The aim of this study is to evaluate the effects of probiotic administration of L. paracasei 28.4 as an adjunct to the non-surgical periodontal treatment in patients with periodontitis.

This is a superiority placebo-controlled randomized clinical trial. The population that will be evaluated in the study will be selected at Institute of Science and Technology (ICT), São José dos Campos, College of Dentistry.

Sixty patients presenting Stage III/IV and Grade B/C periodontitis will be divided into 2 groups:

• FMUD+Placebo (n=30): full-mouth ultrasonic periodontal debridement associated with administration of placebo formulation, twice a day for 30 days;
• FMUD+Probiotic (n=30): full-mouth ultrasonic periodontal debridement associated with administration of probiotic formulation twice a day for 30 days.

The study will consist of two stages of treatment:

• Initial therapy: Before starting treatment, a complete examination of the oral cavity and evaluation of periodontal parameters will be performed. All patients will undergo a prior adjustment of the oral environment and oral hygiene. Thirty days after completion of initial therapy, a new periodontal evaluation will be performed and only patients who present a visible plaque index less than or equal to 25% will undergo subgingival periodontal debridement.
• Non-surgical periodontal therapy: After initial therapy, all patients will receive full-mouth ultrasonic periodontal debridement. Debridement will be performed by a single operator, trained, blind to the allocation of patients and different from the evaluator. If there is any complication that prevents the completion of full-mouth debridement, the procedure will be finished within a maximum period of 24 hours. The randomization envelope will be opened and the probiotic/placebo formulation will be delivered to patients. They will be instructed to consume the samples twice a day during the 30 days following periodontal treatment.

All clinical measurements will be performed by a single researcher, previously calibrated for the measurements. After periodontal therapy, treatment results will be evaluated three and six months after periodontal debridement associated with the use of placebo/probiotic formulation. Indications of adverse oral effects will be verified by visual assessment at 7, 30 and 90 days after the start of consumption of formulations.

To assess patient-centered parameters, the OHIP-14 questionnaire will be applied before and after 6 months of periodontal treatment for each patient. A 30-days diary will be used to assess the adherence to use and occurrence adverse effects.

Microbiological and immunological analyzes will be carried out through subgingival biofilm and gingival crevicular fluid samples collected from sites with moderate pockets and sites with deep pockets at baseline, 3 and 6 months after therapy.

Inclusion Criteria:

• Diagnosis of stage III/IV and grade B/C generalized periodontitis;
• Presence of at least 20 teeth in the mouth;
• Signing the informed consent form.

Exclusion Criteria:

• Presence of systemic conditions that contraindicate the periodontal procedure or influence the progression of the disease;
• Periodontal treatment history in the last six months;
• Use of antibiotics or probiotics in the last six months;
• Smoke more than 10 cigarettes a day;
• Pregnant or breastfeeding;
• Chronic use of anti-inflammatory drugs or medications that can alter the response of periodontal tissues;
• Need of antibiotic prophylaxis for dental procedures;
• Need of probiotic therapy.

Data will be available at the end of the study after a direct request.

After the study completion.