Probiotics and oral health bacilli have also been measured. With three prod- recently, too. The probiotic strains used in these ucts, an increase in the number of salivary Lacto- studies include L. reuteri strains, L. brevis (CD2), L. bacillus has been observed.33,41 Unfortunately, with casei Shirota, L. salivarius WB21, and Bacillus subti- respect to dental caries, the study groups have lis. L. reuteri and L. brevis have improved gingival mainly been relatively small, and the studies fairly health, as measured by decreased gum bleed- short. Furthermore, it is important to realize that ing.44-46 The use of probiotic chewing gum con- the salivary level of caries-associated microbes taining L. reuteri ATCC 55730 and ATCC PTA 5289 does not equate to dental caries. In fact, the mi- also decreased levels of pro-inflammatory cyto- crobiota of unstimulated whole saliva resembles kines in GCF,46 and the use of L. brevis decreased that of the tongue more than of dental plaque.42 MMP (collagenase) activity and other inflamma- Thus, no conclusive statement about the effects of tory markers in saliva.45 With L. casei Shirota and probiotic bacteria on dental caries can be made. Bacillus subtilis no difference in test and control groups in gingival bleeding or measured plaque Periodontal diseases index was observed, but the use of L. casei Shirota The first studies of the use of probiotics for decreased PMN elastase and MMP-3 activities in enhancing oral health were for the treatment of GCF, and gingival inflammation was lower in the periodontal inflammation.43 Patients with various group consuming the probiotic product, as mea- periodontal diseases, gingivitis, periodontitis, and sured by MPO activity after a four-day period of pregnancy gingivitis, were locally treated with a experimental gingivitis.47 B. subtilis seemed to re- culture supernatant of a L. acidophilus strain. Sig- duce the number of periodontal pathogens.48 Use nificant recovery was reported for almost every of tablets containing L. salivarius WB21 has been patient. There has been significant interest in us- shown to decrease gingival pocket depth, partic- ing probiotics in treatment of periodontal disease ularly in high-risk groups such as smokers, and Figure 1. Potential mechanisms by which probiotic bacteria could affect oral health (Modified from76, with additional references.27,28,45,46,65,74,77-79). 350 European Journal of Dentistry