Effect of Long-Term Consumption of Lactobacillus paracasei SD1 on Reducing Mutans streptococci and Caries Risk: A Randomized Placebo-Controlled Trial

Randomized, double-blind, placebo-controlled trial in school-aged children in Thailand with generally good oral health. For the probiotic group, N=59 participants were randomized; children were followed for 12 months, with 6 months of treatment and 6 months of observation after stopping treatment.

The active regimen was 5 g of reconstituted milk powder containing Lactobacillus paracasei SD1, mixed with 50 mL water and taken orally once daily for 6 months. The probiotic content was reported as L. paracasei SD1 10^7 CFU/mg; the control product was the same milk powder without probiotic bacteria.

Daily probiotic milk produced a beneficial oral effect overall. Salivary mutans streptococci were significantly lower in the probiotic group than in controls at T3 and T6 (P < 0.001 and P = 0.001), and in the probiotic group MS decreased during dosing and for 3 months afterward (T3-T9) compared with baseline (P < 0.001). The probiotic strain was detected in 85%, 80%, 60%, and 0% of participants at T3, T6, T9, and T12, suggesting temporary colonization. Caries progression was also lower with probiotic use, with DT increment at T12 of 0.30 ± 0.57 versus 0.57 ± 0.95 in controls overall, and 0.26 ± 0.57 versus 0.91 ± 1.04 in the high caries risk subgroup; no adverse effects were reported.

The active arm was small, and the study was conducted in a specific population of Thai school-aged children with generally good baseline oral health, which limits generalizability. Benefits waned after treatment stopped, and some outcomes were subgroup-based, so the durability and broader clinical impact remain uncertain.