Periodontitis is a polymicrobial, inflammatory condition affecting tooth-supporting tissues. It is characterized by a progressive loss of epithelial attachment and resorption of alveolar bone, which can lead to tooth loss. Epithelial-mesenchymal transition (EMT) has been proposed as a reversible process that shifts the cell phenotype from epithelial to mesenchymal-like and may be involved in the process of periodontal inflammation either completely or partially. Long non-coding RNAs (lncRNAs) are a large class of regulatory transcripts longer than 200 nucleotides lacking evident protein-coding potential. Studies have shown that lncRNA dysregulation plays key roles in human diseases, including cancer, by modulating the epithelial-mesenchymal transition (EMT). The involvement of lncRNAs markers in the pathogenesis of periodontal disease induced EMT has not been studied thoroughly and have created a gap in the knowledge.

Inclusion Criteria:

• Patients with no history of systemic disease e.g., diabetes.
• Both males and females will be included in the study.
• Control group: patients fit the case definition of gingival health2, and confirmed by Histopathological inflammatory cell infiltration analysis.
• Periodontitis group: patients fit the case definition of periodontal disease referred for periodontal flap surgery (modified Widman's flap).
• Patients radiographically confirmed with infrabony pocket eligible for periodontal flap surgery.

Exclusion Criteria:

• Patients not willing to participate or consent.
• Patient taking medications that affect or modify immunity (e.g., corticosteroid), for the last 3 months.
• Patient taking NSAIDs for the last 3 months.
• Active smoker.

Patients diagnosed with periodontitis, and healthy periodontal tissues will be recruited at the College of Dentistry/University of Baghdad and Al Sadir specialized dental center/Al-Risafa directorate/ Ministry of Health. No age or gender restriction.