Probiotics and postbiotics in caries and periodontal prevention: mechanisms, clinical evidence, and trajectory of the field

Dental caries and periodontal disease remain among the most prevalent non-communicable conditions, and their redefinition as biofilm dysbiosis opened the door to probiotics and, more recently, postbiotics as preventive agents. This narrative review reconstructs the trajectory of mechanistic and clinical evidence on both classes between 2019 and 2026. OpenAlex, PubMed and Crossref were searched for studies on probiotics and postbiotics in caries and periodontal prevention, and the synthesis was organized chronologically in three periods: consolidation (2019-2021), refinement and emergence of postbiotics (2022-2024), and the current inflection toward standardization (2025-2026). Mechanistically, probiotics act through competitive exclusion, secreted antimicrobials, inhibition of glucan synthesis and immunomodulation, and postbiotics retain these activities in inactivated or cell-free form. Clinical evidence evolved from small trials of live strains that reduced Streptococcus mutans toward lesion-level outcomes; a 2026 trial reported progression to cavitated lesions in 26.8% of children receiving Lactobacillus rhamnosus SP1 versus 46.3% of controls. In periodontitis, meta-analyses consistently show improvements in probing depth and bleeding that are statistically significant but modest, and postbiotic candidates show bone-protective effects in preclinical models. The field has shifted from proving that live probiotics work to standardizing strain, dose and vehicle, and postbiotics now represent the most active frontier because of their safety and stability.