Biofilm was composed of many bacteria. It exists on many parts in human body. If there were any imbalance in bacteria, biofilm stress will be induced. This stress will cause dental plaque formation, dental caries, and gingival infection. Controlling bacte-rial imbalance by probiotics maybe beneficial to the aim of caries control. There are many evidences in the literature that probiotics have the potential to reverse bacterial imbalance in biofilm. The effect of maternal ingestion of probiotics to prevent the verti-cal transmission of caries bacteria from mother to the child is still to be verified. Pre-vention of caries merely by bacterial therapy to lower biofilm stress is not practical.