Fig. 2. The mechanism of probiotics to prevent dental caries.

It is roughly divided into five parts. A Production of active metabolites: probiotics directly inhibit cariogenic pathogens by active metabolites (e.g., bacteriocin, enzyme, biosurfactants, organic acids, and hydrogen peroxide), which themselves have bacteriostatic activity. B Inhibition of cariogenic microbial biofilm: probiotics can inhibit or remove the biofilm of oral cariogenic microorganisms. C Competitive adhesion and colonization: probiotics not only occupy the colonized sites in the oral cavity but also inhibit the adhesion ability of cariogenic microorganisms. D Coaggregation with pathogens: probiotics inhibit cariogenic microorganisms colonization in the oral cavity through co-aggregation. E Regulation of the immune system: probiotics activate or modulate the host immune system, thereby enhancing the immune response to cariogenic microorganisms (enhances salivary levels of human neutrophil peptides 1–3).