**5. Future directions**

According to the researches, probiotic bacteria have been characterized for different oral health purposes, including caries, periodontal diseases, and halitosis.

Genetically modified microbes including probiotics can take a new dimension to the concept of probiotics. Their main aim is the reduction of harmful effects of pathogenic strains naturally colonizing the oral cavity. The modified strain could then be used to replace the original pathogen. They also could be used to increase the properties of a potentially beneficial strain. In field of oral immunology, probiotics are being used as passive local immunization vehicles against dental caries. Bacteriophages, have also been detected in oral pathogens, such as *Actinobacillus Actinomycetemcomitans* (Sheikh et al., 2011).

 The selection of the best probiotic for oral health and investigation the effect of other probiotic's metabolites on virulence genes and other traits of *S. mutans* are also issues that calls for further studies. It is possible that the administration way of probiotics might positively affect the effects observed as related to mutans streptococci reduction. So, further studies regarding the selection of best way for probiotic administration are necessitated.

Furthermore, the dosage of probiotic administration in each indication should be defined. Probiotics should be administered carefully and cautiously, and only on the basis of strong scientific evidence. Such evidence should direct the cautious, deliberate addition of clinically proven probiotics to commonly consumed food products to allow consumers to conveniently benefit from these organisms. Finally, safety issues are very important with any kind of bacteriotherapy.

Consequently, future studies should be conducted to investigate if phage therapy might be applied for oral and dental diseases in the same way as has been attempted for systemic infections.
