Reduction of Streptococcus mutans by probiotic milk: a multicenter randomized controlled trial.

OBJECTIVE: To investigate the effects of probiotics, Lactobacillus paracasei SD1, on the quantities of Streptococcus mutans in saliva and plaque samples of preschool children. DESIGN: This randomized trial recruited 487 preschool children from eight childcare centers. Participants were assigned to receive a 6-month course of placebo milk daily (group I), probiotic milk either daily (group II) or three days a week (triweekly, group III). The absolute quantities of S. mutans and total lactobacilli in the saliva and plaque samples at baseline (T0), after intervention (T6), and 6 months after discontinuation (T12) were assessed by qPCR. RESULTS: Of 487 children, 354 completed all follow-up periods. However, only 268 children (3.2 +/- 0.8 years old; groups I = 86, II = 89, and III = 93) provided adequate saliva for qPCR. Whereas the quantities of S. mutans were significantly decreased in groups II and III compared to group I in the saliva and plaque samples at T6 and T12, those of total lactobacilli were significantly increased (p < 0.0167). There was no difference in the quantities of S. mutans or total lactobacilli between groups II and III at any period. Significant changes in the quantities of S. mutans and total lactobacilli lasted until T12 compared to T0 (p < 0.0167). CONCLUSIONS: Probiotic administration daily or triweekly reduces S. mutans quantities, whereas it increases total lactobacilli quantities that persists at least 6 months after discontinuation in the saliva and plaque samples of preschool children. CLINICAL RELEVANCE: Daily or triweekly consumption of L. paracasei SD1 supplemented in milk may help prevent dental caries in preschool children.