Dental caries are considered the most common infectious diseases that impacts human populations worldwide. The human oral cavity is colonized by a wide range of microorganisms including viruses, protozoa, fungi, archaea and bacteria. Oral diseases begin with the development of dental plaque, a biofilm formed by the accumulation of bacteria. Of these bacteria, Streptococcus mutans has been identified as the leading cause of dental caries. Probiotics are described as live microorganisms which provide beneficial impacts to their host by improving the intestinal microbial balance. Studies have demonstrated that probiotic therapies may be suitable for decreasing the cariogenic potential of S. mutans as well as other cariogenic bacteria. In this study, it was hypothesized that probiotics would exhibit a significant effect on the population density of S. mutans within the oral cavity. Nine people selected in this study consumed Activia probiotic yogurt for a seven-day trial period. DNA was extracted from these swabs and analyzed by qPCR. The results showed the amount of S. mutans increased insignificantly (P>0.05), whereas the proportion of S. mutans in the entire community was insignificant (P>0.05). Individual subjects responded differently to treatment, indicating the influence of their preferential diet on S. mutans abundance. Studies conducted on the probiotic strains within the Activia yogurt were previously shown to be insufficient in antagonizing cariogenic bacteria, which attributes to these results.