Background: The objective of this trial was to evaluate whether the regular consumption of probiotics may improve the known deterioration of periodontal health in navy sailors during deployments at sea.

Methods: 72 healthy sailors of a naval ship on a practicing mission at sea were recruited and randomly provided with a blinded supply of lozenges to be consumed twice daily for the following 42 days containing either the probiotic strains Lactobacillus reuteri (DSM 17938 and L. reuteri (ATTC PTA 5289) (test n = 36) or no probiotics (placebo n = 36). At baseline, at day 14 and day 42 bleeding on probing (primary outcome), gingival index, plaque control record, probing attachment level, and probing pocket depth were assessed at the Ramfjord teeth.

Results: At baseline there were no significant differences between the groups. At day 14 and day 42 test group scores of all assessed parameters were significantly improved (P < 0.001) compared to baseline and to the placebo group which by contrast showed a significant (P < 0.001) deterioration of all parameters at the end of the study.

Conclusions: The consumption of probiotic L. reuteri-lozenges is an efficacious measure to improve and maintain periodontal health in situations with waning efficacy of personal oral hygiene.