OBJECTIVE The aim of this retrospective study was to determine factors influencing tooth loss during a long-term follow-up, emphasizing the impact of various compliance definitions. METHODS Patients with periodontitis who were treated and presenting for maintenance care for at least up to 6 years were included. The effects of compliance and other patient- and treatment-related factors on tooth loss were assessed. Lack of compliance was defined in three ways: (1) fewer than 1.4 visits per year (irregular compliers), (2) no maintenance visit over a 2-year period (erratic compliers), and (3) no maintenance visit over a 2- to 5-year period (partial compliers) and no maintenance visit for a period of more than 5 years (non-compliers). RESULTS One hundred and one patients were selected. The mean follow-up was 9.72 ± 1.17 years. Tooth loss per patient-year was significantly higher in erratic compliers (0.35 ± 0.19) and non-compliers (0.40 ± 0.20) compared with compliers (0.18 ± 0.10). No significant differences were found for irregular (0.30 ± 0.17) and partial (0.25 ± 0.15) compliers. Similar results were obtained for the number of patients who lost more than three teeth. Multivariable regression analysis showed that lack of compliance and periodontitis severity (more than 3% of periodontal pockets > 7 mm at baseline) were independent risk factors for tooth loss. CONCLUSIONS During long-term follow-up, non-compliance and initial periodontitis severity were the principal risk factors that increased tooth loss. CONCLUSIONS Tooth loss associated with lack of compliance was essentially observed in patients with long continuous periods without maintenance visits and was less influenced by patients' attended mean visit frequency.