The aim of this study is to compare the effects of two different working length determination methods on the incidence of postoperative pain in single-rooted, single-canal teeth undergoing root canal retreatment (RCR). Sixty-four previously treated, single-rooted, single-canal teeth, which were determined to require RCR based on clinical symptoms and radiographic findings, were randomly and equally divided into two groups and included in the study. Two distinct working mechanisms of an integrated endodontic motor with an apex locator were used in our study. One method involved simultaneous determination of the working length during canal shaping, while the other method determined the working length with a hand file after the canal filling was removed. After the session in which the methods were applied and the working length was determined, participants' pain levels were recorded using a visual analog scale (VAS) at 6-12 hours and on days 1-2-3-4-5-6-7.

Inclusion Criteria:

Healthy volunteers aged between 18 and 65 with no systemic diseases. Teeth without acute apical abscess. Single-rooted and single-canal teeth that have previously undergone root canal treatment, failed, and require re-treatment (diagnosed based on clinical symptoms and radiographic findings).

Individuals with preoperative pain rated 50 or lower on the 100 mm VAS scale

Exclusion Criteria:

Individuals with systemic diseases or allergic reactions. Pregnancy and breastfeeding. Teeth with open apex. Teeth with internal or external root resorption. Patients who have taken analgesic, anti-inflammatory, or antibiotic medications within the last twelve hours.

Teeth with broken instruments in the canal. Individuals with bruxism problems.