Substantial effort has been devoted in explaining and understanding the aetiology of the two major oral diseases, dental caries (DC) and periodontal diseases (PD). Both occur as the result of the metabolic activities of microorganisms within the oral biofilm, host factors and altered salivary ecosystem, that favour the emergence and persistence of a dysbiotic microbiota. Besides, both recognize dental hygiene as the main preventive measure. In DC, overexposure to dietary carbohydrates favour acidogenic and aciduric microorganisms and acidic metabolites. Prolonged and repeated state of acidification cause the progressive demineralization of tooth tissue. Periodontitis is a chronic inflammatory disease affecting tissues that surround and support the teeth; it's characterized by expansion of the microbial biofilm at the gingival margin, where keystones bacteria can orchestrate the inflammatory response. Without treatment, periodontal tissue destruction, bone resorption and tooth loss may ensue. Many metabolites associated with inflammation, oxidative stress, tissue degradation, and bacterial metabolism were found to be significantly elevated in both these diseases. Recently, a common development mechanism has been hypothesized. However, to date there is contradictory evidence about the association between DC and PD. The aim of our research, integrating metagenomics and metabolomics analysis, is to investigate the microbial and metabolites profiles in salivary samples in the co-occurrence of both diseases. For this purpose, salivary samples from 120 subjects grouped into 4 categories (30 with DC; 30 with PD, 30 with both diseases, and 30 healthy controls) will be collected. Results obtained by metagenomic and metabolomics procedures and clinical data, will be integrated by proper bioinformatic analysis, could possibly highlight innovative ecological common feature linking DC and PD, as significant prognostic factors in terms of primary and secondary prevention.
