Metagenomic investigation of bacteria associated with dental lesions: a cross-sectional study

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.

Construction of a caries diagnosis model based on microbiome novelty score

OBJECTIVES

This study aimed to analyze the bacteria in dental caries and establish an optimized dental-ca-ries diagnosis model based on 16S ribosomal RNA (rRNA) data of oral flora.

METHODS

We searched the public databa-ses of microbiomes including NCBI, MG-RAST, EMBL-EBI, and QIITA and collected data involved in the relevant research on human oral microbiomes worldwide. The samples in the caries dataset (1 703) were compared with healthy ones (20 540) by using the microbial search engine (MSE) to obtain the microbiome novelty score (MNS) and construct a caries diagnosis model based on this index. Nonparametric multivariate ANOVA was used to analyze and compare the impact of different host factors on the oral flora MNS, and the model was optimized by controlling related factors. Finally, the effect of the model was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

1) The oral microbiota distribution obviously differed among people with various oral-health statuses, and the species richness and species diversity index decreased. 2) ROC curve was used to evaluate the caries data set, and the area under ROC curve was AUC=0.67. 3) Among the five hosts' factors including caries status, country, age, decayed missing filled tooth (DMFT) indices, and sampling site displayed the strongest effect on MNS of samples (P=0.001). 4) The AUC of the model was 0.87, 0.74, 0.74, and 0.75 in high caries, medium caries, low caries samples in Chinese children, and mixed dental plaque samples after controlling host factors, respectively.

CONCLUSIONS

The model based on the analysis of 16S rRNA data of oral flora had good diagnostic efficiency.

Comparative Microbial Profiles of Caries and Black Extrinsic Tooth Stain in Primary Dentition

Extrinsic black tooth stain (BS) is a common oral disease associated with lower caries experience in preschool children, although the microbiotic features contributing to the low risk of caries in this group remain elusive. In this study, we aimed at identifying the dominant bacteria in dental plaque to indicate the incidence of caries in the primary dentition. Subjects were divided into 3 groups based on the clinical examination: group CF, children without pigment who had no caries lesions or restorations (n = 18); group CS, children who were diagnosed with severe early childhood caries (n = 17); and group BS, children with pigment (black extrinsic stain) without caries or restorations (n = 15). The total microbial genomic DNA was extracted and subjected to bacterial 16S ribosomal RNA gene sequencing using an Illumina HiSeq platform. The differential dominant bacteria were determined using Wilcoxon rank-sum testing and linear discriminant analysis effect size (LEfSe). Co-occurrence network analysis was performed using sparse correlations for compositional data, calculation and functional features were predicted using PICRUSt. Interestingly, our results showed that the relative abundance of Pseudopropionibacterium, Actinomyces, Rothia, and Cardiobacterium was from high to low and that of Porphyromonas was low to high in the BS, CF, and CS groups, consistent with the clinical incidence of caries in the 3 groups. Moreover, an increased level of Selenomonas_3, Fusobacterium, and Leptotrichia was associated with high caries prevalence. We found that the interactions among genera in the BS and CS plaque communities are less complex than those in the CF communities at the taxon level. Functional features, including cofactor and vitamin metabolism, glycan biosynthesis and metabolism, and translation, significantly increased in caries plaque samples. These bacterial competition- and commensalism-induced changes in microbiota would result in a change of their symbiotic function, finally affecting the balance of oral microflora.