Probiotics are microorganisms, basically bacteria, that when ingested would confer health benefit beyond the basic nutrition. The microbes mostly involved are Lactobacillus acidophilus or cocci e.g. Streptococcus salivarius, S. Lactis, Entrococcus faecium, and yeast e.g. Saccharomyces cerevisiae, Aspergillus nigere and Candida pintolopesii. Ingestion of probiotics in any form, such as in food stuff (cheese, yogurt, fermented milk, fruit juice, or chewing gum) or contained in tablets and capsules, has been shown to reduce the incidence of dental caries, to manage priodontitis, halitosis and oral candidal infection. Probiotics act through competing with pathogenic microorganism for adhesion sites and nutrients on the host surface. They are also able to stimulate the immune system, secrete antimicrobial substances and alter the pH milieu of the host. However, more research is still needed in this field. According to the currently adopted definition by FAO/WHO, probiotics are “living microorganisms, principally bacteria that are safe for human consumption and, when ingested in sufficient quantities, have beneficial effects on human health, beyond the basic nutrition.1 The term “probiotic” is derived from the Latin preposition pro (“for”) and the Greek adjective (biotic), the latter deriving from the noun (bios, “life”).2 A human being is ingesting bacteria daily either non-intentionally as contaminants of e.g. vegetable, fruits and environment, or intentionally associated with processed food such as yogurt, fermented milk or cheese. Reviewing the literature revealed several reports for a beneficial effect of probiotics in treating systemic infection such as diarrhea,3 uro-genital infections4 and some systemic diseases such as liver disease,5 Crohn’s disease and cancer.6 The vast majority of probiotics are bacteria bacilli e.g. Lactobacillus acidophilus or cocci e.g. Streptococcus salivarius, S. lactis, Entrococcus faecium, and yeast e.g. Saccharomyces cerevisiae, Aspergillus nigere, Candida pintolopesii. Not any bacteria can act as probiotics. For a microorganism to be called probiotic has to be microbiologically characterized and subjected to randomized clinical trials. Principally it has to be of human origin, scientifically demonstrate beneficial physiological effects, to proof of being safe for human use, and stable in acid and bile. In addition, it has to be effectively able to adhere to the intestinal mucosa or the target tissue.7 Generally, there are multiple mechanisms explaining the effect of probiotics. By microbial adhesion to the target tissue, the probiotics compete with the pathogenic microbes on adhesion sites and nutrients. Once adhered, they secrete several antimicrobial substances such as bactreiocins, hydrogen peroxide and organic acids. The later can farther modify the pH and the oxidation-reduction potential in a way adversely affects the pathogenic microbes and facilitates their elimination. In addition, probiotics can stimulate the non-specific immunity and modulate the cellular and humeral immune response.6 In the oral cavity, probiotics are able to form a biofilm that lines and hence protects the oral mucosa or tooth surface from the invading bacteria. In addition probiotics compete with cariogenic bacteria, periodontopathogens, and bacteria associated with halitosis.