Periodontitis is a widely prevalent disease worldwide that has serious public health consequences. Its prognosis includes tooth loss and edentulism, a condition that negatively affects chewing causing functional disability; and esthetics causing social impairment. Consequently, periodontitis may end up causing marked impairment of the quality of life of the affected patients, impairment of general health and increasing the dental care costs significantly.

Dysbiotic changes in the oral microbiome arise after some microbial species are enriched by primary products resulting from tissue breakdown due to gingivitis. It then triggers the host cells to produce proteinases that mediate loss of marginal periodontal ligaments, apical migration of the junctional epithelium and apical spread of bacterial biofilm.

However, the dysbiotic changes may be more likely to occur in some patients rather than others due to certain risk factors including smoking and immuneinflammatory responses. Thus, the severity of periodontal disease in these patients would be higher. Tobacco smoking is no longer considered to be a habit, but a dependence to nicotine and a chronic relapsing medical disorder. Among its detrimental effects on general health, tobacco smoking increases the risk of periodontitis by 2 to 5 folds. This takes place by increasing the dysbiotic changes in the oral microbiome and so, increasing the severity and extent of the periodontal disease at a younger age. Therefore, smoking has been considered as a modifying factor of periodontitis that should be considered upon periodontitis case grading definition.

Therefore, this research aims to identify the difference in dysbiosis between the three categories of periodontitis, trying to understand the cause of the resistance of each category to treatment compared to the milder category.

Inclusion Criteria:

• Patients 18 years or older.
• Patients with periodontitis.
• Probing pocket depth ≥ 4 mm.
• Teeth with CAL≥ 3 mm at ≥2 non-adjacent teeth.
• Clinical indication and/or patient request for treatment of the periodontal condition.

Exclusion Criteria:

• Patients with any systemic diseases.
• Pregnant females.
• Patients who took any antibiotic in the past month.
• Handicapped and mentally retarded patients.
• Patients undergoing radiotherapy.

adult patients clinically diagnosed to have chronic periodontitis