This study is designed to evaluate the impact of the regular consumption of probiotic Lactobacillus reuteri-containing lozenges over a period of 42 days on parameters of oral and general health in crew members of a naval ship at sea.

Probiotic strains of Lactobacillus reuteri have demonstrated a significant impact on the composition of the oral and intestinal microbiome as well as modulating the host response in several clinical trials and in vitro experiments.

This two-arm double blind placebo controlled clinical trial will evaluate the impact of the regular consumption of L.reuteri-containing lozenges over a period of 42 days on parameters of oral and general health in crew members of a naval ship at sea.

2 x 36 healthy study subjects will be recruited from the crew members of the ship.

At baseline and at the end of the study (day 42) the following parameters will be recorded at the Ramfjord teeth (teeth 16, 21, 24, 36, 41, 44):

Bleeding on Probing (BoP) as the primary outcome

Secondary outcomes will be Gingival Index (GI) Plaque Control Record (PCR) Pocket Probing Depth (PPD) Pooled oral and intestinal (stool) microbial samples will be taken at baseline and at the end of the study for the subsequent analysis of the

• composition of the oral microbiome
• composition of the intestinal microbiome by whole genome sequencing

Furthermore the frequency of short-term sick leave due to respiratory or intestinal diseases among the study participants during the observation period will be recorded.

Inclusion Criteria:

Minimum of 12 natural teeth

Exclusion Criteria:

Regular intake of antiinflammatory drugs affecting periodontal health (e.g. NSAIDs) Manifestation of systemic disease affecting periodontal health (e.g. diabetes) Use of antiseptic oral mouthrinses Drug/alcohol abuse