Currently, with the increase of bacterial resistance to antibiotics associated with its side effects, it is necessary to find other adjuncts to combat the disease that are an alternative to the use of antibiotics. The use of probiotics has been proposed in the literature as an adjunct therapy for the treatment of periodontal diseases, however, few controlled and randomized clinical studies have been performed. The objective of this double-blind randomized controlled trial will be to evaluate the response of clinical and microbiological periodontal parameters to the comparison of two different adjuvant therapies (antibiotic and probiotic) for the treatment of stages II and III grade B periodontitis.

Currently, with the increase of bacterial resistance to antibiotics associated with its side effects, it is necessary to find other adjuncts to combat the disease that are an alternative to the use of antibiotics. The use of probiotics has been proposed in the literature as an adjunct therapy for the treatment of periodontal diseases, however, few controlled and randomized clinical studies have been performed. The objective of this double-blind randomized controlled trial will be to evaluate the response of clinical and immunological periodontal parameters to the comparison of two different adjuvant therapies (antibiotic and probiotic) for the treatment of stages II and III grade B periodontitis. Patients will be randomized into 3 groups: Group 1 (n=15): periodontal debridement, Group 2 (n=15): periodontal debridement associated with antibiotic (Metronidazole 400 mg + Amoxicillin 500mg) and Group 3 (n=15): periodontal debridement associated with probiotic (Lactobacillus reuteri). Clinical (plaque index, gingival index, probing depth, gingival recession, relative clinical attachment level and periodontal inflamed surface area (PISA) index) and immunological data obtained before and after periodontal therapy (baseline, 30 and 90) will be consolidated and made available on average ± standard deviation and normality tested using the Shapiro-Wilk test. For statistical analysis, the software BioEstat 5.0 (Belém, PA, Brazil) will be used, with p-value < 0,05.

Inclusion Criteria:

• Individuals between 35 and 50 years of age;
• Be diagnosed with generalized chronic periodontitis: present a loss of interproximal clinical insertion> 3 mm in 2 nonadjacent teeth and loss of interproximal clinical insertion ≥5 mm, in 30% or more of the teeth present;
• Present at least 16 teeth;
• Present good systemic health;
• Agree to participate in the study and sign the informed consent form

Exclusion Criteria:

• Patients with systemic problems (cardiovascular changes, blood dyscrasias, immunodeficiency, among others), which do not indicate the periodontal procedure;
• Have undergone periodontal treatment in the last twelve months;
• Have used antibiotics and/or anti-inflammatories for the past six months;
• Smoking patients;
• Pregnancy or Lactation;
• Chronic use of medications that may alter the response of periodontal tissues.

In addition to concealment of randomization, the investigator responsible for the procedures of periodontal therapy (periodontal debridement) and the researcher responsible for the measurements will not know which treatment each group will receive, characterizing the blindness of the study.