Inclusion criteria:  Patient over 18 years old Patient treated for periodontitis between 01/01/2012 and 07/31/2021 Patient whose medical and periodontal file contains all the elements necessary for data analysis Subject not having expressed, after information, his opposition to the reuse of his medical data for the purposes of this research.  Exclusion criteria:  Patient who expressed his opposition to participating in the study Patient without periodontitis Patient smoking more than 10 cigarettes / day Patient presenting a dilapidated oral state (untreated caries, unrestored teeth), oral infectious foci whose management requires antibiotic treatment during the initial treatment Impossibility of giving the subject informed information Subject under safeguard of justice Subject under guardianship or guardianship