Quantitative assessment of salivary oral bacteria according to the severity of dental caries in childhood

Effect of fluoride varnishes on oral bacteria of preschool children with cavitated and non-cavitated carious lesions: randomized clinical trial

We compare the effect of calcium and phosphate-containing sodium fluoride (NaF) varnishes to conventional NaF varnish on S. mutans and L. fermentum counts. 3-4 years old children were grouped according to their caries status (n = 45 each): caries-free, with non-cavitated and with cavitated lesions. Each group was randomly subdivided (n = 15 each) into: Group 1- 5% NaF, Group 2- 5% NaF with tricalcium phosphate, Group 3- 5% NaF with casein phosphopeptide- amorphous calcium phosphate. Biofilm and saliva were collected to quantify microorganisms at baseline (T1) and 24-months (T2). Differences between groups were compared using Kruskal-Wallis test, followed by Dunn-Bonferroni post-test, at 0.0167 α-level. Significant difference was found for percentage of children with detectable biofilm L. fermentum (p = 0.013) at T1 and salivary S. mutans (p = 0.011) at T2. Percentage of children increased from T1 to T2 in Group 2 with salivary S. mutans (p = 0.007), salivary L. fermentum (p = 0.035), and biofilm L. fermentum (p = 0.019) and in Group 3 with salivary L. fermentum (p = 0.035). Bacterial change was not significant in both samples of intervention groups, except increase in salivary S. mutans (p = 0.038) in Group 3. Both calcium- and phosphate-containing NaF varnishes demonstrated similar antibacterial effect on S. mutans and L. fermentum compared to conventional NaF varnish.

Salivary levels of five microorganisms of root caries in nursing home elderly: a preliminary investigation

BACKGROUND

Streptococcus, Bifidobacteria, Lactobacillus and Actinomyces are acidogenic aciduria that may be associated with root caries (RC). The aim of the study was to analyze Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), Bifidobacterium spp., Lactobacillus spp. and Actinomyces naeslundii (A. naeslundii) in the saliva of nursing home elderly, to assess the correlation between bacterial composition and RC for five putative catiogenic organisms.

METHODS

In this study, we collected 43 saliva samples and divided into two groups: the root caries group (RCG, n = 21) and the caries-free group (CFG, n = 22). Bacterial DNA was extracted from the saliva samples. The presence and abundance of the five microorganisms were detected by Quantitative real-time PCR (qPCR). Spearman correlation test was performed to evaluate the relationship between the numbers of root decayed filled surfaces (RDFS) and root caries index (RCI) and salivary levels of the bacteria.

RESULTS

The salivary levels of S. mutans, S. sobrinus, Bifidobacterium spp. and Lactobacillus spp. were significantly higher in RCG than in CFG (p < 0.05). RDFS and RCI (RDFS/RCI) were positively associated with salivary levels of S. mutans, S. sobrinus and Bifidobacterium spp. (r = 0.658/0.635, r = 0.465/0.420 and r = 0.407/0.406, respectively). No significant differences in presence and amounts of A. naeslundii was observed between the two groups (p > 0.05).

CONCLUSION

S. mutans, S. sobrinus and Bifidobacterium spp. in saliva appear to be associated with RC in the elderly. Taken together, the findings indicate that specific salivary bacteria may be involved in the progression of RC.

Quantitative analysis of salivary and biofilm bacteria associated with cavitated and non-cavitated carious lesions in pre-school children

OBJECTIVE

To quantify and compare Streptococcus mutans (S. mutans) and Lactobacillus fermentum (L. fermentum) in saliva and biofilm of caries-free children to those with cavitated and non-cavitated lesions.

DESIGN

One hundred and thirty-five 3-4 years old children were grouped (n = 45 in each group) according to their caries status: Clinical examination was done by a calibrated examiner. Biofilm and saliva were collected to quantify the microorganisms using qRT-PCR. The decayed-missing-filled surfaces (dmfs) was calculated by adding the number of decayed (ICDAS-II score 3-6), filled (ICDAS-II score 7 and 8) and missing (ICDAS-II score 9) surfaces due to caries. The correlation between the bacterial amounts and the number of carious surfaces was evaluated using Spearman's correlation coefficient. The levels and proportions of the microorganisms were compared using the Kruskal-Wallis test at an α-level of 0.05.

RESULTS

The quantity of S. mutans and L. fermentum was significantly higher in saliva and biofilm of children with cavitated lesions, followed by those with non-cavitated lesions and the lowest in caries-free children. Also, salivary and biofilm S. mutans, along with biofilm L. fermentum levels, significantly correlated with the number of non-cavitated surfaces; while salivary and biofilm S. mutans and L. fermentum levels significantly correlated with the number of cavitated surfaces. Additionally, dmfs scores significantly correlated with the salivary and biofilm S. mutans and L. fermentum levels.

CONCLUSIONS

S. mutans and L. fermentum in saliva and biofilm samples are associated with caries lesion severity.

Third-generation sequencing-selected Scardovia wiggsiae promotes periodontitis progression in mice

BACKGROUNDS

Periodontitis is an oral-bacteria-directed disease that occurs worldwide. Currently, periodontal pathogens are mostly determined using traditional culture techniques, next-generation sequencing, and microbiological screening system. In addition to the well-known and cultivatable periodontal bacteria, we aimed to discover a novel periodontal pathogen by using DNA sequencing and investigate its role in the progression of periodontitis.

OBJECTIVE

This study identified pathogens from subgingival dental plaque in patients with periodontitis by using the Oxford Nanopore Technology (ONT) third-generation sequencing system and validated the impact of selected pathogen in periodontitis progression by ligature-implanted mice.

METHODS

Twenty-five patients with periodontitis and 25 healthy controls were recruited in this study. Subgingival plaque samples were collected for metagenomic analysis. The ONT third-generation sequencing system was used to confirm the dominant bacteria. A mouse model with ligature implantation and bacterial injection verified the pathogenesis of periodontitis. Neutrophil infiltration and osteoclast activity were evaluated using immunohistochemistry and tartrate-resistant acid phosphatase assays in periodontal tissue. Gingival inflammation was evaluated using pro-inflammatory cytokines in gingival crevicular fluids. Alveolar bone destruction in the mice was evaluated using micro-computed tomography and hematoxylin and eosin staining.

RESULTS

Scardovia wiggsiae (S. wiggsiae) was dominant in the subgingival plaque of the patients with periodontitis. S. wiggsiae significantly deteriorated ligature-induced neutrophil infiltration, osteoclast activation, alveolar bone destruction, and the secretion of interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α in the mouse model.

CONCLUSION

Our metagenome results suggested that S. wiggsiae is a dominant flora in patients with periodontitis. In mice, the induction of neutrophil infiltration, proinflammatory cytokine secretion, osteoclast activation, and alveolar bone destruction further verified the pathogenic role of S. wiggsiae in the progress of periodontitis. Future studies investigating the metabolic interactions between S. wiggsiae and other periodontopathic bacteria are warranted.

Dental caries and their microbiomes in children: what do we do now?

The oral cavity is an unique ecosystem formed by different structures, tissues, and a complex microbial community formed by hundreds of different species of bacteria, fungi, viruses, phages, and the candidate phyla radiation (CPR) group, all living in symbiosis with healthy individuals. In an opposite state, dental caries is a biofilm-mediated dysbiosis that involves changes in the core microbiome composition and function, which leads to the demineralization of tooth tissues due to the fermentation of dietary carbohydrates, producing acid by select oral bacteria. The cariogenic biofilm is typically characterized by bacterial species with the ability of adhering to the saliva-coated tooth surface, production of exopolysaccharides-rich matrix (which will limit the diffusion of acidic products of carbohydrate fermentation), and the ability of surviving in this acidic environment. Besides years of research and dental treatment, dental caries remains the most common chronic disease in children worldwide. This article aims to bring an insightful discussion about important questions that remain unanswered in the Cariology and Oral Microbiology fields, to move Science forward, characterize the interrelationships of these communities, and understand mechanistic functions between microorganisms and the host, therefore leading to translatable knowledge that benefits the provision of care to our pediatric patients.

Gain a Baby Lose a Tooth-Is There an Association between Periodontitis and Preterm Birth?

Preterm birth serves as one of the leading causes of neonatal mortality worldwide. The underlying mechanisms that contribute to preterm birth are not yet fully understood. However, an association between periodontitis and preterm birth has been proposed. The periodontal status and presence of periodontal pathogens in women with different birth outcomes have been previously examined. However, varying definitions of periodontitis and different microbiological methods make their interpretation challenging. The aim of this case-control study on women with and without preterm birth was to investigate their periodontal status using the current classification system for periodontal diseases. Moreover, differences in the periodontal microbiome of the study participants were investigated. Therefore, we collected data on oral and periodontal parameters in 77 puerperal women divided into two groups based on gestational age at delivery: 33 patients with preterm birth (PTB, <37 weeks) and 44 patients with term birth (TB, >37 weeks). These data included pocket probing depth (PPD), clinical attachment loss (CAL), bleeding on probing (BOP), gingival-bleeding index, DMFT index, and gynecologic and dental history. In addition, their oral microbiome was explored. Median CAL and percentage PPD ≥ 4 mm were significantly higher in the PTB group than in the TB group (p = 0.0128 and p = 0.047, respectively). Birth weight was significantly higher in periodontally healthy women than in those with gingivitis (p = 0.0078) or periodontitis (p = 0.0127). The periodontal microbiome differed significantly between groups. Our results are underlining the possible association between periodontitis and preterm delivery. Women with periodontitis had babies with significantly lower birth weights. The microbiome varied between the groups.

Analysis of a Pediatric Dental School Patient Population Revealed Increasing Trends of Limited English Proficiency (LEP) Patients: Implications for Pediatric Dental Public Health and Access to Care

Based upon the lack of current information regarding the pediatric patient population at UNLV-SDM, the overall goal of this project was to analyze the demographic characteristics of this population, indicators for socioeconomic status (SES), such as enrollment in Medicaid, and other barriers to healthcare access, such as non-English/non-Spanish languages spoken. Using an Institutional Review Board (IRB)-approved protocol, this analysis revealed the percentage of minority pediatric patients between 2010 and 2020 increased among African Americans, Asian Americans, and mixed or multiracial patients, while decreasing among Hispanics. Analysis of the Limited English Proficiency (LEP) patients and guardians found an overall increase in the number of non-English/non-Spanish languages spoken from n = 4 in 2010 to n = 21 in 2020 with no significant changes in Medicaid/CHIP enrollment identified between 2010 and 2020 (76.7%, 77.9%, p = 0.988). These data suggest the composition of the patient population has experienced significant shifts over time, with more patients of mixed racial backgrounds and increased numbers of Limited English Proficiency (non-English/non-Spanish foreign languages) spoken. These data may suggest there is an increased need for multilingual health materials, training, and translators for pediatric oral health within this population.

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.

Mutans Streptococci and Lactobacilli: Colonization Patterns and Genotypic Characterization of Cariogenic Bacterial Species in American Indian Children

Aim: The purpose of this study was to investigate the presence of Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus species in an American Indian population displaying a high incidence of severe early childhood caries (S-ECC) and to explore the genotypic diversity and fidelity of transmission of S. sobrinus in this population.

Methods: We report here on the microbial profiles of 71 children compiled from birth to 36 months of age and initial exploration of genotypic diversity in a subset of 40 mother/child dyads. Whole mouth plaque samples were collected from mother/child dyads in a Northern Plains American Indian cohort. Mutans streptococci (MS) and Lactobacillus counts were recorded and presence/absence of S. mutans, S. sobrinus, and Lactobacillus was noted for each child. S. sobrinus was isolated and genotyped via arbitrarily primed-polymerase chain reaction (AP-PCR).

Results: The children in this study were divided into caries active (CA) and caries free (CF) groups. S. mutans, S. sobrinus, and Lactobacillus species were detected more frequently in CA groups. Distribution of MS and Lactobacillus counts was significantly different between the two groups, as was the distribution of three species colonization profiles. Twelve S. sobrinus genotypes were detected in the subset of mother/child dyads. Individual participants displayed a range of 0–3 distinct genotypes while mother/child pairs displayed a range of 1–5 genotypes. Eighty-three percent of children shared at least one genotype with his/her mother.

Conclusion: Caries active children in this population display different microbial profiles than the caries free children in this cohort. A small number of S. sobrinus genotypes appear to be very common in this population. A high rate of vertical transmission of S. sobrinus from mother to child is seen in these mother/child dyads.

Quantification and gene expression of Lactobacillus casei group species associated with dentinal lesions in early childhood caries

Background

Considering that the Lactobacillus casei group is strongly associated with caries progression, the use of lactobacilli as probiotics must be balanced due to their possible involvement in dental caries.

Objective

This study aimed to detect and quantify L. paracasei, L. rhamnosus, and L. casei group species in the active and arrested dentinal lesions of preschoolers. It also aimed to determine the expression profiles of lactobacilli genes related to adhesion, extracellular polymeric substance regulation, and pyruvate oxidation.

Methods

Total ribonucleic acid (RNA) was extracted from dentinal lesion samples (25 active, 13 arrested) of children between 2 and 5 years of age. The samples were converted to complementary deoxyribonucleic acid (cDNA), and quantitative polymerase chain reaction (qPCR) analyses were performed to quantify and determine the relative abundance (measured by percentage of total bacteria) of L. paracasei, L. rhamnosus, and L. casei group species. The expression profiles of L. paracasei/casei genes (spaC and spxB) and L. rhamnosus genes (spaE and wzb) were assessed. The Student t-test and the Mann-Whitney U test were used for comparisons.

Results

The L. casei group species were found to be part of the viable microbial community in dentinal caries. L. paracasei (p = 0.001), L. rhamnosus (p = 0.022), and L. casei (p = 0.004) group species were abundant in the active dentinal lesions compared to the arrested dentinal lesions. Only the wzb gene (p = 0.006) exhibited a statistically significant difference between the active and arrested lesions in terms of its expression profile; it was expressed to a higher extent in the active dentinal lesions.

Conclusions

The L. casei group species presented in large numbers in the active dentinal caries lesions, indicating that these microorganisms are related to caries activity, and the wzb gene may play an important role in caries progression.

Quantitative Analysis of Salivary Oral Bacteria Associated with Severe Early Childhood Caries and Construction of Caries Assessment Model

To construct a saliva-based caries risk assessment model, saliva samples from 176 severe early childhood caries (S-ECC) children and 178 healthy (H) children were screened by real-time PCR-based quantification of the selected species, including Streptococcus mutans, Prevotella pallens, Prevotella denticola and Lactobacillus fermentum. Host factors including caries status, dmft indices, age, gender, and geographic origin were assessed in their influence on abundance of the targeted species, which revealed host caries status as the dominant factor, followed by dmft indices (both P < 0.01). Moreover, levels of S. mutans and P. denticola in the S-ECC group were significantly higher than those in the healthy group (P < 0.001 for S. mutans and P < 0.01 for P. denticola). Interestingly, the co-occurrence network of these targeted species in the S-ECC group differed from that from the healthy group. Finally, based on the combined change pattern of S. mutans and P. pallens, we constructed an S-ECC diagnosis model with an accuracy of 72%. This saliva-based caries diagnosis model is of potential value for circumstances where sampling dental plague is difficult.

Sugar Metabolism of Scardovia wiggsiae, a Novel Caries-Associated Bacterium

Scardovia wiggsiae has been detected from caries in children and adolescents and has been suggested to be a caries-associated microorganism. To investigate the cariogenic potential of S. wiggsiae, we examined carbohydrate metabolism and acid productivity, the fluoride sensitivity of carbohydrate metabolism and the mechanism by which fluoride inhibits carbohydrate metabolism, and the acid sensitivity of carbohydrate metabolism in this bacterium. S. wiggsiae metabolized glucose and reduced the environmental pH to 3.5. It mainly produced acetic acid from glucose, together with small amounts of lactic and formic acid. The 50% inhibitory concentration of fluoride for acid production was 8.0 mM at pH 7.0 and 1.5 mM at pH 5.5, which were much higher than those of representative caries-associated bacteria, such as Streptococcus mutans. Metabolomic profiles showed the accumulation of 3-phosphoglycerate and a marked reduction in the pyruvate concentration in the presence of fluoride, suggesting that fluoride inhibits the latter half of glycolysis, including enolase activity. Enolase activity was inhibited by fluoride in S. wiggsiae, but it was more fluoride-tolerant than the enolase activity of S. mutans. Unlike in S. mutans, lactic acid did not inhibit acid production by S. wiggsiae at acidic pH. These results indicate that S. wiggsiae exhibits high acid production and tolerance to fluoride and lactic acid. S. wiggsiae possesses a unique metabolic pathway, the F6PPK shunt, which might allow it to avoid the lactate-formate pathway, including fluoride-sensitive enolase activity, and enable metabolic flow to the fluoride-tolerant acetate pathway. The fluoride tolerance of S. wiggsiae's enolase activity also increases the fluoride tolerance of its carbohydrate metabolism. The lactic acid tolerance of S. wiggsiae's acid production might result in S. wiggsiae having high acidogenic and aciduric potential and make it ecologically competitive in acidic environments, such as caries lesions, where lactic acid predominates.

Relationship Between Mutans Streptococci and Lactobacilli in the Oral Cavity and Intestine of Obese and Eutrophic Children With Early Childhood Caries-Preliminary Findings of a Cross-Sectional Study

This brief communication assessed whether there was any relationship between the counts of lactobacilli (LB) and mutans streptococci (MS) in the oral cavity and intestine of obese and eutrophic children with early childhood caries (ECC). Seventy-eight preschoolers were assigned into the following groups: 1. obese children with ECC (OECC), 2. eutrophic children with ECC (EECC), 3. obese caries-free children (OCF), and 4. eutrophic caries-free children (ECF). The diagnosis of obesity and ECC was based on the World Health Organization criteria. Dental plaque and fecal samples were collected to assess the counts of MS and LB using selective media. Data were evaluated by Poisson regression analysis, Wilcoxon test, and Sign test. Microbial indicators of ECC in obese children were MS counts in the intestine [rate ratio (RR): 4.38] and presence of LB in the oral cavity (RR: 2.12). The indicators in eutrophic children were MS levels and the presence of LB, both in the oral cavity (RR: 6.35/1.50) and intestine (RR: 2.35/2.38) (p < 0.05). The comparison between MS levels in the mouth and in the intestine revealed significant differences only in the ECF group (p = 0.04). Regarding LB presence in the mouth vs. in the intestine, except for the OCF group (p = 0.03), no other statistical differences were found. Our preliminary findings highlighted that the levels of MS and the presence of LB in the oral cavity, as well as in the lower gastrointestinal tract were associated with ECC. Moreover, obesity was found to influence this relationship.

Morphological identification of Streptococcus mutans and Streptococcus sobrinus in SB-20M culture medium has efficiency comparable to proteomic identification by the MALDI-TOF mass spectrometry technique

OBJECTIVES

The objective of this study was to evaluate the efficiency of SB-20 M culture medium to perform differential morphological identification of S. mutans and S. sobrinus compared to biochemical identification and to proteomic identification by the MALDI-TOF mass spectrometry technique.

MATERIAL AND METHODS

Unstimulated saliva samples from 266 dental students were seeded on SB-20 M culture medium by the wooden spatula technique. After incubation, S. mutans and S. sobrinus colonies were identified by stereomicroscopy based on their differential morphological characteristics. Following these procedures, 135 colonies with characteristic morphology of S. mutans (89 colonies) and S. sobrinus (46 colonies) were randomly selected, submitted to biochemical identification (biotyping) and proteomic identification by the MALDI-TOF mass spectrometry technique. The results were compared using the Kappa test, with a 5% significance level.

RESULTS

All (100%) S. mutans colonies were correctly identified after culture in SB-20 M medium compared to biotyping and proteomic identification. For S. sobrinus, morphological identification in SB-20 M medium was correct for 43 colonies (93.5%) compared to biotyping and proteomic identification. However, there was no statistically significant difference when comparing the capacity to identify S. mutans and S. sobrinus of the three techniques (p < 0.001; K = 0.951).

CONCLUSIONS

It was concluded that the SB-20 M culture medium for morphological identification of S. mutans and S. sobrinus was highly reliable, being comparable to the MALDI-TOF mass spectrometry technique.

CLINICAL RELEVANCE

The efficiency evaluation of identification methods of S. mutans and S. sobrinus is clinically relevant in order to determine caries risk and activity of patients.

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.

Quantitative analysis of biofilm bacteria according to different stages of early childhood caries

OBJECTIVE

Monitoring selected key species related to health or disease may facilitate caries risk assessment and discovery of novel ecological preventive and therapeutic approaches. This study aimed at quantifying Actinomyces naeslundii, Bifidobacterium spp., Lactobacillus acidophilus, Lactobacillus casei group, Streptococcus gordonii, Mitis group and Streptococcus mutans by quantitative polymerase chain reaction (qPCR) in dental biofilm from Brazilian children with different stages of early childhood caries (ECC).

DESIGN

Seventy-five preschool children were clinically evaluated by ICDAS criteria and divided into groups: caries-free (CF; n = 20), enamel caries lesions (ECL; n = 17) and dentine caries lesions (DCL; n = 38). Plaque samples from all children were collected for detection and quantification of the selected bacteria.

RESULTS

L. acidophilus and L. casei group were absent in almost all plaque samples. No differences in relative proportions of A. naeslundii, Mitis group and S. gordonii were observed in any stage of caries. However, S. mutans and Bifidobacterium spp. were present at higher concentrations in the biofilm of children with DCL (p < 0.001). Multivariate analysis showed that S. mutans and Bifidobacterium spp. were strongly associated with biofilm in children with DCL.

CONCLUSION

Differences were observed in the proportion of acidogenic and aciduric bacteria with dental caries progression. The data indicate that S. mutans and Bifidobacterium spp. in dental biofilm may be involved in some progression processes for ECC.

Functional profiles of coronal and dentin caries in children

Background: Dental caries results from a dysbiosis of tooth-associated biofilms and frequently extends through enamel into dentin which has a different structure and composition.

Objective: To evaluate the metatranscriptome of caries to determine the metabolic potential of caries communities compared with health.

Design: Samples from children, caries-free (CF: n = 4) or with coronal (CC: n = 5) or dentin (DC: n = 5) caries were examined for gene expression potential. Functional profiling was performed using HUMAnN2 (HMP Unified Metabolic Analysis Network).

Results: There was increased gene expression diversity in DC compared with CC and CF. Genes in CF included alcohol dehydrogenase from Neisseria sicca, methylenetetrahydrofolate reductase from Streptococcus sanguinis and choline kinase from streptococci. Genes in CC mapped mainly to Streptococcus mutans. Arginine deiminase in DC mapped to S. sanguinis and Actinomyces naeslundii. Glycerol kinase genes mapped to S. sanguinis in all groups whereas glycerol kinase in DC were from Rothia, Prevotella and streptococci. Uracil-DNA glycosylase in DC mapped to Prevotella denticola and Actinomyces. Repressor LexA in DC mapped to Scardovia wiggsiae, Dialister invisus and Veillonella parvula.

Conclusions: Functional profiling revealed enzyme activities in both caries and caries-free communities and clarified marked differences between coronal and dentin caries in bacterial composition and potential gene expression.