In February 2013, 44 healthy adults was recruited and randomized to daily intake of lozenges with or without Lactobacillus reuteri strains DSM 17938 and PTA 5289 for 12 weeks. The effect of these Lactobacillus reuteri strains on the oral microbial composition was monitored before, after 4, 8 and 12 weeks and after 1 and 6 months after exposure was completed. For this purpose saliva and tooth plaque was collected. Of 44 included subjects, 41 completed the study. The used Lactobacillus reuteri containing lozenges are commercially available and identical placebo lozenges was obtained from the manufacturer. The study product was well tolerated with no observed side effects. Compliance was excellent.