Comparison of periodontitis patients' classification in the 2018 versus 1999 classification

Objectives We aimed to assess how the 2018 and 1999 classifications of periodontal diseases reflect (a) patients' characteristics, (b) disease severity/extent/progression and (c) tooth loss (TL) during observation period. Methods A total of 251 patients were followed over 21.8 +/- 6.2 years. For the 1999 classification, using clinical attachment level (CAL), patients were classified as localized/generalized, mild/moderate/severe and aggressive/chronic periodontitis. For the 2018 classification, patients were staged according to their CAL or bone loss (BL) and the number of lost teeth (stages I-IV). Further factors like probing pocket depths (PPD) or furcation involvement modified the stage. The extent was sub-classified as generalized/localized. Patients were graded according to the BL/age index, smoking and/or diabetes. Results According to the 1999 classification, most patients suffered from generalized severe chronic periodontitis (203/251) or generalized aggressive periodontitis (45/251). Patients with aggressive periodontitis were younger and less often female or smokers. They showed similar TL (0.25 +/- 0.22 teeth/patient*year) as generalized severe chronic periodontitis patients (0.23 +/- 0.25 teeth/patient*year). According to the 2018 classification, most patients were classified as generalized III-C (140/251), III-B (31/251) or IV-C (64/251). Patients' age, smoking status, CAL, PPD and BL were well reflected. TL differed between IV-C (0.36 +/- 0.47), generalized III-C (0.21 +/- 0.24) and localized forms (0.10-0.15). Conclusions Patients' characteristics, disease severity/extent/progression and TL were well reflected by the 2018 classification.