Aim: To identify risk factors for loss of molars during supportive periodontal therapy (SPT). Materials and Methods: A total of 136 subjects with 1015 molars at baseline were examined retrospectively. The association of risk factors with loss of molars was assessed using a multilevel Cox regression analysis. Furcation involvement (FI) was assessed clinically at start of periodontal therapy and assigned according to Hamp et al. (1975).
Results: Fifty molars were extracted during active periodontal therapy (APT) and 154 molars over the average SPT period of 13.2 T 2.8 years. FI degree III (HR 4.68, p < 0.001), baseline bone loss (BL) > 60% (HR 3.74, p = 0.009), residual mean probing pocket depth (PPD, HR 1.43,  p  = 0.027), and  endodontic treat- ment (HR 2.98, p  < 0.001) were identified as relevant tooth-related factors for    loss of molars during SPT. However, mean survival time for molars with FI III      or BL > 60% were 11.8 and 14.4 years, respectively. Among the patient data, age (HR 1.57, p = 0.01), female gender (HR 1.99, p = 0.035), smoking (HR 1.97, p = 0.034), and diabetes mellitus (HR 5.25, p = 0.021) were significant predictors for loss of molars.
Conclusion: Overall, periodontal therapy results in a good prognosis of molars. Degree III FI, progressive BL, endodontic treatment, residual PPD, age, female gender, smoking, and diabetes mellitus strongly influence the prognosis for molars after APT.