ObjectivesThe aims of the present longitudinal retrospective observational case series study were to investigate the survival and success rates of primary non-surgical endodontic therapy.Materials and methodsPatients with at least one endodontically treated tooth (ETT), with 5 years of follow-up and in compliance with the recall programme of at least 1 time per year in a private practice setting, were recruited. Kaplan-Meier survival analyses were performed considering (a) tooth extraction/survival and (b) endodontic success as the outcome variables. A regression analysis was performed to evaluate prognostic factors associated with tooth survival.ResultsThree hundred twelve patients and 598 teeth were included. The cumulative survival rates showed 97%, 81%, 76% and 68% after 10, 20, 30 and 37 years, respectively. The corresponding values for endodontic success were 93%, 85%, 81% and 81%, respectively.ConclusionsThe study demonstrated high longevity in symptomless function as well as high success rates of ETT. The most significant prognostic factors associated with tooth extraction were the presence of deep (>6 mm) periodontal pockets, the presence of pre-operative apical radiolucency and the lack of occlusal protection (no use of a night guard).Clinical relevanceThe favourable long-term (> 30 years) prognosis of ETT must encourage clinicians to rely on primary root canal treatment when taking the decision regarding whether a tooth with pulpal and/or periapical diseases should be saved or be extracted and replaced with an implant.