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dependence of the results of pulp therapy on certain factors,’’1 a plethora of clinical follow-up studies has the influence of patient-related, tooth-related, and treatment-related factors on endodontic outcome in a ARTICLE IN PRESSdealt with influencing factors on endodontic treatment outcome.2 The aim of endodontic therapy is to prevent or treat periapical inflammatory lesions. These are host reactions to microbial challenges from the root canal system.3 It has been convincingly demonstrated that a maximal reduction of microbiota in the root canal system, followed by a tight seal, are key factors to endodontic treatment success.4 On the other hand, with few exceptions,1,5 host factors other than patient age and gender have been largely neglected in clinical in-vestigations. series of consecutive patients, and weigh these variables against each other using logistic regression analysis. PATIENTS AND METHODS Cohort identification Subjects included in this study were patients seeking treatment at the dental service of the Policlinique Medicale Universitaire in Lausanne. During her part-time employment as a comprehensive dental care provider at the hospital, one of the authors (M.M.) completed 132 orthograde root canal treatments (RCT