Aciduric microbial taxa including Scardovia wiggsiae and Bifidobacterium spp. in caries and caries free subjects

Comparative Evaluation of Antimicrobial Effectiveness and Compressive Strength in Neem and Lemongrass-Modified Glass Ionomer Cement: An In Vitro Study

Background Glass ionomer cement (GIC) demonstrates biocompatibility and fluoride ion release, indicating their potential to inhibit a wide range of bacteria, although this remains uncertain. Lemongrass and neem are recognized for their potent antimicrobial activity against numerous pathogenic microorganisms. The objective of the study is to evaluate the antimicrobial effectiveness and compressive strength of GIC modified with neem and lemongrass. Methodology Lemongrass and neem were incorporated into conventional GIC at varying concentrations. Group I - neem-modified GIC (0.5%, 1%, 2%), group II - lemongrass-modified GIC (0.5%, 1%, 2%), and group III (non-modified GIC as a control group). The disk-shaped specimens were then compared to unmodified GIC (control). Antimicrobial effectiveness was assessed using the minimal inhibitory concentration (MIC) assay against Streptococcus mutans and Lactobacillus. Compressive strength was assessed using a Universal Testing Machine, with a crosshead speed set to 0.5 mm per minute. Statistical analysis was conducted with a significance level set at p < 0.05. Results Neem modification displayed superior antimicrobial effectiveness against both Streptococcus mutans and Lactobacillus at all concentrations when compared to the control, with 2% showing the least mean value of 0.262. In contrast, lemongrass modification exhibited a significant difference in effectiveness against Streptococcus mutans but no difference against Lactobacillus. Neem modification demonstrated superior performance compared to lemongrass (p < 0.05). Both modified groups showed no significant impact on compressive strength. Conclusions Neem-modified GIC demonstrated the highest antimicrobial efficacy against Streptococcus mutans and Lactobacillus without altering its compressive strength. This suggests its potential as a promising alternative material in restorative dentistry. Additional in vivo investigations are needed to assess the extended-term effectiveness of the material.

How probiotics, prebiotics, synbiotics, and postbiotics prevent dental caries: an oral microbiota perspective

Dental caries, a highly prevalent oral disease, impacts a significant portion of the global population. Conventional approaches that indiscriminately eradicate microbes disrupt the natural equilibrium of the oral microbiota. In contrast, biointervention strategies aim to restore this balance by introducing beneficial microorganisms or inhibiting cariogenic ones. Over the past three decades, microbial preparations have garnered considerable attention in dental research for the prevention and treatment of dental caries. However, unlike related pathologies in the gastrointestinal, vaginal, and respiratory tracts, dental caries occurs on hard tissues such as tooth enamel and is closely associated with localized acid overproduction facilitated by cariogenic biofilms. Therefore, it is insufficient to rely solely on previous mechanisms to delineate the role of microbial preparations in the oral cavity. A more comprehensive perspective should involve considering the concepts of cariogenic biofilms. This review elucidates the latest research progress, mechanisms of action, challenges, and future research directions regarding probiotics, prebiotics, synbiotics, and postbiotics for the prevention and treatment of dental caries, taking into account the unique pathogenic mechanisms of dental caries. With an enhanced understanding of oral microbiota, personalized microbial therapy will emerge as a critical future research trend.

Effect of a Toothpaste Containing Surface Pre-Reacted Glass-Ionomer Filler on the Remineralization of Artificial Carious Enamel Lesions in situ

This study evaluated the remineralizing effect of a toothpaste containing surface pre-reacted glass-ionomer (S-PRG) filler on demineralized enamel in situ. For this, 180 bovine enamel samples were demineralized by using a microcosm biofilm model for 3 days. Thereafter, the samples were randomly signed to 15 healthy volunteers and to 3 cross-over in situ phases corresponding to the following treatments: (1) toothpaste containing 1,500 ppm F as NaMFP (positive control, Colgate®Cavity Protection), (2) toothpaste containing 5% S-PRG filler (Shofu®), and (3) placebo toothpaste (negative control prepared by Shofu®). Four demineralized enamel blocks were fixed into each palatal appliance per phase. The volunteers wore the appliances for 5 days and were trained to brush their teeth 2 times for 2 min a day, while one drop of the toothpaste's slurry (1:3) was dripped on each sample for the same period. The surface hardness and TMR analyses were done and analyzed by ANOVA/Tukey and t test (p < 0.05). S-PRG filler and Colgate® toothpastes were equally able to improve 2-2.5× enamel remineralization by the analysis of % surface hardness recovery. However, S-PRG toothpaste was the only one able to significantly improve ΔΔZ (the integrated mineral loss recovery: 1,489 ± 503 %vol.μm) compared to placebo (1,050 ± 467 %vol.μm), while Colgate® did not differ from placebo. No differences were seen between the groups with respect to ΔLD. S-PRG filler and Colgate® toothpastes show similar potential to remineralize the lesion surface. However, S-PRG toothpaste is better to recover mineral loss at the subsurface area.

In vitro evaluation of the antibacterial and cytotoxic activities of the Euclea natalensis crude extract and fractions against oral infection agents

OBJECTIVE

This study aimed (i) to evaluate the antibacterial and cytotoxic activities of the crude extract and fractions obtained from Euclea natalensis A.D.C. roots against bacteria that cause periodontal disease and caries and (ii) to identify the isolated compounds.

DESIGN

The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the extract and fractions were determined by the microplate dilution assay. The cytotoxicity of the extract and fractions was evaluated by using the XTT colorimetric assay and normal human fibroblast cells (GM07492A, lung fibroblasts). The compounds present in the most promising fraction were determined by qualitative analysis through liquid chromatography coupled to mass spectrometry (HPLC-MS-ESI).

RESULTS

The MIC results ranged from 25 to > 400 μg/mL for the extract and from 1.56 to > 400 μg/mL for the fractions. To evaluate cytotoxicity, the tested concentrations of the extract and fractions ranged from 19.5 to 2500 μg/mL; IC₅₀ values between 625 and 1250 μg/mL were obtained. Analysis of the main bioactive fraction by HPLC-MS-ESI identified phenolic acids, coumarins, naphthoquinones, lignans, and fatty acids.

CONCLUSIONS

The E. natalensis root extract and fractions displayed good antibacterial activity against periodontal pathogenic and cariogenic bacteria. The antibacterial activity may be due to compounds present in the extract and fractions, which also showed low cytotoxicity to normal human cells. These data are relevant and encourage further research into this plant species, which may contribute to the discovery of new herbal medicines that will help to mitigate the problems caused by oral pathogenic bacteria.

Association between Bifidobacterium and Scardovia Wiggsiae and caries-related factors in severe early childhood caries and caries-free Thai children: a quantitative real-time PCR analysis and a questionnaire cross-sectional study

AIMS

To quantitatively identify Bifidobacterium, S. wiggsiae and S. mutans in plaque samples obtained from children with severe-ECC and caries-free groups and to analyze their association with caries-related factors retrieved from the questionnaire in each group.

STUDY DESIGN

To establish the 2 study groups, clinical examination in 122 Thai children, aged 2-5 years, recorded decayed, missing and filled teeth scores (dmft), in addition to plaque and gingival indices. Sixty one children in the caries-free group and 61 in the S-ECC group were identified. A questionnaire was used to assess the parent's attitudes and behavior regarding the child's oral hygiene care and diet.

METHODS

Pooled overnight supra gingival plaque was collected from each child using a sterile toothpick, released in 1 ml of TE buffer, transported on ice to the Laboratory and stored at  - 20 °C. DNA was extracted from the plaque based on enzymatic lysis and quantitative real-time PCR using fluorescent dye (SYBR green) in addition to Agarose gel electrophoresis were performed. All laboratory and retrieved from the questionnaire data per child were recorded and statistically analysed.

RESULTS

S. wiggsiae (p < 0.005) and S. mutans (p < 0.001) were higher in the S-ECC group. Bifidobacterium, S. mutans, and S. wiggsiae were associated with the dmft score and gingival index (p < 0.001). The dmft scores of children who detected only S. mutans were significantly lower than the dmft scores of children who detected two bacteria; S. mutans + S. wiggsiae (p = 0.028), S. mutans + Bifidobacterium (p = 0.026), and three bacteria; S. mutans + Bifidobacterium + S. wiggsiae (p = 0.007). Children who found all three bacteria (Bi + Sm + Sw) had the highest dmft scores, followed by children who had two bacteria (Bi + Sw, or Bi + Sm, or Sw + Sm). The guardians' education levels, occupations, household income, prolonged bottle feeding, taking of water after bottle or breast feeding, eating sugar-coated crackers or bread with sweetened cream, and premature birth were the factors that related to S-ECC.

CONCLUSION

Levels of S. wiggsiae and S. mutans, guardian's education, family economics, prolonged bottle feeding, eating high sugar-containing snacks and premature birth were associated with S-ECC.

The Effect of Toothpastes Containing Natural Extracts on Bacterial Species of a Microcosm Biofilm and on Enamel Caries Development

This study investigated the effects of herbal toothpaste on bacterial counts and enamel demineralization. Thirty-six bovine enamel samples were exposed to a microcosm biofilm using human saliva and McBain saliva (0.2% sucrose) for 5 days at 37 °C and first incubated anaerobically, then aerobically–capnophilically. The following experimental toothpaste slurries (2 × 2 min/day) were applied: (1) Vochysia tucanorum (10 mg/g); (2) Myrcia bella (5 mg/g); (3) Matricaria chamomilla (80 mg/g); (4) Myrrha and propolis toothpaste (commercial); (5) fluoride (F) and triclosan (1450 ppm F), 0.3% triclosan and sorbitol (Colgate^®, positive control); (6) placebo (negative control). The pH of the medium was measured, bacteria were analyzed using quantitative polymerase chain reaction, and enamel demineralization was quantified using transverse microradiography. The total bacterial count was reduced by toothpaste containing Myrcia bella, Matricaria chamomilla, fluoride, and triclosan (commercial) compared to the placebo. As far as assessable, Myrcia bella, Matricaria chamomilla, and Myrrha and propolis (commercial) inhibited the outgrowth of S. mutans, while Lactobacillus spp. were reduced/eliminated by all toothpastes except Vochysia tucanorum. Mineral loss and lesion depth were significantly reduced by all toothpastes (total: 1423.6 ± 115.2 vol% × μm; 57.3 ± 9.8 μm) compared to the placebo (2420.0 ± 626.0 vol% × μm; 108.9 ± 21.17 μm). Herbal toothpastes were able to reduce enamel demineralization.

Oral Microbiome: Streptococcus mutans/Caries Concordant-Discordant Children

Dental caries remains the most common chronic disease in children, and the respective etiology is not fully understood. Though Streptococcus mutans is an important factor in the initiation and progression of caries, its presence is not always associated with the disease. The existence of caries discordant populations, in which S. mutans counts do not correlate with caries experience, poses a challenging problem. This study explored the possible correlation of S. mutans and other microorganism levels on caries-associated ecology of caries-concordant and discordant populations. A total of forty-seven children were analyzed in this study and stratified into four clinical groups based on their S. mutans levels in saliva (HS/LS: High/low S. mutans) and caries experience. Streptococcus mutans levels were determined by culture-based selective plating. The salivary microbiome of caries concordant and discordant populations was investigated by 16S rRNA gene sequencing and downstream bioinformatics analysis. The salivary microbial communities significantly clustered based on S. mutans levels and independent of their caries experience. In addition to S. mutans levels, significant differences in the abundance of other species were observed between HS and LS groups. Interestingly, disease-associated species such as Veillonella dispar, Streptococcus spp., and Prevotella spp. were significantly increased in HS groups and may contribute, in combination with S. mutans, to the caries progression. Furthermore, health-associated species exhibited higher abundance in the LS groups, such as Veillonella rogosae, Haemophilus sp., and Alloprevotella spp. but their possible contribution to the caries process remains to be elucidated. This study provides evidence that S. mutans may play a role in shaping the salivary microbial community. Our results highlight that future caries research should consider additional species as health/disease microbial markers in conjunction with S. mutans to improve diagnosis and caries management of the caries-discordant population.

Microbiome Analysis of Carious Lesions in Pre-School Children with Early Childhood Caries and Congenital Heart Disease

Oral bacteria have been associated with several systemic diseases. Moreover, the abundance of bacteria associated with caries has been found to be higher in patients with congenital heart disease (CHD) than in healthy control groups (HCGs). Therefore, this study aimed to evaluate the dental microbiota in children with CHD compared to a HCG. The aim was to describe and compare the carious microbiome regarding the composition, diversity, and taxonomic patterns in these two groups. Twenty children with CHD and a HCG aged between two and six years participated. All of them were affected by early childhood caries. Microbiome profiling indicated that Fusobacterium, Prevotella, Capnocytophaga, and Oribacterium were more abundant in the CHD group, whereas Lactobacillus and Rothia were predominant in the HCG. Furthermore, microbiome analysis revealed three distinct clusters for the CHD and HCG samples. In the first cluster, we found mainly the genera Lactobacillus and Coriobacteriaceae. The second cluster showed a higher relative abundance of the genus Actinomyces and a more diverse composition consisting of more genera with a smaller relative lot. The third cluster was characterized by two genera, Streptococcus and Veillonella. These data can help us to understand the oral microbial community structures involved in caries and endodontic infections of pre-school children in relation to the general health of these high-risk patients.

Metagenomic analysis of the salivary microbiota in patients with caries, periodontitis and comorbid diseases

Background/purpose

Previous studies have suggested that there is a mutual antagonism between caries and periodontitis. This research aimed to investigate the ecological connection and bacterial interaction of these two diseases.

Materials and methods

We profiled and analyzed the salivary microbiota from 124 individuals (including 38 caries patients, 34 periodontitis patients, 15 comorbid diseases patients, and 37 healthy controls) by using 16 S rRNA gene sequencing and bioinformatics approaches, and also quantified their salivary bacteria loads via quantitative real-time PCR. The putative biological functions of the salivary microbiome of the different groups were predicted by PICRUSt.

Results

We observed that both the total bacteria loads and the overall microbial richness in the saliva of the periodontitis group were higher than that in the healthy group. The principal coordinate analysis (PCoA) showed that the caries, periodontitis and healthy groups were separated from each other, and that the samples from comorbid diseases were located at the overlap of caries and periodontitis groups. Using LEfSe analysis, 20 differentially abundant genera were identified as potential biomarkers. These genera also performed complicated interactions among the four groups. Additionally, the PICRUSt analysis indicated caries-related and periodontitis-related functions (e.g., carbohydrate metabolism and bacteria proliferation) respectively.

Conclusion

We disclosed the significant differences in the salivary bacterial community under caries, periodontitis and comorbid diseases. The periodontitis group was marked by the increased complexity of the salivary microbiota. The result may have vital clinical significance to the screening and early treatment of caries-active and periodontitis-active individuals.

Citizen-science based study of the oral microbiome in Cystic fibrosis and matched controls reveals major differences in diversity and abundance of bacterial and fungal species

Introduction: Cystic fibrosis (CF) is an autosomal genetic disease, associated with the production of excessively thick mucosa and with life-threatening chronic lung infections. The microbiota of the oral cavity can act as a reservoir or as a barrier for infectious microorganisms that can colonize the lungs. However, the specific composition of the oral microbiome in CF is poorly understood.Methods: In collaboration with CF associations in Spain, we collected oral rinse samples from 31 CF persons (age range 7-47) and matched controls, and then performed 16S rRNA metabarcoding and high-throughput sequencing, combined with culture and proteomics-based identification of fungi to survey the bacterial and fungal oral microbiome.Results: We found that CF is associated with less diverse oral microbiomes, which were characterized by higher prevalence of Candida albicans and differential abundances of a number of bacterial taxa that have implications in both the connection to lung infections in CF, as well as potential oral health concerns, particularly periodontitis and dental caries.Conclusion: Overall, our study provides a first global snapshot of the oral microbiome in CF. Future studies are required to establish the relationships between the composition of the oral and lung microbiomes in CF.

Explorative study on Lactobacillus species and their acid-producing capacity and anti-microbial activity in head and neck cancer patients

OBJECTIVE

To determine acid-producing capacity and anti-microbial activity of Lactobacillus species collected pretreatment and post treatment in head and neck cancer patients.

MATERIAL AND METHODS

Lactobacillus isolates from 21 patients pretreatment and post treatment were identified using molecular methods. The patients' stimulated salivary secretion was determined pretreatment, and 6 and 12 months post treatment and caries lesions/new filled surfaces registered at 24 months post treatment. The acid-producing capacity of the Lactobacillus isolate was analyzed using a colorimetric fermentation test in microtiter plates. The anti-microbial activity of the isolates against Streptococcus mutans associated with caries, and against the mucosal pathogens Staphylococcus aureus, Candida albicans, and Enterococcus faecalis was analyzed by determining inhibitory zones on agar plates.

RESULTS

The most frequent species were L. paracasei (n = 21), L. casei/rhamnosus (n = 17) and L. fermentum (n = 10). Sixty-seven percent of the patients harbored L. paracasei either at 6 or 12 months post radiotherapy. The corresponding figures for L. casei/rhamnosus and L. fermentum were 62% and 33%. L. paracasei strains showed the best acid-producing capacity and L. fermentum strains the lowest. Strong acid-producing capacity was most common among isolates collected at 6 months post treatment. Seventy-two percent of the strains showed an anti-microbial activity against S. mutans, one strain against S. aureus and none against C. albicans or E. faecalis.

CONCLUSION

The most frequent species isolated from head and neck cancer patients both pretreatment and post treatment were L. paracasei, L. casei/rhamnosus, and L. fermentum. L. paracasei showed the best acid-producing capacity and the highest proportion with anti-microbial activity against S. mutans.

Effect of probiotics on gingival inflammation and oral microbiota: A meta-analysis

To evaluate the effect of probiotics on gingival inflammation and oral microbiota in patients suffering from plaque-induced gingivitis. PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE were electronically searched until December 2020. The quality of included studies was assessed with the Cochrane Collaboration's Risk of Bias tool. The differences were expressed as weighted mean differences (WMD) and 95% of confidence interval (95% CI). I² test was performed to evaluate the heterogeneity of the studies. All analyses were performed using Review Manager (version 5.3). Eleven randomized and controlled trials were included, enrolling 554 patients. All comparisons displayed that oral probiotics had no significant improvement in the Gingival Index (GI), Plaque Index (PI), and bleeding on probing (BOP) of patients with plaque-induced gingivitis. In terms of microecology, no significant difference in the volumes of gingival crevicular fluid (GCF), the concentration of IL-1β, and the counts of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), and Fusobacterium nucleatum (Fn) were found between the probiotic group and the placebo group. There exists no clear evidence that oral probiotics have positive effect on gingival inflammation and oral microecological environment of patients with plaque-induced gingivitis.

Analysis of relative bacterial activity and lactate dehydrogenase gene expression of caries-associated bacteria in a site-specific natural biofilm: an ex vivo study

Objectives

Detecting bacterial activity is considered a promising approach to monitor shifts from symbiosis to dysbiosis in oral microbiome. The present study aimed at investigating both the relative bacterial activity and the lactate dehydrogenase (ldh) gene expression of caries-associated bacteria in a site-specific natural biofilm.

Material and methods

Sixty subjects (age, mean ± SE: 30.1 ± 1.4) were allocated to two groups: caries-free subjects (CF) or caries-active subjects (CA). CF presented one sound surface (CFS, n = 30). CA presented two donor sites: a cavitated caries lesion (CAC, n = 30) and a sound reference surface (CAS, n = 30). Real-time quantitative PCR (q-PCR) on species or genus level and total bacteria was performed targeting the 16S gene, the 16S rRNA, the ldh gene, and the ldh mRNA (increasing 16S ribosomal RNA copy numbers can function as an indicator of increased energy metabolism). As the 16S rRNA abundance represents the number of ribosomes, while the 16S gene abundance represents the number of genomes, the quotient of the relative abundances functions as a measure for the relative bacterial activity (%).

Results

Both lactobacilli and S. mutans showed the highest relative bacterial activity in CAC ((mean ± SE) 218 ± 60% and 61 ± 16%, respectively) and the lowest values for both sound reference surfaces (69 ± 48%; 8 ± 3%). Significant differences were found between CAC and CAS as well as between CAC and CFS for both lactobacilli and S. mutans (p < 0.05). The ldh gene expression of lactobacilli and S. mutans only showed moderate values in CAC (1.90E+03 ± 2.11E+03; 2.08E+04 ± 4.44E+04 transcripts/μl) and CFS (2.04E+03 ± 2.74E+03; 8.16E+03 ± 6.64E+03 transcripts/μl); consequently no significant differences were detected.

Conclusion and clinical relevance

Caries-associated bacteria (lactobacilli and S. mutans) showed the highest relative bacterial activity in plaque of cavitated lesions, the lowest in sound surfaces, allowing the detection of a significant activity shift in health and disease for caries-active patients. However, no significant differences in ldh gene expression could be determined.

In-Vitro Model of Scardovia wiggsiae Biofilm Formation and Effect of Nicotine

Recently, Scardovia wiggsiae has been reported to be strongly associated with caries formation. This study aimed to establish an in vitro model of S. wiggsiae biofilm and to investigate the effect of nicotine on S. wiggsiae colony-forming units (CFUs) growth. S. wiggsiae biofilm was grown overnight using brain-heart infusion (BHI) broth supplemented with 5 g of yeast extract/L (BHI-YE). The overnight culture was used as an inoculum to grow S. wiggsiae biofilm on standardized enamel and dentin samples. Samples were incubated with different nicotine concentrations (0, 0.5, 1, 2, 4, 8, 16 and 32 mg/mL) for 3 days. The dissociated biofilms were diluted, spiral plated on blood agar plates, and incubated for 24 h. CFUs/mL were quantified using an automated colony counter. A two-way ANOVA was used to compare the effect of different nicotine concentrations on S. wiggsiae CFUs. This study demonstrated that S. wiggsiae biofilm could be initiated and formed in vitro. Increased CFUs was observed through 0.5-4 mg/mL and 0.5-8 mg/mL of nicotine using enamel and dentin substrates, respectively. 16 and 32 mg/mL of nicotine were determined as the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), respectively. S. wiggsiae formed greater biofilm on enamel than dentin specimens in response to the nicotine stimulus. This study demonstrated the negative effect of smoking on increasing S. wiggsiae biofilm. Establishing S. wiggsiae biofilm in vitro may allow researchers in the future to have a better understanding of caries pathogenesis and bacterial interaction.

Decoding the Genomic Variability among Members of the Bifidobacterium dentium Species

Members of the Bifidobacterium dentium species are usually identified in the oral cavity of humans and associated with the development of plaque and dental caries. Nevertheless, they have also been detected from fecal samples, highlighting a widespread distribution among mammals. To explore the genetic variability of this species, we isolated and sequenced the genomes of 18 different B. dentium strains collected from fecal samples of several primate species and an Ursus arctos. Thus, we investigated the genomic variability and metabolic abilities of the new B. dentium isolates together with 20 public genome sequences. Comparative genomic analyses provided insights into the vast metabolic repertoire of the species, highlighting 19 glycosyl hydrolases families shared between each analyzed strain. Phylogenetic analysis of the B. dentium taxon, involving 1140 conserved genes, revealed a very close phylogenetic relatedness among members of this species. Furthermore, low genomic variability between strains was also confirmed by an average nucleotide identity analysis showing values higher than 98.2%. Investigating the genetic features of each strain, few putative functional mobile elements were identified. Besides, a consistent occurrence of defense mechanisms such as CRISPR-Cas and restriction-modification systems may be responsible for the high genome synteny identified among members of this taxon.

Salivary parameters and oral health status amongst adolescents in Mexico

Background

In the last years an increased interest in the use of salivary parameters in connection with caries experience and caries prediction has been shown. In schoolchildren investigations are known, where the relationship between caries prevalence and salivary parameters has been assessed, but in the adolescent population studies are scarce. The aim of the study was evaluate of the association among salivary parameters, oral health status and caries experience in adolescents in Mexico.

Methods

A cross-sectional study was conducted on 256 (DMFT≥5) and 165 (DMFT< 5) 12-to- 14-year-old adolescents. From all the adolescents, unstimulated mid-morning saliva samples were collected, after which the salivary flow rate was calculated, and the salivary pH and buffer capacity was measured. The caries was evaluated via the application of the DMFT score. Clinical variables such as oral hygiene and dental calculus were examined in the adolescent’s oral cavity. The adolescents provided data on their personal characteristics by completing a questionnaire, while socioeconomic data were collected from their parents. Descriptive, bivariate and logistic regression model analyses were performed.

Results

The prevalence of caries was 61.1% (DMFT≥5) in permanent dentition, with 72.7% of subjects presenting poor oral hygiene. The mean levels of salivary flow rate, pH, and buffer capacity was significantly lower (p < 0.05) in adolescents with caries score of DMFT≥5 than in those with caries score of DMFT < 5. Salivary flow and buffer capacity were higher in boys than in girls. The logistic regression model applied showed that adolescents with a salivary flow rate < 1 ml per min were more likely to present caries [OR = 1.58 (CI95% 1.04–2.40); p = 0.033] than adolescents with a flow rate ≥ 1 ml per-min, and that, for each unit of increased pH, the probability of presenting caries reduced by 76% [OR = 0.24 (CI95% 0.10–0.55); p = 0.001].

Conclusion

Significant association was found in salivary flow rate, pH and buffer capacity in adolescents with caries (DMFT≥5). In addition to differences of these parameters by sex, the results suggest saliva parameters may act as indicators of caries in adolescents.

Bifidobacterium β-Glucosidase Activity and Fermentation of Dietary Plant Glucosides Is Species and Strain Specific

Dietary plant glucosides are phytochemicals whose bioactivity and bioavailability can be modified by glucoside hydrolase activity of intestinal microbiota through the release of acylglycones. Bifidobacteria are gut commensals whose genomic potential indicates host-adaption as they possess a diverse set of glycosyl hydrolases giving access to a variety of dietary glycans. We hypothesized bifidobacteria with β-glucosidase activity could use plant glucosides as fermentation substrate and tested 115 strains assigned to eight different species and from different hosts for their potential to express β-glucosidases and ability to grow in the presence of esculin, amygdalin, and arbutin. Concurrently, the antibacterial activity of arbutin and its acylglycone hydroquinone was investigated. Beta-glucosidase activity of bifidobacteria was species specific and most prevalent in species occurring in human adults and animal hosts. Utilization and fermentation profiles of plant glucosides differed between strains and might provide a competitive benefit enabling the intestinal use of dietary plant glucosides as energy sources. Bifidobacterial β-glucosidase activity can increase the bioactivity of plant glucosides through the release of acylglycone.

Gene expression profile of Scardovia spp. in the metatranscriptome of root caries

A few investigations of caries biofilms have identified Scardovia spp.; however, little is known about its involvement in caries pathogenesis. The purpose of this study was to assess the gene expression profile of Scardovia spp. in root caries, and compare it with other microorganisms. Clinical samples from active root caries lesions were collected. Microbial mRNA was isolated and cDNA sequenced. The function and composition of the Scardovia were investigated using two methods: a) de novo assembly of the read data and mapping to contigs, and b) reads mapping to reference genomes. Pearson correlation was performed (p < 0.05). Proportion of Scardovia inopinata and Scardovia wiggsiae sequences ranged from 0-6% in the root caries metatranscriptome. There was a positive correlation between the transcriptome of Lactobacillus spp. and Scardovia spp. (r = 0.70; p = 0.03), as well as with other Bifidobacteriaceae (r = 0.91; p = 0.0006). Genes that code for fructose 6-phosphate phosphoketolase (the key enzyme for "Bifid shunt"), as well as ABC transporters and glycosyl-hydrolases were highly expressed. In conclusion, "Bifid shunt" and starch metabolism are involved in carbohydrate metabolism of S. inopinata and S. wiggsiae in root caries. There is a positive correlation between the metabolism abundance of Lactobacillus spp., Bifidobacteriaceae members, and Scardovia in root caries.

Quantitative assessment of Scardovia wiggsiae from dental plaque samples of children suffering from severe early childhood caries and caries free children

Scardovia wiggsiae has recently been identified as a potential pathogen associated with dental caries. The aim of the present study was to detect and quantify S. wiggsiae from dental plaque samples of children suffering from severe early childhood caries and children who were caries free by employing a real time DNA polymerase chain reaction (Real-time PCR) method. Dental plaque samples were collected from children suffering from severe early childhood caries (S-ECC) (n = 30) and caries free children (CF) (n = 30) reporting to the out-patient clinics of the department of paediatric and preventive dentistry. Plaque samples from each group were subjected to real-time PCR, post DNA extraction. Both the groups showed the presence of the organism S. wiggsiae, however there was a significant difference in its quantification between groups, with the median number being 1.49 × 10⁸ cells per ml in caries free samples compared to 1.40 × 10⁹ cells per ml in S-ECC samples. S. wiggsiae were isolated from nearly all samples of children, both caries free and those suffering from S-ECC. However, their numbers differ drastically in both groups with the scales tipping towards the S-ECC group, proving their association with the disease process in a significant manner. The present study shows significant association of S. wiggsiae in severe early childhood caries.

Deep sequencing of biofilm microbiomes on dental composite materials

Background: The microbiome on dental composites has not been studied in detail before. It has not been conclusively clarified whether restorative materials influence the oral microbiome. Methods: We used Illumina Miseq next-generation sequencing of the 16S V1-V2 region to compare the colonisation patterns of bovine enamel (BE) and the composite materials Grandio Flow (GF) and Grandio Blocs (GB) after 48 h in vivo in 14 volunteers. Applying a new method to maintain the oral microbiome ex vivo for 48 h also, we compared the microbiome on GF alone and with the new antimicrobial substance carolacton (GF+C). Results: All in vitro biofilm communities showed a higher diversity and richness than those grown in vivo but the very different atmospheric conditions must be considered. Contrary to expectations, there were only a few significant differences between BE and the composite materials GB and GF either in vivo or in vitro: Oribacterium, Peptostreptococcaceae [XI][G-1] and Streptococcus mutans were more prevalent and Megasphaera, Prevotella oulorum, Veillonella atypica, V. parvula, Gemella morbillorum, and Fusobacterium periodonticum were less prevalent on BE than on composites. In vivo, such preferences were only significant for Granulicatella adiacens (more prevalent on BE) and Fusobacterium nucleatum subsp. animalis (more prevalent on composites). On DNA sequence level, there were no significant differences between the biofilm communities on GF and GF+C. Conclusion: We found that the oral microbiome showed an increased richness when grown on various composites compared to BE in vitro, but otherwise changed only slightly independent of the in vivo or in vitro condition. Our new ex vivo biofilm model might be useful for pre-clinical testing of preventive strategies.

In Sickness and in Health-What Does the Oral Microbiome Mean to Us? An Ecological Perspective

The oral microbiome is natural and has a symbiotic relationship with the host by delivering important benefits. In oral health, a dynamic balance is reached between the host, the environment, and the microbiome. However, the frequent intake of sugar and/or reductions in saliva flow results in extended periods of low pH in the biofilm, which disrupts this symbiotic relationship. Such conditions inhibit the growth of beneficial species and drive the selection of bacteria with an acid-producing/acid-tolerating phenotype, thereby increasing the risk of caries (dysbiosis). A more detailed understanding of the interdependencies and interactions that exist among the resident microbiota in dental biofilms, and an increased awareness of the relationship between the host and the oral microbiome, is providing new insights and fresh opportunities to promote symbiosis and prevent dysbiosis. These include modifying the oral microbiome (e.g., with prebiotics and probiotics), manipulating the oral environment to selectively favor the growth of beneficial species, and moderating the growth and metabolism of the biofilm to reduce the likelihood of dysbiosis. Evidence is provided to suggest that the regular provision of interventions that deliver small but relevant benefits, consistently over a prolonged period, can support the maintenance of a symbiotic oral microbiome.

Correlation between relative bacterial activity and lactate dehydrogenase gene expression of co-cultures in vitro

OBJECTIVES

The present study aims at correlating the relative bacterial activity with the H⁺ concentration and the ldh expression of caries-associated bacteria in co-cultures.

MATERIALS AND METHODS

Well plates were prepared with BHI medium and cultures of Lactobacillus paracasei and Fusobacterium nucleatum. Bacterial growth at 37 °C was measured using a microplate-photometer before and after adding sucrose to the samples. Samples of co-cultures (n = 12) and single-species cultures (n = 3) were taken and pH was assessed. Real-time quantitative PCRs were applied targeting the 16S-gene, the 16S-rRNA, the ldh-gene, and the ldh-mRNA.

RESULTS

For L. paracasei with sucrose, an increase in relative bacterial activity (62.8% ± 23.5% [mean, SE]) was observed, while F. nucleatum showed a clear decrease in relative bacterial activity (- 35.0% ± 9.6%). Simultaneously, the H⁺ concentration increased (1.15E-05 mol*l-1 ± 4.61E-07 mol*l-1). Consequently, a significant positive correlation was found between L. paracasei's relative bacterial activity and H⁺ concentration (Spearman rank correlation, r = 0.638; p = 0.002), while F. nucleatum exhibited a negative correlation (r = - 0.741; p ≤ 0.001). Furthermore L. paracasei with sucrose showed a moderate, but significant positive correlation between relative bacterial activity and ldh-expression (r = 0.307; p = 0.024).

CONCLUSIONS AND CLINICAL RELEVANCE

The relative bacterial activity after sucrose pulse showed a significant correlation not only to the acid production (H⁺ concentration) but also to ldh expression of L. paracasei. However, further research is required to confirm these findings in a mature biofilm in vivo.

Analysis of the antimicrobial and anti-caries effects of TiF4 varnish under microcosm biofilm formed on enamel

Titanium tetrafluoride (TiF4) is known for interacting with enamel reducing demineralization. However, no information is available about its potential antimicrobial effect.

OBJECTIVES

This study evaluated the antimicrobial and anti-caries potential of TiF4 varnish compared to NaF varnish, chlorhexidine gel (positive control), placebo varnish and untreated (negative controls) using a dental microcosm biofilm model.

MATERIAL AND METHODS

A microcosm biofilm was produced on bovine enamel previously treated with the varnishes, using inoculum from human saliva mixed with McBain saliva, under 0.2% sucrose exposure, for 14 days. All experiments were performed in biological triplicate (n=4/group in each experiment). Factors evaluated were: bacterial viability (% dead and live bacteria); CFU counting (log10 CFU/mL); and enamel demineralization (transverse microradiography - TMR). Data were analysed using ANOVA/Tukey's test or Kruskal-Wallis/Dunn's test (p<0.05).

RESULTS

Only chlorhexidine significantly increased the number of dead bacteria (68.8±13.1% dead bacteria) compared to untreated control (48.9±16.1% dead bacteria). No treatment reduced the CFU counting (total microorganism and total streptococci) compared to the negative controls. Only TiF4 was able to reduce enamel demineralization (ΔZ 1110.7±803.2 vol% μm) compared to both negative controls (untreated: ΔZ 4455.3±1176.4 vol% μm).

CONCLUSIONS

TiF4 varnish has no relevant antimicrobial effect. Nevertheless, TiF4 varnish was effective in reducing enamel demineralization under this model.

Beyond Streptococcus mutans: clinical implications of the evolving dental caries aetiological paradigms and its associated microbiome

Aetiological concepts of dental caries have evolved over the years from being considered as a disease initiated by nonspecific microorganisms, to being regarded as an 'infectious' disease caused by specific bacteria, to the current paradigms that emphasise a 'mixed bacterial-ecological approach' as being responsible for lesion initiation and pathogenesis. These aetiological paradigms are not just intellectual concepts but have important implications on how clinicians manage this age-old disease in the twenty-first century. Despite evidence-backed recommendations for adopting more biological measures to counter the disease, a significant proportion of dentists continue following traditional caries management guidelines in their daily clinical practice. This paper will review the evolving dental caries aetiological concepts and highlight the current evidence for adopting a more ecological approach to caries prevention, risk assessment, and treatment.

Microbial Complexes and Caries in 17-Year-Olds with and without Streptococcus mutans

Streptococcus mutans is a key bacterial species in the caries process, which affects >90% of the population worldwide. However, other acidogenic and aciduric/acidophilic species may contribute to disease development. In Sweden, a country with low prevalences of caries and S. mutans, a significant portion of caries-affected adolescents lack detectable levels of S. mutans. The objectives of the present study were 1) to characterize the tooth biofilm and saliva microbiota of adolescents with caries disease, with or without detectable S. mutans, from tooth biofilm and saliva samples and 2) to assess taxa clustering in the tooth biofilm and saliva samples and relate this information to caries status. For 17-y-old participants ( N = 154), enamel and dentin caries (the total number of present carious surfaces in the enamel and dentin) and caries experience (the number of decayed and filled tooth surfaces) were recorded, dental biofilm and saliva samples obtained, and information on medical and lifestyle habits collected. Multiplex 16S rDNA (V3-V4) sequencing of bacterial DNA was performed with the Illumina MiSeq platform. The Human Oral Microbiome Database and the ProbeSeq pipeline were used in the HOMI NGS procedure. In subjects with caries experience, high levels of S. mutans were associated with a few species and low levels with a panel of saccharolytic species. Present caries was similarly associated with a panel of saccharolytic species in subjects without S. mutans. Furthermore, tooth biofilm microbiota could be used to establish 4 clusters of subjects with different caries experiences. In particular, high levels of S. mutans were associated with the presence of a few influential species in multivariate modeling, including Scardovia wiggsiae. By contrast, a panel of less avid lactic acid-producing species was influential in patients with undetectable or low S. mutans levels in such modeling. These findings support a prominent role of S. mutans in infected adolescents but also the ecologic concept, especially in S. mutans-free subjects.

Oral microbial profiles of individuals with different levels of sugar intake

The aim was to compare the oral microbial profiles in young adults with an intake of free sugars above or below the current recommendations by the WHO for sugar consumption. Seventy subjects completed a Quantitative Food Frequency Questionnaire to establish the proportion of free sugars in relation to the total energy intake (% E). Subjects with <5% E (n = 30) formed the low-sugar group, while those with ≥5% E (n = 40) were regarded as reference group. Saliva and plaque samples were analyzed by qPCR, and 52 of the plaque samples were assayed by HOMINGS. The HOMINGS analysis revealed a comparable core microbiota in plaque samples with Streptococcus, Leptotrichia, Actinobaculum, and Veillonella as predominant. No major differences between groups were revealed by α-diversity testing (p = 0.83), principal component analysis, or correspondence analysis. Higher relative abundance of Streptococcus sobrinus and Prevotella melaninogenica was observed in plaque samples in the reference group. By qPCR, Scardovia wiggsiae was associated with elevated sugar intake. The findings suggests that the amount of ingested sugars had a marginal influence on microbial profiles in dental plaque and saliva. However, some caries-associated species were less abundant in the dental plaque of the low sugar group.

Saliva and tooth biofilm bacterial microbiota in adolescents in a low caries community

The oral cavity harbours a complex microbiome that is linked to dental diseases and serves as a route to other parts of the body. Here, the aims were to characterize the oral microbiota by deep sequencing in a low-caries population with regular dental care since childhood and search for association with caries prevalence and incidence. Saliva and tooth biofilm from 17-year-olds and mock bacteria communities were analysed using 16S rDNA Illumina MiSeq (v3-v4) and PacBio SMRT (v1-v8) sequencing including validity and reliability estimates. Caries was scored at 17 and 19 years of age. Both sequencing platforms revealed that Firmicutes dominated in the saliva, whereas Firmicutes and Actinobacteria abundances were similar in tooth biofilm. Saliva microbiota discriminated caries-affected from caries-free adolescents, with enumeration of Scardovia wiggsiae, Streptococcus mutans, Bifidobacterium longum, Leptotrichia sp. HOT498, and Selenomonas spp. in caries-affected participants. Adolescents with B. longum in saliva had significantly higher 2-year caries increment. PacBio SMRT revealed Corynebacterium matruchotii as the most prevalent species in tooth biofilm. In conclusion, both sequencing methods were reliable and valid for oral samples, and saliva microbiota was associated with cross-sectional caries prevalence, especially S. wiggsiae, S. mutans, and B. longum; the latter also with the 2-year caries incidence.

Microbiomes of Site-Specific Dental Plaques from Children with Different Caries Status

The oral microbiota associated with the initiation and progression of dental caries has yet to be fully characterized. The Human Oral Microbe Identification Using Next-Generation Sequencing (HOMINGS) approach was used to analyze the microbiomes of site-specific supragingival dental plaques from children with different caries status. Fifty-five children (2 to 7 years of age) were assessed at baseline and at 12 months and grouped as caries free (CF), caries active with enamel lesions (CAE), and caries active with dentin carious lesions (CA). Plaque samples from caries-free tooth surfaces (PF) and from enamel carious lesions (PE) and dentin carious lesions (PD) were collected. 16S community profiles were obtained by HOMINGS, and 408 bacterial species and 84 genus probes were assigned. Plaque bacterial communities showed temporal stability, as there was no significant difference in beta diversity values between the baseline and 12-month samples. Irrespective of collection time points, the microbiomes of healthy tooth surfaces differed substantially from those found during caries activity. All pairwise comparisons of beta diversity values between groups were significantly different (P < 0.05), except for comparisons between the CA-PF, CAE-PE, and CA-PE groups. Streptococcus genus probe 4 and Neisseria genus probe 2 were the most frequently detected taxa across the plaque groups, followed by Streptococcus sanguinis, which was highly abundant in CF-PF. Well-known acidogenic/aciduric species such as Streptococcus mutans, Scardovia wiggsiae, Parascardovia denticolens, and Lactobacillus salivarius were found almost exclusively in CA-PD. The microbiomes of supragingival dental plaque differ substantially among tooth surfaces and children of different caries activities. In support of the ecological nature of caries etiology, a steady transition in community species composition was observed with disease progression.

Salivary microbiome of an urban Indian cohort and patterns linked to subclinical inflammation

OBJECTIVE

To profile salivary microbiomes of an urban-living, healthy Indian cohort and explore associations with proinflammatory status.

METHODS

Fifty-one clinically healthy Indian subjects' salivary microbiomes were analyzed using 16S rRNA Illumina MiSeq sequencing. Community distribution was compared with salivary data from the Human Microbiome Project (HMP). Indian subjects were clustered using microbiome-based "partitioning along medoids" (PAM), and relationships of interleukin-1 beta levels with community composition were analyzed.

RESULTS

Indian subjects presented higher phylogenetic diversity than HMP. Several taxa associated with traditional societies gut microbiomes (Bacteroidales, Paraprevotellaceae, and Spirochaetaceae) were raised. Bifidobacteriaceae and Lactobacillaceae were approximately fourfold greater. A PAM cluster enriched in several Proteobacteria, Actinobacteria, and Bacilli taxa and having almost twofold higher Prevotella to Bacteroides ratio showed significant overrepresentation of subjects within the highest quartile of salivary interleukin-1 beta levels. Abiotrophia, Anaerobacillus, Micrococcus, Aggregatibacter, Halomonas, Propionivivrio, Paracoccus, Mannhemia, unclassified Bradyrhizobiaceae, and Caulobacteraceae were each significant indicators of presence in the highest interleukin-1 beta quartile. 2 OTUs representing Lactobacillus fermentum and Cardiobacterium hominis significantly correlated with interleukin-1 beta levels.

CONCLUSION

The salivary microbiome of this urban-dwelling Indian cohort differed significantly from that of a well-studied Western cohort. Specific community patterns were putatively associated with subclinical inflammation levels.

Acidogenicity of dual-species biofilms of bifidobacteria and Streptococcus mutans

OBJECTIVE

The aim of this study was to evaluate the acidogenicity of dual-species biofilms of bifidobacteria and Streptococcus mutans.

MATERIALS AND METHODS

The following strains were tested: Bifidobacterium dentium DSM20436, Parascardovia denticolens DSM10105, and Scardovia inopinata DSM10107. Streptococcus mutans UA159 and Lactobacillus acidophilus ATCC4356 were used as control. Bifidobacteria were studied planktonically as they were not able to form monospecies biofilm, they were grown in biofilms associated with S. mutans. Endogenous polysaccharide reserves of cultures at log phase were depleted. Standardized suspensions of the microorganisms were incubated in growth media supplemented with 10 mM glucose, lactose, raffinose, glucose, or xylitol. S. mutans biofilms were grown on glass cover slips for 24 h to which bifidobacteria were added. After 24 h, the dual-species biofilms were exposed to the same carbon sources, and after 3 h, the pH of spent culture media and concentrations of organic acids were measured. Statistical analyses were carried out using ANOVA and Tukey's test (α = 0.05).

RESULTS

A higher pH drop was observed when S. mutans was associated with P. denticolens or S. inopinata, in either planktonic or biofilm cultures, than with S. mutans alone. Bifidobacteria showed a higher pH drop in the presence of raffinose than S. mutans or L. acidophilus.

CONCLUSIONS

Dual-species biofilms of bifidobacteria and S. mutans produced more acid and greater pH drops than biofilms of S. mutans alone.

CLINICAL RELEVANCE

New insights on the complex process of caries pathogenicity contribute to the establishment of preventive and therapeutic measures, in particular in specific cases, such as in early childhood caries.

Analysis of Bacterial Activity in Sound and Cariogenic Biofilm: A Pilot in vivo Study

Dental caries is a multifactorial disease with many associated microbial taxa, but only a few are notably contributing to acidogenicity. The ribosome number and the corresponding 16S ribosomal RNA (rRNA) concentration are considered a molecular indicator for general metabolic activity of bacteria, as they are elevated with increased anabolic and catabolic activities. We hypothesize that the activity of aciduric/acidogenic bacterial taxa, reflected by a rise in ribosomal counts, could resolve differences between plaque biofilm from sound surfaces and caries lesions. The included subjects were allocated to two groups: caries-free (CF) or caries-active (CA). CF subjects presented one donor site, namely one sound surface (CFS, n = 10), whereas CA subjects presented two donor sites: a cavitated lesion with an ICDAS score of 5-6 (CAC, n = 13), and a sound reference surface (CAS, n = 13). Four aciduric/acidogenic bacterial taxa (Streptococcus mutans, lactobacilli, Bifidobacterium dentium, and Scardovia wiggsiae) and one asaccharolytic taxon (fusobacteria) as a contrast were selected. 16S rRNA and 16S rRNA genes were quantified by quantitative PCR. Based on these parameters, bacterial and ribosomal counts, as well as relative activities were calculated as the quotient of relative ribosomal abundance and relative genome abundance. Caries-associated bacteria showed the highest relative activity in caries lesions (e.g. lactobacilli CAC: 177.5 ± 46.0%) and lower activities on sound surfaces (e.g. lactobacilli CAS: 96.3 ± 31.5%), whereas asaccharolytic fusobacteria were most active on sound surfaces and less active in caries lesions (CFS: 275.7 ± 171.1%; CAS: 205.8 ± 114.3%; CAC: 51.1 ± 19.0%). Thus, the present study suggests different activity patterns for biofilms from CF and CA individuals.