Guest Editorial: Clarifications on the use of the new classification of periodontitis

Abstract
This editorial provides clarifications on the application of the Stage and Grade classification of periodontitis. In particular it describes: i) how to apply the extent criterion to the defined Stage of the disease; and ii) how to calculate tooth loss due to periodontitis in Stage III and IV cases presenting with evidently hopeless (irrational to treat) teeth with a clinical definition of such teeth.