Local and systemic effects of probiotic modulation of the oral microbiota

The oral cavity hosts a complex microbial ecosystem in which bacteria, fungi, viruses, and archaea interact with the host to maintain both local and systemic homeostasis. Increasing evidence indicates that disruption of this equilibrium can promote the overgrowth of opportunistic species such as Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus mutans, triggering chronic inflammatory processes with potential effects beyond the oral environment. This narrative review summarizes the mechanisms through which oral dysbiosis may influence immune, metabolic, and microbial pathways along the oral–gut and oral–lung axes, potentially contributing to systemic conditions including cardiovascular, respiratory, intestinal, and autoimmune disorders, cancer development, and preterm delivery. Within this framework, targeted modulation of the oral microbiota through probiotics, prebiotics, and postbiotics may represent a potential prophylactic strategy. Several strains (including Lactobacillus reuteri, Streptococcus salivarius K12/M18, Bifidobacterium animalis BB-12, and Lactobacillus rhamnosus GG) have been reported, based on current evidence, to exert beneficial effects by competing with pathogens, modulating inflammatory responses, and supporting mucosal barrier function, with possible downstream effects mediated through interactions with the intestinal microbiota. Prebiotics and postbiotics represent complementary approaches, promoting a more stable and less inflammatory oral microenvironment while offering advantages in terms of safety, stability, and applicability in oral care products. Despite these encouraging findings, the lack of long-term clinical studies with endpoints clearly demonstrating systemic benefits from probiotic interventions targeting oral health remains a limitation. Importantly, current evidence does not establish a consistent causal relationship between oral dysbiosis and the systemic diseases discussed in this review. Overall, these findings suggest that probiotic interventions may serve as a valuable adjunct to oral healthcare, with the potential, based on current evidence, to contribute to the prevention and management of systemic diseases through targeted modulation of the oral microbiome. Nevertheless, more comprehensive and rigorous research is required to confirm these potential effects.