Purpose: To investigate the oral colonisation potential after four weeks' administration of Lactobacillus reuteri and to examine the short-term effect of probiotics on salivary Streptococcus mutans and lactobacilli.
Materials and Methods: The study group comprised 13 young adults who volunteered after receiving verbal and written information. The short-term prospective clinical trial lasted 9 weeks, consisting of a 4-week intervention period with administration twice daily and a 5-week post-administration follow-up period with no probiotic consumption. Saliva and dental biofilm samples were obtained immediately before probiotic administration, after 2 weeks and after 4 weeks of L. reuteri administration. Follow-up samples were collected once every week on a regular basis after administration was terminated. The numbers of salivary S. mutans and lactobacilli were assessed by regular plating, while the presence of the two L. reuteri strains in saliva and dental biofilm was evaluated using quantitative polymerase chain reaction (qPCR).
Results: The occurrence of L. reuteri in the oral cavity increased gradually during the intervention period and reached the maximum level after four weeks of probiotic administration (p < 0.0001). The 4-week samples of stimulated whole saliva showed a statistically significant decrease in the number of S. mutans and a statistically significant increase in the salivary lactobacilli level in comparison to baseline. qPCR showed that the DSM 17938 strain has better colonisation for both saliva and dental biofilm than the ATCC PTA 5289 strain at the nine-week follow-up.
Conclusion: Probiotics have the ability to colonise the oral cavity during usage, but it gradually disappears after the completion of intake. It also has ability to decrease the number of salivary S. mutans.