AimThis study assessed the long-term costs per retention year for periodontally affected molars. MethodsA cohort of 379 compliant subjects was retrospectively evaluated. Periodontal, restorative, endodontic, prosthetic and surgical treatment costs were estimated based on fee items of the private German health insurance. Costs/year were calculated and the impact of tooth- and subject-related factors on this cost-effectiveness ratio assessed using generalized linear-mixed modelling. Results2306molars received non-regenerative initial and supportive therapy and were followed until extraction or censoring (in mean (SD): 16.5 [6.8] years). Per year, 0.07 (SD: 0.12) deep scalings, 0.04 (0.11) open flap debridements, 0.01 (0.04) resective therapies and 2.49 (0.12) SPTs had been provided. Few teeth received non-periodontal treatments. Costs/year decreased significantly with each tooth a patient had at baseline (mean difference: -0.01, 95%CI: -0.02/-0.01Euro/year), and increased with each mm of probing-pocket depth (0.04 [0.03/0.06]Euro/year), in upper (0.07 [0.11/0.31]Euro/year) or mobile molars (up to 0.33 [0.18/0.48]Euro/year), those with bone loss (up to 0.11 [0.04/0.17] Euro/year), endodontic treatment (0.24 [0.15/0.33] Euro/year), peri-apical lesions (0.24 [0.11/0.38]) and prosthetic treatment (0.54 [0.49/0.59] Euro/year). ConclusionsAnnual costs for retaining periodontally affected molars were limited, and associated mainly with tooth-level factors.