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 (<i>n</i> = 18); group CS, children who were diagnosed with severe early childhood caries (<i>n</i> = 17); and group BS, children with pigment (black extrinsic stain) without caries or restorations (<i>n</i> = 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 <i>Pseudopropionibacterium</i>, <i>Actinomyces</i>, <i>Rothia</i>, and <i>Cardiobacterium</i> was from high to low and that of <i>Porphyromonas</i> 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 <i>Selenomonas_3</i>, <i>Fusobacterium</i>, and <i>Leptotrichia</i> 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.