AbstractBackgroundPain from temporomandibular disorders (TMDs) may mimic endodontic pain, but its prevalence in endodontic patients is unknown.ObjectivesThis cross‐sectional study investigated the prevalence of painful TMDs in patients presenting for endodontic treatment of a painful tooth. Contribution of TMD pain to the chief complaint and characteristics associated with TMD prevalence were also assessed.MethodsPatients reporting tooth pain in the 30 days before attending university clinics for nonsurgical root canal treatment or retreatment were enrolled. Before endodontic treatment, they completed questionnaires and a board‐certified orofacial pain specialist/endodontic resident diagnosed TMD using published Diagnostic Criteria for TMD. Log‐binomial regression models estimated prevalence ratios to quantify associations with patient characteristics.ResultsAmong 100 patients enrolled, prevalence of painful TMDs was 54%. In 26% of patients, TMD pain was unrelated to endodontic pain; in 20%, TMD contributed to their chief pain complaint; and in 8%, TMD was a sole aetiology for pain. TMD prevalence was associated with greater intensity, frequency and duration of the chief pain complaint; pain in more than one tooth; tenderness to tooth percussion and palpation; a diagnosis of symptomatic apical periodontitis; pain medication use; and psychological distress.ConclusionA majority of patients with tooth pain seeking endodontic treatment had painful TMDs; one quarter had TMD as a component or sole cause of their pain. TMD prevalence was associated with more severe symptoms and signs of tooth pain and with psychological factors. The high frequency of TMD comorbidity warrants consideration in management of endodontic patients with history of toothache.