Effect of Rotary File Number on MB2 Canal Negotiation and Postoperative Pain

This randomized controlled clinical trial aims to evaluate the effect of the number of rotary files on working length negotiation and postoperative pain in the second mesiobuccal (MB2) canals of maxillary first molars. Patients are assigned to one of four groups according to the number of rotary files used: single-, two-, three-, or four-file systems. Postoperative pain is assessed on each of the seven consecutive postoperative days (Days 1-7) using a visual analog scale (VAS), and working length negotiation success is recorded during canal instrumentation.

Inclusion Criteria: * Systemically healthy individuals aged between 20 and 65 years * Requiring primary endodontic treatment of maxillary first molars * Diagnosis of asymptomatic apical periodontitis based on clinical and radiographic findings * Presence of a second mesiobuccal (MB2) canal in the maxillary first molar * Absence of preoperative pain or symptoms * Teeth with periapical lesions smaller than 5 mm in diameter * Ability to comply with follow-up visits and effectively communicate during the treatment process Exclusion Criteria: * Presence of symptomatic apical periodontitis or acute apical abscess * Need for retreatment of previously treated teeth * Use of medications such as narcotics, antibiotics, sedatives, or antidepressants within one week prior to treatment * Presence of a sinus tract, periapical abscess, or facial cellulitis * Pregnancy * Inability to understand or follow the study instructions