Effects of Short-term Consumption of Probiotic Yogurt on Streptococcus Mutans and lactobacilli Levels in 18-30 Years Old Students with Initial Stages of Dental Caries in Ahvaz City

Background and Objectives: Dental caries, caused by oral microbial flora, is considered as one of the most common infectious diseases in human. The aim of this study was to determine the effect of short-term consumption of probiotic yogurt containing bifidobacterium lactis on salivary streptococcus mutans and lactobacilli in students with initial stages of dental caries. Materials and Methods: 66 students (18-30 years old) with initial stages of dental caries were selected in this single blind randomized clinical trial. The subjects were randomly assigned into two groups: intervention group received 300g/d probiotic yogurt, and control group received 300 g/d conventional yogurt for 2 weeks. Un-stimulated fasting saliva sample was collected pre- and post-intervention. Bacterial counting was performed for salivary streptococcus mutans and lactobacilli. Salivarius Mitis agar and Rogosa agar were used as culture media for streptococcus mutans and lactobacilli, respectively. Results: The number of streptococcus mutans in saliva was significantly reduced in the intervention group post-intervention (P>0.001) however, it was not changed in the control group (P=0.71). Streptococcus mutans was also significantly lower in the intervention group compared with the control group post-intervention (P>0.001). Although salivary lactobacilli was reduced significantly in both groups post-intervention (P>0.001), this reduction was not significantly greater in the intervention group compared with the control group (P=0.594). Conclusions: It is suggested that consumption of probiotic yogurt may be useful to prevent the progression of dental caries. Keywords: Probiotic yogurt, Streptococcus mutans, Lactobacilli, Bifidobacterium lactis, Tooth decay