An in situ study of the salivary microbiome derived from caries-free and caries-active individuals

This study aimed to compare the early response of salivary microbiome to sucrose challenge between caries-free and caries-active subjects. Eighteen systemic healthy volunteers aged 24 to 40 years, among which 8 were caries-free and 10 were caries-active, were recruited at Tianjin Stomatological Hospital. Saliva samples were collected at baseline, as well as 30 minutes and 2 hours post-administration of a 20% sucrose solution. The diversity and composition of the microbiota were investigated using 16S rRNA gene sequencing, and changes in salivary microbiome response to sucrose challenge were compared between caries-free and caries-active groups. The ASVs (Amplicon Sequence Variants) of salivary microbiome from caries-active individuals exhibited a higher rate of increase and a more intricate interaction network in response to sucrose challenge. After a 2-hour sucrose treatment, Actinomyces_graevenitzii exhibited a significant increase in saliva samples from either caries-free or caries-active donors compared to that before treatment. However, Schaalia_odontolytica exhibited a unique increase in caries-active saliva after 2 hours of sucrose treatment, while no such increase was observed in caries-free saliva. These results suggest that the salivary microbiome from caries-active individuals is more susceptible to sucrose challenge and more prone to a cariogenic microbiota. These findings provide innovative ecological insights into the etiology of dental caries.