Stimulated saliva volume accelerates dysbiosis of the salivary microbiome in children and young adults?

Management of salivary microbiota is essential in maintaining equilibrium. Background: The establishment of oral microflora reportedly occurs during infancy and childhood. However, the oral microbiota during this period of establishment remains to be fully investigated. This study aimed to compare the saliva test results and saliva flora between groups with high and low salivary bacterial counts. Materials and Methods: This cross-sectional study included 382 patients who visited the Department of Orthodontics at Hiroshima University Hospital. They underwent saliva examination. Subsequently, they were divided into two groups: high and low bacterial count groups. Among the clinical variables, factors affecting the salivary bacterial count were explored. A comprehensive analysis of the diversity and composition of the bacterial flora in the saliva of both groups was conducted via 16S rRNA sequencing using Illumina NovaSeq. Results: Multivariate analysis revealed that stimulated saliva volume and plaque control record were independent factors affecting increased salivary bacterial counts. Principal coordinate analysis and PERMANOVA supported the presence of distinct microorganisms between the groups. In the high bacterial count group, LEfSe analysis revealed that Prevotella, Veillonella, Megafaella, Selenomonas, and TM7X were the five most abundant bacteria. Significant differences were observed in the relative abundance of the 35 KEGG pathways. Furthermore, Prevotella and Veillonella were found to be strongly associated with 25 functional pathways. Conclusions: Management of salivary microbiota during the establishment of oral flora is essential in maintaining equilibrium in the upcoming oral microbial ecosystem.