Inclusion Criteria:  self-reported good general health, ≥ 14 erupted teeth excluding third molars. For periodontally healthy: Bleeding on probing score ≤10%, without attachment loss and radiographic bone loss and probing depth ≤ 3 mm in every site (Trombelli L et al., 2018). For periodontitis patients: periodontitis in stages II-IV.  Exclusion Criteria:  history of periodontal treatment in previous six months, acute oral infection, presence of systemic disease(s), pregnancy, lactation, smoking ≥ 10 cigarettes per day