Bacterial Composition and Metabolomics of Dental Plaque From Adolescents

Metabolomics for dental caries diagnosis: Past, present, and future

Dental caries, a prevalent global infectious condition affecting over 95% of adults, remains elusive in its precise etiology. Addressing the complex dynamics of caries demands a thorough exploration of taxonomic, potential, active, and encoded functions within the oral ecosystem. Metabolomic profiling emerges as a crucial tool, offering immediate insights into microecosystem physiology and linking directly to the phenotype. Identified metabolites, indicative of caries status, play a pivotal role in unraveling the metabolic processes underlying the disease. Despite challenges in metabolite variability, the use of metabolomics, particularly via mass spectrometry and nuclear magnetic resonance spectroscopy, holds promise in caries research. This review comprehensively examines metabolomics in caries prevention, diagnosis, and treatment, highlighting distinct metabolite expression patterns and their associations with disease-related bacterial communities. Pioneering in approach, it integrates singular and combinatory metabolomics methodologies, diverse biofluids, and study designs, critically evaluating prior limitations while offering expert insights for future investigations. By synthesizing existing knowledge, this review significantly advances our comprehension of caries, providing a foundation for improved prevention and treatment strategies.

Oral microbiota of adolescents with dental caries: A systematic review

OBJECTIVE

This systematic review summarizes the current knowledge on the association between the oral microbiota and dental caries in adolescents.

DESIGN

An electronic search was carried out across five databases. Studies were included if they conducted research on generally healthy adolescents, applied molecular-based microbiological analyses and assessed caries status. Data extraction was performed by two reviewers and the Newcastle-Ottawa Scale was applied for quality assessment.

RESULTS

In total, 3935 records were reviewed which resulted in a selection of 20 cross-sectional studies (published 2005-2022) with a sample size ranging from 11 to 614 participants including adolescents between 11 and 19 years. The studies analyzed saliva, dental biofilm or tongue swabs with Checkerboard DNA-DNA hybridization, (q)PCR or Next-Generation Sequencing methods. Prevotella denticola, Scardoviae Wiggsiae, Streptococcus sobrinus and Streptococcus mutans were the most frequently reported species presenting higher abundance in adolescents with caries. The majority of the studies reported that the microbial diversity was similar between participants with and without dental caries.

CONCLUSION

This systematic review is the first that shows how the oral microbiota composition in adolescents appears to differ between those with and without dental caries, suggesting certain taxa may be associated with increased caries risk. However, there is a need to replicate and expand these findings in larger, longitudinal studies that also focus on caries severity and take adolescent-specific factors into account.

Oral microbial signatures associated with age and frailty in Canadian adults

This study aimed to assess the association between the oral microbiome, age, and frailty. Data and saliva samples were obtained from male and female participants aged 35-70 years (n = 1357). Saliva samples were analysed by 16S rRNA gene sequencing and differences in microbial diversity and community compositions were examined in relation to chronological age and the frailty index (FI). Most alpha diversity measures (Richness, Shannon Diversity, Faith's Phylogenetic Diversity) showed an inverse association with frailty, whereas a positive association was observed with age and Shannon Diversity and Evenness. A further sex-stratified analysis revealed differences in measures of microbial diversity and composition. Multiple genera were detected as significantly differentially abundant with increasing frailty and age by at least two methods. With age, the relative abundance of Veillonella was reduced in both males and females, whereas increases in Corynebacterium appeared specific to males and Aggregatibacter, Fusobacterium, Neisseria, Stomatobaculum, and Porphyromonas specific to females. Beta diversity was significantly associated with multiple mental health components of the FI. This study shows age and frailty are differentially associated with measures of microbial diversity and composition, suggesting the oral microbiome may be a useful indicator of increased risk of frailty or a potential target for improving health in ageing adults.

Understanding the influence of the microbiome on childhood infections

INTRODUCTION

The microbiome is known to have a substantial impact on human health and disease. However, the impacts of the microbiome on immune system development, susceptibility to infectious diseases, and vaccine-elicited immune responses are emerging areas of interest.

AREAS COVERED

In this review, we provide an overview of development of the microbiome during childhood. We highlight available data suggesting that the microbiome is critical to maturation of the immune system and modifies susceptibility to a variety of infections during childhood and adolescence, including respiratory tract infections, Clostridioides difficile infection, and sexually transmitted infections. We discuss currently available and investigational therapeutics that have the potential to modify the microbiome to prevent or treat infections among children. Finally, we review the accumulating evidence that the gut microbiome influences vaccine-elicited immune responses among children.

EXPERT OPINION

Recent advances in sequencing technologies have led to an explosion of studies associating the human microbiome with the risk and severity of infectious diseases. As our knowledge of the extent to which the microbiome influences childhood infections continues to grow, microbiome-based diagnostics and therapeutics will increasingly be incorporated into clinical practice to improve the prevention, diagnosis, and treatment of infectious diseases among children.

The oral microbiome: diversity, biogeography and human health

The human oral microbiota is highly diverse and has a complex ecology, comprising bacteria, microeukaryotes, archaea and viruses. These communities have elaborate and highly structured biogeography that shapes metabolic exchange on a local scale and results from the diverse microenvironments present in the oral cavity. The oral microbiota also interfaces with the immune system of the human host and has an important role in not only the health of the oral cavity but also systemic health. In this Review, we highlight recent advances including novel insights into the biogeography of several oral niches at the species level, as well as the ecological role of candidate phyla radiation bacteria and non-bacterial members of the oral microbiome. In addition, we summarize the relationship between the oral microbiota and the pathology of oral diseases and systemic diseases. Together, these advances move the field towards a more holistic understanding of the oral microbiota and its role in health, which in turn opens the door to the study of novel preventive and therapeutic strategies.

Quantifying picomoles of analyte from less than 100 live bacteria: A novel method with a buffering hydrogel as an electrochemical cell

Microenvironmental changes in the chemical surrounding of bacterial cells might have a profound impact on the ecology of biofilms. However, quantifying total amount of picomoles of analyte from a miniscule number of bacteria is an analytical challenge. Here we provide a novel microliter volume hydrogel based electrochemical cell platform suitable of coulometrically measuring hydrogen peroxide (H2O2) produced by less than 100 cells of Streptococcus sanguinis, a relevant member of the healthy oral microbiome. A morpholine moiety was incorporated into the polymer structure of the hydrogel to create a controlled microenvironment at biological pH. We calculated the buffering capacity of this hydrogel as 0.257 ± 0.135 m o l H N O 3 m o l M E A × Δ p H over the pH range of 7.2-6.2 by using a novel method designed for buffering hydrogels. The H2O2 sensors coated in microliter volume of buffering hydrogel showed no change in sensitivity within the pH range of 7.0-3.0, allowing for H2O2 measurements of S. sanguinis independent of any acid they produce. The novel platform was able to measure down to 22.7 ± 3.5 pmol H2O2 produced by less than 100 bacterial cells, which would otherwise not be attainable in large solution-based assays. These findings indicate that this is a suitable platform for quantifying metabolites from sub-milligram biological samples and may even be suitable for direct analysis of raw biofilms samples with little to no sample pretreatment.

Dysimmunity in common variable immunodeficiency is associated with alterations in oral, respiratory, and intestinal microbiota

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency characterized by decreased immunoglobulins and recurrent infections. Its aetiology remains unknown, and some patients present with severe non-infectious autoimmune or inflammatory complications with elevated associated morbimortality. Recently, intestinal dysbiosis has been proposed as a driver of immune dysregulation. In this study, we assessed the oral, respiratory, and gastrointestinal microbiota of 41 CVID patients (24 with dysimmune and 17 with infection complications) and 15 healthy volunteers using 16S rRNA gene sequencing to explore associations between microbiome profiles and CVID phenotypes. Profound differences in the composition of the microbiota in saliva, sputum, and stool were detected between dysimmune CVID patients and healthy individuals. Globally, respiratory species diversity and faecal bacterial richness were lower in CVID individuals with immune complications. Although a single species could not be identified as a robust predictor of dysimmunity, a combination of around 5-7 bacterial species in each type of sample could predict this severe phenotype with an accuracy of around 90% in the study population. Our study provides new insights into these previously unexplored but highly interrelated ecological niches among themselves and with patient profiles. Our data suggest that this disease-related systemic dysbiosis could be implicated in the immune dysregulation associated with severe cases of CVID.

Changes in Dental Biofilm Proteins' Secondary Structure in Groups of People with Different Cariogenic Situations in the Oral Cavity and Using Medications by Means of Synchrotron FTIR-Microspectroscopy

This work unveils the idea that the cariogenic status of the oral cavity (the presence of active caries lesions) can be predicted via a lineshape analysis of the infrared spectral signatures of the secondary structure of proteins in dental biofilms. These spectral signatures that work as natural markers also show strong sensitivity to the application in patients of a so-called modulator-a medicinal agent (a pelleted mineral complex with calcium glycerophosphate). For the first time, according to our knowledge, in terms of deconvolution of the complete spectral profile of the amide I and amide II bands, significant intra- and intergroup differences were determined in the secondary structure of proteins in the dental biofilm of patients with a healthy oral cavity and with a carious pathology. This allowed to conduct a mathematical assessment of the spectral shifts in proteins' secondary structure in connection with the cariogenic situation in the oral cavity and with an external modulation. It was shown that only for the component parallel β-strands in the amide profile of the biofilm, a statistically significant (p < 0.05) change in its percentage weight (composition) was registered in a cariogenic situation (presence of active caries lesions). Note that no significant differences were detected in a normal situation (control) and in the presence of a carious pathology before and after the application of the modulator. The change in the frequency and percentage weight of parallel β-strands in the spectra of dental biofilms proved to be the result of the presence of cariogenic mutans streptococci in the film as well as of the products of their metabolism-glucan polymers. We foresee that the results presented here can inherently provide the basis for the infrared spectral diagnosis of changes (shifts) in the oral microbiome driven by the development of the carious process in the oral cavity as well as for the choice of optimal therapeutic treatments of caries based on microbiome-directed prevention measures.

Salivary metabolomic profile associated with cariogenic risk in children

OBJECTIVES

To identify the metabolomic differences in the saliva of healthy children versus children with active carious lesions and to estimate the predictive capacity of a model based on the salivary metabolomic profile.

METHODS

A study of cases (n = 31) and controls (n = 37) was designed for children aged between 6 and 12 (mean age of the cases: 8.9; controls: 8.7). The said children attended public health centers in Valencia, Spain. Intraoral examinations were performed by a single examiner using ICDAS II diagnostic criteria. Unstimulated total saliva samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

The dft index for cases was 2.84 while it was 0.19 for the control group, the DMFT index was 1.13 and 0.11, respectively. The predictive model generated by the multivariate PLS-DA analysis projects a separation between the cases and the controls on the score chart with a predictive capacity and generating an area under the curve of 0.71. The metabolites: 3-methyl-2-oxovalerate, 3-hydroxybutyrate, lactate, acetone, citrate, ornithine, ethanolamine, taurine, proline, glycine, mannose, glucose, 1-6-Anhydro-β-d-glucose and citraconate, are those that show greater significance in the model. In the controls, glycine (Cohen's d = 0.430) and glucose (Cohen's d = 0.560) present higher means compared to the cases. On the contrary, taurine (Cohen's d= -0.474) and mannose (Cohen's d= -0.456) show higher means in cases compared to controls.

CONCLUSIONS

Our findings show a difference in the salivary metabolomic profiles, specifically in the groups of saccharides and amino acids, suggesting an association of these with the level of caries risk.

CLINICAL SIGNIFICANCE

The results reported in the present study reinforce the use of salivary metabolomics as a research method for the search for salivary biomarkers that allow the evaluation of caries risk in patients. Furthermore, it brings us closer to a personalized medicine that will help in dental caries prevention strategies.

The Oral Microbiome and Cross-Kingdom Interactions during Pregnancy

Pregnancy initiates a temporary transition in the maternal physiological state, with a shift in the oral microbiome and a potential increase in frequency of oral diseases. The risk of oral disease is higher among populations of Hispanic and Black women and those with lower socioeconomic status (low SES), demonstrating a need for intervention within these high-risk populations. To further our understanding of the oral microbiome of high-risk pregnant women, we characterized the oral microbiome in 28 nonpregnant and 179 pregnant low-SES women during their third trimester living in Rochester, New York. Unstimulated saliva and supragingival plaque samples were collected cross-sectionally, followed by assessment of the bacterial (16S ribosomal RNA) and fungal (18S ITS) microbiota communities. Trained and calibrated dentists performed oral examinations to determine the number of decayed teeth and plaque index. Initially, plaque from 28 nonpregnant women and 48 pregnant women were compared; these data showed significant differences in bacterial abundances based on pregnancy status. To further our understanding of the oral microbiome within the pregnant population, we next examined the oral microbiome within this population based on several variables. Streptococcus mutans, Streptococcus oralis, and Lactobacillus were associated with a greater number of decayed teeth. The composition of fungal communities differed between plaque and saliva, demonstrating 2 distinct "mycotypes" that were represented by a greater abundance of Candida in plaque and Malassezia in saliva. Veillonella rogosae, a common oral bacterium, was negatively associated with both plaque index and salivary Candida albicans colonization by culture data. This was further emphasized by in vitro inhibition of C. albicans by V. rogosae. Identification of interactions between the bacterial or fungal oral communities revealed that V. rogosae was positively associated with the oral commensal Streptococcus australis and negatively with the cariogenic Lactobacillus genus, suggesting V. rogosae as a potential biomarker of a noncariogenic oral microbiome.

Lifestyles, arterial aging, and its relationship with the intestinal and oral microbiota (MIVAS III study): a research protocol for a cross-sectional multicenter study

Background

The microbiota is increasingly recognized as a significant factor in the pathophysiology of many diseases, including cardiometabolic diseases, with lifestyles probably exerting the greatest influence on the composition of the human microbiome. The main objectives of the study are to analyze the association of lifestyles (diet, physical activity, tobacco, and alcohol) with the gut and oral microbiota, arterial aging, and cognitive function in subjects without cardiovascular disease in the Iberian Peninsula. In addition, the study will examine the mediating role of the microbiome in mediating the association between lifestyles and arterial aging as well as cognitive function.

Methods and analysis

MIVAS III is a multicenter cross-sectional study that will take place in the Iberian Peninsula. One thousand subjects aged between 45 and 74 years without cardiovascular disease will be selected. The main variables are demographic information, anthropometric measurements, and habits (tobacco and alcohol). Dietary patterns will be assessed using a frequency consumption questionnaire (FFQ) and the Mediterranean diet adherence questionnaire. Physical activity levels will be evaluated using the International Physical Activity Questionnaire (IPAQ), Marshall Questionnaire, and an Accelerometer (Actigraph). Body composition will be measured using the Inbody 230 impedance meter. Arterial aging will be assessed through various means, including measuring medium intimate carotid thickness using the Sonosite Micromax, conducting analysis with pulse wave velocity (PWA), and measuring pulse wave velocity (cf-PWV) using the Sphygmocor System. Additional cardiovascular indicators such as Cardio Ankle Vascular Index (CAVI), ba-PWV, and ankle-brachial index (Vasera VS-2000^®) will also be examined. The study will analyze the intestinal microbiota using the OMNIgene GUT kit (OMR-200) and profile the microbiome through massive sequencing of the 16S rRNA gene. Linear discriminant analysis (LDA), effect size (LEfSe), and compositional analysis, such as ANCOM-BC, will be used to identify differentially abundant taxa between groups. After rarefying the samples, further analyses will be conducted using MicrobiomeAnalyst and R v.4.2.1 software. These analyses will include various aspects, such as assessing α and β diversity, conducting abundance profiling, and performing clustering analysis.

Discussion

Lifestyle acts as a modifier of microbiota composition. However, there are no conclusive results demonstrating the mediating effect of the microbiota in the relationship between lifestyles and cardiovascular diseases. Understanding this relationship may facilitate the implementation of strategies for improving population health by modifying the gut and oral microbiota.

Trial registration

clinicaltrials.gov/ct2/show/NCT04924907, ClinicalTrials.gov, identifier: NCT04924907. Registered on 21 April 2021.

Effect of silver diamine fluoride upon the microbial community of carious lesions: A scoping review

OBJECTIVES

To explore the effects of silver diamine fluoride (SDF) on the microbial community of carious lesions.

DATA

Original studies evaluating the effect of SDF treatment on the microbial community of human carious lesions were included.

SOURCES

A systematic search of English-language publications was performed in PubMed, EMBASE, Scopus, and Web of Science. Gray literature was searched in ClinicalTrials.gov and Google Scholar.

STUDY SELECTION/RESULTS

This review included seven publications reporting the effects of SDF on microbial community of dental plaque or carious dentin, including the microbial biodiversity, relative abundance of microbial taxa, and predicted functional pathways of the microbial community. The studies on microbial community of dental plaque reported that SDF did not have a significant effect on both the within-community species diversity (alpha-diversity) and inter-community microbial compositional dissimilarity (beta-diversity) of the plaque microbial communities. However, SDF changed the relative abundance of 29 bacterial species of plaque community, inhibited carbohydrate transportation and interfered with the metabolic functions of the plaque microbial community. A study on the microbial community in dentin carious lesions reported that SDF affected its beta-diversity and changed the relative abundance of 14 bacterial species.

CONCLUSION

SDF showed no significant effects on the biodiversity of the plaque microbial community but changed the beta-diversity of the carious dentin microbial community. SDF could change the relative abundance of certain bacterial species in the dental plaque and the carious dentin. SDF could also affect the predicted functional pathways of the microbial community.

CLINICAL SIGNIFICANCE

This review provided comprehensive evidence on the potential effect of SDF treatment on the microbial community of carious lesions.

Anti-biofilm and bacteriostatic effects of three flavonoid compounds on Streptococcus mutans

Streptococcus mutans (S. mutans) is the main cariogenic pathogen associated with dental caries. Orientin-2''-O-β-L-galactoside, orientin and vitexin are natural flavonoids compound. In this study, the antibacterial ability of these flavonoids and their mechanisms in inhibiting S. mutans biofilm formation were investigated. Inhibition zone and 2-fold-dilution tests showed that these flavonoids exerted inhibitory effects on S. mutans. Phenol sulfuric acid method and lactate dehydrogenase (LDH) test revealed that they could reduce EPS formation and stimulate S. mutans to release LDH. Moreover, crystal violet and live/dead bacterial staining test showed that they inhibited biofilm formation. Finally, qRT-PCR test indicated that the down-regulated the transcription levels of spaP, srtA, brpA, gtfB and luxS genes of S. mutans. In conclusion, orientin-2''-O-β-L-galactoside, orientin and vitexin had antibacterial and anti-biofilm activities.

Microbiome and metabolome associated with white spot lesions in patients treated with clear aligners

White spot lesions (WSLs) have long been a noteworthy complication during orthodontic treatment. Recently, an increasing number of orthodontists have found that adolescents undergoing orthodontic treatment with clear aligners are at a higher risk of developing WSLs. The oral microbiota and metabolites are considered the etiologic and regulatory factors of WSLs, but the specific impact of clear aligners on the oral microbiota and metabolites is unknown. This study investigated the differences in the salivary microbiome and metabolome between adolescents with and without WSLs treated with clear aligners. Fifty-five adolescents (aged 11-18) with Invisalign appliances, 27 with and 28 without WSLs, were included. Saliva samples were analyzed using 16S rRNA gene sequencing and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS); the data were further integrated for Spearman correlation analysis. The relative abundances of 14 taxa, including Actinobacteria, Actinomycetales, Rothia, Micrococcaceae, Subdoligranulum, Capnocytophaga, Azospira, Olsenella, Lachnoanaerobaculum, and Abiotrophia, were significantly higher in the WSL group than in the control group. Metabolomic analysis identified 27 potential biomarkers, and most were amino acids, including proline and glycine. The metabolites were implicated in 6 metabolic pathways, including alanine, aspartate and glutamate metabolism; glycine, serine and threonine metabolism; and aminoacyl-tRNA biosynthesis. There was a correlation between the salivary microbial and metabolomic datasets, reflecting the impact of clear aligners on the metabolic activity of the oral flora. A concordant increase in the levels of Lachnoanaerobaculum, Rothia, Subdoligranulum and some amino acids had predictive value for WSL development. In summary, when adolescents undergo long-term clear aligner therapy with poor oral hygiene habits, clear aligners can disrupt the balance of the oral microecosystem and lead to oral microbiota dysbiosis, thereby increasing the risk of developing WSLs. Our findings might contribute to the understanding of the pathogenesis of WSLs and provide candidate biomarkers for the diagnosis and treatment of WSLs associated with clear aligners.

Untargeted metabolomics of saliva in caries-active and caries-free children in the mixed dentition

Objective

To compare the differences in salivary metabolites between caries-active and caries-free children in the mixed dentition, and explore their correlation with caries status.

Methods

The study involved 20 children (aged 8–9 years) in the mixed dentition, including 10 caries-active (aged 8.6 ± 0.49years) and 10 caries-free children(aged 8.5 ± 0.5years), with a male/female ratio of 1:1. The saliva samples were collected from all children. Metabolite extraction, LC-MS/MS-based untargeted metabolomics, qualitative and semi-quantitative analysis and bioinformatics analysis were performed to identify differential metabolites between the two sample groups. The differential metabolites identified were further analyzed in an attempt to find their correlations with caries status.

Results

In the positive ion mode, a total of 1606 molecular features were detected in the samples of the two groups, 189 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 104 up-regulated and 85 down-regulated metabolites. In the negative ion mode, a total of 532 molecular features were detected in the samples of two groups, 70 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 37 up-regulated and 33 down-regulated metabolites. In the positive ion mode, two of the top 5 up-regulated differential metabolites were found in and annotated to specific metabolic pathways, whereas in the negative ion mode, only one of the top 5 up-regulated differential metabolites was found in and annotated to specific metabolic pathways. In both the positive and negative ion modes, the top 5 down-regulated differential metabolites were both annotated to the metabolic pathways. KEGG pathway enrichment analysis of differential metabolites showed that histamine and arachidonic acid identified in the positive ion mode, as well as succinate and L-histidine identified in the negative ion mode were enriched in the top 3 significantly altered pathways.

Conclusion

The enriched differential metabolites including histamine, L-histidine and succinate were correlated with the presence of dental caries, but their role in the caries process needs to be further investigated.

Identification of a Biomarker Panel for Diagnosis of Early Childhood Caries Using Salivary Metabolic Profile

Several studies have demonstrated that nuclear magnetic resonance (NMR) metabolic profiles can differentiate patients with caries from healthy individuals; however, these studies only identified individual metabolites. The present study aimed to identify a salivary metabolite biomarker panel for the diagnosis of early childhood caries (ECC). Saliva samples from children with and without caries were analyzed using NMR spectroscopy. Multivariate and univariate analyses were performed to identify the discriminating metabolites. Selected metabolites were further evaluated and used to detect ECC. The saliva samples of children with ECC were characterized based on the increased levels of formate, glycerophosphocholine, and lactate and reduced levels of alanine, glycine, isoleucine, lysine, proline, and tyrosine. The levels of these metabolites were significantly different from those in the control in the ECC subgroup according to caries severity and correlated with the number of decayed and filled teeth or surfaces. Subsequently, an optimal salivary metabolite biomarker panel comprising formate, lactate, proline, and glycine was developed. This panel exhibited a better diagnostic performance for ECC than a single metabolite. These results demonstrate that salivary metabolic signatures can reflect oral conditions associated with dental caries, thereby emphasizing the importance of distinct salivary metabolic profiles as potential biomarkers of ECC.

Short-term sugar stress induces compositional changes and loss of diversity of the supragingival microbiota

Frequent intake of free sugars is a major risk factor for dental caries, but the immediate influence of sugar intake on the supragingival microbiota remains unknown. We aim to characterize the effect of 14 days of sugar rinsing on the supragingival microbiota. Forty orally and systemically healthy participants rinsed their mouth with a 10% sucrose solution, 6-8 times a day, for 14 days, followed by 14 days without sugar stress. Supragingival plaque samples were collected at baseline, and after 14, and 28 days. The supragingival microbiota was analyzed using 16S rDNA sequencing. Taxonomic classification was performed using the Human Oral Microbiome Database. After 14 days of sugar stress induced by the daily sugar rinses, a significant loss of α-diversity (p = 0.02) and a significant increase in the relative abundance of Actinomyces (6.5% to 9.6%, p = 0.006) and Corynebacterium (6.2% to 9.1%, p = 0.03) species were recorded. In addition, a significant decrease in Streptococcus (10.3% to 6.1%, p = 0.001) species was observed. Sugar-mediated changes returned to baseline conditions 14 days after the last sugar rinse. The present study shows that temporary sugar stress induces loss of diversity and compositional changes to the supragingival microbiota, which are reversible if oral care is maintained.

Application of fluoride disturbs plaque microecology and promotes remineralization of enamel initial caries

Background

The caries-preventive effect of topical fluoride application has been corroborated by a number of clinical studies. However, the effect of fluoride on oral microecology remains unclear.

Objective

To monitor the effect of fluoride on dental plaque microecology and demineralization/remineralization balance of enamel initial caries.

Methods

Three-year-old children were enrolled and treated with fluoride at baseline and 6 months. International Caries Detection and Assessment System II indices of 52 subjects were measured at baseline, 3, 6, and 12 months. Supragingival plaque samples of 12 subjects were collected at baseline, 3 and 14 days for 16S rRNA sequencing.

Results

Changes in microbial community structure were observed at 3 days after fluoridation. Significant changes in the relative abundance of microorganisms were observed after fluoride application, especially Capnocytophaga, unidentified Prevotellaceae and Rothia. Functional prediction revealed that cell movement, carbohydrate and energy metabolism were affected significantly after fluoride application. Fluoride significantly inhibited enamel demineralization and promoted remineralization of early demineralized caries enamel at 3 months.

Conclusion

Fluoride application significantly inhibited the progression of enamel initial caries and reversed the demineralization process, possibly by disturbing dental plaque microecology and modulating the physicochemical action of demineralization/remineralization. This deepened our understanding of caries-preventive effects and mechanisms of fluoride.

Polymicrobial Infections and Biofilms: Clinical Significance and Eradication Strategies

Biofilms are population of cells growing in a coordinated manner and exhibiting resistance towards hostile environments. The infections associated with biofilms are difficult to control owing to the chronicity of infections and the emergence of antibiotic resistance. Most microbial infections are contributed by polymicrobial or mixed species interactions, such as those observed in chronic wound infections, otitis media, dental caries, and cystic fibrosis. This review focuses on the polymicrobial interactions among bacterial-bacterial, bacterial-fungal, and fungal-fungal aggregations based on in vitro and in vivo models and different therapeutic interventions available for polymicrobial biofilms. Deciphering the mechanisms of polymicrobial interactions and microbial diversity in chronic infections is very helpful in anti-microbial research. Together, we have discussed the role of metagenomic approaches in studying polymicrobial biofilms. The outstanding progress made in polymicrobial research, especially the model systems and application of metagenomics for detecting, preventing, and controlling infections, are reviewed.

The impact of Er:YAG laser combined with fluoride treatment on the supragingival plaque microbiome in children with multiple caries: a dynamic study

BACKGROUND

As a minimally invasive tool for caries prevention tool, the pulsed erbium:yttrium-aluminum-garnet (Er:YAG) laser is being used in a large number of studies. Microorganisms are extremely vital in the occurrence and development of dental caries. However, the impact of Er:YAG laser irradiation combined with fluoride on the dynamic microbial changes that occur in dental plaques is still uncertain. In this study, we examined the effect of an Er:YAG laser combined with fluorine on supragingival microbial composition and diversity in children with multiple caries.

METHODS

In this study, dental plaque samples (n = 48) were collected from 12 children with over 8 filled teeth. Supragingival plaques from left mandibular molars before (CB) and after fluoride treatment (CA) and right mandibular molars before (EB) and after fluoride+Er:YAG laser treatment (EA) were collected from each patient. In CB and EB groups, the samples were collected just before the treatments. In CA and EA groups, the samples were collected 1 month after treatments. Then, all specimens were subjected to 16S rRNA high-throughput sequencing to investigate the changes in microbial composition and diversity in mandibular molar supragingival plaques before and after fluoride or fluoride+Er:YAG laser treatment.

RESULTS

The dental plaque microbial diversity was higher in the EA group than in the EB group (baseline levels), and the microbial composition changed in EA group compared with EB group (P < 0.05). The levels of microorganisms associated with caries occurrence, including Proteobacteria, Fusobacteria, and Bacteroidetes, declined, while the levels of Faecacterium, Fastidiosipila, Vibrio, and Shewanella increased in EA group compared with EB group. The declines in Firmicutes, Streptococcus, Fusobacterium, and Veillonella levels were significantly lower in the EA group than in the CA group.

CONCLUSION

The combined application of the Er:YAG laser and fluoride may be more effective than using fluoride alone in reducing the proportion of cariogenic bacteria, increasing the diversity of plaque microorganisms, and further promoting the microecological balance.

Oral Microbiome and Dental Caries Development

Dental caries remains the most prevalent oral disease worldwide. The development of dental caries is highly associated with the microbiota in the oral cavity. Microbiological research of dental caries has been conducted for over a century, with conventional culture-based methods and targeted molecular methods being used in order to identify the microorganisms related to dental caries. These methods’ major limitation is that they can identify only part of the culturable microorganisms in the oral cavity. Introducing sequencing-based technology and bioinformatics analysis has boosted oral microbiome research and greatly expanded the understanding of complex oral microbiology. With the continuing revolution of molecular technologies and the accumulated sequence data of the oral microbiome, researchers have realized that microbial composition alone may be insufficient to uncover the relationship between caries and the microbiome. Most updated evidence has coupled metagenomics with transcriptomics and metabolomics techniques in order to comprehensively understand the microbial contribution to dental caries. Therefore, the objective of this article is to give an overview of the research of the oral microbiome and the development of dental caries. This article reviews the classical concepts of the microbiological aspect of dental caries and updates the knowledge of caries microbiology with the results of current studies on the oral microbiome. This paper also provides an update on the caries etiological theory, the microorganisms related to caries development, and the shifts in the microbiome in dental caries development.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Does high sugar intake really alter the oral microbiota?: A systematic review

OBJECTIVES

Diet is one of the main factors influencing the diversity and interactions of the oral microbiota. The purpose of this study is to determine the impact of sugar intake on the microbial diversity and bacteria that predominate under these conditions.

MATERIAL AND METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guide, using the PubMed, Scopus, and Science Direct databases and combinations of the words "microbiota," "microbiology," "bacteria," "sugars," "dysbiosis," "caries," "microbiome," "oral microbial," and "oral microbiota profile pattern." The selection criteria included year, language, type of publication, comparison of microbiota during low and high sugar intake, and bacterial identification by molecular sequencing of the 16S subunit of ribosomal RNA.

RESULTS

Out of a total of 374 papers that came up after the initial search, 8 met the criteria for this review. The papers included research on populations comprising children, young adults, and adults, with most of the studies reporting selection criteria for the participants and using validated instruments to determine sugar intake. Apart from one study, all others reported for high sugar intake conditions a significant decrease in microbial diversity of the oral microbiome and the predominance of several bacterial genera or species, including Streptococcus, Scardovia, Veillonella, Rothia, Actinomyces, and Lactobacillus.

CONCLUSIONS

Sugar-rich diets have a significantly unfavorable effect on the diversity and balance of oral microbiota; however, further studies are required to determine the exact role of sugar in microbial interactions.

From Mouth to Brain: Distinct Supragingival Plaque Microbiota Composition in Cerebral Palsy Children With Caries

Children with cerebral palsy (CP) present a higher prevalence and severity of caries. Although researchers have studied multiple risk factors for caries in CP, the role of microorganisms in caries remains one of the critical factors worth exploring. In order to explore the differences in the supragingival plaque microbiota (SPM), supragingival plaque samples were collected from 55 CP children and 23 non-CP children for 16S rRNA sequencing. Distinct SPM composition was found between CP children with severe caries (CPCS) and non-CP children with severe caries (NCPCS). Further subanalysis was also done to identify if there were any differences in SPM among CP children with different degrees of caries, namely, caries-free (CPCF), mild to moderate caries (CPCM), and severe caries (CPCS). After selecting the top 15 most abundant species in all groups, we found that CPCS was significantly enriched for Fusobacterium nucleatum, Prevotella intermedia, Campylobacter rectus, Porphyromonas endodontalis, Catonella morbi, Alloprevotella tannerae, Parvimonas micra, Streptobacillus moniliformis, and Porphyromonas canoris compared to NCPCS. By comparing CPCF, CPCM, and CPCS, we found that the core caries-associated microbiota in CP children included Prevotella, Alloprevotella, Actinomyces, Catonella, and Streptobacillus, while Capnocytophaga and Campylobacter were dental health-associated microbiota in CP children. Alpha diversity analysis showed no significant difference between NCPCS and CPCS, but the latter had a much simpler core correlation network than that of NCPCS. Among CP children, CPCM and CPCF displayed lower bacterial diversity and simpler correlation networks than those of CPCS. In summary, the study showed the specific SPM characteristics of CPCS compared to NCPCS and revealed the core SPM in CP children with different severities of caries (CPCF, CPCM, and CPCS) and their correlation network. Hopefully, the study would shed light on better caries prevention and therapies for CP children. Findings from the current study offer exciting insights that warrant larger cohort studies inclusive of saliva and feces samples to investigate the potential pathogenic role of oral microbiota through the oral–gut–brain axis in CP children with caries.

NOD2 is involved in regulating odontogenic differentiation of DPSCs suppressed by MDP through NF-κB/p65 signaling

Dental pulp stem cells (DPSCs) are well known for their capable of both self-renewal and multilineage differentiation. Dental tissue diseases, include caries, are often accompanied by inflammatory microenvironment, and muramyl dipeptide (MDP) is involved in the inflammatory stimuli to influence the differentiation of DPSCs. Nucleotide-binding oligomerization domain 2 (NOD2), a member of the cytosolic Nod-like receptor (NLR) family, plays a key role in inflammatory homeostasis regulation, but the role of NOD2 in DPSCs differentiation under inflammatory is still unclear. In this study, we identified that MDP suppressed odontogenic differentiation of DPSCs via NOD2/ NF-κB/p65 signaling pathway. Alizarin red staining and ALP activity showed the odontogenic differentiation was suppressed by MDP in a concentration-dependent manner, and the expression of dentin differentiation marker protein dentin matrix protein 1 (DMP-1) and dentin Sialophosphoprotein (DSPP) also indicated the same results. The expression of NOD2 increased gradually with the concentration of MDP as well as the phosphorylation and nuclear translocation of p65, which meant NF-κB signaling pathway was activated. Further, the interference of NOD2 inhibited the phosphorylation and nuclear translocation of p65 and reversed the MDP-mediated decrease of odontoblast differentiation of DPSCs. Our study showed that MDP can inhibit the odontoblast differentiation of DPSCs in a concentration-dependent manner. The NF-κB signaling pathway was activated by increasing expression of NOD2. Interference of NOD2 reversed the negative ability odontoblast differentiation of DPSCs in the inflammatory environment. Our study might provide a theoretical basis for the clinical treatment for dentinogenesis of DPSCs.

Metagenomic Analysis of Dental Plaque on Pit and Fissure Sites With and Without Caries Among Adolescents

Caries is one of the most prevalent infectious diseases worldwide and is driven by the dysbiosis of dental biofilms adhering to tooth surfaces. The pits and fissured surfaces are the most susceptible sites of caries. However, information on the taxonomic composition and functional characteristics of the plaque microbiota in the pit and fissure sites is very limited. This study aimed to use metagenomic sequencing analyses to investigate the relationship between the plaque microbiome in the pit and fissure site and caries in adolescents. A total of 20 adolescents with active pit and fissure surface caries were involved as well as 20 age-matched, caries-free teenagers for control tests. Plaque samples were collected from the pit and fissure site and were subjected to metagenomic analyses, in which the microbial communities were investigated. Our results showed that the microbiota diversity was similar between those two groups. At the species level, the relative abundances of A. gerencseriae, P. acidifaciens, P. multisaccharivorax, S. oralis, S. mutans, and P. denticolens were higher in the caries-active group. N. elongata, C. hominis, and A. johnsonii were relatively more abundant in the caries-free groups. Functional analysis suggested that the metabolic pathway was the most abundant pathway, and the functional traits of the level 2 pathways included amino acid metabolism, metabolism of cofactors, and vitamins and carbohydrate metabolism. Our results also revealed that the caries group displayed several alterations in metabolic pathways, including enriched functions in carbohydrate digestion and absorption. This study suggested that in addition to the specific anatomical structures of the pit and fissured surfaces, the fundamental differences in the plaque microbiome may also be related to the susceptibility of pit and fissure caries.