 Material and methods: Fifty-four chronic periodontitis patients will be recruited and monitored clinically, immunologically and microbiologically at baseline, 3, 6, 9 and 12 months after therapy. All patients will receive scaling and root planning and randomly will be assigned over an probiotic experimental SRP probiotic, n18, antibiotic experimental SRP Azithromycin, n18 or control SRP placebo, n18 group. Probiotic will be used once per day during 3 months. Antibiotic will be used once per day during 5 days. 