed a cohabiting group with Klebsiella pneumoniae and Alistipes finegoldii in the rectal microbiota. The total abundance of tongue ASVs in the rectal microbiota was significantly higher in participants with older age, hypertension, and proton pump inhibitor (PPI) use. Our study presents an extensive translocation of oral taxa to the rectum of a population without intestinal disorders and suggests that aging, hypertension, and PPI use are associated with an increased abundance of oral taxa and potential pathogenic bacteria in the rectal microbiota.

Establishment of tongue microbiota by 18 months of age and determinants of its microbial profile.

IMPORTANCE: Understanding the development of oral microbiota early in life and the factors that influence it is important for preventing the establishment of dysbiotic oral microbiota later in life. This study demonstrates that the tongue microbiota undergoes early development from 4 to 18 months of age and converges into two types of microbiota showing indications of adult characteristics, with either S. salivarius or Neisseria-dominance. Interestingly, their divergence was strongly determined by their weaning status and the dietary frequencies of sweetened beverages, snacks, and fruits, suggesting that dietary habits during this period might influence the establishment of the oral microbiota. These findings may contribute to the development of novel preventive strategies against oral microbiota-related diseases.

Longitudinal association between periodontal condition and glycaemic status in middle-aged adults: A cross-lagged panel analysis.

AIM: To investigate the existence of a bidirectional temporal relationship between periodontal condition and glycaemic status. MATERIALS AND METHODS: This longitudinal study included 2198 participants with mean age 43.4 ± 7.7 years, who underwent dental examinations in Yokohama, Japan, at two time points, 2003-2004 and 2008-2009, at an interval of 5 years. Periodontal condition was assessed by the mean value of probing pocket depth (PPD) and clinical attachment level (CAL). Glycaemic status was assessed by fasting glucose and glycated haemoglobin (HbA1c). RESULTS: The cross-lagged panel models showed the effect of HbA1c at baseline on mean PPD at follow-up (ß = 0.044, p = .039). There was a marginal effect of fasting glucose on the mean PPD (ß = 0.037, p = .059). It was similar to the effect of fasting glucose or HbAlc on mean CAL. However, in the opposite direction, no effect of mean PPD or CAL at baseline on fasting glucose or HbAlc at follow-up was identified. CONCLUSIONS: This study demonstrated a unidirectional relationship between glycaemic status and periodontal condition. The study population, however, had mostly mild periodontitis. Future studies are needed to investigate the effect of periodontal condition on glycaemic status in patients with severe periodontitis.

Association of second-hand smoke exposure, quantified by salivary cotinine, with dental caries in Japanese adolescents.

PURPOSE: Second-hand smoke has adverse effects on oral health. This cohort study used a multilevel approach to investigate the association of second-hand smoke exposure, as determined by salivary cotinine level, with dental caries in adolescents. METHODS: Data from 75 adolescents aged 11 or 12 years and 2,061 teeth without dental caries were analyzed in this study. Annual dental examinations to assess dental caries were conducted between 2018 and 2021. Salivary cotinine and Dentocult SM-Strip level were measured at baseline. Information on the smoking habits of parents, snack frequency, regular dental visits, and use of fluoride toothpaste was collected at baseline from parent-reported questionnaires. RESULTS: During the 3-year follow-up, dental caries was noted in 21 adolescents and 43 teeth. Participants exposed to parental smoking had higher salivary cotinine levels than those whose parents did not smoke. The multilevel Cox regression model showed that a high salivary cotinine level was associated with the incidence of dental caries, after adjusting for potential confounding factors (hazard ratio, 3.39; 95% confidence interval 1.08-10.69). CONCLUSION: This study suggests that the risk of dental caries is higher for adolescents who have high salivary cotinine levels attributable to second-hand smoke exposure.

Butyrate as a Potential Driver of a Dysbiotic Shift of the Tongue Microbiota.

The tongue dorsum is colonized by a stable microbiota, mostly comprising common commensal taxa. However, the predominance of each taxon varies among individuals. We hypothesized that equilibrium in the tongue microbiota is affected by exposure to butyrate in the oral fluid, which is reported to affect the growth of specific microorganisms. In this study, the bacterial composition of the tongue microbiotas of 69 male adults was determined via 16S rRNA gene sequencing to investigate its relationship to n-butyric acid concentration in oral rinse samples. The tongue microbiotas of individuals with a higher n-butyric acid level had higher relative abundances of Prevotella histicola, Veillonella atypica, and Streptococcus parasanguinis and lower relative abundances of Neisseria subflava and Porphyromonas pasteri. Subsequently, tongue microbiota samples collected from 12 adults were cultivated for 13 h in basal medium containing mucin and different concentrations of sodium butyrate (0, 0.8, 1.6, and 3.2 mM) to assess its effect on the growth of tongue microbiota organisms. The bacterial composition of the cultivated tongue microbiotas also demonstrated a significant gradual shift with an increase in sodium butyrate levels in beta-diversity analysis. N. subflava was significantly less predominant in the microbiota after cultivation with an increased addition of sodium butyrate, although no statistical difference was observed in the other aforementioned taxa. These results suggest that butyrate in the oral fluid is partially involved in the dysbiotic shift of the tongue microbiota. IMPORTANCE Oral microbial populations that are always ingested with saliva have attracted increasing attention because more oral microorganisms than previously known reach distal organs, such as the lungs and intestinal tract, thereby affecting our health. However, although such organisms are predominately derived from the tongue dorsum, the dynamics and determinants of the tongue microbiota composition remain unclear. This study demonstrated that exposure to butyrate could lead to a dysbiotic shift in the tongue microbiota using an observational epidemiological and microbiota cultivation approach. This result adds a new dimension to tongue microbiota ecology.

Yogurt product intake and reduction of tooth loss risk in a Japanese community.

AIM: To evaluate the longitudinal association between yogurt product intake and oral health in a population-based study. MATERIALS AND METHODS: This study included 1967 Japanese residents aged 40-79 years who underwent dental examinations in 2012. Among them, 1469 participants were followed up in 2017 for the incidence of tooth loss, which was defined as two or more teeth lost over 5 years. The intake of yogurt products, defined as yogurt and lactic acid beverages, was estimated using a semi-quantitative food frequency questionnaire. The composition of the salivary microbiota was evaluated. RESULTS: The Poisson regression model showed that a higher intake of yogurt products was negatively associated with the incidence of tooth loss (p for trend = .020), adjusted for potential confounding factors. Mediation analysis confirmed that periodontal condition partly mediated the effect of yogurt product intake on tooth loss, while dental caries experience did not. Additionally, we confirmed the association of a high intake of yogurt products with a low percentage of the salivary microbiota pattern, which was associated with poor oral health. CONCLUSION: These findings suggest that the intake of yogurt products is associated with a lower risk of tooth loss resulting from periodontal disease, probably via modulation of the oral microbiome composition.

High-Level Acquisition of Maternal Oral Bacteria in Formula-Fed Infant Oral Microbiota.

The influx of maternal oral microbes is considered to play an important role in the acquisition and development of infant oral microbiota. In this study, we examined tongue swab samples from 448 mother-infant pairs at 4-month checkups. The bacterial composition of each sample was determined using PacBio single-molecule long-read sequencing of the full-length 16S rRNA gene and the amplicon sequence variant (ASV) approach. Although the infant oral microbiota was distinctly different from the mother oral microbiota, ASVs shared with their biological mother accounted for a median relative abundance of 9.7% (range of 0.0 to 99.3%), which was significantly higher than that of ASVs shared with unrelated mothers. This shared abundance was strongly associated with the feeding method of infants rather than their delivery mode or antibiotic exposure, and formula-fed infants had higher shared abundance than exclusively breastfed infants. Our study presents strain-level evidence for mother-to-infant transmission of oral bacteria and suggests that colonization of maternal oral bacteria is higher in formula-fed infants. IMPORTANCE Acquisition of oral bacteria during infancy can affect the subsequent formation of stable oral microbiota. This study focused on the mother-to-infant transmission of oral bacteria, a major acquisition route of infant oral microbiota, and demonstrated that most infants acquired oral bacteria from their biological mother even at the single-nucleotide level. Our results also indicated that the occupancies of maternal oral bacteria in infant oral microbiota were associated with the feeding methods of infants. These data could increase understanding of the early development of oral microbiota in infants and its potential associations with oral microbiota-related diseases.

Baseline periodontal status and modifiable risk factors are associated with tooth loss over a 10-year period: Estimates of population attributable risk in a Japanese community.

BACKGROUND: This study aimed to examine whether modifiable risk factors can predict tooth loss over 10 years and estimate population attributable risk (PAR) for a combination of modifiable factors. METHODS: This longitudinal study included 1466 participants who underwent dental examinations in 2007 and 2017 and were aged 40 to 79 years at baseline. Periodontal conditions were assessed using the 2018 periodontal classification. Incident tooth loss was defined as ≥4 teeth lost over a 10-year period. We calculated the partial PAR (pPAR%) for tooth loss to estimate the combined effect of modifiable risk factors. RESULTS: Incidence of tooth loss was 17.5%. Directed acyclic graphs were used to identify risk factors for tooth loss. A logistic regression model showed that baseline periodontitis, dental caries experience, no regular dental visit, periodontal treatment, smoking, and obesity were associated with tooth loss after adjusting for covariates; pPAR% was 55.5% (95% confidence interval: 31.1% to 73.0%) in periodontitis Stage III to IV and 87.6% (50.4% to 97.4%) in the combination of all factors, respectively. The sex-stratified analysis showed that smoking and no regular dental visit in men and obesity in women were identified as potential risk factors for tooth loss. CONCLUSIONS: Modifiable factors accounted for most cases of incident tooth loss. Risk factors for tooth loss might differ by sex, suggesting that the appropriate approach for preventing tooth loss base on sex.

Dataset to evaluate the geology, metamorphic conditions and pseudosection modeling of the Luswishi Dome, Copperbelt, Zambia.

This Data in Brief article presents methods used to acquire and process the data presented and discussed in a research paper co-submitted to the Journal of African Earth Sciences titled: "Comparative geology and metamorphic evolution of the Luswishi Dome, Copperbelt, Zambia: Implications for exploration targeting." [1]. The dataset includes geographical coordinates, lithological logs of drill holes, rock and mineral chemistry data, and pseudosections. The dataset is hosted in the Mendeley Data repository in relevant sub-folders as supplementary data to the research paper. In order to provide spatial context for the study area map, geographical coordinates and collar information of the studied drill holes obtained from secondary sources are also provided in tabular form. Lithological logs summarize physical characteristics of lithological observations made on drill core. Rock chemistry data were obtained by fusion X-ray fluorescence, XRF (outsourced to the Actlabs, Canada), and mineral chemistry data were obtained by electron probe microanalyzer, EPMA, model JXA-8800R at Hokkaido University in Japan. Pseudosections were computed using Perple_X 6.8.6 software, as a function of rock compositions, temperature and pressure following the methods outlined in the online Perple_X documentation files available on the developer's website. The data maybe of potential use for improving our understanding of the geology, geochemical characteristics, and metamorphic conditions of the study area, with potential to inform further research and explorations works in the Dome's region of the Lufilian Arc.

10-year trend of tooth loss and associated factors in a Japanese population-based longitudinal study.

OBJECTIVES: We examined the trend in the number of missing teeth in a Japanese community over a 10-year period and the potential associated explanatory factors. DESIGN: Prospective cohort study. SETTING: A population-based study conducted in 2007, 2012 and 2017 in Japan (Hisayama Study). PARTICIPANTS: Residents of a Japanese community aged 40-79 years undergoing dental examination in 2007 (n=2665), 2012 (n=2325) and 2017 (n=2285). OUTCOME MEASURES: The number of missing teeth, periodontal condition, dental caries experience, dental plaque index and oral health behaviours were evaluated each year. The longitudinal analysis of variation in these factors were assessed using mixed models. RESULTS: The age-adjusted and sex-adjusted mean number of missing teeth decreased with time (6.80 in 2007, 6.01 in 2012 and 4.99 in 2017). The mean clinical attachment level (CAL), prevalence of periodontitis and dental plaque index decreased over the study period, while dental caries experience slightly increased. The level of oral health behaviour increased over time. Poisson mixed models showed that changes in mean CAL and dental caries experience were positively associated with the change in the number of missing teeth over time. Linear mixed models showed that changes in dental plaque index and no regular dental visit were positively associated with changes in mean CAL. CONCLUSIONS: These findings suggest that a decreasing trend regarding the number of missing teeth in Japan might be associated with improvements in the periodontal condition due to changes in oral hygiene level and oral health behaviour.

Clinical utility of subgingival plaque-specific bacteria in salivary microbiota for detecting periodontitis.

Saliva contains diverse bacteria shed from various oral sites, including subgingival plaque. It is reasonable to focus on the total occupancy of subgingival plaque-specific bacteria (SUBP bacteria), which live in subgingival environments, in the saliva for detecting periodontitis using salivary testing. This study aimed to validate the clinical utility of SUBP bacteria in the salivary microbiota for the detection of periodontitis. We examined stimulated saliva samples collected from 125 subjects who visited three dental clinics. The relative abundances of previously identified 11 SUBP bacteria were determined using 16S ribosomal RNA gene sequencing and a reference-based approach. The prediction performance was evaluated using a receiver operating characteristic (ROC) curve. The SUBP bacteria accounted for 0-15.4% of the salivary microbiota, and the percentage distinguished periodontitis patients with at least 15 sites with probing depth ≥4 mm with a sensitivity of 0.90 (95% confidence interval [CI], 0.81-0.98) and specificity of 0.70 (95% CI, 0.60-0.80) (area under the ROC curve [AUC], 0.87). Among 2,047 combinations of 11 SUBP bacteria, combinations including Streptococcus constellatus, Porphyromonas gingivalis, and Fusobacterium nucleatum subsp. vincentii demonstrated significantly higher AUC values in their detection. These results suggest that examining SUBP bacteria in saliva may be useful for detecting periodontitis patients in mass screening.

Airflow limitation and tongue microbiota in community-dwelling elderly individuals.

Numerous oral indigenous microorganisms are constantly introduced into the stomach via the laryngopharynx, and a portion of these microorganisms irregularly reaches the lower airways and lungs. This study investigated the association between airflow limitation and the status of tongue microbiota, which is a primary source of ingested oral bacterial populations. The study population consisted of 484 community-dwelling adults aged 70-80 years inhabiting Hisayama town, Japan, who underwent a regular health examination including dental examination and spirometry test in 2016. The bacterial density and composition of their tongue microbiota were determined using a previously used 16S rRNA gene to understand their relationship with oral health conditions. The present cross-sectional study compared the tongue microbiota status between elderly individuals with airflow limitation and those with normal airflow. The total bacterial density of the tongue microbiota of individuals with airflow limitation was significantly higher than that of individuals with normal airflow. Logistic regression analysis demonstrated that a high-biomass tongue microbiota was significantly associated with airflow limitation after adjustment for smoking intensity and other covariates (adjusted OR 1.61, 95% CI 1.01-2.60). Of the predominant commensals, higher amounts of Prevotella melaninogenica and Actinomyces odontolyticus were associated with a higher prevalence of airflow limitation. These results indicate that increased bacterial burden in the tongue microbiota is associated with a higher prevalence of airflow limitation.

Tongue Microbiota Composition and Dental Caries Experience in Primary School Children.

The tongue microbiota of elderly adults is composed of two cohabiting commensal groups and their ratios are related to the number of teeth with dental caries experience. In this study, the variation in the tongue microbiota of primary school children and its relationship with the dental caries experience were investigated. We examined the tongue microbiota of 138 children aged 6 to 7 years and 11 to 12 years (61 and 77 children, respectively) who underwent annual dental examinations. The bacterial composition was determined by sequencing the V1-V2 region of the 16S rRNA gene. Cooccurrence network analysis indicated two groups of cohabiting predominant commensals in the tongue microbiota of children. The microbiota in children without a history of dental caries showed significantly higher relative abundances of one of the cohabiting groups, primarily composed of Neisseria subflava, Porphyromonas pasteri, and Fusobacterium periodonticum, compared to that in children with a history of dental caries, which is consistent with that of elderly adults with fewer teeth with dental caries experience. Linear discriminant analysis effect size (LEfSe) further identified Streptococcus oralis subsp. dentisani, belonging to the aforementioned commensal group, as a discriminant species in children without dental caries experience aged 6 to 7 years and 11 to 12 years. Our results describe the tongue microbiota composition of primary school children without history of dental caries and support the possibility that dental caries experience is accompanied by a shift in the tongue microbiota.IMPORTANCE Dental caries is now considered to be caused by acids produced by the overall dental plaque microbiota rather than by specific pathogens. This study focused on the relationship between dental caries experience and the variations in tongue microbiota, which is adjacent but separate from the dental plaque microbiota. Our results demonstrated that the tongue microbiota of primary school children with no history of dental caries experience was composed of predominant commensals with different relative abundances compared to those present in children with dental caries experience, suggesting that dental caries experience is accompanied by a shift in the tongue microbiota. The maintenance of a healthy tongue microbiota may indirectly contribute to the prevention of dental caries.

Association between periodontitis and fibrotic progression of non-alcoholic fatty liver among Japanese adults.

AIM: Non-alcoholic fatty liver (NAFL) is known to develop into liver fibrosis, which increases the risk of liver cirrhosis and liver cancer. The association between periodontal condition and fibrotic progression of NAFL is unclear. This study aimed to clarify this longitudinal association. MATERIALS AND METHODS: Among 4812 participants aged 35-64 years undergoing annual health check-ups between 2003 and 2004, and follow-up 5 years later, 392 participants were diagnosed with NAFL. After excluding participants with liver fibrosis at baseline, 341 participants were followed up for 5 years. NAFL disease fibrosis score of ≥-1.455 was used to evaluate the probability of the presence of liver fibrosis. RESULTS: During the follow-up period, 10.6% of participants progressed to liver fibrosis. A higher clinical attachment level (CAL) tended to be associated with the incidence of liver fibrosis in the logistic regression analysis (odds ratio [OR] 1.82, 95% confidence interval [CI], 0.94-3.49, p = .074). The stratified analysis by obesity revealed a significant association with higher CAL in obese participants (OR 2.87, 95% CI, 1.23-6.69, p = .015), but not in non-obese participants. CONCLUSION: Higher CAL was associated with an increased probability of liver fibrosis in obese adults with NAFL.

Compositional Shift of Oral Microbiota Following Surgical Resection of Tongue Cancer.

Salivary microbiota is considered a source of microorganisms for the respiratory and digestive tracts, and a trigger for diseases in these distant organs. Meanwhile, the microbiota on the tongue surface is thought to be a major source of salivary microbiota. Therefore, surgical resection of the tongue for definitive treatment of oral cancer could drastically change the salivary bacterial balance and virulence. Here, we investigated the shift of the salivary microbiota following surgical resection in patients with tongue cancer. The stimulated saliva samples were collected from 25 tongue cancer patients pre- and post-resection of the tongue, and bacterial density and composition was determined using quantitative PCR analysis and 16S ribosomal RNA (rRNA) gene sequencing, respectively. Although no significant difference in the total bacterial density in saliva pre- and post-surgery was observed, the bacterial composition significantly differed according to the analysis of similarity. Among predominant operational taxonomic units (OTUs) with ≥1% of relative abundance, the proportions of OTUs corresponding to Streptococcus salivarius, Prevotellamelaninogenica, and Prevotellahisticola were significantly decreased following the tongue resection. On the other hand, the proportions of OTUs corresponding to Lautropiamirabilis, Neisseriaflava, Streptococcussanguinis, and Fusobacterium nucleatum, known to be inhabitants of dental plaque, were significantly increased. These results suggest that surgical resection of the tongue causes a compositional shift of the salivary microbiota, characterized by an increase in bacterial species derived from dental plaque, including periodontal pathogens. These results suggest the necessity of more careful and frequent postoperative oral care after surgical resection of tongue cancer.

Effect of Calcium Chloride Hydrothermal Treatment of Titanium on Protein, Cellular, and Bacterial Adhesion Properties.

Topographical modification of the dental implant surface is one of the main topics for the improvement of the material, however, the roughened surface has some risks for peri-implantitis. A hydrothermal treatment (HT) of titanium with calcium chloride solution was reported to improve osseointegration and soft tissue sealing without changing the surface topography; however, its mechanism is unclear. We herewith investigated the interaction between extracellular matrix (ECM) protein and HT titanium. Furthermore, we also clarified the bacterial interaction. We employed two kinds of HT, HT with water (DW-HT) and HT with calcium chloride solution (Ca-HT). As a result, the adsorptions of both laminin-332 and osteopontin onto the Ca-HT surface were enhanced. In contrast, the adsorption of albumin, which was reported to have no cell adhesion capacity, was not influenced by Ca-HT. Osteoblast adhesion onto Ca-HT was also enhanced. Although Ca-HT was reported to enhance both epithelial cell attachment strength and in vivo peri-implant epithelial bonding, the number of epithelial cell attachment was not increased even after HT. Ca-HT had no impact in the adhesion of Streptococcus gordonii. These results suggest that Ca-HT enhances cell adhesion onto titanium without increasing bacterial adhesion, and the improvement of ECM protein adsorption is supposed to contribute to cell adhesion.

Effects of eradication of Helicobacter pylori on oral malodor and the oral environment: a single-center observational study.

OBJECTIVE: Although a relationship between Helicobacter pylori and oral malodor has been suggested, it remains to be confirmed. One reason for this is that many studies assess oral malodor subjectively. Another reason for the uncertainty is that the reduction in oral malodor may be due to the effect of antibiotics on the oral microbiota. In this study, changes in oral malodor along with the eradication treatment of H. pylori were investigated by organoleptic test and gas chromatography. In addition, the salivary bacterial composition and clinical parameters were analyzed. RESULTS: The organoleptic test score, hydrogen sulfide and dimethyl sulfide concentrations, and all clinical parameters except for tongue-coating score were significantly decreased at 1 week compared with baseline. Although antibiotic treatment also altered the overall composition of the salivary bacterial population, it had recovered at 7 weeks. On the date that H. pylori was determined to have been eradicated from all of the subjects (7 weeks after treatment), only the organoleptic test score was significantly lower compared with baseline. The hydrogen sulfide and dimethyl sulfide concentrations were non-significantly lower than those at baseline.

Disrupted tongue microbiota and detection of nonindigenous bacteria on the day of allogeneic hematopoietic stem cell transplantation.

Disruption of the intestinal microbiota caused by intensive chemotherapy, irradiation and antibiotics can result in development of severe gut graft-versus-host disease and infectious complications, leading to poorer outcomes among allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Although the oral cavity is also densely colonized by indigenous microorganisms, the bacterial composition in allo-HSCT recipients remains unclear. We determined the tongue microbiota composition of 45 patients with hematological disorders on the day of transplantation and compared them to 164 community-dwelling adults. The V1-V2 regions of the 16S rRNA gene sequences demonstrated that the allo-HSCT recipients had less diverse and distinct microbiota from that of community-dwelling adults. The full-length 16S rRNA gene sequences identified 146 bacterial taxa in the microbiota of allo-HSCT recipients, of which 34 bacterial taxa did not correspond to bacteria primarily inhabiting the oral cavity deposited in the expanded Human Oral Microbiome Database. Notably, the detection of Staphylococcus haemolyticus and/or Ralstonia pickettii was significantly associated with a higher risk of mortality during the follow-up period. These results demonstrate that the oral cavity of allo-HSCT recipients is colonized by a disrupted microbiota on the day of transplantation and suggest that detection of specific nonindigenous taxa could be a predictor of transplant outcome.

Longitudinal Associations of Toothbrushing With Obesity and Hyperglycemia.

BACKGROUND: Toothbrushing is a health-related lifestyle habit and has been reported to contribute not only to oral health but also to some parameters of general health; however, little research has been conducted to understand the association of the frequency and timing of toothbrushing with the development of comprehensive metabolic abnormalities, with consideration of oral health condition. In this study, using longitudinal data, we examined this association in Japanese adults, adjusting for periodontal condition. METHODS: A 5-year longitudinal study was performed with 4,537 participants between 35 and 64 years old who underwent an annual dental examination in both 2003 and 2008. Data about toothbrushing habits and metabolic abnormalities, such as obesity, hyperglycemia, diabetes, hypertension, hypertriglyceridemia, and low levels of high-density lipoprotein-cholesterol, were analyzed using Poisson regression analysis. RESULTS: The percentage of participants with a toothbrushing frequency ≤1 time/day was 29.4%, and that for those not brushing their teeth at night was 21.4%. The incidences of obesity and hyperglycemia after 5 years were 5.5% and 28.4%, respectively. A toothbrushing frequency ≤1 time/day was associated with development of obesity (prevalence rate ratio [PRR] 1.77; 95% confidence interval [CI], 1.12-2.80), after adjusting for periodontal condition and potential risk factors. A significant association between not brushing teeth at night and hyperglycemia (PRR 1.30; 95% CI, 1.02-1.66) was observed in participants with toothbrushing frequency of 1 time/day. No association was found between toothbrushing habits and other metabolic abnormalities. CONCLUSIONS: This study suggests that toothbrushing habits are associated with the development of obesity and hyperglycemia.

Identification of Initial Colonizing Bacteria in Dental Plaques from Young Adults Using Full-Length 16S rRNA Gene Sequencing.

Development of dental plaque begins with the adhesion of salivary bacteria to the acquired pellicle covering the tooth surface. In this study, we collected in vivo dental plaque formed on hydroxyapatite disks for 6 h from 74 young adults and identified initial colonizing taxa based on full-length 16S rRNA gene sequences. A long-read, single-molecule sequencer, PacBio Sequel, provided 100,109 high-quality full-length 16S rRNA gene sequence reads from the early plaque microbiota, which were assigned to 90 oral bacterial taxa. The microbiota obtained from every individual mostly comprised the 21 predominant taxa with the maximum relative abundance of over 10% (95.8 ± 6.2%, mean ± SD), which included Streptococcus species as well as nonstreptococcal species. A hierarchical cluster analysis of their relative abundance distribution suggested three major patterns of microbiota compositions: a Streptococcus mitis/Streptococcus sp. HMT-423-dominant profile, a Neisseria sicca/Neisseria flava/Neisseria mucosa-dominant profile, and a complex profile with high diversity. No notable variations in the community structures were associated with the dental caries status, although the total bacterial amounts were larger in the subjects with a high number of caries-experienced teeth (≥8) than in those with no or a low number of caries-experienced teeth. Our results revealed the bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults.IMPORTANCE Selective attachment of salivary bacteria to the tooth surface is an initial and repetitive phase in dental plaque development. We employed full-length 16S rRNA gene sequence analysis with a high taxonomic resolution using a third-generation sequencer, PacBio Sequel, to determine the bacterial composition during early plaque formation in 74 young adults accurately and in detail. The results revealed 21 bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults, which include several streptococcal species as well as nonstreptococcal species, such as Neisseria sicca/N flava/N mucosa and Rothia dentocariosa Given that no notable variations in the microbiota composition were associated with the dental caries status, the maturation process, rather than the specific bacterial species that are the initial colonizers, is likely to play an important role in the development of dysbiotic microbiota associated with dental caries.