Evidence-based dentistry is a frequent theme of numerous scientific papers and metaanalyses currently constitute a gold-standard. Not all the arguments regarding the links between periodontics and orthodontics are based on scientific proof. However, there now exist strong professional consensuses. Fundamental data concerning the etiology of periodontal pathologies are used to define precise clinical definitions. The aim of this article is to enable orthodontists to incorporate the most recent periodontal data into their treatment protocols. By means of a simple and logical framework, the orthodontist will be able to detect the signs and symptoms of periodontitis at the first visit and determine the presence, or not, of periodontal risk factors.