Influence of Probiotic Delivery Vehicles on Streptococcus mutans Levels in Children and Adolescents: A Systematic Review and Meta-Analysis

Background/Objectives: Oral probiotics may help prevent dental caries, but whether the delivery vehicle influences their effect remains unclear. This review compared oral probiotics with non-probiotic controls on Streptococcus mutans levels in children and adolescents according to the delivery vehicle. Methods: PubMed, Embase, Scopus, Web of Science, Cochrane Library and LILACS were searched to 1 April 2026 (PROSPERO CRD420261337128). Randomized trials in participants aged 0–19 years receiving probiotics for ≥14 days were included. RoB 2, GRADE and random-effects meta-analyses of standardized mean differences (Hedges’ g) by delivery vehicle were used. Results: Twenty-eight reports of 27 trials were included; nine trials contributed ten comparisons (1256 participants) to the meta-analysis. The exploratory overall estimate favored probiotics (g = −1.19; 95% CI: −1.99 to −0.39; I2 = 93.9%). The estimates for lozenges/tablets (g = −2.02; 95% CI: −6.73 to 2.69), non-fermented dairy products (g = −0.90; 95% CI: −2.02 to 0.22) and fermented dairy products (g = −1.14; 95% CI: −4.62 to 2.35) were not significant, and the subgroups did not differ (p = 0.59). Certainty was very low. Conclusions: Current evidence is insufficient to determine whether the delivery vehicle modifies the effect of probiotics on S. mutans. Head-to-head trials using the same strain, dose and outcomes are needed.