Objective: Evaluation of tooth-related factors influencing long-term success of systematic periodontal therapy. Main outcome variable for this analysis was tooth loss. Methods: 38 patients were consecutively recruited. Inclusion criteria were antiinfectious therapy 10 years ago by the same therapist (PE) and a complete set of intraoral radiographs obtained at the initiation of therapy. Clinical examinations, sampling for interleukin-1 polymorphism test, and questionnaire regarding smoking, and oral hygiene, were performed by the same examiner (BP). Tooth loss, type, and location as well as frequency of supportive periodontal therapy (SPT) were recorded from patients' charts. Each tooth was evaluated for bone loss in per cent of root length and type of bone loss (vertical/horizontal) on the radiographs by another examiner (JK). Results: From a total of 847 teeth 70 teeth were lost in a period of 10 years (8%). Initially 256 teeth exhibited a bone loss up to 20% (tooth loss 4%), 302 up to 40% (5%), 192 up to 60% (11%), 69 up to 80% (19%), and 28 > 80% (36%). Under frequent SPT (21 patients, 479 teeth) tooth loss amounted to 4%, without SPT to 13%. Multilevel regression analysis identified the following factors as preventive against tooth loss: frequent SPT (p = 0.021), little bone loss (p Conclusion: Little initial bone loss, mandibular as well as anterior tooth location, and frequent SPT are positive predictors for tooth retention. Schlagwörter: Langzeitergebnisse, antiinfektiöse Therapie, unterstützende Parodontitistherapie, parodontaler Knochenabbau, Zahntyp