Effect of probiotic interventions on oral health in children: a systematic review

Early childhood caries (ECC) is one of the most prevalent chronic diseases affecting young children worldwide. Probiotic supplementation has emerged as a potential adjunctive strategy for modifying the oral microbiome and reducing caries risk; however, evidence regarding its effectiveness remains inconsistent. This review evaluated the effects of probiotic interventions on oral health outcomes in children under 6 years of age, with emphasis on probiotic-based interventions and their influence on caries incidence, microbial changes, and biological mechanisms.

A systematic search of PubMed, Scopus, and Web of Science was conducted in accordance with the PRISMA 2020 guidelines up to June 2026. Eligible studies included randomized controlled trials, non-randomized intervention studies, and in vitro mechanistic studies evaluating probiotic interventions in children aged 0-6 years. Two independent reviewers performed study selection, data extraction, and quality assessment using the Cochrane RoB 2.0, ROBINS-I, and QUIN tools. Due to substantial clinical and methodological heterogeneity, findings were synthesized narratively, with supplementary quantitative analyses performed where appropriate. Certainty of evidence was assessed using the GRADE framework.

Twenty-one studies met the inclusion criteria, comprising 13 randomized controlled trials, three non-randomized intervention studies, and five in vitro studies. The clinical evidence primarily evaluated probiotic supplementation, most commonly Lactobacillus paracasei SD1, Lactobacillus rhamnosus strains, and Limosilactobacillus reuteri. Most randomized trials reported reductions in caries incidence or progression and decreases in salivary Streptococcus mutans counts, although findings were heterogeneous across probiotic strains and outcome measures. Mechanistic studies consistently demonstrated antimicrobial and antibiofilm activity of probiotic lactobacilli against cariogenic microorganisms, providing biological plausibility for the observed clinical effects. GRADE assessment indicated moderate-certainty evidence for randomized controlled trials, while evidence from non-randomized and in vitro studies was rated as low and very low certainty, respectively.

Probiotic supplementation appears to be a promising adjunct to conventional preventive strategies for improving oral microbial profiles and reducing caries progression in preschool children. However, the observed benefits appear to be strain-specific, and considerable heterogeneity across interventions and outcome measures limits definitive clinical recommendations. Further high-quality, adequately powered randomized controlled trials with standardized probiotic regimens, uniform caries assessment.

https://www.crd.york.ac.uk/PROSPERO/view/CRD420251229276, PROSPERO CRD420251229276.