The buccal cavity is colonized by numerous microorganisms whose the number and composition could be modified with medical background (diseases and drugs) and the level of oral hygiene of the patients. Among all microorganisms identified in the periodontium, few of them are implicated in the etiopathogenesis of periodontal pathologies. To date, four major bacteria are identified for their ability to degrade periodontal tissues.

Although the periodontitis is established to be the consequence of bacterial virulence and immune dysfunction, these factors fail to explain the refractory periodontitis of some patients to etiologic treatment .

Others microorganisms such as protozoans could have an impact on this disease.

Inclusion Criteria:

• Adults > 18 years-old
• consulting in periodontal department of CHRU
• Patients with moderate to severe periodontitis
• At least 2 periodontal sites with PPD ≥ 5mm and one healthy site
• No scaling root planing in the last 6 months
• Patients insured under the Franch social security system

Exclusion Criteria:

• Pregnants patients
• Patients with antibiotic therapy and/ or all medecines which could modify the buccal microbiota in the last 6 months
• Tooth with endodontics periapical lesion
• Patients having a scaling root planing in the last 6 months
• Patients with guardianship

Patients consulting to periodontal department of CHRU (Nancy-Nice- Toulouse) presenting at least two PPD of 5mm and more, without any medecines which could modify microbiota were included in this study

non applicable