Beneficial microorganisms, or probiotics, have various functions including antibacterial activities, modulation of the host immune response, antiallergic effects, and cancer prevention in the human intestine. A number of studies using lactic acid bacteria for the prevention of oral diseases have been reported. Probiotic bacteria in the human oral cavity include Bifidobacterium species and Lactobacillus species. Oral administration of Lactobacillus salivarius WB21-containing tablets and oil reduced plaque accumulation, periodontal pocket depth, bleeding on probing, and oral malodor.L. salivarius TI 2711 showed antibacterial activity against Porphyromonas gingivalis in mixed culture experiments, and a clinical trial indicated that the number of P. gingivalis in subgingival plaque was reduced by oral administration of L. salivarius TI 2711-containing tablets but recovered following cessation of tablet administration. However, there have been no reports regarding caries prevention and control by L. salivarius.
Lactobacillus species are microbial markers of dental caries risk. Some species of lactobacilli have been reported to occur in large numbers in both superficial and deep caries. However, several Lactobacillus species have been isolated from healthy mouths. Increased production of organic acids in the dental plaque would be considered a side effect of probiotic lactobacilli. Most studies of caries prevention and control by lactic acid bacteria were performed over the last few years. Lactobacillus species, including Lactobacillus rhamnosus, Lactobacillus reuteri, and Lactobacillus paracasei, that were investigated in previous clinical trials did not alter or reduce mutans streptococci levels. No adverse effects or potential risks of these bacteria were reported. In the present study, the potential effects of tablets containing L. salivarius WB21 or TI 2711 on caries risk factors were compared with tablets containing an antibody against Streptococcus mutans and those containing only xylitol as controls. In addition, oral administration of L. salivarius WB21-containing tablets for 2 weeks was performed to evaluate their effect on the levels of mutans streptococci.