The use of probiotics has taken giant leaps since the 20th century. Probiotics have been used in modifying the microbial flora of the stomach and intestines. Probiotics can create a biofilm, acting as a protective lining for oral tissues against oral diseases by keeping the bacterial pathogens off oral tissues by filling the spaces where the pathogens would invade. Some probiotic species also secrete antimicrobial compounds called bacteriocins: eg, reuterin. The efficiency of probiotics can be improved by the use of prebiotics. The probiotic organisms, lactobacillus, streptococci, and bifidobacterium species, are genetically designed to have greater adhesion and hence competitively inhibit S mutans