Pilot study with healthy subjects to test the in vivo potential colonization ability of S. dentisani. Phase I, exploratory, prospective, mechanistic pilot clinical trial with two parallel follow-up groups. Probiotic will be applied topically as an adhesive gel with a dental splint under different dosing regimes. Saliva and plaque samples will be obtained at day 0, 14 and 28.

Phase I study, exploratory, prospective, mechanistic, to evaluate the capacity of

Streptococcus dentisani CECT 7746 of colonizing the tooth surface. The study will be carried out with 10 healthy subjects divided into two groups (n = 5 per group) that differ in the number of applications of probiotic:

Group A: participants who will receive a single application of the product during the initial visit Group B: participants who will receive 7 applications on consecutive days, with the first in the start visit. Probiotic will be applied topically as an adhesive gel with a dental splint under different dosing regimes.The total dose received will be the same for both groups, and the total duration of the follow-up will be of 4 weeks from the first application also for both groups.

On day 0: Participants who meet the inclusion and exclusion criteria will be randomized in one of the two groups. Saliva and plaque samples will be obtained by the dentist, and all the participants will receive an professional teeth cleaning in one half of the mouth (quadrants 1-4). Afterwads, treatment will be applied by the dentist according to assigned group, and the randomized participants in the multiple-dose group will be explained how to perform the six successive applications at home every 24 hours.

On day 14: follow-up visit, saliva and plaque samples will be obtained from all participants. Patient assigned to the multi-dose group will return the used material On day 28th: final visit, saliva and plaque samples will be obtained.

Inclusion Criteria:

• Absence of serious periodontal diseases (eg gingivitis, periodontitis)
• Ability to understand the requirements and implications of the study

Exclusion Criteria:

• Antibiotic consumption during the 30 days prior to the initiation of the study.
• Oral probiotics consumption during the 30 days before the start of the study
• Pregnant or lactating women
• Chronic diseases (eg, diabetes, kidney problems, cancer) or diseases that could affect salivary flow.
• Chronic treatment or medication that could reduce salivary flow, such as antidepressants or psychotropic drugs.
• Allergy to any of the product composition ingredients