The aim of this study is to evaluate the effect of the probiotic therapy as an adjunct to non-surgical periodontal treatment in patients diagnosed with Generalized Chronic Periodontitis. Clinical study's hypothesis is that with the use of probiotic therapy, the standard treatment could be enhance.

Before the study begins, the selected individuals will be identified by a numeric code and will receive instructions regarding oral hygiene as well as supragingival scaling in all teeth. According to a random numeric table generated by a computer software, the study coordinator will allocate each patient into one of the following groups: Control (Scaling and Root Planing - SRP) or Test (SRP + probiotic therapy). The subjects (Test and Control groups) will receive lozenge containing/not containing. In the Test group, the lozenge will present Bifidobacterium lactis HN019 (HN019). Individuals will be instructed (immediately after the first session of mechanical instrumentation) to consume twice a day for 4 weeks by dissolving the lozenge before bedtime, and when wake up. They will also be instructed not to consume other probiotic product during the study. Clinical, immunological and microbiological parameters will be assessed at baseline (pre-intervention) and after completion of non-surgical periodontal therapy 30 and 90 days. All patients will receive detailed information regarding the study (goals, benefits and risks) according to the Term of Consent. The sample size was determined using the software Graphpad Statemate 2.0 (GraphPad Software, Inc., San Diego, CA, USA). The ideal sample size to ensure an 80% power in the statistical analysis of the data obtained in this study was calculated considering the differences of means and standard deviations between the test and control groups of the study by Vivekananda et al. (2010). The α value was set at 0.05. The average dropout of patients in our previous studies (approximately 20%) was also considered to calculate the sample size. Thus, a sample size of at least 30 patients was considered appropriate for this study. The normality and homoscedasticity of the data obtained will be checked. Comparisons within groups and among groups at different time intervals will be performed through parametric or non-parametric appropriate tests. The significance level will be set at 5% in all tests. All calculations will be performed by SPSS software (SPSS, Chicago IL, USA).

Inclusion Criteria:

• More than 30 years old
• All patients must present good general health.
• Previously untreated periodontitis
• Minimum of 15 teeth

Exclusion Criteria:

• Having received antibiotics for any purpose within 6 months prior to entering the study or the need for antibiotic coverage for dental treatment
• Pregnancy and nursing
• Acute oral lesions or necrotizing ulcerative periodontitis,
• A history of diabetes, rheumatic fever, liver or kidney disease, neurological deficiencies, immunological diseases or use of medication which may affect periodontal tissue, (phenytoin, cyclosporin, nifidepine, chronic use of non-steroidal anti-inflammatory drugs)
• Current smoker or former smoker

Periodontal clinical examination (pre- and post-intervention) will be conducted by a single trained and calibrated examiner, who will be blinded to the experimental groups of the study. The examiner will also be blinded to the microbiological and immunological evaluations. SRP procedures will be performed by specialist in Periodontics, trained for these purposes, who will also be blinded to the experimental groups of the study.

The coded lozenge will be given to the examiner, who will distribute them to the patients and will not have any access to information regarding the content of the lozenge. In addition, the patients will be blinded to the content of the lozenge and the treatment assignment during the study. The meaning of each code number will be revealed by the study coordinator only after conducting the statistical analysis of the experimental data.