Periodontitis is one of the most common chronic inflammatory disease with the etiology of bacterial plaque and is associated with a number of putative bacterial species. The periodontal destruction is substantially mediated by the host, driven by the bacterial challenge. The presence of pathogenic bacteria with the absence of so-called "beneficial bacteria" and the susceptibility of the host are the main aetiological factors of periodontal diseases.

Inclusion Criteria:

• Patients free from any systemic illness
• Previously untreated moderate to severe generalised chronic periodontitis.
• Patients free from adverse reactions to lactose or fermented milk products
• Patient unwilling to quit smoking and smokers over the past one year ( Smoker arm).

Exclusion Criteria:

• Previous history of antibiotic usage over past 6 months
• Patients who are eligible for antibiotic usage during the treatment course
• Patients who are pregnant, lactating, alcoholic or who had undergone any surgical or nonsurgical therapy within 6 months.
• Acute oral lesions or necrotising ulcerative periodontitis