The development of resistance to a range of antibiotics by some important pathogens has raised the possibility of a return of humans to the pre-biotic dark ages. The time has come to shift the paradigm of treatment from specific bacteria elimination to altering the bacterial ecology by probiotics. In order to better understand the pathogenesis of various oral diseases, it is necessary to understand the role of the ecology and microbiology of the oral cavity. Thus, the concept of bacteriotherapy has been an emerging field in dentistry. Probiotics are dietary supplements containing potentially beneficial bacteria or yeasts and has been found beneficial to the host health. They help in stimulating health promoting flora and also suppressing pathogens which cause and spread diseases. In the medical field, probiotics are used mainly in support therapy for gastrointestinal diseases. Recently, probiotics are being used as a treatment for various oral diseases. The aim of this review is to examine potential mechanisms of probiotic bacteria in the oral cavity and summarize observed effects of probiotics with respect to oral health. The review focuses on probiotic lactobacilli and bifidobacteria genera that are most utilized in various probiotic products.