Graetz C, et al. - In this investigation involving 251 patients, researchers sought to evaluate how the 2018 and 1999 classifications of periodontal diseases reflect patients’ features, disease severity/extent/progression and tooth loss (TL) during the observation period. For this investigation, study participants were followed over 21.8 ± 6.2 years. Most patients suffered from generalized severe chronic periodontitis or generalized aggressive periodontitis according to the 1999 classification. Younger and less often female or smokers were patients with aggressive periodontitis. Most patients were classified as generalized III-C, III-B or IV-C according to the 2018 classification. Patients’ age, smoking status, clinical attachment level, probing pocket depths and bone loss have been well reflected. Overall, the authors concluded that the features of patients, disease severity/extent/progression and TL were well reflected in the 2018 classification.