Following active periodontal treatment and the resolution of periodontal inflammation in periodontitis, the periodontal tissue is healthy but with a reduced connective tissue attachment and alveolar bone height. Plaque-induced gingivitis on a reduced periodontium is characterized by the return of bacteria -induced inflammation to the gingival margin on a reduced periodontium with no evidence of progressive attachment loss (ie. no indication of active disease). If a clinician is going to make the diagnosis of "gingivitis on a reduced but stable periodontium", it is necessary to longitudinally demonstrate that attachment loss is not occurring.