PURPOSE This review summarized the available literature on the prevention of childhood caries through biofilm engineering with probiotic bacteria in early childhood. METHODS Three databases (PubMed, Cochrane Library and Trip) were searched through January, 2016 for randomized controlled trials published in English. Out of 144 abstracts, seven studies fulfilled the predetermined inclusion criteria and were quality assessed with respect to risk of bias independently by two examiners. Due to the paucity and heterogeneity, a narrative synthesis was performed. The effect size was estimated from the caries prevalence and expressed as prevented fraction and number needed to treat. RESULTS Probiotic supplements were better than placebo in preventing early childhood caries in all seven studies although the difference was statistically significant in only four of them. The prevented fraction ranged from 11% to 61% with a median of 48%. However, the quality of the evidence was low or very low and further translational research is needed to investigate this preventive approach in the clinic.