IL17A and periodontal disorder: The aims of this study were (i) to assess whether the salivary IL-1β, IL-17A, RANK-L and OPG levels, jointly, have the potential to discriminate between the mild and severe periodontitis site conditions according to the current classification criteria of periodontal diseases; and (ii) to enable diagnostic/prognostic actions to differentiate between the incipient and more advanced levels of the disease.