Periodontitis is a chronic inflammatory disease of the tooth supporting structures induced by a dysbiosis in the oral and subgingival microenvironment of susceptible patients. The long-term swallowing of high doses of periodontal pathogenic microorganisms could induce a dysbiosis of the intestinal microbiota, favouring the establishment of an 'inflamed' microbiome in terms of composition and/or function. The present project is aimed at a better understanding of the etiopathogenetic correlation between periodontitis and intestinal dysbiosis, and aims to explore the hypothesis that periodontal treatment may influence the multi-omics profile on the oral-gut-systemic axis. 70 patients affected by stage III-IV periodontitis will be recruited, and treated by means of full-mouth scaling and root planing. Salivary, subgingival plaque, plasma and stool samples, together with a complete periodontal charting and a food diary will be collected and compared at baseline and after treatment. Age, gender and BMI-matched healthy individuals will be recruited as controls.