Purpose: The aim of this study is to evaluate the effect of consumption of probiotic yogurt on the children’s salivary cariogenic microflora.

  Materials and Method: A double-blind randomized study was performed recruiting 2 parallel groups 24 healthy children in the case and 25 children in the control group. All healthy children were followed- up over 4 periods. Periods 1 and 3 were wash-out periods with duration of 1 and 2 weeks, respectively. During periods 2 and 4 (2weeks duration each), the case group consumed 200g yogurt containing Bifidobacterium lactis (1×106 per gram) once daily and the control group consumed normal yogurt. Salivary Streptococci mutans and Lactobacilli were enumerated before and after the yogurt consumption periods. Pre- and post-treatment values within and between regimens were compared using the t-test and paired samples. 

  Results: There was a reduction in Streptococcus mutans and Lactobacillus counts in the control group, but for Streptococcus mutans, the count reduction between phases 1 and 4 was statistically significant (p= 0.009). In the case group, neither the Streptococcus mutans count nor the Lactobacilli count was significantly reduced. 

  Conclusion: Based on the findings of this study, short-term daily consumption of probiotic yogurt containing Bifidobacterium lactis could not reduce the levels of salivary Streptococcus mutans and Lactobacilli in 6 to 12 year-old children, while normal yogurt could reduce the Streptococcus mutans counts significantly.