**6. Conclusion**

284 Contemporary Approach to Dental Caries

Other studies have focused on the production and gene regulation of virulence factors, such as gtfs, which play an important role in biofilm formation by *S. mutans*, for controlling dental caries (Tamwsada and Kawabata 2004; Huang et al. 2008). The ability of *S. mutans* to produce extracellular polysaccharides from dietary carbohydrates has been demonstrated to significantly enhance its cariogenicity. Thus, the less extracellular polysaccharide produced, the lower the cariogenicity of *S. mutans*. Also it is demonstrated that chemical surfactants exerted different effects on the synthesis of glucosyltransferases in *S. mutans*; Tween 80 sig nificantly increased the level of gtfs, while Triton X-100 decreased gtf levels. So, It is proposed that the secondary metabolite of the probiotic bacteria (*L.fermentum and L.acidophilus*) decreases the expression level of gtf genes and therefore may be useful for the

Although probiotics can affect most important caries pathogens, lactobacilli may correlate with caries development. Some strains of *Lactobacillus* spp., together with *S. mutans*, play a key role in development of dental caries. The production of organic acids from dietary carbohydrates is also a main factor in dental caries progression. If lactobacilli taken orally are able to adhere or temporarily establish themselves in the oral environment, their metabolism and acid production should not support caries induction. Studies addressing

pH drop and the decrease was the fastest with glucose for all tested strains, thus highlighting the acidogenic potential of probiotics. The diversity of *in vitro* results does not allow clear conclusions about which probiotics may add benefit to the oral cavity. More large scale, multicenter clinical investigations are required to support the true effectiveness

It has been also observed that caries free subjects are colonized by lactobacilli that possess a significantly increased potential to suppress the growth of mutans streptococci compared with caries active or arrested subjects (Stamatova & Meurman, 2009*)*. Finally, it can be concluded that the lactobacilli effect on caries prevention seems favorable when probiotic

Furthure more, it should be mentioned that, orally lactobacillus species are well tolerated by about every one. Flatulence or gas is the most common side effect of Lactobacilli supplementation. It is usually very mild and goes away after 2 or 4 days. Immunocompromised people should be careful with the probiotics use as there have been

Bifidobacteria, is not associated with any side effects. It can occasionally cause mild diarrhea

According to the researches, probiotic bacteria have been characterized for different oral

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

control of *S. mutans* and possibly other species.

sugar fermentation has shown a strain dependent

of probiotics in the prevention of oral and dental diseases.

reports of entering the blood stream (sepsis) in these individuals.

health purposes, including caries, periodontal diseases, and halitosis.

**4.6 Safty aspects of probiotics** 

strains are well selected.

**5. Future directions** 

in children.

Adhesion reduction can be an effective way on decreasing cariogenic potential of oral streptococci and all of the evidence has shown that probiotic bacteria such as Lactobacillus spp. can affect the oral ecology. In general, the above promising results suggest a potentially beneficial application of probiotics for the prevention of dental caries. These data also suggest that biosurfactant treatment can provide an option for controlling biofilm development and also influence the adhesive ability of bacterial pathogens
