The effects of probiotics intervention on oral health outcomes: a comprehensive umbrella review of meta-analyses

Background Probiotics are proposed adjuncts for oral health, but findings from meta-analyses are inconsistent. We conducted an umbrella review of meta-analyses to synthesize evidence on probiotics’ effects on cariogenic bacteria such as Streptococus (S.) mutans and Lactobacillus , halitosis (volatile sulfur compounds and organoleptic scores), and caries progression. Methods PubMed, Web of Science and Scopus databases were searched up to October 2025 for meta-analyses of clinical trials investigating the effect of probiotics on oral health outcomes. Two reviewers screened studies, extracted data on strains, doses, durations, and pooled effect estimates, and assessed review quality using AMSTAR-2. Directions and key pooled estimates reported in included meta-analyses were summarized. Results Eleven meta-analyses met inclusion criteria, encompassing participants from infancy to adulthood (reported mean/median ages 0.2–42.5 years), probiotic doses reported between ∼5 × 10 5 and 5 × 10 10 CFU, and intervention durations of 7 days to 24 months. Common strains included Lactobacillus , Bifidobacterium , and S. salivarius . Probiotics were associated with reductions in S. mutans counts in most reported comparisons and improved halitosis measures in the majority of comparisons. Pooled estimates for caries-related outcomes indicated modest reductions (example pooled SMDs reported∼−0.24; 95% CI −0.39 to −0.10 and for Lactobacillus rhamnosus −0.41; 95% CI −0.60 to −0.21). Most meta-analyses were rated moderate by AMSTAR-2; substantial heterogeneity, variable strains/delivery, and reliance on surrogate endpoints were common. Conclusions Evidence suggests modest benefits of certain probiotic strains on cariogenic bacteria and halitosis, but heterogeneity, surrogate outcomes, and moderate review quality limit certainty. High-quality, strain-specific RCTs with standardized clinical endpoints are needed.