Subjects in group A received chlorhexidine for 2 weeks, subjects of group B received probiotic yogurt containing Lactobacillus rhamnosus GG (LGG) at a concentration of 2 × 10(8) colony-forming units per gram for 3 weeks, and subjects in group C received chlorhexidine in the same manner as group A and 24 h after cessation, they received probiotic yogurt in the same manner as group B. Salivary Streptococcus mutans (SM) and LGG were counted at baseline, 24 h, 1 week and 5 weeks after each intervention in all groups.
The SM count was reduced 24 h after cessation of chlorhexidine in group A (p < 0.001), and was steady for 5 weeks (p < 0.05). In group B, SM counts did not show significant differences 5 weeks after ending the intake of the probiotic (p > 0.05); LGG counts increased (p < 0.001), but were not steady over 5 weeks.
In group C, a significant reduction in SM count was recorded, and the reduced count was steady for 5 weeks; a significant increase in LGG counts was registered (p < 0.001), which was steady for 5 weeks.
Intergroup comparison showed a significant increase in LGG counts in groups B and C; however, this increase was not steady in group B. Chlorhexidine treatment before probiotic intake induced more stable colonization with LGG strains than probiotic alone.